AP Inter 1st Year Botany Study Material Chapter 6 Modes of Reproduction

Andhra Pradesh BIEAP AP Inter 1st Year Botany Study Material 6th Lesson Modes of Reproduction Textbook Questions and Answers.

AP Inter 1st Year Botany Study Material 6th Lesson Modes of Reproduction

Very Short Answer Questions

Question 1.
What is the dominant phase in the life cycle of an angiosperm?
Answer:
The dominant phase in the life cycle of an angiosperm is Diploid sporophyte.

Question 2.
What is meant by heterospory? Mention the two types of spores developed in an angiospermic plant?
Answer:
Heterospory means the formation of more than one type of spores. Microspores and Megaspores are developed in an angiospermic plant.

Question 3.
Mention the modes of reproduction in Algae and Fungi.
Answer:
In Algae (Chlamydomonas) Reproduction is by motile zoospores and by fragmentation. In fungi (Rhizopus), reproduction is by non motile spores produced in the sporangia and by fragmentation.

Question 4.
How do Liver worts reproduce vegetatively?
Answer:
Reproduction in liver worts is by specialized structure via fragmentation called ‘Gemmae’.

Question 5.
Mention any two characteristics of bacteria and yeast that enable them to reproduce asexually.
Answer:

1. Rapid Growth.
2. The offsprings produced asexually are not only identical to one another but are also exact copies of their parent.

Question 6.
Why do we refer to offspring formed by asexual method of reproduction as clones?
Answer:
There is no involvement of sex organs. Hence the offsprings produced by Asexual Reproduction are called clones.

Question 7.
Between an annual and a perinneal plant, which one has a shorter juvenile phase? Give one reason.
Answer:
Annual have a shorter Juvenile phase because they show clear cut vegetative reproductive and senescent phases.

Question 8.
Rearrange the following events of sexual reproduction in the sequence in which they occur in a flowering plant : embryogenesis, fertilisation, gametogenesis, pollination.
Answer:
Gametogenesis, Pollination, Fertilisation, Embryogenesis.

Question 9.
Is there a relationship between the size of an organism and its life span?
Answer:
No relationship between the size of an organism and its life span.

Question 10.
Give reasons as to why cell division can or cannot be a type of reproduction in multicellular organisms.
Answer:
In Multicellular organisms, cell division cannot be a type of Reproduction because, Reproduction in them takes place by vegetative Asexual and Sexual Methods.

Question 11.
Which of the following are monoecious and dioecious organisms :
a) Date palm b) Coconut c) Chara d) Marchantia.
Answer:
a) Date Palm – Dioecious
b) oconut – Monoecious
c) Chara – Monoecious
d) Marchantia – Dioecious

Question 12.
Match the following given in Column A with the vegetative propagules given in Column B.

Column A	Column B
i) Bryophyiium	a. Offset
ii) Agave	b. Eyes
iii) Potato	c. leaf buds
iv) Water hyacinth	d. fragmentation
v) Chara	e. Sucker
vi) Mentha	f. bulbils

Answer:

Column A	Column B
i) Bryophyiium	Leaf buds
ii) Agave	Bulbils
iii) Potato	Eyes
iv) Water hyacinth	Offsets
v) Chara	Fragmentation
vi) Mentha	Suckers

Question 13.
What do the following parts of a flower develop into after fertilisation?
a) Ovary b) Stamens c) Ovules d) Calyx.
Answer:
After fertilisation.
a) The ovary develops into a fruit
b) Stamens – wither away
c) Ovules – develop into seeds
d) Calyx – Wither away or persistent in some species (Capsicum, Solanum).

Question 14.
Define vivipary with an example.
Answer:
In Mangrooves, the seeds germinate while still attached to the mother plant is called vivipary”.
Ex : Rhizophora.

Short Answer Type Questions

Question 1.
Describe briefly the gametogeneis with suitable example.
(Or)
Write a brief account on gametogenesis with examples.
Answer:
Gametogenesis is a process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. They are two types.
1) Homogametogenis :
In some algae like cladophora the two gametes are so similar in appearance that it is not possible to categorize them into male and female gametes. They are called hormogametes and process is called homogametogenesis.

2) Heterogametogenesis :
In a majority of sexual reproducing organisms the gametes produced are of two morphologically distinct types. In such organisms, the male gamete is called the authorized and the female gamete is called the egg.
Ex : Funaria, Cycas, Pteris.

Question 2.
Give an account of sexuality in organisms.
(Or)
Describe Sexuality in living organisms.
Answer:
Sexuality involves formation and fusion of the male and female gametes, either by the same individual or by different individuals of the opposite sex. Sexuality in plants is varied, particularly in angiosperms, due to the production of diverse types of flowers. Plants are defined as monoecious and dioecious.

Monoecious :
If the male and female flowers may be present ont he same individual such plants are called as monoecious plants.
Ex : Cucurbita and coconuts.

Dioecious :
If the male and female flowers may be present on the separate individual such plants are called Dioecious plants.
Ex : Papaya and date palm.

In Angiosperms based on sexualty flowers divided into two types. They are :
1) Staminate flowers :
The flowers bearing stamens are called as staminate flowers.

2) Pistillate flowers :
The flowers bearing pistil or Gynoecium are called as pistillate flowers.

Question 3.
In haploid organisms that undergo sexual reproduction, name the stage in the lifecycle where meiosis occurs. Give reasons for your answer.
Answer:
Zygote :
It goes through Meiosis, it develops into spore or some other in structure. Meiosis produces 4 cells from each zygote and go through Mitosis to become an organism. Then it reproduce a either by Asexual method or by sexual method. It produce gametes, which fuse together, resulting in the formation of zygote. It is called Zygotic life cycle.
Ex : Volvox, Ocologonium.

Question 4.
The number of taxa exhibiting asexual reproduction is drastically reduced in higher plants (angiosperms) when compared to the lower groups of paints. Analyse the possible reasons for this situation.
Answer:
Reproduction is defined as a biological process in which an organism gives rise to young ones similar to itself. Reproduction becomes a vital process without which species cannot survive for long days. Each individual leaves its progeny by asexual or sexual means. Sexual mode of Reproduction enables creation of new variants; So that survival advantage is enhanced.

The plants obtained through asexual reproduction produce offsprings which are identical to each other and to their parent They cannot withstand in different environmental condition. Thats why, the number of taxa exhibiting asexual reproduction is drastically reduced in Higher plants, where as in lower groups of plants. Asexual Reproduction results in formation of large number of spores or cinidia which germinate, increase their Race.

Question 5.
Is it possible to consider vegetative propagation observed in plants like bryophyllum, water hyacinth and ginger as a type of asexual reproduction? Give two/three reasons.
Answer:
In Bryophyllum, buds formed on Knotches of the leaf develop into new Individuals in which no involvement of two parents. So this process is called asexual mode of Reproduction.

In water hyacinth, a weed is formed growing wherever there is stanoling water. It can propagate vegetatively at a phenomenal rate and spread all over the water body in a short period of time. So it is also called asexual mode of Reproduction.

In Ginger, a underground stem modification nodes and internodes are present. At each node, an auxiliary bud is present which develops into new plant, so treated as Asexual Reproduction.

Question 6.
“Fertilisation is not an obligatory event for fruit production in certain plants”. Explain the statement.
Answer:
Production of fruits without fertilisation of ovules is called parthenocarpy. It is common in Banana, grapes, Cucurbita, pollination or other stimulation is required for parthenocarpy called stimulative parthenocarpy. Plants that do not require pollution or simulation to produce parthenocarpic fruits have vegetative parthenocarpy. Seedless cucumbers, watermelons.

Panthenocarp is also desirable in fruit crops that may be difficult to pollinate or fertilize, such as tomato and summer squash. If plant harmones, gibberellin, auxin and cytokinins are sprayed on flowers, they induce parthenocarpy called artificial parthenocarpy. It is also induced by natural agents like low light cool conditions, to produce seedless fruits. Parthenocarpic fruits are advantageous because they are bigger in size, flavour is more :

1. Easier to eat with less waste.
2. Shelf like longer due to reduced ethylene generated by seeds.
3. Seedless fruits have higher total soluble contents so fertilization is not an obligatory event in fruit production.

Question 7.
List the changes observed in angiosperm flower subsequent to pollination and fertilisation.
Answer:
Event in sexual Reproduction after the formation of zygote are called post fertilisation events. They are

1. Calyx, Corolla, Stamens, style and stigma wither away.
2. Ovary develops into fruit.
3. Ovules develop into seeds.
4. The zygote develops into an embryo.
5. Primary endosperm nucleus develops into endosperm which provides nourishment to the developing embryo.
6. The synergid and antipodals degenerate after fertilization.
7. Funicle of the ovule changes into stalk of the seed.
8. Outer antegumentofthe ovule changes into testa (outer seed coat). Inner integument changes into Inner seed coat (Tegmen).
9. Micropyle changes into seed pore.
10. Hilum changes into scar of the seed.

Question 8.
Suggest a possible explanation why the seeds in a pea pod are arranged in a row where as the tomato are scattered in the juicy pulp.
Answer:
In Pea :
Fruit is legume. It is a dry dehiscent fruit developed from Monocarpellary, unilocular and half superior ovary. At maturity, the fruit splits along the dorsal and ventral sutures and discharge its seeds. More over, the ovules are arranged in Marginal placentation (i.e.,) placentation axis is present along the Margin of Ventral suture. Thats why seeds are arranged in a row in legume (Pea) pod.

In tomato, the fruit is Bery. It is a fleshy fruit develop from superior or Inferior ovary. In this, the margins of the carpels grow inwards to the centre of the ovary forming locules. So that ovules are arranged in a divided central column. Thats why the seeds are scattered in the Juicy pulp which are dispersed after the delay of pulp. ‘

Question 9.
Justify the statement “Vegetative reproduction is also a type of asexual “reproduction”.
Answer:
In multicellular or colonjal forms of algae, moulds and mushrooms, the body may break into smaller fragments. Each fragment thus formed develops into a mature Individual. This process is called Fragmentation. Some plants have specialized structures for reproduction called Gemmae (in liverworts).

In flowering plants, the units of vegetative propagation such as Runners, Stolons, Suckers, Offset, Rhizome, Corm, Stem tuber, Bulb, Bulbil, Reproductive leaves, are cell capable of giving rise to new offsprings. These structures are called vegetative propagules. In all these plant. No involvement of sex organs takes place. So vegetative reproduction is also a asexual Reproduction and formed progeny are called clones.

Question 10.
Define : a) Juvenile phase, b) Reproductive phase.
Answer:
a) All organisms have to reach a certain stage of growth and Maturity in their life, before they can reproduce sexually and this storage is known as Juvenile stage or vegetative pahse.

b) The stage which occurs after the Juvenile stage, which can be seen easily in the higher plants when they came to flower is called Reproductive phase. In this, reproduction occurs either by asexual or by sexual means produce offsprings.

Question 11.
Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?
Answer:

Asexual Reproduction	Sexual Reproduction
1. Single parent is involved.	1. Two parents take part in reproduction.
2. Offspring are genetically identical to each other and to their parent.	2. Variation occurs in offsprings due to Genetic recombinations.
3. No fertilisation.	3. Fertilisation takes place.
4. No gametes are formed.	4. Gametes are involved.
5. No mixing of hereditary material.	5. Mixing of hereditary material.

In multicellular or colonial forms of algae, moulds and mushrooms, the body may break into smaller fragments. Each fragment thus formed develops into a mature Individual. This process is called Fragmentation. Some plants have specialized structures for reproduction called Gemmae (in liverworts). In flowering plants, the units of vegetative propagation such as Runners, Stolons, Suckers, Offsets, Rhizome, Corm, Stem tuber. Bulb, Bulbil, Reproductive leaves, are capable of giving rise to new offsprings. These structures are called vegetative propagules. In all these plants, sex organs are not involved. So vegetative reproduction is also a asexual Reproduction.

Question 12.
Identify each part in a flowering plant and write whether it is haploid (n) or diploid (2n).
a) Ovary —– b) Anther —– c) Egg —– d) Pollen —– e) Male gamete —– f) Zygote
Answer:
a) Ovary – Diploid (2n)
b) Anther – Diploid (2n)
c) Egg – Haploid (n)
d) Pollen – Haploid (n)
e) Male gamete – Haploid (n)
f) Zygote – Diploid (2n)

Question 13.
Give a brief account on the phases of the life cycle of an angiosperm plant.
Answer:
In the life cycle of an angiospermic plant, two phases occur alternately. They are
A) Sporophytic phase :
It is diploid (2n) and dominant phase of the life cycle. It is developed from the zygote. Reproductive organs develop on this plant.

B) Gametophytic phase :
It is haploid (n). It is derived from a spore which is a product of meiotic division of spore mother cell. In angiosperms, microspore mother cells and megaspore mother cells are present. Microspore mother cells develop in an anther while megaspore mother cells develop from the nucleus of the ovule. Each of these cells in turn gives microspores and megaspores after meiotic division.

These micro and megaspores develop into male and female gametophytes respectively. The male gametophyte gives male gametes & the female gametophyte forms the egg cell. Male and female gametes (Egg) fuse to form a diploid zygote which develops into embryo in the seed. When the seed germinates, the embryo develops into sporophytic plant.

Long Answer Type Questions

Question 1.
Enumerate the differences between asexual and sexual reproduction. Describe the types of asexual reproduction exhibited by unicellular organisms.
Answer:

Asexual Reproduction	Sexual Reproduction
1. Single parent is involved.	1. Two parents take part in reproduction.
2. Offspring are genetically identical to each other and to their parent.	2. Variation occurs in offsprings due to Genetic recombinations.
3. No fertilisation.	3. Fertilisation takes place.
4. No gametes are formed.	4. Gametes are involved.
5. No mixing of hereditary material.	5. Mixing of hereditary material.

Asexual Reproduction in Unicellular organisms :
In Protista and Monereans, the organism or the parent cell divides into two to give rise to hew individuals. Many single celled organisms reproduce by binary fission, where a cell divides into two halves and each rapidly grows into an adult. (Euglena, Bacteria). In yeast, asexual reproduction takes place by budding, where the division is unequal. Small buds are produced that remain attached initially to the parent cell which, eventually get separated and mature into new yeast organisms.

Question 2.
Describe the post – fertilisation changes in a flower.
Answer:
After fertilisation many changes takes place in the embryo sac ovule, ovary and flower. These changes are called post fertilisation changes. The sepals, petals, stamens, styles and stigmas fall off. Ovary stores food materials and develops into a fruit. The fertilized ovules develop into seeds. The various changes that occur in the ovule are as follows :

The parts of ovule and embryo sac	Changes occurring after fertilization
1. Funiculus	Stalk of the seed
2. Outer integument	Testa (outer seed coat)
3. Inner integument	Tegmen (inner seed coat)
4. Micropyle	Seed pore
5. Zygote	Embryo
6. Synergids	Degenerate
7. Antipodals	Degenerate
8. Primary endosperm nucleus	Endosperm
9. Hilum	Scar, of the seed

Endosperm :
In majority of angiosperms, endosperm is triploid and formed after fertilisation. In gymnosperms, endosperm is haploid and formed from female gametophyte before fertilisation.

In certain plants, the developing embryo utilises the endosperm completely. The seed contains only embryo. Endosperm is absent. Such seeds are called the non-endospermic seeds or ex-albuminous seeds.
E.g. : Dolichos, Cicer, capsella etc.

In certain plants, the developing embryo utilises the endosperm partially and the seed contains some amount of endosperm. Such seeds are called the endospermic seeds at albuminous seeds.
E.g. : Ricinus, Datura, Cocos etc.

In members of Orchidaceae endosperm is not formed (Podestamaceae).

Perisperm :
As the embryo and endosperm are developing in the embryo sac, this embryosac grows by absorbing the nutrients from the nucellus. Hence Nucellus gets depleted when the seed reaches maturity. But in some seeds, some amount of nucellus is left out called perisperm.
E.g. : Seeds of Piperaceae, Nymphaeaceae, Coffee seeds etc.

Additional Question & Answer

Question 1.
Although sexual reproduction is long drawn, energy-intensive complex form of reproduction, many groups of organisms in kingdom plantae prefer this mode of reproduction. Give atleast three reasons for this.
Answer:
Sexual reproduction is a long drawn, energy Intensive, Complex and slow process as compared to asexual reproduction but Mung organisms in kingdom plantae prefer sexual reproduction because,

1. The fusion of Male and female gametes results in offspring that are not identical to the parents or amongst themselves.
2. Sexual reproduction gives rise to more viable variations as compared with asexual reproduction. These variations further helps plant to survive in different climatic conditions.
3. Sexual reproduction may prove advantageous in plant defense.
4. Seeds produced by sexual reproduction can be dispersed in more locations and grow in more favourable environments efficiently.
5. Seed dormancy allows the plant to survive until bad environmental conditions are reversed.

Intext Questions

Question 1.
Why is reproduction essential for organisms?
Answer:
Reproduction is a vital process without which species can not survive for long. It enables the continuity of species, generation on after generation.

Question 2.
Which is a better mode of reproduction sexual or asexual? Why?
Answer:
Sexual reproduction is better mode of reproduction because it enables creation of new variants. So that survival advantage is enhanced.

Question 3.
Why is the offspring formed by asexual reproduction referred to as clone?
Answer:
In Asexual reproduction, a single parent is capable of producing offsprings. As a result, the offspring produced are not ony identical to one another but are also exact copies of their parent so referred to as clones.

Question 4.
How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?
Answer:
The progeny formed from asexual reproduction are identical to one another and also exact copies of their parent. Their survival chance in different environments is low.

The progeny obtained from sexual reproduction are not identical to the parents. So their survival chance is enhanced. ‘

Question 5.
What is vegetative propagation? Give two suitable examples.
Answer:
It is a form of asexual reproduction in plants, in which multicellular structures become detached from the parent plant and develop into new individuals that are genetically identical to the parent plant.
Ex : Bryophyllum, Zinger, Turmeric, Colacasia, Gemmae (Liver worts)

Question 6.
Higher organisms have resorted to sexual reproduction in spite of its complexity. Why?
Answer:
Sexual reproduction varies the gene pool; as all offspring are slightly different from the parents and their ability to adapt over time is good.

Question 7.
Explain why meiosis and gametogenesis are always interlinked?
Answer:
In Angiosperms, Meiosis occurs in Microspore mother cells and Megaspore mother cells, without which male and female gametes are not formed.

Question 8.
Define external fertilisation. Mention its disadvantages.
Answer:
In Aquatic organisms, syngamy occurs outside the body of the organism. This type of gametic fusion is called external fertilisation. In this method, zygote is formed in the external medium (water).

Question 9.
Differentiate between a zoospore and a zygote.
Answer:

Zoospore	Zygote
It is a motile asexual spore that uses a flagellum for locomotion. They are found in Algae, Bacteria fungi.	It is a diploid cell formed by the fusion of one male gamete and one female gamete.

Activity :

Question 10.
Examine a few flowers of any cucurbit plant and try to identify the staminate and pistillate flowers. Do you know any other plant that bears unisexual flowers?
Answer:
In Cucurbitaceae family – flowers are unisexual rarely bisexual in Schizo pepon.

In All unisexual flowers, In Luffa cylindrica and Thladiantha – stamens with Monothecus anthers are present.

In Citrullus, Legenaria, Cucumis (all unisexual) stamens are three, one with Monothecus (all unisexual) stamens are three, one with Monothecus and two with Dithecous anthers. In female flowers, stamens are represented by staminodes. In Male flowers, Gynoecium is represented by Pistiollodes.

Question 11.
What is a bisexual flower? Collect five bisexual flowers from your neighbourhood and with the help of your teacher find out their common and scientific names.
Answer:
The flower with both Androecium and Gynoecium is called bisexual flower.

1. Hibiscus rosa – sinensis – shoe flower
2. Gloriosa superba – Adavinabhi
3. Datura metal – Thorn apple
4. Dolichos lab – lab – Bean
5. Solanum melongena – Brinjal