Microevolution Exam Review

defined as simply a change in gene frequency within a population

microevolution

microevolution can be observed over a ___ period of time

short (for example, between one generation and the next)

antibiotic resistance, pesticide resistance HIV strains evolving resistance to antibiotic resistance, body size in house sparrows, etc are all examples of

microevolution responding to shifting environmental circumstances

Microevolution occurs because natural selection favored the gene because the population received

new immigrants carrying the mutant gene

a population is defined as

A group of interbreeding individuals of the same species inhabiting the same space at the same time.

the more offspring an organism can produce,

the higher its fitness

As novel traits and behaviors arise from mutation,

natural selection perpetuates the traits that confer a benefit

Variations in appearance or functions that are passed from one generation to the next

phenotypic variations

phenotypic variations within populations may be caused by

genetic differences, differences in environmental factors or due to an interaction between the genetics and the environment.

Black coat coloration of rock pocket mice from NM is an example of

genetic variation (different genotypes, same phenotype)

only ___ based variations are subject to evolutionary change

genetically

quantitative vs qualitative traits

quantitative - measurable phenotype that depends on the cumulative actions of many genes and the environment (height, weight, blood pressure)

qualitative - a trait that fits into discrete categories, existing in two or more polymorphisms. (eye color, etc)

what are the sources of genetic variations?

generation of new alleles through small scale genetic mutations in the DNA (base-pair substitutions, deletions)

rearrangement of existing alleles by genetic recombination events during crossing over, independent assortment, and random fertilization

some genetic changes are silent because

the variations in the protein-coding genes do not change the amino acid sequences of the proteins for which the genes encode

gel electrophoresis and DNA sequencing technologies are used to

detect genetic polymorphisms at protein and genome levels

The quantitative study of the distribution of genetic variation in a population, and of how the frequencies of its alleles are maintained or changed.

population genetics

the theory in the field of population genetics stems from three premises:

DNA can replicate

DNA mutates and recombines

the information in DNA interacts with the environment to produce traits

Sum of all alleles or gene copies at all gene loci in all individuals in a population

gene pool

Percentage of individuals in a population possessing a certain phenotype.

genotype frequencies

The relative abundance of the different alleles in a population.

allele frequency

Sum of the allele frequencies and genotype frequencies should add up to

1

why are null models used in population genetics?

they are used as theoretical reference points against which observations can be evaluated (controls)

A mathematical model that describes how genotype frequencies are established in sexually reproducing organisms.

hardy-weinberg principle

hardy-weinberg equilibrium suggests that

A population’s allele and genotype frequencies remain constant unless there is some type of evolutionary force acting 3 on them. It basically specifies conditions under which a population of diploid organisms achieves genetic equilibrium.

what are the conditions of hardy-weinberg equilibrium?

1. No mutations are occurring.

2. The population is closed to migration.

3. The population is infinite in size.

4. All genotypes survive and reproduce equally well.

5. Individuals mate randomly with respect to genotypes.

If one of the conditions of the hardy-weinberg principle is violated…

a population’s allele frequencies will change, microevolution occurs

what is a mutation?

a spontaneous and heritable change in DNA

what are the 4 types of mutations? briefly describe each.

deleterious - alter in harmful ways

lethal - kill all carriers (if dominant) or only homozygous carriers (if recessive)

neutral - neither harmful nor helpful

advantageous - alter in helpful ways

Ehlers-Danlos syndrome: what type of mutation, characteristics

deleterious mutation in the gene coding for collagen

weak joints, hypermobility, loose skin, could result in sudden death from the rupture of major blood vessels, the colon, or the uterus.

dermatosparaxis Ehlers-Danlos syndrome (dEDS)

inherited connective tissue disorder associated with extremely fragile skin leading to severe bruising and scarring, saggy skin, hernias, characteristic facial appearance

Huntington’s disease is an example of what kind of mutation?

lethal (dominant allele)

sickle cell anemia is an example of what type of mutation?

lethal (recessive allele)

Movement of organisms or their gametes or genetic variations from one population to another (migration)

gene flow

Young male baboons move from one local population to another experiencing aggressive behavior by older males. this is an example of

gene flow

___ are responsible for gene flow in plant populations

Dispersal agents (e.g., wind or animals)

Blue jays act as agents of ___ as they carry acorns from one oak population to another.

gene flow

Chance events that cause allele frequencies in a population to change unpredictably.

genetic drift

what are the types of genetic drift?

founder effect, population bottlenecks

founder effect

When a small group splits off from the main population to find a new colony

Ellis-Van Creveld syndrome in the Amish community is an example of…

founder effect

population bottlenecks

When a population is sharply reduced in size by a natural disaster or animal poaching, disease, drought

Elephant seal population in Pacific Northwest decreasing due to hunting is an example of

population bottleneck

population bottlenecks cause lack of ___

genetic diversity and variability in the population

process by which heritable traits that enable some individuals to survive and reproduce better than others become more common in subsequent generations.

natural selection

what are the three modes of natural selection?

directional, stabilizing, and disruptive

directional stabilization.

Individuals near one end of the phenotype spectrum have the highest relative fitness. Most common form of selection, especially in artificial selection.

example: Body size and color in guppy fish populations, selection to produce domestic animals and crops (small-sized chihuahua’s, intense bite chili peppers)

stabilizing selection

Individuals expressing intermediate phenotypes have the highest relative fitness.

example: Human newborn body weight undergoes stabilizing selection. Very small and very large human newborns are less likely to survive than those born with an intermediate body weight.

disruptive selection

Traits undergo disruptive selection when extreme phenotypes have higher relative fitness than intermediate phenotypes.

sexual selection

Evolution of showy structures like brightly colored feathers, long tails, elaborate courtship behaviors.

intersexual vs intrasexual selection

intersexual - interactions between males and females

intrasexual - interactions between members of the same sex (competing)

___ increases the frequency of homozygous genotypes and decreases the frequency of heterozygous alleles and recessive phenotypes are expressed, reducing fitness.

inbreeding/nonrandom mating

Genetic and phenotypic variations are maintained through masking the ___

recessive alleles in the heterozygotes

neutral variation hypothesis

Some genetic variations at the loci coding for enzymes or proteins are selectively neutral when different forms of the proteins function equally well.

what is an adaptive trait?

any product of natural selection that increases the relative fitness of an organism in its environment.

adaptation is…

the accumulation of adaptive traits over time

what are the constraints on adaptive traits?

no organism is perfectly adapted to its environment because the environment changes over time

natural selection is not an engineer that designs new organisms from scratch. Instead, it acts on new mutations and genetic variations

adaptive changes in an organism’s morphology must be based on small modifications of existing structures.