B4 - Organising animals and plants

• The circulatory system


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


  bind to oxygen and transport it around the body
• Plasma


  transports substances and blood cells around the body
• Platelets


  form blood clots to create barriers to infections
• White blood cells


  part of the immune system to defend the body against pathogens
• Blood vessels


  • Arteries
  • Veins
  • Capilliaries
• Veins


  • carries blood away from the heart
  • high prsssure
  • thick, muscular, elastic walls
  • the walls can stretch and withstand high pressure
  • small lumen
• Veins

  • carries blood to the heart
  • low pressure
  • have valves to stop blood flowing the wrong way
  • thin walls
  • large lumen
• Capillaries 


  • carries blood to tissues anf cells
  • connects arteries and veins
  • one cell thick
  • short diffusion distance for substances to move between the blood and the tissues
  • very narrow lumen
• The heart


  • the organ that pumps blood around the body
  • made from cardiac tissue
  • supplied with oxygen by the coronary artery
• Right atrium


  • Pulmonary artery
  • takes deoxygenated blood to the lungs
  • Vena cava
  • brings deoxygenated blood into the heart
  • Right ventricle
  • pumps blood to the lungs
• Left atrium


  • Aorta
  • carries oxygenated blood around the body
  • Pulmonary vein
  • brings oxygenated blood from the lungs
  • Left ventricle
  • pumps blood around the body
• Pacemaker


  • a group of cells in the right atrium
  • generate electrical impulses
  • control heart rate
• Artificial pacemakers can be used to control irregular heartbeats
• Double circulatory system


  • blood passes through the heart twice for every circuit around the body
  • the right ventricle pumps blood to the lungs where gas exchange takes place
  • the left ventricle pumpls bood around the rest of the body
• The lungs


  • During breathing, air moves:
  • into the body through the mouth and nose
  • down the trachea
  • into the bronchi
  • through the bronchioles
  • into the alveoli
  • Oxygen then diffuses into the blood in the network of capillaries over the surface over the surface of the alveoli
• Leaves


  • Waxy cuticles
  • Upper epidermis
  • Palisade mesophyll
  • Spongy mesophyll
  • Stomata
  • Guard cells
• Waxy cuticle


  • makes the leaf waterproof
• Upper epidermis


  • single layer of cells
  • protects against water loss
  • transparent to allow light to pass through
• Palisade mesophyll


  • tightly packed cells
  • lots of chloroplasts to absorb light for photosynthesis
• Spongy mesophyll


  • spherical cells
  • lots of air spaces to allow gases to diffuse quickly
  • large surface area-to-volume ratio to increase gas exchange
• Stomata


  • tiny openings on the lower surface of the leaf
  • allow gases to move in and out of the leaf
• Guard cells


  • control the opening and closing of the stomata
• Stomat


  • tiny openings in the underside of leaves
  • reduces water loss through evaporation
  • allow carbon dioxide into the plant for photosynthesis
  • allowing diffusion of oxygen out of the plant
  • guard cells open and close the stomata
• Transpiration


  • Water is lost through the stomata by evaporation
  • This pulls water up from the roots through the xylem and is called transpiration
  • The constant movement of water up the plant is called the transpiration stream
• Transpiration 


  • provides water to cells to keep them turgid
  • provides water to cells for photosynthesis
  • transports mineral ions to leaves
• Xylem


  • one way transport only
  • transports water and minerals
  • made of dead cells, jointed together with no end walls between them
  • thick walls stuffed with lignin
• Translocation


  • the movement of dissolved sugars from the leaces to the rest of the plant
  • takes place in the phloem
• Translocation


  • moves dissolved sugars made in the leaves during photosynthesis to other parts of the plant
  • allows for respiration, growth and glucose storage
• Phloem


  • transports water and dissolved sugars
  • cells have end walls with small holes to allow substances to flow through
  • substances transported in both directions
• Factors affecting transpiration


  • Temperature
  • Humidity
  • Wind speed
  • Light intensity
• Affect of temperature on transpiration

  • higher temperature increases the rate of transpiration
  • water evaporates faster in higher temperatures
• Affect of humidity on transpiration


  • lower humidity increases the rate of transpiration
  • the drier the air, the steeper the concentration gradient of water molecules betweeent he air and leaf
• Affect of wind speed on transpiration


  • more wind increases the rate of transpiration
  • wind removes te water vapour quickly, maintaining a steeper concentration gradient
• Affect of light intensity on transpiration


  • higher light intensity increases the rate of transpiration
  • the stomata open wider to let more carbon dioxide into the leaf for photosynthesis
• Root hair cells


  • increase absorbtion of water and mineral ions into the root by increasing the root surface area
  • contain lots of mitochondria to transfer energy, which is used to take in mineral ions by active transport