AP Biology Unit 7: Evolution

Introduction

• Focus on evolution, a key aspect of biology.
• Evolution covers biological changes over hundreds of millions to billions of years.
• Key topics: Selection, Population Genetics, Speciation, Variation, Extinction, Phylogeny, and Origin of Life.

Types of Selection

Natural Selection

• Developed by Charles Darwin.
• Based on inherited variation, survival advantages, and adaptation.
• Examples include genetic traits like camouflage in animals.

Artificial Selection

• Also known as selective breeding.
• Humans select traits over many generations.
• Examples: Brassica oleracea (cauliflower, broccoli) and dog breeds.

Sexual Selection

• Traits that increase reproductive success.
• Leads to sexual dimorphism and behaviors like mate choice.
• Types include intersexual selection (e.g., peacocks) and intrasexual selection (e.g., elephant seals).

Population Genetics

Hardy-Weinberg Equilibrium

• Describes genetic variation in ideal populations.
• Conditions include no mutation, random mating, no gene flow, infinite size, no selection.
• Equations: (p + q = 1) and (p^2 + 2pq + q^2 = 1).

Genetic Drift

• Random changes in allele frequency, significant in small populations.
• Includes bottleneck effect and founder effect.

Gene Flow and Mutation

• Movement of alleles between populations.
• Mutation introduces genetic variation, crucial for evolution.

Evidence of Evolution

Homologous Traits

• Similar structures from a common ancestor.
• Adaptive radiation explains diversity.

Analogous Traits

• Similar function, different evolutionary origin.
• Result from convergent evolution.

Molecular Homologies

• Genetic similarities indicate common ancestry.
• Pseudogenes as evidence of evolution.

Biogeography and Fossils

• Geographic distribution and fossil records support evolutionary theory.
• Relative and absolute dating methods.

Speciation and Extinction

Speciation

• Biological species concept: reproductive isolation defines species.
• Mechanisms: prezygotic (e.g., behavioral, temporal) and postzygotic (e.g., hybrid sterility).
• Modes: allopatric (geographic isolation) and sympatric (no geographic barrier).

Extinction

• Normal and mass extinctions shape biodiversity.
• Human activities contributing to current mass extinction.

Phylogeny

Phylogenetic Trees

• Diagrams showing evolutionary relationships based on evidence.
• Terms: clades, nodes, sister groups, outgroups.

Molecular Clocks

• Use mutation rates to estimate divergence times between species.

Origin of Life

Key Steps

1. Formation of a stable planet.
2. Abiotic synthesis of organic molecules.
3. Formation of polymers and protocells.
4. Emergence of self-replicating cells.

RNA World Hypothesis

• RNA as the first genetic material, capable of self-replication and catalysis.

Miller-Urey Experiment

• Demonstrated abiotic synthesis of amino acids.

Study and Exam Preparation

• Utilize resources like Learn-Biology.com for interactive learning and exam reviews.
• Understanding evolutionary processes is crucial for success in AP Biology.