DO NOW Wednesday March 26th, 2019 STANDARD

Mechanism of Evolution (day 2) Describe the processes of genetic drift, gene flow, and non-random mating; and explain how they result in evolutionary change

Natural Selection: Evolution Vocabulary Review: Evolution: a change in a heritable trait in a population over time Heritable: able to be passed from one generation to the next Population: the total of all the organisms of the same species

Natural Selection Review Natural selection: Organisms that are best adapted to an environment survive and reproduce more than others one of the main methods by which evolution occurs Requires 4 main principles: 1. Overproduction of Offspring More offspring are born than can survive 2. Inherited Variation Difference in phenotype of population 3. Struggle to Survive Competition for resources cause by Overpopulation Environmental pressure 4. Differential Reproductive Success Organisms with better adaptive trait will survive and pass on its genes.

Check for understanding #1 Answer at the bottom of your notes In his book On the Origin of the Species, Charles Darwin described how species change over time. Which of the following is NOT part of his observations that describes the mechanisms of natural selection?  A. Organisms produce more offspring than can survive. B. Disease and natural disaster will limit population growth. C. Species today descended with modifications from ancestral species. D. Organisms with advantages will survive and reproduce.

Mechanisms of Evolution

Definition: Movement of alleles from one population to another Gene Flow Definition: Movement of alleles from one population to another How it works: When animals migrate and breed in the new population the traits of both populations are passed on

Lots of gene flow results in: genetically Similar populations

Gene Flow Limited gene flow results in: genetically Different populations that could evolve into different species

Definition: Changes in allele frequencies due to chance alone Genetic Drift Definition: Changes in allele frequencies due to chance alone How it works: Some alleles may increase in frequency while others may decrease or become eliminated from the population.

Genetic Drift Which allele gets lost is due to random chance. Over time, drift tends to reduce genetic variation through random loss of alleles.

Genetic Drift Bottleneck effect: genetic drift that occurs after an event drastically reduces the size of a population

Genetic Drift Founder Effect: genetic drift that occurs after a small number of individuals separate from the population and form a new population

Genetic Drift Negative effects: population loses genetic variation, so they are less likely to be able to adapt to a changing environment

https://www.youtube.com/watch?v=-UfrN11V9SM

Sexual Selection Definition: Process which certain traits increase mating success and become more common in the population

Sexual Selection How it works: Females mate with males that display certain traits, so those traits get passed on to offspring

Upsetting Genetic Equilibrium Natural selection is not the only way that allele frequencies can change from one generation to the next. Gene Flow (migration) – Alleles move from one population to another Genetic Drift – a random loss of alleles. Mutation – a new mutation can add alleles. Nonrandom mating – inbreeding increases the number of homozygous traits. All of these will increase genetic variation

Breeding Bunnies

How many individuals are there? How many are homozygous dominant? The shapes below represent alleles in a individuals. Blacks represent F and white represents f How many individuals are there? How many are homozygous dominant? Homozygous recessive? Heterozygous? 3. How many F alleles are there? How many f? F F F F F f f f F F F f f f f f 8 3 3 2 8 8

FF = 8 F = 25 Ff= 9 f = 25 ff= 8

FF = 10 F = 25 Ff= 5 f = 9 ff= 2

Check for Understanding #2 Answer at the bottom of your notes. A small population of chimpanzees lives in a habitat that undergoes no changes for a long period. How will genetic drift probably affect this population? It will accelerate the appearance of new traits. It will promote the survival of chimpanzees with beneficial traits. It will increase the number of alleles for specific traits. It will reduce genetic diversity.

Check for Understanding #3 Answer at the bottom of your notes The concept of gene flow is demonstrated when a cow is driven off from its herd, joins another herd, and reproduces. When the cow contributes to the gene pool of the new herd, which of these most likely increases? Natural selection Genetic variation Environmental fitness Reproductive mutations

Check for Understanding #4 Answer at the bottom of your notes Two populations of mice living in the same forest are separated by a large water-filled ditch. After a rainstorm, flooding brings several mice from one population to the other population. When the mice from the first population reproduce with members of the second population, which of the following will likely occur? All the offspring will die as a result of reproductive mutations. The offspring will be forced to leave the second population. The offspring will be genetically identical to their parent from the first population. The offspring in the second population will have greater genetic variety.

Check for Understanding #5 Answer at the bottom of your notes Lord Howe Island is a volcanic island in the Tasman Sea that is about 11 km long and 2.8 km wide. The island has two species of palm trees, Howea forsteriana and the more abundant Howea belmoreana. The two species do not interbreed even when they grow very close to each other. Which evolutionary process fails to occur? Genetic drift of Howea forsteriana Natural selection of adaptive traits in both species Gene flow between the two species Mutations in Howea belmoreana