the variety of living organisms present in an area
Habitat biodiversity
the number of different habitats found within an area
The greater the habitat biodiversity...
the greater the species biodiversity will be within that area
Species richness
The number of different species living in a particular area
Species evenness
the relative proportion of different species in a given area
Genetic biodiversity
refers to the variety of genes that make up a species
Sampling
can be used to estimate the number of organisms in an area without having to count them all
Random sampling
a sample that fairly represents a population because each member has an equal chance of inclusion
How can you take a random sample- example
1) mark out a grid on the grass using 2 tape measures at right angles
2) use random numbers to determine the x-coordinate and y-coordinate on your grid
3) take a sample at each of the coordinate pairs generated
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 (NRS)
sampling using the organisms that are conveniently available. The weakest form of sampling as it may not be representative of the population.
Stratified sampling (NRS)
the population is divided into a number of strata (subgroups) and weighted based on a particular characteristic.
e.g. divided into male and female.
then random sampling used for that
Systematic sampling (NRS)
select some starting point and then select every kth element in the population
Linetransect- systematic sampling
a line is marked along the ground and samples are taken at specified points.
Belt transect- systematic sampling
2 parallel lines are marked, and samples are taken of the area between the two lines
Sampling bias
A problem that occurs when a sample is not representative of the population from which it is drawn. for example choosing moreinteresting looking flowers in an area.
Chance
the organisms selected may, by chance, not be representative of the whole population.The larger the sample size, the more reliable the result
Pooters- sampling technique
used to catch small insects. suck on a mouthpiece and insects are drawn into the holding chamber via the inlet tube. There is a filter before the mouthpiece to prevent it being sucked into the mouth.
Sweep nets- sampling technique
used to catch insects in areas of long grass
Pitfall traps- sampling technique
used to catch small, crawling invertebrates. a hole is dug in the ground which insects fall into with roof
left overnight
Tree beating - sampling technique
used to take samples of the invertebrates living in a tree or bush large white cloth is stretched out under the tree
the tree is shaken/beaten to dislodge the invertebrates onto the cloth
Kick sampling- sampling technique
used to study organisms living in a river. the river bank or bed is 'kicked' for a period of time to disturb the substrate
a net is held just downstream for a set period of time in order to capture any organisms released into the flowing water
Point quadrat (Plant sampling)
a frame has a horizontal bar - set intervals along the bar long pins can be pushed through the bar to reach the ground, each plant that touches the pin is recorded
Frame quadrat (Plant sampling)
consists of a square frame divided into a grid of equal sectionsthe type and number of species within each section of the quadrat is recorded
Measuring species richness
Various techniques should be used to compile list of species in habitat. Then total is a measure of species richness
Measuring species evenness
Ratios of organisms in a community.
Example:
50 organisms under a log
20 woodlice
15 spiders
15 centipedes
This is even
45 woodlice
5 spiders
This is uneven
Frame quadrat- density
count the number of individual large plants in a 1m x 1m squarequadrat. this gives you the density per square meter. it is an absolute measure.
Frame quadrat- frequency
using the small grids within a quadrat, count the number of squares a particular species is present in.
Frame quadrat- percentage cover
It is an estimate by eye of the area within a quadrat that a particular plant species covers
it is fast
2 ways to increase reliability
take a larger sample size
calculate mean
Estimating animal population size: capture-mark-release-recapture method
compare numbers of marked individuals with number of unmarked in the second sample and then the population size can therefore be estimated
the greater the number of marked individuals recaptured, the smaller the population
species evenness can then be calculated
Abiotic factors
a nonliving condition or thing, as climate or habitat, that influences or affects an ecosystem and the organisms in it
Examples of abiotic factors
wind speed
light intensity
relative humidity
pH
temperature
oxygen content in water
How to calculate biodiversity
Simpson's index of diversity
Simpson's index of diversity
a measure of biodiversity that takes into account both species richness and species evenness
a higher value means there is more diversity
Species diversity
takes into account both the number of different species present (species richness) and the number of individuals of each species
Importance of genetic diversity
Diverse gene pool gives a population more flexibility to survive in a changing environment and is less likely to become extinct
The more genetically diverse a population, the more ways it has to adapt
Factors that increase genetic diversity
mutation
interbreeding between different populations (gene flow)
Factors that decrease genetic diversity
selective breeding (artificial selection)
captive breeding programmes are breeds artificial cloning
natural selection
genetic bottlenecks
founder effect
genetic drift
Polymorphism
the existence of two or more forms of individuals within the same animal species (independent of sex differences)