1.3 Features of organisms
- Syllabus
- 0610–2026–2027
- Topic
- 1.3
- Level
- —
Learning objectives
1.3.1Main features used to place animals• State the main features used to place animals and plants into the appropriate kingdoms1.3.2Main features used to place organisms• State the main features used to place organisms into groups within the animal kingdom, limited to: (a) the main groups of vertebrates: mammals, birds, reptiles, amphibians, fish (b) the main groups of arthropods: myriapods, insects, arachnids, crustaceans1.3.3Classify organisms using the features• Classify organisms using the features identified in 1.3.1 and 1.3.21.3.4Main features used to place all• State the main features used to place all organisms into one of the five kingdoms: animal, plant, fungus, prokaryote, protoctist1.3.5Main features used to place organisms• State the main features used to place organisms into groups within the plant kingdom, limited to ferns and flowering plants (dicotyledons and monocotyledons)1.3.6Classify organisms using the features• Classify organisms using the features identified in 1.3.4 and 1.3.51.3.7Features of viruses• State the features of viruses, limited to a protein coat and genetic material
Distinguish the animal and plant kingdoms
Animals and plants are placed in different kingdoms by a combination of cellular and nutritional features, not by one familiar example.
| Feature | Animals | Plants |
|---|---|---|
| organisation | multicellular | multicellular |
| cell wall | absent | cellulose cell wall present |
| chloroplasts | absent | present in photosynthetic tissues |
| nutrition | consume organic material | photosynthesise using chlorophyll |
| movement | usually able to move the whole organism or body parts | usually fixed in one place; parts can move or grow |
A multicellular organism with cellulose cell walls and chloroplasts belongs to the plant kingdom. A multicellular organism whose cells lack walls and chloroplasts and which feeds on other organisms belongs to the animal kingdom.
Movement alone is not a safe kingdom test, and not every plant cell contains chloroplasts. Use the combined pattern of cell walls, chloroplasts, nutrition and organisation.
Recognise vertebrate and arthropod groups
Vertebrates have a backbone. Arthropods have a segmented body, jointed appendages and an exoskeleton. Features within each group separate the named classes.
| Vertebrate group | Main identifying features |
|---|---|
| mammals | hair or fur; females have mammary glands and feed young with milk; lungs |
| birds | feathers; beak; hard-shelled eggs |
| reptiles | dry, scaly skin; leathery-shelled eggs laid on land |
| amphibians | moist skin without scales; eggs laid in water; larvae and adults differ |
| fish | scales and fins; gills; aquatic |
| Arthropod group | Main identifying features |
|---|---|
| myriapods | many body segments; many pairs of legs |
| insects | head, thorax and abdomen; three pairs of legs; one pair of antennae |
| arachnids | cephalothorax and abdomen; four pairs of legs; no antennae |
| crustaceans | usually more than four pairs of legs; two pairs of antennae |
Wings do not define birds because some insects and mammals also have wings. Four limbs do not distinguish one vertebrate class. Prefer feathers, fur, skin, gas-exchange structures, leg pairs and body regions.
Classify animals from a feature set
To classify an animal, match all available evidence to the defining feature set for a kingdom and then for a vertebrate or arthropod group.
| Step | Question |
|---|---|
| 1 | Is it an animal: multicellular, no cellulose cell walls, feeds on organic material? |
| 2 | Does it have a backbone, or the exoskeleton and jointed appendages of an arthropod? |
| 3 | Which named group matches its covering, appendages, body regions, reproduction and gas exchange? |
| 4 | Check that no observed feature contradicts the classification. |
An animal with an exoskeleton, three body regions and three pairs of jointed legs is an insect. An animal with a backbone, moist unscaled skin and eggs laid in water is an amphibian.
When evidence is mixed, discuss both support and contradiction. A single shared feature, such as the same number of teeth or the ability to swim, is weaker than a whole matching feature set.
Do not classify from habitat or one striking feature. Whales swim but are mammals; some reptiles have four limbs, but so do many amphibians and mammals.
Distinguish the five kingdoms
The five kingdoms are animal, plant, fungus, prokaryote and protoctist. They are distinguished by cell type, organisation, cell walls, chloroplasts and nutrition.
| Kingdom | Main features |
|---|---|
| animal | multicellular; no cell walls or chloroplasts; feeds by consuming organic material |
| plant | multicellular; cellulose cell walls; chloroplasts; photosynthetic |
| fungus | usually a mycelium of hyphae; chitin cell walls; no chloroplasts; extracellular digestion then absorption |
| prokaryote | usually unicellular; no nucleus or membrane-bound organelles; circular DNA; cell wall not made of cellulose |
| protoctist | mostly unicellular eukaryotes with a nucleus; varied features; some have chloroplasts and photosynthesise |
First ask whether a nucleus is present. No nucleus indicates a prokaryote. With a nucleus, use multicellularity, cell-wall material, chloroplasts and feeding method to separate plants, animals, fungi and protoctists.
A unicellular organism with a nucleus and chloroplasts is a photosynthetic protoctist, not a prokaryote. A multicellular organism with non-cellulose walls that secretes digestive enzymes and absorbs products is a fungus.
Chloroplasts do not automatically mean plant: some protoctists contain them. A cell wall does not automatically mean plant: fungi and prokaryotes also have walls of different composition.
Recognise fern, monocot and dicot features
Within the plant kingdom, ferns are separated from flowering plants; flowering plants are then divided into monocotyledons and dicotyledons.
| Group | Main features |
|---|---|
| ferns | fronds; reproduce by spores; no flowers or seeds |
| flowering plants | produce flowers, seeds and usually fruits |
| monocotyledons | one cotyledon; narrow leaves with parallel veins; fibrous roots; flower parts in multiples of three |
| dicotyledons | two cotyledons; broad leaves with branching veins; tap root; flower parts in multiples of four or five |
For a visible specimen, leaf width and venation are often the fastest evidence: narrow parallel-veined leaves support monocot; broad branching-veined leaves support dicot. Fronds and spores support fern.
One leaf feature can be damaged or atypical. Use more than one feature when available, and do not call every non-flowering specimen a fern without evidence of fronds or spores.
Classify organisms into kingdoms and plant groups
Classify an unknown organism by moving from broad cellular evidence to narrower plant-group features. Each conclusion should name the observed evidence that supports it.
| Stage | Evidence to use |
|---|---|
| kingdom | nucleus, multicellularity, cell wall and its material, chloroplasts, nutrition |
| plant versus other eukaryote | cellulose wall, chloroplasts and photosynthesis |
| fern versus flowering plant | spores and fronds versus flowers and seeds |
| monocot versus dicot | cotyledons, leaf venation, roots and flower-part number |
A plant with narrow leaves and parallel veins is classified as a flowering plant and, more specifically, a monocotyledon. A plant with fronds and spores but no flowers is a fern.
An answer should pair identity with evidence: ‘monocotyledon because its leaves are narrow and have parallel veins’, not just the group name.
Do not jump from one cellular feature directly to a plant subgroup. First establish the kingdom, then use only the syllabus-listed fern and flowering-plant features.
Identify the two defining virus components
A virus consists of genetic material surrounded by a protein coat.
| Component | Role in the structure |
|---|---|
| genetic material | carries the viral genetic information; it may be DNA or RNA |
| protein coat | surrounds and protects the genetic material |
In a simple virus diagram, an outer shell is the protein coat and the strand or material inside is the genetic material. Both are present in all viruses within the syllabus scope.
A virus is not classified as a prokaryote. A bacterial cell has cytoplasm, a cell membrane and other cellular structures; the syllabus virus model is limited to genetic material and a protein coat.
Do not label the protein coat as a cell wall or the genetic material as a nucleus. The objective requires exactly the protein coat and genetic material; extra organism-specific structures are not universal virus features.