Competition & Adaptation


Organisms compete with each other for certain essential needs for survival. Survival of the Fittest!

Plants compete for:

  • light for photosynthesis
  • water
  • nutrients & minerals

This video looks at competition of plants

Animals compete for:

  •  food
  • water
  • mates to reproduce
  • living space

Predator / Prey relationship

A predator is an organism that eats another organism. The prey is the organism which the predator eats. Some examples of predator and prey are lion and zebra, bear and fish, and fox and rabbit. The words "predator" and "prey" are almost always used to mean only animals that eat animals, but the same concept also applies to plants: Bear and berry, rabbit and lettuce, grasshopper and leaf.

Predator and prey evolve together. The prey is part of the predator's environment, and the predator dies if it does not get food, so it evolves whatever is necessary in order to eat the prey: speed, stealth, camouflage (to hide while approaching the prey), a good sense of smell, sight, or hearing (to find the prey), immunity to the prey's poison, poison (to kill the prey) the right kind of mouth parts or digestive system, etc. Likewise, the predator is part of the prey's environment, and the prey dies if it is eaten by the predator, so it evolves whatever is necessary to avoid being eaten: speed, camouflage (to hide from the predator), a good sense of smell, sight, or hearing (to detect the predator), thorns, poison (to spray when approached or bitten), etc.


The fastest lions are able to catch food and eat, so they survive and reproduce, and gradually, faster lions make up more and more of the population. The fastest zebras are able to escape the lions, so they survive and reproduce, and gradually, faster zebras make up more and more of the population. An important thing to realize is that as both organisms become faster to adapt to their environments, their relationship remains the same: because they are both getting faster, neither gets faster in relation to the other. This is true in all predator-prey relationships.

Mutualism and Parasitism

Some organisms rely on the presence of organisms of a different species. This may be beneficial to both species, but it does not have to be.

In mutualism, both species benefit from their relationship. For example, oxpecker birds eat ticks and larvae infesting the skin of buffalo and other large animals. For this reason oxpeckers are called a cleaner species.

Lichens are another example of mutualism. They are formed by algae and fungi living together. Algae can photosynthesise and make food, which is shared by the fungus. The fungus in turn shelters the algae from a harsh climate.

Parasites are organisms that live on or in a host organism. The parasite benefits from this arrangement, but the host suffers as a result. Fleas are parasites. They live on the skin of other animals and suck their blood. This feeds the flea but weakens the host.

A tapeworm lives inside another animal, attaching itself to the host’s gut and absorbing its food. The host loses nutrition, and may develop weight loss, diarrhoea and vomiting. Parasites do not usually kill the host, as this would cut off their food supply.


Every organism has certain features or characteristics that allow it to live successfully in its habitat. These features are called adaptations, and we say that the organism is adapted to its habitat. Organisms living in different habitats need different adaptations.

Adaptation Example: Camel & Polar Bear

Living things adapt over time to their environment in order to survive

Camel well suited for desert:

  • slit-like nostrils, two rows of eyelashes to keep sand out
  • wide, flat feet to stop them sinking into sand
  • thick fur to keep sun off their skin

 Polar Bear well suited for Arctic:

  • black skin absorbs heat well
  • white fur camouflages against snow and ice
  • thick layers of fat and fur for insulation
  • wide, hairy soles avoid bear from slipping

This video shows plant adaptations

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