biological 1st lesson of standard 12th all questions and answers
Answers
Answer:
Which do you want CBSE, NCERT or STATE
Explanation:
I have NCERT answers
Access Answers of Biology NCERT Chapter 1 – Reproduction in Organisms....
1. Why is reproduction essential for organisms?
Solution:
Reproduction is essential for the continuity of species on earth. If the organisms do not reproduce, life will cease to exist.
2. Which mode of reproduction is better: asexual or sexual? Why?
Solution:
Sexual reproduction is better than asexual reproduction because it produces offsprings that are genetically unique from the parents. It also means that the offspring will be more resilient and be able to survive better than either parent due to genetic variation.
3. Why is the offspring formed by asexual reproduction referred to as clone?
Solution:
The offsprings formed by asexual reproduction are referred to as clones because it involves only a single parent. Furthermore, there is no recombination of genes and the offsprings produced are genetically identical.
4. Offsprings formed due to sexual reproduction have better chances of survival. Why? Is this statement always true?
Solution:
Sexual reproduction is said to occur when two gametes fuse. This leads to the production of the offspring that are genetic variants of the parents and therefore, are able to survive better.
However, the organisms produced by sexual reproduction do not always survive more than those produced by asexual reproduction. Sometimes, the organisms produced by asexual reproduction survive better than those produced by sexual reproduction. Also, it is a fairly quick process and consumes less energy and time.
5. How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?
Solution:
The progeny formed by asexual reproduction involves a single parent and are genetically identical to the parent whereas the progeny formed by sexual reproduction are formed when male and female gametes fuse together and are genetically unique.
6. Distinguish between sexual and asexual reproduction. Why is vegetative reproduction also considered a type of asexual reproduction?
Solution:
Differences between sexual and asexual reproduction are mentioned below:
Sexual Reproduction Asexual Reproduction
It takes place by the fusion of male and female gametes. In this, the organism arises from a single organism.
The offsprings produced are not identical to the parents. The offsprings produced are identical to the parents and are known as clones.
It is found in higher invertebrates and all the vertebrates. It is found in lower organisms.
It is a slow process. It is faster compared to sexual reproduction.
For eg., Humans and nearly most other higher lifeforms exhibit sexual reproduction. Conjugation can also be considered as the bacterial equivalent of sexual reproduction. For eg., Budding, fragmentation. Even cloning is considered as a form of asexual reproduction.
Vegetative reproduction is considered to be a form of asexual reproduction as it does not involve the fusion of male and female gametes. In this, a new plant grows from the fragment of the genetically identical parent plant.
7. What is vegetative propagation? Give two suitable examples.
Solution:
Vegetative propagation is a common form of asexual reproduction observed plants. In this, a fragment of a plant is used to grow another plant. Many plants reproduce naturally as well artificially by vegetative propagation and the offsprings produced are genetically identical.
For eg., ginger, garlic
8. Define:
Juvenile phase
Reproductive phase
Senescent phase
Solution:
Juvenile phase: It is defined as the period of growth between an organism’s birth and reproductive maturity.
Reproductive phase: It is the phase in which an organism can reproduce sexually. In males, it lasts until death, but in females it lasts uptil the age of 50.
Senescent phase: It is the period of ageing in an organism.
9. Higher organisms have resorted to sexual reproduction in spite of their complexity. Why?
Solution:
Higher organisms undergo sexual reproduction despite its complex nature because the organisms are produced by the fusion of two different gametes and therefore show genetic variations. Due to these variations, they are well adapted to different environmental factors, and hence usually have higher rates of survival.
10. Explain why meiosis and gametogenesis are always interlinked?
Solution:
Meiosis is the process that occurs during gametogenesis. Gametogenesis refers to the process of how gametes are formed. Meiosis is necessary for the formation of gametes. Hence, both the processes are said to be interlinked.
11. Identify each part in a flowering plant and write whether it is haploid (n) or diploid (2n).
Ovary
Anther
Egg
Pollen
Male gamete
Zygote
Solution:
Ovary – Diploid (2n)
Anther – Diploid (2n)
Egg – Haploid (n)
Pollen – Haploid (n)
Male gamete – Haploid (n)
Zygote – Diploid (2n)
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