9) Microevolution pt A.

2 types of evolutionary processes

• Microevolution

• Macroevolution

Microevolution

• Small scale genetic changes within a population in response to environmental changes

Macroveloution

• Large scale evolutionary pattern in history like speciation and the origin of higher taxonomic groups

Taxonomy

• The scientific study of naming, defining, and classifying biological groups based on shared characteristics

Plastic traits

• An organisms ability to change its phenotype in repose to the environment

• Flamingo Skin and Hydrangea color

Classifying Evolution

• The changes must be genetic, populational, and generational.

Qualitative variation

• Less common

• Polymorphism

• A trait that exist in 2 or more discrete states in the same species

  • Blue and White now geese

  • Panama frogs coloration

Quantitative Variation

• More common

• Continuous

• A traits that usually vary continuously across a population

  • Humans height variation

  • Horses variation in running speed

Variation in Variation

• Some snails species have more shell size variation than other species.

• A low-wide histogram = large variation

• A tall-thin histogram = small variation

Genotype

• An organisms genetic information

Phenotype

• The set of observable physical traits

• Reflect an interaction between genotype and the environment

• Nature + nurture

How to test if variation in a trait is caused by genetics or the environment (flower height)

• Grow the organisms in different environments

• Breed like individuals

• Then observe if differences persist or disappear.

Persistent vs disappearing traits after manipulation

• Persistent = probably determined by genetics

• Disappear = probably determined by environment

Mice genetic basis of wheel behavior

• Artificial selection enhanced wheel running speed and distance

Chromosomal locus

• The position of a gene or other DNA sequence on a chromosome

Allele

• The differences in genes that determines a specific trait

• B = the dominant traits

• b = the recessive trait

• One from each parent

Population genetics

• A field of biology that studies the genetic composition of population and what alters this genetic composition

Genotype frequency

• How common a certain pair of alleles is in a population

• How common is each genotype in the population

• The proportion of individuals with each genotype (BB, bb, or Bb)

Allele frequency

• How common each allele is in a population compared to the total number of alleles for the gene

• a change in allele frequencies = evolution

Hardy -Weinberg Equilibrium model

• Calculates allele frequencies

• When at equilibrium frequency doesn’t change across successive generations

Allele and Diploid equation

Alleles: p+q = 1

Diploid: p² + 2pq + q² = 1

• What is the frequency of dominant and recessive alleles

• What is the frequency of individuals with the 3 different genotypes in the population

Answers

5 factors that can push a population out of HW equilibrium

• Mutation

• Gene Flow

• Non-random mating

• Genetic drift

• Natural selection

Mutation

• UV lighting and chemicals can cause random heritable changes to DNA

• Mutations create new DNA sequences resulting in new alleles

• In most multicellular organisms, only mutations in germ cells are transmitted to offspring

• Most mutations are harmful and decrease reproductive success

Gene flow

• Individuals immigrate to existing populations and bring their alleles with them

• This caused different populations to become more similar

• It may introduce +, -, or ± alleles to a population

No-random mating (sexual selection)

• Selection of mates based on their phenotype

• Effects on reproductive success

  • It often increases success of individuals with unusual traits

  • It could increase the frequency of alleles with + , -, or ± impacts on survival

Genetic drift

• A change in frequency of alleles in a population sue to chance events

• Small populations are more vulnerable

  • loss of a few individuals can drastically change allele frequencies and genetic diversity

• Often harmful because of the loss in genetic diversity

Formation of small population

1. Founder effect

2. Bottleneck effect

3. Chance events

Founder effect

• When a few individuals start a new population

• They carry only a small sample of the original population’s genetic variation

Bottleneck effect

• A catastrophic event dramatically reduces the size of a population

• The surviving subset population only passes on some of the original populations alleles.

  • Cheetah

Chance events

• Natural disasters eliminate rare alleles making the new population genetically distinct from the original population

• Brown beetles getting stepped on more because of bad luck :(

Natural Selection

• When individuals have a between chance at survival and reproduction die to heritable traits and live to pass them on. 

• It can cause one allele to replace another or increase allele variation

• The positively effect reproduction success

Three types of natural selection

• Directional selection: Favor increase or decrease

• Stabilizing selection: Favor mean

• Disruptive selection: Favor only Extremes 

According to Darwin’s theory what drives the process of natural selection

• Competition for limited resources

Is competition for limited resources necessary for evolution to operate

NO!!!!

Can happen though gene drift, gene flow, sexual selection, and mutation

In an isolated population of fruit flies, 4% of the individuals have pink eyes, a homozygous recessive condition, and 96% have the dominant black eye phenotype. What percentage of the population are heterozygotes?

32%

Learning Objective

• Define evolution as descent with modification in heritable characters within a population.

• Distinguish evolution from other forms of biological change such as plasticity, individual development, and ecological succession

• Describe the differences between quantitative and qualitative phenotypic variation.

• Distinguish between genotype and phenotype.

• Discuss the role of the environment in shaping phenotype.

• Design experiments that test for a critical role of genetics in the development of a phenotypic response.

• Solve problems using the H-W equilibrium equation to determine the frequency and number of (a) the dominant and recessive alleles, and (b) the homozygous dominant, heterozygous and homozygous recessive genotypes in a population.

• Use the H-W equilibrium equation to determine whether a population has evolved.

• Distinguish between the five agents of evolutionary change.

• Distinguish between directional, stabilizing and disruptive selection.

• Indicate conditions that would resist evolutionary change in a population.