All the reproductive methods of living organisms are broadly categorized into two types: 1. Asexual reproduction, and 2. Sexual reproduction.

Asexual reproduction involves the participation of a single parent without the formation of gametes, fertilisation and transfer of genetic material. This method is a common means of rapidly increasing offsprings under favourable conditions.

(a) Name the type of fission that occurs in Leishmania and Plasmodium.

(b) Write one advantage of sexual mode of reproduction over asexual reproduction.

(c) Give reasons why:

(i) Colonies of yeast fail to multiply in water but multiply in sugar solution.

(ii) Rhizopus individuals do not grow on a dry slice of bread.

OR

(c) Name the filamentous structures a student could identify when he collected water from a pond that appeared dark green. How do these organisms multiply? Explain.

(a) The type of fission that occurs in Leishmania is binary fission, while in Plasmodium it is multiple fission.

(b) Sexual mode of reproduction provides more variations in the offspring due to the shuffling of genes during meiosis and fertilisation, which increases the chances of survival of the species in a changing environment.

(c) (i) Yeast colonies fail to multiply in water because they require a source of energy, which is provided by the sugar solution. Yeast can ferment sugars to produce energy.

(ii) Rhizopus individuals do not grow on a dry slice of bread because they require moisture to grow and multiply. Rhizopus is a fungus that grows in damp environments.

OR

(c) The filamentous structures that the student could identify are the hyphae of Spirogyra. Spirogyra multiplies by fragmentation, where the filaments break into smaller pieces, each of which can grow into a new individual.