Topic 3 Summary

• What is the relationship between size and surface area to volume ratio (SA:V) in organisms?

  As size increases, SA:V tends to decrease
• How can the surface area to volume ratio be increased in organisms?

  By having thin, flat, folded, or elongated structures
• How is the surface area to volume ratio calculated?

  Divide surface area by volume
• What is the surface area to volume ratio of a cube with 2 cm sides?

  3:1
• What is the surface area to volume ratio of a cube with 4 cm sides?

  1.5:1
• Why is calculating surface area to mass more advantageous than surface area to volume?

  It is easier and more accurate for irregular shapes
• What is metabolic rate?

  Energy used by an organism over time
• How is metabolic rate often measured?

  By oxygen uptake during aerobic respiration
• How does surface area to volume ratio affect metabolic rate?

  Higher SA:V increases metabolic rate in smaller organisms
• Why do smaller organisms have a higher metabolic rate?

  They lose heat faster per unit mass
• What adaptations facilitate gas exchange in larger organisms with reduced SA:V?

  1. Changes to body shape (e.g., long/thin)
  2. Development of specialized surfaces/organs (e.g., lungs)
  3. Maintenance of concentration gradients (e.g., ventilation)
• What is the structure of a single-celled organism's body surface for gas exchange?

  Thin, flat shape with large SA:V
• How does the tracheal system of an insect facilitate gas exchange?

  It has spiracles, tracheae, and tracheoles
• What is the function of spiracles in an insect's tracheal system?

  They allow diffusion by opening and closing
• How are tracheoles adapted for gas exchange in insects?

  They have thin walls for short diffusion distance
• How does abdominal pumping aid gas exchange in insects?

  It changes pressure to move air in/out
• How does fluid in tracheoles affect gas exchange during exercise?

  Fluid is drawn into tissues, increasing air in tracheoles
• What structural and functional compromises do terrestrial insects make for gas exchange?

  • Thick waxy cuticle reduces water loss
  • Spiracles can open for gas exchange and close to limit water loss
  • Hairs trap moist air, reducing water potential gradient
• How are fish gills adapted for gas exchange?

  Gills have filaments and lamellae for increased surface area
• What is the role of countercurrent flow in fish gills?

  It maintains a concentration gradient for oxygen diffusion
• What happens if parallel flow occurs in fish gills?

  Equilibrium is reached, limiting oxygen diffusion
• What adaptations do dicotyledonous plants have for gas exchange?

  • High density of stomata for gas exchange
  • Spongy mesophyll with air spaces for diffusion
  • Thin structure for short diffusion distance
• What adaptations do xerophytic plants have for gas exchange while limiting water loss?

  • Thicker waxy cuticle to reduce evaporation
  • Sunken stomata to trap water vapor
  • Spines/needles to reduce surface area
• What are the main components of the human gas exchange system?

  Trachea, bronchi, bronchioles, lungs, alveoli
• What features of the alveolar epithelium aid gas exchange?

  Flattened, one cell thick, folded, moist, and permeable
• How does gas exchange occur in the lungs?

  Oxygen diffuses from alveoli to blood
• Why is ventilation important for gas exchange?

  It maintains concentration gradients of gases
• What are the steps of human ventilation during inspiration?

  1. Diaphragm contracts and flattens
  2. External intercostal muscles contract
  3. Ribcage moves up and out
  4. Volume increases, pressure decreases, air moves in
• What are the steps of human ventilation during expiration?

  1. Diaphragm relaxes and moves upwards
  2. External intercostal muscles relax
  3. Ribcage moves down and in
  4. Volume decreases, pressure increases, air moves out
• Why is expiration normally passive at rest?

  Due to elastic recoil in alveoli
• How do lung diseases affect gas exchange?

  They increase diffusion distance or reduce surface area
• How do lung diseases affect ventilation?

  They reduce lung elasticity and airflow
• Why do people with lung disease experience fatigue?

  Cells receive less oxygen for respiration
• How can data be analyzed to assess the effects of pollution on lung disease?

  • Describe overall trends (correlation)
  • Calculate percentage change
  • Interpret standard deviations
  • Use statistical tests (e.g., correlation coefficient)
• What factors should be evaluated when analyzing experimental data on lung disease risk factors?

  • Sample size and diversity
  • Control groups and variables
  • Duration of study
  • Context of data generalization
• What is the difference between correlation and causation?

  Correlation is a relationship; causation is a cause
• Why is it important to identify features of gas exchange surfaces?

  To understand their efficiency in gas exchange
• What are large biological molecules hydrolysed into during digestion?

  Smaller soluble molecules
• Why must smaller molecules be absorbed across cell membranes?

  To enter the blood for transport
• What enzyme hydrolyses starch to maltose in mammals?

  Amylase