The Mechanisms of Evolution

EQ: In what ways can the availability and frequency of genes in a population change over time?

New Vocabulary: Evolution- Changes in genetic information over time. Allele frequency – the frequency that a certain allele is expressed in a given population. More favorable variants become more frequent over time. Adaptation – an inherited trait that increases an organism’s rate of survival in its current environment

New Vocabulary - Continued Evolutionary mechanisms – processes that alter the allele frequency of an organism and are responsible for evolutionary change. Gene flow – movement of genes from one population to another Genetic drift – random fluctuations of allele frequencies in a small population. Natural selection – the process by which organisms better suited to their environment survive and reproduce

Evolution - Recap As the immediate environment of a population changes, the survivability of the organisms in that environment will change as well. Some will be better adapted - Kangaroo Rat in the desert can survive for months without water Some will not survive – A frog in a drought.

Evolution Recap - As animals survive or perish the traits they carry will either become more frequent or less frequent in the population. We call the processes by which these changes in survivability occur – the mechanisms of Evolution: Gene Flow Natural Selection Genetic Drift

Evolution – No Pokemon Here Evolution only occurs at the population level. Genetic change in an individual is considered a mutation, and may not be passed onto the rest of the population. Mutation is not a mechanism of evolution, but it is a factor. Mutations create variation in a population.

Knowledge Check - Kahoot Please go to Kahoot.it

Gene Flow When individuals of a species move from one population to another, this is called gene flow. We see this in: Lions, the male adolescents move away from their birth pride to found their own. A Maine coon cat is brought to an island where only wild tabby cats live. After mating with other cats on the island, some of the kittens have bushy tails and tufted ears. Seeds and pollen from conifers on one side of a valley are blown high into the air, eventually reaching and pollinating trees on the other side of the valley.

Genetic Drift Unlike the more commonly known mechanism – Natural Selection – Genetic drift is a simple process that can change the allele frequency of a population over time. Some things need to be in place: Small Population Random occurrence – the trait being affected cannot be selected for or against for genetic drift to occur. Can be a dominate or recessive trait Limited to no gene flow occurring – Isolated population.