Zusammenfassung der Ressource
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