SEE Science (Asexual and sexual reproduction) Notes

    Asexual and sexual reproduction

1.    What is asexual reproduction?

Ans: The reproduction which takes place without the fusion of male gamete and female gamete is called asexual reproduction.

2.     Show with neat diagram of binary fission that takes place in Amoeba.

Ans:

3.     Define sporulation.

Ans: The method of asexual reproduction which takes place by the formation of spores is called sporulation.

4.     Write down the significance of asexual reproduction.

Ans: The significance of asexual reproduction is given below:

a) The characters of a plant are preserved by this method.

b) It is cheaper, easier and faster method of reproduction.

c) The plants which do not produce viable seeds can easily be propagated by this method.

d) The plants produced by this method bear flowers and fruit earlier than those produced from seeds.

5.    A new rose plant is grown by panting a piece of its stem in the soil. What type of asexual reproduction is it? Why is this process used in rose? Give three reasons why such type of reproduction is more beneficial.

Ans: A new rose plant is grown by planting a piece of its stem in the soil. This type of           reproduction is called vegetative propagation by stem.

        This process is used in rose because rose does not produce viable seeds.

This type of reproduction is more beneficial than other types of reproduction due to the following reasons:

i) Gardeners, farmers and botanists can grow a large number of plants by this method.

ii) The plants which do not produce viable seeds like rose, sugarcane, potato, etc. can easily be propagated by this method.

iii) The plants produced by this method bear flowers and fruit earlier than those produced from seeds.

6.    Name one example of each organism which reproduces by the following methods.   

a)    Budding – Hydra, Yeast etc.

b)    Binary fission – Amoeba, Bacteria, Paramecium, Euglena, Diatoms etc.

c)    Multiple fission – Plasmodium, Chlamydomonas etc. 

d)    Sporulation – Moss, Mushroom, Fern, Mucor, Marchantia etc.

e)    Vegetative propagation by root – Sweet potato, Sissoo, Dahlia, Carrot, Asparagus etc.

f)    Vegetative propagation by stem – Onion, Mint, Cynodon (DUBO), Potato, Ginger, Garlic, Canna, Turmeric etc.

g)    Vegetative propagation by leaf - Bryophyllum

h)    Regeneration – Tapeworm, Hydra, Starfish, Earthworm, Planarion etc.

i)     Fragmentation - Spirogyra

7. What is sexual reproduction?

Ans: The complex process in which reproduction takes place by the fusion of male gamete and female gamete is called sexual reproduction.

8.    What is pollination? Differentiate between self-pollination and cross-pollination.

Ans: Pollination is the process of transfer of pollen grains from the anther to the stigma of a flower.

Self-pollination	Cross-pollination
1. It is the process of transfer of pollen grains from anther to the stigma of same flower.	1. It is the process of transfer of pollen grains from anther of a flower of one plant to the stigma of a flower of another plant of the same species.
2. External agents of pollination are not required.	2. External agents of pollination like insects wind, water, etc. are required.
3. It does not help in variation.	3. It helps in variation.
4. This process is common in bisexual flowers.	4. This process is common in both unisexual and bisexual flowers.

9.    Mention any two advantages of sexual reproduction.

Ans: Any two advantages of sexual reproduction are mentioned below:

i) It helps in evolution.

ii) It gives continuity to the generations.

iii) It causes the genetic variation.

10.  Write any two differences between ovum and zygote.

Ovum	Zygote
1. It is a female gamete having haploid chromosomes.	1. It is a fertilized ovum having diploid chromosomes.
2. It is formed by oogenesis.	2. It is formed after fertilization.

11.   How many chromosomes are there in ovum and zygote and why?

Ans: Ovum contains haploid (n) and zygote contains diploid (2n) number of chromosomes because ovum is formed by meiosis cell division and zygote is formed by fusion of two haploid (n) gamete.

12.  Differentiate between:

A) Asexual reproduction and sexual reproduction.

Asexual reproduction	Sexual reproduction
1. It takes place without fusion of a male gamete and a female gamete.	1. It takes place by the fusion of a male gamete and a female gamete.
2. Only single parent is involved in asexual reproduction.	2. Both parents are involved in sexual reproduction.
3. Variation in offspring cannot be observed.	3. Variation in offspring can be observed.

13.   What is the significance of sexual reproduction in the evolution of organism

Ans:  Sexual reproduction causes the variation and favorable variation transmits from generation to generation. Thus, it helps in the evolution of organism.

14.  "Offspring produced by asexual and sexual reproduction process are dissimilar." Why?

Ans: In asexual reproduction, crossing over does not take place and gametes are not produced. So, offspring produced by asexual reproduction are genetically identical to the parent. But in case of sexual reproduction, crossing over takes place during the formation of gametes. So variation occurs in offspring.

15.   "Vegetative propagation is beneficial to the farmers." Give any two reasons to justify the statement.

Ans: Vegetative propagation is beneficial for farmers because of the following reasons:

i) Gardeners, farmers and botanists can grow a large number of plants by this method.

ii) The plants which do not produce viable seeds like rose, sugarcane, potato, etc. can easily be propagated by this method.

16.  How many chromosomes are there in human sperm and zygote?

Ans: There are 23 pairs of chromosomes in human sperm and 23 pairs of chromosomes in human zygote.

17.  What type of asexual reproduction takes place in yeast, potato, euglena and mushroom?

Ans:      Yeast - Budding

Potato - Vegetative propagation by stem

Euglena - Binary fission

       Mushroom - Sporulation