Notes
Naming and classifying
- Levels: Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
- Binomial nomenclature: Genus species (e.g. Homo sapiens).
- Dichotomous keys identify organisms; cladograms show evolutionary relationships.
Three domains
| Domain | Cell type | Notes |
|---|---|---|
| Bacteria | Prokaryote | Peptidoglycan cell walls |
| Archaea | Prokaryote | Often in extreme environments |
| Eukarya | Eukaryote | Protists, fungi, plants, animals |
Viruses and bacteria
- Bacteria are alive; they reproduce by binary fission, and many are helpful. Antibiotics kill bacteria.
- Viruses are DNA or RNA in a protein coat. They are not cells and need a host cell to reproduce. Antibiotics do not work on them; vaccines help prevent them.
Eukaryote diversity
- Protists: mostly single-celled; algae, protozoa, slime molds.
- Fungi: heterotrophs that absorb food; chitin walls; decomposers.
- Plants: nonvascular (mosses), seedless vascular (ferns), gymnosperms (cones), angiosperms (flowers and fruit). Xylem carries water; phloem carries sugar.
- Animals: invertebrates (95% of species, including arthropods) and vertebrates. Most show bilateral symmetry.
Topics in this unit
Each topic has its own short notes and practice.
Practice
The first part of a scientific name is the genus.
The order is domain, kingdom, phylum, class, order, family, genus, species.
A single-celled eukaryote that photosynthesizes is a plant-like protist (alga).
Viruses have DNA or RNA; only bacteria are cells.
Gymnosperms have vascular tissue and seeds in cones, not fruit.
Amphibians rely on outside heat; birds and mammals are endotherms.
Free response
Write your answer first, then open the scoring guide.
Free-response question
A student uses this dichotomous key to identify four pond organisms. 1a: has a nucleus, go to 2. 1b: no nucleus, Organism W (bacterium). 2a: makes its own food with chloroplasts, Organism X (alga). 2b: does not make its own food, go to 3. 3a: single-celled, Organism Y (amoeba). 3b: multicellular, Organism Z (water flea).
(a) A sample has a nucleus, no chloroplasts, and is made of many cells. Identify it and give its kingdom.
Show the answer and scoring guide
Following 1a, 2b, 3b, it is Organism Z, the water flea. It belongs to kingdom Animalia, since it is a multicellular heterotroph.
Check off the points you earned:
(b) Which organisms belong to domain Eukarya? Explain.
Show the answer and scoring guide
Organisms X, Y and Z belong to Eukarya because they have a nucleus. Organism W has no nucleus, so it is a prokaryote in domain Bacteria.
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(c) The student also finds a virus in the water. Explain why it cannot be placed in this key.
Show the answer and scoring guide
The key sorts cells by having a nucleus, chloroplasts, and one or many cells. A virus is not a cell; it is genetic material in a protein coat and cannot live or reproduce on its own, so it does not fit any choice.
Check off the points you earned: