Friday 4/18 LT: Explain how natural selection on single-gene traits can lead to changes in allele frequencies ET: Create a vocabulary list for section 17.1 Gene pool Relative frequency Single-gene trait Polygenic trait

Wed. 2/13 – 16.1 LT: 1.Explain what a gene pool is 2.Identify the main sources of inheritable variation in a population 3.State what determines how a phenotype is expressed ET: Outline sections 16.1 and 16.2 Highlight headings and underline new vocabulary words (the bolded ones) These must be quality outlines if you want to receive full credit

Friday 4/18 – Genes and Variation _______________________________________________________ Daily Objective: By the end of today I should be able to… Explain what a gene pool is Identify that main sources of inheritable variation in a population Entrance Activity: What are the 2 important factors that Darwin was unable to explain? (17.1) Why was he unable to explain them?

Gene Pool: The combined genetic information of all the members of a particular population All the members of a population may interbreed so they share a group of common genes

Relative Frequency: The number of times an allele occurs in a gene pool Pg. 483 – How many alleles for black fur are there vs. alleles for white fur?

What are the 2 main sources of genetic variation? 1.Mutations: Any change in a sequence of DNA Q: how do mutations occur? radiation, environment, replication of DNA 2.Gene Shuffling: Your 23 pairs of chromosomes can produce 8.4 million different combinations of genes! Q: how do chromosomes get arranged so differently? Independent assortment and crossover

The number of phenotypes produced for a given trait depends on how many genes control the trait. Single-Gene Traits: Controlled by a single gene that has 2 alleles Ex. Widows peak pg. 395 Polygenic traits: Controlled by 2 or more genes, each with 2 or more alleles Ex. Height Polygenic traits produce a bell-shaped curve when graphed – “normal distribution.”

Create a data table to record the height of each individual in the room Create a graph using frequency and height, just like the one on pg. 396

Friday, February 15 th, 2013 _______________________________________________________ Daily Objective: By the end of today I should be able to… Explain genetic drift Describe the conditions necessary for genetic equilibrium to be maintained. Entrance Activity: What are the 3 ways that natural selection can affect the distributions of phenotypes

Natural Selection on… Single-gene Traits: one form of the trait all of the sudden increases fitness, allele frequency will change and evolution will take place Polygenic Traits: Natural selection can affect the distribution of phenotypes by 1.Directional Selection 2.Stabilizing Selection 3.Disruptive Selection

Directional Selection When nature selects individuals at one end of the bell curve as the fittest

Directional Selection Food becomes scarce. Key Low mortality, high fitness High mortality, low fitness

Stabilizing Selection When nature selects individuals in the middle of the curve as more fit and the bell narrows

Key Percentage of Population Birth Weight Selection against both extremes keep curve narrow and in same place. Low mortality, high fitness High mortality, low fitness Stabilizing Selection

Disruptive Selection When nature selects individuals at opposites ends of the curve as more fit.

Genetic Drift In small populations, individuals with a specific trait may leave more desendents, just by chance. When allele frequency is altered by the migration of a small population it is called the – “founder effect”

Evolution vs. Genetic Equilibrium 5 conditions can disturb equilibrium and cause evolution to occur… Hardy-Weinberg principle: Allele frequencies in a population will remain constant unless one or more factors cause those frequencies to change. Genetic Equilibrium

5 conditions that must be constant for equilibrium … If conditions are not met, the population will evolve. 1.Random Mating: All members of the population must have an equal opportunity to produce offspring. An example of this condition not being met: Female birds usually select their mates based on plumage… Colorful plumage is selected for…

2. Large Population: Large populations are less likely to be changed through Genetic Drift REVIEW!!! What is genetic drift?

3.No movement into or out of the population …because individuals may bring new alleles into a population A population’s gene pool has to be kept together and separate from the gene pools of other populations

4. No mutations Mutations introduce new alleles, which changes the frequencies

5. No natural selection All genotypes in the population must have equal probabilities of survival and reproduction. No selective pressures!!

Thursday. 2/23 – 16.3 LT: Identify conditions necessary for a new species to evolve Describe the process of speciation ET: What factors are involved in the formation of a new species? – Behavioral, geographic, and temporal isolation

Speciation The formation of new species based on a significant change in allele frequency

As new species evolve, populations become reproductively isolated from each other Reproductive isolation: when the members of two populations cannot interbreed and produce fertile offspring

Behavioral Isolation 2 populations are capable of interbreeding but have differences in courtship rituals or other types of behaviors Ex: Eastern Meadowlark and Western Meadowlark

Geographic Isolation Two populations are separated by geographic barriers such as rivers, mountains or bodies of water. Ex: Abert squirrel and Kaibab squirrel

Temporal Isolation Common water frog Rana esculenta BioEd Online 2 or more species reproduce at different times Ex: different frog species live and breed in the same pond, but they reproduce at different times of the year.

Speciation in Darwin’s Finches Read and summarize steps 1-6 on pg. 408 Compare your steps to fig pg. 410 Analyzing Data: complete the activity on pg. 408 “How Are These Fish Related” Answer #1-4 in NB

Tuesday 2/28/2012 LT: Last day to review for exam! *Test Tomorrow