GSEB Solutions Class 12 Biology Chapter 1 Reproduction in Organisms

Gujarat Board GSEB Textbook Solutions Class 12 Biology Chapter 1 Reproduction in Organisms Textbook Questions and Answers, Additional Important Questions, Notes Pdf.

Gujarat Board Textbook Solutions Class 12 Biology Chapter 1 Reproduction in Organisms

GSEB Class 12 Biology Reproduction in Organisms Text Book Questions and Answers

Question 1.
Why is reproduction essential for organisms?
Answer:
Reproduction is essential for a species to live generation after generation but it is not essential for an organism to survive.

Question 2.
Which is a better mode of reproduction: sexual or asexual? Why?
Answer:
Sexual. It brings genetic variation and inherited during reproduction. It helps to create new species.

Question 3.
Why is the offspring formed by asexual reproduction referred to as clone?
Answer:
The offspring produced after asexual reproduction are identical and exact copies of their parents. Such genetically and morphologically similar individuals are called clones.

Question 4.
How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?
Answer:
Yes. Because sexual reproduction brings changes in the genetic structure which leads to variation. This helps the organism to adjust or adapt according to the changes in the environment.

Question 5.
Distinguish between asexual and sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?
Answer:
In asexual reproduction, a single individual (parent) is capable of producing offspring. As a result, the progeny that are produced are not only identical to one another but are also exact copies of their parent.

Sexual reproduction involves the formation of the male and female gametes either by the same individual or by different individuals of the opposite sex. These gametes fuse to form the zygote which develops to form the new organism. The progeny produced in sexual reproduction are not identical to the parents.

Vegetative reproduction also involves a single individual and the progeny produced after vegetative reproduction are identical to one another. So it is considered as a type of asexual reproduction.

Question 6.
What is vegetative propagation? Give two suitable examples.
Answer:
The regeneration of new plants from portions of vegetative organs is called vegetative propagation. Vegetative propagation takes place naturally or artificially. Natural vegetative reproduction takes place by stem, root, leaves, and reproductive organs, e.g., Rhizome (e.g., ginger, banana), Stem tuber (e.g., potato), Root (e.g., Albizia lebbeck).

Question 7.
Define a. Juvenile phase
b. Reproductive phase
c. Senescent phase
Answer:
(a) Juvenile phase: The period of growth is called the juvenile phase. It is known as a vegetative phase in plants.
(b) Reproductive phase: The phase during which the organisms are able to produce their offsprings.
(c) Senescent phase: The period during which the organisms lose their ability to produce their offspring.

Question 8.
Explain why meiosis and gametogenesis are always interlinked?
Answer:
Gametogenesis is the process of the production of gametes. Gametes are haploid in nature produced from diploid gametic cells. The diploid cell undergoes meiotic division followed by mitotic division produces gametes.

Question 9.
Identify each part in a flowering plant and write whether it is haploid (n) or! diploid (2n).
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 10.
Define external fertilization. Mention its disadvantages
Answer:
Fertilization which involves the union of an egg with the sperm outside the body of the female is called external fertilization. It generally takes place in the medium of water. There is a chance of loss of male gamete during transport in water which leads to failure of external fertilization. Therefore the number of male gametes produced is several thousand times the number of female gametes produced.

Question 11.
Differentiate between a zoospore and a zygote.
Answer:
Zoospore is an asexual spore that uses a flagellum for moving around. It is also called a swarm spore. These spores are created by some algae and fungi to multiply themselves.

Zygote is a cell that is the result of fertilization i.e., two haploid cells – usually an ovum from a female and a sperm cell from a male – merge into a single diploid cell called the zygote.

Question 12.
Differentiate between gametogenesis from embryogenesis.
Answer:
Gametogenesis is a process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes into various gametes or by mitotic division of haploid gametogenous cells.

In flowering plants, the male gamete is produced inside the pollen grain through the division of a generative cell into two sperm nuclei. The female gamete is produced inside the embryo sac of the ovule.

Embryogenesis is the process by which the embryo is formed and develops. It starts with the fertilization of the ovum, egg which after fertilization, then called a zygote. The zygote undergoes rapid mitotic divisions. The formation of two exact genetic replicates of the original cell with no significant growth and cellular differentiation leads to the development of an embryo.

Plant embryogenesis is the process that produces a plant embryo from a fertilized ovule by asymmetric cell division and the differentiation of undifferentiated cells into tissues and organs. It occurs during seed development when the single-celled zygote undergoes a programmed pattern of cell division resulting in a mature embryo.

Question 13.
Describe the post-fertilization changes in a flower.
Answer:
Post fertilization changes in a flower
After fertilization, the sepals, petals, and stamens of a flower wither and fall off. The pistil remains attached. The ovary develops into fruit and the ovule develops into the seed. The zygote develops into the embryo. After dispersal, seeds germinate under favourable conditions to produce new plants.

Question 14.
What is a bisexual flower?
Answer:
The flower in which both reproductive organs i.e. stamen and pistil are present is called a bisexual flower.

GSEB Class 12 Biology Reproduction in Organisms Additional Important Questions and Answers

Question 1.
Study the relation of the given pair and fill up the blanks
a. Bud : Hydra : : : Penicillium
b. Algae : Zoospores : : Sponges :
c. Monoecius palm : Coconut : : Dioecious palm :
d. Primates : Menstrual cycle : : Non primates :
e. Unisexual male : Staminate : : Unisexual female :
Answer:
a. Conidia
b. Gemmule
c. Date palm
d. Oestrus cycle
e. Pistillate

Question 2.
Differentiate between staminate and pistillate flower. Give the term for this condition of flower.
Answer:

• The unisexual male flower is called staminate, which bears only stamen.
• The unisexual female flower is called pistillate, which bears only pistil.
• Heterothallic or dioecious are the terms used to describe this condition.

Question 3.
In sexually reproducing organisms during reproduction, male gametes are produced in huge numbers. Why?
Answer:
In almost all organisms, the female gamete is stationary and male gametes are mobile. The male gametes must travel through a medium to reach the female gametes. However, most of them fail to reach the female gametes. To compensate this loss of male gametes during transport, the number of male gametes produced is several thousand times the number of female gametes.

Question 4.
The cyclical changes in the ovaries of female placental mammals during the reproductive phase differ in primates and nonprimates.
a. What is this cycle called in primates and nonprimates respectively?
b. Distinguish between seasonal breeders and continuous breeders.
Answer:
a. In primates the cycle is called as menstrual cycle and in nonprimates, it is called as oestrus cycle.
b. Many mammals living in natural conditions exhibit such reproductive cycles only during favourable seasons, therefore called as seasonal breeders. Others are reproductively active throughout their reproductive phase and hence called as continuous breeders.

Question 5.
Harish observed two different types of papaya plants in his garden. One produced male flowers only and the other type produced female flowers as well as fruits.
a. What are these types of plants called in which male and female flowers seen separately?
b. Name another plant with the same feature.
c. If both male and female flowers are seen separately in the same plant, what do you call them? Give examples.
Answer:
a. Dioecious
b. Date palm
c. Monoecious, e.g. Coconut, cucurbits

Question 6.
In the animal world, some organisms have both male and female reproductive organs.
a. What do you call such organisms?
b. Give two examples.
Answer:
a. Hermaphrodites
b. Earthworm, sponges etc.

Question 7.
In Ashes as well as amphibians where does syngamy occur. What type of fertilization occurs.
Answer:
In lower animals like fishes and amphibians syngamy occurs outside the body i.e., in water media. Therefore the type of fertilization is external fertilization.

Question 8.
Syngamy is the fusion of gametes to produce zygotes. But in some organisms like rotifers, honey bees and even some lizards, syngamy doesn’t occur. Then how do these organisms produce young ones? Name the phenomenon.
Answer:
In these organisms, the female gamete undergoes development to form new organism without fertilization. This phenomenon is called parthenogenesis.

Question 9.
a. Differentiate oviparous and viviparous with examples.
b. In which of these two types, is the chances of survival of young ones, greater? Why?
Answer:
a. Oviparous animals are those which lay eggs, covered by hard calcareous shell in a safe place. These eggs after a period of incubation hatch out as young ones.
e.g. Reptiles and birds
Viviparous animals are those which keep the fertilization product – zygote within the body of female organism and after attaining a certain stage of growth are delivered from the body, e.g. Human beings
b. Viviparous. Because of proper embryonic care and protection inside the body.

Question 10.
Match the following asexual reproductive methods or structures with the respective organisms.

Reproductive method or structures	Organisms
a. Binary fission	Algae
b. Buds	Sponges
c. Zoospores	Amoeba
d. Conidia	Hydra
e. Gemmules	Penicillium

Answer:
a – Amoeba, b – Hydra, c – Algae, d – Penicillium, e – Sponges

Question 11.
Why do intermodal segments of sugarcane fail to propagate vegetatively even when they are in contact with damp soil?
Answer:
Internodal segments lack the initials for producing root and shoot.

Question 2.
Draw a labelled diagram for asexual reproduction in the following.
i. Budding in yeast
ii. Binary fission in amoeba.
Answer:

Question 3.
What is a bulbil?
Answer:
A branch or offshoot, detached from the parental plant falls on the soil and grows into a new plant.
e.g. Agave.