AP Biology Unit 7: Evolution

Introduction

• Evolution is a core topic in AP Biology.
• It covers biological changes over millions of years.

Topics Covered

1. Selection
   • Natural Selection
   • Artificial Selection
   • Sexual Selection
2. Population Genetics
   • Hardy-Weinberg Equilibrium
3. Evidence for Evolution
   • Speciation
   • Extinction
   • Phylogeny
   • Origin of Life

Types of Selection

Natural Selection

• Developed by Charles Darwin.
• Based on inherited variation and survival of the fittest.
• Adaptations arise through recombination and mutation.

Artificial Selection

• Also known as selective breeding.
• Humans breed plants/animals for desired traits.
• Example: Brassica oleracea (cauliflower, broccoli) and dog breeds.

Sexual Selection

• Selection for traits that increase reproductive success.
• Intersexual: Mate choice (e.g., peacocks).
• Intrasexual: Competition (e.g., elephant seals).

Selection Effects

• Directional Selection: Favors one extreme phenotype.
• Stabilizing Selection: Favors average phenotype.
• Disruptive Selection: Favors multiple extreme phenotypes.

Population Genetics and Hardy-Weinberg Equilibrium

Population Genetics

• Studies gene distribution and changes over time.
• Gene pool: All alleles in a population.

Hardy-Weinberg Equilibrium

• Conditions: Large population, no selection, random mating, no migration, no mutation.
• Equations: p + q = 1 and p² + 2pq + q² = 1.

Genetic Drift

• Random changes in allele frequencies due to small population size.
• Bottleneck Effect: Drastic reduction in population size.
• Founder Effect: New population started by a small group.

Gene Flow and Mutation

• Gene Flow: Movement of alleles between populations.
• Mutation: Source of genetic variation.

Evidence of Evolution

Homologous Traits

• Traits from a common ancestor, e.g., limb structures.

Vestigial Structures

• Remnants of features from ancestors.

Analogous Features

• Similar function, different origin due to convergent evolution.

Molecular Homologies

• Genetic similarities indicating common ancestry.

Fossils

• Show evolutionary change over time.

Biogeography

• Study of species distribution supports evolutionary theory.

Speciation and Extinction

Biological Species Concept

• Species: Group that can interbreed to produce fertile offspring.

Reproductive Isolation

• Prezygotic: Prevents mating.
• Postzygotic: Prevents hybrid success.

Types of Speciation

• Allopatric: Geographic isolation.
• Sympatric: Speciation without geographic isolation.

Mass Extinction

• Rapid decrease in biodiversity, leading to adaptive radiations.

Phylogeny

Phylogenetic Trees

• Diagram showing evolutionary relationships.
• Built using morphological and genetic data.

Key Definitions

• Clade: Common ancestor and all descendants.
• Shared Derived Character: Trait that defines a clade.

Molecular Clocks

• Mutation rate estimation to infer evolutionary timelines.

Origin of Life

Key Steps to Life

1. Formation of a stable planet.
2. Abiotic synthesis of organic molecules.
3. Formation of polymers and vesicles.
4. Emergence of self-replicating RNA.
5. Development of Proto-cells.

Miller-Urey Experiment

• Simulated early Earth conditions and synthesized amino acids.

Study Tips

• Focus on key concepts in each section.
• Utilize online resources for interactive learning.
• Understand examples like the peppered moth and sickle cell anemia.

These notes summarize key points from the AP Biology Unit 7 on Evolution, focusing on selection, genetics, evidence for evolution, speciation, and origin of life.