14. The Geography of Evolution Flashcards
What is the disparity between Darwin’s model of evolution and what is seen in the fossil record?
Darwin’s model describes very gradual change, the fossil record shows ‘statis’ with sudden jumps
How did Darwin explain the sudden jumps of evolution in the fossil record?
He explained them as being missing, aka the specimens in between existed but the fossils were missing.
What is a proposed alternative to Darwin’s theory of intermediate fossils simply being missing? Who proposed this?
Punctuated equilibrium (statis with sudden evolutionary ‘jumps’)
- Eldredge and Gould
Define Phyletic Gradualism.
- Speciation occurs gradually and statis is just perceived not real and transitional links may one day be found.
- An ancestral species may transform completely into a new one
Define Punctuated Equilibrium.
Speciation occurs rapidly and then a species undergoes stasis, transitional links may not exist
- A sub-group of an ancestral species becomes a new one
What is a possible reason for rapid speciation as described by Punctuated equilibrium?
A chance dispersal event may geographically isolate a species causing genetic drift and local adaptation, then reproductive isolation leads to a new species
How do the idea of poor depositional environments feature in the process of rapid speciation?
If the geographically isolated subset of a species is in a poor/small depositional environment (such as a mountain side) there may be no record of the species while it is developing - only when it takes over a more depositional environment.
What can happen when an adapted species comes back into contact with the original population?
Competition, habitat alteration, predation, spread of diseases/parasites - this can lead to extinction, replacement, and turnover
What are some possible scenarios for a population becoming separated from the rest of the species?
Tectonic activity (spreading continents/mountain uplift), environmental changes (new rivers/lakes), islands etc
Where are the highest rates of evolution/speciation seen now?
Remote oceanic islands, mountain tops, some lakes
What is a sedimentary basin?
Regions of earth’s crust dominated by subsidence, providing deopcentres for sediment to accumulate
What sort of regions have the thickest sediment deposition?
Lagoons, just-offshore, lakes, basins
How do strong depositional regions compare with strong evolutionary regions? Why is this significant?
Mostly opposite, poor deposition on islands, mountain tops - volcanic islands often don’t last long
- ,Environments prime for deposition are bad for evolution.
What is found when sediments do survive from strong evolutionary regions such as mountain tops?
Fossils of many new specimens.
What happened to diversity and speciation rates after the KT boundary?
Why is this significant?
Massive explosion of diversity compared to pre extinction
- Nothing is environmentally changing in these periods – just the existence, or lack of other species.
- Shows that a region with little diversity is likely to see new species
