This is a cheat sheet based on the OCR A Gateway Biology A level spec, Chapter 10 module 4. Specification reference: 4.2.2
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Carl Linneaus - Hierarchal classification
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Mnemonic: King Prawn Curry Or Fat Greasy Sausage
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(Domain)
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Kingdom
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Phenus
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Class
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Order
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Family
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Genus
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Species - Organisms able to reproduce to produce fertile offsprings
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Binomial nomenclature - genus and species in italics genus has a capital letter, not species.
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Prokaryotes
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Unicellular
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No nucleus or membrane-bound organelles
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Absorb nutrient through cell walls / produce it internally
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Protists
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Mainly unicellular
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Nucleus + membrane-bound organelles
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Nutrients through photosynthesis + ingest other organisms
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Fungi
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Uni/multicellular
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Nucleus + membrane-bound organelles
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Nutrients absorbed from decaying material
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Plantae
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Multicellular
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Nucleus + membrane-bound organelles
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Nutrients photosynthesised
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Animalia
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Multicellular
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Nucleus + membrane-bound organelles
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Nutrients ingested
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Proposed by Carl Woese
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3 domains (bacteria, arches and eukarya)
6 kingdoms (eubacteria, archaebacteria, protists, fungi, plantae and animalia). |
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Based on differences in sequence of nucleotides in RNA, lipid structure, sensitivity to antibiotics...
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Domain
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Kingdom
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Other details
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Bacteria
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Eubacteria
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70s ribosomes
Eubacteria = "true bacteria" found in all environments |
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Archaea
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Archaebacteria
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70s ribosomes
Archaebacteria = "ancient bacteria" Extreme environments |
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Eukaryotes
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Protists, fungi, plantae, animalia
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80s ribosomes
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Show evolutionary relationships.
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Similarities and differences in physical characteristics of species.
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+ Continuous tree - Don't have to fit into one group or other, no discrete taxonomical group.
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+ Hierarchal nature of Linnean system - Suggests same levels are equivalent when actually not necessarily comparable.
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Variation
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New alleles because of mutations
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Survival
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Selection pressure increases chance of survival for best adapted organisms
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Reproduction
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Successful organisms reproduce (survival of the fittest)
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Genes
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Successful organisms pass on advantageous alleles. Frequency of allele in gene pool increases.
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Time
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Over time, whole population has advantageous allele. Speciation - Can become different species.
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Paleontology (fossil record)
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Allows us to study phylogenetic relationships.
Biases - Incomplete because not all organisms fossilise, specific conditions necessary for fossils formation... |
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Anatomical evidence
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Homologous structures - Structures that look different (and may have different purposes) but have the same underlying structure (e.g. forelimbs in vertebrates).
Example of divergent evolution - common ancestors with different adaptations. Closely related species in different habitats. |
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Biochemical evidence
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Differences between proteins - some important molecules are the same in different species (e.g. cytochrome C, rRNA...).
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Embryological evidence
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Similarities in embryos between species. Shows they develop in a similar way (e.g. human and fish embryos both have gills).
Evolutionary history can be traced through embryonic development. |
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Interspecific variation
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Differences between species
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Intraspecific variation
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Differences within species
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Causes of variation
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Environment
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Sunlight, nutrient, and water availability
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Genetic
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Alleles, mutations, sexual reproduction, meiosis...
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or both
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Anatomical
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Body covering
Mimicry Camouflage Teeth |
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Physiological
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Poison / antibiotic production
Water holding (Animals - blinking, reflexes...) |
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Behavioural
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Survival behaviours (e.g. playing dead)
Courtship Seasonal behaviours (e.g. migration, hibernation...) |
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Convergent evolution
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Different species start to share similarities, adapt in a similar environment / selection pressures.
e.g. Marsupials (in Australia) and placental mammals (USA) are species that resemble each other and because adapted in a similar environment. |
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Analolgous structures
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Structures that perform the same function but aren't structurally similar (e.g. wings in different animals)
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Founder effect
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Small number of individuals separate to form new colony. Rate alleles become more common.
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MRSA
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Variation - Some resistant to antibiotics
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Selection pressure - Antibiotics
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Antibiotic-resistant bacteria survive, advantageous alleles are passed on
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After generations, more S. aureus becomes resistant to antibiotics.
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Peppered moths
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Variation - Some white, some black
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Selection pressure - Change in tree colour because of industrial revolution.
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White ones survive pre-revol., black ones survive during and white ones again after.
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Moths therefore change colour through generations to match tree colour.
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
