Evolution is the gradual changing of a species from one generation to the next as a consequence of processes such as natural selection, mutation and genetic drift.
EVIDENCE OF EVOLUTION
1. Evidence from comparative anatomy.
2. Evidence from fossil records.
3. Evidence from vestigial organs.
4. Evidence from cytology.
5. Evidence from classification of organism.
6. Evidence from biochemistry and genetics.
THEORIES OF EVOLUTION
The chief exponents of the theories of evolution are Jean-Baptiste de Lamarck and Charles Darwin. Others who have contributed to the study of evolution include De-vides Hugo, Alfred Russel Wallace, Charles Lyell Gregor Mendel and Erasmus Darwin.
DARWIN’S THEORY(DARWINISM) / THEORY OF NATURAL SELECTION
This theory of evolution was proposed by the British naturalist. Charles Darwin (1809 – 1882). In his book on the origin of species published in 1859. Darwinism is a theory of evolution which states that present-day living organisms have developed from gradual changes over many generations as a result of natural selection. The theory of natural selection which is the basis of Darwinism states that the individual organisms which is best adapted to its environment will survive to reproduce. It can be summarized as.
3) Survival of the fittest
LAMARCK’S THEORY/ THEORY OF USE AND DISUSE
Lamarckism is an early theory of evolution proposed by the French biologist Jean-Baptiste de Lamarck (1744 – 1829). According to Lamarck, organisms develop specialized characteristics by the use or disuse of organs. He believed that acquired characteristics during an individual’s life time can be transmitted to its offspring.
Lamarckism can be summarized as follows.
i) The environment warrants an organism to have some needs.
ii) To satisfy these needs an organism may need an organ.
iii) An organ frequently used is better developed.
iv) An organ rarely used or not used at all tend to become useless and degenerates.
v) Characters so acquired are transmitted to offspring.
For more reading visit Wikipedia