Mechanisms Producing Population Changes PDF

# Mechanisms that Produce Changes in Populations ## The Gene Pool in Populations - **Variations exist according to a population's gene pool.** - **A population** is a cluster of organisms of the same species that live together in the same area at the same time and can reproduce among each other....

# Mechanisms that Produce Changes in Populations ## The Gene Pool in Populations - **Variations exist according to a population's gene pool.** - **A population** is a cluster of organisms of the same species that live together in the same area at the same time and can reproduce among each other. - **Variations** within the population can be described by all the alleles present in its gene pool. ## The Hardy-Weinberg Equilibrium - **Showing no change or evolution in a population.** - **The Hardy-Weinberg Principle** states that the allele and genotype frequencies in a population are constant in all generations given: - **There is random mating.** - **No natural selection, genetic drift, gene flow, or mutation.** - The population is said to be in **Hardy-Weinberg equilibrium.** ## The Effect of Mate Selection in a Population - **Forces disrupting the Hardy-Weinberg Equilibrium** - During mate selection, some organisms can be "choosy," or some individuals breed with only nearby neighbors, if not inbreeding with relatives. - **Non-random mating** changes only the frequencies of the genotypes, but not of the alleles. ## The Effect of Natural Selection in a Population - **Forces disrupting the Hardy-Weinberg Equilibrium** - **Natural selection** occurs when individuals in a population respond variably to natural events or changes, favoring the survival and reproduction of the fittest. - Over generations, the allele and genotype frequencies in a population change. ## The Effect of Genetic Drift in a Population - **Forces disrupting the Hardy-Weinberg Equilibrium** - Random allele frequency changes or fluctuations can occur across generations, called **genetic drift,** especially in a smaller population or if it decreased in size at some point. - The Hardy-Weinberg model behaves as though the population is large. ## The Effect of Gene Flow in a Population - **Forces disrupting the Hardy-Weinberg Equilibrium** - Some individuals or groups in the population are added during **immigration** or lost by **emigration.** - Through migration, new alleles can possibly arise or disappear from the gene pool, known as **gene flow.** ## The Effect of Mutations in a Population - **Forces disrupting the Hardy-Weinberg Equilibrium** - **Mutations** can occur when genes are replaced, deleted, or duplicated. - Hence, it is accounted as a different type of allele and changes the probabilities of inheriting the original types of alleles in the gene pool. ## Significance of the Hardy-Weinberg Equilibrium - **Evolution in terms of allelic frequencies** - A population can show variation of traits, but huge changes and possibly new species only emerge after many generations of disrupting the Hardy-Weinberg equilibrium. - In theory, **a population is the smallest unit of evolution.** ## Conclusion/Summary - Change in a population that can be observed in allele and genotype frequencies in its gene pool across generations. It occurs when there is at least two or more types of alleles, or **genetic variation.** - The **Hardy-Weinberg equilibrium** is a model that shows how the allele and genotype frequencies do not change in a population with genetic variation, given that there is random mating and that there is no occurrence of natural selection, genetic drift, gene flow, and mutation.