Unit 3 - AOS 1 - CH 2 - Biodiversity changes overtime Flashcards
Fossils definition
“When under the right conditions hard body parts or traces of an organisms (footprint, impressions on tree bark) become mineralised and turn into a fossil.
Strata
layers of sedimentary rock
Relative dating
Type of method to date rocks
“looks at rocks above and below, and is based on the fact that the layers of lower strata were typically formed before the rocks in the upper strata.”
Absolute dating
They provide an estimate of actual date the fossil was formed relying on the info of radioactivity.
- Changes from parent to daughter isotope
- Carbon dated fossils -> measure unstable isotope carbon 14 (6 protons and 8 neutrons) which decays to nitrogen 14 (7 protons and 7 neutrons.)
-» due to decay being at a stable rate: the amount of carbon 14 left in specimen tells us how long ago it.
Name the 6 mass extinctions
- Ordovician -> Silurian
- Late Devonian
- Permian -> Triassic
- Triassic -> Jurassic
- Cretaceous -> Tertiary
- Holecene
Define mass extinction.
“A widespread and rapid decline in the diversity and abundance of species on earth”
Ordovician -> Silurian extinction
Occurred by: Gondwana (large land mass) moving to a position over the south pole.
Organisms: trilobites, reef building invertebrates and jawless fish and all unicellular plants other than algae.
- global cooling: large ice sheets and sea levels
- CO2 was ^ in sequestration = cooling.
Late Devonion extinction
Occurred by: not clear
Organisms: 1st ferns and insects, some fish evolved limbs = first land vertebrates.
- Affected life in shallow and tropical seas -> decreased O2
Permian - triassic extinction
Occurred by: not clear
organisms: reptiles and amphibians, ancestors of mammals and dinosaurs.
- Pangea rest large ocean
- Largest extinction 95%
Triassic - Jurassic extinction
Occurred by: volcanic activity associated with seafloor spreading and breaking up of Pangea, but other causes have been suggested.
Organisms: first mammals and dinosaurs were appearing
Cretaceous - tertiary extinctions
Occurred by: impact of large asteroid
organisms: event that killed off dinosaurs and other organisms.
- change in climate due to volcanic activity and falling sea level was already occurring.
Holecene (6th mass extinction)
Occurred by: Human activity -> alteration of habitat and impact on climate change
organisms: one whole class of vertebrates under threat.
- occurring 100-1000 times faster
Species endemism
“Animals and plants that are native to one single geographical location”
Biodiversity hotspot
“Areas that have a high representation of diversity with many locally endemic species”
Rapid species diversification definition
“A process where a group of organisms undergoes a significant increase in the variety of species of forms in a species, over a relatively short period of time”.
Rapid species diversification in terms of after a mass extinction
Opening of new ecological niches or availability of untapped resources, can lead to rapid diversification as species adapt to exploit evolution.
Environmental variations definition + examples
” Changes to environment over long, medium and short term scales”
SHORT: bushfire, volcanic eruption
MEDIUM: El Nino
LONG: Continental drift
El Nino
Southern oscillation (ENSO)
- Last 3-8yrs cycle
- See-sawing change in sea surface temps and avg atmospheric pressure in & above Pacific Ocean
During events:
1. more than avg. temp -eastern pacific
2. less than usual pressure - central pacific
3.1 yrs long droughts aus (S&E)
Continental drift
Plate tectonic move earths continental plates
- each plate = 100km thick and move 1-12cm per yr
- Endemic species due to populations being isolated.
