Presentation on theme: "1 Lesson 25 – Evolutionary Processes Life Science."— Presentation transcript:
1 Lesson 25 – Evolutionary Processes Life Science
2 Lesson 25 Look at the structures in this lesson. Can also look this website on mechanisms of evolutionmechanisms of evolution
3 Mechanisms of Evolution Change in how common a gene is in a population (gene frequency). Can result from gene flow, non-random mating, genetic drift, mutation and natural selection.
4 Gene Flow (Migration) Movement of genes from one population to another. (Image from http://evolution.berkeley.edu/evosite/evo101/images/beetles_mech2.gif)http://evolution.berkeley.edu/evosite/evo101/images/beetles_mech2.gif
5 Nonrandom Mating The probability that two individuals in a population will mate is not the same for all possible pairs of individuals. The result is that some individuals have more opportunity to mate than others and thus produce more offspring (and more copies of their genes) than others.] (Image from http://biology.unm.edu/ccouncil/Biology_203/Images/PopGen/nonrandom.jpeg)http://biology.unm.edu/ccouncil/Biology_203/Images/PopGen/nonrandom.jpeg
6 Genetic Drift Random changes in gene frequency. Occurs when some individuals, just by chance, leave behind a few more descendents (and genes) than other individuals. The next generation will be the genes of the “lucky” individuals, not necessarily the healthier or “better” individuals. (Image from http://evolution.berkeley.edu/evosite/evo101/images/beetles_mech3.gif )http://evolution.berkeley.edu/evosite/evo101/images/beetles_mech3.gif
7 Mutation Change in DNA. Mutations add to the genetic variability of populations over time.
8 Natural Selection Individuals having characteristics that aid their survival will produce more offspring. As a result the proportion of their genotype will increase in the population over time. (Image from http://www.answersingenesis.org/assets/images/articles/nab/h-pylori.jpg)