Question

How do most unicellular algae get food? How does this differ from the way most protists get food?

Answer 1

Hint: Algae are a diverse group of aquatic organisms that usually can conduct photosynthesis. Certain algae are familiar to most of the people; for instance, seaweeds (such as the kelp or phytoplankton), pond scum or the algal blooms in lakes. Some algae form very close partnerships with fungi to form the lichens. Unusual algal habitats are usually the hairs of the South American sloth and polar bears.

Complete answer:
All algae usually contain a pigment called chlorophyll a (some other types of chlorophyll such as b, c and/or d may also be present) and have to make their food by photosynthesis. The chlorophyll is contained or stored in the chloroplasts and gives many algae their green appearance.
However, some algae appear brown, yellow or red because in addition to chlorophylls they have some other accessory pigments that camouflage the green colour. Some of the fungus-like the protists, such as the slime molds decompose the decaying matter. The animal-like protists need to "eat" or ingest food.
Some animal-like protists use their "tails" to eat. These protists are called the filter-feeders. They acquire some nutrients by constantly whipping their tails, called a flagellum, back and forth. The whipping of the flagellum usually creates a current that brings food into the protist.
Other animals-like the protists need to"swallow" their food through a process called endocytosis. Endocytosis happens when a cell takes in substances through its membrane.
The protist usually wraps around its prey, which is mostly bacteria. It creates somehow food vacuole, a sort of "food storage compartment," around prey bacteria. The protist produces some toxins which paralyze its prey.
Once digested, the food material usually moves through the vacuole and into the cytoplasm of the protist.

Note: Also, some of the animal-like and fungi-like protists are usually parasitic, harming their hosts as they obtain their nutrients. Fungi-like protists absorb nutrients meant for their host, harming the host in the process.