Questions: All of the following are found in some or all protozoa except (A) cell walls. (B) motility. (C) ectoplasm and endoplasm. (D) formation of a cyst stage. (E) heterotrophic nutrition.

The answer is (A): cell walls.

Explanation for each option:

(A) Cell walls: Protozoa do not have cell walls. This is a characteristic feature that distinguishes them from other microorganisms like bacteria and fungi, which do have cell walls. Protozoa typically have a flexible cell membrane.

(B) Motility: Many protozoa exhibit motility through various structures such as flagella, cilia, or pseudopodia. This is a common feature in protozoa, allowing them to move in their environment.

(C) Ectoplasm and endoplasm: Protozoa have a differentiated cytoplasm, with ectoplasm being the outer, more rigid layer, and endoplasm being the inner, more fluid part. This differentiation is found in many protozoa.

(D) Formation of a cyst stage: Many protozoa can form cysts, which are a dormant, resistant stage that helps them survive unfavorable conditions. This is a common survival strategy among protozoa.

(E) Heterotrophic nutrition: Protozoa are generally heterotrophic, meaning they obtain their nutrients by ingesting other organisms or organic matter. This is a defining characteristic of protozoa.

Summary: Protozoa do not have cell walls, which is why the correct answer is (A). All other options describe features that are found in some or all protozoa.