Mahesh

Andhra Pradesh BIEAP AP Inter 1st Year Zoology Study Material Lesson 5 Locomotion and Reproduction in Protozoa Textbook Questions and Answers.

AP Inter 1st Year Zoology Study Material Lesson 5 Locomotion and Reproduction in Protozoa

Very Short Answer Type Questions

Question 1.
Draw a labeled diagram of the T.S of the flagellum.
Answer:

Question 2.
List any two differences between a flagellum and a cilium.
Answer:

Question 3.
What are dynein arms? What is their significance?
Answer:
‘A’ tube of each peripheral doublet bears paired arms along its length called dynein arms made up of protein dynein.
The dynein arms of the ‘A’ tubule face the tubule ‘B’ of the adjacent doublet.

Question 4.
What is a kinety?
Answer:
In the ciliate protozoans, a longitudinal row of kinetosomes together with kinetodesmata constitute a unit called kinety.

Question 5.
Distinguish between synchronous and metachronous movements.
Answer:
Synchronous movement: Cilia in a transverse row beat simultaneously in one direction. It is called synchronous movement.
Metachronous movement: The sequential movement of cilia, in a longitudinal row, one after the other in one direction is called metachronous movement.

Question 6.
Why do we refer to the offspring, formed by the asexual method of reproduction, as a clone?
Answer:
As a result of the asexual method, the offsprings are, not only identical to one another but also exact copies of their parent. The term ‘clone’ is used to describe such morphologically and genetically similar individuals.

Question 7.
Distinguish between proter and opisthe.
Answer:
During transverse binary fission in Paramecium two daughters, individuals are formed. The anterior one is called proter and the posterior is called opisthe.

Question 8.
How is sexual reproduction advantageous in evolution?
Answer:
Sexual reproduction results the advantageous in evolution in genetic recombination occurs in sexual reproduction.

Question 9.
Distinguish between lobopodium and filopodium. Give an example to each of them.
Answer:
Lobopodium: The blunt and finger-like tubular pseudopodia containing both ectoplasm and endoplasm is called lobopodium.
Ex: Amoeba proteus
Filopodium: The slender filamentous pseudopodia with pointed tips, composed of only ectoplasm are called Filopodium.
Ex: Euglypha

Question 10.
Define conjugation with reference to ciliates. Give two examples.
Answer:
Conjugation is a temporary union between two senile ciliates that belong to two different ‘mating types’ for the exchange of nuclear material and its reorganization. – Wichterman.
Ex: Paramecium and Vorticella.

Short Answer Type Questions

Question 1.
Name the system that controls the fastest swimming movement of protozoans and write its components.
Answer:
Ciliary locomotion is the fastest swimming movement of protozoans, Hence, ciliates are the fastest protozoans.
Cilia are small hair-like structures found in ciliate protozoans like Paramecium.

Infraciliary system: It is located just below the pellicle in the ectoplasm of a ciliate. It includes kinetosomes, kinetodesmal fibrils, and kinetodesmata. The kinetosomes are present at the bases of cilia in transverse and longitudinal rows. The kinetodesmal fibrils are connected to the kinetosomes and run along the right side of each row of kinetosomes as a ‘cord of fibres’ called kinetodesmata. A longitudinal row of kinetosomes together with kinetodesmata constitute a unit called ‘kinety’.

All the kineties together form an infraciliary system, which is connected to a ‘motorium’, located near the cytopharynx. The infraciliary system and motorium form the ‘neuromotor system’ that controls and coordinates the movement of cilia.

Question 2.
Write the mechanism of bending the flagellum and explain effectively recovery strokes.
Answer:
The bending movement of a flagellum is brought about by the sliding of microtubules past each other due to the functioning of ‘dynein arms’ utilizing ATP. A flagellum pushes the fluid medium at right angles to the surface of its attachment, by its bending movement.

Bending movement of flagella and cilia: Dynein arms show a complex cycle of movements using energy provided by ATP (dynein arms are the sites of ATPase activity in the cilia and flagella). The dynein arms of each doublet attach to an adjacent doublet and pull the neighbouring doublet. So the doublets slide past each other in opposite directions. The arms release and reattach a little further on the adjacent doublet and again ‘puli’. As the doublets of a flagellum or cilium are physically held in place by the radial spokes, the doublets cannot slide past much. Instead, they curve and cause the bending of flagellum or cilium. Such bending movements of flagella and cilia play an important role in flagellar and ciliary locomotion.

The flagellar movement of many organisms is a sidewise-lash which consists of two strokes namely the effective or propulsive stroke and the recovery stroke.

• Effective stroke: Flagellum becomes rigid and starts bending to one side beating against the water. This beating against water is at right angles to the body axis and the organism moves forwards.
• Recovery stroke: Flagellum becomes comparatively soft so as to offer the least resistance to water and moves back to its original position. It is called ‘recovery stroke’.

Question 3.
What are lateral appendages? Based on their presence and absence, write the various types of flagella giving atleast one example for each type.
Answer:
Lateral appendages: Some flagella bear one or two or many rows of short, lateral hair-like fibrils called lateral appendages. They are of two types namely ‘mastigonemes’ and ‘flimmers’.
Types of Flagella: Based on the presence or absence and/or the number of rows of lateral appendages, five types of flagella are recognized.
(a) Stichonematic: This flagellum bears one row of lateral appendages on the axoneme.
E.g. Euglena and Astasia.
(b) Pantonematic: This flagellum has two or more rows of lateral appendages on the axoneme.
E.g. Peranema and Monas.
(c) Acronematic: This type of flagellum does not bear lateral appendages and the terminal part of the axoneme is naked without the outer sheath at its tip.
E.g. Chlamydomonas and Polytoma

(d) Pantacronematic: This type of flagellum is provided with two or more rows of lateral appendages and the axoneme ends in a terminal naked filament.
E.g. Urceolus.
(e) Anematic or simple: In this type of flagellum, lateral appendages and terminal filament are absent. Hence, it is called anematic (a-no; nematic-threads)
E.g. Chilomonas and Gryptomonas.

Question 4.
Describe the process of transverse binary fission in paramecium.
Answer:
Transverse binary fission is performed by Paramecium. Binary fission is the most common method of sexual reproduction in protozoans. During favourable conditions, Paramecium stops feeding after attaining its maximum growth.

At first, the micronucleus divides by mitosis and the macronucleus divides into two daughter nuclei by amitosis. The oral groove disappears. After karyokinesis, a transverse constriction appears in the middle of the body, which deepens and divides the parent cell into two daughter individuals, the anterior proper and the posterior opisthe. The proper receives the anterior contractile vacuole, cytopharynx, and cytosome from its parent individual. It develops a posterior contractile vacuole and a new oral groove.

The opisthe receives the posterior contractile vacuole of its parent. It develops a new anterior contractile vacuole, cytopharynx, cytostome and a new oral groove. Binary fission is completed in almost two hours, in favourable conditions and Paramecium can produce four generations of daughter individuals by binary fission in a day. The transverse binary fission is also called homothetogenic fission because the plane of fission is at right angles to the longitudinal axis of the body. As it occurs at right angles to the kineties, it is also called perkinetal fission.

Question 5.
Describe the process of longitudinal binary fission in Euglena.
Answer:
Binary fission is the most common method of asexual reproduction in protozoans. Longitudinal binary fission is performed by Euglena. In this type of binary fission, the body divides into two halves longitudinally, hence called longitudinal binary fission.

During the process of binary fission, the nucleus, basal granules, chromatophores, and cytoplasm undergo division. The nucleus divides by mitosis into two daughter nuclei. Then the kinetosomes and the chromatophores also divide. At first, a longitudinal groove develops in the middle of the anterior end. This groove extends gradually towards the posterior end until the two daughter individuals are separated. One daughter Euglena retains the parental flagella. The other daughter individual develops new flagella from the newly formed basal granules. The stigma, paraflagellar body, and contractile vacuole of the parent disappear. They develop afresh in both the daughter Euglenae. The longitudinal binary fission is known as symmetrogenic division because the two daughters Euglenae resemble each other like mirror images.

Question 6.
Write a short note on multiple fission.
Answer:
Multiple fission: It is the division Of the parent body into many smaller individuals (Multi-many; Fission- splitting). Normally multiple fission occurs during unfavourable conditions. During multiple fission, the nucleus first undergoes repeated mitotic divisions without cytokinesis. This causes the formation of many daughter nuclei. Then the cytoplasm also divides into as many bits as there are nuclei. Each cytoplasmic bit encircles one daughter nucleus. This results in the formation of many smaller individuals from a single-parent organism. There are different types of multiple fissions in protozoans such as Schizogony, malegametogony, sporogony in plasmodium, sporulation in Amoeba, etc.

Question 7.
Give an account of pseudopodia.
Answer:
Locomotion in protozoans is performed by cellular extensions such as pseudopodia found in rhizopods organisms. The pseudopodia are temporary extensions of cytoplasm that develop in the direction of the movement. These temporary structures are useful to move on the substratum as our legs do, hence the name ‘pseudopodia’. There are four kinds of pseudopodia in protozoans.

1. Lobopodia: blunt + finger like Pseudopodia. Ex: Amoeba, Entamoeba.
2. Filopodia: fiber like pseudopodia contain ectoplasm. Ex: Euglypha.
3. Reticulopodia: net like pseudopodia. Ex: Elphidium.
4. Axopodia or heliopodia: Sun ray-like pseudopodia. Ex: Actinophiys.

Question 8.
Give an account of the ultrastructure of an axoneme.
Answer:
Ultrastructure of flagellum: The axial filament or axoneme shows 9+2 organisation under the electron microscope. Two central singlets are enclosed by a fibrous inner sheath. Nine peripheral doublets form a cylinder between the inner sheath and the outer sheath. The “A” microtubule of each doublet is connected to the inner sheath by radial spokes. It also has pairs of arms all along the length and is directed towards the neighbouring doublet.

These arms are made of a protein called dynein. These arms create the sliding force. The peripheral doublets are surrounded by an outer membranous sheath called a protoplasmic sheath, which is the extension of the plasma membrane. Some flagella bear lateral appendages called flimmers or mastigonemes along the length of the axoneme above the level of the pellicle. Each flagellum arises from a basal granule that lies below the cell surface in the ectoplasm.

Question 9.
Draw a neat labelled diagram of Euglena.
Answer:

Question 10.
Draw a neat diagram of paramecium and label its important structures/components.
Answer:

Andhra Pradesh BIEAP AP Inter 1st Year Zoology Study Material Lesson 4 Animal Diversity-II: Phylum Chordata Textbook Questions and Answers.

AP Inter 1st Year Zoology Study Material Lesson 4 Animal Diversity-II: Phylum Chordata

Very Short Answer Type Questions

Question 1.
List out the characters shared by chordates and echinoderms.
Answer:
Chordates and echinoderms are enterococci, deuterostomes, and bilaterally symmetrical.

Question 2.
Write four salient features of cyclostomes.
Answer:

1. Cyclostomes are jawless aquatic forms.
2. The body is scaleless, long, slender, and eel-like in shape.
3. Endoskeleton is cartilaginous.
4. Vertebrae are represented by imperfect neural arches in some.
5. The mouth is circular and suctorial, Hence there are called Cyclostomes. Ex: Petromyzon.

Question 3.
What is the importance of endostyle in lancelets and ascidians?
Answer:
Endostyle is useful for accumulating and moving food particles to the oesophagus in lancelets and ascidians.

Question 4.
Name the type of caudal fin and scales that are present in a Shark and Catla respectively.
Answer:
The caudalfin in shark is heterocercal and scales are placoid. The caudal fin is catla is homocercal and scales are cycloid.

Question 5.
What is the importance of air bladder in fish?
Answer:
Fishes have an ‘air bladder’ acting as a ‘hydrostatic organ’ helping the fish float easily at the desired level without much expenditure of energy.

Question 6.
How do you justify the statement ‘heart in fishes is a branchial heart’?
Answer:
The heart of fish is two-chambered and is described as a branchial heart as it supplies blood only to the gills.

Question 7.
What are claspers? Which group of fishes possesses them?
Answer:
Claspers are formed from the posterior portion of pelvic fins in male cartilaginous fish. They serve as intermittent organs used to channel semen into the female’s cloaca during mating.
Ex: Chondrichthyes fishes possess Claspers.

Question 8.
How does the heart of an amphibian differ from that of a reptile?
Answer:
The heart of an amphibian is three-chambered. The heart of a reptile is incompletely four-chambered.

Question 9.
Name the structures that appeared for the first time in amphibians, in the course of evolution.
Answer:
The two pairs of pentadactyl limbs appeared for the first time in amphibians in the course of evolution.

Question 10.
How do you distinguish a male frog from a female frog?
Answer:
The male frog can be distinguished by the presence of sound amplifying vocal sacs and a copulatory pad on the first digit of each forelimb.

Question 11.
What is a ‘force pump’ in a frog? Why is named so?
Answer:
In frogs, during pulmonary respiration, the buccopharyngeal cavity acts like a ‘force pump’. Due to the elevation of the buccopharyngeal cavity the air forces the glottis to open and enter the lungs.

Question 12.
What are corporabigemina? Mention their chief function.
Answer:
Midbrain is represented by a pair of optic lobes called corpora bigemina. The optic lobes are associated with the sense of sight.

Question 13.
Distinguish between mesorchium and mesovarium.
Answer:
The testes are attached to the kidneys and dorsal body wall by a double fold of the peritoneum called mesorchium.
The ovaries are attached to the kidneys and dorsal body wall by a double fold of the peritoneum called mesovarium.

Question 14.
Distinguish between milt and spawn.
Answer:
During amplexus, the mass of eggs and the mass of sperm released by the female and male are called spawn and milt.

Question 15.
What are the ‘Golden ages’ of the first jawed vertebrates and the first amniotes?
Answer:
The Devonian period is considered the ‘golden age of first jawed vertebrates (Fishes).
The Mesozoic era is considered the golden age of amniotes (Reptiles).

Question 16.
Name two poisonous and non-poisonous snakes found in south India.
Answer:
Poisonous Snakes:

1. Naja naja (Cobra)
2. Bungarus (Krait)
3. Vipera russelli (Chain viper)

Non-poisonous Snakes:

1. Ptyas (rat snake)
2. Tropidonotus (Pond or grass snake).

Question 17.
In which features does the skin of a reptile differ from that of a frog?
Answer:

• The skin of reptiles is rough and dry, covered by horny epidermal scales, and shields.
• The skin of a frog is thin, scaleless, and moist.

Question 18.
Describe a cat and a lizard on the basis of their chief nitrogenous wastes excreted.
Answer:
Based on the nitrogenous wastes excreated by lizards are Uricotelic and cats are ‘Ureotelic’ animals.

Question 19.
Name the four extraembryonic membranes.
Answer:
The extraembryonic membranes namely amnion, allantois, chorion, and yolk sac.

Question 20.
What are Jacobson’s organs? What is their function?
Answer:
Jacobson’s organs are the specialized olfactory structures, that are highly developed in lizards and snakes.

Question 21.
What are pneumatic bones? How do they help birds?
Answer:
The main bones in birds are extensions of air sacs without bone marrow are called pneumatic bones. These are helpful in flying birds.

Question 22.
What is a ‘wishbone? What are the skeletal components that form it?
Answer:
In birds, both the clavicles are fused with the interclavicular to form a ‘V-shaped bone, called fiircula or ‘wish hone’ or ‘Merrythought bone’.

Question 23.
What is continuous oxygenation of the blood? How is it made possible in birds?
Answer:
The lungs of birds are compact, spongy, undistensible lungs associated with air sacs. Air sacs facilitate continuous air supply is called ‘continuous oxygenation of the blood.

Question 24.
Distinguish between the crop and the gizzard in birds.
Answer:

• The Oesophagus of birds is often dilated into a crop for the storage of food.
• The stomach is usually divided into glandular proventriculus and muscular gizzard a grinding mill.

Question 25.
Distinguish between altricial and precocial hatchlings.
Answer:

• Altricial: Young ones of flying birds’ hatchlings are altricial.
• Precocial: Young ones of flightless bird hatchlings are precocial.

Question 26.
In which group of animals do we find three ear ossicles on each side and what are their names from the innermost to the outermost?
Answer:
The middle ear possesses three ear ossicles in the Mammalia group of animals. They are malleus, incus and stapes.

Question 27.
How does a mature RBC of a mammal differ from that of other vertebrates?
Answer:

• In mammals, mature RBC is enucleated and biconcave.
• In other vertebrates RBC is nucleate.

Question 28.
Name the characteristic type of vertebrae found in reptiles, birds, and mammals.
Answer:

• Reptiles’ vertebrae are procoelons.
• Birds’ vertebrae are heterologous.
• Mammalian vertebrae are amphiplatyan.

Question 29.
Name the three meninges. In which group of animals do you find all of them?
Answer:
Mammals have three meninges. They are the outer dura mater, middle arachnoid mater, and inner diameter.

Question 30.
Name the vertebrate groups in which ‘renal portal system1 is absent.
Answer:
The renal portal system is absent in aves (birds) in vertebrate animals.

Short Answer Type Questions

Question 1.
Give three major differences between chordates and non-chordates and draw a sketch of a chordate’s body showing those features.
Answer:
The major differences between chordates and non-chordates.

Question 2.
Name the four ‘hallmarks’ of chordates and explain the principal function of each of them.
Answer:
The hallmarks of chordates: All the chordates exhibit four fundamental characteristics. They are Notochord, Dorsal tubular nerve cord, Pharyngeal slits or clefts, and Post-anal tail.

Notochord: It is a flexible rod-like structure situated along the mid-dorsal line between the gut and the nerve cord. It is derived from the embryonic chorda mesoderm. It is firm but flexible. It is present throughout life in the lancelets and cyclostomes. It is present in the tail of the tadpole larva of an ascidian, It is present in embryonic stages, but is replaced partly or wholly by the vertebral column in the adults of higher chordates. Remnants of notochord occur as nucleipulposi in the intervertebral discs of mammals.

Dorsal tubular nerve cord: A single, hollow tubular, and fluid-filled nerve cord is situated above the notochord and below the dorsal body wall. It is derived from the ectoderm of the embryo. In the higher chordates, it gets enlarged to form a distinct brain at the anterior end the rest of it becomes the spinal cord.

Pharyngeal slits of clefts: These are slit openings present on the Pharyngeal wall and meant for the exit of the water from the pharyngeal cavity. They are present throughout life in the protochordate, fishes, and some amphibians. These are present in larval stages in amphibians. They develop by in-pushing of ectoderm and corresponding out pursing of the endoderm. In land vertebrates, the gills become vestigial and nonfunctional and are restricted to embryonic stages only.

Post-anal tail: Chordates have a tail extending posteriorly to the anus. It is lost in many species during late embryonic development. It contains skeletal elements and muscles, coelom and visceral organs are absent in it.

Question 3.
Describe the features of a tunicate that reveals its chordate identity.
Answer:

1. The body of these animals is covered by cellulose-like covering tunicin, hence called tunicates.
2. These possess Notochord in the tail region during the larval stage, hence called Urochordata.
3. These are sedentary or pelagic marine forms.
4. The notochord is present only in larval tails and degenerated in adults.
5. Open type of blood vascular system with blood pigment vanadium.
6. Indirect development with tadpole larva.
7. Adults (mostly) show degenerate characters.
8. The nervous system is represented in the adult by a single dorsal ganglion.
9. They are bisexual or hermaphrodites.
10. Ex: Ascidia, Salpa, Doliolum, Pyrosoma and Oikopleura.

Question 4.
Compare and contrast sea squirts and lancelets.
Answer:
Sea squirts: These are included in class – Ascadiaceae of subphylum – Urochordata. These are sessile. These are solitary or colonial. The body is enclosed in a permanent test and un-segmented. All these are marine and occur from the surface water to greater depths. Coelom in the absent, pharynx is large and is perforated by numerous gill slits. Branchial aperture in anterior and atrial aperture is dorsal. The digestive tract is ‘complete’. The circulations system is of an open type, the heart is the tubular and the ventral heart. These are bisexual. Development generally includes a free-swimming tadpole larva. Notochordcontinued to the tail hence the name Urochordata.
Ex: Ascidia

Lancelets: Cephalochordates are also called Lancelets. These are marine animals and are small fish without paired fins. These are typical chordates because they possess the notochord, tubular nerve cord, and pharyngeal slits throughout this life. The coelom is enterocoelic respiration mostly across the external body surface. The circulatory system is of a closed type, the heart, blood corpuscles, and respiratory pigments are absent. Excretion by protonephridia fertilization is external and development is indirect.
Ex: Branchiostoma (amphioxus or Lancelet)

Question 5.
List out eight characteristics that help distinguish a fish from the other vertebrates.
Answer:
General characters:

1. Fishes are completely aquatic poikilothermic (cold-blooded) animals.
2. The body of a fish is usually streamlined and differentiated into the head, trunk, and tail.
3. The exoskeleton consists of mesodermal scales or bony plates. A few are scaleless.
4. The endoskeleton may be cartilaginous or bony. Skull is monocondylic. Vertebrae are amphicoelous. Centrum is concave at both anterior and posterior faces.
5. Locomotion is assisted by unpaired (median and caudal) fins along with paired (pectoral and pelvic) fins.
6. The mouth is ventral or terminal. Teeth are usually acrodont, homodont, and polyphyodont.
7. The exchange of respiratory gases is performed by the gills. The heart is ‘two-chambered’.
8. Kidneys are mesonephric. Fishes are mostly ammonotelic and some are ureotelic. (cartilaginous fishes).
9. Cranial nerves are 10 pairs, Meninx Primitiva is the only ‘meninx’ enveloping the central nervous system.
10. The internal ear consists of three semicircular canals. Lateral-line sensory system (to detect movement and vibration in the surrounding water) is well-developed.
11. Eyes are without eyelids and each eyeball is protected by a nictitating membrane.
12. Sexes are separate. Fertilization is internal or external. Development may be direct or indirect.

Question 6.
Compare and contrast cartilaginous and bony fishes.
Answer:

Question 7.
Describe the structure of the heart of the frog.
Answer:
The blood vascular system consists of the heart, blood vessels, and blood. The heart is a muscular organ situated in the upper part of the body cavity. It has two separate atria and a single undivided ventricle. It is covered by a double-layered membrane called the pericardium. A triangular chamber called sinus venosus joins the right atrium on the dorsal side. It receives blood through three vena cavae (caval veins). The ventricle opens into the conus arteriosus on the ventral side. The conus arteriosus bifurcates into two branches and each of them divides into three aortic arches namely carotid, systemic and pulmocutaneous. Blood from the heart is distributed to all parts of the body by the branches of the aortic arches. Three major veins collect blood from the different parts of the body and carry it to the sinus venosus.

Question 8.
Write eight salient features of the class – Amphibia.
Answer:
General characters of Amphibia:

1. They are the first tetrapods and lead a dual mode of life, i.e. on land and in freshwater.
2. The body is divided into distinct ‘head’ and ‘trunk’. The tail may or may not be present.
3. Skin is soft, scale-less (except for the members of Apoda), moist and glandular.
4. The body bears two pairs of equal or unequal pentadactyle limbs (caecilians are limbless).
5. Skull is dicondylic as in mammals. Vertebrae are mostly precocious (centrum is concave at its anterior face only) in the anurans, amphicoelous in the caecilians, and usually opisthocoelous (centrum is concave at its posterior face) in the urodeles. Sternum appeared for the first time in the amphibians.
6. The mouth is large; teeth are acrodont, homodont, and polyphyodont.
7. Respiratory gaseous exchange is mostly cutaneous; pulmonary and buccopharyngeal respiration also occurs. Branchial respiration is performed by larvae and some adult urodeles.
8. The heart is three-chambered with sinus venosus and conus arteriosus. Three pairs of aortic arches and well-developed portal systems are present; erythrocytes are nucleated.
9. Kidneys are mesonephric; ureotelic.
10. Meninges are the inner pia mater and outer dura mater; cranial nerves are 10 pairs.
11. The middle ear consists of a single ear ossicle, the columella Auris which is the modified ‘hyomandibula’ of the fishes.
12. Tympanum, lacrimal and harderian glands appeared for the first time in the amphibians.
13. Sexes are separate and fertilization is mostly external. Development is mostly indirect.
14. e.g. Bufo (toad), Rana (frog), Hyla (tree frog), Salamandra (salamander), Ichthyophis (limbless amphibian), Rhacophorus (flying frog).

Question 9.
Describe the male reproductive system of a frog with the help of a labelled diagram.
Answer:
Male Reproductive System of frog: The male reproductive system consists of a pair of yellowish and ovoid testes, which are attached to the kidneys and dorsal body wall by a double fold of peritoneum called mesorchium. Each testis is composed of innumerable seminiferous tubules which are connected to form 10 to 12 narrow tubules, the vasa efferentia. They enter the kidneys and open into the Bidders canal which is connected to the ureter through transverse canals of the kidney. The urinogenital ducts of both sides open into the cloaca.

Question 10.
Write short notes on organs of special senses in frogs.
Answer:
Special senses: Frog has sense organs such as the organs of touch, taste, smell, sight, and hearing. The well-organized structures among them are eyes, and internal ears, and the rest are ‘cellular aggregations’ around nerve endings. The receptors of touch occur in the skin. Organs of taste are called taste buds that lie on small papillae of the tongue. The organs of smell are a pair of nasal chambers.

The organs of sight are a pair of eyes located in the orbits of the skull. Eyes are protected by eyelids. The upper eyelid is immovable. The lower eyelid is folded into a transparent nictitating membrane, which can be drawn across the surface of the eye. The retina of the eye contains both rods and cones. Cones provide ‘colour vision’ and rods are helpful in ‘dim light vision’.

The ear is useful for hearing and balance. It consists of a middle ear closed externally by a large tympanic membrane (ear drum) and a columella that transmits vibrations to the inner ear. The inner ear consists of a utriculus with three semicircular canals and a small sacculus.

Question 11.
List out the salient features of Exo and endoskeleton in reptiles.
Answer:
The exoskeleton of reptiles occurs in the form of horny epidermal scales, shields, and claws.
Endoskeleton:

1. Skull is monocondylic and many have temporal fossae.
2. Each half of the lower jaws is formed by six bones.
3. Vertebrae are mostly procoelous.
4. The first two cervical vertebrae are specialized into the atlas and axis.
5. The vertebral column is distinguished into cervical, thoracic, lumbar, sacral, and caudal regions.
6. Most living reptiles possess two sacral vertebrae.
7. Interclavicular is associated with the pectoral girdle.
8. Ribs are single-headed except in crocodilians.

Question 12.
List out the extant orders of the Class – Reptilia. Give two examples for each Order.
Answer:

1. Chelonia – Chelone (marine green turtle), Testudo (terrestrial form), Trionyx (freshwater form)
2. Rhynchocephalia – Sphenodon (a ‘living fossil’, endemic to New Zealand)
3. Crocodilia – Crocodylus pulustris (Indian crocodile or mugger), Alligator (alligator), Gavialis gangeticus (Indian gavial or gharial)
4. Squamata
   • Lizards – Hemidactylus (wall lizard), Chameleon, Draco (flying lizard)
   • Snakes
     • Poisonous Snakes: Naja naja (cobra), Ophiophagus hannah (King cobra), Bungarus (krait), Daboia/Vipera russelli (chain viper)
     • Non-Poisonous Snakes: Ptyas (rat snake), Tropidonotus (grass snake or pond snake)

Question 13.
What are the modifications that are observed in birds that help them in flight?
Answer:
So many modifications are observed in birds that help them in flight.

1. Exo and endo skeletons and body structure features might have contributed to their successful aerial mode of life.
2. The exoskeleton consists of epidermal feathers. Feathers are unique to birds. They are useful for flight, particularly the Quill feathers help in flight.
3. The body is boat-shaped and streamlined.
4. Four limbs are modified into wings.
5. Many bones are neumatic with extensions of air sacs.
6. All modern flying birds are provided with powerful breast muscles (flight muscles) chiefly the pectoralis major and pectoralis minor.
7. Lungs are associated with air and seas.

Question 14.
What are the features peculiar to ratite birds? Give two examples of ratite birds.
Answer:
Ratite birds:

1. These are modern flightless running birds.
2. They are ‘discontinuous’ in their distribution like the lungfishes and marsupials.
3. They are characterized by the presence of reduced wings.
4. Feathers are without an interlocking mechanism.
5. Rectrices are absent or irregularly arranged.
6. Prren gland is absent.
7. Pygostyle is rudimentary or absent.
8. The sternum is like without a keel.
9. Clavicles are absent, and syrinx is absent.
10. The male animal has a penis.
11. Young ones are precocial.
12. Ex: Struthio camelus – (African ostrich); Dromaeus (Emu) Kiwi.

Question 15.
Mention the most important features of the nervous system and sense organs in mammals.
Answer:

• The nervous system and sense organs are well developed in mammals.
• Mammals have relatively large brains when compared to that other animals in relation to body size.
• The four optic lobes constitute corpora quadrigemina.
• The two halves of the cerebrum are connected by the corpus callosum.
• The central nervous system is enveloped by three meninges.
• Eyes have movable eyelids with eyelashes.
• The external ear has a large pinna middle ear and possesses three ear ossicles.
• They are malleus, incus, and stapes, Cochlea of the internal ear is spirally coiled and bears the organ of Corti which is the receptor of sound.
• Skin is one of the sense organs.

Question 16.
Write short notes on the following features of the eutherians.

1. Dentition
2. Endoskeleton

Answer:

1. Dentition: The Dental formula of eutherians is i 3/3; c 1/1j pm 4/4, m 3/3; dentition is the codon, heterodont, diphyodont.
2. Endoskeleton: Skull is dycondylic. Most mammals have seven cervical vertebrae; vertebrae are of the amphiplatyan type, sacral vertebrae are two or five, and ribs are double-headed.

Question 17.
Give an example for each of the following.

1. A viviparous fish
2. A fish possessing electric organs
3. A fish possessing poison sting
4. An organ that regulates buoyancy in the body of a fish
5. An oviparous animal with milk-producing glands.

Answer:

1. Scoliodon fish is viviparous fish.
2. Torpedo fish is possessing electric organs.
3. Dasyatis/Trygon fish possess poison sting.
4. The air bladder regulates buoyancy in the body of a fish.
5. Ornithorhynchus anatinus (Duck-billed platypus) is an oviparous animal with milk-producing glands.

Question 18.
Mention two similarities between
(a) Aves and mammals
(b) A frog and a crocodile
(c) A lizard and a snake
Answer:
(a) Aves and mammals:

• Aves and mammals are Triploblaste and bilaterally symmetrical.
• The heart is four-chambered in both.

(b) A frog and a crocodile:

• Erythrocytes are nucleated in both.
• Frogs and crocodiles are uriotelic animals.

(c) A lizard and a snake:

• Lizards and snakes are reptilian animals.
• The heart is incompletely four-chambered.
• Jacobson’s organs, the highly developed specialized olfactory structures are present.

Question 19.
Name the following animals.

1. A limbless amphibian
2. The largest of all living animals
3. An animal possessing dry and cornified skin
4. ‘National animal’ of India.

Answer:

1. Ichthyophis is a limbless amphibian.
2. Balaenoptera musculus (Blue whale) is the largest of all living animals.
3. Crocodylus is an animal possessing dry and cornified skin.
4. Panther Tigris (tiger) is the National animal of India.

Question 20.
Write the generic names of the following.

1. An oviparous mammal
2. Flying fox
3. Blue whale
4. Kangaroo

Answer:

1. An oviparous mammal’s generic name is Ornithorhynchus (Duckbilled platypus).
2. Flying fox’s generic name is Pteropus.
3. The blue whale’s generic name is Balaenoptera musculus
4. Kangaroo generic name is Macropus

Andhra Pradesh BIEAP AP Inter 1st Year Zoology Study Material Lesson 3 Animal Diversity-I: Invertebrate Phyla Textbook Questions and Answers.

AP Inter 1st Year Zoology Study Material Lesson 3 Animal Diversity-I: Invertebrate Phyla

Very Short Answer Type Questions

Question 1.
What physical feature pertaining to the organism and its medium do you notice in a sponge body form in which sponges can be/were identified as animals and not plants? What do you call the region in the sponge body in which you noticed that feature?
Answer:
Sponges are primitive multicellular and sessile animals and have a cellular level of organisation. The body wall is composed of two layers separated by matrix mosohyl, and are heaving canal system for transport of water through Ostia, having a cavity in the body called a spongocoel hence the sponge are animals and are not plants.

Question 2.
What are the different structures that make up the internal skeleton of a sponge? What are the chemicals involved in the formation of these structures?
Answer:
The internal skeleton of a sponge is made up of different types of spicules.
Calcareous spicules made up of CaCO₃.
Ex: Sycon
Siliceous spicules – are made up of Silicon dioxide – glass.
Ex: Euplectella
Spongin fibres.
Ex: Spongilla

Question 3.
What are the functions of the canal system of sponges?
Answer:
The functions of the canal system of a sponge are gathering of food, respiratory exchange of gases, and removal of wastes.

Question 4.
What are the two chief morphological ‘body forms’ of cnidarians? What are their chief functions?
Answer:
The body form of Cnidarians is polyp and medusa. Polyp produces medusae by asexual reproduction. Medusae produce polyps by sexual reproduction.

Question 5.
What is metagenesis? Animals belonging to which phylum exhibit metagenesis?
Answer:
Cnidarians show two basic body forms called polyp and medusa. Cnidarians which exist in both forms exhibit alternation of generations called metagenesis.

Question 6.
What is the cnidarian group with quantitatively/relatively large mesoglea? What is the significance of such a well-developed mesoglea pertaining to the aquatic life of that group?
Answer:
The Scyphozoa of cnidarian animals have large mesoglea, it is the significance of these animals.

Question 7.
What is the chief difference between the hydrozoans and the rest, of the cnidarians regarding the germinal layer (s) in which its ‘defencive structures or cells of defence occur?
Answer:
The defencive structures Cnidocytes or Cnidoblasts occur only in the ectoderm, in the hydrozoans in the rest of the Cnidarians the cnidocytes occur in both ectoderm and endoderm.

Question 8.
What are the excretory cells of flatworms called? What is the other important function of these specialized cells?
Answer:
The excretory cells of flatworms are flame cells. Another important function of these specialized cells is osmoregulation.

Question 9.
Distinguish between amphids and phasmids.
Answer:
Amphids: These are the cuticular depressions present on the lips surrounding the mouth in the nematodes such as Aphasmidia animals and serve as Chemoreceptors.
Phasmids: These are the well-developed sensory organs and they occur in some nematodes such as phasmidia animals.

Question 10.
What is the essential difference between a ‘flat worm’ and a ’round worm’ with reference to the perivisceral area of the ‘bodies’.
Answer:
With the reference to the perivisceral area of the body, the flatworms have dorso-ventrally flattened bodies. The body is not segmented, but some of the animals exhibit pseudometamerism. In the Nematoda the body is circular in cross-section, hence the name roundworms, body is not segmented.

Question 11.
How do you account for the origin of the perivisceral space in the body of a nematode and an annelid?
Answer:
The perivisceral space in the body of a nematode is circular in cross-section. Hence the name ‘wound worms’ body unsegmented. In an annelid, the body is segmented by septa into segments or metameres (annulus – little rings) some of them (Nereis) possess lateral appendages parapodia.

Question 12.
What is metamerism? What is the essential difference between the mode of formation of individual morphological body units of a tapeworm and those of an earthworm?
Answer:
The body is divided into segments like units called metameres. Like the divination in known as metamerism.
Ex: Earthworm.
In tapeworm body segments are pseudometameres.
In earthworms, body segments are true segments or metameres.

Question 13.
How do you distinguish a ‘hirudineaun’ from the rest of the annelids, based on the morphological features pertaining to metamerism? How does the coelom of a leech differ from the coelom of an earthworm with reference to its contents?
Answer:
In hirudinean like Leach, the body is with a definite number of segments. The segments are externally sub-divided into annute, internal segmentation’ is absent.
In Leech coelom is filled with a characteristic tissue called botryoidal tissue. In earthworms, the coelom is filled with coelomic fluid.

Question 14.
What do you call the locomotor structures of Nereis? Why is Nereis called a polychaete?
Answer:
Locomotor structures of Nereies are parapodia. The parapodia bear many setae that help in locomotion hence the name Polychaeta.

Question 15.
What is botryoidal tissue?
Answer:
The coelom of Leech is filled with a characteristic tissue called botryoidal tissue, it is resembling a bunch of grapes. They range from excretion to storage of iron, calcium, and revascularization in areas of injury.

Question 16.
What is the difference between the epidermis of a Nematoda and that of an annelid? How does a nematode differ from an annelid with reference to the musculature of the body wall?
Answer:
The epidermis of Nematoda is syncytial and the epidermis of annelid animals is informed by one cell thick ectodermal epithelial cells.

Question 17.
What do you call the first and second pairs of cephalic appendages of a scorpion?
Answer:
The first and second pairs of cephalic appendages of a Scorpion are Chelicerae and Pedipalpi.

Question 18.
What is the uniqueness of the first two pairs of cephalic appendages of a crustacean compared to those of the other extant arthropods?
Answer:
In crustaceans, cephalic appendages are two pairs of antennae (antennules and antennae). It is the unique feature of Crustaceans compared to those of the other extent arthropods.

Question 19.
What is the sub-phylum to which ‘ticks’ and ‘mites’ belong? How do you distinguish them from insects with reference to their walking legs?
Answer:
Ticks and mites belongs to the sub-phylum Chelicerata and class Arachnida. These have four pairs of walking legs.

Question 20.
What are the respiratory structures of Limulus and Palamnaeus respectively?
Answer:
The respiratory structures of Limulus are book gills, and in palamnaeus are book-lungs.

Question 21.
What ara antennae? What is the arthropod group without antennae?
Answer:
Antennae are the sensory organs, of the animals of sub-phylum-Mandibulata of arthropod bear antennae.

Question 22.
What do you call the perivisceral cavity of an arthropod? Where from is it derived during development?
Answer:
The perivisceral cavity of an Arthropoda is a haemocoel, it is not true coelom, but derived from mostly the embryonic blastocoel.

Question 23.
Which arthropod, you have studied, is called a living fossil? Name its respiratory organs.
Answer:
The arthropod animal Limulus is called a living fossil, it is respiratory organs are book-gills.

Question 24.
How do you identify a Chiton from its external appearance? How many pairs of gills help in the respiration of Chiton?
Answer:
Chiton is bilaterally symmetrical and dorsoventrally flattened. Shell is dorsal and consists of eight transverse plates. Poat is ventral elongated and flat. Gills are 6 to 88 pairs helps in respiration.

Question 25.
What is the function of the radula? Give the name of the group of mollusks that do not possess a radula.
Answer:
The buccal cavity contains a file-like rasping organ called radula for feeding, except for the bivalves and tusk of Molluscs.

Question 26.
What is the other name for the gill of a mollusc? What is the function of osphradium?
Answer:
The other name for the gill of a mollusc is Ctenidia. The main function of Osphradium is to test the purity of water.

Question 27.
What is Aristotle’s lantern 7 Give one example of an animal possessing it?
Answer:
In the mouth of the sea Urchin a complex five Jawed masticatory apparatus called Aristotle’s Lantern.
Ex: Echinus.

Question 28.
What is the essential difference between the Juveniles and adults of echinoderms, symmetry-wise?
Answer:
The adult echinoderms are radially symmetrical (pentamerous radial symmetry), but Juveniles (Larvae) are bilaterally Symmetrical.

Question 29.
What are blood glands in pheretima?
Answer:
Blood glands are present in the 4th, 5th, and 6th segments of pheretima. They produce blood cells and haemoglobin which is dissolved in the plasma.

Question 30.
What are spermathecae on the body of pheretima?
Answer:
In Pheretima there are four pairs of spermothecae are located in the segments 6th to 9th as one pair in each segment. This receives and stores spermatozoa during copulation.

Short Answer Type Questions

Question 1.
Write short notes on the salient features of the anthozoans.
Answer:

1. Anthozoans are commonly referred to as sea anemones.
2. Anthozoa includes sea anemones, corals, and sea pens.
3. All are marine forms. These are solitary or colonial.
4. They are sedentary and only have polypoid information.
5. Coeienteron is divided into several compartments by vertical septa called mesenteries.
6. Mesoglea contains connective tissue.
7. Cnidocytes occur both in the ectoderm and endoderm and are cellular and contain amoebocytes.
8. Germ cells are derived from the endoderm. Ex: Adamsia (sea anemone), Gorgonia (sea fan), Pennatula (sea pen).

Question 2.
What is the class to which the flukes belong? Write short notes on the chief characters of the group.
Answer:
Flukes belong to the class Trematoda of Phylum-Platyhelminthes.

1. Trematoda organs are commonly called flukes.
2. These are parasitic on other animals.
3. The body is covered by a thick cuticle and bears two suckers, an oral and a ventral.
4. The mouth is anterior and the intestine is bifurcated.
5. These are bisexual (monoecious).
6. Life history is complex with many hosts and different types of stages – miracidium, sporocyst, redia, cercaria, etc. Ex: Fasciola (Liver fluke), Schistosoma (blood fluke).

Question 3.
What are the salient features exhibited by Polychaetes?
Answer:

1. These are commonly known as bristle worms.
2. All are marine. Many are burrowing, others are free swimming or crawling or tubicolous.
3. Head is distinct with sensory structures like eyes, antennae, palps, and cirri.
4. Clitellum is absent.
5. Each segment has a pair of lateral appendages called parapodia in which bundles of setae are arranged.
6. Animals are unisexual. Most segments bear glands. Gonoducts are absent.
7. Gametes are shed into the coelom.
8. Fertilization is external.
9. Development includes a trochophore larva. Ex: Nereis

Question 4.
How do the hirudineans differ from the polychaetes and oligochaetes?
Answer:

1. Definite number of body segments are present in hirudinean but many segments are present in polychaetes and earthworms.
2. Locomotion in leeches is by suckers but body setae in oligochaetes and parapodia in polychaetes. Parapodia also help in respiration.
3. Temporary clitellum during the breeding season is present in leeches but clitellum is absent in polychaetes and permanent clitellum is present in oligochaetes.
4. Hirudineans are bisexuals, oligochaetes are bisexual and polychaetes are unisexual animals.
5. Coelom is reduced on leeches, but coelom is spacious in oligochaetes and polychaetes.
6. Development is direct in leeches and earthworms but indirect in polychaetes.
7. Nutrient tissue called botryoidal tissue fills the coelom in hirudinean.
8. Anterior and posterior suckers are present in hirudineans. Such suckers are absent in polychaetes and oligochaetes. Ex: Pheretima, Tubifex

Question 5.
What are the chief characteristics of crustaceans?
Answer:

1. This includes prawns, crabs, lobsters, crayfishes, etc.
2. Mostly marine, a few are fresh water and some are adapted to terrestrial life.
3. In most species, the head and thorax fuse to form a cephalothorax.
4. Cephalic appendages are five pairs – first antennae (antennules) second antennae, mandibles, first maxillae and second maxillae.
5. Thoracic and abdominal appendages are typically biramous
6. Respiration is by gills.
7. Excretory organs are green glands or antennal glands.
8. Sense organs include statocysts, compound eyes, and antennae.
9. Gonopores are paired.
10. Development is direct or indirect involving several larval stages. The basic larva is nauplius. Ex: Palaemon (Prawn); Cancer (Crab).

Question 6.
Mention the general characters of Arachnida.
Answer:

1. This includes scorpions, spiders, ticks, and mites.
2. Primarily they are all terrestrial.
3. Prosoma bears one pair of pre-oral chelicerae, one pair of post-oral pedipalps, and four pairs of walking legs.
4. In spiders each chelicera bears a fang into which the poison gland opens.
5. Abdominal appendages are modified into book lungs, spinnerets, pectines, etc.
6. Telsun is usually absent. It is present as a sting in scorpions.
7. Respiration is by book lungs or tracheae.
8. Excretory organs are coaxial glands and malpighian tubules.
9. Scorpions are viviparous.
10. Development is direct. Ex: Palamnaeus (scorpion); Aranea (spider).

Question 7.
Compare briefly a centipede and a millipede.
Answer:

Question 8.
Cephalopods show several unique or advanced features when compared to the other molluscs. Discuss briefly.
Answer:

1. The class Cephalopoda includes cuttlefishes, squids, octopuses, nautilus, etc.
2. The Head is discrete and bears very conspicuous eyes.
3. Shell is either present (e.g.: Sepia) or absent (e.g.: Octopus). When present it may be multi-charactered and external (e.g.: Nautilus) or internal (e.g.: Loligo).
4. The foot is modified into eight to ten arms (tentacles) present around the mouth and siphons.
5. Some Cephalopods (e.g: Sepia) possess an ink gland as a defensive adaptation.
6. Ctenidia are two or four in number – dibranchiate. e.g.: Sepia and tetrabranchiates. (e.g.: nautilus)
7. The brain is complex and is protected by a cartilaginous cranium.
8. Eyes are superficially similar to those of vertebrates.
9. Development is direct. Ex: Architeuthis (giant squid).

Question 9.
Which class of Mollusca represents the primitive molluscs? What are their chief features?
Answer:
The primitive molluscs are represents the class Aplacophora of Phylum-Mollusca.
These are primitive forms with ‘worm-like’ bodies. These are marine forms without mantle, shell, foot, and nephridia. The Head is poorly developed. A rasping organ radula is present in the buccal cavity. Cuticle contains calcareous spicules. Eyes, statocysts, and tentacles are absent. The heart consists of a single auricle and a ventricle. A pair of gonads are present in some, there is a mid-ventral groove that is homologous to the foot of the other molluscs.
Ex: Neonmia, Chaetoderma.

Question 10.
What are the salient features of the echinoids?
Answer:

1. It includes sea urchins, heart urchins, sand dollars, etc. The body is ovoid or discoidal and covered by movable spines.
2. Arms are absent, tube feet are arranged in five bands, and bear suckers.
3. Ossicles of the body unite to form a rigid test or corona or case.
4. Pedicellaria is “three jawed”.
5. Anus and madreporite are aboral in position.
6. Ambulacral grooves are closed.
7. A complex five-jawed masticatory apparatus called Aristotle’s lantern is present just inside the mouth. It is absent in heart urchins.
8. Life history includes a larval form called echinopluteus.
9. Specialized gills called peristomial gills as present in sea urchins. Eg: Salmacis (Sea urchin), Echino Cardium (Heart urchin), Clypeastoer (Cake Urchin).

Question 11.
Mention the salient features of Holothuroidea.
Answer:
Holothuroidea: This class includes sea cucumbers. Body elongated in the oro-aboral axis. Arms, spines, and pedicellariae are absent skin are soft and leathery (Coriaceous). The dermis contains microscopic, isolated ossicles. The madreporite is internal, suspended in the perivisceral coelom. Tube feet are provided with suckers. The mouth is surrounded by retractile feeding tentacles, which are modified tube feet, chief gas exchange organs are a pair of respiratory trees that arise from the wall of the cloaca and form branched tubes in the perivisceral coelom. The development includes auricularia and doliolaria larvae.
Ex: Cueumaria, synaptic, Thyone.

Question 12.
What is the function of nephridia?
Answer:

• The nephridia of pheretima are ectodermal in origin and are metanephridia.
• Several types of nephridia occur in pheretima but are fundamentally similar in structure.
• Which opens outside through the nephridiopore – The nephridia tolled open nephridia. Ex: Septal nephridia.
• Those who do not have nephridiopore are called closed-type nephridia. Ex: Pharyngeal nephridia.
• Those open at the outer surface are called exonephridia.
• The nephridia play an important role in osmoregulation.
• Earthworms mostly excrete urea as the excretory product and are described as ureotelic animals.

Question 13.
How many types of nephridia occur in pheretima and how do you distinguish them?
Answer:
In Pheretima three types of nephridia are present.

1. Septal nephridia: The septal nephridia are present on the intersegmental septum from 15 & 16 segments onwards to last and are opened into the alimentary canal.
2. Integumentary nephridia: The integumentary nephridia attached to the inner body wall from the 3rd segment to the last. They open to the exterior on the body surface by nephridiopores.
3. Pharyngeal nephridia: The pharyngeal nephridia present three paired tufts in the segments 4tfl, 5th, and 6th. They open into the buccal cavity and pharynx.

Question 14.
Give an account of the hearts in the circulatory system of pheretima.
Answer:
Hearts in Pheretima: The dorsal blood vessel and the ventral blood vessel are connected by a pair of pulsatile hearts, in each of the seventh, ninth, twelfth, and thirteenth segments. Of these four pairs, the anterior two pairs connect only the dorsal blood vessel to the ventral blood vessel. Hence they are ’ called lateral hearts. The posterior two pairs connect both the dorsal blood vessel and the supra-oesophageal blood vessel with the ventral blood vessel. Hence, they are called lateral oesophageal hearts. These two types of hearts also differ in the number and arrangement of their valves. Four pairs of valves are present in each lateral heart, while three pairs of valves are present in each lateral oesophageal heart. Hearts allow the blood to flow into the ventral blood vessel only.

Long Answer Type Questions

Question 1.
Draw a labelled diagram of the reproductive organs of Pheretima.
Answer:
Reproductive organs of pheretima: Pheretima is a hermaphrodite (bisexual). There are two pairs of testes. One pair each present in the 10th and 11th segments. Their vasa deferentia run up to the 18th segment where they join the prostatic ducts. Two pairs of seminal vesicles present in the 11th and 12th segments are sacs in which spermatogonia mature into spermatozoa. The common prostatic and spermatic ducts open to the exterior by a pair of male genital pores on the ventrolateral sides of the 18th segment. Two pairs of accessory glands’ are present one pair each in the 17th and 19th segments. Four pairs of spermathecae are located in the segments 6th to 9th (one pair in each segment). They receive and store spermatozoa (spermatophores) during copulation.

One pair of ovaries is attached to the posterior face of the inter-segmental septum of the 12th and 13th segments. Oviducal funnels are present beneath the ovaries and they continue into oviducts (14th segment). They join together and open to the exterior on the ventral side of the 14th segment by a single median female genital pore.

Question 2.
Describe the digestive system and process of digestion in pheretima.
Answer:
The digestive system in pheretima: The alimentary canal is a straight tube and runs from the first to the last segment of the body. The mouth opens into the buccal cavity (1-3 segments) which leads into the muscular pharynx (4th segment). A small narrow tube, oesophagus (5-7 segments), continues into a muscular gizzard (8th segment). It helps in grinding the small particles of food in the decaying leaves (grinding mill). The stomach extends from segments 9 to 14. The food of earthworms is decaying leaves and other organic matter mixed with the soil. Calciferous glands, present in the stomach, neutralise the humic acid present in the humus of the soil. The intestine starts from the 15th segment and continues till the last segment.

A pair of short and conical intestinal caeca project from the intestine in the 26th segment. An internal median fold of the dorsal wall of the intestine called typhiosole, helping in increasing the area of absorption, is poorly developed in Pheretima (between the 26th and the rectum which occupies the last 23 to 28 segments). The alimentary canal opens to the exterior by a small rounded aperture called the anus. The ingested soil rich in organic matter passes through the digestive tract where digestive enzymes break down complex food into smaller absorbable units. These simpler molecules are absorbed through intestinal membranes and are utilized for various metabolic activities.

Process of digestion: Digestion in earthworms is extracellular. Earthworm obtains their nourishment from the organic debris (detritus) present in the soil. So it is called a detritivore. The pharynx is ejected due to the inside out of the buccal chamber. The pharynx, with the help of its radial-dilator muscles, works as a suction pump in feeding.

The organic food along with the swallowed soil particles is sucked into the pharynx, where it mixes with the salivary secretion. The mucin in the saliva lubricates the gut wall for the easy passage of food and also helps in the formation of the bolus. The proteolytic enzyme in the saliva partly digests the proteins. Then the food reaches the gizzard. Its circular muscle and the thick cuticle grind the food into fine particles. In this state, the food is easily acted upon by the digestive enzymes in the stomach and intestine.

The intestinal juice of an earthworm is comparable to the pancreatic juice of higher animals. All these enzymes like proteases, amylases, and lipases act upon the finely ground food and digest the organic matter in it. Proteases digest proteins into amino acids, amylases digest carbohydrates into glucose and lipases digest lipids into fatty acids and glycerol.

The digested food is absorbed by the intestinal epithelium in the typhlosolar region. The extensive capillary network of blood vessels of the intestine plays a vital role in absorption. The typholosole helps in increasing the area of absorption. The undigested food then passes to the rectum, where water is absorbed from the undigested food. Then the undigested matter is egested out through the anus in the form of worm castings.

Andhra Pradesh BIEAP AP Inter 1st Year Zoology Study Material Lesson 2 Structural Organisation in Animals Textbook Questions and Answers.

AP Inter 1st Year Zoology Study Material Lesson 2 Structural Organisation in Animals

Very Short Answer Type Questions

Question 1.
The body of sponges does not possess a tissue level of organisation, though it is made up of thousands of cells. Comment on it.
Answer:
Even though the sponge’s body is made up of thousands of cells, they exhibit a cellular grade of organization, due to the absence of sensory and nerve cells spongs do not possess a tissue level of organisation.

Question 2.
What is the tissue level of organisation among animals? Which metazoans exhibit this organisation?
Answer:
The tissue level of organisation is the lowest level of organisation among the eumetazoans, exhibited by diploblastic animals like cnidarians.

Question 3.
Animals exhibiting which level of organisation lead the relatively more efficient way of life when compared to those of the other levels of organisation? Why?
Answer:
Animals exhibit an organ-system level of organisation of the animals and are exhibited by the triploblastic animals.
Organ level of organisation is a further advancement over the tissue level in the evolution of levels of organisation.

Question 4.
What is monaxial heteropolar symmetry? Name the group of animals in which it is the principal symmetry.
Answer:
Monaxial heteropolar symmetry: When any plane passing through the central axis of the body divides an organism into two identical parts is called Monaxial heteropolar symmetry or radial symmetry. It is the principal symmetry of diploblastic animals such as Cnidarians and ctenophores.

Question 5.
Radial symmetry is an advantage to sessile or slow-moving organisms. Justify this statement.
Answer:
Animals showing radial symmetry live in water and they can respond equally to stimuli that arrive from all directions. Thus, radial symmetry is an advantage to sessile or slow-moving animals.

Question 6.
What is cephalization? How is it useful to its possessors?
Answer:
Cephalization: Concentration of nerve (Brain) and sensory cells at the anterior end of the body is called Cephalization. As a result of cephalization, these animals can sense the new environment and are more efficient than the other animals in seeking food, locating mates, and avoiding or escaping from predators.

Question 7.
Mention the animals that exhibited a ‘tube-within-a-tube’ organisation for the first time? Name their body cavity.
Answer:
Cnidarians and some flat warms are the first animals to exhibit a ‘tube-within-a-tube’ organisation. The body cavity is pseudocolor.

Question 8.
Why is the true coelom considered a secondary body cavity?
Answer:
During the embryonic development of the coelomates, the blastocoel is replaced by a true coelom derived from the mesoderm. So, the true coelom is also called ‘the secondary body cavity.

Question 9.
What are retroperitoneal organs?
Answer:
Certain organs such as the kidneys of the vertebrates are covered by the parietal peritoneum only on their ventral side. Such a peritoneum is called the ‘retroperitoneum’ and the organs lined by it are called ‘retroperitoneal organs.

Question 10.
If the mesentoblast cell is removed in the early embryonic development of protostomes what would be the fate of such animals?
Answer:
In the protostomes, the mesentoblast cell of the early embryo divides to form mesodermal blacks between the ectoderm and the endoderm and replaces the blastocoel. The split that appears in each mesodermal black leads to the formation of Schizocoelom. If the mesentoblast cell is removed in the early embryonic development of protostomes it will cause no ceolome in their animals.

Question 11.
What is enterocoelom? Name the enterocoelomate phyla in the animal kingdom.
Answer:
Animals in which the body cavity is formed from the mesodermal pouches of archenteron are called ‘enterocoelomates’.
Echinoderms, hemichordates, and chordates are enterocoelomates.

Question 12.
Stratified epithelial cells have a limited role in secretion. Justify their role in our skin.
Answer:
The main function of stratified epithelial cells is to provide protection against chemicals and mechanical stress. Hence the stratified epithelial cells have a limited role in secretion.

Question 13.
Distinguish between exocrine and endocrine glands with examples.
Answer:
Exocrine glands are provided with ducts. Secrete mucus, saliva, earwax, oil, milk, digestive enzymes, and other cell products.
Endocrine glands are ductless and their products are hormones that are not sent out via ducts but are carried to the target organs by blood.
Ex: Pituitary gland.

Question 14.
Distinguish between holocrine and apocrine glands.
Answer:
Apocrine glands in which the apical part of the gland cell in pinched off along with the secretory product.
Ex: Mammary glands
Holocrine glands, in which the entire cell disintegrates to discharge the contents.
Ex: Sebaceous glands

Question 15.
Mention any two substances secreted by mast cells and their functions.
Answer:
Mast cells secrete heparin – an anticoagulant, histamine, bradykinin – vasodilators, and serotonin – vasoconstrictor. Vasodilators cause inflammation in response to injury and infection.

Question 16.
Distinguish between a tendon and a ligament.
Answer:
Tendons are the collagen fibrous tissue of dense regular connective tissue which attaches the skeletal muscles to bones.
Ligaments are also the collagen fibers tissue of dense regular connective tissue which attach bones to other bones.

Question 17.
Distinguish between brown fat and white fat.
Answer:
White fat: It is the predominant type in adults, the adipocyte has a single large lipid droplet. White fat is metabolically not active.
Brown fat: It is found in fetuses and infants. Adipocyte of Brown fat has several small ‘lipid droplets’ and are metabolically active and generates heat to maintain body temperature required by infants.

Question 18.
What is the strongest cartilage? In which regions of the human body, do you find it?
Answer:
The fibrous cartilage is the strongest of all types of cartilage. It occurs in the intervertebral discs and pubic symphysis of the pelvis.

Question 19.
Distinguish between osteoblasts and osteoclasts.
Answer:
Osteoblasts are immature bone cells that secrete the organic components of the matrix and also play an important role in the mineralization of bone and become Osteocytes. Osteoclasts are phagocytic cells involved in the resorption of bone.

Question 20.
Define Osteon.
Answer:
In compact bone structure, a Haversian canal and the surrounding lamellae and lacunae are collectively called a Haversian system or Osteon.

Question 21.
What are Volkmann’s canals? What is their role?
Answer:
In compact bone structure, the Haversian canals communicate with one another, with the periosteum and also with the marrow cavity by transverse or oblique canals called Volkmann’s canals.

Question 22.
What is a Sesamoid bone? Give an example.
Answer:
Sesamoid bones are formed by ossification in tendons.
Eg: Patella (Knee cap) and Pisiform bone of the wrist of a mammal.

Question 23.
What is lymph? How does it differ from plasma?
Answer:
Lymph is a colourless fluid. It lacks RBC, platelets, and large plasma proteins, but has more number of leucocytes. It is chiefly composed of plasma and lymphocytes.

Question 24.
What is the hematocrit value?
Answer:
The percentage of the total volume occupied by RBCs in the blood is called the hematocrit value.

Question 25.
What are intercalated discs? What is their significance?
Answer:
The dark lines across cardiac muscle are called intercalated discs (IDS). These discs are highly characteristic of the cardie muscle.

Question 26.
“Cardiac muscle is highly resistant to fatigue”. Justify.
Answer:
The cardiac muscle is highly resistant to fatigue because it has numerous acrosomes, many molecules of myoglobin (Oxygen storing pigment), and a copious supply of blood which facilitate continuous aerobic respiration. The muscles are immune to fatigue and work tirelessly from the embryonic state until death.

Question 27.
Distinguish between ‘nucleus’ and ‘ganglion’ with respect to the nervous system.
Answer:
A group of cell bodies in the Central Nervous System is called a ‘nucleus’, and in the Peripheral Nervous System, it is called a ‘ganglion’.

Question 28.
Distinguish between tracts and nerves with respect to the nervous system.
Answer:
Groups of axons (nerve fibers) in the central nervous system (CNS) are called tracts’ and in the peripheral nervous system (PNS) they are called ‘nerves’.

Question 29.
Name the glial cells that form the myelin sheath around the axons of the central nervous system and peripheral nervous system respectively.
Answer:
In the central nervous system, the glial cells are called ‘Oligodendrocytes’, in the peripheral nervous system, the glial cells are called Schwann cells.

Question 30.
Distinguish between white matter and Greymatter of ‘CNS’.
Answer:
Myelinated nerve fibers occur in the white matter of the CNS, and in most peripheral nerves, and Non-myelinated axons are commonly found in the grey matter of the CNS and autonomous nervous system.

Question 31.
What are microglia and what is their origin add a note on their function.
Answer:
Microglial cells are the Neurogila (supporting cells) of cells of CNS which are phagocytic cells, of mesodermal origin.

Question 32.
What are pseudounipolar neurons? Where do you find them?
Answer:
In a unipolar neuron, the soma or cyton is found in the dorsal root ganglion they are called pseudounipolar neurons. These are found in spinal nerves.

Short Answer Type Questions

Question 1.
Describe the four different levels of organization in metazoans.
Answer:
The levels of organisation in metazoans are as follows:
1. Cellular level of organisation: It is the lowest level of organisaiton among the metazoans and ‘ is exhibited by the sponges. Different types of cells are functionally isolated due to the absence of sensory and nerve cells. There is no uniformity of labor among the cells and they don’t form tissues.

2. Tissue level of organisation: This is the lowest level of organisation among the eumetazoans, exhibited by diploblastic animals like the cnidarians. In these animals, the cells which perform the same function are arranged into tissues due to the presence of nerve cells and sensory cells.

3. Organ level of organisation: An aggregation of different kinds of tissues that are specialized for a particular function is called an organ. Organ level of organisation is a further advancement over the tissue level in the evolution of levels of organisation. It is the first time appeared in the members of platyhelminths.

4. Organ-system level: It is the highest level of organisation among the animals and is exhibited by triploblastic animals such as the flatworms, nematodes, annelids, arthropods, molluscs, echinodermates, and chordates. High specilized sensory and nerve cells bring about a higher level of coordination and integration among the various organ systems to lead an efficient way of life.

Question 2.
In which group of bilaterians do you find solid bauplan? Why is it called so?
Answer:
The bilaterian’s body plan is the solid bauplan when only one plane that passes through the identical axis divides an organism into two identical parts, it is called bilateral symmetry. It is the principal type of symmetry in triploblastic animals.

Bilaterally symmetrical animals are more efficient than the other animals in seeking food locating mates and in avoiding or escaping from predators, because of cephalization. As a result of cephalization, bilaterally symmetrical animals can sense the new environment into which they enter and respond more efficiently and quickly.

Question 3.
Mention the advantages of coelom over pseudocolor.
Answer:
Advantages of coelom over pseudocoelom:
1. Visceral organs of eucoelomates are muscular (because of their association with mesoderm) and so they can contract and relax freely independent of the muscular movements of the body wall in the coelomic space, e.g.: peristaltic movements of the alimentary canal.
2. Gametes are released into the coelom in some invertebrates (which do not have glnoducts) and in the female vertebrates.
3. Coelomic fluid receives excretory products and stores them temporarily before their elimination.
4. In the eucoelomates, the mesoderm comes into contact with the endoderm of the alimentary canal, and it causes ‘regional specialization of the gut, such as the development of gizzard, stomach, etc., This is referred to as ‘primary induction’. In the case of the pseudocoelomates, due to the absence of such a contract between the gut and the mesoderm, the wall of the gut does not show complex and highly specialized organs.

Question 4.
Describe the formation of schizocoelom and enterocoelom.
Answer:
Schizocoelom: During embryonic development, a specialized cell called 4d blastomere is formed. The cells formed from these cells divide and redivide and develop blocks of mesoderm in blastocoel. The blocks fuse and form the mesodermal band which later on splits to form the Schizocoelom. This type of coelom is present in Annelida, Arthropoda, and Mollusca.

Enterocoelomates: Animals in which the body cavity is formed from the mesodermal pouches of archenteron are called enterocoelomates. Echinoderms, hemichordates, and chordates are enterocoelomates. In these animals, mesodermal ouches that evaginate from the wall of the archenteron into the blastocoel are fused with one another to form the enterocoelom. All the enterocoelomates are deuterostomes and they show radial and indeterminate cleavage.

Question 5.
Describe briefly the three types of intercellular junctions of epithelial tissues.
Answer:
The specialized ‘junctions’ provide both structural and functional links between the individual cells of an epithelium. They show different types of junctions so as to serve the specific needs of that tissue. They are
(A) Tight junctions: These junctions between epithelial cells prevent ‘leakages’ of body fluids. For example, they prevent leakages of water into the surrounding cells in our sweat glands. The plasma membranes of adjacent cells are tightly pressed against each other and are bound together by specific proteins.

(B) Desmosomes: Muscle cells are provided with “desmosomes” (anchoring junctions) which act as ‘rivets’ binding the cells together into strong sheets. Intermediate filaments made of protein ‘keratin’ anchor desmosomes in the cytoplasm.

(C) Gap junctions: They provide continuous cytoplasmic channels between adjacent cells. Various types of ions, sugar molecules amino acids, etc. can pass from a cell to an adjacent cell through ‘gap junctions. They occur in many types of tissues including the ‘cardiac muscles’ where they allow rapid conduction of impulses or depolarization.

Question 6.
Give an account of glandular epithelium.
Answer:
Glandular epithelium: Some of the columnar or cuboidal cells that get specialised for the production of certain secretions, form glandular epithelium. The glands are of two types.
Unicellular glands: Consisting of isolated glandular cells such as goblet cells of the gut.
Multicellular glands: Consisting of clusters of cells such as salivary glands. On the basis of the mode of pouring of their secretions, glands are divided into two types namely exocrine and endocrine glands.
Exocrine glands: These glands provided with ducts secrete mucus, saliva, earwax, oil, milk, digestive enzymes, etc.
Endocrine glands: These glands are ductless and their products are hormones, which are carried to the target organs by blood.
Based on the mode of secretion, Exocrine glands are further divided into three types.
1. Merocrine glands: Which release the secretory granules without the loss of other cellular material.
Ex: Pancreas
2. Apocrineglands: The apical part of the cell is pinched off along with the secretory product.
Ex: Mammary glands
3. Holocrine glands: The entire cell disintegrates to discharge the contents.
Ex: Sebaceous gland

Question 7.
Give a brief account of the cells of areolar tissue.
Answer:
Areolar tissue: It is one of the most widely distributed connective tissue in the body. It forms the packing tissue in almost all organs. Areolar tissue forms the subcutaneous layer of the skin. It has cells and fibres. Cells of the areolar tissue are fibroblasts, mast cells, macrophages, adipocytes, and plasma cells.
1. Fibroblasts are the most common cells which secrete fibres. The inactive cells are called fibrocytes.
2. Mast cells secrete heparin (an anticoagulant), histamine, bradykinin (vasodilators), and serotonin vasoconstrictor). Vasodilators cause inflammation in response to injury and infection.
3. Macrophages are amoeboid cells, Phagocytic in function, and act as internal scavengers. They are derived from the monocytes of blood. Tissue-fixed macrophages’ are called histiocytes and others are ‘wandering macrophages’.
4. Plasma cells are derived from the B-lymphocytes and produce antibodies.
5. Adipocytes are specialized cells for the storage of fats.

Question 8.
Describe the three types of cartilage.
Answer:
Cartilage is a solid, but semi-rigid (flexible) connective tissue. Cartilage is of three types, which differ from each other chiefly in the composition of the matrix.

Cartilage is a solid, but semi-rigid (flexible) connective tissue It resists compression. Matrix is firm but somewhat pliable. It has collagen fibres, elastic fibres (only in the elastic cartilage), and matrix-secreting cells called chondroblasts. These cells are enclosed in fluid-filled spaces called lacunae. Chocolates are the inactive cells of cartilage. Cartilage is surrounded by a fibrous connective tissue sheath called perichondrium. Cartilage is of three types, which differ from each other chiefly in the composition of the matrix.

1. Hyaline cartilage: It is bluish-white, translucent, and glass-like cartilage. Matrix is homogeneous and shows delicate collagen fibres. It is the weakest and the most common type of cartilage. It is found in the walls of the nose, larynx, trachea, and bronchi.

2. Elastic cartilage: It is yellowish due to elastic fibres. Matrix has an abundance of yellow elastic fibres in addition to collagen fibres. It provides strength and elasticity. Perichondrium is present. It is found in the pinnae of the external ears, Eustachian tubes, and epiglottis.

3. Fibrous cartilage: Matrix has bundles of collagen fibres. The perichondrium is absent. It is the strongest of all types of cartilage. It occurs in the Intervertebral discs and pubic symphysis of the pelvis.

Question 9.
Explain the Haversian system.
Answer:
The compact bone consists of several structural units called Osteons or Haversian systems arranged around and parallel to the bone marrow cavities.

The Haversian system consists of a Haversian canal that runs parallel to the marrow cavity. It contains an artery, a vein, and a lymphatic vessel. The Haversian canal is surrounded by concentric lamellae. Small fluid-filled spaces called ‘lacunae’ provided with minute canaliculi lie in between the lamellae. Canaliculi connect the lacunae with one another and with the Haversian canal.

Each lacuna encloses one osteocyte (an inactive form of osteoblast). The cytoplasmic processes of osteocytes extend through canaliculi. A Haversian canal and the surrounding lamellae and lacunae are collectively called a Haversian system or osteon. The Haversian canals communicate with one another, with the perio¬steum and also with the marrow cavity by transverse or oblique canals called Volkmann’s canals. Nutrients and gases diffuse from the vascular supply of Haversian canals.

Question 10.
Write short notes on lymph.
Answer:
Lymph: Lymph is a colourless fluid. It lacks RBC, platelets, and large plasma proteins, but has more number of leucocytes. It is chiefly composed of plasma and lymphocytes. When compared to the tissue fluid, it contains very small amounts of nutrients and oxygen but has abundant CO2 and other metabolites.

The most important site of the formation of lymph is the interstitial space. As blood passes through the blood capillaries, some portion of blood that includes water, solutes, and proteins of low molecular weight passer: through the walls of capillaries, into the interstitial spaces due to hydrostatic pressure at the arteriolar ends. This fluid forms the interstitial fluid (tissue fluid). Most of the interstitial fluid is returned directly to the capillaries due to osmotic pressure at the venular ends.

A little amount of this tissue fluid passes through a system of lymphatic capillaries (lymph capillaries of the intestinal villi are called ‘lacteals’), vessels, and ducts and finally, reaches the blood through the subclavian veins. The extracellular ’tissue fluid’ that passes into the lymph capillaries and lymph vessels is called ‘lymph’. The lymphatic system represents an ‘accessory route’ by which interstitial fluid flows from tissue spaces into blood.

Question 11.
Describe the structure of a skeletal muscle.
Answer:
Skeletal (striped and voluntary) muscle:
It is usually attached to skeletal structures by ‘tendons’. In a typical muscle such as the ‘biceps’ muscle, skeletal muscle fibre is surrounded by a thin connective tissue sheath, the endomysium. A bundle of muscle fibres is called a fascicle. It is surrounded by a connective tissue sheath called perimysium. A group of fascicles forms a ‘muscle’ which is surrounded by an epimysium (outermost connective tissue sheath). These connective tissue layers may extend beyond the muscle to form a chord-like tendon or sheet-like aponeurosis.

A skeletal muscle fibre is a long, cylindrical, and unbranched cell. It is a multinucleated cell with many oval nuclei characteristically in the ‘peripheral’ cytoplasm (a syncytium formed by the fusion of cells). Sarcoplasm has many myofibrils which show alternate dark and light bands. So it is called striped or striated muscle.

Question 12.
Describe the structure of a cardiac muscle.
Answer:
Cardiac (striped and involuntary) muscle: The cardiac muscle is striated like the skeletal muscle (shows sarcomeres). Cardiac muscle is found in the ‘myocardium’ of the heart of vertebrates. The cardiac muscle cells or the myocardial cells’ are short, cylindrical, mononucleate, or binucleate cells whose ends branch and form junctions with other cardiac muscle cells. Each myocardial cell is joined to adjacent myocardial cells by ‘electrical synapses’ or ‘gap junctions. They permit ‘electrical impulses to be conducted along the long axis of the cardiac muscle fibre. The dark lines across cardiac muscle are called intercalated discs (IDs). These discs are highly characteristic of the cardiac muscle.

Question 13.
Give an account of the supporting cells of nervous tissue.
Answer:
Nervous tissue is of two types.
1. Nervous
2. Supporting cell or neuroglia

Neuroglia (supporting cells): These are the supporting and non-conducting cells that provide a microenvironment suitable for neuronal activity. Unlike neurons, they continue to divide throughout life. Neuroglial cells of the CNS include oligodendrocytes (that form myelin sheath as mentioned above); astrocytes (star-shaped cells) that form an interconnected network and bind neurons and capillaries (helping in providing the blood-brain barrier); ependymal cells, which are ciliated cells that line the cavities of the brain and spinal cord to bring movements in the cerebrospinal fluid; microglial cells, which are phagocytic cells, of mesodermal origin. Neuroglial cells of the peripheral nervous system include the satellite cells and Schwann cells. Satellite cells surround the cell bodies in ganglia, and Schwann cells form neurolemma around axons.

Question 14.
Describe the structure of a multipolar neuron.
Answer:
Multipolar neurons have one axon and two or more dendrites. Most neurons in our body are multipolar neurons.
A neuron usually consists of a cell body with one too many dendrites and a single axon.

Neurons: Neurons are the ‘functional units of nervous tissue. These are electrically excitable cells that receive, initiate, and conduct/transmit impulses. When a neuron is stimulated, an electric disturbance (action potential) is generated which swiftly travels along its plasma membrane. A neuron usually consists of a “cell body” with one to many dendrites and a single axon.

Cell body: It is also called perikaryon, cyton, or soma. It contains abundant granular cytoplasm and a large spherical nucleus. The cytoplasm has Nissl bodies (they represent RER, the sites of protein synthesis), neurofibrils, and lipofuscin granules.

Dendrites: Several short, branched processes that arise from the cyton are called dendrites. They also contain Nissl bodies and neurofibrils. They conduct nerve impulses towards the cell body (afferent processes).

Axon: An axon is a single, long, cylindrical process that originates from a region of the cyton called the axon hillock. The Plasmalemma of an axon is called axolemma, and the cytoplasm is called axoplasm, which contains neurofibrils. However, Nissl bodies are absent. An axon may give rise to collateral branches. Distally it branches into many fine filaments called telodendrites, (axon terminals), which end in bulb-like structures called synaptic knobs or terminal boutons. Synaptic knobs possess ‘synaptic vesicles’ containing chemicals called neurotransmitters.

Question 15.
Write short notes on (a) Platelets and (a) Synapse.
Answer:
(a) Blood platelets (Thrombocytes): These are colourless non- nucleated, round or oval biconvex discs. The number of platelets per cubic mm of blood is about 2,50,000-4,50,000. They are formed from giant megakaryocytes produced in the red bone marrow by fragmentation. The average lifespan of blood platelets is about 5 to 9 days. They secrete thromboplastin and play an important role in blood clotting. They adhere to the damaged endothelial lining of capillaries and seal minor vascular openings.

(b) Synapse: It is the place in between the two neurons or inter-neuronal or neuromuscular junctions. Nerve cells do not have direct contact with each other. There is a microscopic gap of about 200-300 A° present between the nerve cells called a synapse. The nerve cell present before synapse is called the presynaptic neuron and the behind is called the post-synaptic neuron. A neurotransmitter substance called acetylcholine is secreted in the synapse by presynaptic neurons’ telodendrites. Acetylcholine helps in the conduction of nerve impulses from one neuron to another neuron.

Long Answer Type Questions

Question 1.
What is coelom? Explain the different types of coelom with suitable examples and neat labelled diagrams.
Answer:
The body cavity, which is lined by mesoderm, is called coelom more elaborately, coelom is a fluid-filled space between the body wall and visceral organs and lined by mesodermal epithelium peritoneum. Based on the body cavity triploblastic animals can be classified into acoelomentes, pseudo-coelo mates, and coelomates.

Acoelomate bilaterians: The bilaterian animals in which the body cavity is absent are called acoelomates, e.g. Platy-helminthes (lowest bilaterians). In these animals, the mesenchyme derived from the thrid germinal layer, called mesoderm, occupies the entire blasto coel, between the ectoderm and the endoderm, so that the adults have neither the primary cavity (blasto-coelom) nor the secondary cavity (coelom). As there is no body cavity, the acoelomates exhibit a solid body plan.

Pseudocoelomate bilaterians: In some animals, the body cavity is not lined by mesodermal epithelia. Such animals are called Pseudocoelomates. They include the members of phylum Aschelminthes (Nematoda, Rotifera, and some minor phyla). During embryonic development mesoderm (mesenchyme) occupies only a part of the blastocoel adjoining the ectoderm. The unoccupied portion of the blastocoel persists as pseudocoelom.

Eucoelomate bilaterians: Coelom or ‘true coelom’ is a fluid-filled cavity, that lies between the body wall and the visceral organs and is lined by mesodermal epithelium, the peritoneum. The portion of the peritoneum that underlines the body wall is the parietal peritoneum or somatic peritoneum. The portion of the peritoneum that covers the visceral organs is the splanchnic peritoneum or visceral peritoneum. In coelomates, the visceral organs are suspended in the coelom by the peritoneum.

During the embryonic development of the eucoelomates, the blastocoel is replaced by the true coelom derived from the mesoderm. So, the true coelom is also called the ‘secondary body cavity. Based on the mode of formation of coelom, the eucoelomates are classified into two types:

I. Schizocoelomates: Animals in which the body cavity is formed by the ‘splitting of mesoderm’ are called schizocoelomates. Annelids, arthropods, and mollusks are schizocoelomates in the animal kingdom. All the schizocoelomates are protostomians and they show ‘holoblastic’, ‘spiral’, and ‘determinate’ cleavage. The 4d blastomere or mesentoblast cell of the early embryo divides to form mesodermal blocks between the ectoderm and the endoderm and replaces the blastocoel. The split that appears in each mesodermal block leads to the formation of Schizocoelom.

II. Enterocoelomates: Animals in which the body cavity is formed from the mesodermal pouches of archenteron are called enterocoelomates. Echinoderms, hemichordates, and chordates are the enterocoelomates. In these animals, mesodermal pouches that evaginate from the wall of the archenteron into the blastocoel are fused with one another to form the enterocoelom. All the enterocoelomates are deuterostomes and they show radial and indeterminate cleavage.

Question 2.
What is symmetry? Describe the different types of symmetry in the animal kingdom with suitable examples.
Answer:
Symmetry: The concept of symmetry is fundamental in understanding the organisation of an animal. Symmetry in animals is the balanced distribution of paired body parts. The body plan of a vast majority of metazoans exhibits some kind of symmetry. However, most of the sponges and snails show asymmetry (lack of symmetry). The symmetry of an animal and its mode of life are correlated.

Asymmetry: The animals, which cannot be cut into two equal parts (antimeres) in any plane passing through the centre of the body is called asymmetrical, e.g.: most sponges and adult gastropods. In asymmetrical animals, the body lacks a definite form.

Symmetry: The regular arrangement of body parts in a geometrical design relative to the axis of the body is called symmetry. In a symmetrical animal, paired body parts are arranged on either side of the plane passing through the principal axis, such that they are equidistant from the plane. The unpaired body parts are located mostly on the plane, passing through the principal axis.
Basically, the symmetry in animals is of two kinds:
(i) Radial symmetry
(ii) Bilateral symmetry

(i) Radial Symmetry or Monaxial heteropolar Symmetry: When any plane passing through the central axis (oro-aboral axis/principal axis) of the body divides an organism into two identical parts, it is called radial symmetry. The animals with radial symmetry are either sessile or planktonic or sluggish forms. It is the principal symmetry of the diploblastic animals such as the cnidarians and ctenophores symmetrical (as it is five-angled, it is also called pentamerous radial symmetry). Radially symmetrical animals have many planes of symmetry, whereas pentamerous radially symmetrical animals have five planes of symmetry.

(ii) Bilateral symmetry: When only one plane (median sagittal plane) that passes through the central axis (anterior-posterior axis) divides an organism into two identical parts, it is called bilateral symmetry. It is the ‘principal type of symmetry’ in triploblastic animals. Among the triploblastic animals, some gastropods become secondarily asymmetrical though they have primarily bilaterally symmetrical larvae.

Bilaterally symmetrical animals are more efficient than other animals in seeking food, locating mates, and in avoiding or escaping from predators, because of cephalization (concentration of nerve and sensory cells at the anterior end). As a result of cephalization, bilaterally symmetrical animals can sense the new environment into which they enter and respond more efficiently and quickly.

Question 3.
Classify and describe the epithelial tissues on the basis of structural modification of cells with examples.
Answer:
Epithelium (epi-upon; thelia – growing) forms the outer covering of the body and the living of internal organs and cavities. There are two types of epithelial tissues namely ‘simple epithelia1 and ‘compound epithelia’ based on the number of layers or strata.

Simple epithelium is composed of a single layer of cells and forms the lining of body cavities, ducts, and vessels. It helps in the diffusion, absorption, filtration, and secretion of substances. On the basis of the shape of the cells, it is further divided into three types:
(i) Simple squamous epithelium (Pavement epithelium): It is composed of a single layer of flat and tile-like cells, each with a centrally located ‘ovoid nucleus’. It is found in the endothelium of blood vessels, mesothelium of body cavities (pleura, peritoneum, and pericardium), wall of Bowman’s capsule of the nephron, lining of alveoli of lungs, etc.

(ii) Simple cuboidal epithelium: It is composed of a single layer of cube-like cells with centrally located spherical nuclei. It is found in germinal epi – thelium, proximal, and distal convoluted tubules of the nephron. Cuboidal epithelium of proximal convoluted tubule of nephron has ‘microvilli’.

(iii) Simple columnar epithelium: It is composed of a single layer of tall and slender cells with oval nuclei located near the base. It has mucus-secreting ‘goblet cells’ in some places. It is of two types:
(a) Ciliated columnar epithelium: Columnar epithelial cells have cilia on their free surface. It is mainly present in the inner surface of hollow organs like fallopian tubes, ventricles of the brain, the central canal of the spinal cord, bronchioles, etc.

(b) Non-ciliated columnar epithelium: Columnar cells are without cilia. It is found in the lining of the stomach and intestine. Microvilli are present in the columnar epithelium of the intestine to increase the surface area of absorption.

(II) Compound epithelium (stratified epithelium): It is made up of more than one layer of cells. Its main function is to provide protection against chemical and mechanical stress. It covers the dry surface of the skin as stratified, keratinized, squamous epithelium. It covers the moist surface of the buccal cavity, pharynx, esophagus, and vagina as stratified non-keratinized squamous epithelium. It forms the inner lining of the larger ducts of salivary glands, sweat glands, and pancreatic ducts as stratified cuboidal epithelium. It forms the wall of the urinary bladder as transitional epithelium.

(III) Glandular epithelium: Some of the columnar or cuboidal cells that get specialised for the production of certain secretions, form glandular epithelium. The glands are of two types – unicellular glands consisting of isolated glandular cells such as goblet cells of the gut, and multicellular glands, consisting of clusters of cells such as salivary glands. On the basis of the mode of pouring of their secretions, glands are divided into two types namely exocrine and endocrine glands. Exocrine glands are provided with ducts; that secrete mucus, saliva, earwax (cerumen), oil, milk, digestive enzymes, and other cell products. In contrast, endocrine glands are ductless and their products are ‘hormones’, which are not sent out via ducts, but are carried to the target organs by blood.

Based on the mode of secretion, exocrine glands are further divided into
(i) merocrine glands (e.g.: pancreas) which release the secretory granules without the loss of other cellular material.

(ii) Apocrine glands (e.g.: mammary glands) in which the apical part of the cell is pinched off along with the secretory product and
(iii) Holocrine glands (e.g.: sebaceous glands), in which the entire cell disintegrates to discharge the contents.

Question 4.
Describe the various types of connective tissue properly with suitable examples.
Answer:
Connective tissue proper is of two types as
(A) Loose connective tissue proper
(B) Dense connective tissue proper

(A) Loose connective tissue: Cells and fibres are loosely arranged in a semi-fluid ground substance there are three types of loose connective tissues-areolar tissue adipose tissue and reticular tissue.
(i) Areolar tissue: It is one of the most widely distributed connective tissues in the body. It forms the packing tissue in almost all organs. Areolar tissue forms the subcutaneous layer of the skin. It has cells and fibres. Cells of the areolar tissue are the fibroblasts, mast cells, macrophages, adipocytes, and plasma cells.
1. Fibroblasts are the most common cells with secreted fibres. The inactive cells are called
fibrocytes.
2. Mast cells secrete heparin (an anticoagulant), histamine, bradykinin (vasodilators), and serotonin (vasoconstrictor), vasodilators cause inflammation in response to injury and infection.
3. Macrophages are amoeboid cells, phagocytic in function, and act as internal scavengers. They are derived from the monocytes of blood. ‘Tissue fixed macrophages’ are called histiocytes and others are ‘wandering macrophages’.
4. Plasma cells are derived from the B-lymphocytes and produce antibodies.
5. Adipocytes are specialized cells for the storage of fats.

(ii) Adipose tissue: It is specialized for fat storage. It consists of a large number of adipocytes and few fibres. The adipose tissue which is found beneath the skin provides. Adipose tissue is of two types: white adipose tissue, and brown adipose tissue. Excess nutrients which are not used immediately are converted into fats and stored in this tissue.
White adipose tissue (WAT): It is the predominant type in adults, and the adipocyte has a single large lipid droplet (monocular). White fat is metabolically not active.
Brown adipose tissue (BAT): It is found in fetuses and infants. Adipocyte of BAT has several small ‘lipid droplets’ (multilocular) and numerous mitochondria. Brown fat is metabolically active and generates ‘heat’ to maintain the body temperature required by infants.

(iii) Reticular tissue: It has specialized fibroblasts called reticular cells. They secrete ‘reticular fibers’ that form an interconnecting network. It forms the ‘supporting framework’ of lymphoid organs such as bone marrow, spleen, and lymph nodes and forms the reticular lamina of the ‘basement membrane’.

(B) Dense connective tissue: This tissue consists of more fibres, but fewer cells. It has very little ground substance. Based on the arrangement of fibres, the dense connective tissue is of three types.
(i) Dense regular connective tissue: In this tissue, collagen fibres are arranged parallel to one another in bundles. Tendons that attach the skeletal muscles to bones and ligaments which attach bones to other bones are examples of this type of connective tissue.

(ii) Dense irregular connective tissue: In this type of connective tissue, bundles of collagen fibres are irregularly arranged. Periosteum, endosteum, pericardium, heart valves, joint capsule, and deeper region of the dermis of skin contain/are made up of this type of connective tissue.

(iii) Elastic connective tissue: It is mainly made of yellow elastic fibres, capable of considerable extension and recoil. This tissue can recoil to its original shape, when the forces of stretch are released. It occurs in the wall of arteries, vocal cords, trachea, bronchi, and ‘elastic ligaments’ present between vertebrae.

In addition to the above-mentioned connective tissues, mucous connective tissue occurs as foetal or embryonic connective tissue. It is present in the umbilical cord as Wharton’s jelly.

Question 5.
What is skeletal tissue? Describe the various types of skeletal tissue.
Answer:
Skeletal tissue (supporting tissue): It forms the endoskeleton of the vertebrates. It supports the body, protects various organs, provides a surface for the attachment of muscles, and helps in locomotion. It is of two types:
(A) Cartilage (Gristle): Cartilage is a solid, but semi-rigid (flexible) connective tissue. It resists compression. Matrix is firm but somewhat pliable. It has collagen fibres, elastic fibres (only in the elastic cartilage), and matrix-secreting cells called chondroblasts. These cells are enclosed in fluid-filled spaces called lacunae. Chondrocytes are the inactive cells of cartilage. Cartilage is surrounded by a fibrous connective tissue sheath called perichondrium.

Cartilage is of three types, which differ from each other chiefly in the composition of the matrix.
1. Hyaline cartilage: It is bluish-white, translucent, and glass-like cartilage. Matrix is homogeneous and shows delicate collagen fibres. It is the weakest and the most common type of cartilage. It is found in the walls of the nose, Larynx, trachea, and bronchi.

2. Elastic cartilage: It is yellowish due to elastic fibres. Matrix has an abundance of yellow elastic fibres in addition to collagen fibres. It provides strength and elasticity. Perichondrium is present. It is found in the pinnae of the external ears, Eustachian tubes, and epiglottis.

3. Fibrous cartilage: Matrix has bundles of collagen fibres. The perichondrium is absent. It is the strongest of all types of cartilage. It occurs in the intervertebral discs and pubic symphysis of the pelvis.

(B) Bone (osseous) tissue: Bone is highly calcified (mineralized), solid, hard and rigid connective tissue. It is the major component of the endoskeleton of most adult vertebrates.

Bone has an outer fibrous connective tissue sheath called periosteum, the inner connective tissue sheath that lines the marrow cavity called the endosteum, a non-living extracellular matrix, living cells, and bone marrow. Bone cells include osteoblasts, osteocytes, and osteoclasts. Osteoblasts (immature bone cells) secrete the organic components (collagen fibres) of the matrix and also play an important role in the ‘mineralization of bone’ and become osteocytes (mature bone cells). Osteocytes are enclosed in fluid-filled lacunae. Osteoclasts are phagocytic cells involved in the resorption of bone.

Types of bones based on the method of formation:
(i) Cartilage bones (replacing bones or endochondral bones) are formed by ossification within the cartilage e.g. bones of limbs, girdles, and vertebrae.
(ii) Investing bones (membrane bones or dermal bones) are formed by the ossification in the embryonic mesenchyme e.g. most of the bones of the cranium.
(iii) Sesamoid bones are formed by ossification in tendons e.g.: patella (knee cap) and pisiform bone of the wrist of a mammal
(iv) are formed by ossification in the soft tissues, e.g.: Oscordis (inside the heart of ruminants), and Ospenis (inside the glans-penis of many mammals such as rodents, bats, and carnivores).

Types of bones based on the structure:
1. Spongy bone (Cancellous bone or trabecular bone): It occurs in the epiphyses and metaphyses
of long bones. It looks spongy and contains columns of bone called ‘trabeculae’ with irregular interspaces filled with red bone marrow.
2. Compact bone: The diaphysis of a long bone is made up of ‘compact bone. It has a dense continuous lamellar matrix between the periosteum and endosteum.

Structure of a compact bone: Diaphysis (shaft) is a part of a long bone that lies in between expanded ends. The diaphysis is covered by a dense connective fibrous tissue called the periosteum. The diaphysis of a long bone has a hollow cavity called marrow cavity which is lined or surrounded by the endosteum. In between periosteum and endosteum, the matrix of the bone is laid down in the form of ‘lamellae’. Outer circumferential lamellae are located immediately beneath the periosteum; inner circumferential lamellae are located around the endosteum.

Between the outer and inner circumferential lamellae, there are many Haversian systems (osteons – units of bone). The spaces between the Haversian systems are filled with interstitial lamellae. Haversian system consists of a Haversian canal that runs parallel to the marrow cavity. It contains an artery, a vein and a lymphatic vessel. Haversian canal is surrounded by concentric lamellae. Small fluid filled spaces called ‘lacunae’ provided with minute canaliculi lie in between the lamellae.

Canaliculi connect the lacunae with one another and with Haversian canal. Each lacuna encloses one osteocyte (inactive form of osteoblast). The cytoplasmic processes of osteocytes extend through canaliculi. A Haversian canal and the surrounding lamellae and lacunae are collectively called a Haversian system or osteon. The Haversian canals communicate with one another, with the periosteum and also with the marrow cavity by transverse or oblique canals called Volkmanns canals. Nutrients and gases diffuse from the vascular supply of Haversian canals.

Question 6.
Give an account of the “formed elements” of Blood.
Answer:
Blood is a red-coloured, opaque, and slightly alkaline fluid. It is composed of blood plasma and formed elements or blood cells – the RBC, WBC, and platelets.
Formed elements of Blood cells: The blood corpuscles (RBC and WBC) constitute 45% of the total blood by volume.

(i) Red blood corpuscles (Erythrocytes): Erythrocytes of mammals are circular (elliptical in camels and Liamas), biconcave and enucleate. The biconcave shape provides a large surface area-to-volume ratio, thus providing more area for the exchange of gases. These are 7.8 pm in diameter. The number of RBCs per cubic millimeter of blood is about 5 million in a man and 4.5 million in a woman.

(ii) White blood corpuscles (Leucocytes): These are nucleate, colourless, complete cells. They are spherical or irregular in shape and are capable of exhibiting amoeboid movement into the extravascular areas by diapedesis. WBC are two main types: 1) Granulocytes and 2) Agranulocytes.

Granulocytes: They possess cytoplasmic granules that may take three different types of stains, neutral or acidic, or basic. The nucleus of the granulocytes is divided into lobes and assumes different shapes, hence, these are also called polymorphonuclear leucocytes. Based on the staining properties these are of three tvoes.

Basophils: They constitute about 0.4% of the total leucocytes. The nucleus is divided into irregular lobes. Cytoplasmic granules are ‘fewer’ and ‘irregular’ in shape. They take basic stains. They produce heparin, histamine, etc. They supplement the function of mast cells when needed.

Eosinophils (acidophils): They constitute about 2.3% of the total leucocytes. The nucleus is distinctly bilobed. The cytoplasm has large granules which stain with acidic dyes such as ‘eosin’.

Neutrophils: They constitute about 62% of the total leucocytes. The nucleus is many lobed (2-5). Specific cytoplasmic granules are small and abundant. They stain with ‘neutral dyes’.

Agranulocytes: Cytoplasmic granules are absent in agranulocytes. divided into lobes. These are of two types:
(a) Lymphocytes: They constitute about 30% of the total leucocytes. They are small, spherical cells with large spherical nuclei and scanty peripheral cytoplasm. There are functionally two types of lymphocytes – ‘B’ lymphocytes, which produce ‘antibodies’ and T lymphocytes which play a key role in the immunological reactions of the body. Some lymphocytes live only a few days while others survive for many years.

(b) Monocytes: They constitute about 5.3% of the leucocytes. The nucleus is kidney-shaped (reniform). These are the largest, motile phagocytes. They engulf bacteria and cellular debris. They differentiate into macrophages when they enter the connective tissues.

(iii) Blood platelets (Thrombocytes): These are colourless non-nucleated, round, or oval biconvex discs. The number of platelets per cubic mm of blood is about 2,50,000-4,50,000. They are formed from giant megakaryocytes produced in the red bone marrow by fragmentation. The average lifespan of blood platelets is about 5 to 9 days. They secrete thromboplastin and play an important role in blood clotting. They adhere to the damaged endothelial lining of capillaries and seal minor vascular openings.

Question 7.
Compare and contrast the three types of muscular tissues.
Answer:
Muscular tissue is mesodermal in origin. Muscles show three essential properties such as excitability, conductivity, and contractility. The study of muscular tissues is known as mycology. Muscular tissue has elongated cells called ‘muscle fibers’ (myocytes) which are surrounded by a connective tissue sheath. The extracellular matrix is absent. The plasma membrane of a muscle fiber is called sarcolemma.

The cytoplasm of a muscle fibre is called Sarco plasm, the endoplasmic reticulum, the sarcoplasmic reticulum, and the mitochondria, the Sarcosomes. The cytoplasm of a muscle fibre has several myofibrils. Each myofibril has thick (myosin) and thin (actin) myofilaments. The regular arrangement of myosin and actin filaments is responsible for the alternate dark and light bands of a ‘striated muscle’. Sarcoplasm also contains ATP, phosphocreatine, glycogen, and myoglobin. Muscles are of three types – skeletal, smooth, and cardiac.

Skeletal (striped and voluntary) muscle: It is usually attached to skeletal structures by ‘tendons’. A typical muscle such as the ‘biceps’ muscle/skeletal muscle fibre is surrounded by a thin connective tissue sheath, the endomysium. A bundle of muscle fibres is called a fascicle.

It is surrounded by a connective tissue sheath called perimysium. A group of fascicles forms a ‘muscle’ that is surrounded by an epimysium (outermost connective tissue sheath). These connective tissue layers may extend beyond the muscle to form a chord-like tendon or sheet¬like aponeurosis.

A skeletal muscle fibre is a long, cylindrical, and unbranched cell. It is a multinucleated cell with many oval nuclei characteristically in the “peripheral” cytoplasm (a syncytium formed by the fusion of cells). Sarcoplasm has many myofibrils which show alternate dark and light bands. So it is called striped or striated muscle.

Smooth (unstriped and involuntary muscle): It is located in the walls of the visceral organs such as blood vessels, trachea, bronchi, stomach, intestine, excretory and genital ducts, and so this is also called ‘visceral muscle’. As cross striations are absent, it is called ‘smooth muscle. It is also found in the iris and ciliary body of the eye and in the skin as ‘arrector pili muscles that are attached to hair follicles.

Usually, smooth muscles are arranged in ‘layers’/’sheets’. A smooth muscle fibre is a spindle-shaped (fusiform), uninucleate cell. Myofibrils do not show alternate dark and light bands due to the irregular arrangement of actin and myosin fibres. They do not work under conscious control, and so they are called involuntary muscles. Smooth muscles exhibit ‘slow’ and ‘prolonged’ contractions. They may remain contracted for long periods without fatigue (show sustained involuntary contractions called ‘spasms’). The contraction of smooth muscles is under the control of the autonomous nervous system.

Cardiac (striped and involuntary) muscle: The cardiac muscle is striated like the skeletal muscle (shows sarcomeres). Cardiac muscle is found in the ‘myocardium’ of the heart of vertebrates. The cardiac muscle cells or the ‘myocardial cells’ are short, cylindrical, mononucleate, or binucleate cells whose ends branch and form junctions with other cardiac muscle cells. Each myocardial cell is joined to adjacent myocardial cells by ‘electrical synapses’ or gap junctions. They permit ‘electrical impulses’ to be conducted along the long axis of the cardiac muscle fibre. The dark lines across cardiac muscle are called intercalated discs (IDs). These discs are highly characteristic of the cardiac muscle.

Andhra Pradesh BIEAP AP Inter 1st Year Zoology Study Material Lesson 1 Diversity of Living World Textbook Questions and Answers.

AP Inter 1st Year Zoology Study Material Lesson 1 Diversity of Living World

Very Short Answer Type Questions

Question 1.
Define the term metabolism. Give any one example.
Answer:
The sum total of all the chemical reactions occurring in the bodies of organisms constitutes metabolism.
Ex: Photosynthesis is one of the metabolic processes in living organisms.

Question 2.
How do you differentiate between growth in a living organism and a non-living object?
Answer:
Growth is one of the fundamental characteristics of living beings growth in living beings is growth from the inside, whereas growth in non-living things is by the accumulation of material on the surface.

Question 3.
What is biogenesis?
Answer:
Life comes only from life is called biogenesis. Living organisms produce young ones of their kind using molecules of heredity.

Question 4.
Define the term histology. What is it otherwise called?
Answer:
Histology is the study of the microscopic structure of different tissues. It is also called Micro anatomy.

Question 5.
Distinguish between embryology and ethology.
Answer:
Embryology: It is the study of events that lead to fertilization, cleavages, early growth, and differentiation of a zygote into an embryo.
Ethology: The study of animal behaviour based on systematic observation, with special attention to physiological, ecological, and evolutionary aspects is called ethology.

Question 6.
In a given area, remains of animals that lived in the remote past are excavated for study. Which branch of science is it called?
Answer:
The branch of science Palaeontology deals with that. In a given area, remains of animals that lived in the remote past (fossilized remains) are excavated for study.

Question 7.
Zoos are tools for ‘classification’ Explain.
Answer:
Zoos are places where wild animals are taken out of their natural habitat and are placed in protected environments under human care. This enables us to learn about the animal’s external features, habits, behaviour, etc. These observations enable us to systematize the organism and position it in the animal world.

Question 8.
Where and how do we preserve skeletons of animals dry specimens etc?
Answer:
The Skeletons and dry specimens are preserved in Museums and are usually stuffed and preserved.

Question 9.
What is trinominal nomenclature? Give an example.
Answer:
The trinominal nomenclature is the extension of the binominal system of nomanclature. It permits the designation of subspecies with a three-worded name called ‘trinomen’.
Ex: Homo Sapiens Sapiens, Corvus splendns spelendns.

Question 10.
What is meant by tautonymy? Give two examples.
Answer:
The practice of naming animals or organisms, in which the generic name and species name are the same, is called Tautonymy.
Ex: Axis axis – spotted dear
Naja naja – The Indian Cobra

Question 11.
Differentiate between Protostomia and Deuterostomia.
Answer:
Protostomia (Gr. mouth first) are the organisms in which blastopore develops into the mouth.
Deuterostomia (Gr. second mouth) are the organisms in which blastopore develops into the anus, the mouth is formed later.

Question 12.
‘Echinoderms are enterocoelomates’. Comment.
Answer:
The animals of phyla Echinodermata have a true coelom, which is an ‘enterocoel’. It is formed from the archenteron.

Question 13.
What does ICZN stand for?
Answer:
ICZN stands for ‘International Code of Zoological Nomenclature which specifies the mandatory rules to be followed for the naming of animals by the International congress (ICZ) in 1898.

Question 14.
Give the names of any four protostomian phyla.
Answer:
The phylum Platyhelminthes, Nematoda, Annelida, Arthropoda, and Mollusca are the protostomian phyla.

Question 15.
Nematoda is a protostomian but not a coelomate justify the statement.
Answer:
Animals of group Nematoda are protostomian but they have no true coelom/secondary body cavity as it is not lined by mesodermal epithelial layers. Pseudocoel is a remnant of the embryonic blastocoel. Hence they are protostonian. Pseudocoelomata, but not coelomates.

Question 16.
What is ecological diversity? Mention the different types of ecological diversities.
Answer:
Diversity at a higher level of organization, i.e., at the ecosystem level is called ‘Ecological diversity.
The other ecological diversities are Alpha, Beta, and Gama diversities.

Question 17.
Define species richness.
Answer:
The more the number of species in an area (unit area) the more species richness.

Question 18.
Mention any two products of medicinal importance obtained from Nature.
Answer:
Anticancer drugs Vinblastin from the plant Vinco rosa and Digitalin from the plant for gloves are obtained from nature.

Question 19.
Invasion of an Alien species leads to the extinction of native species. Justify this with two examples.
Answer:
When alien species are introduced into a habitat, they turn invasive and establish themselves at the cost of the native species.
Ex: Nail perch introduced into lake Victoria, in east Africa led to the extinction of 200 species of Cichlid fish in the lake. The illegal introduction of exotic African catfish for aquaculture purposes in posing a threat to the native catfish.

Question 20.
List out any four sacred groves in India.
Answer:
The following are the Sacred Groves in India.

1. Khasi and Jaintia Hills – Meghalaya
2. Aravalli Hills – Rajasthan and Gujarat
3. Western Ghat region – Karnataka and Maharashtra
4. Sarguja, Bastar – Chhattisgarh
5. Chanda – Madhya Pradesh

Question 21.
Write the full form of IUCN. In which book threatened species are enlisted.
Answer:
IUCN – International Union for the Conservation of Nature and Natural Resources.
All the threatened species are enlisted in the Red Data Book Published by IUCN.

Short Answer Type Questions

Question 1.
Explain the phylogenetic system of biological classification.
Answer:
Phylogenetic classification is an evolutionary classification based on how a common ancestry was shared. Cladistic classification summarizes the ‘genetic distance’ between all species in this ‘Phylogenetic tree’. In Cladistic classification characters such as analogous characters (characters shared by a pair of organisms due to convergent evolution e.g. wings in sparrows and patagia (wing-like structures) in flying squirrels) and homologous characters (characters shared by a pair of organisms, inherited from a common ancestor e.g. wing of sparrows and finches) are taken into consideration. Ernst Haeckel introduced the method of representing Phylogeny by ‘tree’ branching diagrams.

Question 2.
Explain the hierarchy of classification.
Answer:
Human beings are not only interested in knowing more about different kinds of organisms and their diversities, but also the relationships among them. This branch of study is referred to as systematics. Systematics is the branch of science that deals with the vast diversity of life. It also reveals the trends and evolutionary relationships of different groups of organisms. These relationships establish the phylogeny of organisms. A key part of systematics is taxonomy. The taxonomic hierarchy includes seven obligate categories namely kingdom, phylum, class, order, family, genus, and species, and other intermediate categories such as subkingdom, grade, division, subdivision, subphylum, superclass, subclass, superorder, suborder, superfamily, subfamily, subspecies, etc.

Question 3.
What is meant by classification? Explain the need for classification.
Answer:
Classification is defined as the process by which anything is grouped into convenient categories based on some easily observable characteristics. It is impossible to study all living organisms. So, it is necessary to devise some means to make this possible. This process is called classification. The scientific term used for these categories is ‘TAXA’. Taxa can indicate categories at different levels, e.g. Animalia, Chordata, Mammalia, etc. represent taxa at different levels.

Hence based on characteristics, all living organisms can be classified into different taxa: This process of classification is called taxonomy. External and internal structures, along with the structure of cells, developmental processes, and ecological information of organisms are essential and they form the basis of modern taxonomic studies, Hence characterization, identification, nomenclature, and classification are the processes that are basic to taxonomy. To understand the interrelationships among the diversified animal groups, a systematic classification is necessary.

Question 4.
Define species. Explain the various aspects of ‘species’.
Answer:
Species: Species is the ‘basic unit’ of classification. Species is a Latin word meaning ‘kind’ or ‘appearance’. John Ray in his book ‘Historia Generalis Plantarum’ used the term ‘species’ and described it on the basis of common descent (origin from common ancestors) as a group of morphologically similar organisms. Linnaeus considered species, in his book ‘Systema Naturae’, as the basic unit of classification. Buffon, in his book ‘Natural History, proposed the idea of the evolution of species which is the foundation for the biological concept of evolution. This biological concept of species (dynamic nature of species) became more popular with the publication of the book “The Origin of Species” by Charles Darwin.

Buffon’s biological concept of species explains that species is an interbreeding group of similar individuals sharing the common ‘gene pool’ and producing fertile offspring. Species is considered as a group of individuals which are:

1. Reproductively isolated from the individuals of other species – a breeding unit.
2. Sharing the same ecological niche – an ecological unit.
3. Showing similarity in the karyotype – a genetic unit.
4. Having similar structure and functional characteristics – an evolutionary unit.

Question 5.
What is genetic diversity and what are the different types of genetic diversity?
Answer:
Genetic diversity is the diversity of genes within a species. A single species may show high diversity at the genetic levels over its distributional range. For e.g. Rauwolfia vomitoria, a medical plant growing in the Himalayas ranges shows great genetic variation, which might be in terms of potency and concentration of the active chemical (reserpine extracted from it is used in treating high blood pressure) that the plant produces. India has more than 50,000 different strains of rice and 1,000 varieties of mangoes. Genetic diversity increases with environmental variability and is advantageous for its survival.

Question 6.
What are the reasons for greater biodiversity in the tropics?
Answer:
Reasons for greater biodiversity in the tropics:
Reason 1: Tropical latitudes have remained relatively undisturbed for millions of years and thus had a long ‘evolutionary time’. The as long duration available in this region for speciation led to species diversification. (Note: The temperate regions were subjected to frequent glaciations in the past).

Reason 2: Tropical climates are relatively more constant and predictable than that temperate regions. A constant environment promotes niche specialization (how an organism responds, and behaves with the environment and with other organisms of its biotic community) and this leads to greater species diversity.

Reason 3: Solar energy, resources like water, etc., are available in abundance in this region. They contribute to higher productivity in terms of food production, leading to greater diversity.

Question 7.
What is the ‘evil quartet’?
Answer:
The following are the ‘four major causes (The Evil Quartet) for accelerated rates of species extinction in the world.
Habitat loss and Fragmentation: These are the most important reasons for the loss of biodiversity.

• Deforestation leads to species extinction in forests.
  e.g: tropical rainforests once covered 14% of the earth’s land surface now not more than 4%.
• Conversion of forest land to agricultural land.
  e.g: the amazon rainforest, called the lungs of our planet, harbouring innumerable species is cut and cleared to cultivate soybeans or convert to grasslands for raising beef cattle.
• Pollution enhances the degradation of habitats and threatens the survival of many species as pollutants change the quality of the environment.
• Fragmentation of habitat leads to population decline.
  e.g: mammals and birds requiring large territories and certain animals with migratory habits are badly affected.

Question 8.
Explain in brief ‘Biodiversity Hot Spots’.
Answer:
Biodiversity hot spots: A Biodiversity hot spot is a Biogeographic Region that is both a significant reservoir of biodiversity and is threatened with destruction.
The concept of biodiversity originated from Norman Myers. There ate about 34 biodiversity hot spots in the world. As these regions are threatened by destruction habitat loss is accelerated.
e.g.: (I) the Western Ghats and Srilanka
(II) Indo Burma
(III) Himalayas in India.

Ecologically unique and biodiversity-rich regions are legally protected as in

• Biosphere Reserves – 14
• National Parks – 90
• Sanctuaries – 448

Biosphere Reserves: An area that is set aside, minimally disturbed for the conservation of the resources of the biosphere is the ‘Biosphere reserve. The latest biosphere reserve (17th biosphere reserve in India) is Seshachalam hills.

National Parks: A National Park is a natural habitat strictly reserved for the protection of natural life. National Parks, across the country, offer a fascinating diversity of terrain, flora, and fauna. Some important National Parks in India are – Jim Corbett National Park (the first National Park in India located in Uttarakhand), Kaziranga National Park (Assam), Kasu Brahmananda Reddy National Park, MahavirHarinaVanasthali National Park (AP). Keoladeo Ghana National Park (Rajasthan), etc.

Sanctuaries: Specific endangered faunal species are well protected in wildlife sanctuaries which permits eco-tourism (as long as animal life is undisturbed). Some, important Sanctuaries in India (AP) include-Koringa Sanctuary, Eturnagaram Sanctuary, and Papikondalu Sanctuary.

Question 9.
Explain the ‘Rivet Popper’ hypothesis.
Answer:
What if we lose a few species? Will it affect man’s life? Paul Ehrlich experiments Rivet popper, hypothesis, taking an aeroplane as an ecosystem, explains how the removal of one by one ‘rivets’ (species of an ecosystem) of various parts can slowly damage the plane (ecosystem)-shows how important a ‘species’ is in the overall functioning of an ecosystem. Removing a rivet from a seat or some other relatively minor important parts may not damage the plane, but the removal of a rivet from a part supporting the wing can result in a crash. Likewise, the removal of a ‘critical species’ may affect the entire community and thus the entire ecosystem.

Question 10.
Write short notes on In-situ conservation.
Answer:
In-situ conservation (On-site conservation): In-situ conservation is the process of protecting an animal species in its natural habitat. The benefit is that it maintains recovering populations in the surrounding where they have developed their distinctive properties. Conservationists identified certain regions by the name ‘Biodiversity hot spots’ for maximum protection as they are characterized by very high levels of species richness & high degree of endemism. By definition ‘A biodiversity hot spot’ is a ‘Biogeographic Region’ with a significant reservoir of biodiversity that is under threat of extinction from humans. They are Earth’s biologically ‘richest’ and ‘most threatened’ Terrestrial Ecoregions.