Question

Photosynthetic autotrophs get their energy requirement from
A. Heat
B. Light
C. Inorganic chemicals
D. Organic chemicals

Answer 1

Hint: They are also known as primary producers that synthesize complex organic compounds from simple substances.

Complete answer:
Photosynthetic autotrophs use energy from light to convert water and carbon dioxide into a nutrient called glucose. Photosynthetic autotrophs include green plants, certain algae, and photosynthetic bacteria. Food synthesized by the autotrophs provides both the energy to do work and the carbon to build bodies. Photosynthesis provides approximately 99% of the energy for life on earth.

Additional information:
Chemosynthetic autotrophs:
- It is a very small group of autotrophs that uses chemical energy stored in inorganic molecules like hydrogen sulphide, methane, and ammonia.
- Some of the chemosynthetic bacteria are found in the deep ocean.
- They use the energy in the form of gases found in the earth’s interior to produce food.
- Chemosynthetic autotrophs play an important role in maintaining certain biogeochemical cycles like nitrogen, phosphorus, and Sulphur cycle in the environment.

Heterotrophs:
- All the consumer comes under the heterotrophs.
- They cannot synthesize their own food by carbon fixation and hence, depends on other sources like plants and animals.
- They include all animals, fungi, and many protists and bacteria.
- Heterotrophs are placed as secondary and tertiary consumers in the food chain.

So, the correct answer is ‘light’.

Note:
- The cells present in a middle layer of leaf tissue known as mesophyll are the primary site of photosynthesis.
- The reactions of photosynthesis are carried out in chloroplasts that are present in the mesophyll cell.
- Large quantities of carbon dioxide are removed by photosynthetic organisms from the environment.