3.3 Biodiversity Flashcards
Define biodiversity
Biodiversity is the total variation that exists among all living things on earth.
Define genetic diversity
Genetic diversity is the number and frequency of all the alleles within a population.
If one population of a species dies out then the species may have lost some of its genetic diversity, and this limits its ability to adapt to changing conditions.
species diversity can be divided into two sub visions
species richness - number of different species in an ecosystem.
Relative abundance - the proportion of each species in an ecosystem.
Effect of a dominant species in an community
a community with an dominant species has a lower species diversity than one with the same species richness which does not have a particular dominant species.
Define ecosystem diversity
refers to the number of distinct ecosystems within a define area. The more ecosystems the better the biodiversity.
HIPPO factors - examples of species affected
Habitat Destruction - scottish wildcat by deforestation.
Invasive species - red squirrel out competed by non native grey squirrel.
Population(human) Increase - bengal tigers forced out of territories by human housing developments.
Pollution - Slender stonewort plant affected by nitrate and phosphate pollution caused by fertiliser runoff and sewage into rivers/lochs.
Overexploitation - Cod stocks in the north sea plummeted to critical levels.
overexploitation and recovery
with overexploitation, 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.
Bottleneck Effect
The bottleneck effect is when small populations may lose the genetic variation necessary to enable evolutionary responses (to adapt) to environmental change.
This loss of genetic diversity in small populations can be critical for many species (not all), as interbreeding can result in poor reproductive rates.
effect of habitat fragmentation on biodiversity
Degradation causes a decrease in habitat quality at the edges of habitat fragments and results in increased competition between species
effect of habitat fragmentation on biodiversity
Degradation causes a decrease in habitat quality at the edges of habitat fragments and results in increased competition between species, as the fragment becomes smaller, which may reduce biodiversity.
More isolated/smaller fragments exhibit a lower species diversity.
Fragmentation occurs as habitats are isolated/spilt by human activities; deforestation, roadbuilding.
Habitat corridors and benefits
Habitat corridors allow movements of animals between fragments.
Benefits :
- increased access to food; increased choice of mates; may lead to re-colonisation of small fragments after local extinction.
Introduced (non native) species
introduced (non native) species are those that humans have moved either intentionally or accidently to new geographical locations.
Either positive/negative effect on native species.
Naturalised species
naturalised species are introduced (non native) species which become established within wild communities.
Little or no effect on indigenous population.
Invasive species
invasive species are naturalised species that spread rapidly and eliminate native species.
Reduces species diversity.
why are invasive species more successful in their new habitat?
invasive species are usually free of predators, parasites, pathogens and competitors that limit their population in their native land.
