Evidence for evolution, lecture 2 Flashcards
Categories of evidence for evolution
7
- direct experiment
- biogeography
- fossil record
- homology, vestigial structures and homoplasy
- embryology
- comparative behaviour and biochemistry
- hierarchical organisation of life
Example for direct evidence from experiments for evolution
Guppies, fish that breed quickly 1 generation per month live in pools and streams Native to South America intense male competition for females
Guppies
competition between males for females
females prefer to mate with males which have more brightly coloured spots
Guppies are an example of
direct evidence for evolutionary change over a short timescale
Biogeography
Living organisms aren’t as widely distributed as their potential habitats
Why aren’t living organisms aren’t as widely distributed as their potential habitats?
(Biogeography)
continental drift
such as Pangaea
Example of similar organisms found on different continents
Ratites, 3 way continental split
- Rheas, South America
- Emus, Australasia
- Ostriches, Africa
Oceanic islands
Few species, many endemic but resemble mainland species
evolved in isolation
Example of oceanic island
NZ
split before mammals evolved
only native mammals are bats and marine mammals: cetaceans and seals
Pangaea
250 MYA to Modern Earth
Convergent evolution
independent evolution of traits similar to species in separate places
How are island species separated?
land masses which were joined by bridges,
bridges disappeared and the continents were cut off
Example of separated islands
Madagascar,
endemic lemur, 99 species
Alternative to isolation of species by separation of land masses?
island species migrated there then became isolated
The fossil record
A direct but fragmentary record of evolution
The fossil record represents organisms which had and live in…
which had hard parts
and it is more common in past aquatic environments
Process of fossilisation
- animal/plant dies - soft bits rot away
- sediment settles, covers bones, solidifies over time
- groundwater dissolves the bone, leaving a cavity/mould
- minerals deposited in the mould form a cast
- erosion/land movement reveals the fossil millions of years later
How can a time to be given to fossils?
layers of a known age that the fossils are found in, indicate timeframe of fossils
Burgess Shale faunas
Canada,
ocean life, 525 - 525 MYA
high degree of preservation
able to construct images
Homologous characteristic
Similar structures aquired from a common ancestor
Vestigial structures
Parts of organism which are inherited from an ancestor but have no apparent function currently, poorly developed in some organisms but functional in some
Examples of vestigial structures
arm hair on humans
hair, chimpanzees
Homoplastic characters (analogous characters)
Characters which are similar in appearance and function but have separate evolutionary origins
Embryology
comparison of vertebrate embryos,
similar when developing but different organisms when formed
Comparative (social) behaviour
The more similar the behaviour, the more closed related organisms may be
Biochemistry - the molecular record
5
- DNA contains a record of evolutionary change
- mutations change genes
- evolution results from continuous changes in genetic composition
- closely related organisms have fewer genetic differences
- less closely related organisms have more genetic differences
Phylogenetic tree
A diagram which displays the lines of evolutionary descent of different species, organisms or genes from a common ancestor
Hierachical organisation of life
7
- kingdom
- phylum
- class
- order
- family
- genus
- species
