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AP Bio Exam: Unit 7
AP Exam
| Question | Answer |
|---|---|
| What is natural selection? | Process where organisms better adapted to their environment tend to survive and produce more offspring. |
| How does natural selection lead to evolution? | It increases the frequency of advantageous traits in a population over generations. |
| What are two causes of natural selection? | Variation in traits and differential survival and reproduction. |
| What is Darwin’s theory of natural selection? | Evolution occurs through natural selection acting on heritable variation. |
| What does differential survival mean? | Individuals with favorable traits are more likely to survive and reproduce. |
| TRUE or FALSE: Favorable traits are ALWAYS favorable. | False; traits depend on environmental context. |
| Why do organisms require competition for limited resources to allow for natural selection? | Competition drives selection for traits that enhance resource acquisition. |
| How does natural selection affect populations? | It changes the allele frequencies, leading to adaptation. |
| What is evolutionary fitness? | The ability of an organism to survive and reproduce in its environment. |
| How is evolutionary fitness measured? | By the number of viable offspring an individual produces. |
| What is reproductive success? | The production of offspring that reach reproductive age. |
| How does reproductive success lead to natural selection? | Successful individuals pass advantageous alleles to the next generation. |
| What does biotic and abiotic mean? | Biotic refers to living factors; abiotic refers to non-living physical/chemical factors. |
| How does a biotic environment affect the direction of evolution? | Predation, competition, and disease drive specific adaptations. |
| How does an abiotic environment affect the direction of evolution? | Climate, pH, and salinity select for physiological tolerances. |
| How does a biotic environment affect the rate of evolution? | High interaction rates (e.g., predator-prey) can accelerate evolution. |
| How does an abiotic environment affect the rate of evolution? | Stable environments slow evolution; rapid changes accelerate it. |
| How does a genetic variation affect natural selection? | It provides the raw material for selection to act upon. |
| What is phenotype? | The observable physical or biochemical characteristics of an organism. |
| How does phenotypic variation lead to differential success? | Variations affect survival and reproduction rates in a specific environment. |
| What does natural selection act on … PHENOTYPE or GENOTYPE? | Phenotype. |
| What does natural selection modify … PHENOTYPE or GENOTYPE? | Genotype (indirectly, by selecting phenotypes). |
| How does natural selection act on and modify different levels of genes? | It acts on the whole organism but changes allele frequencies. |
| What are selective pressures? | Environmental factors that favor certain traits over others. |
| How does an environment apply a selective pressure to a population? | It challenges survival, favoring individuals with beneficial traits. |
| Describe how a population changes due to an applied selective pressure. | Allele frequencies shift toward traits that confer higher fitness. |
| Identify two examples of a phenotypic variation that increases fitness of an organism in a particular environment. | Antibiotic resistance in bacteria; camouflage in moths. |
| Identify two examples of a phenotypic variation that decreases fitness of an organism in a particular environment. | Lack of camouflage in prey; heat intolerance in mammals. |
| How does the MC1R gene found in the Rock Pocket Mouse population causing expression of dark colored melanin pigmentation lead to differential success on the dark lava flows? | Dark fur provides camouflage, reducing predation on dark lava flows. |
| How does a mutation in the cortex gene in Peppered Moths leading to darker coloration aid in their survival in polluted forests? | Dark coloration camouflages moths against soot-covered trees, reducing predation. |
| Describe the difference in the expression of the Pitx1 gene in marine vs freshwater stickleback fish. | Marine fish express Pitx1 for spines; freshwater fish suppress it to avoid dragonfly predation. |
| How can cells differ in the number and types of molecules within cells? | Gene expression levels vary, leading to different protein concentrations. |
| How does variation at the molecular level affect the organism’s ability to respond to environmental stimuli? | It alters metabolic pathways and stress responses. |
| How does this variation in number of molecules lead to a selective advantage? | More efficient molecules improve survival under specific conditions. |
| How does this variation in types of molecules lead to a selective advantage? | Specialized molecules allow exploitation of unique niches. |
| In cold-weather mammals, why would do the cells in the body core have more saturated fatty acids while cells in the legs and ears have more unsaturated fatty acids? | Saturated fats stay fluid at core temps; unsaturated fats prevent freezing in extremities. |
| How do fetal hemoglobin and adult hemoglobin differ in their oxygen affinity? | Fetal hemoglobin has higher affinity to extract oxygen from maternal blood. |
| Describe the need for this difference based on survival at different life stages? | Ensures the fetus receives adequate oxygen for development. |
| What is the difference between chlorophyll a and chlorophyll b? | Chlorophyll a is the primary reaction center; b is an accessory pigment. |
| How does the variation in the amount of these chlorophylls provide differential success to these different plants? | Shady plants use more b to capture available light; bright-light plants use a for efficiency. |
| What is artificial selection? | Human-directed breeding for desired traits. |
| How does artificial selection modify the variation in a species? | It exaggerates specific traits, reducing genetic diversity. |
| Identify two examples of artificial selection due to humans. | Dog breeds; crop varieties. |
| How has this modified the species? | Created distinct morphologies and behaviors not found in wild ancestors. |
| What are mutations? | Changes in the DNA sequence. |
| Identify two examples of mutations that potentially could affect phenotype. | Point mutations; chromosomal rearrangements. |
| How do mutations affect genetic makeup of a population? | They introduce new alleles, increasing genetic variation. |
| What is genetic drift? | Random fluctuation of allele frequencies in a population. |
| What is the bottleneck effect? | Sharp reduction in population size due to an event, losing genetic diversity. |
| How does the bottleneck effect modify genetic makeup of a population? | It reduces genetic variation and alters allele frequencies randomly. |
| Identify one example of a population that has undergone the bottleneck effect. | Cheetahs; Northern elephant seals. |
| What is the founder’s effect? | Loss of genetic variation when a new population is started by a few individuals. |
| How does the founder’s effect modify genetic makeup of a population? | The new population has different allele frequencies than the source. |
| Identify one example of a population that has undergone the founder’s effect. | Amish populations; Galapagos finches. |
| What is gene flow? | Movement of alleles between populations via migration. |
| How does gene flow modify genetic makeup of a population? | It increases genetic diversity and reduces differences between populations. |
| Identify one example of a population that has undergone gene flow. | Pollen transfer between plant populations; animal migration. |
| What is the effect of mutations on genetic variation? | They create new alleles, the source of variation. |
| How does genetic variation lead to a variation in phenotypes? | Different alleles produce different traits and physical characteristics. |
| Identify two examples of natural selection acting on phenotypes. | Sickle cell trait in malaria zones; beak shape in finches. |
| What are the three types of selection? | Directional, stabilizing, and disruptive. |
| Identify an example of each type of selection. | Directional: Giraffe necks; Stabilizing: Human birth weight; Disruptive: Finch beaks. |
| How does genetic drift affect a small population vs a large population? | It has a stronger effect in small populations due to sampling error. |
| How does genetic drift cause a small population to diverge from other populations of the same species? | Random changes lead to unique allele frequencies. |
| How does gene flow affect a population? | It introduces new alleles, making populations more similar. |
| How does gene flow affect the genetic variation between two populations of the same species? | It decreases genetic divergence between them. |
| How can you measure allele frequencies changes? | By tracking the proportion of alleles in a population over time. |
| What causes changes in allele frequencies? | Natural selection, genetic drift, gene flow, and mutations. |
| What does a change in allele frequency provide evidence of? | Evolution occurring in the population. |
| What is Hardy-Weinberg equilibrium? | A state where allele and genotype frequencies remain constant across generations. |
| What are the five conditions that must be TRUE for Hardy-Weinberg equilibrium? | No mutation, random mating, no gene flow, infinite population size, no selection. |
| What is allele frequency? | The relative abundance of an allele in a population. |
| What is genotypic frequency? | The proportion of individuals with a specific genotype. |
| What are the equations for Hardy-Weinberg equilibrium? | p + q = 1 and p^2 + 2pq + q^2 = 1. |
| Ident all the variables in the Hardy-Weinberg equation. | p = freq. of dominant allele; q = freq. of recessive allele. |
| Solve for the alleles if there are three colors of snapdragons: 100 red, 800 pink, 100 white. | q = 0.316, p = 0.684. |
| Solve for the alleles if 75% of flowers are purple (dominant) and 25% are white (recessive). | q = 0.5, p = 0.5. |
| What does it mean if the allele frequency changes from one generation to the next? | The population is evolving. |
| What does it mean if the genotype frequency stays the same from one generation to the next? | The population is in Hardy-Weinberg equilibrium. |
| Why are small populations more susceptible to changes in allele frequency? | Genetic drift has a larger impact due to sampling error. |
| What is biogeography? | The study of the distribution of species and ecosystems in geographic space. |
| How does geographical data support evolution? | Similar environments host distinct species, showing adaptation to conditions. |
| Provide one example of geographical data. | Continental drift patterns; island species distribution. |
| How does geological data support evolution? | Fossil layers show progression of life forms over time. |
| Provide one example of geological data. | Radiometric dating of rocks; transitional fossils. |
| How does physical data support evolution? | Homologous structures indicate common ancestry. |
| Provide one example of physical data. | Forelimb bones in humans, bats, and whales. |
| How does biochemical data support evolution? | Shared DNA and protein sequences indicate relatedness. |
| Provide one example of biological data. | Cytochrome c gene comparison across species. |
| How does mathematical data support evolution? | Population genetics models predict evolutionary changes. |
| Provide one example of mathematical data. | Hardy-Weinberg equilibrium calculations. |
| What are extant and extinct organisms? | Extant are currently living; extinct are no longer living. |
| What are fossils? | Preserved remains or traces of ancient organisms. |
| How can fossils be used as evidence of evolution? | They document the sequence of historical life forms. |
| Describe THREE ways fossils can be dated. | Radiometric dating, relative dating (stratigraphy), and index fossils. |
| How do the rock layers allow for dating of fossils? | Older layers are deeper; fossils in lower layers are generally older. |
| What is carbon-14 decay? | Radioactive decay of carbon-14 isotopes over time. |
| How can carbon-14 decay be used to date fossils? | By measuring remaining C-14 to estimate age (up to ~50,000 years). |
| How can geographical data be used to date fossils? | Correlating rock layers across continents using index fossils. |
| What are homologous structures? | Anatomical features similar in origin but different in function. |
| What are analogous structures? | Features similar in function but different in evolutionary origin. |
| What is embryology? | The study of embryos and their development. |
| Which results from convergent evolution (not representing common ancestry)? | Analogous structures. |
| DNA and proteins can be used as evidence of evolution. Which is more accurate to determine most recent common ancestor? | DNA. |
| Justify why DNA is more accurate to determine most recent common ancestor. | DNA mutations accumulate regularly and are less influenced by environment. |
| How do the number of differences of nucleotides or amino acids demonstrate ancestry of organisms? | Fewer differences indicate a more recent common ancestor. |
| What are membrane bound organelles? | Specialized structures enclosed by lipid membranes within eukaryotic cells. |
| What type of cells have membrane bound organelles? | Eukaryotic. |
| How did membrane bound organelles originate? | Through endosymbiosis and infolding of the plasma membrane. |
| How do membrane bound organelles indicate common ancestry for all eukaryotes? | Shared complex structures suggest a single eukaryotic ancestor. |
| Describe a linear chromosome. | A DNA molecule with ends (telomeres) found in eukaryotic nuclei. |
| How are prokaryotic chromosomes organized? | Typically circular DNA in the nucleoid region. |
| How are eukaryotic chromosomes organized? | Linear DNA wrapped around histones in the nucleus. |
| How do linear chromosomes indicate common ancestry for all eukaryotes? | Shared structural features imply a common origin. |
| What is an intron? | Non-coding sequence of DNA that is transcribed but removed from mRNA. |
| When are introns removed? | During RNA splicing in the nucleus. |
| What type of cells have introns? | Eukaryotic. |
| How do genes containing introns indicate common ancestry for all eukaryotes? | The presence of splicing machinery is a shared derived trait. |
| What evolves? Individuals or Populations? | Populations. |
| True or False: Once a population of organisms are perfect, they will cease evolving. | False; environments change, so "perfection" is temporary. |
| How can scientists use genomes to prove that all species continue to evolve? | By comparing genetic changes and mutations over time. |
| How can scientists use fossil record to prove that all species continue to evolve? | Fossils show morphological changes and extinction events. |
| What does it mean if a population of bacteria is antibiotic resistant? | The bacteria can survive and reproduce despite antibiotic presence. |
| How does a population of bacteria become antibiotic resistant? | Selection for resistant mutants due to antibiotic overuse. |
| How does this resistance to antibiotics support the claim that all species have evolved and continue to evolve? | It demonstrates natural selection acting on heritable variation in real time. |
| Why do you need to get the influenza vaccine every year? | The virus evolves rapidly via antigenic drift and shift. |
| How does the fact that viruses and other pathogens change over time support the claim that all species have evolved and continue to evolve? | It shows evolution is an ongoing process for all life. |
| What type of evidence can be used to infer an evolutionary relationship? | Morphology, DNA sequences, and fossil records. |
| Describe how to develop a phylogenetic tree. | Use shared derived characteristics to map evolutionary relationships. |
| Describe how to develop a cladogram. | Group organisms by shared traits to show branching patterns. |
| What is a phylogenetic tree? | A diagram showing evolutionary relationships among species. |
| What is a cladogram? | A diagram showing nested groups of organisms based on shared traits. |
| Identify one similarity about the data presented in a phylogenetic tree and cladogram. | Both depict branching relationships and common ancestry. |
| Identify one difference about the data presented in a phylogenetic tree and cladogram. | Phylogenetic trees include time/scale; cladograms focus on trait order. |
| Where would you see a gained or lost trait on a cladogram or phylogenetic tree? | At the branch points (nodes). |
| What are shared characters? | Traits common to all members of a group. |
| What are derived characters? | Traits unique to a specific clade or lineage. |
| What is an outgroup? | A species or group closely related to but not part of the group being studied. |
| How do you identify the outgroup on a cladogram? | It branches off from the base before the main group. |
| Which is the most accurate and reliable data for construction of phylogenetic tree or cladogram? | Molecular data. |
| Justify why molecular data is the most accurate and reliable. | It provides quantitative data on genetic divergence. |
| What does a branch point in a cladogram or phylogenetic tree represent? | A speciation event or common ancestor. |
| How do you determine the most recent common ancestor on a cladogram or phylogenetic tree? | Trace branches back to where they converge. |
| What evidence is used to construct a cladogram or phylogenetic tree? | Morphological, molecular, and fossil data. |
| When using molecular evidence, how do you determine if two organisms are closely related? | Compare DNA or protein sequences; fewer differences = closer relation. |
| When using fossil evidence, how do you determine if two organisms are closely related? | Look for similar structures in overlapping rock layers. |
| How do you construct a cladogram using similarity in DNA sequences? | Group organisms by the fewest sequence differences. |
| What is speciation? | The formation of new and distinct species in the course of evolution. |
| What causes speciation? | Reproductive isolation and genetic divergence. |
| What is reproductive isolation? | Mechanisms that prevent members of two species from producing viable offspring. |
| Identify FIVE types of reproductive isolation. | Habitat, temporal, mechanical, behavioral, and gametic isolation. |
| Describe FIVE types of reproductive isolation. | Habitat: different locations; Temporal: different times; Mechanical: structural mismatch; Behavioral: different mating rituals; Gametic: gametes cannot fuse. |
| What is the biological species concept? | Species are groups of actually or potentially interbreeding natural populations. |
| How can you determine if two organisms are from the same species according to the biological species concept? | If they can interbreed and produce fertile, viable offspring in nature. |
| What is punctuated equilibrium? | Evolution characterized by rapid bursts of change separated by long periods of stability. |
| Identify an example of an organism that underwent punctuated equilibrium. | Trilobites during the Cambrian explosion show rapid diversification. |
| What is gradualism? | Evolution occurring slowly and steadily over long periods of time. |
| Identify an example of an organism that underwent gradualism. | The horse shows gradual changes in size and toe structure over millions of years. |
| What is divergent evolution? | Related species evolving different traits, often due to different environments. |
| What term do we use when two organisms have similar characteristics due to divergent evolution? | Homologous structures. |
| What is adaptive radiation? | Rapid evolution of many species from a single ancestor to fill available niches. |
| What is the effect of adaptive radiation on speciation rates? | Significantly increases speciation rates by creating diverse ecological roles. |
| What is convergent evolution? | Unrelated species evolving similar traits due to similar environmental pressures. |
| Identify two examples of organisms that demonstrate convergent evolution. | Dolphins (mammals) and sharks (fish) both have streamlined bodies. |
| How do selective pressures result in similar phenotypic adaptations? | Similar environmental challenges favor similar functional solutions in unrelated lineages. |
| What are the results of speciation? | Formation of new species that cannot interbreed with the ancestral population. |
| What is sympatric speciation? | Speciation occurring without geographic isolation, often via polyploidy. |
| What mechanisms lead to speciation in sympatric speciation? | Polyploidy in plants or sexual selection driving behavioral isolation. |
| What is allopatric speciation? | Speciation occurring due to geographic isolation of populations. |
| What mechanisms lead to speciation in allopatric speciation? | Physical barriers like mountains or rivers prevent gene flow. |
| What is the difference between pre and post-zygotic reproductive barriers? | Pre-zygotic prevent fertilization; post-zygotic prevent hybrid development or reproduction. |
| What is temporal isolation? | Species breed at different times (seasons, times of day). Example: Western spotted skunk breeds in fall, eastern skunk in winter. |
| What is behavioral isolation? | Unique mating signals or behaviors prevent interbreeding. Example: Specific firefly flash patterns. |
| What is mechanical isolation. | Structural differences prevent successful mating. Example: Snail shell coiling direction prevents copulation. |
| What is gametic isolation? | Gametes fail to fuse or survive. Example: Sea urchin sperm cannot fertilize eggs of other species. |
| What is habitat isolation? | Species live in the same area but different habitats. Example: One species lives in soil, another in trees. |
| What is reduced hybrid viability? | Hybrid offspring are weak or die early. Example: Hybrid salamanders often fail to develop properly. |
| What is reduced hybrid fertility? | Hybrid offspring are sterile. Example: Mules (horse + donkey) are sterile. |
| What is hybrid breakdown? | First generation hybrids are viable, but later generations are weak or sterile. Example: Hybrid rice plants decline in second generation. |
| How does reproductive isolation lead to speciation? | It prevents gene flow, allowing populations to diverge genetically over time. |
| What three potential results occur when two species come in contact in the hybrid zone? | Reinforcement, fusion, or stability of the hybrid zone. |
| What is genetic diversity? | Total genetic information within a population. |
| Why are populations with little genetic diversity at risk of decline or extinction? | Low diversity reduces ability to adapt to environmental changes or resist disease. |
| If a population is more genetically diverse, how do they respond to environmental changes? | Higher likelihood of survival due to presence of advantageous traits. |
| What is the advantage of a population being genetically diverse? | Increased resilience and adaptability to changing environments. |
| True or False: Alleles that are helpful in one environment will be helpful in another environment. | False; allele fitness depends on specific environmental context. |
| Why do alleles affect individuals differently in different environments? | Selective pressures vary, altering the fitness value of specific traits. |
| What geological evidence provide support for the origin of Earth? | Zircon crystals showing liquid water presence in early Hadean eon. |
| Approximately when did the Earth form? | About 4.6 billion years ago. |
| Approximately when was Earth no longer hostile for life? | About 3.9 to 4.0 billion years ago. |
| Approximately when does the earliest fossil date? | About 3.5 billion years ago (stromatolites). |
| What is the RNA World Hypothesis? | Proposes that RNA, not DNA, was the first genetic material and catalyst. |
| Identify three supports for the RNA World Hypothesis. | RNA stores genetic info, catalyzes reactions (ribozymes), and can evolve. |
| What are ribozymes? | RNA molecules that act as enzymes to catalyze reactions. |
| How do ribozymes confirm the RNA hypothesis? | They demonstrate RNA can both store genetic info and function as a catalyst. |
| Describe the base pairing needed for replication. | Complementary base pairing (A-U/T, G-C) allows accurate copying. |
| TRUE or FALSE: Genetically encoded proteins were involved as catalysts. | False; early life likely used RNA catalysts before proteins evolved. |
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