Themes of Biology and Evolution: Study Guide

Chapter 1: Themes of Biology and Evolution

Five Themes of Biology

• Organization: Biological systems are structured hierarchically, from molecules to the biosphere. Emergent properties arise at each level due to interactions among components.

• Information: Life processes depend on the transmission and expression of genetic information, primarily through DNA.

• Energy and Matter: Organisms require energy to perform work; energy flows through ecosystems while chemicals cycle. Producers (e.g., plants) convert energy, consumers (e.g., animals) use it.

• Interactions: Organisms interact with each other and their environment, leading to feedback regulation (e.g., negative feedback maintains homeostasis).

• Evolution: The core theme explaining the unity and diversity of life; all organisms share a common ancestry but have adapted to different environments.

Cell Types

• Eukaryotic cells: Have membrane-bound organelles, including a nucleus.

• Prokaryotic cells: Lack a nucleus and membrane-bound organelles.

Genetic Information

• DNA: The molecule that stores genetic information and transmits it from one generation to the next.

Energy Flow and Chemical Cycling

• Energy enters ecosystems as sunlight and leaves as heat.

• Chemicals (e.g., carbon, nitrogen) cycle within ecosystems.

Feedback Regulation

• Negative feedback: A process in which a system responds to a change by returning to its original state.

Climate Change

• Caused by increased greenhouse gases, which affect global temperatures and ecosystems.

Unity and Diversity of Life

• Life is unified by common molecular and cellular features, but diverse due to evolutionary adaptation.

Three Domains of Life

Domain	Characteristics
Bacteria	Prokaryotic, diverse, found in many environments
Archaea	Prokaryotic, often found in extreme environments
Eukarya	Eukaryotic, includes plants, animals, fungi, protists

Charles Darwin and Natural Selection

• Darwin proposed that evolution occurs via natural selection, where organisms better adapted to their environment survive and reproduce.

Scientific Inquiry

• Inductive reasoning: Generalizing from specific observations.

• Deductive reasoning: Predicting specific results from general principles.

• Hypothesis: A testable explanation for an observation.

• Theory: A broad explanation supported by evidence.

• Independent variable: The factor manipulated in an experiment.

• Dependent variable: The factor measured in an experiment.

Chapter 22: Natural Selection

Charles Darwin and Evolution

• Darwin's theory explains the unity and diversity of life through descent with modification.

• Evolution: Change in the genetic composition of a population over time.

Paleontology and Early Influences

• Cuvier: Developed paleontology noted extinction events.

• James Hutton: Proposed gradual geological changes.

• Charles Lyell: Expanded on Hutton's ideas, emphasizing uniform processes.

Adaptations and Descent with Modification

• Adaptations: Traits that enhance survival and reproduction.

• Artificial selection: Humans select traits in domesticated species.

Darwin’s Observations and Inferences

• Observation 1: Members of a population vary in their traits.

• Observation 2: Traits are inherited from parents to offspring.

• Inference 1: Individuals with advantageous traits survive and reproduce.

• Inference 2: Favorable traits accumulate in the population.

Allele Frequency and Population Evolution

• Populations evolve as allele frequencies change over time.

Evidence for Evolution

Type of Evidence	Example
Direct Observations	MRSA antibiotic resistance
Homology	Mammal forearm bones
Vestigial Structures	Remnants of ancestral features
Convergent Evolution	Analogous traits (e.g., wings in birds and bats)
Biogeography	Distribution of species across continents

• Analogous traits: Similar function, different ancestry.

• Homologous traits: Similar ancestry, may have different function.

Chapter 23: Evolution of Populations

Mechanisms of Evolution

• Four mechanisms: Natural selection, Genetic drift, Gene flow, Mutation.

Microevolution vs. Macroevolution

• Microevolution: Changes in allele frequencies within a population.

• Macroevolution: Broad patterns of evolutionary change above the species level.

Genetic Variation

• Arises from mutations and sexual reproduction.

• Mutation: Source of new alleles; types include point mutations, insertions, deletions.

Hardy-Weinberg Equation

• Measures allele and genotype frequencies in a population under equilibrium.

$p^2 + 2pq + q^2 = 1$

$p + q = 1$

Genetic Drift

• Founder Effect: Small group establishes a new population; allele frequencies may differ.

• Bottleneck Effect: Population size drastically reduced; genetic variation decreases.

Gene Flow

• Movement of alleles between populations.

Natural Selection and Adaptive Evolution

• Relative fitness: Contribution to the gene pool of the next generation.

• Directional selection: Favors one extreme phenotype.

• Stabilizing selection: Favors intermediate phenotypes.

• Disruptive selection: Favors both extreme phenotypes.

• Sexual selection: Traits that increase mating success.

Chapter 24: Origin of Species

Speciation and Biological Species Concept

• Speciation: Formation of new species.

• Biological species concept: Species are groups of interbreeding populations reproductively isolated from others.

Reproductive Isolation

• Prezygotic Barriers: Prevent mating or fertilization.

• Types:

  • Habitat isolation: Species occupy different habitats.

  • Temporal isolation: Species breed at different times.

  • Behavioral isolation: Different mating behaviors.

  • Mechanical isolation: Incompatible reproductive structures.

  • Gametic isolation: Gametes cannot fuse.

• Postzygotic Barriers: Prevent hybrid offspring from developing or reproducing.

• Types:

  • Reduced hybrid viability: Hybrids do not develop properly.

  • Reduced hybrid fertility: Hybrids are sterile.

  • Hybrid breakdown: Hybrids' offspring are weak or sterile.

Limitations of Biological Species Concept

• Cannot be applied to asexual organisms or fossils.

Allopatric vs. Sympatric Speciation

• Allopatric speciation: Occurs when populations are geographically separated.

• Sympatric speciation: Occurs without geographic separation (e.g., Cichlids).

Hybrid Zones and Their Outcomes

• Hybrid zones: Regions where different species meet and mate.

• Three outcomes over time:

  • Reinforcement: Strengthening of reproductive barriers.

  • Fusion: Weakening of barriers, species merge.

  • Stability: Continued production of hybrids.

Punctuated Equilibria

• Evolutionary change occurs in rapid bursts, separated by periods of stability.

Chapter 25: History of Life on Earth

Macroevolution and Early Earth

• Macroevolution: Major evolutionary changes, such as the origin of new groups.

• Early Earth conditions favored the formation of life.

Fossils and the Fossil Record

• Types of fossils: body fossils, trace fossils.

• Fossil record shows patterns of evolution, but is incomplete due to preservation biases.

• Fossils are dated using radiometric dating and relative dating.

Eons and Eras

• Major divisions: Hadean, Archaean, Proterozoic, Phanerozoic eons.

Key Events in the History of Life

• First single-celled organisms: Stromatolites.

• Photosynthesis and the oxygen revolution.

• First eukaryotes: Endosymbiosis theory.

• Origin of multicellularity.

• Cambrian explosion: Rapid diversification of animals.

• Colonization of land: Arthropods, tetrapods, plants.

Plate Tectonics and Pangaea

• Movement of continents affects evolution and distribution of species.

Mass Extinctions and Adaptive Radiation

Mass Extinction	Characteristics
Permian	Largest extinction, affected marine life
Cretaceous	Extinction of dinosaurs, rise of mammals
Sixth (current)	Human-driven, ongoing

• Adaptive radiation: Rapid evolution of new species from a common ancestor, often after mass extinctions.