Question

Asexual reproduction through formation of gemmule occurs in
a. Ascidian
b. Hydra
c. Planaria
d. Spongilla

Answer 1

Asexual reproduction is one of the types of reproduction where offspring are formed by simple division from the parent, some times the parent organism itself undergo division or fragmentation and produce the offspring, and this process is also called as cloning, as only particular clones are produced.

Complete answer:
- There are different types of asexual reproduction which takes place in plants and animals.
- There are advantages and disadvantages to this type of reproduction.
- Some advantages include, they can inherit the good things continually but the disadvantage is that there is no genetic diversity and there is a chance of accumulation of mutants, and fewer variations occur.
- When coming to gemmules, they are mainly found in the sponges which involved in the asexual reproduction.
- Generally, sponges reproduce asexually by budding, and this budding is again of two types such as external or internal.
- Internal buds are also called gemmules, this is the mass of cells, which are capable of developing into new organisms, which means that they can develop into new sponges.
- Only endogenous types of buds are capable of developing into new sponges.
- These gemmules have certain characteristics such as their resistance to dry environment or dehydration, and they are also resistant to freezing and lack of oxygen such as anoxia, for a long period of time.
- This gemmules are generally similar to bacterial endospores and are made up of amoebocytes, which are surrounded by a layer of Spicules where they also survive the conditions which can kill adult sponges, and this gemmule starts growing or resumes growing when the environment back to the favor.

Hence, the correct answer is option (D).

Note: These gemmules are found mainly in freshwater sponges and in some marine sponges also, when the conditions are unfavorable these freshwater sponges die by leaving numerous gemmules, where they survive all the unfavorable conditions and starts growing when they become normal.