Question

An example of a filamentous green alga is
A. Chlamydomonas
B. Volvox
C. Spirogyra
D. Fucus

Answer 1

Filamentous algae are single-celled algae characterized by long visible chains, loops or filaments. Based on the morphology of their vegetative or developing state, the algae may be classified into many classes. An example of a filamentous green alga is water silk.

Complete answer: Filamentous algae are a group of microscopic organisms that develop threads or mesh-like filaments which connect together. Typically, such primitive organisms grow underwater, on the surface of hard objects or other substrates, but they may break loose and form floating mats. Some filaments are unbranched (e.g., Spirogyra), while others are branched and bush-like (e.g., Stigeoclonium). As stormwater ponds capture water flowing from town yards and highways, due to the many sources of nutrients in residential and commercial projects, they also contain an abundance of algae. It is not unusual for stormwater ponds to develop large floating algae mats in response to the fertilization of lawns and animal waste in the watershed during the warm months of the year. Filamentous algae need to provide oxygen and food to the animals living in the pond, but they can also cause problems such as clogging and stagnation. Filamentous algae have no roots; instead, they get their nutrients directly from the water, which means that their growth and reproduction depend entirely on the number of nutrients in the water (i.e., fertilizers). Spirogyra is an example of filamentous algae.
So, the correct answer is option C.

Note: Algae limit the exchange of oxygen between the water and the atmosphere and prevent photosynthesis from producing oxygen in the water as mats of filamentous algae grow to the point that they cover large areas of the pond surface. As a result, because of lack of oxygen, ponds that are mainly filled by algal mats are more likely to kill fish and have a poisonous odour.