Science GCSE, B1 Topic 1 - Variation

Four pages on variation - the first topic of GCSE biology 1

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  • Created by: Dottie
  • Created on: 15-04-12 12:29
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Living organisms are first classified into kingdoms ­ animals, fungi, plants, prokaryote, and
Then they are broken down into smaller and smaller groups in this order ­ kingdom, phylum, class,
order, family, genus and species.
Animals are broken down into vertebrates (animals with backbones) and invertebrates (animals
without backbones). Scientists put them into these groups based on three things ­ how they obtain
oxygen (absorbed through the skin, gills or lungs), how they regulate internal body temperature
(pokilotherms or homeotherms) and how they reproduce (viviparous or oviparous, internal
fertilisation or external fertilisation).
Some organisms are difficult to classify. This might be because ­ they have characteristics from many
species (e.g. euglena), members of the same species might look alike (e.g. not all breeds of dog look
the same), a ring species (a group of related populations living in neighbouring areas ­ the
populations closer together can breed but the ones further apart cannot) may be formed and if a
male from one species breeds with a female from another species a hybrid is born (according to the
species definition the hybrid should be infertile but sometimes they can reproduce and their
offspring would be difficult to classify.
The binomial naming system is the scientific two-part name for every living organism (e.g. Homo
sapiens are modern humans). The first part of the name refers to the genus and the second part
refers to the species. This helps to ­ identify species (it avoids confusion when different names mean
different things in different languages), study species (by identifying and naming species, scientists
can share information on them), conserve species (it's easy to presume that two different species
are the same when they're actually different) and to target conservation efforts (scientists can
protect areas that have a great variety of different species).
Keys can be used to identify creatures.
For example:

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There is lots of variation (differences) between members of the same species. These are caused by
two things: genes and the environment.
Genetic variation ­ characteristics inherited by your parent's genes (genes are codes on the
chromosome inside your cells that control aspects of what you will look like.…read more

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Organisms living deep in the sea have adapted to be able to survive in the dark cold waters -
Some are able to emit light (attracting prey) they often have huge mouths, huge eyes and
long feelers to locate prey
Organisms living in polar regions have also adapted - Polar bears have a thick layer of
blubber for insulation, a hairy coat to trap a layer of warm heat, greasy fur which prevents
cooling, big feet (which spread their weight and stops them from sinking…read more

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Inside every human body cell is a nucleus which controls the rest of the cell. Inside the nucleus are 46
chromosomes (23 pairs). Chromosomes carry DNA (Deoxyribonucleic acid) and genes are found on
this DNA.
There can be different versions of the same gene. These are called alleles. As there are two copies
of each chromosome, there are two copies of the allele. These alleles are might be the same or
different.…read more

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What is discontinuous variation?
8) What is speciation? Explain how geographical isolation can lead to speciation
9) What is an allele?
10) Give two symptoms of:
a. Cystic Fibrosis
b.…read more



A concise, well written set of notes with a fair amount of detail on variation,speciation, classification and genes with  a useful set of short questions at the end. These would be suitable for any GCSE Biology or science student ending to study these topics.

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