Why do large organisms need specialised exchange surfaces?

- low SA:V ratio - larger so greater diffusion distance - high metabolic demand that can't be met by only diffusion

What are the features of efficient exchange surfaces and how do they link to efficiency?

- large surface area so more diffusion can happen at once - thin layers for shorter diffusion distance - good blood supply maintains steep concentration gradient for quick diffusion - ventilation to maintain steep concentration gradient

What are the structures of the human gas exchange system and their functions?

trachea: - carries air to and from the lungs - branched and lined with a ciliated epithelium with goblet cells that secrete mucus to trap dust and pathogens - supported by cartilage rings that stop it from collapsing bronchi: - carry air from the trachea into each lung - also has cartilage rings bronchioles: - carry air deeper into the lungs - walls contain smooth muscle, which can contract to narrow the airway or relax to widen it alveoli: - site of gas exchange

Describe the process of breathing.

Inhalation: - external intercostal muscles contract - ribs move upwards and outwards - diaphragm contracts and flattens - thoracic volume increases - pressure decreases - air enters lungs exhalation: - external intercostal muscles relax - ribs move downwards and inwards - diaphragm relaxes - thoracic volume decreases - pressure increases - air leaves lungs

What are the different aspects of lung volume that can be measured?

tidal volume - volume that moves in and out of the lungs in each resting breath vital capacity - volume of air that can be exhaled when the deepest intake of breath is taken followed by the strongest possible exhalation inspiratory reserve volume - maximum volume of air that can be taken in over a normal inhalation expiratory reserve volume - maximum volume of air that can be exhaled over a normal exhalation residual volume - amount of air left in the lungs after the strongest possible exhalation total lung capacity: vital capacity + residual volume

What are the adaptations of gills for gas exchange?

- gill filaments and gill lamellae provide a large surface area for efficient gas exchange - the typical ones - water constantly passes over the gills

Explain countercurrent flow and why its important?

- water flows over gills in one direction while blood flows through lamellae in the opposite direction important because: - water always contains more oxygen than the blood, maintaining the concentration gradient and causing oxygen to always move into the blood

Describe the structures of the insect gas exchange system and their function.

spiracles: - small opening on body surface, have valves that can open and close - allows air into the tracheal system - reduces water loss by evaporation tracheae: - larger tubes than spiracles - reinforced with chitin tracheoles: - fine branches that reach individual cells

Explain the adaptations of insect gas exchange system.

- many tracheoles provide a large surface area for diffusion - tracheoles extend directly to cells to minimize diffusion distance - cells using oxygen maintain concentration gradient