OCR Biology Unit 2: Section 6 - Biodiversity

Biodiversity - is the number and variety of species, habitats and ecosystems found in a specific geographic location.

Species - a group of very similar organisms that are able to breed and produce fertile offspring.

Habitat - an area inhabited by a species that are most suitable for the area, in terms of physical factors; temperatures etc. and biotic factors; food supply etc.

Population – a group of organisms of the same species, living in the same place and at the same time and also able to interbreed.

Community – all the living organisms, of all species living in the same place.

Ecosystem – considered as a relatively self-contained system including all the living organisms and their environment interacting with each other.

High biodiversity in areas means there is lots of different species.

Habitat Diversity – the number of different habitats present in an area.

Species Diversity – the number of different species and the abundance of each in an area.

Genetic Diversity – this is the variation of alleles within a species.

Sampling – it’s too time consuming to count every organism, so samples are taken.

Random sampling – this is choosing small areas to randomly sample. E.g. using coordinates.

Systematic sampling – placing quadrats, for example, systematically along a line (transect).

Sweep netting – used for catching mobile animals like spiders, invertebrates and insects. It involves using a big net and sweeping the area with it.

Longworth trap – also used for mobile animals, including – voles, mice and other small mammals. The traps are checked once a day and the animals are marked and released.

Mark, release, recapture – this is a good method of estimating the population of a mobile organisms. A group of animals are caught and these are marked and counted, they are then released into the population so that they can mix randomly. Another group is then caught and the marked animals are counted.

To estimate the size of the population from the mark, release, reacpture technique,  take the numbers caught in the first and second sample and multiply them together, then divide by the number of marked in the second sample.

Eg. 17 caught in first sample, 18 caught in second sample and 6 were marked;

 (17 x 18) / 6 = 51

Estimate of population is 51.

Species Richness – is the number of different species in an area. The higher the number of species, the greater the species richness.

Species Evenness – measure of relative abundance of each species. The more even the population size of each species, the greater the species evenness.

Diversity measured using Simpson’s Index of Diversity

n= total number of individuals of one species

N = total number of organisms of all species.

It is always a value between 0 and 1, the closer it is to 1 the higher the diversity in the area.

D = 1 - 'sum of' (n/N)^2

Global biodiversity is the total number of species on earth.

Named species – 1.5-1.75 million – no central database of species names and some scientists disagree.

Unnamed species – a very large proportion – undiscovered or not yet named.

Estimates of total numbers of species are between 5 million to 100 million. Most recent estimates are around 14 million.

Biodiversity varies across the Earth, but there is more variety around the equator and this reduces as you move towards the poles.

Climate change

Affects biodiversity – most species need a particular climate to survive.

-          Drastic changes in climate mean that some habitats become inhabitable and vice versa.

-          Some species may have to migrate causing changes in species distribution.

-          Extinctions may occur if the species have nowhere new to go and if the species is a plant it can’t migrate.  

Climate change

Affects spread of disease

-          Numbers of the insects that carry disease may become greater with climate change. E.g. areas get warmer and wetter and insects like mosquitoes will move into these areas and infect more people.

-          Warmer and wetter conditions may also lead to more fungal infections.

Climate change

Affects agricultural patterns

-          Changes in temperature, rainfall, floods/drought, timing of the seasons.

-          Land becomes available for agriculture; this improves the biodiversity in the area.

-          Different crops require different conditions to grow so as the climate changes, the crops may or may not grow.

Maintaining Biodiversity

Economic reasons

-          Food and drink – plants and animals are sources of many foods and some drinks.

-          Clothing – lots of fibres and fabrics are made from plants and animals.

-          Drugs – many made from parts of plants.

-          Fuels – organisms produce renewable fuels.

-          Other industrial materials – wood, paper, dyes, adhesives, oils, rubbers, pesticides, etc.

Ecological reasons - Disruption of food chains - Disruption of nutrient cycles - Loss of habitats - Habitat destruction 

Ethical reasons -          Organisms have a right to exist -          Moral responsibility to care for the earth -          Religious and spiritual beliefs. Aesthetic reasons  -          Areas rich in biodiversity are attractive places.  -          More visitors will be attracted to the area.  

Agriculture

-          Pollinators – bees and butterflies

-          Sources of food

-          Pest control – natural predators

-          Protection against disasters – majority of food comes from only a few species of plants

-          New varieties – plants being crossbred

In situ conservation – means on site, protecting species in natural habitat.

-          National parks.

-          Controlling introduction of threatening species.

-          Protecting habitats.

-          Restoring damaged area.

-          Promoting particular species.

-          Legal protection to endangered species.

In situ conservation – means on site, protecting species in natural habitat.

-          National parks.

-          Controlling introduction of threatening species.

-          Protecting habitats.

-          Restoring damaged area.

-          Promoting particular species.

-          Legal protection to endangered species.