Old and New Species
- Created by: boy_repellent
- Created on: 10-04-14 19:37
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- Old and New Species
- Origins of life on Earth
- the earth is about 4500 million years old and life began about 3500 million years ago
- fossils may be formed in various ways:
- from hard parts of animals that don't decay easily (bones, teeth, shells, claws etc)
- from parts of organisms that have not decayed because some of the conditions for decay are absent
- when parts of the organism are replaced by other materials, such as minerals, as they decay
- as preserved traces of organisms (footprints, burrows etc)
- most organisms that died did not leave a fossil because the conditions for fossil formation were absent
- many early life forms had soft bodies so few traces were left
- some traces that were left behind could of been destroyed by geological activity (earthquakes)
- Fossil evidence
- extinction means that a species which once existed has completely died out, it can be caused by:
- a new disease killing all members of a species
- the environment changing
- a geological event may occur and destroy a habitat (volcanic eruption)
- climate change
- following a collision of giant asteroid and Earth
- a new predator may evolve and kill/eat all of a species
- a new competitor may evolve, the original species may be left with little to eat
- natural changes in species occur over time
- extinction means that a species which once existed has completely died out, it can be caused by:
- Isolation and Evolution of New Species
- New species can arise from existing species if a group becomes isolated from the rest
- Geographical isolation could occur if an island separates from the mainland etc
- organisms left on the island may be exposed to different environmental conditions, food availability or predators
- Natrual selection will occur in both areas
- Origins of life on Earth
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