AS-LEVEL OCR BIOLOGY NOTES 
TOPIC 2: biodiversity

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1. biodiversity at different levels

Definitions
Species

• A group of individual organisms that are very similar in appearance, anatomy, physiology, biochemistry and genetics
  
• The members are able to interbreed freely to produce fertile offspring
  

Habitat

• Place where an organism lives
  
• Specific locality with a specific set of conditions
  
• Organisms are well adapted to their habitats
  

Biodiversity

• The variety of living species
  
• The degree of nature’s variety
  
• It allows for the permanent stability of an ecosystem
  
• Involves an equilibrium between species
  

Biodiversity can be considered at different levels.
Habitat

• Range of habitats
  
• Each may be occupied by different species
  
• Diverse habitats may lead to diverse species
  
• It is essential to conserve these
  

Species

• Difference between species
  
• This could be within a habitat, or a community
  
• Differences could be structural or physical
  
• We can collect data about different species
  
  • This will inform species richness
    

Genetic

• Genetic variation exists within a species
  
• Degree of allelic variation between the members of a species
  
• It is good
  
  • Lack of variation results in a lack of ability to adapt
    
  • Natural selection depends on variation

2. sampling and measuring the biodiversity of a habitat

In order to measure biodiversity:

• All species must be observed
  
• Number of individuals must be counted
  

Ideally this should be done for all organisms, however this may not always be practical. Instead, a habitat can be sampled.

Sampling is when a small, random portion of a habitat  is selected and studied carefully. You can then multiply up the numbers of individual species found to give  an estimate for the entire habitat.
Sampling allows us to:

• Study any impacts on the environment (EIA)
  
• EIA is used to estimate effects of a planned development on the environment
  

Number of Samples

• Depends on the size of the habitat and time
  
• Number of samples should be sufficient to give an accurate measure of the number of species in habitat and relative abundance
  
• If two areas are being compared, the same number of samples should be taken at each
  

Random Samples

• Samples must be randomly chosen
  
• This avoids bias/subjectivity
  
• You must estimate the size of the habitat and decide where to take samples
  
• This can be done by:
  
  • Taking samples at regular distances
    
  • Use random numbers to plot co-ordinates
    
  • Select co-ordinates from a map and use GPS to find the exact location
    
• However, this process may exclude infrequent plants
  
  • You should visually survey the area
    
  • Record any odd plants
    
  • Write these down, but without abundance
    
  • This is qualitative data
    
  • It cannot be used for statistical analysis
    

Sampling Plants

• A square-frame quadrat can be used to define sample area
  
• Plant species are identified, then abundance is measured
  
• This is done by:
  
  • ACFOR abundance scale
    
  • Estimate percentage cover
    
  • Key can be used to identify species within the quadrat
    

Sampling Animals

• Sampling may disturb the habitat
  
• Animals may be frightened away - this would give an unrepresentative sample
  
• Animals must be trapped or caught, then an estimate made
  
• They can be caught by:
  
  • Swamp Netting
    
  • Collecting from trees
    
  • Pitfall Trap
    
  • Tullgren Funnel
    
  • Light Trap
    

Species Richness

• This is the number of species present in a habitat
  
• The more species present, the richer the habitat
  
• Observe and record the species present in a habitat
  
• Samples should be taken
  
• Visual surveys should be taken, to ensure that nothing is missed
  
• However, this does not take into account the number of individuals of each species
  
• Not sufficient data to measure diversity alone
  

Species Evenness

• Is the number of individuals of each species
  
• Relative to population size
  
• Relative abundance of each species
  
• A habitat with even numbers of species is likely to be more diverse than one with a dominant species
  
• A quantitative survey is carried out to asses this:
  

Survey Frequency of Plants

• Count number of each species present in sample area
  
• With smaller plants is easier to calculate percentage cover
  

Density of Animals

• Careful observation can be made, counting individuals
  
• Animals can be captured, marked then released
  

• This will give an idea of the population size
  
• Counting percentage cover
  

Simpson’s Index of Biodiversity

• Diversity index is a better way of describing biodiversity
  
• It takes into account both species richness and evenness
  
• Gives an idea of the number of each species relative to population size
  
• Small and large populations are treated differently
  
• Simpson’s index measure the diversity of a habitat
  
• The formula is:
  

D =1 -  [nN]2
Where n = the number of individuals of a certain species
And N = the total number of individuals of all species


High Index of Biodiversity means…

• Indicates a diverse habitat
  
• Many different species live there
  
• Small change to environment may only affect one species
  
• If this species is only small population, then only a small proportion of the habitat is effected
  
• Total effect on the habitat would be small
  
• Tends to be stable habitat
  

Low Index of Biodiversity means...

• Suggests it is dominated by few species
  
• Small change to the environment may affect one of the major species
  
• Could damage or destroy the whole species
  
• Small change would have a very large impact on the environment
  
• Much less stable environment

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3. how genetic biodiversity is assessed

​​​Genetic diversity refers to the number of different variations of alleles at a particular locus there is in a species or population. For example, rare and endangered species have a limited genetic diversity because there are only a few of them: their gene pool is small.     

Calculating genetic diversity

• Calculate % of loci in the population with more than one allele
  
• The formula is:
  

Genetic diversity = number of polymorphic gene locitotal number of loci 100%

4. the factors affecting biodiversity

​​Many human activities contribute to loss of biodiversity

• Hunting for food
  
• Over harvesting
  
• Killing for protections
  
• Killing to remove competitors for our food
  
• Pollution
  
• Habitat destruction
  
• Inadvertent introduction of new predators to flora and fauna
  
• Population growth
  

Consequences of climate change

• Migrations
  
  • Loss of genetic variation means species will be unable to evolve
    
  • Reduction in the gene pool
    
  • Decreases genetic variation, limiting ability to evolve
    
  • Unable to adapt to changing environment
    
  • Environment is increasingly changing as a result of climate change
    
  • Only alternative for them is to move
    
  • This may result in the slow migration of entire ecosystems to the poles
    
  • Animals living in protected areas may be forced to move out, into unsafe environments just to survive
    
• Agriculture
  
  • There will be many effects on plants
    
  • These include:
    
    • Higher carbon dioxide levels
      
    • Higher temperature, increasing growth rates
      
    • Longer growing seasons
      
    • Greater evaporation and precipitation
      
    • Change in distribution of precipitation
      
    • Loss of land due to sea level rise
      
  • Domesticated plants have little variation and so are at greatest risk
    
    • Unable to evolve and adapt
      
  • Farmers may find yields decreasing
    
    • They will be forced to change their crops
      
    • Climate may change greatly
      
• Diseases
  
  • Crops grown in new areas will encounter new pests
    
  • They may not be resistant to these pests
    
  • Pest population may increase due to longer growing periods
    
  • Human diseases which thrive in moist tropics may migrate to poles as climate changes
    
  • May cause spread of diseases                             
    

Population growth

• Destroy habitats to support our own agricultural needs
  
• Alter ecosystems to provide ourselves with settlement space and food
  
  • Reduces biodiversity by reducing suitable habitat
    
• More people = more carbon dioxide emissions

5. reasons to maintain biodiversity

Moral reasons

• Last living member of a species dies
  
• Species ceases to exist
  
• 784 recorded extinction since 1500
  
• Since the spread of humans, around 100,000 years ago, the rate of extinction has risen for other species
  
• Extinction is primarily caused by human activity
  

Benefits of having large biodiversity

• Extinction reduces biodiversity
  
• Human clearing of land from agriculture removes habitats
  
• This increases chances for extinction
  
• Modern farming often plants only one type of crop (monoculture)
  
• Makes harvesting easier
  
• However, this has a very low diversity and reduces the variation of animals in this habitat
  
• Selective breeding is also used in agriculture, leading to genetic erosion
  
• Genetic erosion reduces genetic diversity
  
• Prevents organisms from adapting to survive changes in their environment
  

Economic and Ecological Reasons

• Nature can provide us with help in future developments
  
• Incredibly high value natural ecosystems
  
  • Help us with technological problem
    
  • Regulate the atmosphere
    
  • Purify fresh water
    
  • Recycle nutrients
    
  • Crop pollination
    
  • Growth of timber, food and fuel
    
• Essential processes that we need to survive
  

Aesthetic Reasons

• All organisms have the right to live
  
• Loss of habitat may displace organisms
  
• Humans feel joy from observing nature
  
• Natural systems are very important for our physical, social and mental health
  

Other reasons

• Allowing genetic diversity to decline means we may lose some natural solution to our problems
  
• Nature may hold the answers to some of our problems
  
  • Already adapted species may be carefully bred to produce a transgenic species
    
  • May be able to survive new conditions created by climate change
    
• Nature is a source of potential new medicines
  
  • Range of potential vaccines is entirely unknown
    
  • Huge medicinal potential that needs to be maintained

6. in situ an ex situ methods of maintaining biodiversity

Humans attempt to maintain biodiversity through a variety of methods. In situ methods involve supporting natural ecosystems in the wild. Ex situ methods mean moving endangered species into man-made environments for a more controlled approach.                        
In Situ

• Attempting to minimise human impact on environment
  
• Protecting the environment

Method	Process	Pros	Cons
Legislation	Prevents hunting and land clearing	Prevents any development Prevents human activities	My only be specific to an area Hard to enforce in smaller countries
Conservation Parks	Parks and reserves established Permanently protects biodiversity May even allow ecological integrity to be restored	Permanent protection	Conflict may arise if animals escape
Repopulation	Rebuilding of lost biodiversity Habitats are reestablished in attempts to improve biodiversity	Effective in rebuilding biodiversity	Cost Unknown impact on environment

Ex Situ

• Conservation of endangered species outside of their natural environment
  
• All of these techniques carry the risk of disturbance to the natural environment

Method	Process	Pros	Cons
Zoos	Species held in captive Endangered species may be bred to increase population size Ultimate view of releasing into the wild	Lowers likelihood of extinctions	Animals are not kept in their natural habitat
Seed Bank	Collection of seed samples Aim to collect all known species of plants Examples of rare and important species	Seeds have almost infinite options for use in future	Storage must be controlled Seed viability and germination must be tested annually

7. international & local conservation agreements made to protect species & habitats

Loss of habitat and species is an international problem that affects the world as a whole. International cooperation is therefore essential and achieved through a number of agreements.
CITES

• Convention of International Trade in Endangered Species
  
• Agreed in 1973
  
• CITES aims to:
  
  • Regulate trade in selected species
    
  • Encourage trade does not endanger species
    
  • Permits enforced for trade of less endangered species
    
  • Allow trade for artificially propagated plants
    
• International policies are hard to enforce
  
• Demand almost always has a supply
  

Convention on Biodiversity

• Signed by 150 leaders in 1992
  
• Dedicated to promoting sustainable development
  
• Our requirement for genetic and biological diversity
  
• Aims are:
  
  • Conservation of genetic diversity
    
  • Sustainable use for nature
    
  • Shared access to genetic resources
    
  • Shared transfer of scientific knowledge and technology
    
  • Members must have both ex-situ and in-situ conservation programs
    
  • Encourages co-operation between members
    

EIA

• Under the Rio Convention, all members must undertake an environmental impact assessment before any developments
  
• This aims to:
  
  • Avoid adverse impacts on environment
    
  • Ensure potential environmental impacts are taken into account
    
  • Promote international and national exchange of opinions and information
    

• EIA are mainly carried out at local levels
  
• It is a means of assessing the likely impact of a development
  
• Ensures that local planning authority knows about any potential adverse impacts in the environment
  

Can help developers to develop their proposal and make it more environmentally friendly    ​