Guided course 02:53Directional, Stabilizing, and Disruptive SelecitonJason Amores Sumpter2366views25rank2comments
10:47Genetic drift, bottleneck effect and founder effect | Biology | Khan AcademyKhan Academy491views
03:03Natural Selection animation (stabilizing, disruptive and directional selection)Shomu's Biology931views
08:29Natural Selection & Sexual Selection: An Illustrated IntroductionCornell Lab of Ornithology360views
01:42The Evolution of Populations: Natural Selection, Genetic Drift, and Gene FlowProfessor Dave Explains486views
01:27Mechanisms of Natural Selection Part 1: Types of Sexual SelectionProfessor Dave Explains320views
Multiple ChoiceThe human genome consists of approximately 3 billion base pairs. If humans typically differ from one another by about 3 million base pairs, what is the nucleotide variability of Homo sapiens? 888views
Multiple ChoiceSexual recombination includes the shuffling of chromosomes in __________ and fertilization. 354views
Multiple ChoiceWhich type of mutation plays the most important role in increasing the number of genes in the gene pool? 638views
Multiple ChoiceWhich of the following would seem to be an example of neutral variation? 372views1rank
Multiple Choice__________ and __________ generate variation, whereas __________ results in an adaptation to the environment. 415views
Multiple ChoiceA population of 15 birds inhabits a fairly new island. Ten of the birds are dark brown, and five of them are light brown. By chance, two of the dark brown birds and three of the light brown birds die before producing any offspring. All of the birds in the next generation are dark brown. This change in phenotypic frequency can be attributed to __________. 390views
Multiple ChoiceAn earthquake hits a small island. All but a small group of closely related lizards are eliminated, and the survivors spread out over the island. This is an instance of __________. 403views
Multiple ChoiceWhich of the following scenarios would most likely result in the microevolution of a population of humans? 525views
Multiple ChoiceThe lethal genetic disorder Tay-Sachs disease occurs in individuals with two copies of a recessive allele of the responsible gene. Which of the following statements is true? 709views
Multiple ChoiceFor several years, scientists have warned doctors of the danger of overprescribing antibiotics such as penicillin. Scientists are concerned because __________. 662views1rank
Multiple ChoiceA population of squirrels is preyed on by small hawks. The smaller squirrels can escape into burrows. The larger squirrels can fight off the hawks. After several generations, the squirrels in the area tend to be very small or very large. What process is responsible for this outcome? 807views
Multiple ChoiceBirds with average-size wings survived a severe storm more successfully than other birds in the same population with longer or shorter wings. If severe storms occur regularly, then over time, one should expect these storms to bring about __________. 645views
Multiple ChoiceWhich type of selection maintains stable frequencies of two or more phenotypic forms in a population? 436views
Multiple ChoiceSelection that acts over evolutionary time to preserve traits that increase an individual's ability to mate is known as __________. 429views
Multiple ChoiceA number of mosquito populations today are resistant to insecticides that were once quite effective. Biologists think that insecticide resistance evolved in mosquitoes because __________. 573views
Textbook QuestionNatural selection changes allele frequencies because some _________ survive and reproduce better than others. a. alleles b. loci c. species d. individuals1057views
Textbook QuestionThe largest unit within which gene flow can readily occur is a a. population. b. species. c. genus. d. hybrid.672viewsHas a video solution.
Textbook QuestionHow do the phospholipids in archaea differ from those in other cells? a. They have tails made of unsaturated fatty acids instead of saturated fatty acids. b. They do not contain hydrocarbon chains. c. They have isoprenoid tails instead of fatty acid tails. d. They have two hydrocarbon chains instead of three hydrocarbon chains.753viewsHas a video solution.
Textbook QuestionWhat two functional groups are bound to the central carbon of every free amino acid monomer? a. an R-group and a hydroxyl group b. an N—H group and a ═(C═O) group c. an amino group and a hydroxyl group d. an amino group and a carboxyl group911viewsHas a video solution.
Textbook QuestionNo two people are genetically identical, except for identical twins. The main source of genetic variation among humans is a. new mutations that occurred in the preceding generation. b. genetic drift. c. the reshuffling of alleles in sexual reproduction. d. environmental effects.1360viewsHas a video solution.
Textbook QuestionWhy isn't inbreeding considered an evolutionary process? a. It does not change genotype frequencies. b. It does not change allele frequencies. c. It does not occur often enough to be important in evolution. d. It does not violate the assumptions of the Hardy–Weinberg principle.397viewsHas a video solution.
Textbook QuestionDescribe three ways that evolution can occur via genetic drift.809viewsHas a video solution.
Textbook QuestionWhy is genetic drift aptly named? Select True or False for each statement. T/F It causes allele frequencies to drift up or down randomly. T/F It occurs when alleles from one population drift into another. T/F It occurs when mutations drift into a genome.484viewsHas a video solution.
Textbook QuestionWhich of these functional groups is known to be used for storing large amounts of chemical energy? a. amino group b. carbonyl group c. phosphate group d. sulfhydryl group675viewsHas a video solution.
Textbook QuestionEvaluate the following statements related to the synthesis of nucleic acids. Select True or False for each statement. T/F Ribonucleotides are added to the 3′ end of a DNA strand. T/F Polymerization of nucleic acids occurs by the formation of phosphodiester bonds. T/F Complementary pairing between sugars is required for copying nucleic acids. T/F Strands in a double helix are synthesized in an antiparallel orientation.739viewsHas a video solution.
Textbook QuestionEvaluate this statement: Gene flow increases the genetic divergence of populations.401viewsHas a video solution.
Textbook QuestionTrue or false? Gene flow can either increase or decrease the average fitness of a population. Explain.738views
Textbook QuestionAdd labels to the figure that follows, which illustrates how Mycobacterium tuberculosis evolves when it is exposed to an antibiotic. 220viewsHas a video solution.
Textbook QuestionWhat is responsible for the increased stability of DNA compared to RNA?885viewsHas a video solution.
Textbook QuestionCooking oil lipids consist of long, unsaturated hydrocarbon chains. Would you expect these molecules to form membranes spontaneously? Why or why not? Describe, on a molecular level, how you would expect these lipids to behave in water.894viewsHas a video solution.
Textbook QuestionIn an area of erratic rainfall, a biologist found that grass plants with alleles for curled leaves reproduced better in dry years, and plants with alleles for flat leaves reproduced better in wet years. This situation would tend to _________ . (Explain your answer.) a. cause genetic drift in the grass population. b. preserve genetic variation in the grass population. c. lead to stabilizing selection in the grass population. d. lead to uniformity in the grass population.327viewsHas a video solution.
Textbook QuestionIf nucleotides from the DNA of a human were quantified and 30 percent of them contained the base adenine, what percentage of them would contain the base guanine? a. 20 percent b. 30 percent c. 40 percent d. 70 percent670viewsHas a video solution.
Textbook QuestionIf an allele is recessive and lethal in homozygotes before they reproduce, a. the allele will be removed from the population by natural selection in approximately 1,000 years. b. the allele will likely remain in the population at a low frequency because it cannot be selected against in heterozygotes. c. the fitness of the homozygous recessive genotype is 0. d. both b and c are correct.1034viewsHas a video solution.
Textbook QuestionIn the 1700s and 1800s, royalty in Europe often married their close relatives; furthermore, recessive genetic diseases such as hemophilia showed up much more often among royals than in the general population. Explain the likely connection.269viewsHas a video solution.
Textbook QuestionExplain why continuous growth enhances the phenomenon known as phenotypic plasticity.260viewsHas a video solution.
Textbook QuestionThe heritable differences among organisms are a result of . a. differences in their DNA; b. mutation; c. differences in alleles; d. A and B are correct; e. A, B, and C are correct509viewsHas a video solution.
Textbook QuestionAccording to the RNA world model, a ribozyme would replicate by creating a double-stranded RNA intermediate. Would you expect the intermediate to have the same catalytic activity as the original ribozyme? Justify your answer with an explanation.678viewsHas a video solution.
Textbook QuestionA new plant species C, which formed from hybridization of species A(2n = 16) with species B(2n = 12), would probably produce gametes with a chromosome number of a. 12. b. 14. c. 16. d. 28.351viewsHas a video solution.
Textbook QuestionDraw a small concept map showing how selection, genetic drift, gene flow, and mutation relate to genetic variation.432viewsHas a video solution.
Textbook QuestionThe risks faced by small populations include . a. erosion of genetic variability through genetic drift; b. decreased fitness of individuals as a result of inbreeding; c. increased risk of experiencing natural disasters; d. A and B are correct; e. A, B, and C are correct359viewsHas a video solution.
Textbook QuestionIvory from elephant tusks is a valuable commodity on the world market. As a result, male African elephants with large tusks have been heavily hunted for the past few centuries. Today, male elephants have significantly shorter tusks at full adulthood than male elephants in the early 1900s. This is an example of . a. diversifying selection; b. stabilizing selection; c. directional selection; d. chance; e. more than one of the above is correct535viewsHas a video solution.
Textbook QuestionA horse (2n = 64) and a donkey (2n = 62) can mate and produce a mule. How many chromosomes would there be in a mule's body cells? a. 31 b. 62 c. 63 d. 126433viewsHas a video solution.
Textbook QuestionAntibiotic resistance is becoming common among organisms that cause a variety of human diseases. All of the following strategies help reduce the risk of antibiotic resistance evolving in a susceptible bacterial population except . a. using antibiotics only when appropriate, for bacterial infections that are not clearing up naturally; b. using the drugs as directed, taking all the antibiotic over the course of days prescribed; c. using more than one antibiotic at a time for difficult-to-treat organisms; d. preventing natural selection by reducing the amount of evolution the organisms can perform; e. reducing the use of antibiotics in non–health-care settings, such as agriculture508viewsHas a video solution.
Textbook QuestionSuppose you were studying several species of monkeys. In one, males never helped females raise offspring. In another, males provided just as much parental care as females except for actually carrying the fetus during pregnancy. How does the fundamental asymmetry of sex compare in the two species? How would you expect sexual dimorphism to compare between the two species?313viewsHas a video solution.
Textbook QuestionHuman activities are causing the fragmentation of the Brazilian Atlantic rain forest. One result is that toucans have become extinct or nearly extinct in some of the forest fragments. Does the absence of toucans affect the forest? Toucans disperse seeds of key forest species such as juçara palms by eating the fruit and defecating the seeds in new locations, sometimes more than a kilometer away. If there are no toucans, is the genetic diversity of palms likely to increase or decrease within forest fragments? Why? a. increase (due to increased genetic drift) b. decrease (due to decreased gene flow) c. decrease (due to decreased mutation rate) d. decrease (due to decreased natural selection)295viewsHas a video solution.
Textbook QuestionHuman activities are causing the fragmentation of the Brazilian Atlantic rain forest. One result is that toucans have become extinct or nearly extinct in some of the forest fragments. Does the absence of toucans affect the forest? Toucans can eat fruits with large seeds because their large bills can open wide. Most other birds in the same forest can only eat small seeds. Ecologist Mauro Galetti and his colleagues measured the seed sizes of palms in forest fragments with and without toucans. The graphs show two of the forest populations they studied. What is the take-home message of the data? 225viewsHas a video solution.
Textbook QuestionIt seems logical that natural selection would work toward genetic uniformity; the genotypes that are most fit produce the most offspring, increasing the frequency of adaptive alleles and eliminating less adaptive alleles. Yet there remains a great deal of genetic variation within populations. Describe factors that contribute to this variation.434viewsHas a video solution.
Textbook QuestionBotanists are looking for the wild ancestors of potatoes, corn, and wheat. Why is this search important?310viewsHas a video solution.
Textbook QuestionSCIENTIFIC THINKING In Module 31.1, several lines of investigation are used to investigate the time and location of the domestication of important crops. Which line of evidence do you consider the most reliable? Why?269viewsHas a video solution.