Bio 202 Exam 1 (Chp. 23)

During the 1977 drought on the Galápagos island of Daphne Major, the medium ground finch (*Geospiza fortis*) population declined dramatically. Which of the following describes how the population evolved?

Natural selection favored birds with larger beaks because large, hard seeds were more plentiful, though individual birds did not grow larger beaks during their lifetime.

An athlete running at high altitude develops an elevated red blood cell (RBC) count. Which principle of evolutionary biology does this observation illustrate?

Phenotypic plasticity, because the trait is an individual physiological response that will not be passed on to offspring.

What is DNA correctly defined as?

Genetic material that determines traits; passed on from parent to offspring

How are chromosomes defined as in terms of DNA?

Strands of DNA

What is a gene defined as and what do they determine?

Part of a chromosome that determines a trait

Locus (loci)

Locations of genes on chromosomes

In diploid organisms, which statement correctly defines homologous chromosomes?

They have the same length and the same gene loci, with one chromosome inherited from mom and one from dad.

Alleles

Different forms of gene that occur at a particular locus, usually appearing as two alleles per locus

What is an example of alleles in regard to hair?

An allele for widow’s peak, an allele for straight hairline

In terms of alleles, what is a dominant allele?

An allele at a particular locus that masks the effect of the other allele

In alleles, what is a recessive allele?

An allele at a particular locus is masked by the other allele

What type of alleles are Genotypes?

The alleles that are present at a particular locus

Homozygous genotype

An individual has two identical alleles at a particular gene locus (BB, bb)

Heterozygous genotype

The two alleles at a particular locus are different (Bb)

Phenotype

The appearance of an organism

What may the phenotype of an organism be determined by in regard to their appearance?

By genotype alone

What may the genotype interact with in order to produce phenotypes?

Environmental effects

How many sets of chromosomes do diploids have?

Two sets of chromosomes, one inherited from mother and one inherited from father

How many sets of chromosomes are present in haploids?

One set of chromosome, such as egg and sperms in humans

How are discrete traits defined as and determined by?

“Either/or”, and determined by one gene locus with two alleles

How are quantitative traits defined as and determined by?

A range of variation in trait, determined by multiple gene loci alone with environment

Frequencies can be described as percentages and have the ability to add up to 100%. If one allele increases in frequency, what occurs?

One or more must decrease in frequency

What does the sum of all alleles in a population represent in terms of population genetics?

The gene pool

In population genetics, how is the founder effect defined?

An event that initiates an allele frequency change in part of a population that is not typical of the original population.

What is the founder effect usually a means of?

Identifying change without knowing the cause of the chance

What does the Hardy-Weinberg equilibrium allow us to determine and describe in a non-changing population?

Genotype frequencies, describing the balance of alleles

What is the genetic structure a distribution of in regard to a population?

Different possible genotypes

What is population variation a distribution of in a population?

Phenotypes, which are usually dependent upon genetic structure and environmental conditions

What is Heritability a fraction of in terms of population?

Fraction of population variation that can be attributed to its genetic variability

What does the diversity of Genetic variability contain?

Diversity of alleles and genotypes in a population

What is a genetic drift a result of and cause alleles to randomly achieve?

Random mating, which causes alleles to randomly achieve fixation

What impact does population size have on the rate at which genetic drift causes allele fixation?

Smaller mating pools experience genetic drift more strongly, leading to allele fixation at a faster rate.

A severe wildfire drastically reduces a breeding population of rodents to a handful of individuals. What evolutionary phenomenon and genetic consequence are most likely to occur?

A population bottleneck, resulting in a drastic reduction in overall genetic variation.

What does gene flow represent?

A strong evolutionary force, resulting in immigration and emigration of alleles within a gene pool

What type of flow between populations can prevent the effects of genetic drift, maintaining genetic variation?

A relatively small but steady flow of alleles between populations

What is known as the ultimate source of genetic variation?

Mutation

What does a mutation need to affect in order for it to be selected for or against it?

Reproductive outcomes

In Non-random mating, what are changes in a population’s gene pool due to?

Mate choice or other forces that cause individuals to mate within certain phenotypes more than others

What is assortative mating the tendency of in terms of an individual’s appearance?

The tendency of individuals that look similar phenotypically

What does temperature-dependent sex determination affect, for example, through incubation temperatures?

Sex of offspring in organisms such as, reptiles

In Central Africa, why is the sickle-cell allele (\\(Hb^S\\)) maintained in human populations through stabilizing (balancing) selection?

\\(Hb^N/Hb^S\\) heterozygotes have greater fitness because they are protected from malaria without suffering severe sickle-cell crises.

In scale-eating cichlid fish of Lake Tanganyika, individuals are either left-mouthed or right-mouthed. How does frequency-dependent selection maintain both phenotypes?

Natural selection favors whichever phenotype is currently less common, as prey guard against attacks from the more common phenotype.

According to the biological species concept, how is a species defined?

A group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring with members of other such groups.