Chapter 13- exchange and transport

includes gas exchange in fish, insects and plants. also about the strusture of arteries, arterioles, veins and capillaries.

HideShow resource information
  • Created by: malu
  • Created on: 27-06-13 19:44
Preview of Chapter 13- exchange and  transport

First 274 words of the document:

Once substances are absorbed, the materials need to be rapidly distributed all
around the body because cells need them and the waste products are returned to
the exchange surface for removal. Therefore a transport system is
The size and the metabolic rate of an organism will
affect the amount of the material need to be exchanged and the type of exchange
surface needed. Examples of things which need to be interchanged between an
organism are:-
Respiratory gases (oxygen, CO2)
Nutrients (glucose, proteins etc.)
Excretory products
This can take place in two ways:-
Passively (diffusion and osmosis)
Actively (active transport)
Surface area to volume ratio
Surface area should be large compared to volume for efficient
exchange (there are exceptions). As the organism becomes larger,
the volume of the organism increases at
a faster rate than its surface area. This
would prevent the cells in a large organism from receiving
the necessary materials (simple diffusion is prevented).
To overcome this problem, organisms have evolved:-
A flattened shape so that no cell is ever far from the
surface (e.g. flat worm)
Specialised exchange surfaces with large area to
increase the surface area to volume ration (gills in
Features of a specialised exchange surfaces
· A large surface area to volume ratio to increase the rate of
· Very thin so that the diffusion distance is shorter and therefore increases
the rate of exchange

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

Partially permeable to allow selected material to cross through without
· Movement of environment medium e.g. air, diffusion gradient
· Movement of internal medium e.g. blood
surface area*difference in concentration
Diffusion length of diffusion path
Exchange surfaces are often situated inside the organism because they are very
thin therefore they are easily damaged.
Gas exchange in single celled
Single celled organisms are very small and therefore they have a
large surface area to volume ratio.…read more

Page 3

Preview of page 3

Here's a taster:

Most insects are terrestrial (live on land). Water easily evaporates from the surface
of their bodies and they can easily become dehydrated. Therefore they need to
conserve water.
To reduce water lose, terrestrial organisms has:-
Waterproof covering- this covering is rigid and when water evaporates
the water proof layer doesn't allow it to go out. This helps to keep water inside.
Small surface are to volume ratio- minimises the area over which
water is lost.…read more

Page 4

Preview of page 4

Here's a taster:

Respiratory gases move in and out in two ways:-
Along a diffusion gradient- oxygen is used up when
cells are respiring, so concentration of oxygen decreases towards the end
of the tracheoles and creates a diffusion gradient that causes the oxygen
from atmosphere to diffuse into tracheae and then tracheoles. CO2
produced in the respiration diffused out of the body... cells tracheoles
tracheae atmosphere
Ventilation- the movement of muscles can create mass movements
of air in and out of the tracheae.…read more

Page 5

Preview of page 5

Here's a taster:

This is known as COUNTER
CURRENT FLOW. If blood flow in the same direction as water, then
far less gas exchange would take place.
The blood and the water that flow over the gill lamellae in opposite directions,
this arrangement means that:
Blood that is already well loaded with oxygen meets water with its maximum
concentration of oxygen (i.e. 100%).…read more

Page 6

Preview of page 6

Here's a taster:

The efficient supply of materials over larger distances requires a mass transport
Transport system depends on:-
The surface area to volume ratio
How active the organism is
The lower the surface area to volume ratio and the more active
the organism, the greater is the need for a specialised
transport system with a pump.
Features of transport system
A suitable medium in which to carry materials. E.g. blood.…read more

Page 7

Preview of page 7

Here's a taster:

A mechanism for moving the transport medium within the
vessels. This requires a pressure difference b/w one part of the system and
another. this is achieved in two ways:-
Animals use muscular contraction or special ump like heart
Pants use passive natural physical processes such as the evaporation of
A mechanism to maintain the mass flow movement in one
direction. E.g.…read more

Page 8

Preview of page 8

Here's a taster:

The volume and types of gases that are being exchanged by a plant leaf depends
on the balance between the rates of photosynthesis and
When photosynthesis is taking place some CO2 from respiration is used and
some from external air. In the same way oxygen from photosynthesis is used in
respiration but most of it diffuses out.
When photosynthesis is not occurring e.g. in the dark oxygen diffuses into the
leaf because it is used in respiration.…read more

Page 9

Preview of page 9


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »