Question

Cyanophyceae or blue-green algae possess
(a) Definite nucleus but no plastid
(b) Definite plastid but no definite nucleus
(c) Definite nucleus and plastid
 (d) Neither definite nucleus nor definite plastid

Answer 1

Hint: Type of photosynthetic bacteria consisting of either single cells or colonies are called blue-green algae. They are also known as cyanobacteria. They contain only one type of chlorophyll, a green pigment. In addition pigments like carotenoids and phycobilins are also present.

Complete answer:
Cyanophyceae or blue-green algae possess neither a definite nucleus nor definite plastid. Cyanobacteria are single-celled organisms that use sunlight to make their own food. They are found naturally in fresh and salt waters.
- Unicellular organisms without membrane-bound organelles like mitochondria; chloroplasts and plastids are called prokaryotes.
- They also lack a definite nucleus. Instead, they possess nucleoid i.e. genetic material without a nuclear envelope.
- Bacteria, cyanobacteria are some of the examples of prokaryotic organisms.
- Therefore cyanobacteria do not possess a definite nucleus as well as a plastid.
So, the correct option is ‘neither a definite nucleus nor definite plastid.’

Additional Information:
- Cyanobacteria grow naturally in marine and freshwater systems. They thrive in dams, rivers, reservoirs, lakes, and even in hot springs.
- These bacteria normally look green and sometimes turn blue when scums are dying.
- Almost all species of these bacteria are buoyant and float on the water surface and form floating mats.
- Their accumulation is termed as blooms. These blooms discolor the water and produce unpleasant taste and odor.
Examples of cyanobacteria are Nostoc, Spirulina, and Anabaena, etc.

Note: Blue-green algae contain small amounts of vitamin C, E, and folate. They are used as nutrient supplements and help in losing weight. They also help in boosting the immune system and controlling cholesterol levels.