12. Outliving T-rex Flashcards
Which extinction killed the dinosaurs?
End-Cretaceous
What letter is sometimes used to represent the Cretaceous period to avoid confusion with the Carboniferous?
K
When was the end cretaceous mass extinction?
65 Million Years ago
What % of overall species went extinct in the end-cretaceous mass extinction?
75-80%
What are the 2 main theories for the cause of the end-cretaceous extinction?
Bolide impact or eruption of the Deccan Traps in India
What is a bolide?
A meteorite large enough to form an impact crater
What evidence of environmental conditions was found in cretaceous-tertiary boundary clays? What do they evidence? What is the significance of their location?
Iridium, soot, charcoal, tektites
- Evidence of major environmental disruption e.g. wildfires
Found everywhere -> worldwide event
What was the impact of the end-cretaceous extinction on land tetrapods?
All LARGE tetrapods on land died
What was the impact of the end-cretaceous extinction on freshwater animals ?
Most large ones survived
How large was the end-cretaceous bolide speculated to be?
10-12km diameter
What was the quick impact of the bolide?
Nearby - incineration
Far away - wildfires and tsunamis
What was the main long lasting effect of the bolide impact that affected everywhere?
Blackout
What is the impact of a blackout on the world/ecosystems?
- Cold weather
- Photosynthesis shutting down
- Green food chain collapses
- Prevents unsprouted seeds from germinating
What were the most vulnerable land groups in the end-cretaceous extinction?
Vegetable eaters, eaters of vegetable eaters, those requiring lots of food regularly (warmbloods)
What were the least vulnerable land groups in the end-cretaceous extinction?
Detritus eaters, eaters of detritus eaters, diggers for roots, tubers and seeds, those able to fast for long periods (coldbloods)
Why were freshwater systems more durable than land systems in the end-cretaceous extinction?
Freshwater systems are fuelled by both green and brown food chains and are able to survive when the green systems shut down.
- Systems are damaged but not driven to full extinction
Who were the best survivors of the end-cretaceous extinction?
Small seed and invertebrate eaters, especially those plugged into brown food chain, and big freshwater predators at the top of a brown food chain.
What are four main characteristics to increase survival through a mass extinction?
- Large geographic range
- High abundance
- Habitat and food generalism
- Low resource requirements
What traits of cold-blooded animal populations are conducive to their good survival rates?
- Large numbers in favourable areas, which persist under harsh conditions
- Population needs less food than warm-blooded counterparts
- Small numbers even in unfavourable conditions (occupy a range of habitats)
- Can resupply between these regions to grow numbers after reduction
What traits of warm-blooded animal populations make them less likely to survive extinction-type events?
- Need more food
- No breeding populations in unfavourable locations
- Smaller populations typically, in even favourable locations
- More vulnerable to local extinctions when conditions turn unfavourable
- No resupply
What does the study of crocodiles over the last 50 ish years prove about coldbloods?
Crocodiles are very threatened by poaching and thus were predicted to have gone extinct 30 years ago, but still persist today
- Show resilience of cold blooded river animals
What was studied to try and pinpoint a time of year for the beginning of the end-cretaceous extinction? What time does it suggest
Fish bones
- Annual growth lines in specific bones, these have peaks in the summer and show a cut off just before that
Suggests spring extinction
What other research corroborates the findings from the fish-bones?
Carbon isotope records that show growth patterns
Why is it so hard to compare severity of extinctions? (2 reasons)
Due to disparity in fossil records between periods
- Extinction usually described in terms of species, while fossils usually categorised by genus
