Protists: The Eukaryotes That Are Not Plants, Animals or Fungi
Most eukaryotic diversity sits outside the three familiar kingdoms, in lineages that photosynthesise, hunt, or do both depending on the light. Their organelles record a history of one cell taking up another, which is why they are the evidence for endosymbiosis rather than an afterthought to it.
What a learner can do afterwards
- Explain the endosymbiotic origin of mitochondria and plastids and state the evidence for each
- Describe two contrasting protist lifestyles and the cell structures each depends on
- Say why the word protist describes a grade of organisation rather than a natural group
1 · Read
All life sorts into Archaea, Bacteria, and Eukarya, and eukaryotes arose about 2 billion years ago. One cell swallowed another and kept it as the mitochondrion, and later some cells swallowed sunlight users that became chloroplasts.
Both partners still betray their past: they carry their own DNA, wear two membranes, and divide on their own like free bacteria. All eukaryotes keep mitochondria or their traces, while only some lines keep plastids, which is why mitochondria joined first.
Some protists hunt and engulf food, others trap sunlight with chloroplasts, and some switch with the light. Hunters lean on gear that catches food, while sunlight users lean on their captured chloroplasts.
Protist names a level of organisation, not one family, since its members branch from many points of the tree. Never treat it as a single branch.
Swallowed cells became powerhouses and plastids, and protists show that mixed history across many branches.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.