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35 Cards in this Set

  • Front
  • Back

What are the biotic factors that control the size of a population?

•Competition


•Predation


•Parasitism


•Symbiosis

Define competition

The struggle between organisms of the same or different species for one or more limited resources.

What do plants compete for?

Light, water, minerals, space.

What do animals compete for?

Food, water, territory, mates.

What is intraspecific competition?

Competition between members of the same species. Eg. two rams fighting for a mate.

What is interspecific competition?

Competition between members of two different species. Eg. blackbird and a thrush competing for an earthworm.

What is contest competition?

A type of competition where one of the organisms wins the resource and the other loses. It involves a physical contest between the two organisms.

What is scramble competition?

All of the competing organisms get some of the resource. Often none get sufficient resources to survive. Eg. large number of seeds germinating in a seed box - all grow starggly as they compete for water, light, minerals, space.

Give three advantages of competition/predation.

1. Reduces size of population and maintains it at a sustainable level.


2. Helps maintain bio diversity as one species does not thrive at the expense of another.


3. Important role in evolution ie. members of a species compete - the fitter ones (better adapted ones) survive, reproduce and pass on their better genes. This produces a better adapted population.

Define adaptation

A modification of structure or behaviour that improves an organism's chances of survival and reproduction.

What do organisms do to avoid competition?

They adapt.

Give four examples of structural modification.

Thorns(rose)


Sting(nettle/bee)


Spikes(hedgehog)


Shell(snail)

Give two examples of behavioural modification.



Hibernation(bears) - to withstand cold, less energy required, during time of poor food availability.



Nocturnal activity (owl) - less organisms competing for food.

Define predation

The hunting capturing and killing of prey.

Adaptations of hawk(predator).

•Great speed


•Pointed beak


•Powerful wings


•Very well developed eyesight

Adaptations of ladybird(predator)

Strong mouth parts for chewing prey.

Adaptations of mouse (prey)

•Small for concealment from prey.


•Grey/brown in colour for camouflage.


•Great speed to avoid predator.

Adaptations of greenfly

Green for camouflage.

Give three factors that affect predator prey relationships

1. Food availability


2. Concealment


3. Movement of predators

Define parasite

An organism that feeds on an organism of a different species causing it harm.

What are endoparasites?

Parasites that live inside their host Eg. tapeworm living in the intestines.

What are ectoparasites?

Parasites that live on the outside of a host Eg. a flea on a dog.

Three differences between parasite and predator.

1. Parasites tend to be smaller than the host (flea on dog). Predators tend to be bigger (hawk and mouse).



2. Parasites often attack from within the host ( tapeworm). Predators attack from outside.



3. Parasites tend to do limited damage (so they don't eliminate food source). Predator kills and eats their prey.

Give two functions of parasites.

Rate of reproductions may be reduced maintaining the population of a species at a sustainable level.



•Role in evolution - stronger, fitter members of the species survive and reproduce and pass on the better genes.

Define symbiosis

This is a relationship between two different species living together to the benefit of at least one of the species.

What are the three categories of symbiosis?

1. Parasitism


2. Mutualism


3. Commensalism

What is parasitism?

Type of symbiosis where the parasite gains and the host is badly affected. Eg. liver fluke living in the bile duct of a sheep.

What is mutualism?

Type of symbiosis where both species gain. Eg. symbiotic bacteria living in the intestines.

What is commensalism?

Type of symbiosis where one species gains and the other is unaffected. Eg. Lichen growing on a tree.

Define exotic species

An introduced, alien, nonnative species. A species living outside it's native distributional range, which has arrived there by human activity, either deliberate or accidental.

Two possible disadvantages of exotic species.

1. Competition with native species : grey squirrel competes with native red squirrel for resources.



2. Potential predators of native species : the mongoose was introduced to Hawaii to control rats which had previously been accidentally introduced. Unfortunately, the mongoose also eats many native Hawaiian animals.

Three possible benefits of exotic species

1. Food source.



2. Biological control : for the control of a nuisance species Eg. a small wasp was introduced from China to help control the European corn borer, one of the most destructive insects in north America, making it a recent example of a long history of classical biological control efforts for this major pest.



3. Aesthetic eg. pandas.

Four reasons for failure of attempted introductions of exotic species.

•Failure to adapt


•Preyed upon by native predators


•Insufficient numbers for successful breeding.


•Competition with native species

How may an exotic be spread?

•Escaping from captivity eg. animals kept as pets ( racoons, minks ).


•Dispersal of seeds.


•Through fruits - border control will not allow fruits/veg through.

When does an exotic species have a good chance of becoming established in a new environment?

If there is a vacant niche.



•May occur if the exotic species is adapted to the new environment.


•May not occur if the new species is not adapted to the environment.