Biodiversity & Resilience (HL IB ESS OLD COURSE - IGNORE)
Revision Note
Written by: Alistair Marjot
Reviewed by: Bridgette Barrett
Understanding Biodiversity
Why is biodiversity important?
Biodiversity can be thought of as a study of all the variation that exists within and between all forms of life
Biodiversity looks at the range and variety of habitats, species and genes within a particular region
It can be assessed at three different levels:
The number and range of different ecosystems and habitats
The number of species and their relative abundance
The genetic variation within each species
Biodiversity is very important for the resilience of ecosystems
This is because biodiversity allows them to resist changes in the environment and avoid ecological tipping points
Habitat diversity
This is the range of different habitats within a particular ecosystem or biome
If there is a large number of different habitats within an area, then that area has high biodiversity
A good example of this is a coral reef
They are very complex with lots of microhabitats and niches to be exploited
If there is only one or two different habitats then an area has low biodiversity
Large sandy deserts typically have very low biodiversity
The conditions are basically the same throughout the whole area
Species diversity
An ecosystem such as a tropical rainforest that has a very high number of different species would be described as species-rich
Species richness is the number of species within an ecosystem
Species diversity looks at the number of different species in an ecosystem, and also the evenness of abundance across the different species present
The greater the number of species in an ecosystem and the more evenly distributed the number of organisms are among each species, then the greater the species diversity
Ecosystems with high species diversity are usually more stable than those with lower species diversity as they are more resilient to environmental changes
For example in the pine forests of Florida, the ecosystem is dominated by one or two tree species
If a pathogen comes along that targets one of the two dominant species of trees, then the whole population could be wiped out and the ecosystem it is a part of could collapse
Genetic diversity
Genetic diversity is the diversity of genes found within different individuals of a species
Although individuals of the same species will have the same set of genes, these genes can take a variety of different forms
This makes it possible for genetic diversity to occur between populations of the same species
Genetic diversity within a single population also occurs
This diversity is important as it can help the population adapt to, and survive, changes in the environment
This could include changes in biotic factors such as new predators, pathogens and competition with other species
Or the changes could be abiotic factors like temperature, humidity and rainfall
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