Which of the following feed on dead plant and animal tissues?
A. Spirogyra
B. Mushroom
C. Chlamydomonas
D. Chlorella

Hint: Each and every plant and animal requires nutrients for survival and development. However, the mode of nutrition varies greatly among different species, depending on the presence or absence of pigments called chlorophyll and other characters intrinsic to that species. Let us try to understand more to find the correct answer.

Complete answer:
Let us know about the options given:
Spirogyra: It is a charophyte green algae. It is filamentous and has spiral or helical arrangement of chloroplasts. Thus, it contains chlorophyll and has an autotrophic mode of nutrition.
Mushroom: It belongs to the kingdom fungi. It has no chlorophyll of its own and thus cannot make food by photosynthesis. Its mode of nutrition is saprophytic and thus, it obtains its nutrients from dead and decaying matter.
Chlamydomonas: It is also a green algae and belongs to the phylum Chlorophyta and thus, it also contains chlorophyll. So it can also make its own food through the process of photosynthesis.
Chlorella: It is a genus containing single-celled green algae and belongs to the division Chlorophyta. Its chloroplasts contain green photosynthetic pigments, chlorophyll-a and chlorophyll-b. Thus it can also make its own food.

From the above description, it is clear that the correct answer is (B)- Mushroom.

Note:
Chlorella and spirulina are algal forms having high nutritious value and thus provide a good source for SCP (Single cell proteins). Chlamydomonas are also used for SCP production. Not all mushrooms are edible. Some non- edible mushrooms are so dangerous that if consumed can prove lethal.