Specialized Exchange Surfaces

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Specialized Exchange Surfaces Leaves: Plants use their leaves to get the gasses they need. They need carbon dioxide for photosynthesis and oxygen for respiration. The gases diffuse into the intercellular spaces of the leaf through the stomata, these are pores normally found on the underside of the leaf. The gases then diffuse into the cells that require them from these spaces. Whether the stomata opens or closes depends on changes in the turgor of the guard cells. When osmosis causes water to flow into the guard cells, their turgor increases and they expand. Due to the relatively inelastic inner wall, the guard cells bend and draw away from each other, so the pore opens. If the guard cells loose water the opposite happens and the pore closes. The guard cells lower their water potential to draw in water from the surrounding epidermal cells, by actively accumulating potassium ions. This requires ATP which, is supplied by the chloroplasts in the guard cell Gills: Fish uses gills as their gas exchange surface. Gills have a large surface area because of the numerous folds within them. The rows of gill filaments have many protrusions called gill lamellae. Water is continuously pumped through the mouth and over the gills. This keeps the folds moist and well supported. Fish also have an efficient transport system within the lamellae which maintains the concentration gradient across the lamellae. The counter current flow is the water flowing past the gills in the opposite direction to the blood. The arrangement of the water means that they can extract oxygen at three times the rate humans can. An insect’s tracheole system: Insects have a more specialised gas exchange system. Gases need to be transported directly to the respiring tissues. Insects have tiny holes along the side of their body called spiracles. They are openings of small tubes running into the
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