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

• Ecosystems with a high species diversity are usually more stable as they are more resilient to environmental changes

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

• Limited in populations that are very small or isolated which would cause genetic diseases caused by recessive alleles to become more common

What is sampling

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

• Necessary to measure biodiversity in large and complex ecosystems as it would be impossible to count every organism

• 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 are sweep nets

• The nets can be swept across vegetation, e.g. grass or tree branches, to catch flying insects and insects that live on leaves

• After sampling the insects in the net can be counted and identified

What are pitfall traps

• Cans or jars that are sunk into the ground

• Ground-dwelling invertebrates fall into the trap as they walk along the ground, and then cannot climb out again

• A lid ensures that the trap does not fill with rainwater

What are pooters

• Pooters are small plastic or glass containers with two tubes extending from the lid

• The tubes can be used to suck up small invertebrates

  • The first tube is placed over the insect and the second tube is used by the scientist to create suction

• Once inside the container the sampled organisms can be easily viewed and identified

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 the impact of human population growth on biodiversity

• Humans use many resources from the Earth e.g. land, water, wood

• As the human population increases and countries become more economically developed, our requirement for natural resources also increases

• This is having a harmful effect on many aspects of the environment, including aquatic and terrestrial ecosystems, and our atmosphere and climate

• The damage to these ecosystems is negatively impacting the species and habitats contained within them

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:

• Reducing soil depletion (continuous monoculture)

• Preserving sources of fuel

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

Ethical/Aesthetic:

• Protecting Landscapes

• 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 in 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 is the CBD conservation agreement

• The Convention on Biological Diversity (CBD) was signed at the Earth Summit in Rio de Janeiro, Brazil in 1992

• 3 main goals:

  • The conservation of biological diversity by use of a variety of different conservation methods

  • The sustainable use of biological resources

  • The fair and equitable sharing of benefits arising from genetic resources

• The countries that signed the convention agreed to:

  • Design and implement national strategies for the conservation and sustainable use of biodiversity,

  • Organise international cooperation and further international meetings

What is CITES conservation agreement

• Convention on International Trade in Endangered Species of Wild Flora and Fauna

• Global agreement signed by over 150 countries

• Aims to control the trade of endangered species and their associated products

• CITES categorizes endangered species into three forms:

  • Appendix I: species that are endangered and face the greatest risk of extinction - Red panda

  • Appendix II: species that will be facing extinction, unless trade is closely controlled - The Venus fly trap

  • Appendix III: species included at request of the country - The two-toed sloth in Costa Rica

• There are different trading regulations that apply to each appendix

  • 1: trade is banned

  • 2: trade only granted with export permit

  • 3: same as 2 but permits more common

Wha are the limitations of the CITES agreement

• There are several concerns about the efficacy of CITES listings

  • When the trade of a certain endangered species becomes illegal, its price increases

  • The increased economic value of the species can be a major incentive for people to break the law

What is the CSS agreement

• Countryside Stewardship Scheme

• From the 1980s

• Provided funding to farmers and private landowners in England who used environmental management strategies to protect and increase the natural biodiversity on their land

• Was replaced by the Environmental Stewardship Scheme (ESS) in 2005

• In order to qualify for the scheme, farmers and private landowners have to:

  • Provide and protect valuable wildlife habitats such as ponds surrounding farmed areas

  • Ensure their land is managed well

  • Protect any natural resources or historic features on their land

  • Conserve any traditional crops or livestock on their land

  • Provide visitor opportunities so people can learn about the countryside and how important it is in sustaining biodiversity

Move to 6.3.1. 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)