How many mass extinctions have there been?What are they and what caused them?What is the most recent one?
5Ordovician: climate change (cooling)Devonian: environmental changes/anoxia in ocean/sea level changes/plate tectonics Permian: global warming (ocean changes and anoxia)Triassic: volcanic eruptions/global warming/CO2 increase/ocean acidification -> wiped out nearly all of the dinosaursCretaceous: asteroid impact (Climate change?)Quaternary: mass extinction of Pleistocene megafauna
What are megafauna?
Animals with adult body weight >44kg
Describe the extinction vortex
Small population size due to some kind of eventLoss of genetic diversityDecreased fitnessIncreased mortality and decreased fecundityEven smaller population
Mass vs local extinctions
Mass:Large number of species/ecosystems involvedOften due to a catastrophic eventRelatively rapid in geological timeOften non-specificLocal:Often a single species/habitatOften due to a single event/issueRelatively rapid in geological timeOften targeted/specific
What causes species to become extinct?
Being unable to breed
Mass extinctions of Australian mammals
2 major events:PleistoceneLast 200 years
What happened in the Pleistocene?
Evolution of megafaunaArrival of humans on the continent
Why did megafauna evolve?
Response to decreased forest cover and increased savanna: radiation of grazing forms and greater size/bulk (poor food sources)
When was the megafauna extinction?How many species went extinct?Proposed reasons
46,000 YA>40 speciesClimate change? - Rapid onset of ice age- Temperatures dropped- Animals with these long generation times couldn't keep up- BUT extinctions happened at different times -> don't line up with ice ageHumans?- Direct hunting -> overkill, effects of fire- Would expect quick decline -> took over 10,000 years- Large body size: even low hunting rates can cause gradual decline if females and juveniles are killedMore evidence of overkill model: too gradual to be seen by people- megafauna extinctions around the world linked to human arrivals
Where are most animals going endangered/extinct now?What kinds of animals?
Arid regionsCreatures of critical weight range 35g-5.5kg (predation by cats, foxes)Terrestrial herbivores
Types of conservation
In situ:- In the environment to reduce effects on extinct/endangered species- Understanding population dynamics: size, diversity structure- Habitat restorationEx situ:- Conservation outside a species natural habitat i.e. in zoos, captive management and genetic management
Name 3 critically endangered Australian species
Leadbeater's possumOrange-bellied parrotSouthern Corroboree frog
Name 3 species critically endangered world wide
Cross river gorillaSumatran tigerPolar bear
Successes in de-extinction, genetic rescue, re-wilding
Panda: advances in ART and understanding of repro bioBlack footed ferret: ART and better understanding of repro/captive breedingRe-wilding of American Bison and Wolves
Tools for managing extinction
BREEDING!Cryo-bankingGenetic rescue: interbreed with genetically related speciesRewildingCloningCaptive breedingEnvironmental protection