Adaptations for Transport

Adaptations for Transport in Plants

  • Xylem vessels: Specialised for the conduction of water and dissolved mineral salts from roots to leaves; dead tissues with a hollow lumen and no end walls to prevent obstruction of flow.
  • Sieve tubes in phloem: Responsible for sugar transport; sieve plates allow flow between cells; companion cells assist in loading and unloading sugars.
  • Root hair cells: Increases surface area for water uptake; selectively permeable membrane allow for water and mineral ion absorption.
  • Stomata: Opening and closing regulate gas exchange and water loss; always more open at light due to guard cells, facilitating photosynthesis.

Adaptations for Transport in Animals

  • Red Blood Cells: Biconcave shape maximises surface area for gas exchange; Hemoglobin binds oxygen for transport; no nucleus to release more space for oxygen.
  • White Blood Cells: Different types (e.g., lymphocytes and phagocytes) have different functions related to the immune response, including producing antibodies and engulfing pathogens.
  • Platelets: Small cell fragments that initiate clotting upon injury, preventing excess blood loss.
  • Blood vessels: Arteries have thick, muscular walls that can withstand high blood pressure; veins have valves to prevent backflow; capilaries have thin walls allowing for exchange of material with tissues.
  • Heart: A four-chambered heart (two atria and two ventricles) allows separation of oxygenated and deoxygenated blood, enabling a higher metabolic rate in mammals and birds.
  • Lymphatic System: Help in the recirculation of fluid and the transport of fats; also play a major role in the immune response.

Transport Across Membranes

  • Diffusion: Passive movement of particles from high to low concentration; important for gas exchange.
  • Osmosis: Passive movement of water molecules from a region of low solute concentration to a region of high solute concentration; essential for maintaining cell turgidity.
  • Facilitated Diffusion: Passive transport facilitated by transporter proteins for molecules unable to cross the membrane due to size or charge.
  • Active Transport: Allows the movement of substances against a concentration gradient with the use of ATP; used in sodium-potassium pump, uptake of glucose in intestines and kidneys.

Gaseous Exchange in Organisms

  • Insects: Tracheae lead air to tissues for gas exchange; Spiracles control water loss.
  • Fish: Gills have a large surface area and blood flow counter the water flow, optimizing oxygen intake.
  • Mammals: Alveoli provides a large surface area for gas exchange; Ventilation (breathing) maintains concentration gradient for oxygen intake and carbon dioxide removal.
  • Plants: Leaves contain small openings known as stomata for gaseous exchange; the intercellular spaces in the mesophyll tissue facilitate diffusion of gases.