Question

Which of the following about autotrophs is incorrect?
A. They synthesise carbohydrates from carbon dioxide and water in the presence of sunlight and chlorophyll.
B. They store carbohydrates in the form of starch.
C. They convert carbon dioxide and water into carbohydrates in the absence of sunlight.
D. They constitute the first trophic level in food chains.

Answer 1

Hint: The producers in the food chain are autotrophs, they generate their own nutrients and resources. Kelp generates energy by a mechanism called photosynthesis, like most autotrophs.

Complete Answer:
- An autotrophic or primary producer is an entity that utilises carbon from basic substances such as carbon dioxide to create complex organic compounds (such as carbohydrates, fats and proteins), usually utilising light energy (photosynthesis) or inorganic chemical reactions (chemosynthesis).
- Autotrophs do not need a living source of carbon or electricity, and are producers of the food chain, such as land-based plants or water-based algae (as opposed to heterotrophs as consumers of autotrophs or other heterotrophs).
- To render organic biosynthesis compounds and as Autotrophs can lower carbon dioxide by storing chemical fuel.
- Water is used as the reducing agent for most autotrophs, but others may use other hydrogen compounds, such as hydrogen sulphide.
- Some autotrophs, including green plants and algae, are phototrophs, which means that, in the form of glucose, they turn electric energy from sunlight into chemical energy. Others like methanogens, are chemotrophs which, as a source of energy, use organic or inorganic chemical compounds.
- The bulk of chemoautotrophs are lithotrophs, using inorganic electron donors such as carbon sulphide, carbon dioxide, elemental sulphide, ammonium and ferrous oxide as biosynthesis and chemical energy release reduction agents and hydrogen sources.

So the answer is “option C”.

Note: To reduce $NADP^+$ to NADPH to form organic compounds, autotrophs use a portion of the ATP produced during photosynthesis or the oxidation of chemical compounds.