Exam 1

Concepts and Vocab

Proximate Cause

the immediate cause of an adaptation

Ultimate Cause

the historical reasoning behind an evolutionary adaptation

Evolution

the inherited changes over the course of generations

Hypothesis

an educated statement about what you think might be true but needs more evidence to be proven

Theory

a comprehensive statement based in reason and evidence, proven true

Lamarckism

Change occurs within a generation. One individual adapts during their lifespan and the traits they gain (e.g. big muscles) gets passed down to their offspring (e.g. baby born with big muscles)

Darwin’s Hypothesis of Evolution

The species starts with a variation of traits and who survives in the generation determines who passes on their traits. (Giraffe born with long neck lives instead of one with shorter neck, their baby also get born with a long neck)

Descent with Modification

All species come from one common ancestor that has evolved into many lineages as they accumulated differences.

Natural Selection

Variations in traits that are successful to the survival of an individual are passed down to their descendants, while variations in traits are harmful to the survival of an individual die or unable to have progeny.

Mendel’s Theory of Particulate Inheritance

e.g. Parent A brings in 4 genes and Parent B also brings 4 genes. They are put into a bowl and get mixed up, child grabs one handful of genes, a mix of both parents.

Synthetic Theory

evolution is caused by natural selection acting on particulate inheritance

Microevolution

Evolution within a species

Macroevolution

Evolution that leads to new species

Naturalistic Fallacy

Thinking that everything that is natural is good

Gregor Mendel

The Father of Modern Genetics. Cited for the “Law of Segregation”, the “Law of independent assortment”, particulate inheritance, and framework for hereditary.

Parental Generation

Pure-bred/homozygous parents

First Filial Generation (F1)

the generation of offspring from the crossing of two organisms

Genotype

the alleles of an organism inherited from both parents (Yy, YY, or yy)

Phenotype

The observed traits of an organism (YY—> Yellow, yy—>Blue)

Law Of Equal Segregation

During meiosis, alleles of a gene pair segregate equally into gametes (Yy—> Y and y), and then fuse at fertilization with the other parents gametes. Creating ratios of 3:1, 1:1, and 1:2:1 for gene inheritance.

Locus

Formal term for gene

Law of Independent Assortment

Alleles of different traits segregate from each other during meiosis. The inheritance of one gene does not influence the other. Creating a 9:3:3:1 ratio when looking at dihybrid crosses.

R A Fisher

Who combined mendelian inheritance w/ darwinian natural selection?

Polygenic inheritance

Many genes control the expressed traits. 3 genes can factor into what the eye color is.

Incomplete dominance

Heterozygote phenotype is an intermediate between the homozygotes. e.g. white and red alleles make pink heterozygous alleles.

Codominance

Heterozygote is expressed of both homozygotes. e.g. white and red alleles make white and red alleles.

How models of blending inheritance result in convergence of the mean of a trait?

Blending inheritance results in a reduced variation.

Why, in avoiding characters that have variable penetrance and expressivity, Mendel was wise in his choice of character?

Mendel choose phenotypes that were discrete and contrasting of each other. The traits he chose did not have influence over each other which would have made finding how they passed down traits harder.

How, in a classical one locus, two allele,s, one dominant, one recessive case, the phenotype ratio in the F2 is 3:1 in a cross between two pur breeding lines, whereas the genotypic ratio is 1:2:1

When the dominate and recessive alleles come together as alleles, genotypically they represent the 2 in the 1:2:1 ratio, but when they are expressed phenotypically, the recessive allele is not expressed because the dominate one is dominate. Heterozygous genes will show as dominate.

Hardy-Weinberg equation

p²+2(pq)+q²=1 —→ genotype frequencies. p²=AA, 2(pq)=Aa, and q²=aa.

Populations can only have 2 allele variations, T/F?

False, in populations you can have more than 2 variations of a allele.

Why does heterozygosity matter?

It measures the genetic variation available in a population.

What are assumptions for the Hardy-Weinberg Relation?

A large population size, random mating occurs, no selection forces on alleles, no migrations occurs, and no mutations to genes.

What are forces of evolution?

Selection, genetic drift, inbreeding, migration, and combination.

What does it mean when an allele is fixed?

The allele frequency is at 100%

What happens when a balancing selection is simulated? (AA:0.95, Aa:1, aa:0.95)

Heterozygotes have a higher fitness over the homozygotes and show superitoy in the gene pool.

What happens in a balancing selection when one genotype has a higher fitness than the other? (AA:0.98, Aa:1, aa:0.97)

There is a heterozygote superiority in the gene pool, but the homozygotes fitness is balance around the 50%.

What is fitness?

The success of an organisms ability to survive and reproduce.

What is maternal effect?

The effect of the maternal genotype on the offspring

What is nonsynonymous evolution?

When there is a substitution in the nucleotide that leads to a change in the amino acid sequence, affecting protein functionality.

What is synonymous evolution?

When there is a nucleotide substitution that does not affect the amino acid sequence and the protein it translates into.

Founder event

a chance sampling event that shifts allele frequencies. (a few individuals move to a un-inhabited population, the gene pool is now only made up of their genes.) Leads to the loss of some genetic variation.

Genetic Drift

the random fluctuations in the frequency of a gene and is dependent on the population size. It is more noticeable in small populations.

Inbreeding

leads to homozygous populations and increases the probability of rare alleles to be present.

Inbreeding Coefficient (F)

measures the probability than an individual has inherited two identical alleles from a common ancestor. The higher the coefficient, the higher the chance of inbreeding. Reduces biological fitness.

What are the benefits of migration in a population?

Increases gene variation and prevents populations from differentiating.

How are mutations similar to migration?

it introduces new alleles into the population, rarely does it affect the genetics

Gene Interaction

forces do not act in isolation, but they interact, and sometimes counteract each other.

Neutral theory of molecular evolution

From Kimura, he thought that beneficial mutations are so rare that they are trivial. A majority of differences are from the fixation of neutral mutations.

Natural Selection

It acts on expressed traits. Traits needs variation, heritability, and the traits affect survivability for it to impact evolution by natural selection.

Components of fitness and there definitions:

Viability is the probability of surviving to reproductive age. Mating success is the number of mates acquired. Fecundity is the number of offspring produced per mating. Fertility is the number of offspring that survive to reproductive years.

Absolute fitness (W)

how many offspring a genotype produces. the reproductive success of that genotype.

Relative fitness (w)

the fitness of a genotype that compares to a reference genotype (set to a value of 1). Shows a genotypes fitness in proportions to the reference.

Selection coefficient (s)

the difference in fitness between a specific genotype and a reference genotype. Compares the fitness of one genotype to another.

Overdominance

genetic variation is maintained due to the selective advantage of heterozygotes.

Underdominance

the fitness of a heterozygote is lower than both homozygotes.

Selective Sweep

new adaptive mutation that spreads through a population, reducing the gene diversity

Positive selection

spread of beneficial alleles

Purifying selection

hinders the spread of harmful alleles