Chapter 23 Flashcards
Radiometric dating
Based on the decay of radioactive isotopes (parent isotopes decay to daughter isotopes at a characteristic rate.
Half life
Time required for 50% of the parent isotope to decay (not effected by temperature or pressure)
Geologic record
A standard time scale that divides earth history into 4 eons and further subdivisions
4 eons
- Hadean (origin of earth- 4.6 billion years ago)
- archaean (oldest fossils of prokaryotes)
- Proterozoic (endosymbiosis)
- Phanerozoic (Palaeozoic, Mesozoic, Cenozoic= Dino’s to humans)
Stromatolites
Layered rocks that form when certain prokaryotes bind thin films of sediment together
Plate tectonics
The container nets are part of great plates of earths crust that essentially float on the hot underlying portion of the mantle. Movements in the mantle cause plates to move.
How continental drift affects life on earth
- alters habitat
- climate change
- promotes allopatric speciation
- explains why some species are found on two different parts of earth
Mass extinctions
Large # of species become extinct worldwide
How many mass extinction have their been in last 500 million years?
What are two…
5
Permian extinction: separation of Palaeozoic and Mesozoic eras, 96% of marine animals died due to volcanic eruptions.
Cretaceous extinction: between Mesozoic and Cenozoic eras. 1/2 marine species died due to asteroid as well as dinosaurs.
Consequences of mass extinctions
- reduce ecological community
- takes millions of years to recover
- changing types of organisms left (more predators to prey)
Adaptive radiation
Periods of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles.
Ex: mammals were small and outcompeted until dinosaurs went extinct.
Heterochrony
An evolutionary change in the rate or timing of developmental events.
Ex: organisms shape depends in part on the relative growth of different body parts during development. Baby has Are proportions to body, but adult heads are smaller.
Paedomorphosis
Changes in the timing of the onset of reproduction. Retention of juvenile characteristics in the reproductively mature adult.
Ex: salamander can have both adult and juvenile characteristics but is still sexually mature
Homeotic genes
Regulatory genes that determine where features develop
Relative and absolute dating
Older sediments below
Radiometric dating
