Evolution

Evolution:

Organisms produce more offspring then the environment can support. Most will die before reaching adulthood because of the simple fact being there aren't enough resources for them all.

Offspring will show variation in their characteristics but some variations will be better adapted to the environment then others. Limited resources will cause competition between individuals. Those who are better suited to the environment are more likely to survive while others will die. This is called 'Survival of the Fittest' or Natural Selection. They'll pass on their variations to their offspring.

Evolution means a gradual change over time. Charles Darwin (1809-1882) drew together several ideas to produce a theory. 
He knew there was competition between individuals. Darwin realised that if the environment changed different variations may be better suited to the new conditions. So the range of variation in characteristics of the population will gradually change over generations, called evolution.
If the environment changes too quickly and organisms don't have adaptations to help them survive, they'll die out and their species may become extinct.


A problem for Darwin's theory was that there was little evidence for it as Evolution takes time to observe.

Warfarin is a chemical that was used to poison rats. When it was first used most rats that ate it died. Within 10 years rats were resistant to warfarin.
Because of Variation there were always some rats that were resistant but no one realised this. So when the poison killed the non-resistant rats the only ones left to breed were resistant.


Speciation is a formation of new species, such as when populations of a species are separated geographically and evolve until they are no longer capable of interbreeding.



Key Words:

Competition
Survival of the Fittest
Natural Selection
Evolution
Extinct
Resistant
Speciation


Questions:

1. Why is there competition between individuals?
2. What is meant by 'Survival of the Fittest'?
3. How can a species become extinct?
4. How did rats become resistant to warfarin?
5. Ground finches have large, powerful beaks to crush seeds. A closely related species has a narrow beak for probing in small holes for insect larvae. Suggest
how this species could've evolved from the seed-eating species.


What you should've learnt:

An understanding of Darwin's theory by Natural Selection including a. Variation  b. over-production  c. Struggle for existence  d. Survival  e. advantageous
characteristics inherited  f. gradual change.

An understanding of how speciation occurs as a result of geographic isolation.

How new evidence from DNA research and the emergence of resistant organisms support Darwin's theory.