5.1 Evidence for evolution Flashcards
Define evolution
EVOLUTION - cumulative change in allele frquency of a population’s gene pool over successive generations
Define fossil
FOSSIL - preserved remains or traces of an organism from distant past
Preserved remains (bones, teeth, shells) provide direct evidence
Traces (footprints, tooth marks) provide indirect evidence
The totality fo all fossils - fossil record - shows changes in organisms overt time
By what is the chronical sequence of fossils identified?
By the rock layer (straa) where that fossil was found: older deeper, newer closer to top => law of fossil succession - chronoligical sequence of complexity by which characteristics develop
Problems with fossils as evidence
Fossilisation requires distinct conditions - very few fossils - limited fossil data - difficult to determine evolutionary paths - missing links
What are transitional fossils
TRANSITIONAL FOSSILS - demostrate intermediary forms along the evolution path in a single genus
They establish the links between the ancestor and predicted descendants - example - archaeopteryx - links dinosaurs and birds
Define slective breeding
SELECTIVE BREEDING - from of artificial selection where humans intervene in the breeding of species to produce desired traits in offspring
What is comparative anatomy?
COMPARATIVE ANATOMY - a way to show that common features are similar suggesting common ancestry
Define homologous structures
HOMOLOGOUS STRUCTURES - anatomical features in organisms that are similar in basic structure but are used in different ways
Example - pentadactyl limb (five digit limb) - human/bird/reptile - different locomotion
Homologous structures suggest adaptive radiation
Expain adaptive radiation
ADAPTIVE RADIATION - new species rapidly diversify from ancestor where each new species is adapted to utilise a specific unoccupied niche in the environment/resources
Members evolve different morphological features (adaptations) in response to the different selection pressures
Example - Galapagos finches
Define speciation
SPECIATION - evolutionary process by which two related populations develop into different species - cannot interbreed and produce fertile offspring
Speciation happens in gradual divergence - two populations separated - genetic variation is random - natural selection will favour more adapted - the primary populations will gradually diverge
The degree of divergence increase the longer the populations are separated
Explain vestigial structures/organs
VESTIGIAL STRUCTURES/ORGANS - functionless structures/organs that once where in ancestors
Example - pelvic bone in whales, appendix
