Herbivory

Herbivores are a type of heterotrophic consumer that feed principally on plant matter (i.e. vegetation)

• Plants have evolved defences to resist herbivory, while herbivores have developed adaptations to overcome these defences
  

Plant Defences:

• Physical structures – spines and thorns act as deterrents, while thick bark and waxy cuticles can restrict ingestion

• Chemical compounds – seeds and leaves may contain toxic compounds or bitter-tasting chemicals to reduce feeding

Herbivore Adaptations:

• Specialised mouthparts – insects may have stylets or mandibles to assist in piercing or cutting through plant matter

• Digestive systems – ruminant animals have multiple compartments in their stomach to allow for the regurgitation and breakdown of food

• Microbiotic bacteria – the gut flora in ruminants aid in the breakdown of plant sugars (such as cellulose)

• Metabolic processes – certain animals produce chemicals capable of neutralising the toxic compounds produced by specific plants

Carnivory

Carnivores are a type of heterotrophic consumer that feed primarily on animal matter (i.e. meat eaters)

• Predators have developed adaptations for catching prey, while the prey will possess characteristics to resist predation
  

Prey Adaptations:

• Physical structures – tough exoskeletons and shells provide a level of protection against predators

• Appearances – prey may be camouflaged, mimic predator structures or possess bright warning colours

• Chemical compounds – toxins and scents may deter predators or cause harm to the predator when consumed

• Behaviours – prey may act in certain ways to avoid predation (e.g. feigning death, puffing up, grouping together)

Predator Adaptations:

• Physical structures – sensory organs to better detect prey and physical features such as sharp teeth and claws

• Appearances – predators may be camouflaged or have a streamlined body shape to increase speed

• Chemical compounds – neurotoxins and venoms can be used to paralyse or subdue their prey

• Behaviours – predators may act in certain ways to successfuly capture prey (e.g. lay in ambush, hunt in packs)

Omnivory

Omnivores are a type of heterotrophic consumer that feed on both plant and animal matter 

• Diets based on plant or animal matter can be inferred by the dentition (teeth shape) of organisms
  

Hominidae Diets

• Hominidae are a family of greater apes that include gorillas and chimpanzees, as well as modern and ancestral humans

• Hominids that feed predominantly on plant matter have broader jaw muscles, larger premolars and thicker tooth enamel for grinding tough vegetation

• Hominids that eat more meat have narrower jaws and smaller teeth for chewing softer animal tissue, while incisor teeth and canines are tightly packed to enable cutting and tearing

• Teeth can also play a role in other processes (such as aggressive posturing), which is why gorillas have large canines despite being mainly herbivorous

A comparison of the jaws and dentition of extinct hominin (human) fossils demonstrates an evolutionary shift towards a higher proportion of meat in the diet

• Jaws have become narrower, with smaller teeth, as humans developed tools and hunting practices to support greater meat-eating behaviours

• For example, Paranthropus robustus has a larger jaw (suggesting herbivory) than Homo floresiensis (suggesting omnivory) 

Hominid Dentition