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