Evolution- part 3 (Unit 3) Flashcards
Darwins first belief on extinction and biodiversity
Extinction is gradual process
Is it gradual?
-Darwin didn’t recognize rare environmental events (bolide, volcano) that can have quick catastrophic events on population.
Part of extinction Darwin didn’t know of
Second Darwin point
Mass extinctions aren’t real but appear to exist due to gaps in fossil records.
Mass extinctions did occur and some played out over thousand of years.
Big 5 Extinctions
They are all very obvious in fossil records. If fossil sites from the period are known, a mass extinction’s effects on biodiversity will be impossible to miss.
Pre-extinction marine benthic ecosystem in latest Permian
Low abundance, high diversity. Dominated by brachiopods, corals, crinoids, and fususlind.
Microbe dominate ecosystem after EPME in early Griesbachian
Primary producers dominate. Post extinction
Opportunist-dominated ecosystem in Griesbachian Dienerian
High abundance, low diversity and dominated by disaster taxa. (Bivalve Claraia. Basically clams). Post extinction
Tracemaker dominated ecosystem in Spathian. Late Olenkian
Recovery of tracemakers. Dig underground. Post extinction
Mid Anisian benthic ecosystem.
Low abundance, high diversity. Dominated by brachiopods and crinoids. Late recovery period, refilled larger animal
Mid-late ansian ecosystem
Dominated by marine fishes and reptiles, marking rebuilding of top predator trophic structure. Late recovery period, refill larger animal niches
Mass extinction
Global in extent. Many kinds of species affected, various taxa occupying various habitats. Affects around 50%, but no agreed upon cutoff. Any more wont’ find disagreement it’s a mass extinction.
Do not account for most extinctions (only 4%)
Climate change, volcanic activity, impact
Background extinctions
More common loss of one or several species at a time. Slowly and steadly accumulate over huge period of time. Account for most losses.
Darwin 3rd rule
Extinctions result from biological cause.
competition between species not nonbiological catastrophes (volcanos, climate change)
Is this right? Sometimes. Extinctions have tied to biological and nonbiological causes, mass extinctions have been linked to nonbiological.
Darwin 4th rule
Extinction is both a part of and a consequence of natural selection.
Absolutely true. Individuals of a species survive to reproduce to pass on traits.
Extinct species have no individuals that could persist to leave offspring in face of natural selection.
2 sides of coin for darwins 4th rule
Natural selection improves fit between particular species and selection pressures that the habitat imposes. Species could benefit at the expense of one or other species.
Eventually the expense to other species would be their increasing rarity and extinction.
Evolution consequence will be most dramatic when organism gains access to underexploted resource.
Darwins finches
Ancestral species arrived in isolated chain, it was so dramatic darwin didn’t know all finches.
Finch species on Galapagos islands were so far away form mainland, it faced little competition.
Finches in south america were competing with other species for same resources.
