B2.8 Speciation Flashcards
What does the fossil record show? (2)
-That new organisms ARISE, FLOURISH and over time, become EXTINCT.
-CHANGES
that lead to the formation of new species
Why can scientists not be certain
about how life began on Earth? (2)
- Lack of valid and reliable evidence
- Early life forms were SOFT-BODIED
Describe the traces left by deceased soft-bodied organisms (2)
- They leave few traces behind
- Most traces left were destroyed by geological activity
What is a fossil?
The REMAINS OF ORGANISMS from many years ago, found in rocks
Give four ways that fossils are formed
- HARD PARTS of organisms that don’t decay easily
- From parts that haven’t decayed because 1 or more conditions for decay are ABSENT
- Preserved traces (footprints, burrows)
- When decayed parts are replaced with NEW MATERIALS
What can we learn from fossils?
How much/how little different organisms have CHANGED as life developed
Give up to 6 causes of extinction
- New/more successful PREDATOR
- New COMPETITION
- New DISEASE
- A single CATASTROPHIC event (volcano/asteroid)
- The cyclic nature of SPECIATION
- ENVIRONMENTAL CHANGE over geological time
What causes a new species to arise?
-Isolation; two populations of a species become separated (e.g. geographically)
What is ‘genetic variation’?
When each population has a WIDE RANGE OF ALLELES that control their characteristics
What happens in ‘natural selection’?
In each population, the alleles that control the characteristics are selected which are BEST SUITED help the organism to survive
What is ‘speciation’?
When the two populations become so different that they cannot successfully interbreed (to produce viable offspring)
