Evidence and Mechanisms of Evolution

Evidence for Evolution

• Fossil Evidence: Shows transitions between species over time. Archaeopteryx is an example, linking dinosaurs to birds.
• Anatomy: Homologous structures share ancestry (e.g., mammalian limbs); analogous structures result from convergent evolution.
• Embryology: Similar early development in different species suggests common ancestry.
• Biogeography: Geographic distributions reflect evolutionary history, like Darwin's finches.
• Molecular Biology: DNA and protein similarities show evolutionary relationships. Humans and chimpanzees, for instance, share significant genomic similarities.

Mechanisms of Evolution

• Natural Selection: Traits boosting survival/reproduction increase frequency. Peppered moths are an example.
• Mutation: Random DNA changes introduce new traits, like antibiotic resistance in bacteria.
• Genetic Drift: Random changes in allele frequencies, especially in small populations. The bottleneck effect is a drastic reduction in population size (cheetahs). The founder effect establishes a new population with a small subset of individuals (island birds).
• Gene Flow: Movement of alleles between populations (e.g., migration).

Types of Selection

• Natural Selection: Traits enhancing fitness triumph (camouflage in prey).
• Artificial Selection: Human-driven selection (dog breeding).
• Sexual Selection: Traits improving mating success (peacock feathers).

Species Concepts

• Biological Species Concept: Groups of interbreeding populations that produce fertile offspring. Limitations include inability to classify asexual species or fossils.
• Morphological Species Concept: Classifies species based on physical traits.

Speciation

• Allopatric Speciation: Geographic barriers separate populations (e.g., river divides squirrel populations).
• Sympatric Speciation: Reproductive barriers within the same area (e.g., polyploidy in plants).

Reproductive Barriers

• Prezygotic Barriers: Prevent fertilization (e.g., temporal isolation in frogs).
• Postzygotic Barriers: Hybrid offspring are inviable or infertile (e.g., mules).

Modes of Selection

• Directional Selection: Favors one extreme (e.g., antibiotic resistance).
• Stabilizing Selection: Favors intermediate traits (e.g., human birth weight).
• Disruptive Selection: Favors extremes (e.g., varied terrain leading to different colored mice).

Body's Systems (Chapter 16)

• Four Tissue Types:
  • Epithelial: Covers surfaces, like skin.
  • Connective: Supports and connects, like bone and blood.
  • Muscle: Facilitates movement (e.g., skeletal muscle).
  • Nervous: Processes and transmits information (e.g., neurons).
• Homeostasis: Maintaining internal balance (e.g., body temperature and blood sugar).
• Negative Feedback Loops: Reverse deviations from set points (e.g., sweating when overheated).
• Action Potential: Electrical signal in neurons, transmitting information along axons.

Immune System (Chapter 17)

• Innate vs. Adaptive Immunity:
  • Innate: Immediate, non-specific (e.g., skin, phagocytes).
  • Adaptive: Slower, specific, with memory (e.g., antibodies).
• Immune Cells:
  • Phagocytic cells: Engulf pathogens (e.g., macrophages).
  • T cells: Attack infected cells or aid other responses.
  • B cells: Produce antibodies.
  • Dendritic cells: Present antigens to T cells.
• Antigens and Antibodies: Antigens trigger immune responses; antibodies are proteins neutralizing antigens.

Population and Community Ecology (Chapter 19)

• Population Size vs. Density: Size is total individuals; Density is individuals per area.
• Species Distribution Patterns:
  • Random: No pattern (e.g., dandelions).
  • Clumped: Grouped in patches (e.g., herds).
  • Uniform: Evenly spaced (e.g., penguins).
• Population Growth:
  • Exponential: Rapid growth, no limits (J-curve).
  • Logistic: Growth with carrying capacity limits (S-curve).
• Density-Dependent vs. Density-Independent Factors:
  • Density-dependent: Impact depends on population size (e.g., disease).
  • Density-independent: Affects population regardless of size (e.g., natural disasters).
• Interspecific Interactions:
  • Competition: Resources competed for (lions and hyenas).
  • Predation: Predator-prey interactions (hawk and mouse).
  • Herbivory: Herbivores consuming plants (deer eating leaves).
  • Commensalism: One benefits; other unaffected (barnacles on whales).
  • Mutualism: Both benefit (bees and flowers).
  • Parasitism: One benefits; other harmed (ticks on dogs).
• Defenses Against Predation and Herbivory: Plants (thorns, toxins); Animals (camouflage, mimicry, physical defenses like porcupine quills).