3.1.2 Transport in Animals

Question 1

Why do multicellular organisms require

transport systems?

Answer 1

● Large size (small surface area to volume
ratio), subsequently high metabolic rates.
● Demand for oxygen is high, so need a
specialised system to ensure a strong supply
to all respiring tissues.

Question 2

Summarise the different types of

circulatory system.

Answer 2

● Open= blood can diffuse out of vessels e.g. insects
● Closed= blood confined to vessels e.g. fish, mammals
○ Single= blood passes through pump once per
circuit of the body
○ Double= blood passes through heart twice per
circuit of the body

Question 3

Relate the structure of arteries to their

function.

Answer 3

Thick, muscular walls to handle high
pressure without tearing. Elastic tissue
allows recoil to prevent pressure surges.
Narrow lumen to maintain pressure.

Question 4

Relate the structure of veins to their

function.

Answer 4

Thin walls due to lower pressure.
Require valves to ensure blood doesn’t
flow backwards. Have less muscular
and elastic tissue as they don’t have to
control blood flow.

Question 5

Relate the structure of capillaries to their

function.

Answer 5

● Walls only one cell thick; short diffusion pathway.
● Very narrow, so can permeate tissues and red
blood cells can lie flat against the wall, effectively
delivering oxygen to tissues.
● Numerous and highly branched, providing a
large surface area.

Question 6

Relate the structure of arterioles and

venules to their function.

Answer 6

● Branch off arteries and veins in order to feed
blood into capillaries.
● Smaller than arteries and veins so that the
change in pressure is more gradual as blood
passes through increasingly small vessels.