Lecture 20

Question 1

Cambrian Explosion (545MYA)

Answer 1

Burgess Shale: found triploblasic, shift in body form, oxygen levels optimum, break-up of land masses, genetic more sensory bits, increase in community living

Question 2

What caused the Permian-Triassic extinction?

Answer 2

Enormous volcanic activity created nuclear winter
Global warming, increase in global temp. from increase in carbon dioxide. Increased by release of methane hydrate locked in sea beds
90% of species were lost
BUT: reptiles saw increase in diversity –> terrestrial lizards

Question 3

Cretaceous-Tertiary extinction (65MYA)

Answer 3

volcanic activity --> climate change + meteorite 
End of dinos
70% of species died
Major loser: ammonites
Specialised species did badly

Question 4

“evil quartet”

Answer 4

1) Habitat loss/destruction
directly (deforestation, pollution)
indirectly (climate change)
2) Overkill
too many individuals taken to support the population
3) Invasive species
deliberately introduced 
inadvertently introduced
range changes due to climate change
4) Extinction cascades
one species goes extinct, others that depend on it likely follow