Scientific Theories

are supported by, and make sense of, many observations

The increase in oxygen that occurred over the early history of the earth was largely due to

photosynthesis in prokaryotes

The lack of hybrids of Drosophila mojavensis and Drosophila arizonae in the Sonoran desert where they are sympatric is an example of

reinforcement

Which kind of DNA should provide the best molecular clock for determining the evolutionary relatedness of several species whose common ancestor became extinct billions of years ago?

that coding for ribosomal RNA

Current scientific evidence suggests that the first genes on Earth were

RNA molecules with catalytic properties

Which of the following is the most predictable outcome of increased gene flow between two populations?

decreased genetic difference between the two populations

Rocky mountain juniper (Juniperus scopulorum) and one-seeded juniper (J. monosperma) have overlapping ranges. Pollen grains (which contain sperm cells) from one species are unable to germinate and make pollen tubes on female ovules (which contain egg cells) of the other species. These two juniper species are kept separate by

gametic isolation

New morphological forms can come from changes in developmental genes via

sequence evolution, gene duplication, and changes in expression. (all of the above)

What most strongly supports the common origin of all life on Earth?

all organisms use essentially the same genetic code

Genetic drift

can cause deleterious alleles to become fixed, leads to loss of variation, and is most significant in small populations

Which domain includes members that are the result of endosymbioses that included an ancient aerobic proteobacterium, an ancient photosynthetic cyanobacterium, or both?

Eukarya

Developmental genes

control the rate, timing, and spacial patterning of an organism's development

A population of organisms will not evolve if

all individual variation is due only to environmental factors

Correct sequence of events in the origin of life

1) synthesis of organic monomers
2) synthesis of organic polymers
3) formation of protocells
4) origin of self-replicating molecules

Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating

stabilizing selection

Lack of mating due to species occupying different habitats is an example of what type of isolating mechanism?

habitat isolation

The event in which roughly 96% of all marine species went extinct is known as

Permian Extinction

What a good example of homologous structures?

bones in the bat wing and bones in the human forelimb

If differences in courtship rituals exist that prevent mating, this would be an example of

behavioral isolation

Darwin and Wallace's theory of evolution by natural selection was revolutionary because it

dismissed the idea that species are constant and emphasized the importance of variation and change in populations

The most important feature that permits a gene to act as a molecular clock is

a reliable average rate of mutation

For which species concept would differences at the genetic level define the species?

phylogenetic

The earliest fossil of a eukaryote dates back to

2.1 billion years ago

One of the main conclusions of the Mimulus (monkeyflower) studies discussed in class was

a few genes of large effect, such as flower color, could be directly involved in the isolation of populations

Reinforcement is most likely to occur when

hybrids have lower fitness than either parent population

Adaptive radiation can be a direct consequence of four of the following factors. Select the exception

genetic drift

Theoretically, the production of sterile mules by interbreeding between female horses (mares) and male donkeys (jacks) should

strengthen postzygotic barriers between horses and donkeys

Which of the following is not an assumption necessary for the Hardy-Weinberg equilibrium to be met?

Selection occuring

Must be present in a population before natural selection can act upon the population

genetic variation

Which statement about the beak size of finches on the island of Daphne Major during the prolonged drought:

each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted

The presence of the sickle cell anemia allele in certain human populations is an example of

heterozygote advantage

In a comparison of only birds and mammals, having four limbs is

a shared ancestral character

The loss of ventral spines by modern freshwater sticklebacks is due to natural selection operating on the phenotypic effects of the Pitx1 gene

silencing (loss of expression)

Many crustaceans use their tails to swim, but crabs have reduced tails that curl under their shells and are not used in swimming. This is an example of

a vestigial trait

Which of the following represents an idea that Darwin learned from the writings of Thomas Malthus?

populations tend to increase at a faster rate than tier food supply normally allows

The event in which the great majority of dinosaurs went extinct is known as

Cretaceous extinction

The following are all true statements about the endosymbiont theory except:

Mitochondria are a result of an aerobic eukaryotic cell engulfing a anaerobic prokaryotic cell

The earliest fossil of a prokaryote dates back to

~3.5 billion years ago

Which statement about mutations is false.

all mutations affect the phenotype

Fossilized stromatolites

resemble structures formed by bacterial communities that are found today in some warm, shallow, salty bays

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of allele a is 0.1. What is the frequency of individuals with AA genotype?

A=0.9
AA=(0.9)(0.9)=0.81

The most likely explanation for the high rate of sympatric speciation that apparently existed among the cichlids of Lake Victoria in the past is

sexual selection

Which of the following is not a true statement about evolution?

On occasion, some individuals evolve

What does the biological species concept use as the primary criterion for determining species boundaries?

gene flow

What, if it had acted upon a gene, would prevent this gene from acting as a reliable molecular clock?

natural selection

During an individual organism's lifetime, what is most likely to help the organism respond properly to changes in its environment?

change in gene expression

What was derived form an ancestral cyanobacterium?

chloroplast

What is a possible fate of a hybrid zone?

1) shrinking and eventually disappearing
2) persistence over some time
3) fusion of the two species into one

A phylogenetic tree constructed using sequence differences in mitochondrial DNA would be most valid for discerning the evolutionary relatedness of

chimpanzees and humans

In which type of isolating mechanisms do we see the formation of sterile hybrids?

reduced hybrid fertility

Two species of frogs belonging to the same genus occasionally mate, but the embryos stop developing after a day and then die. These two frog species separate by

reduced hybrid viability

Most causes of speciation are relatively slow, in that they make take many generations to see changes, with the exception of

polyploidy

Some beetles and flies have antler-like structures on their heads, much like male deer do. The existence of antlers in beetle, fly, and deer species with strong male-male competition is an example of

convergent evolution

In modern terminology, diversity is understood to be a result of genetic variation. Which of the following is a recognized source of variation in evolution?

recombination by crossing over in meiosis

Structures as different as human arms, bats wings, and dolphin flippers contain many of the same bones, which develop from similar embryonic tissues. These structural similarities are an example of

homology

Which of these should decline in hybrid zones where reinforcement is occuring?

gene flow between distinct gene pools

In most cases, which relationship should be expected between different populations of a species.

a positive correlation between physical distance and reproductive isolation

If two modern organisms are distantly related in an evolutionary sense, then one should expect that

they should share fewer homologous structures than two more closely related organisms

Which of the conditions would prevent the occurrence of natural selection in a population over time?

All variation between individuals to environmental factors

What type of isolating mechanism involves the production of viable and fertile hybrids that have reduced or no mating success?

Hybrid breakdown

The beak of the ground finch in the Galapagos islands have increased in depth as a function of changes in the seeds avaliable (increases in the seed hardness). This is an example of

Directional selection

Which of the following statements regarding developmental genes is true?

they control the rate, time and spatial patterning of an organism's development

The evolution of reproductive incompatibilities between two populations could be caused by

all of the above

The higher the proportion of loci that are "fixed" in a population, the lower is that population's

nucleotide variability and average heterozygosity only.

All of the following are true about genetic drift except

is not considered evolution

Neutral theory proposed that

a significant proportion of mutations are not acted upon by natural selection

The scientific contributions of Jean-Baptiste de Lamarck include all of the following except

Binomial system of naming species

Which of the various species concepts distinguishes two species on the degree of genetic exchange between their gene pools

biological

A farmer uses triazine herbicide to control pigweed in his field. For the first few years, the triazine works well and almost all the pigweed dies; but after several years, the farmer sees more and more pigweed. Which of these best explains what happened?

triazine-resistant weeds were more likely to survive and reproduce