Adaptations for herbivory and predationSpec B4.2.9, B4.2.10
In short
Herbivores have adaptations for feeding on plants, such as the chewing or piercing mouthparts of leaf-eating insects, and plants resist herbivory with thorns and toxic secondary compounds, which some animals can detoxify. Predators have chemical, physical and behavioural adaptations for finding, catching and killing prey, and prey animals have matching adaptations for resisting predation.
Herbivores and plants
- Chewing mouthparts: leaf-eating insects such as caterpillars and locusts have hard mandibles that bite off and grind leaf tissue.
- Piercing mouthparts: insects such as aphids have a needle-like stylet that pierces leaf tissue to reach and suck phloem sap.
- Physical defences of plants: thorns, spines and other physical structures such as stinging or tough hairs deter herbivores.
- Chemical defences of plants: plants produce toxic secondary compounds in seeds and leaves, such as alkaloids (nicotine in tobacco leaves) and cyanogenic glycosides.
- Metabolic adaptations of herbivores: some animals can detoxify these toxins. Koalas break down the toxic compounds in eucalyptus leaves using liver enzymes, so they can feed on a food few others can eat.
Predators and prey
| Type | Predators: finding, catching and killing | Prey: resisting predation |
|---|---|---|
| Chemical | Venom to kill or paralyse prey (e.g. rattlesnakes); detecting the scent of prey | Toxins and distasteful chemicals (e.g. poison frogs); defensive sprays (e.g. skunks) |
| Physical | Sharp teeth and claws; speed (e.g. cheetah); forward-facing eyes for judging distance; camouflage for ambush | Camouflage; spines or shells (e.g. porcupines, tortoises); speed; warning colours |
| Behavioural | Hunting in packs (e.g. wolves); ambush; stalking | Living in herds or shoals; alarm calls; fleeing; playing dead |
Exam tip:
If a question asks for chemical, physical and behavioural adaptations, give one clear example of each and say how it helps the predator or prey survive.
Written and checked against the IB Biology HL specification · Updated October 2026