AP Bio - Macroevolution

AP Biology Macroevolution Study Guide

Table of Contents:

1. Mechanisms for Speciation

2. Prezygotic and Postzygotic Barriers

3. Evidence for Evolution

4. Phylogeny Vocabulary Terms

5. Darwin’s Observations

6. Significance of Oxygen

7. RNA World Hypothesis

8. Miller-Urey Experiment

9. Endosymbiotic Theory

1. Mechanisms for Speciation

• Speciation: The process by which new species arise.

• Allopatric Speciation:

Occurs when populations are geographically separated, leading to the formation of new species.

• Sympatric Speciation:

Occurs within the same geographic area, often due to:

• Habitat Differentiation: Different parts of the same habitat may favor different traits.

• Polyploidy: Having extra sets of chromosomes, common in plants, which can lead to reproductive isolation.

• Chromosome Mutations: Changes in chromosome structure that can prevent successful interbreeding.

2. Prezygotic and Postzygotic Barriers

• Prezygotic Barriers: Prevent fertilization between different species.

• Examples:

  • Temporal isolation

  • Habitat isolation

  • Behavioral isolation

  • Mechanical isolation

  • Gametic isolation

  • Postzygotic Barriers: Occur after fertilization, reducing hybrid viability or fertility.

• Examples:

  • Reduced hybrid viability

  • Reduced hybrid fertility

  • Hybrid breakdown

3. Evidence for Evolution

• Key Sources of Evidence:

• Fossil Records: Show changes in species over time.

• Comparative Anatomy: Homologous and analogous structures.

• Embryology: Similar early development stages in different species.

• Biogeography: Geographic distribution of species.

• Molecular Biology: DNA and protein similarities.

4. Phylogeny Vocabulary Terms

• Phylogeny: The evolutionary history and relationship among species.

• Clade: A group of organisms that includes an ancestor and all its descendants.

• Monophyletic: A clade consisting of a single ancestral species and all its descendants.

• Paraphyletic: A group containing a common ancestor but not all its descendants.

• Polyphyletic: A group with members from different ancestral lines.

• Homologous Structures: Traits inherited from a common ancestor.

• Analogous Structures: Similar traits due to convergent evolution, not common ancestry.

5. Darwin’s Observations

1. Variation: Individuals within a population vary in their traits.

2. Branching: Species can diverge from a common ancestor over time.

3. Gradualism: Evolutionary changes occur slowly and gradually over long periods.

4. Natural Selection: Organisms better adapted to their environment tend to survive and reproduce.

6. Significance of Oxygen

• The Great Oxygenation Event:

  • Around 2.4 billion years ago, cyanobacteria started producing oxygen through photosynthesis, leading to the oxygenation of Earth’s atmosphere.

• Impact:

  • This allowed for aerobic respiration, leading to more energy-efficient organisms and eventually more complex life forms.

7. RNA World Hypothesis

• Proposes that life may have started with self-replicating RNA molecules before the evolution of DNA and proteins.

• Key Points:

  • RNA can store genetic information and act as a catalyst.

  • Early Earth conditions may have favored the formation of RNA.

8. Miller-Urey Experiment

• An experiment that simulated early Earth conditions to show how organic molecules like amino acids could form spontaneously.

• Key Components:

  • Water, methane, ammonia, and hydrogen were exposed to electrical sparks.

  • The experiment produced organic molecules, supporting the idea of abiogenesis (life arising from non-living matter).

9. Endosymbiotic Theory

• Proposes that eukaryotic cells evolved from a symbiotic relationship between early prokaryotic cells.

• Key Evidence:

  • Mitochondria and chloroplasts have their own DNA, similar to bacterial DNA.

  • Both organelles reproduce independently of the cell and have double membranes.

  • Ribosomes in mitochondria and chloroplasts resemble bacterial ribosomes.