Gas exchange in humans and animals

• How does the volume of an organism affect resource consumption?

  Bigger organisms need more resources
• What is the relationship between cell size and chemical reactions?

  Size affects the rate of chemical reactions
• What limits cell size in organisms?

  Surface area to volume ratio
• How do single-celled organisms meet their oxygen needs?

  By absorbing oxygen across the membrane
• What happens to carbon dioxide in single-celled organisms?

  It is removed rapidly to prevent acidity
• Why can cells with a larger surface area to volume ratio move materials more effectively?

  They can move materials in/out more easily
• What type of organisms are flatworms?

  Aquatic organisms
• Why do flatworms have short diffusion pathways?

  No part of their body is far from the surface
• What is the shape of earthworms?

  Cylindrical
• How is the skin of earthworms adapted for respiration?

  It is kept moist by mucus
• What are the requirements for respiratory surfaces?

  • Must be thin for short diffusion pathways
  • Large surface area relative to volume
  • Permeable for easy diffusion
  • Mechanism for steep diffusion gradient
• What type of organisms are Amoeba?

  Single-celled organisms
• Why do single-celled organisms have rapid diffusion?

  They have a large surface area to volume ratio
• How do multicellular organisms differ from unicellular organisms?

  They have many cells aggregated together
• What is the surface area to volume ratio in larger organisms?

  It is lower compared to smaller organisms
• What is the respiratory surface in amphibians?

  Skin and lungs
• How do birds ventilate their lungs?

  Using ribs and flight muscles
• What must fish do for ventilation?

  Keep swimming
• Why do earthworms have low oxygen requirements?

  They are slow-moving with little metabolic needs
• How do gas exchange processes differ among vertebrate groups?

  • Amphibians: Skin and lungs for gas exchange
  • Reptiles: More complex lungs than amphibians
  • Birds: Efficient ventilation without a diaphragm
• What are the features of fish gills?

  • Stacked to increase surface area
  • Thin walls for short diffusion pathways
  • Maintained large surface area by water density
  • One-way current for water flow
  • Many folds to increase surface area
• What are the two groups of fish based on their skeletons?

  Cartilaginous and bony fish
• What is the respiratory surface in fish called?

  Gills
• Why do fish need a good oxygen supply?

  Because they are active organisms
• What are the key features of fish gills?

  • One-way current of water
  • Many folds for large surface area
  • Maintained surface area by water density
• What type of skeleton do cartilaginous fish have?

  Cartilage skeleton
• How many gill pouches do cartilaginous fish have on each side?

  Five gill pouches
• What is the mechanism for water ventilation in cartilaginous fish?

  They must keep swimming for ventilation
• What is parallel flow in cartilaginous fish?

  Blood and water flow in the same direction
• What limits oxygen uptake in cartilaginous fish?

  Equal concentrations of oxygen in blood and water
• How does gas exchange occur in parallel flow?

  Until oxygen concentrations equalize
• What type of skeleton do bony fish have?

  Bone skeleton
• What covers the gills of bony fish?

  The operculum
• How do bony fish maintain a continuous water flow over their gills?

  By creating pressure differences
• What are the steps of the ventilation mechanism in bony fish?

  1. Mouth opens, operculum closes
  2. Floor of mouth lowers, volume increases
  3. Pressure increases, water flows in
  4. Mouth closes, operculum opens
  5. Floor of mouth raises, volume decreases
  6. Pressure increases, water flows out
• How many pairs of gills do bony fish have?

  Four pairs of gills
• What supports each gill in bony fish?

  Gill arch or gill bar
• What are gill filaments responsible for?

  Gas exchange surfaces
• Why do gills collapse out of water?

  They stick together without water
• What is counter-current flow in bony fish?

  • Blood flows opposite to water
  • Maintains a steep concentration gradient
  • More efficient oxygen uptake