Question

reproduction in animals answer with a diagram

Answer 1

Some animals produce offspring through asexual reproduction while other animals produce offspring through sexual reproduction. Both methods have advantages and disadvantages. Asexual reproduction produces offspring that are genetically identical to the parent because the offspring are all clones of the original parent. A single individual can produce offspring asexually and large numbers of offspring can be produced quickly; these are two advantages that asexually reproducing organisms have over sexually reproducing organisms. In a stable or predictable environment.

Answer 2

1. Asexual Reproduction:

In this type of reproduction neither the sex cells (nor gametes) are formed nor do they unite to form the zygote. Moreover, the participation of two organisms (male and female) is not required, only one organism reproduces. During asexual reproduction the body (somatic) cells divide, their nucleus divides either by mitosis or amitosis, therefore, such type of reproduction is also known as somatogenic or blastogenic reproduction. The asexual reproduction is commonly found in lower animals such as protozoans, sponges, coelenterates, certain worms and tunicates.

1. Binary fission

2. Multiple fission

3. Gemmulation

4. Budding

5. Fragmentation

6. Regeneration.

Advantages of Asexual Reproduction:

1. A large number of individuals are produced within a short period from a single parent.

2. The offspring’s are genetically identical to the parent.

3. It occurs only through simple mitotic division.

4. It helps in dispersal of young ones to far off places.

5. It also helps the animal to tide over unfavourable environmental conditions.


Disadvantages of Asexual Reproduction:

1. Continuous binary fission for several generations makes the daughter individuals genetically weak and requires rejuvenation.

2. Animals produced by asexual reproduction are generally less adaptable to changing environmental conditions.

3. Since the genetic constitution of the daughter individuals is similar to the parent there is no genetic variation in the offspring’s and hence does not contribute to speciation.

2. Sexual Reproduction:

Sexual reproduction is commonly found in the complex, multicellular organisms. It involves the union of male and female sex cells or gametes to form the zygote which grow into a new individual. Two different sexes (male and female) take part in the process. The testes in male produce male gametes or sperms and the ovaries in female produce female gametes or ova.

Both these sex organs may be present in the same body. Such animals are known as bisexual or hermaphrodite animals, e.g. earthworm. Formation of sperms and ova involves meiosis or reduction division during which haploid gametes are formed from the diploid cells. Gametes vary in shapes and sizes in different animals.

Fusion of male and female gamete is known as fertilization. During fertilization a haploid (n), motile male gamete or sperm fuses with a non- motile, haploid (n) female gamete or ovum to form a diploid (2n) zygote which gives rise to a new individual

Advantages of Sexual Reproduction:

1. The offspring’s produced due to sexual reproduction adapt themselves successfully to the changing environmental conditions.

2. Formation of gametes by meiosis and their fusion during fertilization produce reshuffling of genes and variation in the offspring’s. Variations in the offspring’s help them in natural selection and evolution.


Disadvantages of Sexual Reproduction:

Since two parents of opposite sexes are needed i.e., biparental reproduction (except hermaphrodite forms) it is not as easy or as frequent as asexual or uniparental reproduction.