If individuals do not evolve then how does a for example a bird population with small beak then after a long period of time have long beaks.???? Please explain!!!
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This is Natural Selection. Mutation causes a variation in allele frequencies in a population. IF a bird possesses a mutant allele for a long beak and all other birds have short beaks AND the long beak phenotype allows the bird to have an advantage over other birds (long beak helps it reach food, long beak attracts mates, etc.) then you will NATURALLY see more long beaked birds present in the population. Because the long beak is advantageous.
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Of course all mutations originate in single individuals. Through sexual reproduction, the mutation can then be passed along to subsequent generations. An individual of a small beaked bird population may have a mutation that gives it a big beak. This mutation can be passed along to its descendants. If this mutation is advantageous, then its descendants will be more fit, leave more descendants and the mutation will then increase in frequency within the population through natural selection. Of course, assortative mating, in which individuals with large beaks prefer to mate with one another, would help increase the % of individuals with large beaks in a population even faster. There can be further increases in beak size if natural selection continues to favor larger beaks.