12. Biodiversity

• Biodiversity: is the variety of life on Earth

• Habitat: the home or environment of an animal, plant or organism

• Species: a group of organisms with similar adaptations that live and breed together to produce fertile offspring with genetic variation 

Sampling involves studying small parts of the habitat in detail and then multiplying up to calculate the size of a population. It is assumed that the sample plots are representative of the entire habitat.

When sampling, it is important to consider that:

• size of the sample- this depends on the size of the habitat
• number of sample areas used- the more sample areas used the more reliable the results
• sampling technique used- this must be identical in every sample

Sampling Techniques:

• random sampling- avoids bias by generating random numbers, which are used as coordinates to locate sample areas on an imaginary grid place over the habitat
• non-random sampling- this includes:
  • opportunistic sampling- using prior knowledge to select sample sites or changing the sampling strategy once outside
  • stratified sampling- involves carrying out samples in each recognised sub-habitat
  • systematic sampling- involves carrying out sampling at fixed intervals in each direction

Sampling Methods:

The method of sampling used depends on the type of vegetation in the habitat and what type of organisms are being examined. It is important to measure both the number of species (species richness) and the number of individuals in each species (species evenness) 

Plants- Larger plants can be counted individually, smaller plants can be sampled using quadrats. These are plants placed on random sites and the species present are listed. To turn this into quantitative sample you can calculate the percentage cover of each species in the quadrat. This can be done using the following:

• point sampling: place a point frame in the quadrat and count the number of examples of each species that touch that point
  
• grid sampling: divide the quadrat using string into a known number of smaller squares (often 100) and then estimated how many squares are occupied by each species

Animals- Large animals can be sampled by careful observation and counting, smaller animals will need to be caught or trapped. It is possible to estimate the population size by the mark and recapture technique. This involves two different trapping sections. The animal is caught the first time, marked and then let back into the habitat. This first session is T1. Then another trapping session is done where they track animals caught with the markings T3 and animals without the markings T2. The total population is given by:

Number in population = T1 X (T2/T3)

Types of traps include; pitfall traps, sweep netting, pond netting, Longworth traps.

Species Richness:

The number of different species in a habitat

Species Evenness:

How evenly each species is represented throughout a habitat

A diverse habitat would contain a large number of species, all of them represented by a sizeable population rather than by just one or two individuals. 

Simpson's Index of Diversity measures the biodiversity of a habitat. The formula for this is:

D = 1 - (sum of (n/N)squared)  where n= the total number of individuals in a particular species, N= the total number of individuals in all species. 

The resultant value always ranges between 0 and 1

Interpretations of High and Low Values:

A high value (close to 1) indicates:                                                      A low value (close to 0) indicates:

  -a habitat with high diversity                                                                -a habitat with low diversity

  -a high species richness                                                                        -a habitat dominated by one or a few species 

  -a high species evenness                                                                       -an unstable and damaged habitat

  -should be a stable habitat and should survive disruption                    -the habitat may be manmade

  -the habitat should be one worth conserving

Assessing Genetic Diversity:

The genetic diversity of a population may be important to conservationists wishing to maintain the health of a captive population in a zoo or rare-breed centre. Genetic diversity is increased when there is more than one gene variant (allele) for a particular locus. If there are several alleles, it is called a polymorphic gene locus. A measure of genetic diversity is given by the formula:

the proportion of polymorphic gene loci = number of polymorphic gene loci / total number of loci

Factors Affecting Biodiversity:

• the rapid human population growth, which means that more space and resources are taken up to supply living space and food
• the increasing use of agriculture (monoculture) as an efficient way to produce food and other products, this decreases biodiversity and reduces the size of natural habitats, which may become unstable as a result
• the increasing release of waste products that pollute the atmosphere, causing climate change 

Ecological Reasons:

• fixing of energy from sunlight
• regulation of the oxygen and carbon dioxide levels in the atmosphere
• fresh water purification and retention
• soil formation
• maintenance of soil fertility
• mineral recycling
• waster detoxification and recycling

Economic Reasons:

• the growth of food and timber relies on the correct functioning of ecosystems, the unstable ecosystem could cause soil depletion (loss of fertility)
• pollination of many crops relies on insects, particularly bees
• natural predators to pests reduce the need for pesticides
• at yet unknown species may contain molecules that are effective medicines
  

Aesthetic Reasons:

• everyone enjoys nature or it benefits them someway
• being surrounded by natural systems relieves stress and helps recovery from injury

This involves conserving a species in its natural habitat by creating marine conservation zones and wildlife reserves. 

Advantages:                                                                         Disadvantages:

- the organisms are in their normal environment                 - it can be difficult to monitor the organisms

- the habitat is conserved along with the species                 - environment factors can cause a decline

- the organisms will behave normally                                  - poaching or hunting may continue

- generates work for local people                                         - may be food shortages

- ecological tourism can generate income                            - disease will be difficult to treat

                                                                                              - predators can be difficult to control

This involves conserving a species using controlled habitats away from its normal environment. Seed banks, botanic gardens and zoos all keep groups of individuals of endangered species

Advantages:                                                                 Disadvantages:

- research is easy                                                         - the organisms are living in an unnatural habitat

- health can be monitored                                            - the organisms may not behave as normal

- controlled breeding reduces inbreeding                    - the organisms may not breed

- sharing resources increases genetic diversity           - natural habitat is not conserved

- reintroduction to the wild

- uses less space

The Convention on International Trade in Endangered Species (CITES)

An international agreement between governments, to which countries adhere voluntarily. Its aim is to ensure that international trade in specimens of wild animals and plants does not threaten their survival.

The Rio Convention on Biological Diversity (CBD)

This recognises that people need to secure resources of food, water and medicines. However, it promotes development that is sustainable and partner countries agree to adopt ex situ conservation measures with shared resources.

The Countryside Stewardship Scheme (CSS)

This aims to enhance the natural beauty and diversity of the UK's countryside and improve public access. This includes looking after wildlife habitats, retaining the traditional character of the land and protecting historical features and natural resources. 

It applies to land that is not considered to be an environmentally sensitive area. Payments are made to landowners to manage the land in a suitable manner and for capital works such as hedge laying, planting and repairing dry-stone walls.