Chapter 23 The Evolution of Populations

Chapter Summary:
This chapter covers four main concepts, or statements, which revolve around the evolution of populations.

1. The first concept states that mutation and sexual reproduction make the genetic variation which makes evolution possible.
2. The second concept is that the Hardy-Weinberg equation can be used to test if certain populations are evolving or not.
3. The third concept states that ceratin parts of evolution such as natural selection, genetic drift, and gene flow can possibly change allele frequencies in populations.
4. The fourth concept states that natural selection is the only thing that can cause consistant causes adaptive evolution.
*Each concept will be thoroughly discussed and explained. :)
(To comprehend this chapter vocabulary is necessary to comprehend as well)

Microevolution: change in allele frequencies in a population over generations.
Example: The theory of how a certain species evolved
Mutations: changes in the DNA
Example: The common fly has branched into different types of flies with different phenotypes

-Point Mutations: changes in one base in a gene
Example: The single base change within DNA

-Chromosomal Mutations: deletion, disruption, duplication or rearrangement of many loci at once
Example: Chromosomes which present one or many of these types of changes (changes being deletion, duplication, inversion, translocation)

Population: a group of individuals of the same species that live in the same area and interbreed
(interbreeding causes production of fertile offspring)
Example: A well known poputation is the human populations; however, there are millions of other populations such as the deer population or the eagle population

Population Genetics: the study of how populations change genetically over time
Example:This is a phylogenetic tree that shows how each of these animals are connected through past ancestors.

Gene Pool: the stock of different genes in an interbreeding population
Example: These are some type of warthogs or pigs which have different genes within their breeding population

Sexual Reproduction: mieosis producing sperms and eggs that are not all identical
Example: This cycle is represented by all orangisms that reproduce sexually, not asexually

Average Heterozygosity: measures in the average percent of loci taht are heterozygous in a population
Example: Zebra mussels have an average heterozygosity of 0.27-0.43
Hardy-Weinberg Theorem: used to describe a population that is NOT evolving
Example: The first picture is Hardy and Weinberg. The second picture shows a species that maintain a stance instead of evolving.

Natural Selection: the only process which consistantly causes adaptive evolution
Example: This presents natural selection within birds. See how the birds like green beetles over the orange colored beetles? This means that orange beetles will become more abundant over time because the birds will continue to consume their "favorite" beetles.
VIDEO: This video explains natural selection. It is about eight minutes. :)

Genetic Drift: unpredictable changes in allele frequencies from one generation to the next generatio
Example: Here is a beetle species which has been disrupted due to an unpredictable occurance.

-Founder Effect: occurs when a few individuals become isolated from a larger population
Example: example below -->

-Bottleneck Effect: a sudden decrease in population size due to a change in the enviornement
Example: In this case a few of the organisms with the genotype bb survive a unpredictable disaster. These organisms become the originators of a new population. While the new populations reproduce, the new gene pool is very different from the original.

Relative Fitness: something an individual gives or contributes to the gene pool of the next generation
Example: This shows the relative fitness, directly according to alleles and also how it effects the next generation.

Quiz yourself on the vocabulary here! --->

Concepts In Depth:How does evolution occur to a population?-Only populations evolve over time and the key is variation.What causes variation in gene pools?-Mutation and sexual reproduction cause variation in gene pools.Sexual Reproduction/Mutation- refer to vocabulary section.*Varation in genotypes mean that there will be variation in phenotypes.What is an example of a quantitative characteristic?-height-weight^^^ sometimes it is easier to change these types of characteristics.Most species show geographic variation differences between gene pools of separate populations.Example: This ring species shows the same organism with different phenotypes, yet it's still the same species. Something strange is that the bottom left species and bottom right species can not mate, but everyone else can. l_052_05_l.jpgA Cline is something very relevent to types of organisms connected to a certain evniornment change. The direct defintion is: occurs along a geographic axis.Example: Physical changes within a species in an enviornmental changes; thus, these plants due to what type of area they are living in.cline.gifAs far as mutation goes, rates of that happening in plants and animals are quite low.

*Locus- is fixed if all individuals in a population are homozygous for the same allele.

For diploid organisms, the total # of alleles at a locus is the total # of individuals is multiplied by two (X2).The total # of dominant alleles at a locus is 2 alleles for each homozygous dominant individuals plus 1 allele for each heterozygous individual.(p + q = 1)Hardy-Weinberg Equilibrium: p^2 + 2pq = q = 1To find step by step instructions and a very thorough explaination visit the link below. you prefer a speaker to walk you through the steps, visit the link below.

If you don't want to do all of that yucky math there is a super secret short-cut (VISIT LINK BELOW!)
*Just plug in the numbers*
FIVE CONDITIONS: Where if one does NOT happen then evolution occurs.

1. No mutations

2. Random Mating

3. No natural selection (This is the main evolution drive)

4. Extremely large population size

5. No gene flow

THREE major factors that influence allele frequency

1. Natural Selection- Different success
2. Genetic Drift- Change in allele frequencies
3. Gene Flow- Movement of alleles among a populationNatural Selection is the only thing that constantly causes adaptive evolution.There are THREE models of selection:The original is the Bell curve:Bell_Curve.gifThe three different types are as follows: asdf.pngHere are some questions to help you study for the test on this chapter.
1. Compare and contrast the bottleneck effect and the founder effect as causes of genetic drift.
2. Why might diseases pose a greater threat to cheetah populations than to mammalian
populations having more genetic variation?
3. Which mechanism of microevolution has been most affected by the ease of human travel
resulting from new modes of transportation?
4. What is incorrect about describing evolution by natural selection as a random process?
Video: Overview of Evolution in Populations and in depth explianation of the bell curves. THE END :)