Evolution can be defined as a natural process where slow and time taking gradual changes occurs in a permanent manner. Evolution means permanent changes occurs in the genome of an organism like from bacteria up to human being which occurs on the basis of present condition.Generally, there are two reasons of evolution such as natural task for survival and reproduction. For example: Earlier giraffe neck was small and food were present on ground so giraffe stretch neck to get that food therefore due to some vital internal force giraffe neck in present condition it is large. Therefore, evolution can be considered as the variation or changes which occur at the generation level.
There are various reasons for particular changes in a genome over a period of time they can be summarized as, Natural selection, Mutation, Genetic drift, Recombination, Independent assortment.
Types of evolution:
There are 2 types of evolution:
- Micro evolution: Micro evolution can be termed as or when the evolution occurs at the level of alleles, genes, chromosome, cell, tissue, organ, organism and below the population level then it is called as micro evolution. In micro evolution changes does not occurs in a species. For example: Sewall wright effect and Hardy Weinberg principle.
- Macro evolution: It can be defined as the changes or evolution or variation when occurs at the species, genus, family order, phylum or kingdom level then it is macro evolution. In macro evolution changes occurs in a species. For example: The changes at the species level were studied by the scientist Lamarck and Darwin.
Lamarck and Lamarckism: Lamarck was one of the naturalists, biologist an and the academic. He was born in 1744 anddied in 1829. During his lifetime he searched on many areas of evolution. In 1801, the scientist were invented the term invertebrate whereas in 1802 he gave the term biology He proposed hypothesis transformism.
Transformism: The idea were also called as Lamarckism, according to this theory one species converts to other or one species transform into other. It concludes that number of species according to Lamarck remains same.Therefore it is also called as anagenesis.
Darwin’s Hypothesis:It is also called asDarwinism. According to Darwin’s hypothesis one species get diversified into other species. Branching evolution occurs. It is also called as divergence or diversification. According to this theory number of species increases therefore also called as cladognesis.
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