Speciation Flashcards
What are fossils?
The ‘remains’ of organisms from many years ago
Where are fossils found?
In rocks
Which 4 ways can fossils be formed?
1) from the hard parts of animals that do not easily decay
2) because parts of organisms that have not decayed due to a condition needed to decay
3) when parts of the organism are replaced with other materials as they decay
4) as preserved traces of organisms, e.g. footprints, burrows and rootlet traces
Why did many early forms of life leave few traces?
As they were soft-bodied
Why may have early life form traces been destroyed?
By geological activity
What can we learn from fossils?
How much or little organisms have changed as life developed on earth
Which 6 ways can extinction be caused by?
1) environment changes over geological times
2) new predators
3) new diseases
4) new, more successful, competitors
5) a single catastrophic event (massive volcanic eruption)
6) cyclical nature of speciation
How can new species arise from isolation?
Two populations of species becoming separated
How can new species arise from genetic variation?
Each population has a wide range of alleles that control their characteristics
How can new species arise from natural selection?
In each population, the allele that control the characterises which help an organism to survive are selected
How can new species arise from speciation?
The populations become so different that interbreeding is no longer possible
Where does evidence for early forms come from?
Fossils
