Unit 4 - Genetic information, variation and relationships between organisms
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Summary AQA A LEVEL BIOLOGY CHAPTER 8 DNA, GENES, PROTEIN SYNTHESIS NOTES
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Unit 4 - Genetic information, variation and relationships between organisms
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AQA
I created these notes throughout y12&13 and used them for my A level 2022 exams. I got a grade 9 in GCSE and am awaiting for my a level biology result. These notes were made using the CGP revision guide, AQA Biology textbook and class notes in order to cover everything in the course. I have also ad...
Unit 4 - Genetic information, variation and relationships between organisms
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10.1 SPECIES & TAXONOMY
21 February 2021
18:31
Species - A group of similar organisms which can reproduce to give a fertile offspring.
If 2 individuals of different species reproduce, the offspring will be infertile.
● Odd number of chromosomes.
● Chromosomes cannot pair, so meiosis cannot occur.
Species is the basic unit of classification.
Members of the same species are similar to each other, but different from other
species.
● Similar genes, so they're similar physically and biochemically.
● Similar immunologically.
● Occupy the same ecological niche.
● Similar courtship behaviour (determined genetically).
Species are universally identified by a binomial system.
● The first name is the generic name, showing which genus the organism
belongs to.
● The second name is the specific name, showing which species the organism
belongs to.
When writing the names using the binomial system:
● They are printed in italics.
● If handwritten, underline the names.
● First letter of generic name is UPPER case.
● Specific name is all in lower case.
● If specific name unknown, can be written as 'sp.'
Courtship behaviour is carried out by organisms to attract a mate of the right species.
Species specific.
● Only members of the same species will respond to the courtship behaviour.
● The more closely related the species are, the more similar their courtship
behaviour.
Courtship behaviour allows individuals to:
● Recognise and ensure that mating occurs with the same species.
● Allows the survival of the species.
● Identify a mate that's capable of breeding, as both partners need to be
sexually mature and fertile.
● Form a pair bond, leading to successful mating and raising of offspring.
, ● Synchronise mating, takes place when max probability of sperm meeting egg.
● Become able to breed.
The female can either have a response allowing the male to continue courtship
action or a response where the male will give up and court another female.
Taxonomy - Biological classification
Classification - Grouping of organisms
There are 2 main forms of biological classification:
Artificial classification:
● Grouping of organisms according to differences that are useful at the time.
● I.e Have wings, don't have wings.
● These features are analogous characteristics, same function but different
evolutionary origin.
Phylogenetic classification:
● Based upon evolutionary origins and relationships between organisms and
their ancestors.
● Uses shared features derived from their ancestors.
● Arranges groups into a hierarchy, groups within larger composite groups with
no overlap.
● Partly based on homologous characteristics, structures with similar
evolutionary origin regardless of their function.
Each group is called a taxon (taxa).
● Taxonomy is the study of these groups and their position in a hierarchical
order, where they're known as taxonomic ranks.
A domain is the highest taxonomic rank and there are 3 which are recognised:
● Bacteria
● Archaea
● Eukarya
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