Fossils, Extiction and Speciation
- Created by: isabella newsum
- Created on: 23-11-14 16:43
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- Fossils, Extinction and Speciation
- Animals and Plants
- Fossils are the remains of organisms and provide the evidence that organisms lived ages ago
- Fossils form in rocks from 3 ways:
- 1) Gradual Replacement by minerals- teeth, shells, bones
- 2) Casts and Impressions- sometimes buried in a soft material, hardens round it and organism decays leaving a cast of itself
- 3) Preservation- in amber and tar pits where ther's no oxygen, moisture, so decay microbes can't survive
- How did life begin?
- Various hypotheses, but no-one
- Hypotheses can't be supported or disapproved- lack of valid and reliable evidence
- Fossils that formed millions of years ago have been destroyed by ecological activity
- Extinction
- Environmental Changes
- New predators
- New diseases
- Can't compete
- Catastrophic event
- New species develops
- Speciation
- The develop of a new speicies
- Occurs when populations of the same species becomes so different that they can no longer breed together
- Isolation
- Speciation
- The develop of a new speicies
- Occurs when populations of the same species becomes so different that they can no longer breed together
- Where populations of a species are separated
- Due to a physical barrier that geographically isolate some individuals from the main population
- Conditions on either side of the barrier will be slightly different, different characteristics will become more common- natural selection
- Due to a physical barrier that geographically isolate some individuals from the main population
- Speciation
- Natural Selection
- Each population shows variation- wide range of alleles
- Conditions on either side of the barrier will be slightly different, different characteristics will become more common- natural selection
- In each population, indibviduals with charcteristics make them better adapted- better chance of survival- breed successfully
- Alleles that control beneficial characteristics, more likely to be passed on
- Animals and Plants
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