Quick questions on Levels of biodiversity (genetic, species, ecosystem): QCE Biology Unit 3

Genetic biodiversity is the variation of alleles within a species, both within a single population and between populations.

Species biodiversity is the number and relative abundance of species in a defined area.

Ecosystem biodiversity is the variety of habitats, communities and ecological processes within a region.

Allelic variation is the raw material for natural selection. A species with high genetic biodiversity contains individuals with different combinations of alleles, so when the environment changes (a new pathogen, a heatwave, a salinity shift) at least some individuals carry alleles that confer resistance and survive to reproduce.

The cheetah (Acinonyx jubatus) is the classic case of low genetic biodiversity. A population bottleneck around 10 000 years ago left cheetahs so genetically uniform that skin grafts between unrelated individuals are not rejected. The species is vulnerable to disease outbreaks for this reason.

- Species richness: the count of species present. - Species evenness: how evenly individuals are distributed across those species. A community with 100 individuals split 50/50 across two species is more even, and more biodiverse, than one with 99 individuals of species A and 1 of species B.

Coral species such as Acropora millepora show measurable variation in heat-shock protein alleles between northern and southern reefs, and individuals with these alleles bleach less readily.

The reef supports about 1500 fish species, 400 coral species, six of the world's seven marine turtle species and over 30 species of marine mammal.

Within the reef system there are coral reef, seagrass meadow, mangrove forest, lagoon and deep slope ecosystems, each with different physical conditions and species.

Richness is one component of species biodiversity; evenness is the other. Two communities with the same richness can have very different biodiversity.

Ecosystem biodiversity is the number and variety of ecosystem types in a region, not a single ecosystem.

Bacteria, archaea and fungi contribute heavily to all three levels. A handful of forest soil contains more bacterial genetic biodiversity than the entire vertebrate phylum.

Markers want each example tagged: this example shows genetic biodiversity because, this example shows species biodiversity because.