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2690126
Fossils, Extinction and Speciation
Description
Biology GCSE Unit 2 Fossils, Extinction and Variation
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fossils
extinction
speciation
biology
gcse
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jroach8989
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Resource summary
Fossils, Extinction and Speciation
Fossils
Remains of plants and aniamals
From million of years ago
Found in rocks
How they're formed
Gradual replacement by minerals
Teeth, shell, bone decay slowly
Replaced by minerals as they decay
Rock-like substance formed
Shaped like original part
Surrounding sediments turn to rock
Fossils remain distinct
Casts and Impressions
Organism buried in soft material
Clay hardens around organism
Organism decays
Cast created
Include burrows and roots
Footprints can also leave impressions
Preservation
In amber and tar pits
No O2 or H20
Decay microbes can't survive
Glaciers are too cold
Peat bogs are too acidic
Speciation
Development of a new species
When populations become too different
Can't breed to produce fetile offspring
Isolation
Physically divides a population
eg. floods, earthquakes
Conditions either side of divide different
Natural selection occurs
Different characteristics for each population
Eventually two populations change too much
So can't produce fertile offspring
Become two separate species
Population shows variation - Wide range of alleles
Individuals in each population have better characteristics to survive
Better adapted individuals more likely to successfully breed
Alleles controlling beneficial characteristics passed on to offspring
Eventually beneficially characteristic are passed on to an entire new generation
Extinction
Organisms can't evolve quickly enough
Sudden environmental change
New predator
Humans
New disease
Can't compete with new species
Natural Diaster
Volcanic eruption
Collision with asteroid
New species develops
Speciation
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