evolution lecture 7 Flashcards
what are fossils?
preserved remnants or traces or past life
what tyopoe of rock are most fossils found in?
sedimentary rock
what are index fossils?
common, widespread fossil characteristic of particular period of earth’s history
what is the geological record?
- earth is about 4.6 billion years old
- microbial life arose relatively early
- fossils of animals and plants common in the last 550 million years
phanerozotic eon
phanerozoic eon divided into______
3 eras
each era subdivided into PERIODS
what are periods?
divisions of an era
order of the eras
oldest to newest
cenozoic –> mesozoic –> paleozioc
what is a mass extinction
when many species go extinct in short period of time
causes of mass extinction?
larhe environmental changes
the 5 big extinctions mark mostly what
most mark the ends of eras
End- Permian mass extinction
about 250 million years ago
- biggest mass extinction
- extinction of about 90% of species on earth
- many large taxa went completely extinct
End-Cretaceous
- 65 million years ago
- most recent big mass extinction
- extinction of 50% species on earth
ex: dinosaurs
adaptive radiations
- rapid speciation and evolutionary change in underexploited (not used to full potential) habitats
when does adaptie radiations happen?
after mass extinction
only surviving lineages can radiate
