A Level Biology B Edexcel

Defining and Understanding Biodiversity

Understanding Biodiversity

• Biodiversity refers to the variety of life at different levels of biological organization. This encapsulates genetic diversity, species diversity, and ecosystem diversity.

Genetic Diversity

• Genetic diversity is the variety of genes possessed by the individuals making up a population, species, or community.
• More genetic diversity ensures long-term viability of a species because it provides more opportunities for adaptation to changing environments.
• Inbreeding reduces genetic diversity; conversely, a wide gene pool promotes it.

Species Diversity

• Species diversity includes two components: species richness (the number of different species in an area) and species evenness (does one species dominate the area or are species numbers fairly equal).
• A higher degree of species diversity generally contributes to the stability of an ecosystem, as a variety of species can compensate for changes in the environment.

Ecosystem Diversity

• Ecosystem diversity refers to the variety of different ecosystems on the Earth.
• Each ecosystem contains unique combinations of species, interactions between these species, and physical conditions under which these species live.

Defining and Identifying Species

• The biological species concept binds species as groups of organisms that can breed together to produce fertile offspring.
• This definition has limitations, particularly for organisms that reproduce asexually, don’t currently have the opportunity to interbreed, or for extinct groups of organisms.
• The phylogenetic species concept identifies species based on the evolutionary history of the population.
• The morphological species concept categorizes species based on observable physical features.

The Importance of Biodiversity

• Biodiversity contributes to everything from ecosystem services such as decomposition, water purification, and pollination, to cultural, spiritual, recreational, and aesthetic values.
• Biodiversity is important to human survival as it provides food, fibres, and medicinal resources; it also ensures the availability of a healthy gene pool for future use.

Threats to Biodiversity

• Threats to biodiversity include habitat loss, overexploitation, invasive species, pollution, and climate change.
• Conserving biodiversity requires understanding threats and their impacts as well as taking action to mitigate or limit those threats.
• Conservation strategies may include establishing protected areas, restoring degraded habitats, reintroducing species, and implementing laws and regulations.