8.1-8.2: Developing a Theory for Evolution
- many individuals challenged prevailing religous philosophical beliefs
| Buffon | common ancestry with apesEarth is older than 6000 years |
|---|---|
| Malthus | populations produce more offspring than the environment can supportfight over resources |
| cuvier | paleontologistsuggested catastrophism (different layers in fossil strata were caused by natural disasters) |
| mary anning | discovered the first plesiosaur-link between aquatic and land species |
| Lyell | challenged catastrophism suggested uniformitarianismgradual changes lead to substantial changes over time |
| Lamarck | inheritance of acquired characteristics, unnecessary body parts will disappear |
| Darwin and Wallace | gradualism and theory of evolution by natural selectionorganisms produce more offspring than are able to survivevariation in populations is heritableindividuals with better adaptations produce more offspringprocesses are slow and gradual |
Sources of Evidence for Evolution
- fossils=traces of remains of past life found in sedimentary rock
- biogeography=the study of past and present geographical distributions of species populations
- anatomy=comparing structures within and between species
- embryology=the study of early, pre-birth stages of an organisms development
- DNA evidence= similarities in organisms genetic sequences suggests a common ancestor
fossil record =containts the remains and traces of past life buried within sedimentary rock
- reveals the history of Earth and kinds or organisms alive in the past
Evidence from Fossils
- the law of superposition
- each rock layer is older than the one above it
- transitional fossils
- show intermediary links between groups of organisms
- common characteristics of two now separate groups
- vestigial structures
- a structure that is a reduced version of a structure that was functional in the organisms ancestor
Evidence from Biogeography
- study of past and present geographical distribution of species populations
- used by Darwin and Wallace
- species evolve in one location then spread to other regions
- geographically close environments are populated by related species
- environmentally similar but geographically separated locations do not guarantee related species
- closely related species are almost never found in exactly the same location or habitat
- super continent separated, spreading organisms over different places
Evidence from Anatomy
- homologous structures=similar structures, different function
- analogous structures = structures that do not have a common origin, similar function
Evidence from Embryology
- study of early pre birth stages of an organisms development
- shared ancestry
Evidence from DNA
- similar DNA sequences