Kingdom Protista

Understand the idea

Protista comes from a Greek word meaning ‘the very first’. These organisms are eukaryotes: they have a nucleus and membrane-bound organelles. Most are unicellular. Many live in water, soil, or damp places. They are treated as the first eukaryotic forms, before plants, animals, and fungi.

Some protists make their own food; others feed on other organisms. A few are multicellular. Giant kelp can grow taller than 100 feet. Kelp forests can shelter otters, and otters eat sea urchins that would otherwise destroy the kelp. That is a living partnership.

Movement may use cilia, flagella, or pseudopodia. Trypanosoma is a parasitic protist that causes sleeping sickness. Reproduction is usually asexual; sexual reproduction is rare and often happens under stress.

What to remember

• Protists are eukaryotes, usually unicellular, often aquatic.
• Nutrition: autotrophic or heterotrophic.
• Trypanosoma causes sleeping sickness.

Recap

Protists are the eukaryotic ‘first’ kingdom: mostly one cell, true nucleus, mixed nutrition, and several ways to move. Know kelp and Trypanosoma as named examples.