Biodiversity

Biodiversity: variety of life existing on multiple levels

Ecosystem diversity: range of different habitats or number of ecological niches per unit area in an ecosystem

variety in the combinations of species living together in communities

--> due to the varied environments on Earth

Genetic diversity: variety in the gene pool of each species

--> variations between geographically separated populations

Species diversity: variety of species per unit area

--> includes both the number of species present and their relative abundance

--> can be determined by estimating the richness and evenness of the species in the area

Richness: refers to the number of species in an area

Evenness: relative abundance of each species

Simpson's Reciprocal Index can be used to describe and compare communities and their diversity

D = N(N-1) / Σ n(n-1)

N = total number of individuals of all species

N = number of individuals of each species

Species numbers and abundances can be sampled by random quadrat

Low diversity could indicate pollution, eutrophication, recent colonisation of a site or agricultural management

Biodiversity can be deduced from fossil evidence

Five mass extinctions (last one was 66 million years ago)

Biodiversity tends to rise gradually between mass extinction events

Evidence for biodiversity can be gathered directly by carrying out reliable surveys that can find changes:

In a species: numbers in population of the species, genetic diversity and range of the species
In an ecosystem: species diversity, richness and evenness of biodiversity, area occupied, extent of ecosystem degradation
For a taxonomic group: number of threated species within the group

Causes of current biodiversity crisis:

Current sixth mass extinction is happening much more rapidly as a result of human influence:

The reasons for the rise in these activities is largely due to overpopulation

--> population increased from 2 million to 8 million people from 1920