Biodiversity

Abiotic Factors

Rainfall

pH

Temperature

Humidity/lack thereof

Presence/level of pollution

Areas with high biodiversity (7)

- Large number of successful species

- Relatively benign climate with more ecological niches

- Presence of many species

- Few specific adaptations to enviroment

- Complex food web

- Change in enviroment has a relatively small effect on the ecosystem as a whole

-High biodiversity index (above 0.5)

Areas with low biodiversity (7)

- Few successful number of species

- Stressful/extreme enviroment with few ecological niches

- Relatively few species live in the habitat

- Very specific adaptations to the enviroment

- Simple food webs

- Enviromental change has a major effect on the ecosystem as a whole

- Low biodiversity index (below 0.5)

Methods of sampling animals (6)

- Pooter

- Sweep net

- Pitfall traps

- Tree beating

- Kick Sampling

- Quadrats (for slow moving animals)

Methods of sampling plants (2)

- Frame quadrat

- Point quadrat

pooter (5)

- Used to catch small insects

- Insects drawn into the holding chamber via the inlet tube

-Filter before the mouthpiece prevents them being sucked in by the mouth

Sweep net

Used to catch insects in areas with long grass.

Pitfall traps

- Used to catch small, crawling inverterbrates e.g. beetles, slugs, spiders etc

- Hole dug into ground which insect falls into.

- Must be deep enough so that the insects cant crawl out.

- Trap must be covered so it doesnt fill up with rainwater

Kick sampling

- Used to study organisms living in a river

- River bank and bed is 'kicked' for a period of time to disturb the substrate

- A net is held downstream for a set period of time in order to catch any organisms released into the flowing water.

Tree beating

- Used to take samples of the inverterbrates living in a tree/bush

- Large white cloth stretched out under the tree.

- Tree is shaken/beaten to dislodge inverterbrates.

- Animals will fall onto the sheet where they will be colected and studied.

Point quadrat

- Consists of a frame containing a horizontal bar

- At set intervals long pins are pushed through the ground along the bar

- Each species of plant the pin touches is recorded

Frame quadrat

- Square frame divided into equal grids

- Type and number of species within each grid is recorded

How do you collect the most valid and representative sample of ana area with a quadrat?

- Quadrats should be used following arandom sampling technique

- To study how the presence and distribution of organisms across some land varies, quadrats can be placed systematically along belt/ine transect

Three main ways of using frame quadrats

DENSITY - If individual large plants can be seen clearly, count the number of them in a 1m by 1m square quadrat. (density per metre). Gives ABSOLUTE measure.

FREQUENCY - used to study biodiversity in grassland. If each gird represents 1% and there is 1 buttercup in 65/100 grids then the frequency of occurence of buttercups would be 65%.

How to get an average vaue of a particular organism per metre squared.

calculate mean of individual quadrat results.

How to work out total population of an organism in an area that has been sampled.

multiply mean value per petre squared by the total area.

Sampling

Can be used to estimate the number of organisms in an area without counting them all.

Number of individuals of a species present in an area = ABUNDANCE

Can be used to measure a characteristic of an organism

Results of the sample can be used to make

Generalisations/estimates about the ...number... of organisms

Generalisations/estimates about the ...distribution... of organisms

Measured ...characteristics... of an organism. E.g. Sample of 200 wheat plants found the average height to be 50cm.

Sampling is necessary because we can't usually gather data from the entire population due to:

Large/inaccessible population (it's impossible in most cases to study the actual entire population)

Lack of resources

Sampling is the only method available when data gathering process damage the item from which we require data.

Random sampling

Selects individuals by chance

Each individual in the population has an equal likelihood of selection.

Random number tables/computers used.

You have no involvement in deciding which organisms to compare.

Tyes of non random sampling

- Opportunistic

- stratified

- Systematic

Opportunistic

Uses organisms that are conveniently available.

Weakest form of sampling as it may not be representative of the whole population.

Stratified

Population divided into stratas (sub groups) based on a particular characteristic.

Random sampling is taken from each strata proportional to its size.

Advantages of stratified sampling

Minimises sample selection bias.

Ensures certain population segments are not over/under represented.

Disadvantage of stratified sampling

Unusable when you can't classify every member of the population into a sub group.

Systematic sampling

Different areas within an overall habitat are identified and sampled separately.

E.g. May be used to study how plant species change as you move inland from the sea.