Question

Aquatic plants use ${\mathrm{CO}}_2$ dissolved water for:

• A. breakdown of toxic materials
• B. respiration
• C. excretion
• D. photosynthesis

Answer 1

The correct option is D

photosynthesis

The explanation for the correct option:

(D) Photosynthesis: The process of conversion of light energy into chemical energy by plants, algae and certain bacteria using Carbon dioxide (CO₂) and water.

$\underset{(\mathrm{Carbon}\mathrm{dioxide})}{6{\mathrm{CO}}_2\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Water}\right)}{2{\mathrm{H}}_2\mathrm{O}}\left(\mathrm{l}\right)\stackrel{\mathrm{Sunlight}}{\to }\underset{\left(\mathrm{Glucose}\right)}{{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left(\mathrm{aq}\right)}+\underset{\left(\mathrm{Oxygen}\right)}{6{\mathrm{O}}_2\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Water}\right)}{6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

• Carbon dioxide is present in water as a dissolved gas.
• It has a high solubility in water and can dissolve in water 200 times more easily than oxygen.
• Aquatic animals like fish depend on dissolved Oxygen $\left({\mathrm{O}}_2\right)$ gas whereas aquatic plants depend on dissolved carbon dioxide for life and growth.
• Plants use this carbon dioxide dissolved in water for the process of photosynthesis.

The explanation for the incorrect options:

(A) Breakdown of toxic materials: It occurs using water or light and by the use of microbes that decompose the waste and toxic materials present in the environment.

(B) Respiration: It is a process of oxidation of food to release energy using Oxygen.

$\underset{\left(\mathrm{Glucose}\right)}{{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6(\mathrm{aq}})+\underset{\left(\mathrm{Oxygen}\right)}{6{\mathrm{O}}_2\left(\mathrm{g}\right)}\to \underset{(\mathrm{Carbon}\mathrm{dioxide})}{6{\mathrm{CO}}_2\left(\mathrm{g}\right)}+\underset{\left(\mathrm{Water}\right)}{6{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}+\mathrm{Energy}$

(C) Excretion: It is a process of removal of wastes from the body of animals.

Hence, option (D) is correct.