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3.2 Origins of biodiversity - Coggle Diagram
3.2 Origins of biodiversity
Extinctions
Background extinction rate
: the natural extinction rate of all species about one species per million species per year so between 10 and 100 species per year
general view of causes of mass extinctions
meteor impact
the result of climate change over a long period
volcanic eruption
The Holocene extinction
100,000 years ago - Stage 1: modern humans spread over the Earth
10,000 years ago - Stage 2: humans became farmers about 10,000 years ago when there were about one to ten million humans living on Earth
caused by the actions of humans and may be far greater in both extent and rate
Formation of species
Speciation
Definition: gradual change of a species over a long time. When populations of the same species become separated, they cannot interbreed and if the environments they inhabit change they may start to diverge and a new species forms
Humans can speed up this process by artificial selection and genetic engineering
may have geographical or reproductive causes
Natural selection
: 'survival of the fittest' where those more adapted to their environment have an advantage and reproduce but those less adapted do not survive to pass on their genes
Factors causing speciation
land bridges
continental drift
physical barriers
Plate tectonics
Continental drift
: the tectonic plates of the lithosphere drift around and move about 50 to 100 mm per year
movement of plate tectonics
slide past each other and create a fault line
diverge - creates a ridge and physically separates populations
converge
collide and forced upwards to create a mountain and creates a physical barrier
collide and the heavier plate sinks, creating a subduction zone where deep ocean trenches and volcanic island chains are formed, creating land bridges and new niches