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What is the name of the scientist who proposed the theory of gradualism?
What is the name of the scientist who proposed the theory of gradualism?
James Hutton
What is the name of the book that Charles Darwin published in 1859?
What is the name of the book that Charles Darwin published in 1859?
On the Origin of Species
What is the main idea behind Darwin's theory of evolution?
What is the main idea behind Darwin's theory of evolution?
Descent with modification
Which French scientist made significant contributions to paleontology?
Which French scientist made significant contributions to paleontology?
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What is the name of the process by which humans select and breed organisms with desirable traits?
What is the name of the process by which humans select and breed organisms with desirable traits?
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Which of the following observations did Darwin make about populations?
Which of the following observations did Darwin make about populations?
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What are the two inferences Darwin drew from his four observations?
What are the two inferences Darwin drew from his four observations?
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Fossils provide evidence for evolution because they show that life forms on Earth have stayed essentially the same throughout history.
Fossils provide evidence for evolution because they show that life forms on Earth have stayed essentially the same throughout history.
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Homologous structures are similar structures that evolved independently in different species, indicating a common ancestor.
Homologous structures are similar structures that evolved independently in different species, indicating a common ancestor.
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Vestigial structures are remnants of features in organisms that have lost their original function but still remain as evidence of evolutionary history.
Vestigial structures are remnants of features in organisms that have lost their original function but still remain as evidence of evolutionary history.
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Convergent evolution refers to the development of similar features in unrelated species due to similar environmental pressures.
Convergent evolution refers to the development of similar features in unrelated species due to similar environmental pressures.
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What is the name of the supercontinent that existed before continental drift?
What is the name of the supercontinent that existed before continental drift?
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What is the smallest unit of evolution?
What is the smallest unit of evolution?
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What are the two main processes that contribute to genetic variation in populations?
What are the two main processes that contribute to genetic variation in populations?
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A point mutation is a change in a single nucleotide within a gene.
A point mutation is a change in a single nucleotide within a gene.
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Sexual reproduction increases genetic diversity by shuffling existing alleles, while mutation introduces entirely new alleles.
Sexual reproduction increases genetic diversity by shuffling existing alleles, while mutation introduces entirely new alleles.
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What are the five conditions that must be met for a population to remain in Hardy-Weinberg equilibrium (not evolving)?
What are the five conditions that must be met for a population to remain in Hardy-Weinberg equilibrium (not evolving)?
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Which of the following is NOT one of the three main factors that can alter allele frequencies in a population?
Which of the following is NOT one of the three main factors that can alter allele frequencies in a population?
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Genetic drift is more likely to have a significant impact on allele frequencies in large populations than small populations.
Genetic drift is more likely to have a significant impact on allele frequencies in large populations than small populations.
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Describe the founder effect.
Describe the founder effect.
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Describe the bottleneck effect.
Describe the bottleneck effect.
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Gene flow refers to the movement of alleles between populations.
Gene flow refers to the movement of alleles between populations.
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Gene flow is more likely to alter allele frequencies directly compared to mutation.
Gene flow is more likely to alter allele frequencies directly compared to mutation.
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What is relative fitness in the context of natural selection?
What is relative fitness in the context of natural selection?
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What is the type of natural selection that favors individuals at one extreme of a phenotypic range?
What is the type of natural selection that favors individuals at one extreme of a phenotypic range?
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What type of natural selection favors individuals at both extremes of a phenotypic range?
What type of natural selection favors individuals at both extremes of a phenotypic range?
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What type of natural selection favors intermediate phenotypes?
What type of natural selection favors intermediate phenotypes?
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What is speciation?
What is speciation?
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Microevolution is a change in allele frequencies within a population, while macroevolution refers to evolution across species levels.
Microevolution is a change in allele frequencies within a population, while macroevolution refers to evolution across species levels.
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What is the biological species concept?
What is the biological species concept?
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Which of the following is NOT a type of reproductive isolation?
Which of the following is NOT a type of reproductive isolation?
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Postzygotic barriers prevent the formation of a hybrid zygote, while prezygotic barriers hinder the survival or fertility of hybrid offspring.
Postzygotic barriers prevent the formation of a hybrid zygote, while prezygotic barriers hinder the survival or fertility of hybrid offspring.
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Describe allopatric speciation.
Describe allopatric speciation.
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Polyploidy involves the duplication of the entire set of chromosomes, leading to increased ploidy levels.
Polyploidy involves the duplication of the entire set of chromosomes, leading to increased ploidy levels.
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What is a hybrid zone?
What is a hybrid zone?
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Hybrids often have reduced fitness compared to their parent species, which can lead to either reinforcement or fusion of the species.
Hybrids often have reduced fitness compared to their parent species, which can lead to either reinforcement or fusion of the species.
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Which of the following is NOT a possible outcome of two closely related species interacting in a hybrid zone?
Which of the following is NOT a possible outcome of two closely related species interacting in a hybrid zone?
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Reinforcement in a hybrid zone occurs when natural selection favors individuals who mate within their own species, strengthening reproductive isolation.
Reinforcement in a hybrid zone occurs when natural selection favors individuals who mate within their own species, strengthening reproductive isolation.
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Fusion in a hybrid zone happens when reproductive barriers weaken, leading to the eventual merging of the two species.
Fusion in a hybrid zone happens when reproductive barriers weaken, leading to the eventual merging of the two species.
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The punctuated equilibrium model of evolution suggests that species undergo long periods of stasis, punctuated by brief bursts of rapid change.
The punctuated equilibrium model of evolution suggests that species undergo long periods of stasis, punctuated by brief bursts of rapid change.
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Evolution is a directed process that always aims to create "perfect" organisms.
Evolution is a directed process that always aims to create "perfect" organisms.
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Study Notes
Evolution Theories, Mechanisms, and Relevance
- Evolutionary thought developed over time.
- Current species are descendants of ancestral species.
- Evolution is defined as descent with modification.
- Evolution is viewed as both a pattern and a process.
Origins of Evolutionary Ideas
- A new era in biology began in 1859 when Charles Darwin published The Origin of Species.
- Darwin focused on the diversity of organisms.
- Darwin's concept: current species are descendants of ancestral species.
- Evolution can be viewed as descent with modification.
Important Names in Evolution
- Linnaeus founded taxonomy, the science of classifying organisms.
- Paleontology, the science of fossils, was developed by Georges Cuvier, a French scientist.
- Fossils are remains of organisms from the past, often found in sedimentary rock layers (strata).
- Lamarck proposed a hypothesis that species evolve through use and disuse of body parts, and that characteristics acquired during an organism's life can be passed to offspring.
Darwin's Focus on Adaptation
- Darwin's interest in the geographic distribution of species was sparked by his observations on the Galapagos Islands.
- Darwin understood adaptation to the environment as a factor in the origin of new species.
- Recent biologists concluded that speciation occurred in the Galapagos finches.
On the Origin of Species
- Darwin developed two main ideas: descent with modification and Natural Selection.
- Darwin recognized that humans modify other species through artificial selection (selective breeding).
- Darwin drew two inferences from his observations of nature.
Darwin's Observations
- Observation 1: Members in a population often vary greatly in their traits.
- Observation 2: Traits are inherited from parents to offspring.
- Observation 3: All species are capable of producing more offspring than the environment can support.
- Observation 4: Overproduction leads to competition for resources.
- The individuals with favorable traits are more likely to survive and reproduce.
Inferences: Descent with Modification
- Inference 1: Individuals with heritable traits that enhance their survival and reproduction are more likely to leave more offspring than other individuals.
- Inference 2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in a population over generations.
- Darwin was influenced by Thomas Malthus's theory about human population growth exceeding resource availability.
Evidences of Evolution
- Biogeography, fossil records, DNA sequences, homology, and embryology are evidence of evolution.
Fossils
- Fossils demonstrate that life on Earth has changed over time.
- Paleontologists use fossil dating methods (e.g., carbon dating) to determine the age of fossils and understand evolutionary relationships.
Anatomical and Molecular Homologies
- Homology is similarity resulting from common ancestry.
- Homologous structures (anatomical resemblances) represent variations on a structural theme present in a common ancestor.
Comparative Embryology and Vestigial Structures
- Embryos of different species often share similarities.
- Vestigial structures are remnants of features that served important functions in the organism's ancestors.
Convergent Evolution
- Convergent evolution occurs when unrelated species independently evolve similar traits in response to similar environments.
- Similar traits often result due to similar adaptations needed in similar environments.
Biogeography
- Darwin's observations on the geographic distribution of species were important to his theory of evolution.
- Islands often have endemic species – unique species found only in that geographic location.
Mechanisms of Evolution
- Artificial and natural selection, genetic drift, and mutation are the mechanisms of evolution.
Overview: The Smallest Unit of Evolution
- Natural selection acts on individuals, but only populations evolve.
- Populations vary genetically; these variations contribute to evolution.
- Microevolution is change in allele frequencies within a population over generations.
- Two processes (mutation and sexual reproduction) contribute to genetic variation among individuals.
Mutation
- Mutations are changes in the nucleotide sequence of DNA.
- Mutations create new genes and alleles.
- Only mutations in gametes can be passed to offspring.
- Point mutations are changes in a single base pair in a gene.
Sexual Reproduction
- Sexual reproduction shuffles existing alleles into new combinations.
- Recombination is more important than mutation in producing genetic variation in sexually reproducing organisms.
Hardy-Weinberg Equilibrium
- Shows that allele frequencies in a population will remain constant (not evolve) in the absence of these 5 influences:
- No mutations, random mating, no natural selection, extremely large population size, no gene flow.
Natural Selection, Genetic Drift, and Gene Flow
- Natural selection, genetic drift, and gene flow alter allele frequencies in a population.
- Natural Selection: Differential reproductive success leads to certain alleles being passed on, favoring individuals more suited for the environment.
- Genetic drift: Random changes in allele frequencies, particularly significant in small populations.
- Gene flow: Movement of alleles between populations through migration, increasing genetic similarities.
- Founder effect and bottleneck effect are special cases of genetic drift.
More on Genetic Drift
- The founder effect occurs when a small group of individuals establishes a new, isolated population, which can have different allele frequencies from the original population.
- The bottleneck effect occurs when a large population is drastically reduced in size by an event; the surviving population may have a different allele frequency than the original.
Gene Flow
- Gene flow is the movement of alleles between populations through migration.
- Alleles can be transferred by the movement of gametes (e.g., pollen) or by movement of individuals.
Natural Selection: Relative Fitness
- The subtle contributions of individuals to the next generation's gene pool define relative fitness.
- Selection favors specific genotypes through the phenotypes of organisms.
- Directional, disruptive, and stabilizing selection are different types of natural selection.
Speciation, Microevolution, and Macroevolution
- Speciation is the origin of new species; it's a central focus of evolutionary theory.
- The process must explain how new species originate, and how populations evolve.
- Microevolution is adaptation within a population; it is confined to a single gene pool.
- Macroevolution refers to evolutionary changes above the species level.
The Biological Species Concept
- Biologists look at morphology, physiology, biochemistry, and DNA to group organisms.
- The biological species concept defines a species as a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring.
Reproductive Isolation
- Reproductive isolation (i.e. barriers) are factors that prevent different species from successfully interbreeding.
- Prezygotic barriers occur before the formation of a zygote, preventing mating or preventing fertilization.
- Postzygotic barriers occur after the zygote is formed, leading to reduced viability or fertility of hybrids.
Speciation by Geographic Separation
- Speciation can occur whether or not populations are geographically separated.
- Allopatric speciation occurs when geographic barriers separate populations.
- Sympatric speciation occurs in the absence of geographic barriers.
Allopatric vs. Sympatric Speciation
- Allopatric speciation (different country): Geographic isolation separates populations.
- Sympatric speciation: Speciation takes place within a population's existing range; often due to polyploidy. Polyploidy occurs when an organism has more than two sets of chromosomes.
Hybrid Zones
- Hybrid zones are regions where members of closely related species meet and interbreed.
- Hybrids sometimes have reduced fitness (reduced survival or reproduction rates) compared to parent species.
The Time Course of Speciation:
- Broad patterns of speciation can be seen in fossil records and/or molecular data.
- Fossil records often reveal stasis (no change) for long periods interspersed with brief periods of rapid change.
Why can't evolution create perfect organisms?
- Evolutionary changes are constrained by previous adaptations, historical constraints, and compromise (e.g., organisms may not be perfectly adapted for all situations).
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