Biology Chapter 13
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What is the definition of evolution?
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the idea that Earth's many species are descendants of ancestral species that were different from those living today.
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What is the definition of fossils?
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the imprints or remains of organisms that lived in the past.
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What did Darwin call evolutionary history of all life?
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descent with modification
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What is the definition of adaptation?
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An inherited characteristic that enhances an organism's ability to survive and reproduce in a particular environment.
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What is Darwin's proposed mechanism for this descent with modification (evolution)?
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natural selection
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What is the definition of artificial selection?
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Human selective breeding of domesticated plants and animals to promote the occurrence of desirable traits.
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What is the definition of natural selection?
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A process in which individuals with certain inherited traits are more likely to survive and reproduce than are individuals that do not have those traits.
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What two inferences did Darwin conclude about natural selection?
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1. individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals. 2. This unequal production of offspring will lead to the accumulation of favorable traits in a population over generations.
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Darwin recognized the connection between _____ _____ and the capacity of organisms to ______.
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natural selection/ overproduce
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Darwin reasoned that if _____ _____ can bring about so much change in a relatively short period of time, then _____ ____ could modify species considerably over hundreds or thousands of generations.
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artificial selection/ natural selection
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Natural selection will select for adaptations to new conditions, sometimes producing changes that result in the origin of a _____ species in the process.
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new
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What are the three key points about evolution?
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1. Individuals do NOT evolve. 2. natural selection can amplify or diminish only HERITABLE TRAITS. 3. Evolution is NOT goal directed; it does not lead to perfectly adapted organisms.
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An unsettling example of natural selection in action is the evolution of ______ _____ in hundreds of insect species.
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pesticide resistance
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What two main points does evolutionary adaptation make about natural selection?
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1. natural selection is more of an editing process than a creative mechanism. 2. natural selection is contingent on time and place: It favors those heritable traits in a varying population that fit the current, local environment.
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The study of ______ provides strong evidence for evolution
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fossils
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Fossils document differences between ____ and _____ organisms and the fact that many species have become extinct.
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past / present
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When do fossils result?
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When a dead organism captured in sediment decays and leaves an empty mold that is later filled by minerals dissolved in water.
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What is the definition of fossil record?
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The chronicle of evolution over millions of years of geologic time engraved in the order in which fossils appear in rock strata.
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Why is the fossil record incomplete?
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Because not all organisms live in areas that favor fossilization, many rocks are distorted by geologic processes, and not all fossils that have been preserved will be found.
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How old is the oldest known fossils?
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3.5 billion years old
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It was the geographic distribution of species, known as_____, that first suggested to Darwin that organisms evolve from ancestral species.
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biogeography
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Anatomical similarities and differences between species give signs of common_____.
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descent
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What is the definition of homology?
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Similarity in characteristics resulting from shared ancestry.
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What is the definition of homologous structures?
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Structures in different species that are similar because of common ancestry.
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What does comparative anatomy illustrate?
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Evolution is a remodeling process in which ancestral structures that originally functioned in one capacity become modified as they take on new functions. (descent with modification)
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What is the definition of vestigial structures?
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A feature of an organism that is a historical remnant of a structure that served a function in the organism's ancestors.
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Anatomical biology is not helpful in linking _____ _____ related organisms.
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very distantly
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In recent decades, advances in ____ _____ have enabled biologists to read a molecular history of evolution in the DNA sequences of organisms.
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molecular biology
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Darwin's boldest hypothesis was that____ life-forms are related.
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all
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Homologies indicate patterns of descent that can be shown on an ______ ____.
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evolutionary tree
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What is the definition of an evolutionary tree?
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A branching diagram that reflects a hypothesis about the evolutionary relationships among groups of organisms.
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Evolution occurs within_____.
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populations
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What is the definition of a population?
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A group of individuals of the same species that live in the same area and interbreed.
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What are some key features of populations?
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1. different populations of the same species may be isolated from one another, with little interbreeding an thus little exchange of genes between them. 2. members of one population are generally more closely related to each other than to members of other populations.
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What is the definition of a gene pool?
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All the alleles for all the genes in a population.
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What is an example of microevolution?
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When the relative frequencies of alleles in a population change like this over a number of generations, evolution is occurring on the smallest scale.
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What is the definition of microevolution?
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A change in a population's gene pool over generations.
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_____ and _____ _____ produce the genetic variation that makes evolution possible.
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mutation / sexual reproduction
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Is all variation in a population heritable?
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NO
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The phenotype results from a combination of the _____, which is inherited, and many______ influences.
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genotype/ environmental
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New alleles originate by _____, a change in nucleotide sequence of DNA.
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mutation
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_____ variation is necessary for a population to evolve, but variation alone does not guarantee that microevolution will occur.
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Genetic
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The ____-____ equation can test whether a population is evolving.
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Hardy/ Weinberg
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The shuffling of alleles that accompanies sexual reproduction___ ____ alter the genetic makeup of the population.
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does not
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The letters _ and __ are often used to represent allele frequencies.
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p/ q
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The frequency of the two alleles in the gametes will be the ____ as their frequencies in the gene pool of the parental population.
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same
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The gene pool of this population is in a state of _____.
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equilibrium
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What is the Hardy-Weinberg equation?
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p^2 + 2pq + q^2 = 1.
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p^2 represents what?
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Frequency of homozygous dominants
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2pq represents what?
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Frequency of heterozygotes
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q^2 represents what?
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Frequency of homozygous recessives
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The Hardy-Weinberg equation tells us that something other than the ____ process of ____ reproduction is required to change allele frequencies in a population.
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shuffling/ sexual
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For a population to be in Hardy-Weinberg equilibrium, it must satisfy five main conditions. What are they?
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1. Very large population 2. No gene flow between populations 3. No mutations 4. Random mating 5. No natural selection
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The smaller the population, the ___ likely that allele frequencies will fluctuate by chance from one generation to the next.
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more
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When individuals move into or out of populations, they ____ or ____ alleles, altering the gene pool.
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add / remove
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By ____ alleles or ____ or _____ genes, mutations modify the gene pool.
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changing / deleting / duplicating
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If individuals mate ______, such as with close relatives, random mixing of gametes does ____ occur, and genotype frequencies change.
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preferentially / not
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The _____ survival and reproductive success of individuals ( natural selection) can alter allele frequencies.
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unequal
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Because it is rare that all five conditions are met in real populations, genotype frequencies ____ change.
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do
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Another use for the Hardy-Weinberg equation is to estimate how many people carry _____ for certain inherited ____.
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alleles / diseases
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What are 3 mechanisms of microevolution?
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genetic drift, natural selection, and gene flow
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If there were no natural selection, then all individuals in a population are ____ in ability to reproduce.
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equal
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What is the definition of genetic drift?
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A change in the gene pool of a population due to chance. Effects of genetic drift are most pronounced in small populations.
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Two situations in which genetic drift can have significant impact on a population are those that produce ____ ____ and the _____ effect.
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bottleneck effect / founder
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What is the definition of a bottleneck effect?
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Genetic drift from a drastic reduction in population size. Typically, the surviving population is no longer genetically representative of the original population.
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What are a few examples of the bottleneck effect?
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earthquakes, floods, or fires
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What is the definition of the founder effect?
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Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool is not reflective of that of the original population.
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What is the definition of gene flow?
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The transfer of alleles from one population to another as a result of the movement of individuals or their gametes.
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____ _____ is the only mechanism that consistently leads to adaptive evolution.
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natural selection
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Adaptive evolution is a _____ dynamic process.
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continuous
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What is the definition of relative fitness?
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The contribution of an individual makes to the gene pool of the next generation, relative to the contributions of other individuals in the population.
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Natural selection can alter variation in a population in ___ ways.
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3
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What are the 3 ways that natural selection can alter variation in a population?
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1. stabilizing selection 2. directional selection 3. disruptive selection
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What is the definition of stabilizing selection?
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Natural selection that favors intermediate variants by acting against extreme phenotypes.
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What is the definition of directional selection?
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Natural selection in which individuals at one end of the phenotypic range survive and reproduce more successfully than do other individuals.
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What is the definition of disruptive selection?
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Natural selection in which individuals on both extremes of a phenotypic range are favored over intermediate phenotypes.
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____ selection may lead to phenotypic differences between males and females.
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sexual
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What is the definition of sexual selection?
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A form of natural selection in which individuals with certain inherited traits are more likely than other individuals to obtain mates.
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What is the definition of sexual dimorphism?
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Marked differences between the secondary sex characteristics of males and females.
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What is the definition of intrasexual selection?
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Individuals competing directly with members of the same sex for mates.
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What is the definition of intersexual selection?
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Individuals of one sex are choosy in selecting their mates ( usually females)
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Females prefer male traits that are correlated with ____ ____.
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good genes
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The evolution of _____ resistance in bacteria is a serious public health concern.
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antibiotic
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In what ways do we contribute to the problem of antibiotic resistance?
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1. Livestock producers add antibiotics to animal feed as growth promoter and to prevent illness. 2. Doctors overprescribe antibiotics 3. Patients may misuse prescribed antibiotics by prematurely stopping the medication because they feel better.
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Diploidy and balancing selection _____ genetic variation.
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preserve
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Having two sets of chromosomes helps to prevent populations from becoming genetically ______.
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uniform
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What are 2 ways that genetic variation is preserved?
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1. diploidy 2. balancing selection
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What are 2 types of balancing selections?
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1. heterozygote advantage 2. frequency-dependent selection
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What is the definition of balancing selection?
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Natural selection that maintains stable frequencies of two or more phenotypic forms in a population.
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What is the definition of heterozygote advantage?
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Greater reproductive success of heterozygous individuals compared to homozygotes; tends to preserve variation in gene pools.
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What is the definition of frequency-dependent selection?
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Selection in which the fitness of a phenotype depends on how common the phenotype is in a population
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Natural selection ____ ____ fashion perfect organisms.
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can not
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What are several reasons why nature abounds with organisms that seem to be less than ideally engineered for their lifestyles?
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1. selection can act only on existing variations. 2. evolution is limited by historical constraints. 3. adaptations are often compromises. 4. Chance, natural selection, and the environment interact.
