Living Environment Translated Arabic 2014 | Page 92

B. General Notes
1. Evolution is one of the central ideas of biology. It explains how
living things have changed in the past and is the basis for
predicting how they might change in the future.
2. Evolution is change in the characteristics of a species over time.
3. There are two model about the speed of evolution :
a. Gradualism- a model that describes evolution as a slow
process by which one species changes into a new species
through a continuing series of mutations and variations
over time.
b. Punctuated equilibrium- a model that describes the rapid
evolution that occurs when mutation of a few genes
results in a species suddenly changing into a new species
4. Lamarck proposed the hypothesis of inherited acquired
characteristics. He said that changes in the environment caused
the organism’s behavior to change, leading to greater use or
disuse of a structure or organ. This was proven to be incorrect.
5. Charles Darwin developed the theory of evolution by natural
selection to explain how evolutionary changes account for the
diversity of organisms on Earth.
6. Darwin proposed evolution by natural selection:
a. Organisms best suited to their environments are most
likely to survive and reproduce ( competition)
b. Organisms have more offspring than can survive.
( overproduction)
c. Individuals of a species vary and these variations are
passed to offspring. ( variation)
7. Adaptations are variations that help an organism to survive or
reproduce in its environment.
8. Mutations are the source of new variations.
9. Evolution may be a slow or fast process depending on the
species under study.
10.Fossils are traces of organisms that existed in the past.