Summary
Summary Circulatory systems of mammals
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- AQA
Year 1 Biology AQA A level notes. Achieved an A* in my final exam using these notes. They are based on the mark scheme requirements.
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Circulatory systems of mammals16 March 2023 13:02
Large transport systems
- SA: vol ratio decreases- needs of organism cannot
be met by body surface alone
- Specialist exchange surfaces are required- absorb
nutrients and respiratory gases and remove
excretory products
- Transport system is required to take materials
from cells to exchange surfaces and from
exchange surfaces to cells
- Tissues and organs have become more
specialised
- The lower the surface area to volume ratio, the
more active the organism- the greater the need
for a specialised transport system with a pump
Features of transport systems
- Suitable medium to carry materials - ie blood-
usually liquid based on water as it can readily
dissolve substances and can be moved around
easily
- Form of mass transport in which transport
medium is moved in bulk over large distances-
more rapid than diffusion
- Closed system of tubular vessels - contains
transport medium and forms a branching
network to distribute it to all parts of the
organism
- Mechanism for moving the transport medium
within vessels- requires pressure difference
between one part of the system and another
Achieved in two main ways
1. Muscular contraction of body muscles of
specialised pumping organ, ie heart
2. Plants rely on natural passive processes such as
evaporation of water
- Mechanism to maintain the mass flow movement
in one direction- ie valves
- Means of controlling the flow of the transport
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