Q.1. Why is reproduction essential for organisms?
Ans. Reproduction is a fundamental feature of all living organisms. It is a biological process through which living organisms produce offspring similar to them. Reproduction ensures the continuance of various species on the Earth. In the absence of reproduction, the species will not be able to exist for a long time and may soon get extinct.
Q.2. Which is a better mode of reproduction Sexual or Asexual? Why?
Ans. Sexual reproduction is a better mode of reproduction. It allows the formation of new variants by the combination of the DNA from two different individuals, typically one of each sex.
It involves the fusion of the male and the female gamete to produce variants, which are not identical to their parents and to themselves. This variation allows the individual to adapt to constantly changing and challenging environments. Also, it leads to the evolution of better-suited organisms which ensures greater survival of a species.
On the contrary, asexual reproduction allows very little or no variation at all. As a result, the individuals produced are exact copies of their parents and themselves.
Q.3. Why is the offspring formed by asexual reproduction referred to as clones?
Ans. A clone is a group of morphologically and genetically identical individuals.
In the process of asexual reproduction, only one parent is involved and there is no fusion of the male and the female gamete. As a result, the offsprings so produced are morphologically and genetically similar to their parents and are thus, called clones.
Q.4. Offspring formed due to sexual reproduction have better chances of survival. Why? Is this statement always true?
Sexual reproduction involves the fusion of the male and the female gamete. This fusion allows the formation of new variants by the combination of the DNA from two (usually) different members of the species.
The variations allow individuals to adapt under varied environmental conditions for better chances of survival. However, it is not always necessary that the offspring produced due to sexual reproduction has better chances of survival.
Under some circumstances, asexual reproduction is more advantageous for certain organisms.
Example: Some individuals who do not move from one place to another and are well settled in their environment.
Also, asexual reproduction is a fast and quick mode of reproduction that does not consume much time and energy as compared to sexual reproduction.
Q.5. How does the progeny formed from asexual reproduction differ from those formed by sexual reproduction?Ans. Q.6. Distinguish between Asexual and Sexual reproduction. Why is vegetative reproduction also considered as a type of asexual reproduction?Ans.
Vegetative propagation is a process in which new plants are obtained without the production of seeds or spores. It involves the propagation of plants through certain vegetative parts such as the rhizome, sucker, tuber, bulb, etc.
It does not involve the fusion of the male and the female gamete and requires only one parent. Hence, vegetative reproduction is considered as a type of asexual reproduction.
Q.7. What is Vegetative Propagation? Give two suitable examples.
Ans. Vegetative propagation is a mode of asexual reproduction in which new plants are obtained from the vegetative parts of plants. It does not involve the production of seeds or spores for the propagation of new plants.
Vegetative parts of plants such as runners, rhizomes, suckers, tubers, etc. can be used as propagules for raising new plants.
Examples of vegetative reproduction are:
Eyes of Potato Bryophyllum PlantQ.8. Define:(a) Juvenile Phase(b) Reproductive Phase(c) Senescent PhaseAns. (a) Juvenile phase:
It is the period of growth in an individual organism after its birth
it reaches reproductive maturity
.(b) Reproductive phase:
It is the period when an individual organism reproduces sexually
.(c) Senescent phase:
It is the period when an organism grows old
and loses the ability to reproduce.
Q.9. Higher organisms have resorted to sexual reproduction in spite of its complexity. Why?
Ans. Although sexual reproduction involves more time and energy, higher organisms have resorted to sexual reproduction in spite of its complexity.
Q.10. Explain why Meiosis and Gametogenesis are always interlinked?
Therefore, for producing haploid gametes (gametogenesis), the germ cells of an organism undergo meiosis. During the process, the meiocytes of an organism undergo two successive nuclear and cell divisions with a single cycle of DNA replication to form the haploid gametes.
Q.11. Identify each part in a flowering plant and write whether it is haploid (n) or diploid (2n).
(e) Male gamete______
(f ) Zygote______
(a) Diploid (2n)
(b) Diploid (2n)
(c) Haploid (n)
(d) Haploid (n)
(e) Haploid (n)
(f) Diploid (2n)
Q.12. Define External fertilization. Mention its disadvantages.
Ans. External fertilization is the process in which the fusion of the male and the female gamete takes place outside the female body in an external medium, generally water. Fish, frog, starfish are some organisms that exhibit external fertilization.
Disadvantages of external fertilization:
- A large quantity of gametes is wasted and left unfertilized.
- Chances of fertilization are diminished by environmental hazards and Predators.
- Eggs and sperms, essentially, may not come in contact.
- Dessication of zygote or gametes.
Q.13. Differentiate between a Zoospore and a Zygote.Ans.
Q.14. Differentiate between Gametogenesis from Embryogenesis.
Q.15. Describe the post-fertilization changes in a flower.
Q.16. What is a Bisexual flower? Collect five bisexual flowers from your neighborhood 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)
Structure of Bisexual Flower
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 flowers?
Ans. Cucurbit plant bears unisexual flowers as these flowers have either the stamen or the pistil. The staminate flowers bear bright, yellow coloured petals along with stamens that represent the male reproductive structure. On the other hand, the pistillate flowers bear only the pistil that represents the female reproductive structure.Cucurbit Plant
Other examples of plants that bear unisexual flowers are corn, papaya, cucumber, etc.
Q.18. Why are the offspring of oviparous animals at a greater risk as compared to offspring of viviparous animals?
Oviparous animals lay eggs outside their body. As a result, the eggs of these animals are under continuous threat from various environmental factors.
On the other hand, in viviparous animals, the development of the egg takes place inside the body of the female.
Hence, the offspring of an egg-laying or oviparous animal is at greater risk as compared to the offspring of a viviparous animal, which gives birth to its young ones.