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Questions and Answers
Which of the following is NOT a key component required for natural selection to occur?
Which of the following is NOT a key component required for natural selection to occur?
- Differential reproductive success based on traits
- A stable environment with no selective pressures (correct)
- Variation in traits within a population
- Heritability of traits from parents to offspring
What type of selection favors intermediate trait values, leading to a decrease in variation around the mean?
What type of selection favors intermediate trait values, leading to a decrease in variation around the mean?
- Artificial selection
- Disruptive selection
- Directional selection
- Stabilizing selection (correct)
Which process is an example of directional selection?
Which process is an example of directional selection?
- The prevalence of small and large sizes while the mean is selected against.
- The selective breeding of dogs for specific traits.
- The decreasing frequency of average-sized beaks in a bird population after a drought favors larger beaks. (correct)
- The maintenance of a consistent coat color in a mammal species over many generations.
What is the primary cause of human-induced evolution?
What is the primary cause of human-induced evolution?
Which of the following describes the evolutionary change observed in Darwin's finches on the Galapagos Islands?
Which of the following describes the evolutionary change observed in Darwin's finches on the Galapagos Islands?
How does the heritability of a trait influence the rate of evolution by natural selection?
How does the heritability of a trait influence the rate of evolution by natural selection?
What is the primary selective pressure that maintains intermediate gall sizes in goldenrod gall flies?
What is the primary selective pressure that maintains intermediate gall sizes in goldenrod gall flies?
What is the significance of the parallel evolution observed in three-spined sticklebacks?
What is the significance of the parallel evolution observed in three-spined sticklebacks?
Which genetic change is associated with the evolution of freshwater sticklebacks from marine sticklebacks?
Which genetic change is associated with the evolution of freshwater sticklebacks from marine sticklebacks?
What is an example of artificial selection?
What is an example of artificial selection?
How does trophy hunting impact the horn size of bighorn sheep populations?
How does trophy hunting impact the horn size of bighorn sheep populations?
What evolutionary adaptation has been observed in Australian black snakes in response to the introduction of cane toads?
What evolutionary adaptation has been observed in Australian black snakes in response to the introduction of cane toads?
Which of the following factors influences the speed of evolution?
Which of the following factors influences the speed of evolution?
What is the primary evolutionary pressure driving the increase in body size and leg length in cane toads in Australia?
What is the primary evolutionary pressure driving the increase in body size and leg length in cane toads in Australia?
Which of the following statements accurately describes the relationship between natural selection and adaptation?
Which of the following statements accurately describes the relationship between natural selection and adaptation?
In the context of natural selection, what does 'differential reproductive success' refer to?
In the context of natural selection, what does 'differential reproductive success' refer to?
If woodpeckers were removed from the goldenrod gall system, what would MOST likely happen?
If woodpeckers were removed from the goldenrod gall system, what would MOST likely happen?
Which of these is an example of humans driving evolutionary change?
Which of these is an example of humans driving evolutionary change?
What broader ecological concept did the study of sticklebacks in Loberg Lake exemplify?
What broader ecological concept did the study of sticklebacks in Loberg Lake exemplify?
Which condition must be met for natural selection to facilitate adaptation in a population?
Which condition must be met for natural selection to facilitate adaptation in a population?
How does the introduction of invasive species like cane toads illustrate the principles of natural selection?
How does the introduction of invasive species like cane toads illustrate the principles of natural selection?
What is the MOST likely long-term evolutionary outcome if trophy hunting continues to selectively remove bighorn sheep with the largest horns?
What is the MOST likely long-term evolutionary outcome if trophy hunting continues to selectively remove bighorn sheep with the largest horns?
How does considering both cane toad and black snake evolution in Australia deepen our understanding of evolutionary biology?
How does considering both cane toad and black snake evolution in Australia deepen our understanding of evolutionary biology?
What is the evolutionary significance of heritable traits?
What is the evolutionary significance of heritable traits?
How might the removal of parasitoid wasps from a goldenrod gall system affect the selective pressures on gall size?
How might the removal of parasitoid wasps from a goldenrod gall system affect the selective pressures on gall size?
How does commercial fishing impact the genetic makeup of Atlantic cod populations?
How does commercial fishing impact the genetic makeup of Atlantic cod populations?
In Loberg Lake, a shift from complete to low-armor phenotype occurred in sticklebacks in approximately 17 years. What does this rapid change suggest about the selective pressures in the new environment?
In Loberg Lake, a shift from complete to low-armor phenotype occurred in sticklebacks in approximately 17 years. What does this rapid change suggest about the selective pressures in the new environment?
An invasive species is introduced into a new environment with abundant resources and few predators. What evolutionary pattern would be expected in the invasive population?
An invasive species is introduced into a new environment with abundant resources and few predators. What evolutionary pattern would be expected in the invasive population?
What key insight can be gained from observing cane toad evolution alongside the evolution of predators such as the Australian black snake?
What key insight can be gained from observing cane toad evolution alongside the evolution of predators such as the Australian black snake?
What long-term evolutionary effect might result from commercial fishing practices that consistently harvest the largest Atlantic cod?
What long-term evolutionary effect might result from commercial fishing practices that consistently harvest the largest Atlantic cod?
In goldenrod gall fly populations, galls of intermediate size are favored due to opposing selection pressures from woodpeckers and parasitoid wasps. What type of selection is this an example of?
In goldenrod gall fly populations, galls of intermediate size are favored due to opposing selection pressures from woodpeckers and parasitoid wasps. What type of selection is this an example of?
Which factor is MOST crucial in determining the rate at which a population can adapt to a new selective pressure?
Which factor is MOST crucial in determining the rate at which a population can adapt to a new selective pressure?
What insight does comparing the cane toad adaptations with similar adaptations found in black snakes give us regarding species evolution within an environment?
What insight does comparing the cane toad adaptations with similar adaptations found in black snakes give us regarding species evolution within an environment?
How can human activities inadvertently reverse the effects of natural selection over relatively short time periods?
How can human activities inadvertently reverse the effects of natural selection over relatively short time periods?
How can the intensive harvesting of Atlantic cod in commercial fisheries lead to a reduction in the overall fitness of the population, aside from just reducing population size?
How can the intensive harvesting of Atlantic cod in commercial fisheries lead to a reduction in the overall fitness of the population, aside from just reducing population size?
Flashcards
Natural Selection
Natural Selection
Process requiring variation, heritability, and differential reproductive success.
Adaptation
Adaptation
Outcome of evolution by natural selection that improves fitness in specific environments.
Stabilizing Selection
Stabilizing Selection
Selection that favors intermediate trait values.
Directional Selection
Directional Selection
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Human-Induced Evolution
Human-Induced Evolution
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Requirements for Natural Selection
Requirements for Natural Selection
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Stabilizing Selection in Goldenrod Gall Flies
Stabilizing Selection in Goldenrod Gall Flies
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Parallel Evolution
Parallel Evolution
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Artificial selection
Artificial selection
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Invasive Species Evolution
Invasive Species Evolution
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Study Notes
- Natural Selection II Lecture took place on March 6, 2025.
- Continuation of discussion on natural selection (Chapter 10)
Objectives
- Understand the mechanisms and requirements of natural selection.
- Examine case studies demonstrating natural selection in action.
- Explore human impacts on evolutionary processes.
Key Concepts
- Natural Selection: Requires variation, heritability, and differential reproductive success.
- Adaptation: The outcome of evolution by natural selection improves fitness in specific environments.
- Stabilizing Selection: Favors intermediate trait values.
- Directional Selection: Favors one extreme of a trait.
- Human-Induced Evolution: Changes in population resulting from human activities.
Darwin's Finches and Evidence for Natural Selection
- Darwin's finches demonstrated natural selection in action.
- Medium ground finches (Geospiza fortis) shifted toward larger beaks after the 1977 drought.
- Beak size is heritable, demonstrated by parent-offspring regression
- Evolution occurs in small steps over generations with a 0.5mm shift in beak size in one generation
Requirements for Natural Selection
- Natural selection requires three key components:
- Variation: Population members must vary in traits (e.g., ladybird beetles with different colors).
- Inheritance: Variation must be heritable where offspring resemble parents
- Differential reproductive success: Some variants reproduce more than others.
- Only evolution by natural selection produces adaptation. Other forms of evolutionary change (mutation, drift, migration) change allele frequencies but don't lead to adaptation.
Stabilizing Selection in Goldenrod Gall Flies
- Opposing selective pressures maintain intermediate trait values.
- Eurosta solidaginis lays eggs in goldenrod stems, causing galls to form.
- Woodpeckers preferentially attack larger galls.
- Parasitoid wasps preferentially attack smaller galls (limited by ovipositor length).
- These opposing forces maintain intermediate gall sizes in the population.
- Stabilizing selection can result when agents of selection are acting in opposite directions
Three-Spined Sticklebacks and Parallel Evolution
- Similar environments produce similar evolutionary outcomes in independent populations.
- Marine sticklebacks have long spines and extensive armor plates.
- Freshwater sticklebacks have reduced spines and fewer armor plates.
- The gene EDA (ectodysplasin) is associated with these differences.
- The low-armor "L" allele increases in frequency in freshwater environments.
- Complete shift from complete to low-armor phenotype occurred in Loberg Lake in ~17 years.
- Populations that independently experience parallel environmental changes represent replicated natural experiments.
Human Induced Evolution
- Humans are powerful agents of evolutionary change.
- Artificial selection: Domestication transformed teosinte into modern corn over ~9,000 years.
- Pesticide resistance: Resistant individuals emerge within ~5 years of new pesticide introduction.
- Trophy hunting: Selected against large horn size in bighorn sheep.
- Commercial fishing: Selection for earlier maturation and smaller size in Atlantic cod.
Invasive Cane Toads in Australia
- Invasive species and their predators evolve rapidly in new environments.
- Cane toads introduced to Australia in 1940s spread rapidly without natural predators.
- They evolved larger body size and longer legs for greater dispersal.
- Australian black snakes evolved in response with larger bodies but smaller jaws to handle toxic toads.
- The speed of evolution depends on the amount of genetic variation that exists and the strength of selection.
- Selection favors the ability to be more mobile.
Summary
- Natural selection requires variation, inheritance, and differential reproductive success.
- Selection can be stabilizing or directional.
- Humans drive evolutionary change through domestication, pesticides, and harvesting.
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