chapter 23

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Explain the statement “It is the population, not the individual, that evolves.”

natural selection acts on an individual but evoloution acts on a population


Define the terms population, species, gene pool, adaptation

a population is a group of individulas in a species at the same time and area who interbreed
species is often defined as the largest group of organisms capable of interbreeding and producing fertile offspring.
a populations genetic make up composed of all variations
inherited characteristics of organisms that enhance survival and reproduction in specific enviroments


List the five conditions that must be met for a population to remain in Hardy-Weinberg equilibrium.

No mutations
Random Mating
No natural selection
Extremely large population size
No gene flow


Write the Hardy-Weinberg equation. Use the equation to calculate allele frequencies when the frequency of homozygous recessive individuals in a population is 25%.

p2(TT) + 2pq(Tt) + q2(tt) = 1; p + q = 1

q = .25


Explain how bill depth in finches on Galapagos Island exemplify microevolution

the represent the change in allele frequencies beaks did not get larger or smaller based on the drought but birds with naturally larger beaks survived thus greater frequency of large beaked alleles its an evolutionary change in a population


List and explain the mechanisms of microevolution

Genetic Drift - chance genetic changes like s moose stepping on a few flowers in a small population

Gene Flow - transfer of alles in or out of a population

Natural Selection - breeding out


When are point mutations harmful and harmless?

point mutations are bad when they make the organism less suitable but sometimes a rare mutation can make an indiviudual better suited for its enviroment


Explain how mice and human olfactory receptor genes, moth coloration, and clover cyanide production illustrate mutations and how natural selection can act upon each mutation.

each mutation can serve a purpose to individuals in certain populations.


“Only natural selection leads to the adaptation of organisms to their environment.”

since natural selection decides what species should survive it is the only mechanism that is able to change overall


Explain the role of population size in genetic drift.

the smaller the population the greater the effect


Distinguish between the bottleneck effect and the founder effect. Know examples of each.

a small population created from a larger pop tristian da cuda out of the 15 on had retinitis

bottleneck killing off of a great number of the population for example the prarie chicken


Distinguish among directional, disruptive, and stabilizing selection. Give an example of each mode of selection.

Directional selection on extreme of a phenotypic range is favored red flowers favored by polinators so more red produce offspring
disruptive phenotypes are favored two polinators
stabalizing Intermediate phenotype is favored
and color range is smaller


Explain how diploidy can protect a rare recessive allele from elimination by natural selection.

recessive allele forms are hidden and not expressed so they are saved but not used so they are not killed off. heterozygocity is the reason.


Describe how heterozygote advantage and frequency-dependent selection promote balanced polymorphism.

heterozygote allows for each gene type to be expressed but extrememes are not favored and frequency depennds on how much of the population has a trait so if you have lil of both you are more likely to survive so as the cycle continues there is an equal amount of occurance


Define neutral variations. Explain why natural selection does not act on these alleles.

Nucleotide differences in noncoding sequences confer no advantage or disadvantage

they are non encoding so natural selection doesnt effect the frecuency of the alleles


Distinguish between intrasexual selection and intersexual selection.

intersexual one mate is picky of the other mate while intrasexual is fighting within the same sex


Explain how female preferences for showy male traits may benefit the female.

Good gene hypothesis female slects male and off spring reproduce
healthy gene hypothesis females prefer eleborate ornamaentation indicatiing good health and no pathogens and parasites because excess energy can be used on brigther colors


Explain how the genetic variation promoted by sex may be advantageous to individuals on a generational time scale.

the more advantageous one generation s those traits will be passed on and other preserved when needed.


List four reasons why natural selection cannot produce perfect organisms.

Selection can act on only existing variations
Evolution is limited to historical constraints
Adaptations are often compromises
Chance, natural selection, and environment interact


Define relative fitness.
a. Explain why relative fitness is zero for a healthy, long-lived, sterile organism.
b. Explain why relative fitness could be high for a short-lived organism

realative fittness is based on an individuals capacity to reproduce
a short lived organisim might have greatly contributed to the gene pool