Higher Secondary Biology Question Answer Chapter 1 Reproduction In Organisms
Chapter: 1
Reproduction in Organisms
Q 1. Why is reproduction essential for organisms?
Ans: Reproduction is an important characteristic of living organisms. It is a biological method by which living organisms can reproduce offsprings of its kind. It helps to maintain continuity of different species on the earth.
Q 2. Which is a better mode of reproduction sexual or asexual? Why?
Ans: Sexual reproduction is a better mode of reproduction as it brings variation by the association of DNA from two different individuals. Sexual reproduction occurs due to the fusion of male and female gametes which brings variation in their offsprings. Such variation helps the individual to adapt in the changing environments. This results to the evolution in which the best suited organisms can survive for the continuity of their species on Earth.
But the asexual reproduction shows no variation as they have same genes present in their parents.
Q 3. Why is the offspring formed by asexual reproduction referred to as clone?
Ans: A clone is the asexual reproduction in which the offspring are genetically identical to the parent. In the asexual reproduction, single parent is involved so there is no fusion of gametes occurs. As a result, the offspring produced in an asexual reproduction contains exact copies of genes present in parent cell.
Q 4. Offspring formed due to sexual reproduction have better chances of survival. Why? Is this statement always true?
Ans. Sexual reproduction occurs due to the fusion of male and female gamete. This fusion brings variation in the offspring formed by the association of DNA from two different individuals. Such variation helps the individual to adapt in the changing environments. This results to the evolution in which the best suited organisms can survive for the continuity of their species on Earth.
Q 5. How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?
Ans: In asexual reproduction, there is no fusion of male and female gamete occurs. The offspring produced by asexual reproduction are genetically identical to the parent. Thus the offsprings produced by asexual reproduction do not show variations.
In sexual reproduction, fusion of male and female gamete takes place. The offspring produced by sexual reproduction are not genetically identical to the parent. Thus, the offspring shows variation from each other.
Q 6. Distinguish between asexual and sexual reproduction. Why vegetative reproduction is also considered as a type of asexual reproduction?
Ans: Sexual reproduction
· In sexual reproduction, fusion of male and female gamete takes place.
· Involvement of two individuals, typically of each sex.
· Offspring produced by sexual reproduction shows variation from their parents.
· The process of sexual reproduction is slow.
Asexual reproduction
· In asexual reproduction, fusion of male and female gamete does not take place.
· Involvement of single parent.
· Offspring produced by asexual reproduction are genetically identical and thus, do not shows variation from their parents.
· The process of asexual reproduction is fast.
Vegetative propagation is the method from which offspring are produced from the vegetative parts of plants such as tuber, rhizome, sucker etc. There is no fusion of male and female gamete takes place, only single parent is involved. Thus, vegetative reproduction is also considered as a type of asexual reproduction.
Q 7. What is vegetative propagation? Give two suitable examples.
Ans: Vegetative reproduction is a kind of asexual reproduction from which offspring are produced from the vegetative parts of plants such as tuber, rhizome, sucker etc. The production of seeds or spores does not involve in this process.
Examples of vegetative propagation:
· There are several buds present on the surface of potato called eyes. Each bud develops into a new plant, when buried in soil. The new plant is genetically identical to the parent plant.
· There are several adventitious buds on the margins of bryophyllum plant’s leaves. These buds develop into a new plant when the leaves fall on the moist soil.
Q 8. Define
a) Juvenile phase- It is the period of change in an organism after birth and before reproductive maturity is attained.
b) Reproductive phase: It is the time during which an organism sexually reproduces.
c) Senescent phase: it is the time during which the organism becomes old and loses the capability to reproduce.
Q 9. Higher organisms have resorted to sexual reproduction in spite of its complexity. Why?
Ans: Higher organisms have resorted to sexual reproduction in spite of its complexity because new variations are introduced in the progenies due to the combination of DNA from two different parents. This variation helps them to adapt with various environmental conditions. As it leads to the evolution in which the best suited organisms can survive for the continuity of their species on Earth.
Q 10. Explain why meiosis and gametogenesis are always interlinked?
Ans: Meiosis is a mechanism in which a single cell divides to create four cells that contain half of the original amount of genetic material. The formation of gametes is called gametogenesis. Organisms produced haploid gametes but the body of an organism is diploid. In order to produce haploid gametes, the germ cell undergoes meiosis.
Q 11. Identify each part in flowering plant and write whether it is haploid (n) or diploid (2n).
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
Q 12. Define external fertilization. Mention its disadvantages.
Ans: External fertilization is the fertilization in which the fusion of male and female gamete occurs outside the female body in an outside medium, mainly in water. Ex- fish and frog
Disadvantages of external fertilization:
· There are a less chances of fertilization of egg.
· Proper parental care to the offspring is absent.
· Low rate of survival of the offsprings.
Q 13. Differentiate between a zoospore and a zygote.
Zoospore
· Zoospore is the asexual spore which has the ability to move with help of flagella.
· It is a structure of asexual reproduction.
Zygote
· Zygote is a diploid cell which does not has the ability to move.
· Formation of a zygote is the result of fertilization.
Q 14. Differentite between gametogenesis from embryogenesis.
Ans: Gametogenesis the process of formation of haploid gamete from diploid meiocytes by the process called meiosis.
Embryogenesis is the process of embryo development from the repeated mitotic divisions of the diploid zygote.
Q 15. Describe the post-fertilization changes in a flower.
Ans: A diploid zygote is formed by the fusion of male and female gamete by the process of fertilization. After the process of fertilization, the zygote splits to form an embryo. The seed is formed from fertilized ovule. The seed coat surrounds the seed to protect the seeds from external environment. The ovary grows to becomes fruit.
Q 16. What is bisexual flower? Collect five bisexual flowers from your neighborhood and with the help of your teacher find out their common and scientific names.
Ans: Bisexual flower is the flower comprises of both male and female reproductive part.
In here we should collect some bisexual flower from neighborhood and write their common and scientific names. For ex:
1) Rose (Rosa multiflora)
2) Hibiscus ( Hibiscus Rosasinensis)
Q 17. 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 flower?
Ans: The flower present in cucurbit plant is unisexual. It has either stamen or pistil. By removing its petal we can see the flowers reproductive parts.
Q 18. Why are offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?
Ans: Oviparous animals lay eggs in the environment. Thus, the egg of oviparous animals is under continual threat from various factors in the environment.
In viviparous animal, the formation of egg takes place inside the female body. Hence, the offspring of oviparous animals are at a greater risk as compared to offspring of viviparous animals.
by
Dipshika Das
Post Id: DABP000951
