exchange and transport in animals

• Transporting substances


  It is necessary to transport substances into organisms which are vital for life, and to transport waste products out of the organism to prevent them from accumulating
• Plants

  • Need to be highly specialised in taking in carbon dioxide and excreting oxygen (a waste product of photosynthesis) out, while at the same time being able to take in dissolved nutrient and mineral molecules and water from the soil and air
• Animals

  • Have especially advanced systems to remove waste - such as the kidney, which efficiently removes waste such as urea and excess ions. This is vital, as if excess urea is not removed it builds up in the body and becomes toxic. Excess carbon dioxide can also build up and dissolve in the blood, causing it to become acidic - leading to a condition called acidosis
• Exchange surfaces

  Specialised surfaces that allow efficient transport of substances from one area to another (from outside to inside the organism, for example)
• Exchange surfaces


  • Root hair cells of plants
  • Walls of the nephrons in the kidney
  • Alveoli in the lungs
  • Villi in the small intestine
  • Gills of fish
  • Leaves of plants
• Exchange surfaces


  • Often have a short distance for diffusion and a large surface area
• Surface Area to Volume Ratio

  The size of the surface area of the organism compared to its volume
• Single-celled organisms can use diffusion to transport molecules into their body from the air as they have a relatively large surface area to volume ratio</b>

  
• Multicellular organisms cannot rely on diffusion alone as they have a small surface area to volume ratio</b>
• Alveoli


  • Very small and arranged in clusters, creating a large surface area for diffusion to take place over
  • Surrounded by capillaries that provide a large blood supply, maintaining the concentration gradient
  • Walls are very thin, meaning there is a short diffusion pathway
• Factors affecting rate of diffusion

  Surface area, concentration gradient, membrane thickness, temperature

  
• Calculating rate of diffusion

  Use surface area, difference in concentration between the two substances either side of a membrane, and the thickness of a membrane

  
• Components of blood


  • Plasma
  • Red blood cells
  • White blood cells
  • Platelets
• Plasma


  Liquid that carries the components in the blood: red blood cells, white blood cells, platelets, glucose, amino acids, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins
• Red blood cells


  Carry oxygen molecules from the lungs to all the tissues in the body
• Capillaries


  • Provide a large blood supply
  • Maintain the concentration gradient
• Walls of the alveoli

  • Very thin
  • Short diffusion pathway
• Calculating rate of diffusion

  1. Given surface area

  2. Difference in concentration between two substances

  3. Thickness of membrane

  
• Components of blood


  • Plasma
  • Red blood cells
  • White blood cells
  • Platelets
• Plasma


  Liquid that carries the components in the blood
• Red blood cells


  • Carry oxygen molecules from the lungs to all the cells in the body
  • Biconcave disc shape provides a large surface area
  • No nucleus allowing more room to carry oxygen
  • Contain the red pigment haemoglobin, which binds to oxygen and forms oxyhaemoglobin
• White blood cells


  • Part of the immune system
  • Have a nucleus
  • Produce antibodies against microorganisms
  • Engulf and digest pathogens
  • Produce antitoxins to neutralise toxins
• Platelets


  • Help the blood clot form at the site of a wound
  • Small fragments of cells
  • No nucleus
• Types of blood vessels

  • Arteries
  • Veins
  • Capillaries
• Arteries


  • Carry blood AWAY from the heart
  • Layers of muscle in the walls make them strong
  • Elastic fibres allow them to stretch
• Veins


  • Carry blood TOWARDS the heart
  • Wide lumen to allow low pressure blood to flow
  • Have valves to ensure blood flows in the right direction
• Capillaries


  • Allow blood to flow very close to cells
  • One cell thick walls create a short diffusion pathway
  • Permeable walls so substances can move across them
• Parts of the circulatory system

  • Heart
  • Lungs
  • Body
• Double circulatory system


  1. Deoxygenated blood flows into the right atrium and then into the right ventricle which pumps it to the lungs

  2. Oxygenated blood flows into the left atrium and then into the left ventricle which pumps oxygenated blood around the body
• Heart


  • Muscular walls to provide a strong heartbeat
  • Thicker muscular wall of the left ventricle to pump blood around the body
  • 4 chambers that separate the oxygenated blood from the deoxygenated blood
  • Valves to make sure blood does not flow backwards
  • Coronary arteries cover the heart to provide its own oxygenated blood supply
• Blood flow through the heart

  1. Blood flows into the right atrium through the vena cava, and left atrium through the pulmonary vein

  2. The atria contract forcing the blood into the ventricles

  3. The ventricles then contract, pushing the blood in the right ventricle into the pulmonary artery to be taken to the lungs, and blood in the left ventricle to the aorta to be taken around the body

  4. Valves close to make sure the blood does not flow backwards
• Natural resting heart rate

  Around 70 beats per minute
• Pacemaker


  Group of cells found in the right atrium that provide stimulation through small electrical impulses which pass as a wave across the heart muscle, causing it to contract
• Artificial pacemaker


  Electrical device that produces a signal causing the heart to beat at a normal speed
• Respiration


  Process of transferring energy from glucose so living processes can occur
• Respiration


  • Exothermic
  • Can take place aerobically (with oxygen) or anaerobically (without oxygen)
• Anaerobic respiration


  In animals: Glucose (C6H12O6) ---> Lactic acid

  In plant and yeast cells: Glucose (C6H12O6) ---> Ethanol + Carbon dioxide (CO2)
• Anaerobic respiration does not yield as much energy as aerobic respiration
• Anaerobic respiration is only used as a last resort, for example during a sprint where it is difficult to breathe in enough oxygen
• Measuring cardiac output


  Cardiac output = stroke volume × heart rate