Biodiversity

• biodiversity is the variety of living organisms in an area
• a habitat is the place where an organism lives
• a community is all the populations of different species in a habitat
• levels of biodiversity: biodiversity can be considered at a range of scales from the local to the global
• local biodiversity - consider the variety of different species living in a small habitat e.g. a pond or meadow. Some habitats will be more biodiverse than others
• global biodiversity - the variety of species on earth. Recent estimates put the total number of species on earth at about 8.7 million

  biodiversity varies in different parts of the world - it is greatest at the equator and decreases towards to poles
• Biodiversity can be measures using species richness or an index of diversity
• species richness is a measure of the number of different species in a community - which makes it a simple measure of biodiversity. It can be worked out by taking random samples of a community and counting the number of different species
• However, no. of different species in a community is not the only thing that affects biodiversity. Population sizes of those species do too. Species that are in a community in very small numbers shouldn't be treated the same as those with bigger populations - this is where an index of diversity comes in
• an index of diversity is another way of measuring biodiversity. It is calculated using an equation that takes both the number of species in a community (species richness) and the abundance of each species (population size) into account
• index of diversity (d) formula = N(N-1) / sum of n(n-1_
• N = total number of organisms of all species
• n = total number of organisms of one species
• The higher the number the more diverse the area is
• if all individuals are of the same species (i.e. there is no biodiversity) the index is 1