BIO: Chapter 12 Forces of Evolutionary Change

over many generations, a populations characteristics can change by natural selection, even giving rise to new speices

descent with modification

what are two ways to define evolution?

one way to define evolution is decent with modification. a second definition takes a population genetics perspective: Evolution is a change in alleles frequencies in a population over time

How do we define natural selection?

process through which populations of living organisms adapt and change.

why does natural selection drive adults rather than embryos?

what does common descent with modification mean?

the idea that species change over time, give rise to new species, and share a common ancestor. The mechanism that Darwin proposed for evolution is natural selection.

Why can't evolution act on individuals?

allele frequencies are a property of a population, not an individual; an individual's alleles do not change within a lifetime. the only way evolution can occur is if allele frequencies in a population change from generation to generation

explain how Malthus's work contributed to Darwin's views

Malthus' work made Darwin realize the importance of overpopulation and how it was necessary to have variability in different populations.

What information could be drawn from Cuvier's work?

Cuvier established proof that many species like dinosaurs had become extinct in ages past. Cuvier proposed that after each series of catastrophes new species had been created. Cuvier's work on extinctions was incorporated into Darwin's theory of natural selection and survival of the fittest.

Why is life not a series according to Von Baer?

animal embryos started from one, or a few, shared basic forms and then developed in a branching pattern into increasingly different looking organisms. NOT DONE

How did Lyell's geologic studies support natural selection?

what did Darwin observe that led him to develop his ideas about the origin of species?

as Darwin journeyed in the HMS beagle, he observed geological processes such as volcanism, earthquakes, and erosion. He collected fossils and living specimens, and he noted their locations an unique characteristics. he also read malthus arguments about populations, and he understood how selective breeding could produce new varieties of domesticated plants and animals. Darwin combined these observations to develop the idea of descent with modification

How might artificial selection and natural selection produce the same result? Which process would be faster? Why?

in artificial selection, a human chooses which individuals get to breed, in an effort to select for one or more desirable traits.

in natural selection, the environment might select for the same traits, provided that those traits promote reproductive success.

artificial selection would probably be faster because the breeder can select only those individuals that come closest to the 'ideal' and prevent all other individuals from reproducing in each generation. natural selection would be less efficient

what is the modern evolutionary?

the modern evolutionary synthesis combines the idea of natural selection with a modern understanding of genes, chromosomes, and the origins of variation

what is an adaption, and how do adaptions become more common within a population?

an adaption is heritable characteristic that helps an individual survive and reproduce in its environment. the adaption becomes more common within a population when individuals with the adaption have enhanced reproductive success, contributing a greater proportion of their alleles to the next generation than individuals without the adaption

an organisms contribution to the next generation's gene pool

fitness

number of individuals of one genotype, divided by the number of individuals in the population

genotype frequencies

The situation in which allele frequencies in the gene pool of a population remain constant is called

Hardy-Weinberg equilibrium

form of natural selection in which one extreme phenotype is fittest, and the environment selects against the others

direction selection

form of natural selection in which the two extreme phenotypes are fittest

disruptive selection

form of natural selection in which extreme phenotypes are less fit than the optimal intermediate phenotype

stabilizing selection

difference in appearance between males and females

sexual dismorphism

type of natural selection resulting from variation in the ability to obtain mates

sexual selection

change in allele frequencies that occur purely by chance; includes the founder and bottleneck effects

genetic drift

genetic drift that occurs when a small, non-representative group of individuals leaves their ancestral population and begins a new settlement

founder effect

sudden reduction in size of population

bottleneck

choosing mates based on location, physical traits, or other factors

nonrandom mating

how can natural selection favor different phenotypes at different times?

natural selection can favor different phenotypes at different times because environments and selective forces are always shifting

what is 'fitness' in the context of evolution?

fitness is an organisms contribution to the gene pool in the next generation. the more offspring an individual produces, the more fir the individual is.

what five conditions are required for handy-weinberg equilibrium?

the five conditions required for Hardy-Weinberg equilibrium:

1 natural selection does not occur

2 mutations do not occur

3 the population is large enough to eliminate random changes in allele frequencies

4 mating is completely random

5 no individuals migrate into or out of the population

Why doesn't Hardy-Weinberg equilibrium occur in real populations?

in real populations, at least one of the requirements for Hardy-Weinberg equilibrium is always violated. for example, both mutations and natural selection are inevitable

distinguish among directional, disruptive, and stabilizing selection.

directional selections selects against phenotypes at one end of the variation spectrum in a population. in disruptive selection, extreme phenotype are more fit than the intermediate phenotype; the frequency of the intermediate phenotype therefore decreases in the population. in stabilizing selection, both extreme variations of phenotype are selected against; intermediate phenotypes are most common

how can natural selection maintain harmful alleles in a population?

if a harmful allele is recessive, and if heterozygotes carrying the recessive allele have a reproductive advantage over homozygous individuals, then natural selection may maintain a balanced polymorphism. in that case, both the dominant and recessive allele are maintained indefinitely, even if individuals who are homozygous recessive for the harmful allele are at a severe disadvantage

how does sexual selection promote traits that decrease survival?

sexual selection selects for extreme phenotypes in one sex, and those extreme variations often place the individual at a disadvantage for survival. However, since these traits increase fitness by increasing mating success, they are maintained in the population

describe two ways in which competition for access to mates can lead to sexual selection

members of one sex may fight each other for the "right" to mate; in this case, female mate choice plays no role in sexual selection. alternatively, members of one sex may choose among potential mates that compete for femlae attention

how do mutations affect an organisms phenotype?

mutations introduce new alleles, which may or may not alter the phenotype of an organism. the new phenotype may reduce reproductive success, have no effect, or promote reproductive success

south china tigers once had two color patters (orange/black and blue/gray), which did not affect an individuals reproductive success. over many decades, the tiger population has drastically declined, and all blue/gray individuals have disappeared. what evolutionary process eliminated this color pattern?

because color pattern did not affect reproductive success, we can rule out natural selection. genetic drift is therefore the most likely explanation. the overall tiger population rapidly declined, and by chance the blue/gray color pattern disappeared

what is the difference between the founder effect and a population bottleneck?

in the founder effect, a new population is started by a small group of individuals that colonize a new area. in a population bottleneck, a large and genetically variable population experiences a massive die-off, and only a few individuals survive to continue the population. in either case, a small population contains a random, nonrepresentative subset of the alleles present in the original, larger population

how do nonrandom mating and migration result in evolutionary change?

nonrandom mating means that not all individuals have an equal chance of reproducing; as a result, some allele combinations will become more frequent than others in subsequent generations. migration causes alleles to enter or leave the population, altering the allele frequencies.

interbreeding members of the same species

A. allele frequency

B. microevolution

C. popultion

D. Gene

C

a population's entire collection of genes and alleles

A. gene pool

B. microevolution

C. macroevolution

D. population

A

the number of copies of an allele, divided by the total number of alleles for the same gene in the population

A. allele frequency

B. gene pool

C. microevolution

D. macroevolution

A

small, generation-by-generation changes to a populations gene pool

A. macroevolution

B. population

C. allele frequency

D. microevolution

D

Large-scale evolutionary events, such as the appearance of new species

A. microevolution

B. allele frequency

C. macroevolution

D. population

C

artificial selection

Humans modifying species for desired traits through selective breeding.

observations of nature

genetic variation,

limited resources, overproduction of offspring

within a species, no two individuals are exactly alike. some of this variation is inheritable

genetic variation

every habitat contains limited supplies of the resources required for survival

limited resources

more individuals are born than survive to reproduce

Overproduction of offspring

Inferences from observations

struggle for existence

unequal reproductive success (natural selection)

decent with modification

individuals compete for the limited resources that enable them to survive

struggle to existence

the inherited characteristics of some individuals make them more likely to obtain resources, survive, and reproduce

unequal reproductive success (Natural selection)