Lec 08 Flashcards
(15 cards)
Mass Extinctions?
- Not always instantaneous
- Thousands-Millions of yrs.
- gradual collapse of ecosystems.
Indicators of Mass Extinctions? + Example?
- Carbon Cycle disruptions (CO2 fluctuations)
- Oxygen Depletion (Anoxia events, low O2, oceanic die off)
- sediment + fossil changes (leaves distinct geological markers)
ex. Permian-Triassic extinction (~252mya)
1. CO2 levels spiked - ocean acidification, global warming
2. >90% marine species died
3. >70% terrestial species died
5 Major Extinctions? Example of a ‘Key Winner’?
OS -
F/F -
PT -
TJ -
KPG -
Causes of Mass Extinctions?
- Sudden natural disasters
- climate shifts, volcanic activity + sea level changes
- loss of keystone species (eg. top predators, large herbivores)
Biodiversity Disruption?
Pre-extinction: stable, diverse species
Post-extinction: slow recovery, new species emerge + ecosystem change
Late Pleistocene - Holocene Megafaunal Extinction?
- 50kya, large vertebrates suffered major losses.
- major strong size biases in extinctions
- most occurred during final stages of Pleistocene + early-middle holocene.
-this event is unique b/c most extinctions DID NOT have strong size biases.
Herbivores?
11/57 species survived (1000kg)
eg. Rhinos, hippos, elephants
Megafauna Definition?
- Animals >42kg
- extinctions during 50kya-5kya
eg.
1. Australia: loss of diprotodon + large kangaroos
2. Eurasia: Extinction of Wooly Mammoths + cave bears
3. North + South America: Mastodens, Giant sloths, sabertooths.
Sized Based Extinctions?
- Larger species (>1000kg) most vulnerable
- smaller species had minimal losses
Reasoning:
1. Large animals need more food + homes
2. slower reproduction = population recovery struggles
Worst Extinctions:
- Australia + South America: Highest % Loss
- Africa had lowest extinction rates (maybe b/c of humans?)
Biomes?
- Tundra + grasslands lost the most large bodies
- Forests had lower rates
- Deserts lost fewer species
BUT all environments lost their large species
eg. Tropical Forests lost nearly all 1000kg species.
Why is the loss of large species bad?
It altered the shape of ecosystems permanently.
Ecosystem Reshaping?
- Pre-extinction:
- large fauna influenced plant diversity + community structure, dispersed seeds
- landscapes had more open areas + fruit bearing trees - Post-extinction:
- Fewer large grazers = forest change
- seed dispersal + nutrient cycling slows
- ecosystem dominated by small animals now - Plant-extinction:
- #’s up to 11x higher than in other intergalacial phases
- disappearance of the steppe biota was driven by extinction of plants that were specialists (generalists disappeared)
Megafaunal Loss Impacts?
- Pre-extinction: large animals spread fecal microbes + ectoparasites across distances
- Post-extinction: dispersal dropped to 15%
- In places like South America, pathogen spread became 70x slower, changing dynamics of microbes
- Loss of critical microbes led to increase # of pathogenic species (disease increase)
North America’s - Hall’s Cave (Climate Impacts)
- Climate driven habitat shifts
- impacts of climate + human activities
“ interplay b/t rapid environment change + anthropogenic factors” - Clovis culture + multi-causal loss of Mega Fauna
+ Younger Dryes Event???
Is there one solid reason for extinction?
no, it varies per region
