organisation in animals

• Levels of organisation in living organisms

  • Cells
  • Tissues
  • Organs
  • Organ systems
  • Organisms
• Cells


  Basic building blocks
• Tissues


  Groups of cells that have similar structures and functions
• Organs


  Groups of tissues working together to perform a specific function
• Organ systems


  Groups of organs working together
• Organisms


  Organ systems work together, forming an organism
• Digestive system


  1. Mouth (where food is chewed)

  2. Salivary glands (make saliva containing amylase enzyme)

  3. Oesophagus (carries food to stomach)

  4. Stomach (churns food, releases protease to digest proteins, releases hydrochloric acid to kill pathogens)

  5. Small intestine (where digested food is absorbed into blood)

  6. Large intestine (where water and minerals are absorbed into blood)

  7. Rectum (stores faeces)

  8. Anus (expels faeces)
• Pancreas


  • Makes enzymes: amylase, lipase, and protease
• Liver


  • Makes bile
• Gall bladder


  • Stores bile, which is alkaline to neutralise hydrochloric acid from stomach and emulsifies fat to form small droplets with large surface area
• Breathing


  1. Air moves into body through mouth and nose

  2. Down the trachea

  3. Into the bronchi

  4. Through the bronchioles

  5. Into the alveoli (air sacs)
• Oxygen diffuses into blood


  In the network of capillaries over the surface of the alveoli
• Components of blood


  • Red blood cells (bind to oxygen and transport it around body)
  • Plasma (transports substances and blood cells around body)
  • Platelets (form blood clots to create barriers to infections)
  • White blood cells (part of immune system to defend body against pathogens)
• Blood vessels


  • The structure of each blood vessel relates to its functions
• Vessel


  • Artery (high pressure)
  • Vein (low pressure)
  • Capillary
• Artery


  Carries blood away from the heart, has thick, muscular, and elastic walls that can withstand high pressure, small lumen
• Vein


  Carries blood to the heart, has thin walls, relatively large lumen, often has valves to stop blood flowing the wrong way
• Capillary


  Carries blood to tissues and cells, connects arteries and veins, has very thin walls (one cell thick) allowing short diffusion distance for substances to move between blood and tissues
• Double circulatory system


  1. Right ventricle pumps blood to the lungs for gas exchange

  2. Left ventricle pumps blood around the rest of the body
• The heart


  • The organ that pumps blood around the body, made of cardiac muscle tissue supplied with oxygen by the coronary artery
• Parts of the heart

  • Pulmonary artery (takes deoxygenated blood to the lungs)
  • Aorta (carries oxygenated blood around the body)
  • Vena cava (brings deoxygenated blood into the heart)
  • Pulmonary vein (brings oxygenated blood from the lungs)
  • Right atrium
  • Right ventricle (pumps blood to the lungs)
  • Left atrium
  • Left ventricle (pumps blood around the body)
• Heart rate


  Controlled by a group of cells in the right atrium that generate electrical impulses, acting as a pacemaker
• Artificial pacemaker


  Can be used to control irregular heartbeats
• Tissue


  A group of cells with similar structures and functions
• Organ


  A group of tissues working together to perform a specific function
• Function of the liver in digestion

  Produces bile, which neutralises hydrochloric acid from the stomach and emulsifies fat to form small droplets with a large surface area
• Function of saliva in digestion

  Lubrication to help swallowing, contains amylase to break down starch
• Enzymes produced in the pancreas

  • Amylase
  • Protease
  • Lipase
• Main components of blood

  • Red blood cells
  • White blood cells
  • Plasma
  • Platelets
• Function of platelets


  Form blood clots to prevent the loss of blood and stop wounds becoming infected
• Adaptations of a red blood cell

  • Bi-concave disc shape
  • Large surface area-to-volume ratio for diffusion of oxygen
  • Contains haemoglobin to bind to oxygen
  • No nucleus to have more space for oxygen
• How white blood cells protect the body

  Engulf pathogens, produce antitoxins to neutralise toxins, or antibodies
• Substances transported in blood plasma

  • Hormones
  • Proteins
  • Urea
  • Carbon dioxide
  • Glucose
• Double circulatory system


  Blood passes through the heart twice for every circuit around the body - deoxygenated blood is pumped from the right side of the heart to the lungs, and the oxygenated blood that returns is pumped from the left side of the heart to the body
• Structure of an artery

  Carries blood away from the heart under high pressure, has a small lumen and thick, elasticated walls that can stretch
• Structure of a vein

  Carries blood back to the heart at low pressure, doesn't need thick, elasticated walls, but has valves to prevent blood flowing the wrong way
• Structure of a capillary

  Carries blood to cells and tissues, has a one cell thick wall to provide a short diffusion distance
• Active transport in the small intestine allows sugars to be absorbed when the concentration of sugar in the small intestine is lower than the concentration of sugar in the blood
• Therapeutic cloning


  Patient's cells are used to create an early embryo clone of themselves, stem cells from the embryo can then be used to treat the patient's medical conditions
• Stem cell


  Undifferentiated cell that can differentiate into one or more specialised cell types