Question

Well-defined nucleus is absent in

• A. Blue-green algae
• B. Diatoms
• C. Algae
• D. Yeast

Answer 1

The correct option is A

Blue-green algae

The correct option is A.

Explanation of correct option:

1. Blue-green algae are also known as cyanobacteria.
2. They lack a membrane-bound organelles such as mitochondria, Golgi apparatus, chloroplasts, and endoplasmic reticulum like all other prokaryotes.
3. They also lack a well-defined nucleus.
4. They are aquatic and photosynthetic so they live in the water, and can grow their own food.
5. They only contain one type of chlorophyll, chlorophyll a, a green pigment.
6. In addition, they also contain pigments such as carotenoids, phycobilin.
7. These algae grow naturally in marine and freshwater systems.
8. They thrive in dams, rivers, reservoirs, lakes and even in hot springs.
9. They normally look green and sometimes turn blue when scum are dying.

Explanation of incorrect options:

Option B:

1. Diatoms are single-celled algae living in glass houses containing freshwater are known as diatoms.
2. They have a well-defined nucleus.

Option C:

1. Algae is the group of aquatic, photosynthetic, nucleus-bearing eukaryotic organisms lacks true stem, leaves, and roots
2. They have a well-defined nucleus.

Option D:

1. Yeasts are fungal organisms, that are unicellular, eukaryotic, autotrophic, and anaerobic.
2. They have a well-defined nucleus.

Final answer: Well-defined nucleus is absent in blue-green algae.