A revision summary of OCR A level Biology Classification & Evolution 4.2.2
Made by a student who achieved A* in A level Biology.
Covers all the points within the OCR Biology Specification.
Condenses 3 OCR specification books and class notes.
Classification Evidence for new classification kingdoms
Phylogeny – study of evolutionary relationships of - Originally classified into plant & animal kingdom (both single-celled)
molecular similarities (DNA/ RNA) shown through Phylogeny - Electron microscope revealed further details inside cells
tree - Single celled organisms shared both plant & animal features
- Common ancestor – point at which two species started to Biological molecules for classification
evolve separately. - Assumes earliest living organisms had identical biological molecules.
- Monophyletic – belong to the same phylogeny group - Differences in biological molecules are a result of evolution
Biological classification- process of sorting living things into - More similar the molecules, the more closely related, less separately
groups evolved.
Taxonomy – classifying by observable characteristics Cytochrome C – protein used in respiration
Hierarchical system – organising by groups; large groups are - Compare sequence of aa in Cytochrome C from 2 different organisms. The
subdivided. more similar the sequence the more closely related.
Taxonomic groups - (King, Philip, Called, Out, For, Good, DNA sequences – DNA code is universal = same base sequence will code for
Soup) same protein in every organisms.
- Domain – Archaea, Bacteria, Eukarya - Mutations cause change, compare DNA sequence, more mutations, more
- Kingdom – Prokaryotae, Protoctista, fungi, Plantae, separately evolved.
Animalia.
- Phylum – groups of organisms with same body plan.
- Class – group with same general traits (no. of legs) New classification - 3 Domains & 6 Kingdom
- Order – additional similar information e.g. feeding Domains – each contains unique ribosomal RNA polymerase.
mechanism Bacteria Archaea Eukarya
- Family – group of closely related genera Prokaryotes Prokaryotes Eukaryotes
- Genus – groups of closely related species. 70s ribosomes 70s ribosomes 80s Ribosomes
- Species – organisms that can interbreed to produce fertile Most common Live in extreme environments Membrane-bound organelles
offspring, all occupy the same niche, some variation. - Different RNA polymerase, CSM, flagella, DNA
Binomial naming system – naming organisms by Genus & replication – not histones in bacteria.
species
- Universal recognition of the organism Archaebacteria Animalia, Plantae, Fungi,
Eubacteria
Protoctista
Kingdom Prokaryotes Protoctista Fungi Plantae Animalia
s
Cell type Prokaryotic Eukaryotic Eukaryotic Eukaryotic Eukaryotic
Single-cellular Single-celled Single-celled & multi Multicellular Multicellular
DNA No nucleus - Circular Nucleus – linear DNA Nucleus – linear DNA Nucleus – linear DNA Nucleus – linear DNA
DNA DNA associated with DNA associated with DNA associated with DNA associated with
Naked DNA histones histones histones histones
Organelle No membrane bound Membrane-bound Membrane-bound Membrane-bound Membrane-bound
s Smaller ribosomes Chloroplasts (photosy) NO photosy Chloroplasts (photosy)
Structure Cilia/ undulipodium Hyphae grow into Cilia, flagella
ground
Cell wall No Chitin Cellulose No
Feeding No visible feeding Autotrophic, Saprophytic Autotrophic Heterotrophic
mechanism Heterotrophic, parasites Food stored as glycogen Food stored as glycogen
Example Bacteria - e.coli Algae’s & Amoeba Yeast Trees, grasses, All mammals
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