Ch:22(cont) & Ch 23

Chapter 22 (cont.)

vestigial organ- are those that are historical remnants of structures that were functional in ancestors. ex) appendix, eyes of bats

2 other types of homologies are:

embryological homologies- which are most prominent during development

molecular homologies-which occur when organisms share characteristics on the molecular level, such as using the same method for reproducing DNA and other cellular processes.

The picture shows embryos of several different animals

DNA analysis and protein comparison is the best technique for determining the phylogenetic relationship among several closely related species.

phylogenetic- system used to determine common ancestor through graphing.

Chapter 23

Individuals do not evolve.. Populations evolve!

mutation and sexual reproduction produce the genetic variation that makes evolution possible.

-genetic variation includes variation among individuals within a population in discrete and quantitative characters as well as geographic variation between populations

mutation- a change in the nucleotype sequence of an organism's DNA.

point mutation- a change of as little as one base in a gene can have a significant impact on the phenotype. ex) sickle cell anemia

Picture of sickle cell anemia point mutation.

sexual reproduction- provides the most genetic variation in a population which results from the unique combination of alleles that each individual recieves(crossing over, independent assortment, fertilization)

Hardy Weinberg equation (Lab 8)

-can be used to test whether a population is evolving.

population- a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring. Smallest unit that can evolve!

gene pool- all the alleles for all the loci in all individuals of the population. If only one allele exists for a population then that allele is said to be fixed.

The gene pool of a population that is not evolving can be described by the Hardy Weinberg principle. The principle states that the population will remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.

equation

(allele frequency) p + q= 1

p- dominant allele

q- recessive allele

(geneotype frequency) p^2 + 2pq + q^2=1

p^2- homozygous dominant

2pq- heterozygous

q^2- homozygous recessive

Conditions for Hardy Weinberg

If one of these conditions is NOT met then the population will evolve.

1) No mutations

2)Random mating

3)No natural selection

4) Extremely large population size

5) No gene flow (immigration, migration)

Natural Selection, Genetic drift, and gene flow can alter the frequencies of a population.

A deviation from any of the 5 conditions is a potential cause for evolution. Now mutations can alter allele frequencies, but because mutations are rare the change from generation to generation is small. Non random mating might affect frequencies of homozygous and heterozygous genotype, but typically has little effect on allele frequencies.

Allele frequency needs to shift for evolution to happen

Example of Genetic Drift:

Multiple Choice Questions

1.) What provides the most genetic variation?

a) mutation

b) point slope mutation

c) sexual reproduction

d) gene pools

2.) Which equation should be used to best describe the allele frequency?

a) a^2+b^2=c

b) p^2 + 2pq + q^2 = 1

c) p+q = 1

d) 3a +2b = 1c

3.) Which is NOT a condition for Hardy Weinberg?

a) No mutations

b) non-random mating

c) No natural selection

d)extremely large population size

e) no gene flow

4.) _____. ______, and ________ cause most evolutionary change.

a) sexual reproduction, natural selection, and gene pool

b) natural selection, genetic drift, and mutations

c) gene flow, genetic drift, and gene pool

d) natural selection, genetic drift, and gene flow

5. The allele y occurs with a frequency of .8 in a population of clams. Give the frequencies of geneotypes yy, Yy and YY.

Answers : 1. (c) 2. (c) 3.(b) 4. (d)

answer to 5:

q=.8

1-.8=p

p=.2
p^2+2pq+q^2=1

(.2)^2+2(.2)(.8)+(.8)^2=1

p^2=.04= 4%

2pq=.32=32%

q^2=.64=64%

Total=100%