Nucleus
True nucleus with chromosomes. Ciliates famously keep a macronucleus and a micronucleus.
A ciliate is a swimming mouth: oral cilia sweep bacteria into a gullet. An amoeba hugs prey with pseudopodia. Some dinoflagellates photosynthesise and still hunt.
Parasitic cycles can need a mosquito and a human, or a tsetse fly and a cow. Those maps are public-health geography, not laboratory recipes.
Parts
Mitochondria or remnants
Giardia's mitosomes show even 'amitochondriate' parasites keep organelle fossils.
Pellicle or test
A flexible protein coat or a shell of silica or calcium in radiolarians and foraminifera.
Motile organelles
Eukaryotic flagella are 9+2 microtubules — not bacterial flagella, not viral fibres.
Contractile vacuole
Freshwater species pump out water. A textbook organelle of osmoregulation.
Apical complex (apicomplexa)
Plasmodium's invasion kit. Named in textbooks; not a construction guide.
Life cycle
1Trophic feeding
The active cell eats, photosynthesises or absorbs. This is the form Leeuwenhoek watched.
2Binary fission or sex
Many split in two. Ciliates conjugate. Apicomplexans have named sexual stages in hosts.
3Cyst or spore wait
A thick wall waits for a new pond — or, in parasites, a new host. Survival, not a culture tip.
4Transmission ecology
Water, food, insects, sex in a few parasites. Public maps, not how-to.
Cysts let some species wait out dryness. Boiling or certified filters are the household language — not how to grow a parasite.
Keep exploring
More in Tree of microbes
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Single-celled prokaryotes with cell walls ? the oldest widespread life form, and both partners and pathogens.
Familiarity 95Viruses
Packets of DNA or RNA that are not cells — they replicate only inside living hosts.
Familiarity 96Fungi
A eukaryotic kingdom of yeasts, moulds and mushrooms — chitin walls, external digestion, partners of plants.
Familiarity 80Archaea
A prokaryotic domain that is not bacteria — methanogens, extremophiles and no known human pathogens.
Familiarity 35Bacteriophages
Viruses that infect bacteria — Earth's most abundant biological entities, and a concept-level idea in medicine.
Familiarity 42