AP Biology Unit 7: Natural Selection

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AP BIOLOGY - UNIT 7: Natural Selection

• Weighting for AP Exam: 13-20%
• Class Periods: ~20-23

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Overview

• BIG IDEA 1: Evolution (EVO)
  • What conditions in a population affect its likelihood to evolve?
  • Defend the theory of evolution scientifically.
• BIG IDEA 4: Systems Interactions (SYI)
  • How do species interactions encourage or slow changes in species?

Important Insights to Unit 7

• Unit 7 expands on foundational concepts about natural selection, highlighting that populations better adapted to their environments are more likely to survive and reproduce.
• The unit includes:
  • Evidence for evolutionary change
  • Mechanisms of evolutionary change
  • Hardy-Weinberg equilibrium, predicting allele frequencies in nonevolving populations.
• Students will learn to analyze data regarding allele frequencies to conclude about population evolution.

Building Science Practices

• Opportunities to use visual models for biological processes, such as cladograms and phylogenetic trees, are included.
• Hardy-Weinberg equations help understand allele frequencies, emphasizing that these can change, vital for making evolutionary predictions.

Preparing for the AP Exam

• Natural selection language: Precise use of terminology without Lamarckian phrases is crucial.
  • Understand genetic variation's role in reproductive success.
• Differentiate reproductive isolating mechanisms leading to speciation.

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Unit Highlights

• Topics covered in Unit 7:
  1. Introduction to Natural Selection
  2. Natural Selection
  3. Artificial Selection
  4. Population Genetics
  5. Hardy-Weinberg Equilibrium
  6. Evidence of Evolution
  7. Common Ancestry
  8. Continuing Evolution
  9. Phylogeny
  10. Speciation
  11. Extinction
  12. Variations in Populations
  13. Origin of Life on Earth

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Topic 7.1: Introduction to Natural Selection

• Enduring Understanding (EVO-1): Evolution involves changes in genetic makeup over time, supported by evidence.
• Learning Objective (EVO-1.C): Describe the causes of natural selection.
  • Essential Knowledge:
  • Natural selection as a key mechanism of evolution.
  • Competition for resources leads to differential survival; favorable phenotypes survive, reproduce.
  • Evolutionary fitness is measured by reproductive success.
  • Environmental stability affects evolutionary rates.

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Understanding Natural Selection

• Define NATURAL SELECTION: Organisms with favorable traits prosper, leading to reproduction of viable offspring.
• Define EVOLUTIONARY FITNESS: Similar to natural selection; those with higher survival rates have more reproduction chances.

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Darwin's Theory of Natural Selection

• 5 Parts of Darwin's Theory:
  1. Variations in populations
  2. Some variations are more favorable
  3. Overproduction of offspring
  4. Adaptations leading to survival
  5. Gradualism: species evolve over time.

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Topic 7.2: Natural Selection

• Illustrative Examples:
  • Sickle cell anemia
  • DDT resistance in insects
  • Flowering time relative to global climate change
• Natural selection acts on phenotypic variations.

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Modes of Selection

• Select Pressure: Environmental factors favor certain traits
  • Types of Selection:
  • Directional selection
  • Stabilizing selection
  • Disruptive selection

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Topic 7.3: Artificial Selection

• Definition: Humans modify species through selective breeding.
• Convergent Evolution: Similar adaptations occur in response to similar selective pressures in different species.
  • Example: Dolphins and sharks share torpedo shapes.

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Topic 7.4: Population Genetics

• Understand how random occurrences affect gene makeup of a population.
• Evolution Drivers:
  • Mutations, genetic drift, and migration can alter allele frequencies.

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Topic 7.5: Hardy-Weinberg Equilibrium

• Conditions for Hardy-Weinberg equilibrium include large population size and random mating.
• Equations:
  p^2 + 2pq + q^2 = 1
  p + q = 1

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Topic 7.6: Evidence of Evolution

• Types of evidence supporting evolution include morphological, biochemical, and genetic evidence, as well as fossil records.
• Homologies indicate common ancestry.

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Topic 7.7: Common Ancestry

• Evidence for common ancestry across organisms includes membrane-bound organelles and linear chromosomes.

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Topic 7.8: Continuing Evolution

• Evolution is ongoing across all life forms, influenced by genomic changes and environmental pressures.

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Topic 7.9: Phylogeny

• Phylogenetic trees illustrate evolutionary relationships among species based on traits, both morphological and molecular.

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Topic 7.10: Speciation

• Speciation occurs under reproductive isolation, which can be allopatric (geographically isolated) or sympatric (in the same area).

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Topic 7.11: Extinction

• Factors leading to extinction include ecological stress and human activity.

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Topic 7.12: Variations in Populations

• Variations affect resilience to environmental pressures; populations with high genetic diversity are more stable.

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Topic 7.13: Origins of Life

• Evidence for life's origin includes geological evidence, chemical experiments, and the RNA world hypothesis.