--- title: "Protists: the eukaryotes that are not plants, animals or fungi" description: "Protists are diverse eukaryotes informally grouped outside animals, land plants and fungi. They include feeding, photosynthetic and mixed lifestyles. Their cell structures and genes provide evidence o" canonical: https://lightmysky.com/learn/science/protists-the-eukaryotes-that-are-not-plants-animals-or-fungi-mt_CHb8H727nW source: https://lightmysky.com/learn/science/protists-the-eukaryotes-that-are-not-plants-animals-or-fungi-mt_CHb8H727nW.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Protists: the eukaryotes that are not plants, animals or fungi Protists are diverse eukaryotes informally grouped outside animals, land plants and fungi. They include feeding, photosynthetic and mixed lifestyles. Their cell structures and genes provide evidence of bacterial organelle origins, later organelle loss and uptake of photosynthetic eukaryotes. Subject: Science · Area: Organisms & Life Processes · Ages 18 to 19 Page: https://lightmysky.com/learn/science/protists-the-eukaryotes-that-are-not-plants-animals-or-fungi-mt_CHb8H727nW ## Ready when they can - Explain the bacterial origins of mitochondria and plastids using genetic and cellular evidence, recognising host dependence and later organelle loss. - Describe contrasting protist lifestyles and the cell structures used for feeding and photosynthesis. - Explain why the informal category protist is not a clade containing an ancestor and all its descendants. ## Lesson: Protists and the origins of organelles Here, protist is an informal name for eukaryotes outside animals, land plants and fungi, including algae. Many protists are single-celled; others form colonies or multicellular bodies. They do not form one clade. A clade contains an ancestor and all its descendants. Some protists are closer relatives of animals or fungi than of other protists. Excluding those descendants prevents the category from forming a clade. Endosymbiosis is a relationship in which one organism lives inside another. Mitochondria descended from bacterial partners related to alphaproteobacteria. Plastids descended from cyanobacteria; photosynthetic plastids are chloroplasts. Over many generations, these partners became integrated organelles, and many genes moved to the host nucleus. Details of the initial mitochondrial partnership remain uncertain. *(drawing: Integration took many generations. The bacterial partner did not remain an independent organism.)* Gene comparisons link mitochondria to alphaproteobacteria and plastids to cyanobacteria. Typical mitochondria and chloroplasts retain DNA and bacterial-like ribosomes. They grow and divide from existing organelles, but depend on host proteins and regulation. Mitochondria and primary plastids have two surrounding membranes. Some plastids acquired through later endosymbiosis have additional membranes. Comparisons across eukaryotic lineages support a last common ancestor with mitochondria. Some descendants later reduced or lost them. Plastids arose later in particular branches. Present distribution contributes evidence when combined with genetic relationships. Distribution alone cannot prove acquisition order: loss can remove an ancestral organelle. An organism lacking mitochondria need not represent a stage before their acquisition. An amoeba uses pseudopodia, temporary cell projections, to surround prey. The enclosed prey enters a food vacuole, where digestion occurs. Photosynthetic protists use chloroplasts to capture light energy and make organic molecules. Some protists combine photosynthesis with feeding, called mixotrophy. The balance depends on species and conditions; it is not a rule that all protists switch feeding methods when light changes. *(drawing: Pseudopodia capture prey; the food vacuole contains it during digestion.)* Primary plastid endosymbiosis involved a host acquiring a cyanobacterium. In secondary endosymbiosis, a eukaryotic host acquired an alga that already had a plastid. Some secondary plastids retain extra membranes and a remnant algal nucleus. Together, these features support uptake of a eukaryotic alga. Later losses mean that not every secondary plastid retains the same membrane count or a nuclear remnant. **Recap.** Protists span different lineages. Genes and cell structures reveal bacterial organelle ancestry, host dependence, later losses and uptake of algae. *Teaching text, questions and flashcards written for this dataset. OpenStax Biology 2e chapter 23 was consulted for organelle ancestry and protist diversity.* ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Prokaryotic and Eukaryotic Cells](https://lightmysky.com/learn/science/prokaryotic-and-eukaryotic-cells-mt_vlL4GinuH6) ## Optional connections - [Single-Celled Organisms](https://lightmysky.com/learn/science/single-celled-organisms-mt_g9RcQOhU5d) ## Opens up - [Fungi: Hyphae, Spores and Digestion Outside the Body](https://lightmysky.com/learn/science/fungi-hyphae-spores-and-digestion-outside-the-body-mt_qfp2nuk1IH)