Transport in Animals Revision Notes
Transport Systems
Need for a Transport System
-single cell organisms – rely on diffusion as it is quick enough and very close to the environment
-multicellular organisms – diffusion pathway too long and slow, need a separate system
-transport systems are needed because
Metabolic Demands – need lots of oxygen and food and produce lots of waste – diffusion cannot supply quantities needed
Surface Area : Volume Ratio – ratio gets smaller so the diffusion distances get bigger and surface area exposure becomes smaller
Molecules – molecules such as enzymes and hormones are made in one place but needed in another hence they need transporting
Food – will be digested in one organ but will needed to be transported around the body so the cells can respire
Waste Products – need to be removed so they don’t build up and become toxic
Features of a Good Transport System
Transport Medium – carries nutrients, oxygen and wastes around the body [blood]
Pump – to create a pressure which will push the transport medium around the body [heart]
Exchange Surfaces – enable substances to enter and leave the blood when needed [capillaries]
Tubes/Vessels – to contain the transport medium by mass flow
Two Circuits – one to pick up oxygen; the other to deliver oxygen to the tissues
Single and Double Circulatory
Single Circulatory System
-flows through the heart once for one complete circuit
In a Fish ( heart → gills → body → heart)
o Blood pressure drops as blood passes through the tiny capillaries of the gills
o Blood pressure is low when flowing towards the body – not very quickly
o Rate at which oxygen and nutrients to tissues and carbon dioxide and urea are removed is limited
-not as metabolically active as mammals – do not maintain body temperature – need less energy. Sufficient for their needs
Double Circulatory System
-flows through the heart twice for one complete circuit
In a Mammal ( heart → body → heart → lungs → heart)
o Blood pressure not too high in the pulmonary circulation (lungs) as it may damage delicate capillaries in lungs
o Heart increases blood pressure after the lungs, so it flows to the body under high pressure – more quickly
o Systemic circulation (body) can carry blood at a higher pressure than pulmonary circulation (lungs)
-mammals maintain body temperature – need lots of energy from food released from respiration – need good supply & removal of substances
Open and Closed Circulatory Systems
Open Circulatory Systems
-blood not held in vessels and flows through the body cavity so the tissues and cells are directly bathed in blood
-movements of the body help circulate the blood (without movement, blood stops moving so oxygen and nutrients are not transported)
-muscular pumping organ (like a heart)
Blood enters long tube (under dorsal – upper body) through pores called ostia
Heart pumps blood towards head by peristalsis (then pores into body cavity)
-larger insects [Locusts] have tubes attached to heart directing blood flow to legs/wings etc.
Disadvantage to Closed Circulatory:
-blood pressure is low and blood flow is slow
-circulation of the blood may be affected by body movements or lack of body movements
Closed Circulatory Systems
-in larger animals
-blood stays entirely in vessels and a separate fluid – tissue fluid – baths the tissues and cells
Advantages Over Single Open Circulatory:
-higher pressure so blood flows more quickly
-more rapid delivery of oxygen and nutrients
-more rapid removal of carbon dioxide and other wastes
Transport Systems
Need for a Transport System
-single cell organisms – rely on diffusion as it is quick enough and very close to the environment
-multicellular organisms – diffusion pathway too long and slow, need a separate system
-transport systems are needed because
Metabolic Demands – need lots of oxygen and food and produce lots of waste – diffusion cannot supply quantities needed
Surface Area : Volume Ratio – ratio gets smaller so the diffusion distances get bigger and surface area exposure becomes smaller
Molecules – molecules such as enzymes and hormones are made in one place but needed in another hence they need transporting
Food – will be digested in one organ but will needed to be transported around the body so the cells can respire
Waste Products – need to be removed so they don’t build up and become toxic
Features of a Good Transport System
Transport Medium – carries nutrients, oxygen and wastes around the body [blood]
Pump – to create a pressure which will push the transport medium around the body [heart]
Exchange Surfaces – enable substances to enter and leave the blood when needed [capillaries]
Tubes/Vessels – to contain the transport medium by mass flow
Two Circuits – one to pick up oxygen; the other to deliver oxygen to the tissues
Single and Double Circulatory
Single Circulatory System
-flows through the heart once for one complete circuit
In a Fish ( heart → gills → body → heart)
o Blood pressure drops as blood passes through the tiny capillaries of the gills
o Blood pressure is low when flowing towards the body – not very quickly
o Rate at which oxygen and nutrients to tissues and carbon dioxide and urea are removed is limited
-not as metabolically active as mammals – do not maintain body temperature – need less energy. Sufficient for their needs
Double Circulatory System
-flows through the heart twice for one complete circuit
In a Mammal ( heart → body → heart → lungs → heart)
o Blood pressure not too high in the pulmonary circulation (lungs) as it may damage delicate capillaries in lungs
o Heart increases blood pressure after the lungs, so it flows to the body under high pressure – more quickly
o Systemic circulation (body) can carry blood at a higher pressure than pulmonary circulation (lungs)
-mammals maintain body temperature – need lots of energy from food released from respiration – need good supply & removal of substances
Open and Closed Circulatory Systems
Open Circulatory Systems
-blood not held in vessels and flows through the body cavity so the tissues and cells are directly bathed in blood
-movements of the body help circulate the blood (without movement, blood stops moving so oxygen and nutrients are not transported)
-muscular pumping organ (like a heart)
Blood enters long tube (under dorsal – upper body) through pores called ostia
Heart pumps blood towards head by peristalsis (then pores into body cavity)
-larger insects [Locusts] have tubes attached to heart directing blood flow to legs/wings etc.
Disadvantage to Closed Circulatory:
-blood pressure is low and blood flow is slow
-circulation of the blood may be affected by body movements or lack of body movements
Closed Circulatory Systems
-in larger animals
-blood stays entirely in vessels and a separate fluid – tissue fluid – baths the tissues and cells
Advantages Over Single Open Circulatory:
-higher pressure so blood flows more quickly
-more rapid delivery of oxygen and nutrients
-more rapid removal of carbon dioxide and other wastes
