Mechanisms of Evolution PDF

Prepared by RFS Booc  describe the basic mechanisms of evolution explain the effects of evolution on the diversity of the population show real life examples of the effects of the basic mechanisms of evolution Observe the two pictures and recognize the similarities and the diffe...

Prepared by RFS Booc  describe the basic mechanisms of evolution explain the effects of evolution on the diversity of the population show real life examples of the effects of the basic mechanisms of evolution Observe the two pictures and recognize the similarities and the differences between individuals or animals in the population. These are natural selection, mutation, genetic drift, and gene flow.  The class will be divided into 4 groups. Each group will be assigned with 1 mechanism of evolution. The group shall act it out without any dialogues and sounds, only facial expressions and body actions. By the end of performance, other groups will guess the mechanism of evolution presented. One representative must explain their performance and talk about their assigned mechanism of evolution. Preparation Time: 5 minutes; Presentation Time: 3 minutes  Described by two naturalists Charles Darwin and Alfred Russel Wallace  “…one species had been taken and modified for different ends.” – Darwin (1860)  Darwin called this mechanism Natural Selection: an inevitable outcome of three principles that operated in nature: 1. Characteristics of organisms are inherited 2. More offsprings are produced that able to survive; resources for survival and reproduction are limited. 3. Offsprings vary among each other in regard to their characteristics.  Whether or not a trait is favorable depends on the environment at the time.  Simply, the effect of chance  Has a stronger effect on small/finite populations  It happens because the alleles in an offspring generation are a random sample of the alleles from each parent.  Genetic drift in a population can lead to the elimination of an allele from a population by chance.  Bottleneck effect – when a species goes through an event that suddenly and significantly reduces its population  The genetic structure of the next generation may be very different from the previous generation. Bottlenecking Events include: Hurricane, lava flow, unusually cold temperatures at night, etc.  Founder effect – a scenario in which a new population is started by a small group from a larger population Happens when: 1. A population leaves and start a new population in another location 2. Population get divided by a physical barrier Mutation is the change in the DNA sequence of a gene. Various phenotypic effects: 1. Harmful – gives reduced fitness 2. Beneficial – positive effect on fitness 3. Neutral – no effect on fitness Various phenotypic effects: 1. Harmful – gives reduced fitness 2. Beneficial – positive effect on fitness 3. Neutral – no effect on fitness Various phenotypic effects: 1. Harmful – gives reduced fitness 2. Beneficial – positive effect on fitness 3. Neutral – no effect on fitness  Harmful mutations are removed and beneficial mutations will spread through the population through selection Its effect on evolution is small Mutation is the ultimate source of genetic variation of all populations.  AKA Migration Flow of alleles in and out of a population resulting from the migration of individuals  It can occur when: An individual travels from one geographic location to another and joins a different population of the same species Plant seeds get sent far and wide through wind or animals and may introduce new alleles to another population MECHANISMS OF EVOLUTION 1. Natural Selection 2. Mutation 3. Genetic Drift 4. Gene Flow  “Nothing makes sense in Biology except in the light of Evolution.” – Theodosius Dobzhansky