Life on Earth Revision

1. Life on Earth Revision

2. Variation of Life on Earth • All living things, both those alive and those that are now extinct all originate from the simple living things that first appeared 3500 million years ago. • Evidence for evolution comes from: • Fossils • DNA testing

3. Natural Selection • Natural selection involves: Variation Competition Increased chance of survival Reproduction Increases numbers in population

4. Selective Breeding • Selective Breeding involves: Selecting individuals with desired features Breeding them Selecting offspring with desired features Breeding them Increasing numbers with desired features

5. Multi-cellular Organsism • Evolution of multi-cellular organisms has lead to; • The development of receptor and effector cells. • These are linked by neurones. • The neurones link via the CNS (See Brain and Mind)

6. Theories of Evolution • Lamark – suggested organisms developed through an inner urge to improve. • Cuvier – suggested the fossils in layers of rock were due to God wiping old species out with catastrophes , e.g. Noah’s Ark. • Darwin – suggested evolution occurred by a process of natural selection or survival of the fittest.

7. Darwin’s Theory • Was rejected at first for religious reasons as the Bible was taken literally at the time. • Was eventually accepted because it explained how evolution occurred.

8. Data and Theories • Understand the difference between data and theories. • Appreciate that data could be explained by a number of theories. • Appreciate that theories require original thought. • Understand why theories are accepted or rejected.

9. Key Terms with Theories • Understand the terms • Corroborate; make more certain • Confirm; strengthen, verify. • Falsify; forge, misrepresent. • Prove; to establish as truth

10. Causes of Variation • Random changes in the DNA called mutations occur. • If in sex cells these are passed on to the offspring. • Sometimes these changes gives increased chances of survival. • The frequency of the mutation then starts to increase. • This can eventually lead to new species.

11. Evolution • Random Mutation. • Random Breeding. • Natural Selection.

12. Human Evolution • Humans species have evolved from a common ancestor. • All other hominids have become extinct. • The evolution of intelligence is very important to the evolution of humans. • The ability to learn from experience has given humans a selection advantage.

13. Under Pressure • Organisms are dependent on the environment and other species. • Organisms compete. • Large changes in the environment can result in extinction of a species. • Extinction of one species can then affect other species in the food web.

14. Under Pressure (cont.) • Changes that can affect an organism include; • Major change in conditions • A new species that is a competitor, predator or disease. • Another organism in the food web becomes extinct. • Many species have become extinct, sometimes mass extinctions occur e.g. dinosaurs.

15. Biodiversity • There is evidence of an increasing rate of extinctions. • Retaining biodiversity may be important for food and medicines. • A species has less chance of becoming extinct in an ecosystem that is diverse. • Maintaining diversity is an important part of using the environment in a sustainable way.

16. Origins of Life • The first living things developed from molecules that could copy themselves (DNA). • These molecules were produced by the unique conditions at the time. • If conditions had been different, natural selection could have produced different results. • Although there is no proof of life elsewhere, there are so many galaxies, stars and planets that some scientists think life elsewhere in the Universe is likely.