8. threats to biodiversity Flashcards
describe exploiting
refers to humans making use of different species to gain useful products (eg. raw materials and food)
describe overexploiting
applies to a situation where individuals are being removed at a greater rate than can be replaced by reproduction
describe the bottleneck effect
some small populations may lose the genetic variation necessary to enable evolutionary responses to environmental change e.g. catastrophic over-exploitation.
In small populations, this loss of genetic diversity can be critical for many species, as inbreeding can result in poor reproductive rates
describe how allele frequencies are affected by the bottleneck effect
A population that has been affected by a catastrophic event (eg. earthquake) will have individuals that survive and those that are killed - regardless of the alleles they have.
This results in decreasing allele frequency as some alleles disappear from the population (they have been killed). The smaller surviving population will therefore have different allele frequencies than before
Explain why small populations with reduced genetic diversity may not recover
Smaller populations with very low genetic diversity have similar consequences to inbred populations. This can result in lower reproduction rates. If the death rate is higher than the birth rate then the population will die out
describe what happens when there is 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 and smaller fragments exhibit a lower species diversity
Considering some species are better adapted to the interior of the habitat and others to the edge, why might species diversity decrease in the interior habitat.
Decreased area of interior. Interior species are not adapted to live at the ‘edge’ therefore individuals of that species will die. Decreased species richness leads to decreased species diversity
why are habitat corridors beneficial
The corridors allow movement of animals between fragments, increasing access to food and choice of mate. This may lead to recolonisation of small fragments after local extinctions
what do habitat corridors allow
-Allow animals to move and occupy new areas when food sources become scarce in their core habitat
-Allow species to relocate seasonally without the need for human interference
-Allow animals to find new mates in neighbouring regions so that genetic diversity can increase within the population.
describe introduced species
species that humans have moved either intentionally or accidentally to new geographic locations
describe naturalised species
introduced species that become established within wild communities
describe invasive species
naturalised species that spread rapidly and eliminate native species, therefore reducing species diversity.
They may well be free of the predators, parasites, pathogens and competitors that limit their population in their native habitat.
They may prey on native species, outcompete them for resources or hybridise with them
