Biology: How Life Works Unit 3 Summary

Unit 3 Learning Outcomes

  • Reproduction in asexual organisms promotes genetic diversity.
  • Features of life cycles vary among different lineages of organisms.
  • Eukaryotic reproductive strategies relate to their environments.
  • Cell structure differences impact growth and development in multicellular eukaryotes.
  • Nutrient acquisition adaptations differ among multicellular eukaryotes.
  • Gas and nutrient transport relates to short-distance and bulk flow processes.
  • Balancing gas and waste exchange with osmoregulation is a challenge.
  • Organisms use various mechanisms for self-defense.
  • Immunological memory allows specific pathogen defense in some organisms.

Transport Mechanisms

  • Short Distance Transport:
    • Diffusion, facilitated diffusion, active transport.
  • Bulk Flow:
    • Long-distance transport driven by pressure differences.

Gas Exchange

  • Aquatic organisms adapt respiratory systems to low dissolved oxygen.
  • Gills:
    • Structured for maximal oxygen extraction (countercurrent exchange).
  • Tracheal Systems (insects):
    • Deliver oxygen directly to tissues.
  • Lungs (mammals):
    • Facilitate gas exchange with blood.

Circulatory Systems

  • Open vs. Closed Circulatory Systems:
    • Open: lower pressure, fluids mix.
    • Closed: higher pressure, separate fluids, better suited for larger systems.

Osmoregulation

  • Osmosis: Movement of water across selectively permeable membranes.
  • Marine Fish: Lose water via osmosis; compensated by drinking seawater.
  • Freshwater Fish: Gain water via osmosis; compensated by active ion absorption.

Waste Excretion

  • Excretory organs manage toxic waste and osmoregulation.
  • Nitrogenous waste varies: Ammonia > Urea > Uric Acid (toxicity & energy to eliminate).

Plant Transport

  • Gas exchange via stomata; water transport through xylem.
  • Guard cells regulate CO₂ and water exchange.

Defense Mechanisms

  • Plants use mechanical, chemical, and mutualistic defenses.
  • Secondary metabolites in plants often serve as defense and medicinal compounds.

Immune Responses

  • Barriers: First line of defense (skin, membranes).
  • Innate Immunity: Non-specific responses.
  • Adaptive Immunity: Specific responses with memory cells.

Autoimmune Disorders

  • Occur when the immune system attacks its own cells.
  • Examples: Rheumatoid arthritis, Type 1 diabetes, Multiple sclerosis.

Prion Diseases

  • Prions evade the immune response due to being recognized as self.
  • Cause neurodegenerative diseases, often fatal.