Linnean classification
Carl Linneaus - Hierarchal classification |
Mnemonic: King Prawn Curry Or Fat Greasy Sausage |
(Domain) |
Kingdom |
Phenus |
Class |
Order |
Family |
Genus |
Species - Organisms able to reproduce to produce fertile offsprings |
Binomial nomenclature - genus and species in italics genus has a capital letter, not species. |
5 kingdom classification
Prokaryotes |
Unicellular |
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No nucleus or membrane-bound organelles |
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Absorb nutrient through cell walls / produce it internally |
Protists |
Mainly unicellular |
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Nucleus + membrane-bound organelles |
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Nutrients through photosynthesis + ingest other organisms |
Fungi |
Uni/multicellular |
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Nucleus + membrane-bound organelles |
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Nutrients absorbed from decaying material |
Plantae |
Multicellular |
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Nucleus + membrane-bound organelles |
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Nutrients photosynthesised |
Animalia |
Multicellular |
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Nucleus + membrane-bound organelles |
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Nutrients ingested |
3 domain classification
Proposed by Carl Woese |
3 domains (bacteria, arches and eukarya)
6 kingdoms (eubacteria, archaebacteria, protists, fungi, plantae and animalia). |
Based on differences in sequence of nucleotides in RNA, lipid structure, sensitivity to antibiotics... |
Domain |
Kingdom |
Other details |
Bacteria |
Eubacteria |
70s ribosomes
Eubacteria = "true bacteria"
found in all environments |
Archaea |
Archaebacteria |
70s ribosomes
Archaebacteria = "ancient bacteria"
Extreme environments |
Eukaryotes |
Protists, fungi, plantae, animalia |
80s ribosomes |
Phylogenetic tree
Show evolutionary relationships. |
Similarities and differences in physical characteristics of species. |
+ Continuous tree - Don't have to fit into one group or other, no discrete taxonomical group. |
+ Hierarchal nature of Linnean system - Suggests same levels are equivalent when actually not necessarily comparable. |
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Natural selection
Variation |
New alleles because of mutations |
Survival |
Selection pressure increases chance of survival for best adapted organisms |
Reproduction |
Successful organisms reproduce (survival of the fittest) |
Genes |
Successful organisms pass on advantageous alleles. Frequency of allele in gene pool increases. |
Time |
Over time, whole population has advantageous allele. Speciation - Can become different species. |
Evidence for evolution
Paleontology (fossil record) |
Allows us to study phylogenetic relationships.
Biases - Incomplete because not all organisms fossilise, specific conditions necessary for fossils formation... |
Anatomical evidence |
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. |
Biochemical evidence |
Differences between proteins - some important molecules are the same in different species (e.g. cytochrome C, rRNA...). |
Embryological evidence |
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. |
Variation
Interspecific variation |
Differences between species |
Intraspecific variation |
Differences within species |
Causes of variation |
Environment |
Sunlight, nutrient, and water availability |
Genetic |
Alleles, mutations, sexual reproduction, meiosis... |
or both |
Types of adaptations
Anatomical |
Body covering
Mimicry
Camouflage
Teeth |
Physiological |
Poison / antibiotic production
Water holding
(Animals - blinking, reflexes...) |
Behavioural |
Survival behaviours (e.g. playing dead)
Courtship
Seasonal behaviours (e.g. migration, hibernation...) |
Explanations for convergent evolution
Convergent evolution |
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. |
Analolgous structures |
Structures that perform the same function but aren't structurally similar (e.g. wings in different animals) |
Founder effect |
Small number of individuals separate to form new colony. Rate alleles become more common. |
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Modern examples of evolution
MRSA |
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 |
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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