Over the course of history, there have been two theories of evolution.
Lamarck and Darwin both proposed theories of evolution but only Darwin’s theory is recognised.
Lamarck’s theory was based on the law of use and disues and the law of inheritance of acquired characteristics.
His theory was basically that the more you use a muscle or organ the bigger and strong it will get, and that characteristic will be passed on to your offspring.
If you don’t use an organ it will eventually disappear.
This theory was eventually discredited with the introduction of Darwin’s theory. This is because in Lamarck's theory organisms continue to get complex. If this was the case, why are there still single celled, simple bacteria?
Charles Darwin is thought of as the god father of evolution. The main features in his theory are that:
Individuals compete for limited resources
Individuals in a population show natural variation
Individuals with characteristics best suited to their environment are more likely to survive and reproduce.
Successful characteristics are inherited.
Species which cant compete die out, while those who can reproduce.
If we compare the two theories with the giraffe you can see just how different they are.
a giraffe stretches its neck to reach food high up
the giraffe's neck gets longer because it's used a lot
the giraffe's offspring inherit its long neck
a giraffe with a longer neck can reach food high up
a giraffe is more likely to get enough food to survive to reproduce
a giraffe's offspring inherit its long neck
Darwin visited the Galapagos islands and found a group of finches.