Unit 4 - Genetic information, variation and relationships between organisms
Summary
Summary Biodiversity
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Unit 4 - Genetic information, variation and relationships between organisms
Institution
AQA
Summary notes for AQA A-level Biology Biodiversity. Includes clear information on phylogeny, domains, courtship behaviour, diversity (including index of diversity), conservation and agriculture. Summarised from class notes and the official course textbook. From an A* student.
Unit 4 - Genetic information, variation and relationships between organisms
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Biodiversity
Species
The system of classification we use divides living organisms into species.
Species: a group of organisms with similar observable characteristics that can breed together
and produce fertile offspring.
Binomial name
Each different species has a binomial name, made up of its genus and species
2 species can share the same genus and will be more closely
related than those with different genera
Difficulty defining species
A species is often defined in terms of similarities and the ability to produce fertile offspring. There
are a few difficulties with this definition:
• Species are not fixed but change and evolve (mutations/natural selection) over time,
producing new species
• There may be considerable variation within a species e.g. males/females and different
stages of the life cycle
• Some species don’t reproduce sexually
• Members of the same species may be isolated so may never interbreed
• Some species are sterile
Odd number of chromosomes
• Some organisms from different species interbreed to form hybrids with an
odd number of chromosomes. This means they are infertile because:
• Chromosomes cant pair up/don’t have homologous chromosomes
• Chromosome number cant be halved
• Meiosis cant occur
• Sex cells/gametes aren’t produced
Grouping species
Grouping of organisms is known as classification.
Artificial classification
• Divides organisms according to any differences e.g. colour, shape
• These characteristics are described as analogous if they have the same function but not the
same evolutionary origins
Phylogenetic classification
• Based on evolutionary relationships between organisms and ancestors
• Classifies species into groups using shared features derived from ancestors - known as
homologous characteristics
• Arranges the groups into a hierarchy in which groups are contained within larger groups with no
overlap
, Phylogeny:
• Phylogeny is the study of evolutionary history between organisms
• To display this, a phylogenetic tree is used which has evolutionary branches and shows how
closely related organisms are:
Hierarchy
Hierarchy is the placing of smaller groups into larger groups with no overlap.
• Each level is called a taxon
• The act of putting the organisms into the groups is called taxonomy
Mnemonic: Dear King Phillip ,
come over for good soup
Domains
Highest taxonomic rank and are recognised as:
1. Bacteria
2. Archaea
3. Eukarya
Bacteria Archaea Eukarya
single celled prokaryotes single celled prokaryotes One or more eukaryotic cells
No membrane bound organelles No membrane bound organelles Have membrane bound
organelles
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