Flashcards in Exam 3 - Ch. 3 and 14 Deck (15):
*What is meant by the vary phrase “Cambrian Explosion”
"the period of animal evolution"; remarkable pulse of rapid evolution during the Cambrian
*What is Ediacaran fauna?
a group of animal species that existed between 575 and 535 million years ago; multicellular organisms that dominated the worlds oceans. some of them gave rise to living lineages of animals while others became extinct
*Why is the Burgess Shale fauna significant?
(a lagerstatten) preserved fossils from the Cambrian period
*What caused the Cambrian Explosion?
retreat of the glaciers and the rise of oxygen in the ocean
*What is an adaptive radiation?
occurs when 1 or few members of a small group of ancestral species rapidly diversifies in large numbers or descendant species occupy many niches
Adaptive radiation: dispersal to new location (often animals) --> reduce competition and increase resources --> adaptive radiation
*What triggers adaptive radiations?
ecological opportunity (increase O2 levels and predation - cambrian)
morphological innovation (jointed legs of cambrian arthropods)
*What is stasis and what are examples?
examples: fossil gingko, living gingko, horseshoe crabs, white tail deer
classic example: stromatolites
*What is the difference between stasis and gradualism?
stasis no change - gradualism gradual change
*Why does stasis occur?
no new niches to fill ??? dont really know
*What is the relationship between adaptive radiations and mass extinction?
Mass extinction --> reduce competition and increase resources and open niches --> adaptive radiation
*What are background extinctions?
extinctions that are not part of mass extinction events; though to be due to typical types and rates of environmental change or species interactions as opposed to the extraordinary environmental changes
*When did the big 5 mass extinctions occur?
The Ordovician Event: 443 mya
The Devonian Event: 359 mya
The Permian Event: 252 mya
The Triassic Event: 200 mya
The Cretaceous Event: 65 mya
*What is punctuated equilibrium?
a model of evolution that proposes that most species undergo relatively little change for most of their geologic history. these periods of stasis are punctuated by brief periods of rapid change, often associated with speciation events
what is the worst possible outcome of global warming
global cooling --> snowball earth