#AP Biology: Natural Selection and Phenotypic Plasticity - Your Ultimate Review

Hey there, future AP Bio superstar! Let's get you prepped and confident for the exam. We're diving into natural selection and phenotypic plasticity, two key concepts that show how organisms adapt to their environment. Get ready to make some connections and ace this!

#Natural Selection: Survival of the Fittest 💪

#The Basics:

• Heritable Variation: Individuals within a population have different traits that can be passed down to offspring.
• Differential Reproductive Success: Some individuals with certain traits are more likely to survive and reproduce than others.
• Adaptation: Over time, the traits that lead to higher survival and reproduction become more common in the population.

#Genotype vs. Phenotype

• Genotype: An individual's genetic makeup (the specific alleles they carry).
• Alleles: Different versions of a gene.
• Phenotype: The physical expression of the genotype (the observable traits).

#Example: The Tale of the Mice 🐭

• Original Environment: Permafrost, light-colored mice have a survival advantage due to camouflage.
• Environmental Change: Permafrost melts, exposing dark volcanic soil.
• New Advantage: Dark-colored mice now have a survival advantage, leading to a shift in allele frequency.

#Phenotypic Plasticity: Adapting on the Fly 🦊

#Key Concepts:

• Same Genotype, Different Phenotype: Individuals with the same genetic makeup can look and behave differently in different environments.
• Ecological Niches: Phenotypic plasticity allows organisms to exploit a wider range of ecological niches.
• Adaptation: Helps organisms adapt to variable conditions.

#Factors Influencing Plasticity:

• Genetic Predisposition: Some organisms are more genetically programmed for plasticity than others.
• Environmental Conditions: The environment plays a huge role in determining the extent of plasticity.

#Example: The Arctic Fox ❄️☀️

• Winter: White coat for camouflage in the snow and ice.
• Summer: Brown/gray coat for camouflage in the tundra.

• Trigger: Changes in daylight regulate melatonin, which influences coat color.

#Connecting the Concepts 💡

• Natural Selection vs. Phenotypic Plasticity: Natural selection operates over generations, favoring certain heritable traits. Phenotypic plasticity allows for rapid, within-lifetime changes in response to the environment.
• Both are Adaptive: Both mechanisms help organisms survive and reproduce in changing environments, but they operate on different timescales and through different processes.

#Final Exam Focus 🎯

• High-Priority Topics: Natural selection, adaptation, genotype vs. phenotype, phenotypic plasticity, environmental influences on traits.
• Common Question Types: MCQs on interpreting scenarios, FRQs on explaining evolutionary processes, short answer questions on comparing and contrasting natural selection and plasticity.

#Last-Minute Tips:

• Time Management: Don't spend too long on any one question. Move on and come back if needed.
• Common Pitfalls: Misunderstanding the difference between genotype and phenotype. Not linking environmental changes to selective pressures. Forgetting that natural selection acts on existing variation.
• Strategies: Read questions carefully, underline key terms, and plan your FRQ responses before writing.

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Practice Question

Practice Questions

#Multiple Choice Questions

1. A population of birds exhibits variation in beak size. In a habitat where small seeds are abundant, which of the following is most likely to occur over time? a) Birds with larger beaks will become more common due to phenotypic plasticity. b) Birds with smaller beaks will become more common due to natural selection. c) Birds with intermediate beak sizes will become more common due to genetic drift. d) The beak size distribution will remain unchanged.

2. Which of the following best describes phenotypic plasticity? a) A change in the genetic makeup of a population over time. b) The ability of an organism to change its phenotype in response to environmental conditions. c) The process by which new species arise. d) The random changes in allele frequencies in a population.

#Free Response Question

A population of insects has two color variations: green and brown. Initially, the environment is mostly green vegetation, and the green insects are more common. Over time, the vegetation changes to mostly brown. Describe how natural selection and phenotypic plasticity could affect the insect population. Include the following in your response:

• The role of heritable variation.
• How differential reproductive success leads to adaptation.
• How phenotypic plasticity could influence the population.

Scoring Breakdown:

• Heritable Variation (1 point): Mention that the insect population has pre-existing genetic variation in color (green and brown).
• Natural Selection (2 points): Explain that in a brown environment, brown insects are better camouflaged, leading to higher survival and reproduction rates. Over time, the frequency of brown insects increases.
• Phenotypic Plasticity (2 points): Describe how some insects may exhibit phenotypic plasticity by changing their color to match the environment. Explain that this is a rapid response within an individual's lifetime, which is different from natural selection.
• Adaptation (1 point): Conclude that both natural selection and phenotypic plasticity are mechanisms that allow the insect population to adapt to the changing environment, but they do so in different ways.

#Combined Concepts Question:

How do the concepts of natural selection and phenotypic plasticity relate to the broader concept of evolution? Provide an example of how environmental change can drive both natural selection and phenotypic plasticity in a single population.