4.2.1 Biodiversity and Sampling

Practice: Simpson’s index of diversity

Bio-diversity definition

The variety of plant and animal life in the world or in a particular habitat; a high level of which is usually considered to be important and desirable

How is the bio-diversity in tropical, moist regions

• Contain the most bio-diversity as they have:

  • High & consistent energy output (lots of solar radiation, highly reliable rainfall)

  • Stable climate conditions - allows for all year round growth and specialised evolutions

What are the three different forms of bio-diversity

• Habitat biodiversity

• Species biodiversity

• Genetic biodiversity

What is habitat biodiversity

• The number of different habitats found within an area

• Each habitat can support different species

• The more habitat biodiversity within an area, the greater the species biodiversity

What is species biodiversity

• Species richness: The number of different species in a given ecosystem, region or particular area

• Species Evenness: A comparison of the numbers of individuals of each species living in a community.

  • Mathematically defined as a diversity index - a measure of biodiversity which quantifies how equal the community is numerically

What is genetic biodiversity

• Refers to the variety of alleles that make up an individual species (i.e. genetic

  variation)

• Alleles are different versions of the same gene

• The more alleles that exist, the greater the genetic biodiversity

• Greater genetic biodiversity within a species allows for better adaptation to a changing environment

How are habitats sampled

• Selecting and studying a small portion of the habitat carefully, using the numbers of individuals to estimate the population size for the whole habitat

• Strategies include:

  • Random sampling

  • Non-Random sampling (Opportunistic Sampling, Systematic sampling & Stratified sampling)

What is random sampling

• Quadrat placed at randomly (coordinates selected using random number generator) chosen locations in a habitat

• Used to measure abundance/number of a species in an area

What are the advantages and disadvantages of random sampling

Advantages:

• Prevents bias in the data

Disadvantages:

• May not cover all areas of a habitat equally

• Species with a low presence may be missed (underestimate of biodiversity)

What is Opportunistic sampling

Selecting sampling sites or organisms based on convenience e.g. studying only the plants nearest to a footpath

What are the advantages and disadvantages of opportunistic sampling

Advantages:

• Fast, easy & convenient; requires less planning and fewer resources

Disadvantages:

• Highly biased and can lead to an overestimate of biodiversity; not representative of the whole ecosystem

What is systematic sampling

• Belt transect: quadrat placed regularly along a transect line and number of

  individuals recorded

• Line transect: position of species touching a transect recorded

  • Used when there is a change in environmental conditions over the area (eg,from one side of a river to another)

What are the advantages and disadvantages of systematic sampling

Advantages:

• Useful when the habitat shows a clear gradient in an environmental factor

Disadvantages:

• Only the species on the belt or the line may be recorded, other species may be missed (underestimate of biodiversity)

What is stratified sampling

• Dividing a habitat into areas which appear different, and sample each area separately. Within each area, the quadrats would be placed randomly

• For example:

  • If an area consisted of 50% woodland, 30% scrubland and 20% grassland, then 50% of quadrats would be in woodland, 30% on scrubland, 20% on grassland

What are the advantages and disadvantages of stratified sampling

Advantages:

• Ensures all the different areas of a habitat are sampled and species are not underrepresented

Disadvantages:

• Possibility that it may lead to over representation of some areas in the sample

What is animal sampling

• Other techniques only work for plants or animals which are static

• Other methods are used when sampling mobile populations such as:

  • Sweep nets

  • Pooters

  • Pitfall traps

What is the Lincoln Index

• An equation used to measure population size

What is Simpson’s index of diversity

• It takes into account:

  • Species evenness: the number of individuals within species within a certain area

  • Species richness: the number of species present

• A higher ‘D’ value indicates a diverse habitat that will be able to withstand a small change to the environment as it may only affect one species that makes up a small part of the habitat

• Habitats with low genetic diversity e.g. isolated populations include zoo’s, rare breeds, predigrees

What is a locus

The positions of a gene in a genome

What is a polymorphic gene

• A gene with more than one allele

• E.g. The human blood type, metabolic enzymes, haemoglobin types

How is genetic diversity measured

• By calculating the percentage of loci in the population that have more than one allele

• Genetic diversity = (no. of loci with more that allele/ total no. of loci) x 100

• Proportion of polymorphic gene loci = number of polymorphic gene loci/total number of loci

What is the impact of deforestation on biodiversity

• Loss of habitat (habitat diversity)

• Reduction in species richness and/or species evenness (species diversity)

  • Often one type of tree is targeted

• Migration of species to other locations/changing food web (species diversity and genetic diversity)

  • Individuals may need to find other suitable habitats

  • Other species who have not lost their habitats may suffer because they can’t find food or find themselves as more in demand prey

What is impact of agriculture on biodiversity

• Loss of habitat (habitat diversity)

  • Clearing of hedgerows to make bigger fields

  • Replacement of trees with cropland

• Reduction in species richness and/or species evenness (species diversity)

  • Replacement of native species with crop

  • Crops grown of one variety - monoculture (genetic diversity)

• Pollution from pesticides/herbicides/factories

  • Killing non-targets species like bees - important pollinators

  • Eutrophication

What is a mono-culture

• In order to feed an ever growing population, large areas of land are devoted to growing one specific type of crop

• E.g. extensive corn fields in mid-west USA

What are the effects of a monoculture

• Habitat loss: hedgerows are destroyed to make way for larger fields meaning fewer natural habitats for native wildlife

• Loss of local plants and animals: many natural and local plants are destroyed when land is needed to grow food crops

• Loss of heritage (traditional) varieties: can be destroyed by pesticides and herbicides used to increase yields

Describe the impact of climate change on biodiversity

• Loss of habitat (habitat diversity) - e.g. polar ice caps melting

• Reduction in species richness and/or species evenness (species diversity)

• Distribution of species may change as environmental conditions change

Why should biodiversity be preserved

Ecological:

• Avoiding the disruption of food chains/ natural cycles

• Maintaining genetic diversity to enable species to survive

• Protecting Keystone species

Economic:

• Preserving sources of fuel

• Potential future uses by humans (medical/improving crops)

Ethical/Aesthetic:

• Moral/Ethical responsibility

• Tourism/Leisure

What is a keystone species

• A species that has a disproportionately large effect on the ecosystem

• Would have the greatest impact if they were lost

• They are linked (directly or indirectly) to all other species and manage species richness/evenness of the habitat as a whole - interdependence of species

How can biodiversity be protected

• In situ conservation - managing natural habitats

• Ex situ conservation - removing species from their habitats and protecting them in specialised environments

Give examples of in-situ conservation

• Restricting Human Access

• Controlling Poaching

• Supplement feeding

• Reintroduction of species

• Culling or removal of invasive species

• Halting succession:

  • Succession is the gradual change of an ecosystem over time and involves a shift in biotic and abiotic factors

  • This is interrupted to preserve immediate, high-diversity habitats (like heathland)

Advantages In situ conservation

• Maintains genetic diversity of a species

• Species can continue to adapt to changing environmental conditions

• Food chains/webs are maintained

• Protects the habitat rather that just the species

• Cheaper than ex-situ conservation

What are the advantages to ex-situ conservation

• Rare breeds can be protected from predators / changing environmental conditions to allow the species to survive

• Captive breeding programmes can help the species size to increase

• Animals bred in captivity can sometimes be released into the wild

• Samples of plants or their seeds can be kept for research / future

  uses

Give examples of ex-situ conservation

• Botanic Gardens

• Seed banks

• Captive breeding programmes

What are the different parts of the Spearman’s Rank Correlation Coefficient

• n = the number of individuals in the sample or the number of pairs of data

• D(2) = the difference in the rank of the two measurements made on an individual

• Sigma = the sum (total) of

• R will be a number between -1 and +1

  • A negative value for r(s) implies a negative correlation

  • A positive value for r(s) implies a positive correlation

How do you use the Spearman’s Rank Correlation Coefficient

1. Rank each set of data (lowest to highest)

• If there are 2 of the same you create an average rank (if they are the 8th number you rank them both as 8.5 and then the next one as 10)

2. Work out the differences between the ranks

3. Square the differences

4. Word out the sum of all the squared differences

5. Insert that into the formula to get a critical value

What are the different types of Hypothesis’

• Null hypothesis

• Alternate hypothesis

When is an unpaired student’s T-test used

Used if the means have been generated by 2 independent groups i.e. each set of data arise from separate individuals

What is the unpaired student t-test and what each part means

What is a paired students T-test formula

What do the parts of the paired students t-test mean

What is biomass

• Biomass includes all the carbon containing compounds within a organism and so biomass can be equated to energy content

• Energy available at each tropic level is measure in kilojoules per meter squared per year (kJm-² yr-^1)

  • It is measured per year to allow for changes in the photosynthetic production and feeding patterns

How is biomass lost

• At each trophic level, some biomass is lost and so is unavailable to the organism at the next trophic level

• These losses are due to:

  • Organisms need energy for life processes e.g. respiration

  • Dead organisms and waste material are only available to decomposers e.g. parts of animals and plants cannot be digested by consumers

Efficiency of biomass transfer formula

How efficient is energy at the producer level

• Producers only convert a small % of the light energy they receive into chemical energy (biomass)

• This is due to:

  • Approx. 90% of the light that falls on the plant is reflected

  • Other light is transmitted

  • Some of the light is of an unusable wavelength

  • Other factors may limit the rate of photosynthesis

  • A proportion of the energy is used for photosynthesis reactions

What is gross production

• The total light energy that plants convert to organic matter

• Some of this energy is then used for respiration, with the remaining energy converted to biomass e.g. cellulose, proteins, lignin

• The energy converted to biomass is then available for the next trophic level - this is known as the Net Production

  • Net production = Gross production - Respiratory losses

Productivity definition

The rate at which energy passes through each trophic level

Primary productivity definition

The rate at which plants convert light energy into chemical potential energy

Gross primary production definition

The total amount of energy transferred by plants, from sunlight into plant tissues

Net primary production definition

The chemical energy that is left after the plants have supplied their own needs by respiration (i.e. the amount of energy available to pass on to primary consumer)