Characteristics and Classification of Living Organisms
Features of Organisms
Cambridge IGCSE Biology
The kingdoms
| Kingdom | Main features |
|---|---|
| Animal | multicellular; no cell wall; no chloroplasts |
| Plant | multicellular; cellulose cell wall; chloroplasts containing chlorophyll; large permanent vacuole |
- The five kingdoms: animal, plant, fungus, prokaryote, protoctist.
- Protoctists and plants are the kingdoms whose organisms can have chloroplasts.
| Kingdom | Main features |
|---|---|
| Fungus | nucleus; mitochondria; cell wall not made of cellulose; body made of hyphae |
| Prokaryote | no nucleus; circular DNA; plasmids; cell wall |
| Protoctist | nucleus; membrane-bound organelles; linear chromosomes; some have chloroplasts |
Vertebrates
| Group | Body covering | Other features |
|---|---|---|
| Mammals | fur | external ears; lungs |
| Birds | feathers | wings; beak; lungs; hard-shelled eggs |
| Reptiles | dry scaly skin | leathery soft-shelled eggs; lay eggs on land; internal fertilisation; lungs |
| Amphibians | moist skin | eggs laid in water; larvae have gills and adults have lungs; adults live on land; gas exchange through skin |
| Fish | scales | fins; gills; operculum |
Arthropods
All arthropods have an exoskeleton, a segmented body and jointed legs.
| Group | Body | Legs | Antennae |
|---|---|---|---|
| Insects | three body regions: head, thorax and abdomen; usually wings | three pairs of legs | one pair of antennae |
| Crustaceans | gills | usually five pairs of legs | two pairs of antennae |
| Arachnids | two body regions | four pairs of legs | none |
| Myriapods | many body segments | legs on every segment | one pair |
Plants: ferns and flowering plants
- The plant kingdom contains ferns and flowering plants; flowering plants are monocotyledons and dicotyledons.
- Ferns: no flowers; reproduce by spores; leaves are fronds.
- Flowering plants have flowers and produce pollen, ovules, seeds and fruit.
| Feature | Monocotyledons | Dicotyledons |
|---|---|---|
| Seed leaves | one cotyledon | two cotyledons |
| Leaf shape | narrow leaves | broad leaves with a petiole |
| Veins | parallel veins | network of veins |
| Flower parts | multiples of three | multiples of five |
| Roots | fibrous | tap root |
| Vascular bundles | throughout the stem | in a ring |
Viruses
A virus is a protein coat around genetic material.
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