Transport Systwms In Multicelluclar Animals

Question 1

Why do animals need specialised transport systems

Answer 1

• the metabolic demands of the animals are too high (they need too much food and oxygen) diffusion over long distances isn’t enough
• the surface area to volume ratio gets smaller as organisms get bigger, the surface area to absorb or remove substances gets relatively smaller
• molecules such as enzymes and hormones are made in one place but are needed in another
• 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
• waste products of metabolism need to be removed from the cells and transported to excretory organs

Question 2

What is a specialised circulatory system

Answer 2

-they carry gases such as oxygen and carbon dioxide, nutrients , waste products and hormones around the body

Question 3

What is a mass transport system

Answer 3

-when substances are transported in a mass of fluid with a mechanism for moving fluid around the body

Question 4

What do most circulatory systems have in common

Answer 4

• they have a liquid transport medium that circulates around the system
• they have vessels that carry the transport medium
• they have a pumping mechanism to move the fluid around the system

Question 5

What is an open circulatory system

Answer 5

• this is where there are very few vessels to contain the transport medium. It is pumped straight from the heart into the body cavity.
• the open body cavity is called the haemocoel, in the haemocoel the transport medium is under low pressure and comes into direct contact with tissues and other cells
• the transport medium returns to the heart through open ended vessel

Question 6

What is a closed circulatory system

Answer 6

• the blood is enclosed in blood vessels and does not come into direct contact with cells of the body.
• the heart pumps blood around the body under pressure and it returns directly to the heart
• substances leave and enter blood by diffusion
• the amount of blood flowing to a particular tissue can be adjusted by widening or narrowing blood vessels

Question 7

What is a single closed circulatory system

Answer 7

• a single closed circulatory system is where a full circulation includes blood passing through the heart once and to the rest of the body
• it has 2 sets of capillaries one that exchanges O2 and CO2 the other set exchanges substances between the blood and the other cells
• the narrow capillaries causes blood pressure to drop so blood takes longer to get back to the heart, this causes low activity rates

Question 8

Why have Fish got high activity rates with a single closed circulatory system

Answer 8

• fish have a counter-current gaseous exchange mechanism which allows them to take a lot of oxygen from the water
• their body weight is supported by the water
• they do not maintain their own temperature
• this reduces metabolic demand allowing them to be more active

Question 9

What is a double closed circulatory system

Answer 9

• involves 2 separate circulations
• blood is pumped from the heart to the lungs to pick up oxygen and unload CO2 then returns to the heart
• blood is pumped though the heart to the body and returns to the heart
• blood is only passed through 1 capillary network so high blood pressure and fast flow of blood is maintained