8.1 Transport Systems in Multicellular Animals

• Why do multicellular organisms need transport systems?

  to supply oxygen and nutrients to the sites where they are needed and to remove waste products from the individual cells
• In single-celled organisms what 5 processes can supply everything the cell needs to import or export?

  diffusion, osmosis, active transport, endocytosis, exocytosis
• Why are specialised transport systems needed in animals?

  metabolic demands, surface area to volume ratio, removal of waste products, enzyme + hormone transport, food digestion products transport for respiration
• Why do animals need specialised transport systems because of their metabolic demands?


  high metabolic demands + produce lots of waste products so diffusion over the long distances is not enough to supply the quantities needed
• Why do animals need specialised transport systems because of their surface area to volume ratio?


  ratio gets smaller as multicellular organisms get bigger - diffusion distances get bigger but amount of surface area available to absorb or remove substances gets relatively smaller
• Why do animals need specialised transport systems for enzyme and hormone transport?

  enzymes or hormones may be made in one place but needed in another
• Why do animals need specialised transport systems for removal of waste products?

  waste products of metabolism need to be removed from the cells and transported to excretory organs
• Why do animals need specialised transport systems for food digestion products transport for respiration?


  food will be digested in one organ system, but needs to be transported to every cell for use in respiration and other aspects of cell metabolism
• What are the 3 features most circulatory systems have in common?

  liquid transport medium that circulates around the system, vessels that carry the transport medium, pumping mechanism to move fluid around system
• What is a mass transport system?

  when substances are transported in a mass of fluid with a mechanism for moving the fluid around the body
• What do specialised circulatory systems carry?

  gases, nutrients, waste products, hormones
• What are the 3 types of circulatory system?

  open, single closed, double closed
• Where are open circulatory systems found mainly?

  invertebrate animals, including most insects and molluscs
• Where is blood pumped from the heart to in an open circulatory system?

  haemocoel
• What is the open body cavity called?

  haemocoel
• What is the pressure in the haemocoel?

  low
• Where does exchange take place in open circulatory systems?

  haemolymph comes into direct contact with tissues and cells
• How does haemolymph return back to the heart?

  open-ended vessel
• Where does gas exchange take place in insects?

  tracheal system
• What is insect blood called?

  haemolymph
• What 3 things does haemolympth transport?

  food, nitrogenous waste products, cells involved in defence against disease
• What is the body cavity split by in insects?

  membrane
• Where is the heart in insects?

  extends along length of thorax and abdomen
• The haemolymph circulates but steep diffusion gradients cannot be maintained for efficient diffusion
• The amount of haemolymph flowing to a particular tissue cannot be varied to meet changing demands
• Why does blood not come directly in contact with cells in closed circulatory system?

  blood is enclosed in blood vessels
• Where does blood return to in closed circulatory systems?

  heart
• How does the heart pump blood around the body in closed circulatory system?

  under pressure and relatively quickly
• How can the amount of blood flowing to particular tissue be adjusted in closed circulatory system?

  by widening or narrowing blood vessels
• What do most closed circulatory systems contain?

  blood pigment that carries respiratory gases
• Which animals are closed circulatory systems found?


  echinoderms, cephalopod molluscs, annelid worms, all vertebrate groups including mammals
• Which animals are single closed circulatory systems found in?

  fish and annelid worms
• Where does blood travel in a single circulatory system?

  blood travels only once through the heart for each complete circulation of the body
• Where does blood pass through before it returns to the heart in a single closed circulation?

  2 sets of capillaries
• What happens when blood passes through the first set of capillaries in single closed circulation?

  exchanges oxygen and carbon dioxide
• What happens when blood passes through the second set of capillaries in single closed circulation?

  substances are exchanges between the blood and the cells
• Why does blood return to the heart slowly in single closed circulation?

  result of passing through 2 sets of capillaries, blood pressure drops considerably
• Why does the activity of animals with single closed circulations tend to be low?

  blood returns to heart slow, limiting the efficiency of exchange processes
• What animal has a relatively efficient single circulatory system?

  fish
• Explain how fish can be so active with a closed single circulatory system

  countercurrent gaseous exchange mechanism in gills that allows lots of oxygen to be taken from water, body weight supported by water and they do not maintain their body temp - greatly reduces metabolic demands