9 Flashcards
How new species arise?
A barrier that prevents gene flow
allopatric speciation?
When the ancestral population is physically divided into two populations by a geographic barrier.
Peripatric speciation?
When a small subset of individuals are separated from the main population by a geographic barrier and isolated to a new location (founder).
Parapatric speciation?
Occurs when species are spread out over a large geographic area, but mate only with those that live close to them.
Sympatric speciation?
Occurs within a population when a small subset exploit a new niche and mate only with others within that niche.
Speciation events that use geographic barriers?
Allopatric and Peripatric
Originations?
Origins of species that result from speciation events
Background rate?
Ordinary extinction with a variety of causes: changing climate, loss of food recourse, predation, disease, competition, loss of habitat, etc
Sepkoski’s curve?
*X axis: time
*Y axis: number of marine invertebrate families
Standing diversity (starting diversity) T2?
Standing diversity T1 + originations T1 - extinctions T1
How to compute standing diversity of current stage?
*Count the standing diversity at the beginning of the previous stage
*Count the number of originations during the previous stage
*Count the number of extinctions during the previous stage
The permian mass extinction occurred how many years ago?
250Mya
In the permian mass extinction, how many species were lost?
96% of species
The Cretaceous Paleogene extinction occurred how long ago?
65Mya
How many species were lost in the Cretaceous Paleogene extinction?
75% of species, which killed all non-avian dinosaurs
Why was the permian extinction important?
It nearly wiped out all life.
In what extinction did he trilobites go extinct?
Permian extinction
What caused the permian extinction?
Largest volcanic eruption ever in Siberia.
What marked the end of the mesozoic?
The Cretaceous Paleogene extinction.
Adaptive radiation?
Rapid diversification into many forms over a short period of time.
Key innovations?
Evolutions of novel traits and phenotypes that drive adaptive radiations.
Tempo in evolution?
The timing or rate in which evolution occurs.
Mode in evolution?
How evolution occurs
Evolution is a change in ________ within a population over time.
Allele frequencies
Time by morphology plots?
*Y axis: Time from old to young. Start of the line is the origination and end is extinction.
*X axis: change in morphology
Angiogenesis?
gradual change overtime within a single lineage.
Cladogenesis?
Subpopulation diverged and developed new traits.
Anagenesis?
Gradual evolution within a single lineage. It is driven by continuous directional selection.
Stasis?
Long periods where most species do not change much, and then rapid busts of evolutionary change.
What is one explanation to why there are gaps of no transitional evolution and then sudden change?
Stasis
Did paleontologists prior to 1970’s believe the idea of stasis?
No, they believed that there was an incompleteness in the fossil record which lost the transitional evolution fossils.
Punctuated equilibrium? 3*
Morphological change occurs relatively rapidly associated with splitting of lineages.
Gaps are not just due to an incompleteness in the fossil record with a lot of missing transitional fossils that will show anagenesis.
Stasis is common
Phyletic gradualism?
Anagenesis causes species to evolve continuously and gradually over time. The gaps in the fossil record are due to an incomplete fossil record.
Possible causes for stasis? 2*
*Fluctuating selection, perhaps tracking a changing environment?
*Constants? Limits or biases in the production of variation due to morphology or genetics.
How does evolution actually proceed?
*Over short evolutionary time, gradualism and anagenesis are common. Adaptive radiations occasionally occur over short evolutionary time. The fossil record holds some examples of gradualism over longer evolutionary time.
Why is the Anthropocene important?
When human hunter gatherers transition to civilization and agriculture. It had a significant important to the planet and could be the start of the 6th mass extinction.
