Chapter 19, Problem 24A

Summary Introduction

Introduction :

The given image is of a diatom. Diatoms are a group of microalgae found in the waterways, oceans, and soils. They are unicellular and found either in colonies or as solitary cells. They have two different shapes: some are radially symmetric and most of the diatoms are broadly symmetric. Diatoms transform the light energy into chemical energy by the process of photosynthesis, similar to the plants. Diatoms have a unique feature that their cell wall is made up of silica which is known as a frustule.

Answer to Problem 24A

Correct answer :

The correct answer is option (B) oil.

Explanation of Solution

Explanation/justification for the correct answer :

Option (B) oil. Diatoms are autotrophs that produce their food by performing photosynthesis. They perform photosynthesis by using the pigments chlorophyll and carotenoids that give them their golden yellow color. They store their excess food material in the form of oil rather than carbohydrates. Oil is less dense than the water, therefore, diatoms can float near the water surface and can easily absorb sunlight for the process of photosynthesis. So, the correct answer is option (B).

Explanation for incorrect answer :

Option (A) cellulose. Cellulose is a substance that contains carbon, oxygen, and hydrogen atoms. It is the main component of the plant cell walls. Cellulose is found in the cell wall of diatoms. It is not stored in the diatoms as excess food material. So, this is an incorrect option.

Option (C) protein. The proteins are polymers of amino acids. protein is not produced as a food material in algae. The food material produced by the autotrophs is usually carbohydrate. These food materials are not stored as excess food material in the form of proteins. So, this is an incorrect answer.

Option (D) Carbohydrate. Carbohydrate is the food material which is produced by the autotrophs after the process of photosynthesis. Most of the autotrophs store their excess food material in the different forms of carbohydrate. But diatoms store their food material in the form of oil instead of carbohydrate. So, option (D) is also incorrect.