Why do fishes in an aquarium thrive better if green plants are growing there?

Select the correct option:
$(1)$ $C_4$ plants have double the efficiency of carbon fixation compared to $C_3$ plants.
$(2)$ Sugar is transported from source to sink through the $\text{phloem}$ / $\text{xylem}$ tissue.

When green algae are illuminated,motile aerobic bacteria usually accumulate near them. This is because,bacteria

According to an estimate,how much carbon is fixed annually in the biosphere through photosynthesis?

Differentiate between $C_3$ and $C_4$ plants.

In which of the following cell organelles do both photo-chemical and thermo-chemical reactions occur?