Evolution and taxonomy Flashcards
3 domains
Bacteria, archaebacteria, eukarya
Bacteria
Prokaryotes, ester links plasma membrane lipids
Archaebacteria
Prokaryotes, ether links plasma membrane lipids
Eukarya
Eukaryotes, ester links plasma membrane lipids
Darwin’s main propositions in 1859
- Random, heritable variation between species
- Variation occurs randomly
- Large abrupt changes are rare
- Small variations make more suited for environment are maintained and increase frequency
- Limited resources = survival of the fittest
Weaknesses of Darwin’s propositions
Weaknesses of Darwin’s propositions Time is needed for evolutionary change, nut teacart s 4500 MYA old
Heritability mechanisms unknown
Evidence for Darwin’s propositions
- Artificial selection
- Ecological genetics e.g. peppered moth
- Rapid effects of artificial selection e.g. antibacterial resistance
- Experimental synthesis of new species
- Molecular phylogenetic evidence
- Biogeographical evidence - plate tectonics and continental drift
- Fossil record
Mechanisms for evolutionary change
- Mutations
- Gene flow between populations
- Genetic drift (random changes in allele frequency): founder effect, bottleneck
- Non-random mating e.g. sexual selection
Stabilisation forces
- Stabilising selection e.g. human birth weight
- Directional selection e.g. TXX in gartner snakes protects toxin in newt prey
- Disruptive selection - favour in different directions
Species isolating mechanisms
Ecological - spacial and temporal (pre mating)
Reproductive - permeating (teportal, ethological mechanical) and postmating (prezyogitic and pos-zygotic)
Speciation
- Allopatric - geographical isolation
- Sympatric - reproductive isolation
- Parametric - on edge of species range
Panmaxis
Fully random mating (unlikely)
Interbreedng
Self fertilisation or cross fertilisation of closely relayed
Outbreeding
Higher inter breeding levels
Polymorphic phenotypes
Change in local phenotype - different local environment and selection pressures
Polyploidy
Changes in chromosome completes AA => AAA
Hadean
3800 MYA, high tops, v high CO2, water, no life, organic molecules
Archean
The beginning - 3800-2500 MYA, much ocean, v high CO2, negligible oxygen. First prokaryotes with self rep all marine. Photosynthetic cyanobacteria generate oxygen.
Proterozoic
2500-542 MYA, oxygen deposits build up further, marine eukaryotes 1500 MYA,
Cambrian
542-488 MYA, oxygen levels similar to today, rapid diversification, almost entirely marine (cambrian explosion), earliest vertebrates
Ordovican
488-444 MYA, massive glaciers over Gondwanaland, drop sea level - 75% animal species extinct
Silurian
444-416 MYA, marine life recovered, jawless fish, first terrestrial vascular plants and arthropods
Devonian
416-259 MYA, Most jawless fish extinct, mass extinction of text at end. Terrestrial plants more diverse. First tetrapods
Carboniferous
359-297 MYA, large glaciers, extensive swamp forests, diversity of terrestrial animals increased, flight evolved in insects
Permian
297-251 MYA, Pangea, diverse fauna, lineage leading to mammals, most dramatic animal extinction at end, volcanic activity and decline in o2
Triassic
251-200 MYA, pangea separates, o2 rises, diversification. Mass extinction, possibly due to meteorite
Jurassic
Jurassic 200-145 MYA, early mammals, birds at end. Dinosaurs specialised, many could relate body temp, flight evolved separately in pterosaur reptiles and birds
Cretaceous
145-65 MYA, high sea levels, warm and humid, increase diversity, first flowering plants, mass extinction - massive environmental change, possible due to meteorite
Tertiary
65-1.8 MYA, continental similar to today, first hot and humid then cooler and drier
Quaternaruy
1.8 MYA - dramatic cooling and climate fluctuations, 4 major ice ages
Classification
The way organisms are sorted into taxa
Systematics
Grouping species according to evolutional ancestory
Phylogeny
Evolution history of a group of organisms
Order of taxa
Domain, kingdom, division/phylum, class, order, family, gents, species, subspecies, variety, form
Monophyletic
All living descendants of a single ancestor
Polyphyletic
Descendants for several different ancestors
Paraphyletic
Basis of non-specilast or non-unique characters