Unit 6 Lecture 31 Flashcards
K-T boundary extinction may have been caused by what?
Asteroid Impact, which later cause an incineration of biosphere by shock wave of incandescent material. Causing a nuclear winter (debris injected into upper atmosphere circulated around the earth)
What was survival like in the first hours of the Cenozoic?
- For several hours the entire earth was bathed with intense infrared radiation
- fires were being ignited
- sheltering underground within natural cavities
- Smaller animals survived along with reptiles
What has caused mass extinctions in the past?
- alternating glacial and interglacial episodes
- global cooling
- drop in CO2
- rise in CO2
- global warming
- volcanism
- acidification of oceans
What happened during the recovery period after extinction? (End Devonian)
There was a change in body size distribution
- vertebrates experienced body-size reduction after the hangenberg extinction
What happened during the recovery period after extinction? (End Permian)
Reset of communities and more complex ecological interactions
What happened during the recovery period after extinction? (Triassic and K-Pg mass extinctions)
- rapid diversification of mammals after the extinction of dinosaurs
- rapid evolution of body size in mammals
- While dinosaurs were around mammal size was not big, but after the extinction, size increased
- therapsids filled in a lot of the body size range
To see if extinction selective, what 3 things would we look at?
- Taxonomic affiliation: clades share characteristics or morphology
- Ecological/life history traits: specialists vs. generalists, trophic level, etc.
- Emergent properties: widespread vs. restricted geographic range
How does geographic range correlate with origination rate?
Large geographic range size correlated with a lower origination rate (inverse relationship)
How does geographic range size impact extinction risk?
A small geographic range size increases extinction risk
Is there a general pattern with extinction rate and geographic range size?
Yes, extinction risk is correlated with geographic range size over the last 600ma
Selectivity is least/most pronounced at major extinction events which indicates a positive/negative association between geographic range and survivorship
Least
Positive
Geographic range size ______ with extinction intensity
decreases
Does body size predispose species to a higher extinction risk?
Body size does not confer to an increased extinction risk
When did size selectivity with mammal extinctions start happening (when did the body size of an animal impact extinction risk)?
When humans came around
What factors make a species more prone to extinction in the fossil record
a. Large body size
b. Narrow geographic range
c. Large population sizes
d. B and C
e. All of the above
b. Narrow geographic range
Why do humans have a reason to believe we are heading to our 6th mass extinction?
- Increasing carbon dioxide leads to warming temperatures
- Ocean acidification
- Habitat loss
Megafauna are defined as?
Mammals larger than 44 kg
Explain the megafaunal extinction
This extinction was unique mammalian history. It was extremely size biased, large bodied mammals were extinct and small bodied species survived.
What was lost during the megafaunal extinction?
13 extinct species
- bears
- wolves (dire wolves)
- cats
- bison
- pronghorn
- 7 species of horses
- llamas
- peccaries and tapirs
- mastodons and mammoths
- African elephants
- Giant rodents
- 3 species of giant ground sloth
- giant armadillos and pampatheres
Why were these species lost?
2 main Hypotheses:
1. human hunting: as humans traveled around the globe they hunted species to extinction
- they originated in Africa, went to Europe -> Asia -> North and South America and spread
2. climate change: extinction was a result of the climate change associated with glaciation
What is one of the major things that happened during the late Pleistocene?
Global climate change: glaciation cycle where polar ice caps expanded to their maximum about 18,000 years ago and then contracted/ The changes in climate associated with glaciation had major effects on the distributions of organisms
What happened as a result of the extinction in the late Pleistocene
- Body size distributions of species on all 4 continents
- Large bodied mammals were more like to go extinct
Things larger than what animal were at risk go going extinct?
Fox
What was the result for this size distribution?
Result was to fundamentally change the shape of the distributions where it happened.
What is pairwise comparisons
Body size distributions of Pleistocene mammals before extinction event
What orders are size biased?
Carnivores, Xenarthrans, artiodactyls, perissodactyls and depirotodonts
- Extinction was particularly interesting because it wasn’t a matter of removing large bodied clade i.e. in the carnivore clade the extinction was largely skewed towards larger body size
Pattern suggest that size selectivity was or was not due to shared ecological traits
was not
Name the order without size bias
Rodents and lagomorphs
- these tend to be small bodied and suffered very few extinctions
What was unique about the timing of the extinctions?
Approximately 12000 years ago in the new world and 46,000 years ago in Australia, the largest species in each fauna went extinct
it was consistent with the timing of human arrival
What continent(s) extinction rate had a coincidence with human arrival and climate change
North America and South America
What continent(s) extinction rate had a coincident with human arrival but not climate change
Australia
What continent(s) extinction rate had a coincident with climate change, humans were already there, but no real extinction
Africa
How many continents were consisted with the hunting hypothesis
How many continent were consistent with the climate
4
2
Very large mammals had unique constraints such as?
Life history slowed
- Low fecundity
- Low gestation
- Low population densities
Over the previous 66ma were large mammals vulnerable to extinction?
NO
What factor is correlated with extinction risk in fossil species?
Small geographic range size
Species that had hunting as at least one of their listings for being endangered were larger/smaller than those who did not?
larger
Explain overkill sites
During overkill, a predator invades the range of prey and constantly hunts it to extinction, but for climate change, the predator invades the range of the prey but does not hunt it to extinction. Instead climate change results in the extinction at a later time
The overkill model predicts that the relationship between kill sites and latitude will be?
Linear and positive
The uniqueness of the Pleistocene extinction implies that?
Increase extinction risk to large bodied species is a hallmark of human effects
Shifts in mean body size on each continent follow what dispersal patterns
hominin
