state 3 sources of evidence for evolution
- palaeontology
- comparative anatomy
- comparative biochemistry
what is palaeontology
study of fossils
what is comparative anatomy?
study of similarities and differences between organisms anatomy
what is comparative biochemistry?
study of similarities and differences between chemical makeup of organisms
explain how the age of fossils can be determined
- over time, sediment deposit forms different layers (strata) of rock
- correspond to different geological eras
- within different strata - fossils different
- so sequence from oldest to youngest can be established
explain how the fossil record provides evidence for evolution
- fossils of simplest organisms in oldest rocks, complex organisms in more recent rocks - supports theory that simple organisms gradually evolved into complex ones
- sequence in which organisms found matches evolutionary links to each other (plants appear before animals - animals require plants to survive)
- analysis of anatomy of fossils studied to show how closely related organisms have evolved from same ancestor
- allows relationships between extinct and living organisms to be investigated
explain how comparative anatomy provides evidence for evolution
- study of similarities and differences in anatomy of different living species
- example: vertebrate limbs structures very similar - same bones adapted to carry out range of different functions
- led to theory that all vertebrates evolved from common ancestor
define homologous structures
structure that appears superficially different but has the same underlying structure
define divergent evolution
process where groups from same common ancestor evolve and accumulate differences - forms new species
explain how comparative biochemistry provides evidence for evolution
- cytochrome c and rRNA studied
- they remain almost unchanged among species throughout time
- slight changes that occur can help identify evolutionary links
- species with most similar structures - more closely related than those w different structures
- to check how closely related - compare molecular sequences of a particular molecule (order of DNA bases or amino acid sequence) - can estimate the point at which the species last shared common ancestor
summarise how darwin formulated the theory of evolution by natural selection
- darwin: observations on finches in Galapagos islands - different islands had different finches which were similar, closely related but beaks and claws different
- darwin realised that beak structure was linked to food available on island
- conclusion - bird born with more suitable beak will survive longer, have more offspring and pass on the characteristic until all have it
summarise how wallace formulated the theory of evolution by natural selection
- ideas similar to darwin so similar they did joint presentation
- darwin published On the Origin of Species, detailing the theory of evolution by natural selection - very controversial and influential
