Extensive notes tailored to the specification points for OCR 2015 Spec, needed for both the AS and A2 components.
My revision from then got me an A* equivalent raw mark last year, and I received an A* at a2.
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(a) How biodiversity may be considered at different levels.
● To include habitat biodiversity (e.g. sand dunes, woodland, meadows,
streams), species biodiversity (species richness and species evenness) and
genetic biodiversity (e.g. different breeds within a species).
Biodiversity is a measure of all the different plant, animal, fungus and other
microorganism species worldwide, the genes they contain and the ecosystems of
which they form. Biodiversity is essential in maintaining a balanced ecosystem for all
organisms. All species are interconnected- they depend on one another. Therefore it
is about functional and structural variety in the living world; it can be considered on a
variety of levels, including habitat, species and genetic biodiversity.
A habitat- a place where individual species live- is a component in biodiversity-
habitat biodiversity measures the range of habitats, the number of different ones,
within an area. Each habitat can support a number of different species, so in general,
the greater the habitat biodiversity, the greater the species biodiversity will be within
that area. Common habitats in the UK include sand dunes, woodland, meadows and
streams, each of which are occupied by a range of organisms. The UK has a large
habitat biodiversity.
Another, smaller, level at which biodiversity can be considered is species
biodiversity. A species consists of individual organisms that are very similar in
appearance, anatomy, physiology, biochemistry and genetics. Of these individual
groups, the species richness and the species evenness in a habitat can be considered
to determine the range of organisms found in a habitat. Species richness is the
number of species living within a particular area, and species evenness is a
comparison of the number of individuals of each species living within a community.
Both are considered because biodiversity is high where there are a large number of
species. However, if one species dominates the population or there are small
numbers of many species, there is limited diversity in such an area, even if there is a
great species richness.
Even more specifically, the genetic diversity between individuals belonging to
the same species, can be considered in consider biodiversity. The variety of genes
within a species occurs where, for many genes, different alleles exist and are present
in different individuals. This ensures they are not structurally, functionally or
superficially identical, different characteristics are exhibited. This can manifest itself
in the creation of breeds within a species, such as dogs. Dogs have a large genetic
diversity because there are many different species, showing different characteristics,
such as coat colour and length, and they can interbreed to form new ones. When
species have large genetic biodiversities, it allows for better adaptation to a changing
environment, because there are likely to be alleles suited to the change, or resistant
to a new disease.
(b) (i) How sampling is used in measuring the biodiversity of a habitat and the
importance of sampling.
● To include how sampling can be carried out i.e. random sampling and non-
random sampling (e.g. opportunistic, stratified and systematic) and the
importance of sampling the range of organisms in a habitat.
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