Mass extinctions and fossil record Flashcards
How many mass extinctions have occurred ?
5 over 4.5 billion years
Define mass execution
An event which leads to killing off a very large number of species
List 3 species of organisms which are in danger of becoming extinct ?
White Rhino
Siberian tigers
Polar Bears
3 effects of man and how we are causing mass extinctions ?
Pollution - Cars , industry
Deforestation - and habitat destruction
Climate change - man made effects which calculate to an increase in global mean temperature
What two ways are humans affecting African Rhino population
Poaching
Habitat loss
Methods used to increase population of rhinos ?
Legislation and policing
Conservation areas
Captive breading
Why is there no official record of the origins of life on Earth ?
The original cells from which all life evolved where to small to have left fossils
How long ago did life on Earth begin ?
4.5 billion years ago
What are fossils ?
They are impressions left in rock ( sedimentary ) of living tissue. Non of the tissue remains
How are fossils formed ?
An organism dies and its body is trapped in still , tar , permafrost
It slows down decomposition and leave fossils behind
Describe 2 reasons why the fossils record is incomplete ?
Very early organisms were unicellular or very simple ( so they didn’t leave fossils
Fossils are relatively rare because they only from under perfect conditions
What info can we gain from the fossil record ?
Enables us to work out when organisms arose
How species are related to other species
differences in intended structures
What evidence is there to suggest what cause the extinction of the dinosaurs ?
A layer of burnt soil all around the world
There are no dinosaur fossils above the burnt layer
Crater off the gulf of Mexico
