ALEVEL BIOLOGY- Biodiversity

Biodiversity

The variety of living organisms in an ecosystem

Importance of Biodiversity

• Essential to maintain a balanced ecosystem

• Species are interconnected

• We rely on ecosystem for survival (yet human activity can lead to reduction in biodiversity)

Ecosystem

The area inhabited by a species. It includes physical/non-living (abiotic) factors as well as living (biotic) factors.

Niche

The role of the organism in its environment, both the physical and environmental conditions it requires (like temperature or terrain) and the interactions it has with other species (like predation or competition)

Community

A group or association of populations of two or more different species occupying the same geographical area at the same time.

Habitat

An environment where an organism lives. It contains all an animal needs to survive such as food and shelter

Habitat Biodiversity

The number of different habitats found within an area e.g. coastal area might contain sand dunes, mudflats, beaches and salt marshes

Species Biodiversity

Not just the number of different species. Includes number of individual and how many places they are found in.

Takes into account species richness and species evenness.

E.g. -Wild Meadow – lots of plants per metre2

-Lawn – may have lots but dominated by one main spp.

Genetic Biodiversity

Variety of genes that make up a species.

e.g. dog breeds

Species richness

The number of different species living in a particular area.

Species Eveness

The degree to which the species are represented.

Estimating Species Evenness- Plants

•Appropriate sampling method

•Count number of plants per unit area

•Percentage cover

•Direct count possible if larger plants

Estimating Species Evenness- Animals

•Direct count for larger animals

•Mark-release-recapture for smaller animals

•Sample-sift-count soil organisms

•Netting for aquatic organisms

Sample

A limited number of things, such as a group of 100 people or 50 pebbles on a beach.

Population

The total number of organisms within a certain habitat at a certain time.

Representative

How closely the relevant characteristics of the sample match the characteristics of the population.

Bias

An inclination or prejudice towards or against a specific finding or outcome.

Individuals

Individuals samples may not be representative of the population.

Sampling

Select a sample which is representative of the population or to estimate the number of organisms in an area.

Types of Sampling

• Random

• Non-random

  • Opportunistic

  • Stratified

  • Systematic

Random Sampling

Sampling where each individual in the population has an equal likelihood of selection

How?

1. Mark out a grid across your area.

2. Use a random number generator to determine your x and y coordinates,

3. Take a sample at each coordinate.

Non-random sampling

An alternative sampling method to random sampling, where the sample is not chosen at random. It can be opportunistic, stratified or systematic.

Opportunistic Sampling

• Sampling using the organisms that are conveniently available.

• The weakest form of sampling as it may not be representative of the population.

Stratified Sampling

• Sampling where populations are divided into sub-groups (strata) based on a particular characteristic.

• A random sample is then taken from each of these strata proportional to their size.

Systematic Sampling

• Different areas of a habitat are identified and sampled separately.

• Often carried out using a line or belt transect.

Line Transect

A tape or string is laid along the ground in a straight line between two poles. Sampling is rigorously confined to organisms that are touching the line.

Belt Transect

Similar to the line transect method but a quadrat is laid down along the string and species populations are monitored. This gives information on abundance as well as presence, or absence of species.

How to avoid sampling bias?

Random Sampling

How to avoid selecting organism by chance?

Increasing sample size

Animal Sampling Technique

• Pitfall Trap

• Pooters

• Kick Sampling

• Sweep Nets

• Tullgren Funnel

Sweep Nets

Large, strong nets with a fine material are used to catch flying insects and insects that live in the long grass.

How? Sweep the net back and forth through the grass

Pitfall Trap

Container buried into the ground used to catch ground-dwelling insects and other invertebrates as they fall into the trap

Pooters

Small containers with two tubes sticking out that are used to suck up small insects and other small invertebrates,

Tullgren Funnel

Funnel with a lightbulb above and a container below that collects invertebrates that live in leaf litter or soil.

How? Leaf litter/soil is placed in the funnel and the light and heat forces the invertebrates to move down until they drop into the container.

Kick Sampling

Used to catch freshwater invertebrates living in streams or rivers. The net is placed in the stream-bed and water flows into it. Invertebrates are carried by the stream into the net.

Mark-Release Recapture

For a single species in the area:

1) The first large sample is taken. As many individuals as possible are caught, counted and marked in a way that won’t affect their survival e.g. if studying a species of beetle, a small amount of brightly coloured non-toxic paint can be applied to their carapace (shell)

2) The marked individuals are returned to their habitat and allowed to randomly mix with the rest of the population

3) When a sufficient amount of time has passed another large sample is captured

4) The number of marked and unmarked individuals within the sample are counted

5) The proportion of marked to unmarked individuals is used to calculate an estimate of the population size

Formula for Mark-Release-Recapture

N = (n1 × n2) ÷ m2

Where:

N = population estimate

n1 = number of marked individuals released

n2 = number of individuals in the second sample (marked and unmarked)

m2 = number of marked individuals in the second sample

Quadrats

Suitable for plants or slow-moving animals. They can be different sizes and can be laid onto the ground where you can measure the abundance or percentage cover of species present.

3 ways of describing the amount of each species within a frame quadrat:

Density

Percentage cover

Frequency

Density

Count the number of individual plants. This is an absolute measure, not an estimate.

Percentage Cover

Use the small square within the grid, count the number of squares the particular species is in.

Frequency

It is an estimate by eye of the areas a particular species covers.

Simpsons index

àUsed to quantify the biodiversity of an area.

n = number of individuals of a particular species (or % cover)

N = the total number of all individuals of all species

Σ means ‘sum of’

A value between 0 and 1 is calculated

– a value nearer 1 demonstrates greatest diversity.

Why is Simpson’s Index a better indicator of biodiversity than richness or evenness alone?

Takes into account both (number of difference species (richness) / how many of each: evenness), instead of one but not the other.

Genetic Biodiversity

Variety of genes that make up a species

• Gene pool

• Different versions of genes- alleles

• more alleles= more genetically biodiversity

• e.g. different dog breeds

Importance of genetic biodiversity

Greater biodiversity → more likely to adapt to changes in environment → less likely to become extinct

More likely some organisms will carry advantageous alleles enabling them to survive and reproduce.

Gene pool

A gene pool is made up of all the genes and their different alleles present in an interbreeding population.

Different factors affect changes in allele frequency leading to evolution of a population.

Genetic Diversity

• Found where there is more than one allele for a particular locus.

• This leads to greater variation and greater genetic differences between gametes

Allele/ Genetic Variant

A version of a gene.

Locus

the position of that gene on a chromosome

Polymorphic Gene Locus

a locus that has more than 2 alleles

Factors that increase Genetic Biodiversity

• Mutations

  • New allele

  • More alleles = increase biodiversity

• Interbreeding

  • Mixing populations which then breed with each other

  • Transfer of alleles

  • Known as ‘gene flow’

Factors that decrease Genetic Biodiversity

• Selective breeding

  • ‘artificial selection’

  • Select individuals based on characteristics and breed them together.

    E.g. pedigree

• Captive breeding programmes

  • Small number of captive individuals of a spp. Available for breeding.

• Rare breeds

  • A particular breed of animal or plant with characteristic becomes less popular, only a small number of individuals remain/ are available for breeding.

  • As a result of selective breeding

• Artificial cloning

  • Asexual reproduction

• Natural selection

  • Alleles with less advantageous characteristics will decrease over time

• Genetic bottlenecks

  • An event (e.g. drought, disease) reduces gene pool

  • Only alleles of surviving individuals are available to reproduce to produce offspring

• Founder effect

  • Small number of individuals create a new colony which is geographically separate from og. population

  • New population will have a small gene pool

• Genetic drift

  • Random passing off alleles to offspring → frequency of allele occurrence will vary, could lead to complete eradication

Measuring genetic biodiversity

Proportion of polymorphic gene loci = num, of polymorphic gene loci/ total number of loci

Human activities affecting biodiversity

• Habitat destruction

• Pollution

• Climate change

• Over harvesting

• Killing for protection

• Killing to remove competitors

• Introducing non-indigenous species

Human Population Growth

• Increasing at a dramatic rate

• To support increasing populations, these main problems occur:

  • Deforestation

  • Agriculture

  • Climate Change

Deforestation

• Directly reduces the no. of tress in an area, if only one tree is felled, species diversity decreases

• reduces animal species in an area, animals are forced to migrate to other areas, increasing biodiversity in that area

Agriculture

• Selective breeding → removing additional alleles → reducing biodiversity

• Monoculture → farms specialising in the production of of only one crop → decreases biodiversity

  • Few animals will be supported by just one species of plant

  • Achieved through intensive farming

• Use of pesticides and herbicides → directly and indirectly reduces biodiversity (indirectly, removing food source)

Climate Change

• Less genetic biodiverse pops. able to cope with change

• So, populations move to follow climate that suit them, here they may have limited food and it may not be ideal conditions

• Migrations of populations, communities and ecosystems can be obstructed by major human development and geographically challenges e.g. mountains, great bodies of water

Reasons to maintain Biodiversity

• Aesthetic

  • protecting a beautiful environment for people to live in

• Ecological

  • Protecting keystone species

  • Interdependence- species depend on each other for survival

  • Maintaining genetic resource

• Economic

  • less ££ on conservation

  • natural resources have a range of uses (e.g. medicine)

  • promotion of tourism

Conservation and e.g.

Active human management of an ecosystem to maintain biodiversity

E.g. replanting trees, culling deer, burning heathland

Preservation and e.g.

Protecting an area by restricting/ banning human interference to maintain ecosystem in its original state

E.g. fenced off areas, marine conservation zones, banning access to newly found caves

Extinct defintion

No organisms exist anywhere in the world

Extinct in wild

Organisms only exist in captivity

Endangered

Organism in danger of extinction

Vulnerable

A species that is considered likely to become endangered in the near future

In Situ Conservation and e.g

Conserving species in their natural habitat. Also maintains evolutionary adaptions and interactions with other species e.g.

• Legislation

• National parks

• Sites of Special Scientific Interest- some of the best wildlife and geological sites In UK

• Marine conservation zones

Ex Situ Conservation

Conserving species outside their natural habitat

E.g

• Storing genetic material

  • Sperm freezing

  • Artificial insemination

  • IVF + embryo transfer

• Botanic gardens

• Seed banks

  • Storage allows repopulation, can be used in natural disasters