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 process by which populations change over time, explaining both the unity and diversity of life.

Cell Types

• Eukaryotic cells: Contain 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, affecting global temperatures and ecosystems.

Unity and Diversity of Life

• Life is unified by common features (e.g., DNA) and diversified by evolution.

Three Domains of Life

• Bacteria

• Archaea

• Eukarya

Scientific Inquiry

• Inductive reasoning: Generalizations based on observations.

• Deductive reasoning: Predictions based on general principles.

• Hypothesis: A testable explanation for an observation.

• Theory: A broad explanation supported by evidence.

• Variables: Independent variable is manipulated; dependent variable is measured.

Chapter 22: Natural Selection

Charles Darwin and Natural Selection

• Natural selection: The process by which organisms with favorable traits are more likely to survive and reproduce.

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

Unity and Diversity of Life

• All life shares common ancestry, but adaptation leads to diversity.

Historical Figures

• Paleontology: Study of fossils; Cuvier contributed to understanding extinction.

• James Hutton and Charles Lyell: Proposed gradual geological changes.

Adaptations and Descent with Modification

• Adaptations: Traits that enhance survival and reproduction.

• Descent with modification: Species change over time, giving rise to new species.

Artificial Selection

• Humans select traits in domesticated species (e.g., dog breeds).

Darwin’s Observations and Inferences

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

• Observation 2: Traits are inherited.

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

• Inference 2: Favorable traits accumulate over generations.

Allele Frequency and Population Evolution

• Populations evolve as allele frequencies change.

Evidence for Evolution

• Direct observations: e.g., MRSA antibiotic resistance.

• Homology: Similar structures due to common ancestry (e.g., mammal forearm bones).

• Vestigial structures: Remnants of features that served a function in ancestors.

• Convergent evolution: Independent evolution of similar traits (e.g., wings in bats and birds).

• Analogous traits: Similar function, different ancestry; homologous traits: Similar ancestry, possibly different function.

• Biogeography: Geographic distribution of species.

Chapter 23: Evolution of Populations

Mechanisms of Evolution

• 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: Change in DNA sequence; creates new alleles.

• Types: Point mutations, chromosomal mutations.

Sexual Reproduction

• Shuffles alleles, increasing genetic diversity.

Hardy-Weinberg Equation

• Measures allele and genotype frequencies in a population not evolving.

Hardy-Weinberg Equation:

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

$p + q = 1$

Genetic Drift

• Founder Effect: Small group establishes new population; allele frequencies differ from original.

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

Gene Flow

• Movement of alleles between populations.

Natural Selection and Adaptive Evolution

• Relative fitness: Contribution to gene pool relative to others.

• Directional selection: Favors one extreme phenotype.

• Stabilizing selection: Favors intermediate phenotypes.

• Disruptive selection: Favors both extremes.

• Adaptations: Traits shaped by selection.

• Sexual selection: Traits that increase mating success.

• Environmental impacts can influence selection.

Chapter 24: Origin of Species

Speciation

• Process by which new species arise.

Biological Species Concept

• Species are groups of interbreeding populations reproductively isolated from others.

Reproductive Isolation

• Prezygotic Barriers:

  • Habitat isolation: Populations live in different habitats.

  • Temporal isolation: Populations breed at different times.

  • Behavioral isolation: Differences in mating behavior.

  • Mechanical isolation: Incompatible reproductive structures.

  • Gametic isolation: Gametes cannot fuse.

• Postzygotic Barriers:

  • Reduced hybrid viability: Hybrids fail to develop or survive.

  • 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 due to geographic isolation.

• Sympatric: Speciation without geographic isolation (e.g., Cichlids).

Hybrid Zones

• Regions where different species meet and mate.

• Three outcomes over time: reinforcement, fusion, stability.

Punctuated Equilibria

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

Chapter 25: History of Life on Earth

Macroevolution

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

Early Conditions Favorable to Life

• Earth's early atmosphere and environment allowed for the formation of simple molecules.

Fossils and the Fossil Record

• Types: body fossils, trace fossils.

• Fossil record shows patterns of evolution and extinction.

• Incomplete due to preservation bias; hard parts fossilize better.

• Dating: relative dating (strata), radiometric dating.

Eons and Eras

• Major divisions of geologic time: Hadean, Archaean, Proterozoic, Phanerozoic.

Key Events in History of Life

• First single-celled organisms: stromatolites.

• Photosynthesis and 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.

Mass Extinctions and Adaptive Radiation

• Permian Mass Extinction

• Cretaceous Mass Extinction

• Sixth Mass Extinction (current)

• Adaptive radiation: rapid evolution of new species after extinction events.