Summary
Summary Classification and Biodiversity
- Module
- Biological Molecules
- Institution
- PEARSON (PEARSON)
Detailed notes following from the Biology B Edexcel textbook with the specification points and notes underneath - A level course
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TOPIC 3Classification and biodiversity
Classifi cati on
i Know that the classification system consists of a hierarchy of domain, kingdom, phylum, class,
order, family, genus and species.
Taxonomy – the science of classification of living things
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
King Peter Called Out For Great Scientists
ii Understand the limitations of the definition of a species as a group of organisms with similar
characteristics that interbreed
to produce fertile offspring.
species – a group of living
organisms with similar
characteristics that interbreed
to produce fertile offspring
(can vary from place to place
with different adaptations but
grouped under same species
e.g. left)
iii Understand why it is often difficult to assign organisms to any one species or to identify new
species.
Binomial system of naming – developed by Linnaeus; genus name written first with capital and
species name written after, e.g. homo sapiens
, There is no known universal ‘library of living things,’ therefore many organisms have been
discovered more than once. The models of classification are still under debate and many scientists
don’t agree on the modern systems.
iv Understand how gel electrophoresis can be used to distinguish between species and determine
evolutionary relationships. – don’t need to know until next year
Conserved gene – gene that remained unchanged throughout evolution e.g. hox genes that help lay
out basic body forms of many animals and set up head to tail organisation.
Gel electrophoresis – a technique of separating charged ions in a fluid by applying a potential
difference
Method:
Preparation
1. Sample of DNA collected, and genome cut up using restriction enzymes
OR
2. Cut a region of conserved DNA using restriction enzymes (assume conserved DNA has
changed very little between species due to mutations over time, and there is no change to
restriction sites);
3. Amplify DNA using PCR; separate by gel electrophoresis.
Gel Electrophoresis
1. Agarose and buffer are mixed and microwaved to create a gel which is poured into a mould
with a comb places into it with holes for DNA to be inserted;
2. This cools and then comb is removed; gel placed in gel electrophoresis box and buffer
solution placed in (this conducts current);
3. Dye added to DNA before samples inserted into holes using micropipette to increase
viscosity of sample and allow migration of sample through gel;
4. DNA markers (ladder) with fragments of a known length are added so can be used to predict
the size of the fragments in the samples;
5. Electrical current turned on with side where DNA placed being negatively charged and
opposite side positive;
6. Phosphate backbone in DNA is negative so pulled to positive side and DNA repel negative
charge initiating movements;
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