Zoo Evolution and Natural Selection
Gradual evolutionary change explains why organisms are well-suited to their environments.
For which one of the following observations were both Lamarck's hypothesis and Darwin's hypothesis in complete agreement?
older strata carry fossils that differ greatly from living organisms
Fossils found in strata reveal that ________.
organisms had adapted to new environments, giving rise to new species (Darwin reasoned that natural selection had increased the match between the organisms and their environment.)
From his observations of organisms in the Galapagos islands, Darwin reasoned that _____.
microevolution
Generation-to-generation change in the allele frequencies in a population is _____.
chance events cause allele frequencies to fluctuate unpredictably
Genetic drift produces variation for evolution when ________.
Genetic Drift Genetic drift can lead to a loss of genetic variation within populations and is therefore not a source of genetic variation.
One of the following is NOT a source of genetic variation. *alteration of gene number or position *mutation *sexual reproduction *rapid reproduction *genetic drift
homology
Structures as different as human arms, bat wings, and dolphin flippers contain many of the same bones, which develop from similar embryonic tissues. These structural similarities are an example of _____.
Triazine-resistant weeds were more likely to survive and reproduce.
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 statements explains why the pigweed reappeared? *Triazine-resistant pigweed has less-efficient photosynthesis metabolism. *Natural selection caused the pigweed to mutate, creating a new triazine-resistant species. *Triazine-resistant weeds were more likely to survive and reproduce. *The herbicide company lost its triazine formula and started selling poor-quality triazine.
The proportion of mottled fish will increase over time. (The mottled fish will tend to escape predation because they are camouflaged against the mottled lake bottom. The mottled fish will most likely produce more offspring.)
A group of small fish live in a lake with a uniformly light-brown sandy bottom. Most of the fish are light brown, but about 10% are mottled. This fish species is often prey for large birds that live on the shore. A construction company dumps a load of gravel in the bottom of the lake, giving it a mottled appearance. Which of these statements presents the most accurate prediction of what will happen to this fish population? *in two generations, all the fish will be mottled. *As the mottled fish are eaten, more will be produced to fill the gap. *There is no way to predict the result. *The ratios will not change. *The proportion of mottled fish will increase over time.
a genetic bottleneck
An earthquake decimates a ground-squirrel population, killing 98% of the squirrels. The surviving population happens to have broader stripes, on average, than the initial population. If broadness of stripes is genetically determined, what effect has the ground-squirrel population experienced during the earthquake?
None of the insect pests would have genetic variations that resulted in DDT resistance.
DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Instead, DDT is largely useless against many insects. Which of these would have prevented this evolution of DDT resistance in insect pests?
dismissed the idea that species are constant and emphasized the importance of variation and change in populations
Darwin and Wallace's theory of evolution by natural selection was revolutionary because it _____.
evolution of the unity and diversity of life
Darwin used the phrase "descent with modification" to explain ________.
No, drug-susceptible cells and drug-resistant cells are equally likely to infect a new host. (A cell's drug susceptibility or resistance does not affect its ability to infect another host, although a cell's drug resistance would increase that cell's chances to spread in an environment containing antibiotics due to increased survival.)
Does the ability of a Mycobacterium tuberculosis cell to infect a new host depend on its drug-resistant phenotype?
"tinkering" with existing structures
Evolution works by _____.
increasing sickle-cell allele frequency
Homozygotes with two sickle-cell alleles are selected against because of mortality. However, heterozygotes for sickle-cell allele experience little effects of sickle allele and are more likely to survive malaria. The net effect of this exposure produced evolutionary change in areas where malaria is endemic by ________.
*Milk is protein and fat-rich and therefore could have been an important, high-quality food source. *Milk may have been a critical food source during times of famine. *Milk was safer to drink than water and reduced exposure to pathogens.
How could milk-drinking have provided strong favorable selection for lactase persistence?
A lactase-persistent person is lactose tolerant. A "lactase-persistent" adult continues to make the enzyme lactase and is able to digest (and tolerate) lactose.
How does the term "lactase persistent" relate to the term "lactose tolerant"?
1)Individuals in a population vary in the traits they possess. 2)Some trait differences are heritable. 3)Survival and reproductive success are variable among individuals in a population. 4)Individuals with certain traits are more likely to survive and reproduce.
Identify the four postulates of natural selection. (Darwin)
a founder effect
In 1983, a population of dark-eyed junco birds became established on the campus of the University of California, San Diego (UCSD), which is located many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains. Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays. Males with more white in their tail are more likely to win aggressive interactions, and females prefer to mate with males with more white in their tails. Females have less white in their tails than do males, and display it less often. (Pamela J. Yeh. 2004. Rapid evolution of a sexually selected trait following population establishment in a novel habitat. Evolution 58[1]:166-74.) The UCSD campus male junco population tails were, on average, 36% white, whereas the tails of males from nearby mountain populations averaged 40-45% white. If this observed trait difference were due to a difference in the original colonizing population, it would most likely be due to ________.
"tinkering" with existing structures (Evolution, and in particular natural selection, can only select for the best available traits. Modifications to those traits are usually made in small, incremental steps, and new inventions are rare.)
In a hypothetical environment, fishes called pike-cichlids are visual predators of large, adult algae-eating fish (in other words, they locate their prey by sight). The population of algae-eaters experiences predatory pressure from pike-cichlids. Which of the following is least likely to result in the algae-eater population in future generations? *predicting the future *"tinkering" with existing structures *constantly increasing complexity *converging on a particular phenotype *molding the environment to conform to the organisms living in it
The corn borer must have or generate (by mutation) heritable variation in resistance to the toxic protein. The resistant corn borers must survive better or reproduce more than nonresistant corn borers.
In the United States today, about half of the corn crop is genetically engineered with a protein that is toxic to corn borers, an insect pest of corn. Which of the following conditions would be necessary for evolution of resistance to the toxic protein to occur in the corn borer?
stabilizing selection
Martin Wikelski and L. Michael Romero (Body size, performance and fitness in Galápagos marine iguanas, Integrative and Comparative Biology 43 [2003]:376-86) measured the snout-to-vent (anus) length of Galápagos marine iguanas and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snout-vent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males and females. Examine the figure. What type of selection for body size appears to be occurring in these marine iguanas?
bones in the flipper of a whale
Of the following anatomical structures, which is homologous to the bones in the wing of a bird? *bony rays in the tail fin of a flying fish *bones in the hind limb of a kangaroo *chitinous struts in the wing of a butterfly *bones in the flipper of a whale
Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.
Over long periods of time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?
a few thousand years old, and populations are unchanging
Prior to the work of Lyell and Darwin, the prevailing belief was that Earth is _____.
the founder effect
Soon after the island of Hawaii rose above the sea surface (somewhat less than one million years ago), the evolution of life on this new island should have been most strongly influenced by ________.
a population that raises wheat and sheep (Sheep can provide milk, which has about the same amount of lactose as cow's milk. Therefore, a lactase-persistence mutation could potentially be advantageous in this population.)
Suppose that a mutation for lactase-persistence occurred in each of the populations described below. In which populations would the mutation be more likely to increase in frequency over time because of natural selection? *a population that raises rice and tilapia fish *a population that raises corn and beans *a population that raises potatoes and chickens *a population that raises wheat and sheep
The lactase enzyme breaks the lactose disaccharide into two monosaccharides, glucose and galactose
The enzyme lactase breaks the sugar lactose into which compound(s)?
the population size is small
The evolutionary effects of genetic drift are greatest when _____.
Gene Flow
The migration of individuals or gametes
*it is broad enough in scope to explain many observations *it is supported by a massive body of evidence from many disciplines *it is general enough to provide many testable hypotheses
The theory of evolution through natural selection is considered a scientific theory because _____.
disruptive selection
Three-spined stickleback fish (Gasterosteus aculeatus) show substantial heritable variation in gill-raker length related to differences in their diets. Longer gill rakers appear to function better for capturing open-water prey, while shorter gill rakers function better for capturing shallow-water prey. Which of the following types of selection is most likely to be found in a large lake (open water in the middle and shallow water around the sides) with a high density of these fish?
True (In an environment without antibiotics, individual cells probably would not differ in their reproductive rates or their survival. Without the application of the drug (antibiotic), it would be very difficult to analyze any differences—one wouldn't even be able to sort the cells!)
True or false? It would be difficult to assess whether the drug-susceptible or drug-resistant phenotype in a population of Mycobacterium tuberculosis was more fit in an environment without antibiotics.
It is found in a regulatory region (a "switch") upstream of the lactase gene. (All known mutations giving rise to lactase persistence are in a genetic "switch" that regulates expression of the lactase gene. Mutations in regulatory regions can change the amount of protein that is produced without affecting its structure or function.)
What did researchers discover about the genetic mutation causing lactase persistence?
natural selection (Because natural selection has a "sorting" effect, it consistently increases the frequency of alleles that improve the match between an organism and its environment.)
What is the only evolutionary mechanism that consistently leads to adaptive evolution?
It is the kind of evolution that can change the relative abundance of a particular allele in a gene pool over the course of generations. (Microevolution is a generation-to-generation change in allele frequency.)
What is true of microevolution?
Ancient pots used to hold milk are about the same age as the lactase-persistence mutations. (Evidence of early milk use in lactase-persistent cultures provides evidence for the co-evolution of genes and culture.)
Which discovery supports the hypothesis that evolution of the lactase-persistence trait was driven by the use of milk in pastoralist cultures?
Characteristics acquired during an organism's life are generally not passed on through genes.
Which of the following statements best explains why modification or change in an organ or tissue during the lifetime of an individual is not inherited? *Characteristics acquired during an organism's life are generally not passed on through genes. *Only favorable adaptations have survival value. *Spontaneous mutations can result in the appearance of new traits. *Disuse of an organ may lead to its eventual disappearance.
The drug-resistance trait is an adaptation to the environment in which human hosts are medicated with the antibiotic rifampin.
Which of the following statements describes the evolution by natural selection of Mycobacterium tuberculosis bacteria in their new environment?
Heritable variation exists for traits among individuals in a population.
Which of the following statements is an accurate combination of postulates 1 and 2 of natural selection?
Individuals experience differential success in their ability to survive or reproduce due to differences in certain traits. (Variation in fitness is required for selection to change the characteristics of a population over time. Remember that selection also requires that the variation in fitness be related to a heritable trait.)
Which of the following statements is an accurate combination of postulates 3 and 4 of natural selection?
Conditions 1 and 2
Which of these conditions are always true of populations evolving due to natural selection? Condition 1: The population must vary in traits that are heritable. Condition 2: Some heritable traits must increase reproductive success. Condition 3: Individuals pass on most traits that they acquire during their lifetime.
sudden change in environments that alters gene frequency of a population
Which one of these processes describes bottleneck effect? *chance events that change allele frequency *transfer of alleles in and out of a population due to movement of fertile individuals *sudden change in environments that alters gene frequency of a population *alleles transferred to the next generation in portions that differ from previous generation
Individuals with inherited traits that promote survival tend to have more surviving offspring.
Which statement illustrates the connection between natural selection and overreproduction of a population?