Date : 01-12-2023 STD 12 Science Biology Total Marks : 190

ch 1 revision paper

SECTION A

* Choose The Right Answer From The Given Options.[1 Marks Each] [20]
1. Why is vivipary an undesirable character for annual crop plants?
(A) It reduces the vigour of the plant.
(B) It adversely affects the fertility of the plant.
(C) The seeds exhibit long dormancy.
(D) The seeds cannot be stored under normal conditions for the next season.

Ans. :
d. The seeds cannot be stored under normal conditions for the next season.
2. Asexual reproduction takes place through budding in:
(A) Amoeba (B) Yeast (C) Plasmodium (D) Leishmania

Ans. :
b. Yeast
Explanation:
Saccharomyces cerevisiae commonly known as yeast, reproduces both asexually as
well as sexually.
Yeast reproduce asexually through a process known as budding.

3. Ootheca of cockroach has .................. fertilized eggs.

(A) 6 (B) 8 (C) 16 (D) 24

Ans. :
c. 16
Explanation:
Cockroaches are oviparous.
The egg hatches at specific conditions to give birth to young ones.
The eggs are carried by the mother cockroach around in a sac called an ootheca,
which is attached to her abdomen.
The number of eggs in each ootheca are about 16 and varies from species to
species.
Many female cockroaches drop or hide their ootheca shortly before the eggs are
ready to hatch.
Others continue to carry the hatching eggs and care for their young after they are
born.
But regardless of how long the mother and her eggs stay together the ootheca.

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4. What is rhizome?
(A) Underground stems with buds.
(B) Stems running above and along the ground.
(C) Spores.
(D) The result of sexual reproduction.

Ans. :
a. Underground stems with buds.
Explanation:
Vegetative propagation or vegetative reproduction is the growth and development of
the plant by asexual means.
A. Rhizome is a vegetative plant structure which arises from the modified
stem that grows horizontally along the underground or ground surface
with buds.
B. This is known as Runners. They originate from existing stem and have
horizontal growth at or just below the soil surface.
C. Spores are the agents for asexual reproduction in nonflowering plants,
bacteria, fungi, and algae.
D. Sexual reproduction is the production of gamete and fertilization.
E. Stems with woody trunk and are underground.
5. In protists and monerans, asexual reproduction occurs by:
(A) Budding. (B) Binary fission. (C) Conidia. (D) Multiple fission.
Ans. :
b. Binary fission.
6. External fertilisation occurs in majority of:
(A) Algae (B) Mosses (C) Liverworts (D) Fungi
Ans. :
a. Algae
7. Which of the following statements is true of yeast?
(A) The cell divides by binary fission. One of them develops into a bud.
(B) The cell produces conidia, which develop into a bud.
(C) The cell divides unequally. The smaller cell develops into a bud.
(D) None of these.
Ans. :
c. The cell divides unequally. The smaller cell develops into a bud.
8. A multicellular, filamentous alga exhibits a type of sexual life cycle in which the meiotic
division occurs after the formation of zygote. The adult filament of this alga has:
(A) haploid vegetative cells and diploid gametangia.
(B) diploid vegetative cells and diploid gametangia.
(C) diploid vegetative cells and haploid gametangia.
(D) haploid vegetative cells and haploid gametangia.
Ans. :
d. haploid vegetative cells and haploid gametangia.

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 Adult filament of a multicellular, filamentous alga have haplontic life cycle in which
the meiotic division occurs after the formation of zygote. So, the filament of this alga
have haploid vegetative cells and haploid gametangia.

9. Tubers help in the vegetative reproduction in:

(A) Tomato (B) Potato (C) Onion (D) Garlic
Ans. :
b. Potato
Explanation:
In potato, underground stem stores starch and becomes fleshy tuber.
The eyes of tuber represent nodes and adventitious buds are present in their axil.
The buds may germinate to produce new plantlets.
Onion and garlic also show stem modifications but in these plants stem is modified to
bulb having fleshy leaves.
Tomato reproduces sexually and produces berry fruit.

10. Vegetative propagation in Pistia occurs by:

(A) Sucker (B) Runner (C) Offset (D) Rhizome

Ans. :
c. Offset
11. In honey bees, males (drones) are formed from:
(A) Unfertilized eggs (B) Fertilized eggs
(C) Embryo (D) None of the above

Ans. :
a. Unfertilized eggs
Explanation:
The male honey bees are called drones.
Drones are formed from the unfertilized eggs i.e. haploid eggs of the queen bee.
Fertilized eggs form queens and female workers.
Drones are meant for mating with the queen bee and soon die after mating.

12. In some species, parthenogenesis may alternate with sexual reproduction. This process
is called as:
(A) Complete parthenogenesis. (B) Incomplete or cyclic parthenogenesis.
(C) Both A and B. (D) Alternation generation.

Ans. :
b. Incomplete or cyclic parthenogenesis.
Explanation:
Incomplete parthenogenesis or cyclic parthenogenesis is a process where sexual
generation alternates with parthenogenesic generation.
For example, in bees and wasps, some eggs develop without fertilization and
produce males, while those eggs that are fertilized developed into females.

13. ....................... is a common method of multiplication of Yeast and Hydra.

(A) Budding (B) Spore formation

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 (C) Vegetative propagation (D) Segmentation

Ans. :
a. Budding
Explanation:
Budding is a form of asexual reproduction in which a new organism develop from an
outgrowth or bud due to cell division at one particular site.
In Hydra, a bud develops as outgrowth due to repeated cell division at a particular
site.
Yeast also splits via budding and it results in a 'mother' and a smaller 'daughter' cell.

14. Animals who give birth to young ones are:

(A) Oviparous (B) Viviparous (C) Ovoviviparous (D) All of the above

Ans. :
b. Viviparous
Explanation:
Animals giving birth to young ones are called viviparous animals.
The egg of these animals typically contains less yolk insufficient to support the
development of the zygote into an embryo.
Hence, development proceeds inside the body of the female animal, and the fully
developed embryo is delivered.
Oviparous animals lay eggs.
Their egg typically has more amount of yolk and can support the development of the
zygote into an embryo outside the body of the mother.
Ovoviviparous animals lay eggs and develop the eggs inside the mother's body.

15. Offspring formed by sexual reproduction exhibit more variation than those formed by
Asexual reproduction because:
(A) Genetic material comes from parents of two different species.
(B) Greater amount of DNA is involved in sexual reproduction.
(C) Gametes of parents have qualitatively different genetic composition.
(D) Sexual reproduction is a lengthy process.

Ans. :
c. Gametes of parents have qualitatively different genetic composition.
16. Identify the correct sequence of events:
(A) Gametogenesis → Syngamy → Embryogenesis → Zygote.
(B) Gametogenesis → Zygote → Syngamy → Embryogenesis.
(C) Gametogenesis → Embryogenesis Zygote → Syngamy.
(D) Gametogenesis → Syngamy → Zygote → Embryogenesis.

Ans. :
d. Gametogenesis → Syngamy → Zygote → Embryogenesis.
17. Which ot the following has the longest life span?
(A) Butterfly (B) Crocodile (C) Parrot (D) Tortoise

Ans. :

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 d. Tortoise
18. In oogamy, fertilization involves:
(A) A large non - motile female gamete and a small non-motile male gamete.
(B) Large motile female gamete and a small non-motile male gamete.
(C) A small non - motile female gamete and a large motile male gamete.
(D) A large non - motile female gamete and a small motile male gamete.

Ans. :
d. A large non - motile female gamete and a small motile male gamete.
Explanation:
Oogamy is the common type of heterogamaous sexual reproduction in which the
female gamete or egg cell is non-motile and significantly larger than the male
gamete.
The male gametes on the other hand are motile spermatozoa that compete for
fertilizing the non-motile egg.
Oogamy occurs in both plant and animals but also found in some protists.

19. Which of the following is a post-fertilisation event in flowering plants?

(A) Transfer of pollen grains. (B) Embryo development.
(C) Formation of flower. (D) Formation of pollen grains.

Ans. :
b. Embryo development.

20. Reptile and bird eggs are:

(A) Macrolecithal (B) Oligolecithal (C) Mesolecithal (D) Alecithal
Ans. :
a. Macrolecithal
Explanation:
Reptiles and birds are terrestrial animals.
They lay large yolk-rich eggs which are covered with a porous shell.
As the eggs are rich in yolk they can support the development of an embryo.
Hence, embryogenesis occurs outside the body of the animal inside the egg.
Such yolk-rich eggs are called as macrolecithal eggs.

* Answer The Following Questions In One Sentence.[1 Marks Each] [20]

21. Mention the unique flowering phenomenon exhibited by Strobilanthus kunthiana
(neelakuranaji).

Ans. : It flowers once in 12 years.

22. In the whiptail lizards only females are born generation after generation. There are no
males. How is this possible?

Ans. : It indicates that the females reproduce parthenogenetically i.e., s develop into the
new female individuals without fertilization and hence, there are no males.

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23. Although potato tuber is an underground part, it is considered as a stem. Give two
reasons.

Ans. :
The tuber has nodes and internodes.

Leafy shoots appear from the nodes.

24. Mention the unique feature with respect to flowering and fruiting in bamboo species.

Ans. : Bamboo flowers only once in its lifetime 50-100 years. lt produces large number of
fruits and dies.

25. Name two plants having haploid body.

Ans. : Algae and fungi.

26. Give the name of any two hermaphrodite animals.

Ans. : Earthworm and tapeworm.

27. How is it possible in Oxalis and Viola plants to produce assured seed-sets even in the
absence of pollinators?

Ans. : By presence of cleistogamous flowers.

28. How do spores help in survival under unfavourable conditions?

Ans. : Soores are covered by a thick wall which prevents them fiom desiccation under
unfavourable conditions.

29. Name one plant which propagates by the means of its leaf.

Ans. : Bryophyllum.
30. Suggest a possible explanation why the seeds in a pea are arranged in a row, whereas
those in tomato are scattered in the juicy pulp.

Ans. : The ovary of pea plant is monocarpellary and the ovules are arranged along one
margin whereas in tomato the ovary is tricarpellary with axile placentation.

31. At what stage does the meiosis occur in an organism exhibiting haploidic life cycle and
mention the fate of the products thus produced.

Ans. : Meiosis occurs at the zygote stage in an organism exhibiting haploidic life cycle.
Thus, the product formed will be haploid spores.

32. What marks the end of reproductive phase?

Ans. : Senescence marks the end of reproductive phase.

33. All organisms have to pass through a particular phase before they can reproduce
sexually. What do we call this phase?

Ans. : Reproduction phase.

34. Which ones of the following organisms exhibit binary fission?
Bacillus, Penicillium, Yeast, Amvebu.

Ans. : Bacillus and Amoeba.

35. Name two organisms where both male and female gametes are motile.

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 Ans. : Algae and fungi.
36. What marks the end of juvenile phase in flowering plants?

Ans. : Initiation of floral buds marks the end of juvenile phase in flowering plants.
37. Give an example of an animal that exhibits oestrous cycle.

Ans. : Cows/ Sheep/ Rats/ Dogs/ Deers/ Tiger.

38. Which of the following statements is true for Bryophyllum?
i. Germinating bud appears from the eye of the stem tuber.
ii. Germinating bud appears from the node of the rhizome.
iii. Germinating bud appears from the notch at the leaf margin.

Ans. : Statement (iii) is true.

In Bryophyllum, germinating bud appears from the notch at the leaf margin which gets
detached and develop into new plants.

39. Name the types of life-cycle in which the zygote undergoes mitosis.

Ans. : Haplo-diplontic life cycle and diplontic life cycle.

40. Name the mode of reproduction that helps in producing genetically identical offspring.

Ans. : Asexual reproduction.

SECTION B

* Given Section consists of questions of 2 marks each. [40]

1. Why are offspring of oviparous animals at a greater risk as compared to offspring of
viviparous animals?

Ans. : The offsprings of oviparous animals are at a greater risk because they develop
outside the female body and are exposed to various environmental conditions and
predator threat whereas in viviparous animals, young ones develop inside the female
body, which ensures proper embryonic care and protection.

2. i. Why do organisms like algae and fungi shift from asexual mode of
reproduction to sexual mode?
ii. What is juvenile phase in organisms?

Ans. :
i. Algae and fungi shift to sexual mode of reproduction for the following
reasons:
a. They do so just before the onset of adverse conditions as an adaptation,
because the zygote formed as a result of sexual reproduction develops a
thick wall that protects the zygote from desiccation and mechanical injuries;
hence, the zygote is able to tide over the unfavourable conditions and
germinate at the return of favourable conditions.
b. Since sexual reproduction brings in genetic variation(s), at least some
variants will be able to survive, in case of an adverse change in the
environmental conditions.
ii. Juvenile phase is the period of growth of an organism from birth till attaining
reproductive maturity.
3.

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 How does the floral pattern of Mediterranean orchid Ophrys guarantee cross
pollination?

Ans. : The orchid bears flowers which resemble the female wasp in colour, smell, as well as
appearance. The male pollinators mistake them as their female counterparts.
Therefore, in the process of their pseudocopulation they pollinate the flower.

4. Why is it difficult to get rid of water hyacinth' from a water body? Name one abiotic
component and one biotic component of the ecosystem that gets affected by its spread
in the water body.

Ans. :
It is difficult to get rid of them because they propagate vegetatively at a rate
faster than we could remove them.
It drains oxygen from the water.

It leads to fish mortality, i.e. death of fishes.

5. Match the asexual reproductive structures in Column I with the organisms in Column II.
S.No. Column I S.No. Column II
A. Conidia i. Chlamydomonas
B. Gemmules ii. Hydra
C. Zoospores iii. Penicillium
D. Buds iv. Sponges
v. Banana

Ans. :
S.No. Column I S.No. Column II
A. Conidia iii. Penicillium
B. Gemmules iv. Sponges
C. Zoospores i. Chlamydomonas
D. Buds ii. Hydra

6. Both coconut palm and date palm produce staminate flowers. One is monoecious and
the other is dioecious. Write the difference.

Ans. :
Coconut palm is monoecious. It bears staminate (male) and pistillate (female)
flowers on the same plant.
Date palm is dioecious. It bears exclusively staminate flowers on one plant and
pistillate flowers on another plant.
7. The number of taxa exhibiting asexual reproduction is drastically reduced in higher
plants (angiosperms) and higher animals (vertebrates) as compared with lower groups
of plants and animals. Analyse the possible reasons for this situation.

Ans. : Both angiosperms and vertebrates have a more complex structural organisation.
They have evolved very efficient mechanism of sexual reproduction. Since asexual
reproduction does not create new genetic pools in the offspring and consequently
hampers their adapability to external conditions, these groups have resorted to
reproduction by the sexual method.

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 8. Why are papaya and date palm plants said to be dioecious whereas cucurbits and
coconut palms monoecious, in spite of all of them bearing unisexual flowers?

Ans. : Papaya and date palm plants are dioecious, because male and female flowers are
present on different plants, that is each plant is either male or female.
Cucurbits and coconut palms are monoecious, because male and female flowers are
present on the same plant.

9. Angiosperms bearing unisexual flowers are said to be either monoecious or dioecious.

Explain with the help of one example each.

Ans. : Monoecious Angiosperms:

Plants bear both male and female unisexual flowers on the same plant
e.g. Cucurbits/coconut/maize.
Dioecious Angisperms- plants bear either male or female unisexual flowers on different
plants
e.g. Papaya/date palms.

10. Give one example each of a fungus, which reproduces by:

i. Budding.
ii. Conidia.

Ans. :
i. Yeast.
ii. Penicillium.
11. A moss plant Produces a large number of antherozoids but relatively a few egg cells.
Why?
OR
Why do moss Plants produce very large number of male gametes? Provide one
reason what are these gametes called?

Ans. : In a moss plant, antherozoids represent the male gametes. Antherozoid depend on
water for theeir transport towards egg. To compensate this loss, antherozoids are
produced in large numbers to increase the chances of fertilization.

12. Which of the following are monoecious and dioecious organisms:

Cockroach.

Ans. : Dioecious.
13. In general, the male gametes are motile while the female gametes are stationary.
Mention two types of exceptions to this, with an example for each.

Ans. :
i. Both male and female gametes are non-motile, e.g. certain algae and few fungi.
ii. In seed plants, the male gametes are non-motile and are carried in the pollen
tube to the egg.
14. How is the milk production regulated by hormones in human female? Explain.

Ans. : Its synthesis is stimulated by the (pituitary) hormone prolactin; Its release is
stimulated by a rise in the level of oxytocin when the baby begins nursing.
Milk contains an inhibitory peptide.
If the breasts are not emptied the peptide accumulates and inhibits milk production.

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15. Zygote forms the major link between one generation and those of the next generation
organism. What is the fate of zygote in organisms which show:
Diplontic life cycle.

Ans. : Zygote of diplontic life cycle divides mitotically during embryogenesis.

16. The probability of fruit set in a self-pollinated bisexual flower of a plant is far greater
than a dioecious plant. Explain.

Ans. : A self-pollinated plant does not have to depend on agents of pollination. But a
dioecious plant has to depend on the agents of pollination for carrying out sexual
reproduction. In certain circumstances, the agents of pollination may not be available
because of various external factors.
For example: use of high level of pesticides has reduced the number of pollinating insects.
This is playing havoc with sexual reproduction in many flowering plants. So, the probability
of fruit set in a self-pollinated bisexual flowers of a plant is far greater than a dioecious
plant.

17. Is the presence of large number of chromosomes in an organism a hindrance to sexual

reproduction? Justify your answer by giving suitable reasons.

Ans. : Presence of large number of chromosomes in an organism is not a hindrance to

sexual reproduction Butterfly has 380 chromosomes but it can reproduce sexually.

18. Draw a yeast cell reproducing by budding and show the following labels in it:
i. Bud.
ii. Parent cell.
iii. Nucleus of bud.
iv. Nucleus of parent cell.

Ans. :

i. Budding in hydra (Expanded body with bud and gonads).

ii. Budding in yeast cell.
19. Is there a relationship between the size of an organism and its life span? Give two
examples in support of your answer.

Ans. : There is no relationship between the size of an organism and its life span. For
example; both mango and peepal tree are similar in size but a mango tree has a much
shorter life span compared to a peepal tree. A tortoise is much smaller than an elephant
yet the tortoise lives more than hundred years.

20. Describe the method which includes propagation of plants by culturing the cells, tissues
and organs.

Ans. : Vegetive propagation can also be done artificially and the man-made methods for
vegative propagation are called artificial methods of vegetative propagation. They
include:
i. Cutting in this method, a small piece of any plant organ (stem, root or leaf) is used
for propagation, e.g. leaves (Bryophyllum), roots (tamarind), stems (sugarcane,

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 grapes, rose and Bougainvillea).
ii. Layering in this method, roots are artificially induced on branches of stem before
they are detached from the parent plant, e.g. jasmine, grapevine, litchi, orange,
etc.
iii. Grafting in this method, parts of the two plants are joined in such a way that they
grow as one plant. The rooted supporting portion of one plant called stock, is
joined with the twig of another plant called scion, e.g. rose, apple, plum, peach,
mango, etc.
iv. Micropropagation This method includes propagation of plants by culturing the
cells, tissues and organs in laboratory which is called tissue culture. Initially, this
forms an undifferentiated mass of cells called callus. Later on, this callus
differentiates to produce many small plantlets.

SECTION C

* Given Section consists of questions of 3 marks each. [60]

1. Differentiate between gametogenesis from embryogenesis.

Ans. : Differences between gametogenesis and embryogenesis are as follows:

Gametogenesis Embryogenesis
1 It is the formation of male and female It is the formation of embryo from the
gametes. zygote.
2 Gametes are the haploid cells. Embryo is a diploid cell.
3 Both mitotic & meiotic cell division take Only mitotic division occur.
place.

2. 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.

Ans. : A flower that contains both the male and female reproductive structure (stamen and
pistil) is called a bisexual flower. Examples of plants bearing bisexual flowers are:

Water lily (Nymphaea odorata).

Rose (Rosa multiflora).

Hibiscus (Hibiscus Rosa-sinensis).

Mustard (Brassica nigra).

Petunia (Petunia hybrida).

3. Throughout sexual reproduction the chromosome number is maintained same. How is
this done?

Ans. : The gametes are usually formed by the meiotic divisions. Therefore, these are
haploid having half (n) the number of chromosomes. In sexual reproduction, male and
female gametes fuse to form a single cell called zygote. This process is called fertilisation.
The zygote formed by the fusion of two haploid gametes is thus diploid or having (2n)
number of chromosomes. So, we can say that meiosis and fertilisation are the two
important events in sexual reproduction that keep the number of chromosomes constant
from generation to generation.

4. Differentiate between oviparous and viviparous animals with an example of each.

Ans. :

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 Oviparous animals Viviparous animals
These are the animals which lay fertilised or These are the animals which give birth to
unfertilised eggs. young ones.
Chances of survival are less as offspring of Chances of survival are high as offspring of
oviparous animals are at a great risk as they viviparous animals are protected by the
are threatened by their predators and parent organism from predators/ enemies
unfavourable environmental conditions, e.g. and unfavourable climate, e.g. Human
frogs, birds. beings/ mammals.

5. Describe the process of sporulation seen in Amoeba.

Ans. :
Sporulation is the process in which the products of multiple fission become
individually surrounded by a cyst wall before being released from the parent;
each of them is a spore.
The spores remain dormant during unfavourable conditions and germinate when
conditions become favourable.

6. Describe the two major events that occur during embryogenesis and mention their
significance.

Ans. :
During embryogenesis, the zygote undergoes a number of mitotic divisions; this is
to increase the number of cells.
The cells thus formed undergo differentiation; this process helps groups of cells to
undergo modifications to form specialised tissues and organs.
7. Suggest a possible explanation why the seeds in a pea pod are arranged in a row,
whereas those in tomato are scattered in the juicy pulp.

Ans. : In a pea pod, the pericarp is not differentiated into many layers. In a tomato fruit, the
pericarp is differentiated into epicarp, mesocarp and endocarp. Most of the edible part or
tomato is composed of mesocarp which is juicy and fleshy. Moreover, placentation is
responsible for arrangement of seeds in a fruit. A pea flower shows marginal placentation,
while a tomato shows axial placentation.

8. Although sexual reproduction is a long drawn, energy-intensive complex form of

reproduction, many groups of organism in Kingdom Animalia and Plantae prefer this
mode of reproduction.
Give at least three reasons for this.

Ans. :
a. Sexual reproduction brings about variation in the offspring.
b. Since gamete formation is preceded by meiosis, genetic recombination occurring
during crossing over (meiosis-I), leads to a great deal of variation in the DNA of

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 gametes.
c. The organism has better chance of survival in a changing environment
9. It is generally observed that the number of male gametes produced is several thousand
times the number of female gametes. Explain.

Ans. : The number of male gametes produced is more than the female gametes because
male gametes are usually motile and they have to compete with one another for their
existence. While the female gamete is stationary. At the end only one male gamete fuses
with the female gamete for the fertilization to take place.

10. Is it possible to consider vegetative propagation observed in certain plants like

Bryophyllum, water hyacinth, ginger etc., as a type of asexual reproduction? Give two/
three reasons.

Ans. : Vegetative propagation in certain plants; like Bryophyllum, water hyacinth, ginger,
etc. can be termed as asexual reproduction. Following are some to the reasons for this:
Reproduction involves a single parent.

Meiosis does not happen during any stage of reproduction.

Offspring get the set of DNA from a single parent.

11. 'Fertilisation is not an obligatory event for fruit production in certains plants'. Explain the
statement.

Ans. : Yes, it is observed in parthenocarpic fruits. The ‘seedless fruits’ that are available in
the market such as pomegranate, grapes etc., are infact good examples. Flowers of these
plants are sprayed by a growth hormone that induces fruit development even though
fertilisation has not occurred. The ovules of such fruits, however, fail to develop into seeds.

12. Differentiate between Parthenocarpy and Parthenogenesis. Give one example of each.

Ans. : In most plants, flowers need to be pollinated and fertilized to produce fruits.
However, some plants can produce fruits before fertilization or without fertilization.
Parthenocarpy is the process which produces fruits from unfertilized ovules in plants.
Unfertilized ovules develop into fruits prior to fertilization. These fruits do not contain
seeds.
Parthenogenesis is a type of reproduction commonly shown in organisms mainly by some
invertebrates and lower plants. It can be described as a process in which unfertilized ovum
develops into an individual (virgin birth) without fertilization. Therefore, it can be
considered as a method of asexual reproduction.
It is seen in organism like rotifers, honeybees and even some lizards and birds (turkey).
The key difference between parthenogensis and parthenocarpy is, parthenogenesis is
shown by animals and plants while pathenocarpy is shown only by plants.

13. Differentiate between an annual and a biennial plant. Provide one example of each.

Ans. : Annual: complete their life cycle in one season/normally planted in spring and
produce grain before end of growing season/planted in autumn and harvested around mid
summer e.g. wheat/barley/rye/rice.
Biennial: They are (monocarpic) plants flower and die in the second season/complete their
life cycle in two seasons/show vegetative growth in one season and reproductive growth in
second season.

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 e.g.- Sugarbeet/cabbage/carrot/radish.

14. Diagrammatically represent the asexual reproduction in Amoeba.

Ans. :

15. What are the three major phases in the life cycle of an organism? Define each phase.
OR
Discuss the similarities in pattern of sexual reproduction.

Ans. : Juvenile phase, Reproductive phase, Senescent phase

Juvenile phase: The phase of growth in the organisms before reproductive maturity.
Reproductive phase: In this phase organism attains reproductive maturity.
Senescent phase: The phase between reproductive maturity and death.

16. Diagrammatically represent the asexual reproduction in yeast.

Ans. :

17. Reptiles and frogs are oviparous animals; yet they differ in certain aspects of
reproduction. Bring out the differences and mention which of the two animals has more
survival advantage.

Ans. :
Reptiles Frogs
In reptiles, fertilisation is internal. In frogs, fertilisation is external
They lay fertilised eggs in safe Both male and female gametes are laid in water.
places.
Eggs have a calcareous shell for Eggs have no calcareous shell, but have a
protection. mucilaginous covering.

18. With which type of reproduction do we associate the reduction division? Analyse the
reasons for it.

Ans. : Reduction division (meiosis) is associated with sexual reproduction. The reasons for
this are:

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 Since sexual reproduction involves the fusion of two types of gametes (male and
female), they must have haploid number of chromosomes.

The cell (meiocyte) which gives rise to gametes often has diploid number of
chromosomes and it is only by reducing the number by half that we can get
haploid gametes.
Reduction division also ensures maintenance of constancy of chromosome
number from generation to generation.
19. Describe the Polygonum type of embryo sac. Why is it referred to as monosporic?

Ans. : Polygonum type embryo sac: Embryo sac in angiosperms is eight nucleate
structure (seven - celled structure). Out of the eight nuclei formed by three successive
divisions of the functional megaspore three get organised at the micropylar end as egg
apparatus, three at the chalazal end as antipodals, and two at the centre as polar nuclei or
secondary nucleus (2n), The egg apparatus consists of two synergids and an egg cell (This
is monosporic type of development generally referred to as the Polygonum type).
Only one megaspore of the tetrad becomes functional/viable that develops into the
embryo sac.

20. i. Name two groups of plants each, which have a:

a. Haploid body and
b. Diploid body.
ii. What is meant by gamete transfer?

Ans. :
i.
a. Algae and bryophytes.
b. Pteridophytes, gymnosperms, angiosperms.
ii. Gamete transfer refers to the process by which male and female gametes are
physically brought together to facilitate their fusion.

SECTION E

* Given Section consists of questions of 5 marks each. [50]

1. Distinguish between asexual and sexual reproduction. Why is vegetative reproduction
also considered as a type of asexual reproduction?

Ans. :
Asexual reproduction Sexual reproduction
( It does not involves fusion of male There is fusion of gametes therefore progeny are
1 and female gametes. not identical to parents.
)
( Single parent involved. Two parents involved usually.
2
)
( The offspring are identical to the The offspring are not identical to their parents and
3 parent and are called as clones. show variations from each other and their parents.
)

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 ( It does not play important role in It play important role in evolution process.
4 evolution process.
)
( It is common in single celled It is common in high level organisms which have
5 organisms or organisms with simple complex structure.
) structure.
( Only mitotic cell division takes place. It involves both meiosis and mitosis.
6
)
( Rate of reproduction is faster. Rate of reproduction is slower.
7
)
Vegetative reproductions is also considered as a type of asexual reproduction because:

Single parent is involved.

There is no fusion of male and female gametes.

Offspring are generally identical.
2. Describe the post-fertilisation changes in a flower.

Ans. : Post-fertilization changes in flower are:

The sepal, petal and stamen of the flower withers and fall off only pistil remains
attached to the plant.

The zygote develops into the embryo.

The ovules develop into the seed.

The ovary develops into the fruit.

The ovary wall is transformed into a protective layer called the pericarp which
covers the fruit.
3. Enumerate the differences between asexual and sexual reproduction. Describe the
types of asexual reproduction exhibited by unicellular organisms.

Ans. :
Asexual Reproduction Sexual Reproduction
i. A single parent is involved in i. A single parent is involved in the process.
the process.
ii Meiosis does not happen. ii Meiosis happens during gametogenesis.
. .
ii Gametogenesis does not ii Gametogenesis happens.
i. happen. i.
i Genotype of offspring is i Genotype of offspring is a combination of two parents
v identical to that of parent. v and is hence different from parents.
. .
v It is mostly seen in simple v It is prevalent in complex organisms.
. organisms. .
Type of Asexual Reproduction in Unicellular Organisms:

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 Binary Fission: In this case, the unicellular organism undergoes cell division and
two daughter cells are produced. The parent generation ceases to exist after
binary fission. Example: Amoeba.

Multiple Fission: In this case, the nucleus of the mother cell divides into multiple
nuclei. A cyst develops around the mother cell. The cyst helps the mother cell to
tide over unfavourable circumstances. On resumption of favourable
circumstances, the cyst disintegrates and daughter nuclei develop into new
individuals. Example: Plasmodium, Entamoeba.

Budding: In this case, a bud develops at one end of the cell. The nucleus
produces a daughter nucleus which then goes to the bud. The bud then gets
detached from the mother cell and develops into a new individual. Example:
yeast.

4. Do all the gametes formed from a parent organism have the same genetic composition
(identical DNA copies of the parental genome)? Analyse the situation with the
background of gametogenesis and provide or give suitable explanation.

Ans. : No, all the gametes formed from a parent organism do not have the same genetic
composition .It can be better understand with the help of the emanation given below
Sexual reproduction in organisms generally involves the fusion of gametes from two
different individuals. These gametes form by the process of gametogenesis. In the
heterogametic species, gametes are of two types namely male and female. Gametes are
haploid though the parent body from which they arise may be either haploid or diploid,

A haploid parent like Monera, fungi, algae and bryophytes produce gametes by
mitotic division. The number of chromosomes, i.e., the genetic composition
remain same after such type of division.

The diploid parent like pteridophytes, gymnosperms, angiosperms and most of

the animals including human beings produces gametes by meiosis. In such
organisms(diploid), specialized cells called meiocytes (gamete mother cell)
undergo meiosis,At the end of meiosis only one set of chromosomes gets
incorporated into each gamete. It means the gametes formed contain a haploid
number of chromosomes in contrast to the number of chromosomes in mother
cells.
5. Differentiate between: Oestrus and Menstrual cycles.

Ans. : Oestrus and Menstrual cycles:

S. No Oestrus cycle Menstrual cycle
(i) It involves no uterine bleeding. It ends with uterine bleeding.
(ii) It continues until death. It continues till menopause.
(iii) Occurs in non-primates. eg. sheeps, cows. Occurs in apes and humans.

6. Differentiate between: Ovipary and Vivipary. Cite an example for each type.

Ans. : Based on whether the zygote develops outside the body of female parent or inside,
animals can be classified into oviparous and viviparous, respectively.

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 S. Oviparous animals Viviparous animals
N
o.
(i) Oviparous animals lay fertilized Viviparous animals give birth to young ones.
eggs.
(ii The fertilized eggs have calcareous The fertilized egg (zygote) has no shell and
) shell ans young ones hatch out after develops into a young one inside the body of
a period of incubation. the female organism.
(iii Chances of survival of young one is Chances of survival of young one is more
) less as the female lays egg in the because of proper embryonic care and
environment. protection inside the mother's body.
(iv For example, reptile, birds, ets. For example, majority of mammals including
) humans.

7. The unicellular organisms which reproduce by binary fission are considered immortal.
Justify.

Ans. : Asexual reproduction is common among single-celled organisms. Thus, in these

organisms cell division is itself a mode of reproduction. In binary fission, the parent body
divides into two halves and each half rapidly grows into an adult. There are no remains of
parent body cell and parent cannot be said to have died. In fact after binary fission, parent
continues living as two daughter individuals. Hence, the unicellular organisms which
undergo binary fission are considered immortal.
Example: Amoeba and Paramecium.

8. What are vegetative propagules? Name any four of them along with an example for
each.

Ans. : The units of asexual vegetative structures of plants which are capable of giving rise
to new individuals/ plants are called vegetative propagules.
Example:
i. Rhizome of ginger,
ii. Bulbil of Agave,
iii. Leaf buds of Bryophyllum,
iv. Bulbs of onion.
9. Do all the gametes formed from a parent organism have the same genetic
composition? Analyse the situation with the background of gametogenesis and provide
suitable explanation.

Ans. : Gametes do not have the same genetic composition formed by the parent organism.
Gametogenesis:
When male and female gametes are similar in appearance and it is not possible
to differentiate between them, they are called homogametes or isogametes.

When the male and female gametes are morphologically distinct, they are called
heterogametes.
 Among heterogametes, the male reproductive unit is called antherozoid or sperm
and female reproductive unit is called egg or ovum.

Unisexual male flowers bearing stamens are called staminate flowers.

Unisexual female flowers bearing pistils are called pistillate flowers.
10. Explain the process of budding with a suitable diagram. Also, explain its types.

Ans. : Budding
It is a mode of asexual reproduction in which one or more unequal and small projections
called buds are produced that remain attached initially to the parent cell, but eventually
get separated and mature into new organisms (cells), e.g. yeast, Hydra, etc.
Depending on the place where the bud arises, budding can be of two types:
i. External budding (Hydra and yeast): In Hydra, (multicellular organism)
regenerative cells are used for reproduction during budding. A bud develops as
an outgrowth due to the repeated cell divisions at one specific site. These buds
develop into tiny individuals which on getting fully matured, detach themselves
from the parent body becoming new independent individuals.

The same process occurs in yeast, where nucleus divides by the process of budding
into a new bud which gets detached from parent yeast.
ii. Internal budding (Gemmule formation): A mass of cells enclosed within a
common opaque envelop, rich in food, which germinates into a new plant, is
called a gemmule.

Gemmule formation is common in freshwater sponges (e.g. Spongilla) and a few

marine sponges. Each gemmule has a group of cells called archaeocytes surrounded
by the protective covering. During adverse environmental conditions, a mass of
archaeocytes comes out via micropyle (a minute pore) that grows into a colony.

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