Gas Exchange in Animals and Plants

• Ways of Gas Exchange

  • Diffusion
  • Mucus
  • Tracheae
  • Gills
  • Lungs
• The respiratory surface of an unicellular organism is through plasma membrane.
• Gas exchange in frogs and toads is through:

  Cutaneous respiration (via skin)

  pulmonary respiration (via lungs)

  buccopharyngeal respiration (small amount, via mouth and lining of pharynx)
• Amphibians use both negative & positive pressure to ventilate
• Negative Pressure: With Mouth closed but nostrils opened, the floor of the mouth is lowered. The lower air pressure will cause air to rush into their mouth cavity.
• Positive Pressure: With mouth & nostrils shut, floor of mouth rises & pushes air into the lungs.
• Nose –have 2 openings (nostrils), nostrils open into the nasal passages (cavities that extend from the nostrils to the throat), cleans, moistens, and warms the air, has coarse hairs projecting from the inner walls of the nostrils that filters air, has a mucous membrane that lines the walls of the nasal passages
• Pharynx –AKA the throat, found at the back of the mouth, passageway for food and air, the epiglottis presses and covers the opening of air when food is swallowed
• Larynx –AKA the voice box or the A’s apple, located at the upper end of the trachea, primarily involved in sound production, sounds are produced when air is forced past two vocal cords that stretch across the larynx
• Trachea –also called the windpipe, located in front of the esophagus, about 10 cm long and 2.5 cm wide, lined with mucous membranes and cilia, the cilia move mucous and materials toward the throat
• Bronchi –the trachea divides into two hollow branches called the bronchi, each bronchus is attached to the lungs, also lined with cilia and mucus that help filter air, the bronchi branch into smaller and smaller tubes (bronchial tubes)
• Lungs –large spongy, and elastic sac-like structures suspended from each side of the heart, the bronchial tubes further divide into smaller tubes called bronchioles inside the lungs, each bronchiole opens into thin-walled bulb-shaped structures called air sacs or alveoli cells (each is surrounded by a network of capillaries for gas exchange)
• The hemoglobin in RBCs transports 95% of the oxygen in the blood
• When CO2 moves out of the cell, 8% is dissolved in the blood plasma, 25% binds to hemoglobin, and the rest is converted to bicarbonate ions
• The reverse reaction takes place in the lungs when CO2 is released into the atmosphere
• Animals that carry out gas exchange via diffusion

  • Flatworms
  • Planarians
  • Cnidarians (Hydra)
  • Jellyfish
• Diffusion


  The movement of molecules from an area of high concentration to an area of low concentration
• Factors affecting diffusion through a semipermeable membrane


  • Concentration gradient
  • Permeability of the membrane
• Papulae


  Tiny finger-like projections found on the skin of echinoderms
• Functions of papulae in echinoderms

  • Gas exchange
  • Nutrient uptake
  • Waste removal
  • Sensory perception
• Mechanisms in fish gills that maximize gas exchange

  • Large surface area
  • Countercurrent flow
• Countercurrent flow


  Blood flowing through the gill lamellae travels in the opposite direction to the water flowing over them
• 1. chambered heart in frogs


  Allows efficient circulation of oxygenated blood to both lungs and skin, supporting their metabolic needs in various environments
• Guard cells


  • Specialized cells that control the opening and closing of stomata
  • Occur in pairs flanking each side of a stoma
• Turgor pressure in guard cells during the day

  1. Light increases solute concentration

  2. Potassium ion uptake increases solute concentration

  3. Higher turgor pressure opens stomata
• Lenticels


  Raised bumps or corky outgrowths on the stems of woody plants that provide a pathway for gas exchange
• Pneumatophores


  Specialized structures found in some wetland plants that grow upwards from the plant's underground structures and protrude above the water or mud to facilitate gas exchange
• Animals that carry out gas exchange via diffusion

  • Flatworms
  • Planarians
  • Cnidarians (Hydra)
  • Jellyfish
• Animals that can carry out gas exchange via diffusion

  • Have thin, flat bodies or live in water
  • Can absorb oxygen and release carbon dioxide directly through their body surface
• Diffusion


  The movement of molecules from an area of high concentration to an area of low concentration
• Factors affecting diffusion through a semipermeable membrane


  • Concentration gradient
  • Permeability of the membrane
• Papulae


  Tiny finger-like projections found on the skin of echinoderms, such as starfish and sea urchins
• Functions of papulae in echinoderms

  • Gas exchange
  • Nutrient uptake
  • Waste removal
  • Sensory perception
• Mechanisms in fish gills that maximize gas exchange

  • Large surface area
  • Countercurrent flow
• Countercurrent flow


  Blood flowing through the gill lamellae travels in the opposite direction to the water flowing over them
• Why a 3-chambered heart is efficient for frogs

  • Allows efficient circulation of oxygenated blood to both lungs and skin
  • Partial separation of blood streams to prevent fully mixing of oxygenated and deoxygenated blood
• Guard cells


  Specialized cells found in the epidermis of leaves, stems, and other plant organs that control the opening and closing of stomata
• Turgor pressure in guard cells during the day

  Light stimulates photosynthesis and potassium ion uptake, increasing solute concentration and drawing in water, leading to guard cell expansion and stoma opening
• Lenticels


  Raised bumps or corky outgrowths on the stems of woody plants that provide a pathway for gas exchange between internal tissues and the surrounding air
• Pneumatophores


  Specialized structures found in some wetland plants that grow upwards from the plant's underground structures and protrude above the water or mud, allowing gas exchange with the atmosphere