Lecture 16: Mass Extinction Flashcards
What is competitive exclusion?
When a species goes extinct by a closely related species
What is obligate symbiosis?
Species can go extinction if another species they depend on declines or goes extinct
What traits make a species vulnerable to extinction?
Poor disperser
Top of a food chain
Restricted to a small geographic range
Small population
Specialized requirements (food, temperature, water salinity…)
Large body size at maturity (long lifespan, low reproductive rate)
What are examples of abiotic factors that lead to extinction?
Temperature or climate fluctuations
Extreme sea level changes
Volcanism
Asteroid impact
How is the background rate of extinction determined?
Examining extinctions throughout the fossil record: how many species have gone extinct over the evolutionary history of a single family
What are limitations to using fossils as evidence of background rate of extinction?
Fossil record does not accurately represent past species diversity (not all animals and environments allow for fossils)
Why do we use families instead of species for mapping out extinctions?
Two families have greater morphological differences between them than between two species or two genera (easier to tell them apart)
What is a mass extinction?
Extinction of a large number of unrelated species (biodiversity loss) over a short period of geological time
Similarities vs difference of mass and background extinctions.
Similarities: can have multiple causes and change evolutionary history
Differences: different outcomes (mass means entire communities are removed and fundamental/unpredictable changes in large scale trends occur)
What are the causes of mass extinctions?
Extreme normal earth processes (intense volcanism, glaciation, earthquakes)
Catastrophic extraordinary events (supernova blast, asteroid impact)
How did the end ordovician extinction occur?
Increased volcanic activities and sediments in ocean meant less carbon in the atmosphere and cooler temps.
How did the late Devonian extinction occur?
more plants lead to global cooling and anoxic ocean environments –> roots increased weathering which caused less atmospheric carbon and algal blooms.
How did the end permian extinction occur?
series of massive volcanic eruptions caused global warming and anoxic environments
How did the end triassic extinction occur?
gradual climate change, asteroid impact and volcanic eruption –> open niches allowed dinos to spread
How did the end Cretaceous (KT) extinction occur?
asteroid impact caused dust cloud in the atmosphere, causing clobal winter and blocking sunlight (killed many plants and the dinosaurs)
What is the evidence for the asteroid in the KT extinction?
180 km wide crater dated to End Cretaceous
Shocked quartz found near there which can only be caused by an intense blast
What are siberian traps?
a large region of volcanic rock that show proof of volcanic activity
What is recovery like after a mass extinction?
If there is a gap in the environment a species can fill, something will evolve to fill that gap.
