Unit 2 AQA Biology - Circulatory System

HideShow resource information
Preview of Unit 2 AQA Biology - Circulatory System

First 344 words of the document:

Circulatory system ­ Mammals
Why do large organisms need a transport system?
Increasing size means a decrease in the SA to Volume ratio.
Can no longer rely on simple diffusion and need to develop specialist exchange
surfaces (these are linked to transport systems).
Mammals are endothermic animals with a high metabolic rate and so they need an efficient
circulatory system to deliver large amounts of food and oxygen to living cells, and to take
away rapidly accumulating wastes. To achieve this mammals have a double circulation: a
pulmonary circulation and a systematic circulation.
Features of a Transport system:
A suitable medium in which to carry materials.
A form of mass transport in which the transport medium is moved around in bulk
over large distances.
A closed system of tubular vessels that contains the transport medium.
A mechanism for moving the transport medium within vessels.
Muscular contraction of the heart or body muscles.
Passive processes such as evaporation in plants.
A mechanism to maintain the mass flow in one direction.
A mechanism of controlling the flow of the transport medium
Transport system in mammals:
A suitable medium in which to carry materials - Blood
A form of mass transport in which the transport medium is moved around in bulk
over large distances.
A closed system of tubular vessels that contains the transport medium ­ Blood
vessels (arteries, veins and capillaries)
A mechanism for moving the transport medium within vessels - Muscular
contraction of the heart
A mechanism to maintain the mass flow in one direction ­ valves
A mechanism of controlling the flow of the transport medium ­ heart rate,
vasodilation, vasoconstriction
Single circulatory systems (e.g. fish):
Blood pressure reduced as blood passes through the gill
capillaries - slows down flow to the rest of the body
Limits the rate of delivery of O2 and nutrients to cells and
removal of waste

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Efficient for the level of activity of fish but not mammals ­ also fish do not maintain
their body temperature ­ need to respire relatively less compared to mammals
Double circulatory system:
Heart is composed of two separate pumps ­ right side
pumps blood to the lungs to pick up oxygen; the blood is
returned to the left side; the left side pumps oxygenated
blood rapidly and at high pressure to the body; the blood is
returned to the right side
Higher level of activity…read more

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »