What is the model organism used to study fundamental biological processes like growth, differentiation, cytoplasmic streaming, and cytoskeleton function?

A biologist was studying some groups of protozoa when he noticed details of some of the organisms of this kingdom, which one pair is mismatched?

A Dutch scientist first observed very small creatures in:

A group of producers second only to diatoms

A sessile ciliate

A student studied a drop of pond water with the low power of compound microscope and made the following exact drawing of an organism she observed, Which kingdom is the organism classified as?