The following image is of a diatom. It lives in water and gets food from photosynthesis. It is encased in a hard shell made of something similar to glass or sand.

Image by Damián H. Zanette

A diatom is a(n) because it has .

A diatom is a(n) autotrophic algae because it has chlorophyll.

Explanation:

Diatom is a type of unicellular and eukaryotic algae which has the ability to make their own food like plants from sunlight due to the presence of chlorophyll pigment. Diatom helps in fixation of carbon in the process of photosynthesis. About 20 percent of carbon fixes by diatom and plays an important role in climate change. It lives in water and provides food for many herbivores.