Fossils: found

Evolution unthinkable in old times

Georges Guvier: sedimentary fossils --> species found in different times according to sediment layers --> catastrophic events: floods, volcanic eruptions --> fossilised --> old ones dead --> others replace them

Jean Baptiste Lamark: new organisms evolve new traits --> pass on beneficial traits to new generations

Charles Darwin: 1831 British HMS Beagle sent out to map out shoreline of South America --> young naturlist --> Charles Lyell: Principles of Geology --> slow gradual changes of geology --> Theory of uniformitarianism: slow changes shape

Galapagos island: new species of tortoises, diving iguanas & finches (13 species with different beaks for different food sources) --> why such large variations in such small area?

1858: Alfred Wallace in support of paper --> 1859: On the Origins of Species by natural selection by Charles Darwin

Evolution process carried out by natural selection --> Mendel laws of hereditary --> Thomas Hunt Morgan: chromosomal theory of inheritance -->

Natural selection: reproduction > environment cannot support --> limited resources: food, water, space, predation --> ind. best adapted to the environment --> able to pass traits --> over time, these traits become more dominant

Gene: basic unit of hereditary --> on DNA strand + proteins = chromosome --> 1 chromosomes = many genes -->

Genotype: genetic make-up

Phenotype: physical characteristics of an organism

Genome: trasnlation of genetic code & protein synthesis

Alleles: different forms of the same genes (e.g. hair color gene: many alleles - black, blond, red) --> each allele: exact location (loci) on both chromosomes --> homozygous: same alleles on both loci --> heterozygous trait for different alleles on loci

Dominance: complete dominance --> dominant allele expresses itself over the recessive allele --> incomplete dominance: offspring phenotype a mixture of parental traits --> co-dominance: pheotype displays both traits

Natural selection determines the frequency of alleles & the traits for which they code --> physical traits that enable survival in the environmental context are more likely to be passed on

Natural selection forms: 1) directional selection: one extreme of a phenotypic trait becomes favoured --> 2) stabilising selection: average form of a phenotypic trait is favoured (under stable environment when a species is well-adapted to its surroundings) --> 3) disruptive selection: rare, either extreme is more favourable to the average trait

Microevolution: the changes of allele frequencies in the population over time (with stable environment)

Genetic drift: change in allele frequnencies due to random events --> bottleneck effect: genetic drift caused by random reduction of population members to a small number

Founder effect: genetic drift caused by geographical differentiation

Gene flow: spread of different genes or gametes across populations with different alleles

Mutation: change in genetic sequence --> 1 in 1million gametes --> 100 mutant genes daily

Non-random mating: same population --> increase level of occurrence of recessive genes --> increased risk of dehabilitative traits & diseases

Microevolution within natural selection: heritable variation enables species to adapt to changing environments

Variation: 1) quantitative: in degrees, polygenic: control by more than a single gene --> 2) discrete variation: control by one gene: either/or trait

Variation sources: 1) mutation: a change in genetic sequence is usually harmful, but sometimes useful, depending --> 2) recombination: most variations --> new combinations allow new possibilities --> how it is preserved?: diploid chromosomes --> more likely heterozygote protection --> to preserve present advantageous genes --> less likely poorer genes

Balanced polymorphism: preserved variation through --> natural selection which favours heterozygotes over homozygotes

Organisms to both survive & reproduce

Allopatric speciation: separation of species members by geographic barriers --> genetic drift occurs --> emergence of multiple species from common ancestor

Speciation equilibrium: 1) gradual: slow changes --> 2) punctuated: sudden changes, then no change --> combination of both

Fossil dating: index fossils (hard shells in 1 layer of rock, crude method, of certain age) --> radioactive dating: absolute dating using isotopes of atoms - unstable decay into stable atoms by half-life (carbon-14 to carbon-12: 5700 years half-life, less carbon-14 means older fossil) --> potassium-40 into Ar-40 over 1.3million years -->

Macroevolution: significant changes --> preadaptation: development of novel features through refinement of existing ones -->

Homologous structure: derived from common ancestral structure

Analogous structure: derived independently from no common ancestral structure

Vestigial organ: no longer of present use, but carried in DNA of this structure (e.g. our appendix & eyes of fish)

Embryological development: similar embryo

DNA shows how similar different organisms are

Extinctions: 1) Permian extinction: 248million years ago, 90% --> 2) Cretaceous extinction: 65million years ago, 50%

Continental drift: Pangea --> 250 million years ago --> seafloor drifting --> Permian --> asteroid ash found --> Cretaceous