Question

Motile zoospores are produced by
A. Chlamydomonas
B. Penicillium
C. Bacteria
D. Amoeba

Answer 1

Hint: Zoospores are naked motile spores. They are asexual reproductive units which are capable of growing independently. They are formed in lower plants like algae and few fungi. They germinate with the onset of favourable conditions.

Complete answer:
Zoospore formation is commonly observed in many members of algae like Chlamydomonas, Ulothrix, Cladophora, etc. and also in some members of fungi like Saprolegnia, etc. During zoospore formation plants withdraw their flagella and enter into a resting phase. The vacuoles and neuromotor apparatus disappear. The protoplasm recedes from the cell wall and undergoes repeated mitotic divisions. The cell contents get divided evenly and as a result, 4, 8 or 16 uninucleated daughter protoplasts are formed. These daughter protoplasts change into oval or round bodies called zoospores. Each zoospore has its own set of vacuoles, chloroplast, and an eyespot.

Zoospores develop within the zoosporangium. These are liberated in water either due to the rupture of sporangial wall or formation of an apical pore in the sporangium. Each naked zoospore soon after its release develops a cell wall and flagella. The movement of flagella helps the zoospore to swim in water and find a suitable substratum for further growth. Zoospores of Chlamydomonas are biflagellate and exact replicas of their parent cell. They enlarge their cell and develop into an adult cell.

Hence, the correct answer is option (A).

Note: A zoosporangium may contain a single zoospore like in Oedogonium or may have many zoospores like in Ulothrix, Chlamydomonas, Cladophora, etc. In some genus, zoospores can be either biflagellated or quadriflagellated like in Ulothrix whereas, in Oedogonium, they are multi flagellated. In Vaucheria, zoospores are both multinucleate and multiflagellate, hence are called syn-zoospores.