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Questions and Answers
What are the two main observations that form the basis of Darwin's theory of natural selection?
What are the two main observations that form the basis of Darwin's theory of natural selection?
- Traits are determined solely by environmental factors, and population size is limited by resource availability.
- Traits are heritable, and more offspring are produced than can survive. (correct)
- Traits are selectively bred by humans, and the environment has no impact on survival.
- Traits are acquired during an organism's lifetime and passed on, and genetic diversity remains constant.
Which of the following best describes an adaptation in the context of natural selection?
Which of the following best describes an adaptation in the context of natural selection?
- A characteristic that is intentionally bred into domesticated plants and animals by humans.
- A characteristic acquired during an organism's lifetime in response to environmental pressures.
- An inherited characteristic that enhances an organism's survival and reproduction in a specific environment. (correct)
- A random change in an organism's DNA that provides no advantage or disadvantage.
What is the primary difference between natural selection and artificial selection?
What is the primary difference between natural selection and artificial selection?
- Natural selection only affects wild populations, while artificial selection only affects domesticated species.
- Natural selection is driven by environmental factors, while artificial selection is driven by human preferences. (correct)
- Natural selection leads to evolutionary change, while artificial selection does not.
- Natural selection results in adaptations that enhance survival, while artificial selection always results in decreased fitness.
What is the eventual result of competition for limited resources in a population?
What is the eventual result of competition for limited resources in a population?
Which statement best describes the target of evolution?
Which statement best describes the target of evolution?
What is the correct definition of 'evolution'?
What is the correct definition of 'evolution'?
Which condition would likely lead to a decrease in genetic diversity within a population?
Which condition would likely lead to a decrease in genetic diversity within a population?
What is the role of mutations in the process of evolution?
What is the role of mutations in the process of evolution?
Which of the following is the MOST accurate description of genetic drift?
Which of the following is the MOST accurate description of genetic drift?
Why is genetic drift MOST significant in small populations?
Why is genetic drift MOST significant in small populations?
A forest fire drastically reduces the size of a deer population. By chance, the surviving deer have a higher frequency of a rare coat color allele than the original population. Which of the following does this exemplify?
A forest fire drastically reduces the size of a deer population. By chance, the surviving deer have a higher frequency of a rare coat color allele than the original population. Which of the following does this exemplify?
A small group of birds colonizes a new island. The allele frequencies in this new population are different from the allele frequencies in the original population. This is an example of:
A small group of birds colonizes a new island. The allele frequencies in this new population are different from the allele frequencies in the original population. This is an example of:
Which of the following describes microevolution?
Which of the following describes microevolution?
What factors drive microevolution?
What factors drive microevolution?
What is the definition of gene flow?
What is the definition of gene flow?
Pollen from a population of red flowers is carried by the wind to a population of white flowers, resulting in some offspring with pink flowers. Which evolutionary mechanism does this scenario best illustrate?
Pollen from a population of red flowers is carried by the wind to a population of white flowers, resulting in some offspring with pink flowers. Which evolutionary mechanism does this scenario best illustrate?
How is reproductive success measured in the context of natural selection?
How is reproductive success measured in the context of natural selection?
What is the effect of directional selection on the phenotype distribution of a population?
What is the effect of directional selection on the phenotype distribution of a population?
Which scenario is an example of stabilizing selection?
Which scenario is an example of stabilizing selection?
What is the result of disruptive selection on the phenotypic distribution of a population?
What is the result of disruptive selection on the phenotypic distribution of a population?
How can sexual selection lead to traits that are harmful to survival?
How can sexual selection lead to traits that are harmful to survival?
Which of these best describes sexual selection?
Which of these best describes sexual selection?
What is the Hardy-Weinberg equilibrium used to assess?
What is the Hardy-Weinberg equilibrium used to assess?
According to the Hardy-Weinberg principle, what condition must be met for the frequencies of alleles and genotypes in a population to remain constant from generation to generation?
According to the Hardy-Weinberg principle, what condition must be met for the frequencies of alleles and genotypes in a population to remain constant from generation to generation?
What is a key assumption of the Hardy-Weinberg equilibrium?
What is a key assumption of the Hardy-Weinberg equilibrium?
A population is in Hardy-Weinberg equilibrium. What can be inferred about this population?
A population is in Hardy-Weinberg equilibrium. What can be inferred about this population?
What are the 5 conditions for Hardy-Weinberg equilibrium?
What are the 5 conditions for Hardy-Weinberg equilibrium?
Which evolutionary mechanisms would cause microevolution to occur if one of the conditions for the Hardy-Weinberg equilibrium are not met?
Which evolutionary mechanisms would cause microevolution to occur if one of the conditions for the Hardy-Weinberg equilibrium are not met?
In the Hardy-Weinberg equation, what does the term 'p' represent?
In the Hardy-Weinberg equation, what does the term 'p' represent?
In a population, the frequency of the recessive allele (q) is 0.3. According to the Hardy-Weinberg equation, what is the frequency of the dominant allele (p)?
In a population, the frequency of the recessive allele (q) is 0.3. According to the Hardy-Weinberg equation, what is the frequency of the dominant allele (p)?
In a population of butterflies, the allele for white coloration (b) is recessive to the allele for brown coloration (B). If 16% of the butterflies are white, what is the frequency of the recessive allele (b)?
In a population of butterflies, the allele for white coloration (b) is recessive to the allele for brown coloration (B). If 16% of the butterflies are white, what is the frequency of the recessive allele (b)?
In a population of frogs, the allele for green skin (G) is dominant to the allele for brown skin (g). If the frequency of the homozygous recessive genotype (gg) is 0.09, what is the frequency of the heterozygous genotype (Gg)?
In a population of frogs, the allele for green skin (G) is dominant to the allele for brown skin (g). If the frequency of the homozygous recessive genotype (gg) is 0.09, what is the frequency of the heterozygous genotype (Gg)?
For a particular gene, the allele frequencies are: A = 0.6 and a = 0.4. What would be the frequency of heterozygous individuals assuming Hardy-Weinberg equilibrium?
For a particular gene, the allele frequencies are: A = 0.6 and a = 0.4. What would be the frequency of heterozygous individuals assuming Hardy-Weinberg equilibrium?
A population of birds has two alleles for feather color: brown (B) and yellow (b). Scientists determine that the frequency of the homozygous recessive genotype (bb) is 0.04. Assuming Hardy-Weinberg equilibrium, what percentage of the bird population is heterozygous (Bb)?
A population of birds has two alleles for feather color: brown (B) and yellow (b). Scientists determine that the frequency of the homozygous recessive genotype (bb) is 0.04. Assuming Hardy-Weinberg equilibrium, what percentage of the bird population is heterozygous (Bb)?
What is the significance of genetic diversity within a population?
What is the significance of genetic diversity within a population?
What is the primary risk for a species with low genetic diversity?
What is the primary risk for a species with low genetic diversity?
The California Condor population was drastically reduced due to poaching and poisoning. Although restoration efforts have increased their numbers, what is a major concern regarding the current population?
The California Condor population was drastically reduced due to poaching and poisoning. Although restoration efforts have increased their numbers, what is a major concern regarding the current population?
What does it mean when a population is referred to as a 'null mode of evolution'?
What does it mean when a population is referred to as a 'null mode of evolution'?
A population of birds displays significant variation in beak size, with some having very large beaks and others very small beaks. Over time, the birds with average-sized beaks become more common. What mode of natural selection does this scenario exemplify?
A population of birds displays significant variation in beak size, with some having very large beaks and others very small beaks. Over time, the birds with average-sized beaks become more common. What mode of natural selection does this scenario exemplify?
In a population of snails, shell color is determined by a single gene with two alleles: brown (B) and yellow (b). After several generations, scientists observe an increase in the frequency of brown shells. What is the MOST likely cause of this change in allele frequency?
In a population of snails, shell color is determined by a single gene with two alleles: brown (B) and yellow (b). After several generations, scientists observe an increase in the frequency of brown shells. What is the MOST likely cause of this change in allele frequency?
A farmer selectively breeds cows that produce the most milk. After several generations, the average milk production in the herd has increased significantly. How might this artificial selection affect the genetic diversity of the cow population?
A farmer selectively breeds cows that produce the most milk. After several generations, the average milk production in the herd has increased significantly. How might this artificial selection affect the genetic diversity of the cow population?
Consider a plant population where flower color is determined by a single gene with two alleles: red (R) and white (r). A researcher observes that the allele frequencies remain constant over several generations. Which conclusion can be drawn?
Consider a plant population where flower color is determined by a single gene with two alleles: red (R) and white (r). A researcher observes that the allele frequencies remain constant over several generations. Which conclusion can be drawn?
A population of fish in a newly formed lake initially consists of individuals with a wide range of body sizes. Over time, the lake's primary predator develops a preference for catching and consuming the larger fish. Which outcome is MOST likely to occur in the fish population over several generations?
A population of fish in a newly formed lake initially consists of individuals with a wide range of body sizes. Over time, the lake's primary predator develops a preference for catching and consuming the larger fish. Which outcome is MOST likely to occur in the fish population over several generations?
Flashcards
Heritable Traits
Heritable Traits
Traits passed from parent to offspring.
Adaptations
Adaptations
Inherited characteristics enhancing survival and reproduction.
Differential Survival
Differential Survival
Survival and reproduction differences due to varied traits.
Artificial Selection
Artificial Selection
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Evolution
Evolution
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Population
Population
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Gene Pool
Gene Pool
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Fixed Allele
Fixed Allele
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Mutations
Mutations
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Genetic Drift
Genetic Drift
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Bottleneck Effect
Bottleneck Effect
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Founder Effect
Founder Effect
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Microevolution
Microevolution
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Gene Flow
Gene Flow
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Relative fitness
Relative fitness
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Directional Selection
Directional Selection
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Stabilizing Selection
Stabilizing Selection
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Disruptive Selection
Disruptive Selection
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Sexual Selection
Sexual Selection
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Hardy-Weinberg Equilibrium
Hardy-Weinberg Equilibrium
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Hardy-Weinberg Principle
Hardy-Weinberg Principle
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Conditions for Hardy-Weinberg Equilibrium
Conditions for Hardy-Weinberg Equilibrium
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Hardy-Weinberg Equations
Hardy-Weinberg Equations
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Population genetic diversity
Population genetic diversity
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Study Notes
Natural Selection
- The theory of natural selection relies on Darwin's observations
- Traits are heritable, meaning they are passed down
- More offspring are produced than can survive
Heritable Traits
- Characteristics are passed down from parent to offspring
- Adaptations are inherited characteristics that enhance survival and reproduction
Offspring and Survival
- More offspring than resources leads to competition and differential survival
- Traits leading to survival accumulate in populations
- Populations evolve, not individuals
Artificial Selection
- Artificial selection is the selective breeding of domesticated plants/animals
- The goal is to encourage desirable traits
- Darwin used natural selection to compare to artificial selection
Natural Selection vs. Artificial Selection
- Natural selection is where nature "selects" traits for survival and reproduction
- Artificial selection is where humans select desirable traits
Evolution
- Evolution is a change in the genetic makeup of a population over time
- It involves descent with modification
Population Genetics
- A population is a group of the same species in an area that interbreed, producing fertile offspring
- A gene pool is a population's genetic makeup
- The gene pool consists of all copies of every type of allele
- Fixed alleles occur when only one allele is present at a locus
- Many fixed alleles result in decreased genetic diversity
Mutations
- Mutations are a source of genetic variation, forming new alleles
- Natural selection can act on varied phenotypes
- Mutation rates are slower in plants/animals, and faster in prokaryotes
- Prokaryotes have faster mutation times due to quicker generation times
- Mutations can be harmful, neutral, or beneficial
- Most mutations are neutral to harmful, and mutations do not always lead to evolution
Genetic Drift
- Genetic drift involves chance events altering allele frequency from one generation to the next
- It is significant in small populations and can lead to a loss of genetic variation
- Harmful alleles can become fixed by genetic drift
- Genetic drift does not produce adaptations
- The two types of genetic drift are bottleneck effect and founder effect
Bottleneck Effect
- The bottleneck effect occurs when a large population is drastically reduced by a non-selective disaster
- Examples of bottleneck events include floods, famine, fires, hurricanes, and hunting
- During a bottleneck, some alleles may become overrepresented, underrepresented, or even absent
Founder Effect
- The founder effect occurs when a few individuals become isolated from a large population to establish a new, small population
- The new population has a gene pool that differs from the original population
- Founder effect leads to a loss of genetic diversity
Population Genetics (cont.)
- A population's allele frequencies change over time
- Remember, populations evolve, not individuals
- Microevolution involves small-scale genetic changes in a population
- Random occurrences drive evolution
- Mutations, genetic drift, migration/gene flow, and natural selection are random occurrences
Gene Flow
- Gene flow is the transfer of alleles into or out of a population
- This occurs due to fertile individuals or gametes
- Alleles can be transferred between populations
- Pollen blown to a new location is an example
Scenario 1
- Black robins on the Chatham Islands in New Zealand faced habitat loss and predators
- The population declined to 5 individuals
- Conservation efforts increased the population to 230 individuals
- This is an example of the bottleneck effect due to human activity
Scenario 2
- An Amish population settled in Pennsylvania in the 1720s
- A small number of settlers from Germany carried mutations, including polydactyly
- Polydactyly is now more common in the Amish population
- This is an example of the founder effect
Scenario 3
- Recurrent flash floods caused mortalities in a marble trout population
- The scientists analyzed the genetic makeup of the remaining marble trout
- Genetic diversity decreased significantly
- This is an example of the bottleneck effect
Scenario 4
- Increased wind caused pollen to travel further and pollinate another flower population
- The offspring have traits of each population
- This is an example of gene flow
Natural Selection (cont.)
- Reproductive success is measured by relative fitness
- Relative fitness is the number of surviving offspring an individual produces compared to others
- The effects of natural selection can be measured by analyzing changes in mean phenotypes
- The three modes of natural selection are directional, stabilizing, and disruptive selection
Modes of Natural Selection
- In directional selection, selection favors one extreme phenotype
- Stabilizing Selection has selection towards the population mean and against extreme phenotypes
- In disruptive selection, selection is against the mean, and both phenotypic extremes have high relative fitness
Natural Selection (cont.)
- Sexual selection is a type of natural selection explaining unique/showy traits
- Males often have useless structures (e.g., peacock feathers)
- These structures form because females choose that trait
- Sexual selection can produce traits harmful to survival
- An example is that colorful peacock feathers make males easier for predators to spot
Hardy-Weinberg Equilibrium
- The Hardy-Weinberg Equilibrium is a model to assess whether natural selection is causing evolution at a locus
- It determines the genetic makeup if the population was not evolving and then compare to actual data
- If there is no difference, the population is not evolving
- If there are differences, the population may be evolving
Hardy-Weinberg Principle
- Allele and genotype frequencies in a population remain constant from generation to generation
- The only condition is that Mendelian segregation and recombination of alleles are at work
- This is a hypothetical situation where no evolution occurs
- Allele and genotype frequencies do change over time in real populations
Hardy-Weinberg Conditions
- Five conditions must be met for Hardy-Weinberg equilibrium
- No mutations, random mating, no natural selection, extremely large population size, and no gene flow
- If any conditions are not met, microevolution occurs
- This includes mutation, gene flow, genetic drift, natural selection, and non-random mating
Hardy-Weinberg Formulas
- Two formulas are used for Hardy-Weinberg equilibrium
- p + q = 1 determines the frequency of the dominant (p) and recessive (q) alleles in a population
- p² + 2pq + q² = 1 determines the percentage of homozygous dominant (p²), heterozygous (2pq), and homozygous recessive (q²) individuals
Hardy-Weinberg Tips
- Start with either formula depending on what info is given in each problem
- "allele frequencies" refers to p and q
- Information about an organism refers to p², 2pq, and q²
- Both formulas are often needed to complete many of the problems
- Usually, you are given ‘q’, then you need to find ‘p’
Solving Problems Tips
- Always write down both equations for hardy-weinberg
- Identify information given for alleles or populations
- Solve for both p and q first, regardless of what the problem asks
- Use a calculator to do the square and square root functions
- Double check your work
Practice Problem #1
- You have found that 36% are homozygous recessive aa
- To find frequencies of A and a alleles use p + q = 1 with q² = 0.36
- √q² = 0.6
- p + 0.6 =1
- p = 0.4
Practice Problem #2
- 10% of a population of mice are albino, recessive to tan coloring
- You need to find the frequency of the homozygous dominant and heterozygous
- q²= 0.10
- √(0. 10)= 0.32
- p = 0.68
- p²=0.46
- 2pq: 2(.68)(.32)= 0.44
- p² + 2pq + q² = 1
- 0.46 +0.44 + 0.1 = 1
Variations in Populations
- Genetic diversity in a population helps the population respond to environmental changes
- Species with low genetic diversity risk decline and/or extinction
- California Condors experienced a population reduction to 27 individuals due to poaching/poisoning
- This drastically lowered their gene pool and diversity
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