BIO 101 Final Exam Study Guide: Evolution and the History of Life

Final Exam Overview

This study guide summarizes the key concepts for the BIO 101 final exam, focusing on evolutionary biology and the history of life on Earth. The exam will include cumulative content, with a special emphasis on material from Chapters 22, 23, 24, and 25.

Chapter 22 – Descent with Modification: A Darwinian View of Life

Key Concepts

• Charles Darwin: Developed the theory of evolution by natural selection.

• Evolution: The process by which species change over time through descent with modification.

• Natural Selection: Mechanism of evolution where individuals with advantageous traits survive and reproduce more successfully.

• Evidence for Evolution:

  • Direct Observation: Examples include antibiotic resistance in bacteria.

  • Homology: Similarities in structure due to shared ancestry (e.g., vertebrate forelimbs).

  • Fossil Record: Shows changes in species over time.

  • Biogeography: Geographic distribution of species supports evolutionary relationships.

Example: The finches of the Galápagos Islands demonstrate adaptive radiation, where a single ancestral species diversified into multiple species with different beak shapes.

Chapter 23 – The Evolution of Populations

Key Concepts

• Mechanisms of Evolution:

  • Mutation: Random changes in DNA that introduce genetic variation.

  • Microevolution: Small-scale changes in allele frequencies within a population.

  • Natural Selection: Differential survival and reproduction.

  • Genetic Drift: Random changes in allele frequencies, especially in small populations (e.g., bottleneck and founder effects).

  • Gene Flow: Movement of alleles between populations.

• Hardy-Weinberg Principle: Describes a non-evolving population. The equation is: $p^2 + 2pq + q^2 = 1$ where p and q are the frequencies of two alleles in a population.

• Types of Selection:

  • Directional Selection: Favors one extreme phenotype.

  • Disruptive Selection: Favors both extreme phenotypes.

  • Stabilizing Selection: Favors intermediate phenotypes.

• Adaptation: Inherited traits that enhance survival and reproduction.

Example: The peppered moth in England is a classic example of natural selection in response to environmental change.

Chapter 24 – Origin of Species

Key Concepts

• Speciation: The process by which one species splits into two or more species.

• Biological Species Concept: Defines species as groups of interbreeding natural populations that are reproductively isolated from other such groups.

• Reproductive Isolation: Barriers that prevent species from interbreeding.

  • Prezygotic Barriers: Prevent mating or fertilization (e.g., habitat isolation, temporal isolation, behavioral isolation, mechanical isolation, gametic isolation).

  • Postzygotic Barriers: Prevent hybrid offspring from developing into viable, fertile adults (e.g., reduced hybrid viability, reduced hybrid fertility, hybrid breakdown).

• Modes of Speciation:

  • Allopatric Speciation: Occurs when populations are geographically separated.

  • Sympatric Speciation: Occurs without geographic separation, often through polyploidy, habitat differentiation, or sexual selection.

• Hybrid Zones: Regions where different species meet and mate, producing hybrids. Outcomes include reinforcement, fusion, or stability.

Example: The formation of new species of cichlid fish in African lakes due to sexual selection and ecological differentiation.

Chapter 25 – History of Life on Earth

Key Concepts

• Fossil Record: Provides evidence of the history of life, including major transitions and extinctions.

• Early Earth Conditions: Life originated under specific conditions; early atmosphere, energy sources, and the formation of organic molecules.

• Major Events in the History of Life:

  • Origin of prokaryotes and eukaryotes

  • Endosymbiotic theory (origin of mitochondria and chloroplasts)

  • Colonization of land by plants, fungi, and animals

  • Mass extinctions (e.g., Permian, Cretaceous)

  • Adaptive radiations following mass extinctions

• Plate Tectonics and Continental Drift: Movement of Earth's plates has influenced the distribution and evolution of organisms.

Example: The Cambrian explosion marks a period of rapid diversification of animal life approximately 540 million years ago.

Summary Table: Types of Reproductive Isolation

Type	Prezygotic or Postzygotic	Description	Example
Habitat Isolation	Prezygotic	Species live in different habitats and do not meet	Garter snakes in water vs. land
Temporal Isolation	Prezygotic	Species breed at different times	Western vs. Eastern spotted skunks
Behavioral Isolation	Prezygotic	Differences in mating behaviors prevent mating	Bird courtship songs
Mechanical Isolation	Prezygotic	Mating is attempted, but morphological differences prevent success	Insect genitalia
Gametic Isolation	Prezygotic	Sperm of one species cannot fertilize eggs of another	Sea urchins
Reduced Hybrid Viability	Postzygotic	Hybrids fail to develop or are frail	Some salamander hybrids
Reduced Hybrid Fertility	Postzygotic	Hybrids are sterile	Mule (horse × donkey)
Hybrid Breakdown	Postzygotic	First-generation hybrids are viable and fertile, but offspring are feeble or sterile	Rice hybrids