NCERT Exemplar Class 12 Biology Solutions Chapter 1 Reproduction in Organisms

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NCERT Exemplar Class 12 Biology Chapter 1 Reproduction in Organisms

Multiple Choice Questions:

Question:1

A few statements describing certain features of reproduction are given below:

i. Gametic fusion takes place

ii. Transfer of genetic material takes place

iii. Reduction division takes place

iv. Progeny have some resemblance with parents

Select the options that are true for both asexual and sexual reproduction from the options given below:

(a) i and ii; (b ) ii and iii; (c) ii and iv; (d) i and iii.

Answer:

The answer is the option (c) (ii) and (iv)

Explanation: Gametic fusion and reduction division take place only in case of sexual reproduction.

Question:2

The term 'clone' cannot be applied to offspring formed by sexual reproduction because:

a. Offspring do not possess exact copies of parental DNA

b. DNA of only one parent is copied and passed on to the offspring

c. Offspring are formed at different times

d. DNA of parent and offspring are completely different.

Answer:

The answer is the option a) Offspring do not possess exact copies of parental DNA

Explanation: Crossing Over takes place during meiosis and is responsible for some alteration in genotype. During fertilisation, gene pools of two different individuals combine to form a zygote, which has a different genotype than both of its parents. Hence, the term cannot be applied to offspring formed by sexual reproduction.

Question:3

Asexual method of reproduction by binary fission is common to which of the following?

i. Some eukaryotes

ii. All eukaryotes

iii. Some prokaryotes

iv. All prokaryotes

Choose the correct option from the following:

(a) i and ii; (b) ii and iii; (c) i and iii; (d) iii and iv.

Answer:

The answer is the option (c) (i) and (iii)

Explanation: Not all Prokaryotes reproduce by binary fission. Other Asexual reproduction methods like multiple fission and spore formation, are also seen in

prokaryotes. Eukaryotes reproduce through both asexual and sexual reproduction methods.

Question:4

A few statements with regard to sexual reproduction are given below:

i. Sexual reproduction does not always require two individuals

ii. Sexual reproduction generally involves gametic fusion

iii. Meiosis never occurs during sexual reproduction

iv. External fertilisation is a rule during sexual reproduction

Choose the correct statements from the options below:

(a) i and iv (b) i and ii (c) ii and iii (d)

Answer:

The answer is the option (b), (i) and (ii)

Explanation: Sexual reproduction does not always require two individuals as both the sexes are present on the same individual. In some of these cases, both the gametes from the same individual are involved.

Question:5

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

Answer:

The answer is the option (d)

Explanation: Many Algae exhibit haplontic life cycle, where the dominant phase is free-living gametophyte. Sporophytic generation is represented by single-celled

zygote. Meiosis leads to the formation of haploid spores eg- Spirogyra and Chlamydomonas.

Question:6

The male gametes of rice plant have 12 chromosomes in their nucleus.The chromosome number in the female gamete, zygote and the cells of the seedling will be, respectively,

a. 12, 24, 12

b. 24, 12, 12

c. 12, 24, 24

d. 24, 12, 24.

Answer:

The answer is the option (c) 12, 24, 24

Explanation: Gametes have haploid number of chromosomes, whereas zygote and plants have diploid number of chromosomes.

Question:7

Given below are a few statements related to external fertilisation. Choose the correct statements.

i. The male and female gametes are formed and released simultaneously

ii. Only a few gametes are released into the medium

iii. Water is the medium in a majority of organisms exhibiting external fertilisation

iv. Offspring formed as a result of external fertilisation have a better chance of survival than those formed inside an organism

(a) iii and iv (b) i and iii (c) ii and iv (d) i and iv

Answer:

The answer is the option (b), (i) and (iii)

Explanation: Fertilisation requires both the gametes to be released simultaneously. A medium is needed by Male gametes to travel to the female gametes. Water is the medium in most cases. Air also acts as the medium in some cases.

Question:8

The statements given below describe certain features that are observed in the pistil of flowers.

i. A pistil may produce more than one seed

ii. Each carpel may have more than one ovule

iii. Each carpel has only one ovule

iv. The pistil has only one carpel

Choose the statements that are true from the options below:

(a) i and ii (b) i and iii (c) ii and iv (d) iii and iv

Answer:

The answer is the option (a), (i) and (ii)

Question:9

Which of the following situations correctly describe the similarity between an angiosperm egg and a human egg?

i. Eggs of both are formed only once in a lifetime

ii. Both the angiosperm egg and human egg are stationary

iii. Both the angiosperm egg and human egg are mobile

iv. Syngamy in both results in the formation of zygote

Choose the correct answer from the options given below:

(a) ii and iv (b) iv only (c) iii and iv (d) i and ii

Answer:

The answer is the option (b) iv only.

Explanation: Option (i) is incorrect as Eggs are formed several times during the lifetime in angiosperms. Option (ii) is incorrect as Human eggs travel from ovaries to the fallopian tube. Option (iii) is also incorrect as angiosperm eggs are stationary.

Question:10

The appearance of vegetative propagules from the nodes of plants such as sugarcane and ginger are mainly because:

a. Nodes are shorter than internodes

b. Nodes have meristematic cells

c. Nodes are located near the soil

d. Nodes have non-photosynthetic cells

Answer:

The answer is the option (b) iv only.

Explanation: Option (i) is incorrect as Eggs are formed several times during the lifetime in angiosperms. Option (ii) is incorrect as Human eggs travel from ovaries to the fallopian tube. Option (iii) is also incorrect as angiosperm eggs are stationary.

Question:10

The appearance of vegetative propagules from the nodes of plants such as sugarcane and ginger are mainly because:

a. Nodes are shorter than internodes

b. Nodes have meristematic cells

c. Nodes are located near the soil

d. Nodes have non-photosynthetic cells

Answer:

The answer is the option (b) Nodes have meristematic cells

Explanation: Vegetative propagation requires meristematic cells

Question:11

Which of the following statements, support the view that an elaborate sexual reproductive process appeared much later in the organic evolution.

i. Lower groups of organisms have simpler body design

ii. Asexual reproduction is common in lower groups

iii. Asexual reproduction is common in higher groups of organisms

iv. The high incidence of sexual reproduction in angiosperms and vertebrates

Choose the correct answer from the options given below:

(a) i, ii and iii; (b) i, iii and iv (c) i, iii and iv (d) ii, iii and iv

Answer:

The answer is the option (c) (i), (ii) and (iv)

Explanation: Asexual reproduction is not common in higher groups of organisms.

Question:12

Offspring formed by sexual reproduction exhibit more variation than those formed by Asexual reproduction because:

a. Sexual reproduction is a lengthy process

b. Gametes of parents have qualitatively different genetic composition

c. Genetic material comes from parents of two different species

d. The greater amount of DNA is involved in sexual reproduction.

Answer:

The answer is the option (b) gametes of parents have a qualitatively different genetic composition

Explanation: During fertilisation, gene pools of two different individuals combine to form a zygote, which has a different genotype than both of its parents.

Question:13

Choose the correct statement from amongst the following:

a. Dioecious (hermaphrodite) organisms are seen only in animals

b. Dioecious organisms are seen only in plants

c. Dioecious organisms are seen in both plants and animals

d. Dioecious organisms are seen only invertebrates

Answer:

The answer is the option (c) Dioecious organisms are seen in both plants and animals

Explanation: Many flowering plants are dioecious. Ex – Pheretima

Question:14

There is no natural death in single-celled organisms like Amoeba and bacteria because:

a. They cannot reproduce sexually

b. They reproduce by binary fission

c. The parental body is distributed among the offspring

d. They are microscopic

Answer:

The answer is the option (c) Parental body is distributed among the offspring

Explanation: Single-celled organisms reproduce by binary fission. As the mother cell divides into 2 daughter cells, the mother cell does not die in the process.

Question:15

There are various types of reproduction. The type of reproduction adopted by an organism depends on:

a. The habitat and morphology of the organism

b. Morphology of the organism

c. Morphology and physiology of the organism

d. The organism’s habitat, physiology and genetic makeup

Answer:

The answer is the option (d) The organism’s habitat, physiology and genetic makeup

Explanation: The organism’s habitat, physiology and genetic makeup

Question:16

Identify the incorrect statement.

a. In asexual reproduction, the offspring produced are morphologically and genetically identical to the parent b. Zoospores are sexual reproductive structures

c. In asexual reproduction, a single parent produces offspring with or without the formation of gametes

d. Conidia are asexual structures in Penicillium

Answer:

The answer is the option (b) Zoospores are sexual reproductive structures

Explanation: Zoospores are sexual reproductive structures

Question:17

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

Answer:

The answer is the option (b) Embryo development

Explanation: Reproduction Sequence in flowering plants is as shown:

Formation of flower → formation of pollen grains→transfer of pollen grains → fertilisation → embryo development

Question:18

The number of chromosomes in the shoot tip cells of a maise plant is 20.The number of chromosomes in the microspore mother cells of the same plant shall be:

a. 20

b. 10

c. 40

d. 15

Answer:

The answer is the option (a) 20

Explanation: microspore mother cells has same ploidy as the vegetative parts.

Very Short Answer Type Questions:

Question:1

Mention two inherent characteristics of Amoeba and yeast that enable them to reproduce asexually.

Answer:

Amoeba and yeast can reproduce asexually due to the following reasons:

They are unicellular organisms

They have a simple organisation

Question:2

Why do we refer to offspring formed by the asexual method of reproduction as clones?

Answer:

Asexual reproduction requires only a single parent and involves only the process of mitosis, which ensures that variation is not possible in offspring, and they are clones of their parents.

Question:3

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

Answer:

Potato Tuber is considered a stem due to the presence of the following features:

(a) Nodes (eyes)

(b) Scaly leaves

Question:4

Between an annual and a perennial plant, which one has a shorter juvenile phase? Give one reason.

Answer:

Annual plants have shorter juvenile phase compared to perennial plants. The number of flowering seasons in a year determines the length of the juvenile phase. While some perennial plants may produce flower only once in a year (some produce flowers once in 50 or even 100 years), annual plants have much shorter life cycles and thus, shorter juvenile phase.

Question:5

Rearrange the following events of sexual reproduction in the sequence in which they occur in a flowering plant: embryogenesis, fertilisation, gametogenesis, and pollination.

Answer:

Gametogenesis → Pollination → Fertilization → Embryogenesis

Question:6

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

Answer:

Dioecious plants depend on agents of pollination to carry out sexual reproduction. The availability of agents is impacted significantly by external factors. Ex – Usage of high level of pesticides has reduced the population of pollinating insects. Hence, the probability of fruit set in self-pollinated bisexual flowers is far greater than a dioecious plant.

Question:7

Is the presence of a large number of chromosomes in an organism a hindrance to sexual reproduction? Justify your answer by giving suitable reasons.

Answer:

The number of chromosomes is not a deciding factor for the mode of reproduction.

Ex – Somatic cell of fruit fly only has 8 chromosomes, whereas somatic cell of a butterfly has 380 chromosomes, yet both of them reproduce sexually.

Question:8

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

Answer:

There is no relationship between the size of an organism and its life span. Ex – Though, mango and peepul tree have similar sizes; mango tree has a much shorter life span.

Question:9

In the figure given below the plant bears two different types of flowers marked ‘A’ and ‘B’. Identify the types of flowers and state the type of pollination that will occur in them.

Answer:

Chasmogamous flowers are shown in ‘A’ as they have exposed anther and stigma. Cross-pollination will be their mode of pollination.

They will require an agent of pollination.

Flowers shown in ‘B’ do not open. These are bisexual flowers and self-pollination will be their mode of pollination.

Question:10

Give reasons as to why cell division cannot be a type of reproduction in multicellular organisms.

Answer:

As multicellular organisms have a complex organisation; it isn’t possible for a single cell to produce all different types of tissues simply by undergoing mitosis.

Question:11

In the figure given below, mark the ovule and pericarp

Answer:

Question:12

Why do gametes produced in large numbers in organisms exhibit external fertilisation?

Answer:

In external fertilisation, gametes are affected by their surroundings; they can get blown off by the wind, washed away by water, eaten by predators etc. and most of the gametes perish before fertilisation. A higher number of gametes increase the probability of fertilisation.

Question:13

Which of the followings are monoecious and dioecious organisms?

a. Earthworm ______________

b. Chara ______________

c. Marchantia ______________

d. Cockroach _____________

Answer:

(a) Dioecious

(b) Monoecious

(c) Dioecious

(d) Monoecious

Question:14

Match the organisms given in Column-’A’ with the vegetative propagules given in column ‘B’

Answer:

i→(c)

ii→(d)

iii→(b)

iv→(a)

Question:15

What do the following parts of a flower develop into after fertilisation?

a. Ovary ______________

b. Ovules _____________

Answer:

(a) Fruits

(b) Seeds