W2: L9 = Palaeontology [ME Methods] (Prof. Benoit) Flashcards
How to characterise a ME? (2)
- Historically, a ME is a paleontological concept.
- Defined based on the fossil record of hard-shelled marine invertebrates & protozoans.
Methods to quantify extinctions attributes? (3)
- You need an idea of Time (vertically).
- You need a list of taxa (horizontal).
- Broken/Dashed lines are solid lines.
Methods to quantify extinctions? (6)
1) Number of genera or family in a given slice of time.
2) Number of extinctions in a given slice of time.
3) Extinction rate (ER).
4) Origination rate (OR).
5) Excess extinction rate (EER).
6) Survival rate (SR).
Step 1? (2)
= Count number of taxa/genera or family in a given slice of time.
- Usually 1-10 million years.
Problem with Step 1?
What if there are many taxa going extinct as there are new ones evolving?
Step 2? (3)
= Count number of extinctions in a given slice of time.
- Count the incomplete lines.
- The number of taxa that become extinct in a given slice of time.
Step 3?
= ER (in %).
ER (Extinction Rate)?
= number of extinctions over number of genera or families (in %).
ER attributes? (4)
- Less sensitive to speciation.
- More sensitive to the Lagerstatten effect.
- Low diversity.
- High extinction bias.
Lagerstatten effect?
=
Graph 2 showing families attributes? (2)
- Speciation & preservation.
- Complete turnover issue.
Step 4?
= Origination rate (OR) (or Speciation rate).
Origination rate (OR)?
= number of new taxa over total number of taxa (in %).
OR attributes? (2)
- Mass extinctions are immediately followed by an evolutionary radiation of new lineages.
- Lines going into other boxes/that continue.
Step 5?
= Excess Extinction Rate (EER).
EER?
= extinction rate compared to the background extinction rate (BER).
EER attributes? (2)
- Taxa go extinct all the time (even if it’s not an anthropogenic cause): for mammals, the species have a life-span of about 1-3myr.
- Extinction rate over BER (in %) will be average extinction rate.
Step 6?
= Survival Rate (SR).
SR?
= how many taxa survive over total number of taxa in the interval (in %).
SR attributes? (2)
- Mass extinction causes drop in survival rate.
- Lines that complete cross the full box/slice of time.
Step 1 equation?
No. of genera or family or taxa.
Step 2 equation?
No. of extinctions.
Step 3 equation?
ER = (# of extinctions / # of genera or family or taxa) x 100
Step 4 equation?
OR = (# of new taxa / # genera or family or taxa) x 100
Step 5 equation?
EER = ER - Average ER
Step 6 equation?
SR = (# complete cross lines / # genera or family or taxa) x 100