Summary
Biology OCR A level Biodiversity Summary Notes
Biology OCR A level Biodiversity Summary Notes
[Show more]
Content preview
1 of 6B11- Biodiversity
4.2.1 Biodiversity
(a) How biodiversity may be considered at different levels.
Key words:
Biodiversity- is the variety of living organisms present in an area.
Habitat biodiversity- the number of different habitats found within an area.
Species biodiversity- the number of different species and the abundance of each species in an
area.
Species evenness- a measure of the relative abundance of each species in an area.
Species richness- the number of different species in an area.
Genetic biodiversity- the variation of alleles within a species (or a population of species).
Habitat biodiversity (e.g. sand dunes, woodland, meadows, streams)
• The number of different habitats found within an area.
• The greater the habitat biodiversity, the greater the species biodiversity will be in that area.
Species biodiversity (species richness and species evenness)
• The number of different species (species richness) and the abundance of each species (species
evenness) in an area.
• The higher the number of species the higher the species richness.
• The more similar the population size of each species, the greater the species evenness.
Genetic biodiversity (e.g. different breeds within a species)
• The variation of alleles within species.
(b) (i) How sampling is used in measuring the biodiversity of a habitat and the importance of
sampling.
Key words:
Sampling- taking measurements of a limited number of individual organisms present in a
particular area.
Random sampling- sampling where each individual in the population has an equal likelihood of
selection.
Non-random sampling- where the sampling is not chosen at random, it can be opportunistic,
stratified or systematic.
Random sampling
• Selecting individuals by chance.
• Each individual in the population has an equal likelihood of selection.
• To decide which organisms to study, random number tables or computer can be used.
• No involvement in deciding which organism to investigate.
Non-random sampling
• Sampling method where the sample is not chosen at random.
• Opportunistic- weakest form of sampling as it may not be representative of the population, it
uses organisms that are conveniently available.
• Stratified- some populations can be divided into a number of strata based on a particular
characteristics.
• Systematic- different areas within an overall habitat are identified, which are then sampled
separately. Systematic sampling is often carried out using a line or belt transect.
• Line transect- involves marking a line along the ground between two poles and taking samples
at specified points, this can include describing all of the organisms which touch the line or
distance of samples from the line.
• Belt transect- provides more information; two parallel lines are marked, and samples are taken
of the area between the two lines.
Sampling animals
• Sweeping nets- used to catch insects in areas of long grass.
, 2 of 6
• Pitfall traps- used to catch small, crawling invertebrates. A hole is dug in the ground, which
insects fall into. Hole must be deep enough that they can’t crawl out and covered with a roof-
structure above so the trap doesn’t fill with rainwater. Traps are normally left overnight.
• Pooters- used to catch small insects, by sucking on a mouthpiece insects are drawn into the
holding chamber via the inlet tube. A filter before the mouthpiece prevents them being sucked
into the mouth.
• Tullgren funnels- used to catch small organisms living in soil or leaf litter. Where a soil or leaf
litter sample is put on a mesh filter at the top of a funnel and a light is shone down onto it.
Organisms move away from the heat created by the light and fall out of the funnel and into a
collecting beaker.
• Kick sampling- used to study the organisms living in a river. The river bank and 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.
Sampling plants
• Frame quadrat- consists of a square frame divided into a grid of equal sections. The type and
number of species within each section of the quadrant is recorded.
• Point quadrat- consists of a frame containing a horizontal bar. At set intervals along the bar,
along the bar, long pins can be pushed through the bar to reach the ground. Each species of
plant the pin touches is recorded.
(ii) Practical investigations collecting random and non-random samples in the field.
(c) How to measure species richness and species evenness in a habitat.
• Species richness is the measure of the number of different species found in a habitat.
• Estimated through a qualitative survey i.e. by recording in a habitat the number of different
species observed.
• Species evenness is a measure of the relative abundance of species.
• Estimated quantitatively, random samples are taken and the percentage coverage of each
species or number of individuals in each area measured.
• If two habitats have equal species richness then a greater species evenness would indicate a
more biodiverse area.
• Large animals can be observed and counted as they are visible as individuals in a habitat.
• Smaller animals a mark and recapture technique is used.
• First set of animals is captured and marked (C1). These animals are then released and later a
second set of animals is captured (C2). Some of the second set of animals will be marked (C3).
• Estimate of the total population= (C1 x C2) / C3
(d) The use and interpretation of Simpson’s Index of Diversity (D) to calculate the biodiversity of a
habitat.
N= the total number of individuals for all species
n= the total number of individuals in a particular species
Interpretation of both high and low values of Simpson’s index of diversity
• High value of the index indicated a diverse habitat where a wide range of species and
organisms live.
• Low value means that the habitat is dominated by one species and a change to the environment
that affects that species would have a large effect on the habitat.
• A change to one species is not likely to have a large effect on the whole habitat, the habitat is
resistant to change.
(e) How genetic biodiversity may be assessed, including calculations.
Key words:
Chromosomes- length of supercoiled DNA, condensed.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller twirlpop. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £3.49. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
70840 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now