Exchange and transport in animals

• Organisms exchanging substances with their environment

  • Cells need oxygen for aerobic respiration which produces carbon dioxide as a waste product. They move between cells and environment by diffusion
  • Water is taken up in cells by osmosis. In animals, food molecules and mineral ions go along with it
  • Urea (a waste product from proteins) diffuses from cells to the blood plasma for removal from the body via the kidneys
• Multicellular organisms need exchange surfaces

  In single celled organisms gases and dissolved substances can diffuse directly into the cell membrane due to their large surface area compared to their volume.

  Multicellular have a smaller surface are compared to their volume which makes it harder to exchange substances to supply their entire volume. So they need an exchange surface and mass transport system so diffusion can happen efficiently and substances can be moved between the exchange surface and the body.
• Gas exchange in mammals

  The job of the lungs is to transfer oxygen to blood and remove waste carbon dioxide from blood. To do this, the lungs contain millions of little air sacs called alveolis where gas exchange takes place. Blood arriving at alveoli has a lot of CO2 and not alot of oxygen which maximises the concentration gradient for diffusion. Oxygen diffuses into the blood from the air. It diffuses the opposite direction for breathing out
• Alveoli adaptations for gas exchange

  Alveoli are specialised to maximise diffusion of oxygen and carbon dioxide:

  • Moist lining for dissolving gases
  • A good blood supply to maintain the concentration gradient
  • Very thin walls minimising distance gases have to move
  • Large surface area
• Red blood adaptations

  • Their job is to carry oxygen from the lungs to all the other cells in the body
  • Biconcave disc to give more surface area for absorbing oxygen
  • No nucleus- more room for oxygen
  • They contain haemoglobin which binds to oxygen in the lungs and splits the oxyhaemoglobin to release oxygen in body tissue cells

  
• White blood cells adaptations

  1. Phagocytes- engulf pathogens with phagocytosis
  2. Lymphocytes- produce antibodies against pathogens and some produce antitoxins to neutralise any toxins produced
  3. While you have an infection your white blood cells multiply to fight it off
• Plasma


  Plasma is a liquid in the blood that carries:

  • Red and white blood cells and platelets
  • Nutrients like glucose and amino acids
  • Carbon dioxide from organs to lungs
  • Urea from liver to kidneys
  • Hormones
  • Proteins
  • Antibodies and antitoxins produced by white blood cells
• Platelets


  Platelets are small fragments of cells that have no nucleus. They help the blood clot at a wound so that you bleed less and let less microorganisms in. Lack of platelets causes excessive bleeding and bruising
• Blood vessels

  1. Arteries- carry blood away from the heart
  2. Capillaries- involved in exchange of material at the tissue
  3. Veins- carry blood to the heart
• How are arteries adapted to their job?

  • Artery walls are strong and elastic for high pressure
  • Thick walls compared to the lumen (hole) in the middle
  • Thick layers of muscle to make them strong and elastic fibres to allow them to stretch and spring back
• How are capillaries suited to their jobs?

  • Very narrow so they can squeeze between the gaps of cells meaning they can carry blood really close to every cell in the body to exchange substances
  • Permeable walls so substances can diffuse in and out
  • Supply food and oxygen and take away waste like CO2
  • One cell thick walls to increase diffusion by decreasing distance needed to travel
• How are veins suited to their jobs?

  • Walls are less thick as pressure is lower than arteries
  • Bigger lumen to help blood flow
  • Valves to help blood flow in the right direction.
• Circulatory system


  Mammals have a double circulatory system: in the first circuit, deoxygenated blood pumps from the heart to the lungs to take in oxygen and in the second circuit the oxygenated blood goes to the rest of the body to deliver oxygen, coming back once deoxygenated.
• The four chambers of the heart

  • Right atrium- receives deoxygenated blood from the body
  • This blood moves to the right ventricle-which pumps it to the lungs
  • Left atrium- receives oxygenated blood from the lungs
  • This blood moves to the left ventricle- which pumps it to the whole body
• The four major blood vessels of the heart

  Vena cava- brings deoxygenated blood into the heart

  Pulmonary artery- pumps out deoxygenated blood to the lungs

  Pulmonary vein- brings oxygenated blood into heart

  Aorta- pumps out oxygenated blood to the rest of the body
• The left ventricle of the heart has a much thicker wall than the right ventricle. It needs more muscle because it has to pump out blood around the whole body at a high pressure whereas the right ventricle only has to pump it to the lungs. Valves prevent the backflow of blood in the heart
• Heart diagram

  label the correct parts:

  A) right atrium

  B) right ventricle

  C) vena cava

  D) pulmonary artery

  E) left atrium

  F) left ventricle

  G) pulmonary vein

  H) aorta

  I) valves

  
• Cellular respiration


  Cellular respiration is an exothermic reaction which occurs continuously in living cells to release energy for metabolic processes, including aerobic and anaerobic respiration. It is the process of transferring energy from the breakdown of organic compounds. This energy is then used for metabolic processes, contracting muscles, maintaining a steady body temperature
• Whats the difference between anaerobic and aerobic respiration?

  Aerobic respiration requires a lot of oxygen. It happens in plants and animals. The equation:

  glucose+ oxygen > carbon dioxide+ water

  However anaerobic respiration doesnt use any oxygen and is much less efficient. Glucose is only partially broken down and lactic acid is produced. The equation:

  glucose > lactic acid

  It is also different in plants than animals. They produce ethanol and CO2 instead of lactic acid
• Cardiac output equation


  Cardiac output = heart rate/stroke volume
• Investigating rate of respiration- Part 1-5

  1. Soda lime granules are added to two test tubes. This absorbs CO2 produced by woodlice in the experiment
  2. A ball of cotton wool is placed above the soda lime. Woodlice are placed on top of the cotton wool in one tube, and glass beads in the other
  3. Respirometer is set up between the two tubes
  4. The syringe is used to set the fluid in the manometer to a known level
  5. The apparatus is then left for a set period of time in a water bath at 15 degrees
• Investigating rate of respiration- step 6-9

  6. During this time, there will be a decrease in the volume of air in the test tube containing the woodlice due to respiration

  7. The decrease in volume reduces the pressure in the tube causing the coloured liquid in the manometer to move towards the tube.

  8. The distance moved by the liquid in a given time is measured. This value can then be used to calculate the volume of oxygen take in by the woodlice per minute. This gives us the rate of respiration

  9. Repeat steps 1-8 in different temperatures of water bath to see how it impacts the rate.
• Investigating rate of respiration

  In aerobic respiration, organisms use oxygen from the air. By measuring the amount of air consumed by organisms in a given time, you can calculate their rate of respiration. Any live animal used should be treat ethically.