Groups of organisms
Groups of organisms
- The animal kingdom splits first into vertebrates and arthropods.
- Plants split into ferns and flowering plants.
- Viruses fit in no kingdom at all.
Vertebrates
Animals with a backbone, in five groups:
| Group | Key features |
|---|---|
| mammals | fur/hair; feed young on milk |
| birds | feathers, beak; hard-shelled eggs |
| reptiles | dry scaly skin; leathery-shelled eggs |
| amphibians | moist skin; eggs in water |
| fish | wet scales, fins, gills |
Practice
Which feature is typical of mammals?
Mammals have fur/hair and feed their young milk; the others describe birds, amphibians and fish.
Arthropods
Animals with no backbone, an exoskeleton and jointed legs:
| Group | Key features |
|---|---|
| insects | 3 body parts; 3 pairs of legs; usually wings |
| arachnids | 2 body parts; 4 pairs of legs; no wings |
| crustaceans | many legs; 2 pairs of antennae |
| myriapods | many segments, legs on each |
Practice
An insect has:
Insects: 3 body parts, 3 pairs of legs, usually wings and one pair of antennae. Arachnids have 2 parts and 4 leg pairs.
Plants and viruses
- ferns: roots/stems/leaves but no flowers/seeds — reproduce by spores.
- flowering plants: monocots (one cotyledon, parallel veins) vs dicots (two cotyledons, net veins).
- viruses: not cells, no kingdom — just a protein coat around genetic material; only reproduce inside a host.
Practice
A monocotyledon has:
Monocots: one seed-leaf, parallel veins. Dicots: two seed-leaves, branching net veins.
Practice
A virus consists of:
Viruses are not cells — just a protein coat with genetic material; they reproduce only inside a host.
You've got it
Key idea
- vertebrates (backbone): mammals, birds, reptiles, amphibians, fish
- arthropods (exoskeleton, jointed legs): insects (3 parts/3 leg pairs), arachnids (2 parts/4 leg pairs), crustaceans, myriapods
- plants: ferns (spores) vs flowering (monocot/dicot)
- viruses = protein coat + genetic material, no kingdom