THREATS TO BIODIVERSITY U3

Question 1

Describe how exploitation and the bottleneck affect impact biodiversity

Answer 1

With over exploitation, populations can be reduced to a low level but may still recover. Some species have a naturally low genetic diversity in their population and yet remain viable.
Example: Overfishing

The bottle neck effect – small populations may lose the genetic variation necessary to enable evolutionary responses to environmental change.

In small populations the loss of genetic diversity can be critical for many species, inbreeding can result in poor reproductive rates.

Question 2

Describe how habitat loss and habitat fragments impact on biodiversity

Answer 2

The clearing of habitats has led to habitat fragmentation.

Degradation of the edges of habitat fragments results in increased competition between species as the fragment becomes smaller.

This may result in a decrease in biodiversity.

More isolated fragments exhibit a lower species diversity.

Question 3

Describe how habitat fragments can be overcome

Answer 3

Isolated habitat fragments can be linked with habitat corridors. The corridors allow movement of animals between fragments, increasing access to food and choice of mate. This may lead to recolonization of small fragments after local extinctions.

Question 4

State the meaning of ‘introduced species’

Answer 4

An introduced species is a species that humans have moved either intentionally or accidentally to new geographical locations.

Question 5

State the meaning of the term ‘naturalised species’

Answer 5

An introduced species that has become established within the wild community are termed naturalised.

Question 6

Describe and explain the impact of an invasive species on biodiversity

Answer 6

Invasive species are naturalised species that spread rapidly and eliminate native species, therefore reducing species diversity.

Invasive species may well be:

free from predators
free from parasites
free from pathogens (disease)
free from competition that would have occurred in their own native habitat.
Invasive species may prey on native species, outcompete them for resources or hybridise with them.

Examples
Japanese Knot weed spreading throughout Great Britain.
Grey squirrel outcompeting red squirrels throughout the UK.