Question

First photoautotroph organism was

• A. Bryophytes
• B. Algae
• C. Cyanobacteria
• D. Bacteria

Answer 1

The correct option is D

Bacteria

Correct option is D:

The explanation of the correct option

1. Organisms that can make their own food in the presence of sunlight are called photoautotrophs.
2. Due to less amount of organic molecules, the first photoautotrophs were dependent on inorganic molecules for their energy need.
3. They used inorganic molecules to make their food in the presence of sunlight, so they did not release oxygen while making their food.
4. Therefore first photoautotrophs were nonoxygenic photoautotrophs.
5. Bacteria were the first nonoxygenic photoautotrophs.

The explanation of the incorrect option

Option A

Bryophytes are oxygenic photoautotrophs, but the first photoautotrophs are nonoxygenic photoautotrophs, so they cannot be the first photoautotroph.

Option B

Algae are also oxygenic photoautotrophs, so they cannot be the first photoautotroph.

Option C

Cyanobacteria were the first oxygenic photoautotroph. They released oxygen while making their food in sunlight.

Final Answer: Bacteria were the first autotroph.