Course review
Review each learning objective in this topic, then open its concept explanation or question set.
Learning objective
• Gas exchange supplies respiratory gases between organisms and environment • Animals take in oxygen and release carbon dioxide for aerobic respiration • Larger or active organisms need specialized exchange surfaces because SA:V decreases
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Learning objective
• Efficient gas-exchange surfaces are permeable, thin, moist, and large • Large surface area and steep concentration gradients increase diffusion • Short diffusion paths speed movement of oxygen and carbon dioxide
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Learning objective
• Dense capillary networks provide large exchange area and rapid transport • Continuous blood flow carries oxygen away and carbon dioxide toward the surface • Ventilation refreshes air or water to maintain steep gas gradients
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Learning objective
• Many small alveoli provide large surface area and thin squamous walls • Capillary beds maintain gradients and bring red blood cells close to alveolar air • Surfactant reduces surface tension, while elastic fibres support ventilation and recoil
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Learning objective
• Diaphragm and intercostal muscles change thoracic volume and pressure • Inspiration uses diaphragm and external intercostal contraction to draw air in • Expiration reduces thoracic volume; internal intercostals and abdominal muscles aid forced exhalation
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Learning objective
• Spirometry records breathing patterns, ventilation rate, and lung volumes • Tidal volume is air moved during normal relaxed breathing • Vital capacity equals tidal volume plus inspiratory and expiratory reserve volumes
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Learning objective
• Stomata allow carbon dioxide, oxygen, and water vapour to diffuse • Guard cells open and close stomata by changes in turgor • Waxy cuticle, lower epidermal stomata, air spaces, mesophyll, and veins balance gas exchange with water loss
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Learning objective
• Dicot leaves have waxy cuticle, upper and lower epidermis, palisade and spongy mesophyll • Vascular bundles contain xylem and phloem for water and assimilate transport • Spongy mesophyll air spaces and stomata create internal diffusion routes
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Learning objective
• Transpiration is evaporation from mesophyll walls followed by diffusion of water vapour through stomata • Temperature, humidity, wind, and light alter concentration gradients and stomatal opening • Potometers estimate transpiration indirectly by measuring water uptake
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Learning objective
• Stomatal density is the number of stomata per unit leaf area • Higher density can increase carbon dioxide uptake and water loss • Leaf casts or micrographs allow stomatal counts and comparisons between species
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Learning objective
• Haemoglobin has four subunits with haem groups that bind oxygen reversibly • Cooperative binding increases oxygen loading in high pO2 and unloading in low pO2 • Foetal haemoglobin has higher oxygen affinity than adult haemoglobin for placental transfer
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Learning objective
• Increased carbon dioxide lowers pH and reduces haemoglobin affinity for oxygen • The oxygen dissociation curve shifts right at higher carbon dioxide concentration • The Bohr effect promotes oxygen release in actively respiring tissues
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Learning objective
• Oxygen dissociation curves plot haemoglobin saturation against partial pressure of oxygen • A sigmoid curve shows cooperative binding between haemoglobin subunits • Curve position indicates oxygen affinity, loading in lungs, and unloading in tissues
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