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Northern elephant seals were hunted by humans in the 1890s, reducing their population size to 20 individuals. Even though their population is now over 30,000, the seals still have reduced genetic variation. What’s the best explanation of this phenomenon?
Question 1 Explanation:
the correct answer is (A). A severe drop in population size can cause a bottleneck effect. In this case, certain alleles were overrepresented in the population of survivors, and other alleles were underrepresented.
Certain cavefish and salamanders have non-functional eyes, which are remnants of the functional eyes of their ancestors. Such examples of “leftover” structures are referred to as:
Question 2 Explanation:
The correct answer is (C). Vestigial structures are of little, if any, importance to the fitness of the organism. They are historical remnants of structures that promoted fitness in their ancestors.
Which scientists tested the hypothesis that Earth’s early atmosphere was a reducing environment in which organic compounds could have formed from simple molecules?
Oparin and Haldane
Miller and Urey
Cech and Altman
Conway and Morris
Question 3 Explanation:
The correct answer is (B). In 1953, Miller and Urey, of the University of Chicago, tested the Oparin-Haldane hypothesis by creating laboratory conditions similar to those that the scientists at the time thought existed on early Earth.
What is the phenomenon that explains the sudden appearance of many phyla of living animals in the fossil record, between 535–525 million years ago?
Permian Mass Extinction
Question 4 Explanation:
The correct answer is (A). The Cambrian explosion is the period of time occurring 535–525 million years ago in which large, hard-bodied forms of animals with most of the major body plans known today appeared in the fossil record.
The first cells on Earth were likely to be:
Question 5 Explanation:
The correct answer is (D). None of the other choices are “cells.” It is likely that the first cells were anaerobic heterotrophic prokaryotes that obtained nutrients by absorbing organic molecules from the surrounding environment.
Which of the following is not a step in the formation of the first living cells?
The biotic synthesis of small organic molecules
The packaging of molecules into droplets with membranes that maintained an internal chemistry different from their surroundings
The joining of small molecules into macromolecules
The origin of self-replicating molecules that eventually made inheritance possible
Question 6 Explanation:
The correct answer is (A). Since this is asking for the steps leading to the formation of the first living cells, the correct answer would be: “The abiotic synthesis of small organic molecules.”
This is an example of:
Question 7 Explanation:
The correct answer is (C). Heterochrony is an evolutionary change in the rate or timing of developmental events.
Which of the following best describes what happened to the snapping shrimp as evidenced by the aggression observed?
Sympatric speciation brought about by polyploidy
Hybridization caused by geographic isolation
Allopatric speciation caused by geographic isolation
Coevolution brought about by habitat isolation
Question 8 Explanation:
The correct answer is (C). Allopatric speciation occurs when one species is divided into two. The original population is physically separated into two subpopulations and the two groups live in different locations. Over time, the gene pools of the isolated populations continue on their own evolutionary paths. Eventually, the populations are no longer able to interbreed if they ever come together again. This is one of the main processes by which new species arise.
Evolutionary changes in mating rituals, like the differences in bower construction by the bowerbirds, can contribute to which of the following:
Question 9 Explanation:
The correct answer is (B). If two species evolve different mating rituals, it may permanently isolate them from one another and complete the process of speciation.
How would evolutionary biologists classify this type of speciation?
Question 10 Explanation:
The correct answer is (A). Sympatric speciation occurs in populations that live in the same geographic regions.
Western spotted skunks (Spilogale gracilis) breed in the fall, whereas and eastern spotted skunks (Spilogale putorius) breed in late winter. What type of reproductive barrier prevents these species from being classified as the same species?
Question 11 Explanation:
The correct answer is (D). Species that breed during different seasons, times of the day, or different years cannot mix their gametes.
Which of the follow scenarios describes allopatric speciation?
A small segment of the original population is exposed to different environmental conditions, and a new subspecies emerges through natural selection. Over time, a new species is formed without geographic isolation.
A population of species enters a new niche or habitat at the edge of the parent species’ range. There is no physical barrier between the populations, but the occupancy of a new niche becomes a barrier to gene flow between the parent population and the new population.
Rapid and abrupt species formation from genetic drift or chance.
Part of the population becomes geographically isolated from the main population, separating the population into two isolated groups. The populations become two distinct species.
Question 12 Explanation:
The correct answer is (D). Allopatric speciation occurs when gene flow is interrupted because the population has been divided into geographically isolated subpopulations.
This type of speciation occurred due to:
Question 13 Explanation:
The correct answer is (A). Polyploidy is a condition in which a cell is formed that has an extra set(s) of chromosomes.
The “oxygen revolution” had an enormous impact on life, and likely
Provided the proper environment for packaging molecules into “protobionts”
Caused RNA molecules with certain base sequences to become more stable and replicate faster
Caused the extinction of many prokaryotic groups due to the rising concentration of O2
Resulted from the sudden appearance of animals in the Cambrian period
Question 14 Explanation:
The correct answer is (C). In certain chemical forms, oxygen attacks chemical bonds and can inhibit enzymes and damage cells. This rising concentration of O2 probably killed many groups of prokaryotes, except for species surviving in habitats that remained anaerobic.
It is hypothesized that eukaryotic features evolved from prokaryotic cells when smaller prokaryotic cells, the precursors of mitochondria and plastids, began living within larger cells. This model is referred to as:
The Cambrian explosion
Question 15 Explanation:
The correct answer is (A). An endosymbiont is a cell that lives within larger cells. It is believed that prokaryotic ancestors of mitochondria and plastids probably entered the host cell as undigested prey or internal parasites.
In which nutrient cycle does bacteria play a key role in the conversion of an essential organic compound from its atmospheric form to a form usable by organisms?
The water cycle
The carbon cycle
The nitrogen cycle
The phosphorus cycle
Question 16 Explanation:
The correct answer is (C). In the nitrogen cycle, nitrogen-fixing bacteria convert nitrogen gas (N2), which is not usable by plants, to a form that is usable by plants. These nitrogen-fixing bacteria reside in the root nodules of legumes.
Male peacocks are famous for their colorful, showy tails, whereas female peahens are brown with no fancy tails. This is an example of sexual dimorphism, found in organisms with two different looks within the species. What mode of selection produces species exhibiting sexual dimorphism?
Question 17 Explanation:
The correct answer is (C). Sexual selection can lead to the evolution of characteristics, both phenotypic and behavioral, that have an adverse impact on survival but promote fitness.
Thermoregulation involves maintaining an internal body temperature within a tolerable range. Which of the following organisms are considered ectothermic?
Question 18 Explanation:
The correct answer is (C). Snakes gain most of their heat from an outside source, making them ectotherms.
Which types of animals excrete nitrogenous waste in the form of ammonia?
Question 19 Explanation:
The correct answer is (A). Animals that excrete ammonia need access to lots of water because ammonia can only be tolerated at very low concentrations.
Which of the following statements does not describe natural selection:
If a group of organisms relocates to a new environment, or if its current environment changes, the organisms that have a higher fitness in the new environment will leave more offspring and may, over time, give rise to a new species.
Humans have modified many species by selectively breeding individual species to develop new species with specific, desired characteristics.
Individual organisms with certain characteristics are more fit for their environment than organisms without certain characteristics. The organisms with the best suited characteristics for their environment will live to reproduce, and pass those characteristic on to their offspring.
Natural selection can increase the proportion of favorable traits in a population.
Question 20 Explanation:
The correct answer is (B). Choice (B) explains artificial selection, the selective breeding of domesticated organisms to increase the expression of desired traits.
This type of evolutionary fitness is referred to as:
Frequency dependent selection
Question 21 Explanation:
The correct answer is (B). Heterozygote advantage is exhibited in individuals who are heterozygous for a particular trait, and gives the carrier of the trait greater fitness.
Which of the following statements best indentifies the type of selection resulting in the typical reddish brown to grayish brown coat of white-tailed deer?
Question 22 Explanation:
The correct answer is (C). Stabilizing selection removes extreme variants (white coat) from the population and preserves the intermediate phenotypes (reddish brown to grayish brown).
The Mexican population had significantly lower gene diversity, few alleles at each locus, and the gene frequencies were significantly different from populations at other locations. The Mexican population was sampled from a breeding nursery used to screen for resistance to this pathogen. The nursery is located far away from the wheat population area and has a limited potential for influx of natural inoculation, and was inoculated with a limited number of strains of the pathogen. This is an excellent example of:
Question 23 Explanation:
The correct answer is (A). Founder effect occurs when a few individuals have been isolated from a larger population, and thus a smaller group of individuals establishes a new population whose gene pool differs from the source population. In this case, the Mexican population of the speckled leaf spot was isolated from the general population. This presents a clear example of genetic drift due to a small founding population.
In Australia, only a relatively small number of individuals arrived on this continent with the introduction of modern agriculture, and therefore
It is likely that a sudden change in the environment caused a bottleneck effect
Mutations resulting from natural selection have created new pathogens in the original strain
The low gene diversity is consistent with the founder effect
The transfer of alleles into a new population
Question 24 Explanation:
The correct answer is (C). With the introduction of modern agriculture to Australia, a few individuals of the speckled leaf spot were isolated from the larger population, and thus less genetic diversity was present.
The geographic area with the highest level of gene diversity speckled leaf spot is likely to be the center of origin. Based on this data, that area would be
Question 25 Explanation:
The correct answer is (C). Israel has the highest average gene diversity, and is likely to be the center of origin.
This movement of polar bear populations provides a prime example of
Question 26 Explanation:
The correct answer is (A). Gene flow is the movement of allele frequencies into or out of a population due to the movement of fertile individuals and their gametes.
Which of the following was not a large-scale process which influenced major evolutionary changes in life on Earth?
The founder effect
Question 27 Explanation:
The correct answer is (B). The founder effect is genetic drift that occurs when a few individuals from a larger population become isolated and form a new population with a less genetically diverse gene pool than the original population. Adaptive radiation, continental drift and mass extinctions are all major large-scale process that influenced major changes to life on earth.
Evidence from which of the following does not support evolution:
Direct observation of natural selection
Question 28 Explanation:
The correct answer is (D). Analogous structures are similarities that are not attributable to common ancestry.
The fossil record is a significant record of the history of life, but it is an incomplete record of evolutionary change. Many fossils have been destroyed by geologic processes and many are yet to be discovered. As a result, the known fossil record is biased in favor of species with certain characteristics. Which of the following is not a characteristic that would be included in the fossil record?
Species that were abundant
Species with hard shells
Species that existed for short periods of time
Species that were widespread
Question 29 Explanation:
The correct answer is (C). The less time a species exists the less likely it is to become a component of the fossil record.
In animal development, which stage of embryonic development involves the rearrangement of the blastula into a three-layered embryo?
Question 30 Explanation:
The correct answer is (B). Gastrulation takes place when the blastula-stage embryo folds inward (through a series of tissue and cell movement) to create a three-layered embryo, called the gastrula. Cleavage is the first stage, involving the creation of the blastula (hollow ball of cells) through cell division. Organogenesis is the stage during which the three layers of the gastrula form rudimentary organs. Fertilization takes place before embryonic development.
Which group of tissues or organs most likely derived from the ectoderm layer during embryonic development in vertebrates?
Epithelial living of the digestive tract
Circulatory and lymphatic systems
Epithelial lining of the mouth and anus
Thyroid and parathyroid glands
Question 31 Explanation:
The correct answer is (C). The ectoderm is the outer layer of the gastrula and forms. The epithelial lining of the mouth and anus are formed from the ectoderm. The endoderm lines the embryonic digestive tract and the thyroid and parathyroid glands, among other things. The mesoderm partly fills the space between the endo- and ectoderms. The circulatory and lymphatic system arise from the mesoderm, among other tissues and organs.
What is the unique family of genes in animals that plays an important role in the development of embryos, and controls the expression of other genes influencing animal morphology?
α-globin and β-globin
Question 32 Explanation:
The correct answer is (B). Hox genes provide information about the location of tissues and organs during development. FOXPS functions in the vocalization of vertebrates. Mads-box genes are involved in flower development. α-globin and β-globin gene families are components of human hemoglobin.
Which group of organisms share these four key characteristic at some stage of their development: notochord; dorsal, hollow nerve cord; muscular, post-anal tail; and pharyngeal slits?
Question 33 Explanation:
The correct answer is (D). Chordata is the phylum to which vertebrates belong along with the Craniata (such as hagfish), Unichordata (such as tunicates), Cephalochordata (such as lancelets), and, possibly, echinoderms. All chordates have the listed characteristics as defining features. Archaeans are unicellular prokaryotes. Angiosperms are flowering plants, and do not have any of the listed characteristics.
Which of the following is the longitudinal, flexible rod located between the digestive tract and nerve cord in chordates?
Dorsal, hollow nerve cord
Muscular, post-anal tail
Question 34 Explanation:
The correct answer is (A). The notochord is a skeletal structure present at some point in all chordate development. It forms a longitudinal, flexible rod between the digestive tract and the nerve cord. The dorsal, hollow nerve cord forms the central nervous system. The post-anal tail extends beyond the anus in embryonic development. The pharyngeal slits may be modified into gill slits in aquatic organisms or into areas of the ear and structures in the head and neck in tetrapods.
Which group of mammals lays eggs?
Question 35 Explanation:
The correct answer is (B). Monotremes include the platypus and spiny anteaters. They lay eggs. Marsupials are born very early and complete their development while nursing. Examples include opossums, kangaroos and koalas. Eutherinas, or placental mammals, have a long pregnancy and complete their embryonic development in the mother’s uterus. Although monotremes are amniotes, not all amniotes lay eggs.
What theory describes this cost-benefit compromise that favors the behavior that minimizes the costs of feeding and maximizes the benefits?
Optimal foraging model
Question 36 Explanation:
The correct answer is (B). The optimal foraging model is used to predict behaviors that maximize the benefits (eating grass) of a feeding behavior while minimizing both the energy expended obtaining the food and the risks associated with (getting eaten by a mountain lion) obtaining the food. Cross-fostering refers to a method used by researchers to determine which environmental conditions contribute to behavior. Associative learning is the ability to associate one environmental feature with another, such as learning that yellow and black flying insects sting. Proximate causation looks the immediate cause of a behavior.
In some animal societies, such as honeybees, a single female mates with several males. This is referred to as:
Question 37 Explanation:
The correct answer is (C). Polyandry is a relationship in which one female mates with multiple males. Monogamous relationships involve mates that remain together for a long period of time. Polygyny is a relationship in which one male mates with multiple females. Polygenetic, as in polygenetic inheritance, refers to the effect of two or more genes on a single phenotypic character.
As tadpoles change into frogs, their tails get smaller and smaller as the cells die and are engulfed by neighboring cells. This is a familiar example of programmed cell death, which is referred to as:
Embryonic cell death
Question 38 Explanation:
The correct answer is (D). Apoptosis is a genetically programmed series of events that result in cell death. Caspases are enzymes that carry out apoptosis. Bulk flow is term for the overall movement of fluid in one direction in an organism.
Although the leaves of a pitcher plant, a Venus flytrap, and a cactus do not appear to be very similar, they are derived from a structure present in a common ancestor. This is an example of:
Question 39 Explanation:
The correct answer is (A). Homologous structures have a common ancestry.
Which description best describes a cell-mediated response to a pathogen?
Defenses, such as skin, mucous membranes and secretions that form a barrier
The proliferation of B cells
Antibodies defending against infections in body fluids
Cytotoxic T cells defending the body against cells
Question 40 Explanation:
The correct answer is (D). Cytotoxic T cells attack foreign cells, cells infected with a virus and cancerous cells.
Saliva, tears, epithelial tissues and the mucous membranes of the digestive, respiratory, urinary and reproductive tracts make up which part of the mammalian immune system?
Question 41 Explanation:
The correct answer is (A). Barrier defenses block the entry of pathogens into the body.
If a body cell does not have the protein called a class I MHC molecule on its surface, it is likely that it has been infected by a virus or converted into a cancerous state. What type of cell patrols the body, attaches to cells without class I MHC molecules, and kills the cell so it cannot spread the virus or cancer?
Natural killer cells
Question 42 Explanation:
The correct answer is (B). Natural killer cells help recognize and eliminate certain diseased cells in vertebrates by secreting chemicals if they do not have a protein called a class I MHC molecule on their surface (with the exception of red blood cells).
Which type of response to a pathogen in plants leads to cell and tissue death near the infection site, thereby preventing the spread of the disease?
Systemic acquired resistance
Recruitment of parasitoids
Question 43 Explanation:
The correct answer is (C). A hypersensitive response takes place when a plant produces antimicrobial molecules, seals off infected cells, and kills off cells and/or tissues that are infected. System acquired resistance involve signaling molecules that put the entire plant on alert for a pathogen. Gene-for-gene recognition is the mechanism that allows the plant to recognize pathogens based on the recognition of pathogen-derived molecules. Plants recruit parasitic organisms that defend the plant against herbivores (not pathogens).
Which example from the list below illustrates the two species that likely share the most recent common ancestor?
Hawaiian silversword plants vary dramatically in their appearance. Some are tall, twiggy trees and others are dense, ground-hugging shrubs. Yet, the silverswords’ genes are very similar to each other.
Wings of birds and insects perform the same function, flying or movement through the air.
New World vultures (Cathartidae family) and Old World (Accipitridae family) vultures look very similar, both have featherless necks and hears, and feed on carrion. New World vultures use only visual senses to hunt for prey, whereas Old World vultures use the sense of vision as well as smell for preying purposes.
Penguins and fish both have fin-like structures to help them navigate through their aquatic environments.
Question 44 Explanation:
The correct answer is (A). In general, if an organism shares a very similar morphological characteristic or similar DNA sequences with another organism, they are more likely to be closely related than organisms with different structures and DNA sequences. However, in some cases the morphological differences can be great and genetic differences can be small (or vise-versa). Comparing traits in several different ways, such as fossil evidence and molecular comparisons can help determine ancestry. All of the above examples, except for (A), show analogous structures, which do not share common ancestry. An organism’s evolutionary history is documented in its genome.
Look at the four phylogenetic trees below. Which tree shows a different evolutionary history for taxa A–D than the other three trees?
Question 45 Explanation:
The correct answer is (A). The phylogenetic tree in (A) shows the different pattern of evolutionary history. In answers (B), (C) and (D), species “C” and species “D” are sister taxa. In answer (A), species “C” and species “B” are sister taxa.
Based on this phylogenetic tree, which statement is not true?
Crocodilians are a sister group to the group containing pterosaurs, ornithischian dinosaurs and saurischian dinosaurs.
Orithischian dinosaurs and saurischian dinosaurs are more closely related to birds than lizards and snakes.
The lineage leading to the lizards and snakes was the first to diverge from the other lineages.
Crocodilians are more closely related to ornithischian dinosaurs than lizards.
Question 46 Explanation:
The correct answer is (D). Phylogenetic trees are branching diagrams that show the evolutionary history of a group of organisms. Phylogenetic trees show relationships between groups of organisms. These relationships are shown as branch points, where each branch point represents the divergence of two evolutionary lineages from a common ancestor. Sister taxa are groups of organisms that share an immediate common ancestor. This tree shows that crocodilians are more closely related to lizards and snakes, than to ornithischian dinosaurs, which are not adjacent to the crocodilians on the tree.
Which of the following lists the hierarchical classification system from most to least inclusive?
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
Phylum, Domain, Kingdom, Class, Order, Family, Genus, Species
Domain, Species, Genus, Family, Order, Class, Phylum, Kingdom
Kingdom, Phylum, Class, Order, Family, Genus, Species, Domain
Question 47 Explanation:
The correct answer is (A). Domain is the most inclusive category, and species is the least.
Which domain has the following characteristics:
- No internal membranes
- May be aerobic or anaerobic
- Contain peptidoglycan in their thick, rigid cell walls
- No introns
Question 48 Explanation:
The correct answer is (B). Domain Bacteria has the characteristics described. Domain Archaea differs in that it may Archaean cells contain introns in some genes and they do not have peptidoglycan. Domain Eukarya includes all organisms with a nucleus, internal organelles and no peptidoglycan. Eukarya includes the following kingdoms: Protista (a polyphyletic grouping), Fungi, Plantae, and Animalia. Prokarya was the taxon that contained all prokaryotic organisms, has been split into two domains: Archaea and Bacteria.
Which kingdom has the following characteristics:
- May be either heterotrophs or autotrophs
- May move by a variety of methods including pseudopods, cilia or flagella
- Some carry serious diseases such as malaria
- Include the widest variety of eukaryotic organisms
Question 49 Explanation:
The correct answer is (D). Kingdom Protista have the characteristics listed above. Kingdom Animalia are all heterotrophic and do not move by the same mechanisms. Kingdom Fungi are also heterotrophic and immobile. Kingdom Plantae are immobile and most are autotrophic.
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