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OCR Biology Unit 2 Module 3
Biodiversity…read more

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Key Definitions
Species; is a group of individual organisms very similar in appearance, anatomy, physiology,
Biochemistry and genetics whose members are able to interbreed freely to produce fertile
A Habitat; is the place where an organism lives
Biodiversity; is the variety of life, the range of living organisms to be found
Biological classification; Is the process of sorting living things into groups. Natural
classification does this by grouping things to how closely related they are. Natural classification
reflect evolutionary relationships.
Taxonomy; is the study of the principles of classification
Phylogeny; is the study of the evolutionary relationships between organisms.
Variation; Is the presence of variety- of differences between individuals
Relationship between Classification and Phylogeny; The objective is a classification system that
accurately records the phylogeny. Phylogeny refers to the evolutionary relationship of
organisms; it's a family tree for all life on Earth. These days, classification seeks to work by
grouping organisms into units based on common ancestors. That approach is phylogenetic.…read more

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Biodiversity includes all the different plant, animal, fungus and microorganisms species
worldwide, the genes they contain and the ecosystems they lives in. Biodiversity is not just
about the number of different species. It also represents the degree of nature's variety.
Biodiversity takes into account the number of different individuals and how many places they
can be found.
Biodiversity is about the structural and functional variety in the living world we can consider
it in a number of ways;
· The range of habitats in which species live in.
· The differences between different species e.g. a cat and a tiger. There are both structural
differences and functional differences.
· Genetic variation between individuals belonging to the same species. This is the variation
found within any species that ensures we do not look alike.
In 2007 an organisation made a list of over 1 million species. However there are many
species that have not yet been discovered and it is estimated the number of species on earth
could actually be close to 1.8 million. These figures are only estimates as new species are
being found all the time, evolution and speciation is continuing, many species are
endangered and some are becoming extinct.…read more

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Sampling Plants
Random Sampling means studying a small part of the habitat and
assuming it contains a representative set of species that can be
applied to the whole habitat. It is often more practical than trying
to collect data for the whole habitat. The sample sites must be
chosen at random.
Randomising samples;
· Take samples at regular distances across the habitat
· Use random numbers generated by a computer, to plot coordinates within the habitat
· Select coordinates from a map of the area and then use a GPS system to find the exact position within the
Quadrat, 1m by 1m, First identify the plants found within the frame then measure their abundance. Lower
a ten pointed point frame into the quadrat. Record any plants touching the needles. Use the frame 10
times. So each plant recorded as touching the needle will have a 1% cover. Since one needle may touch
several plants you may find you have 300-400% coverage. Also an abundance scale or a grid could be used.
Transect; stretch a tape measure across a habitat and take samples across the line. You may record plants
touching the transect . Or use a quadrat at regular intervals along the lines (interrupted transect belt) or
use a continuous belt transect where quadrats are used all the way along the line.…read more

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Sampling animals
· Sweet netting ­ walking through the habitat with a stout net. Small insects may be caught.
Empty the net onto a white sheet and identify species. Suitable for low vegetation areas.
· Collecting from trees ­ Spread a white sheet under a branch and knock the tree with your
stout stick. Small animals will be dislodged and will fall onto the white sheet.
· A pitfall trap ­ Bury a small container in the soil. Any small animals or insect moving through
the grass or the soil surface will fall into the container.
· A Tullgren funnel ­ Place the leaf litter in a funnel. A light above the litter dries out the
leaves. The animals fall through the mesh into a jar.
Why sample?
·To study how human activities are effecting the
·Access our environmental impact
·Maintain habitats and reduce the amount of
damage we do to them A pooter…read more

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Measuring Biodiversity
We have to consider 2 things;
1) Species richness; the number of species present in a habitat, This can be measured
2) Species evenness, a measure of the relative numbers or abundance of individuals in
each species. This must be measured Quantitatively.
Simpsons index is a measure of diversity we calculate it using the formula
D = 1-((n/N)2) where n = number of individuals in a species, N= total number of
individuals of all the species.
A high value of Simpson's index indicates a diverse habitat. A small change to the environment
may only effect one species. If the species is only a small part of the habitat, the total number of
individuals effecting in the population will be low. The habitat tends to be more stable and able to
withstand change. A more flexible habitat.
A low value of Simpson's index suggests the habitat is dominated by a view species. A small
change in the environment that effects one of those species could damage or destroy the whole
habitat.…read more

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