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Evolutionary Relationships I
Evolutionary Relationships 1
Evolution is the sequence of gradual changes over millions of years in which new species are produced.
Charles Robert Darwin was an English naturalist who observed various species of life on the earth, and put forward the idea of “evolution of species by natural selection.” He said that a species inherits its characters from its ancestors.
Variations are the differences among individuals of a species, caused by genetic and environmental factors.
Mutation is the change in the sequence of the nitrogen base pairs in DNA. A mutation in the gene for green colouration in green beetles leads to offspring with brown colouration.
Gene flow is the transfer of genes from one population to another due to migration. Breeding between the brown and green beetles introduces new gene combinations into the population.
Natural selection explains that organisms that are physiologically or behaviourally better adapted for the environment are selected; they can survive and reproduce. The green beetle is better adapted to the environment than the brown beetle.
Genetic variation in small populations caused by an environmental factor is called a genetic
Species can be defined as a group of individuals of the same kind that can interbreed and produce fertile progeny.
Speciation is an event that splits a population into two independent species, which cannot reproduce with each other.
Process of speciation - genetic drift: Occurdue to changes in the frequencies of particular genes by chance alone. If a hurricane strikes the mainland, and bananas with beetle eggs on them are washed away to an island, it is called a genetic drift.
Process of speciation - natural selection: Variations caused in individuals due to natural selection, which leads to the formation of a new species. Ecological conditions are slightly different on the island as compared to the mainland. This leads to a change in the morphology and food preferences in the beetles over the course of generations.
Process of speciation - splitting of population: A population splits into different sub-populations due to geographical isolation that leads to the formation of a new species.
