comparing gas exchange in insects and mammals. added fish too. hope it helps
Compare:
Insects
Mammals
Environment
Terrestrial
Terrestrial
Oxygen available
21% of the air
21% of the air
Percentage of oxygen extracted from that
taken in
<25%
25%
Tube Strengthening Bands
Chitin Rings – heavy, around
Trachea
Cartilage Rings – light,
around Trachea, Bronchi and bronchioles
Association with transport system
None
Close
Haemoglobin
None
Yes
Ventilation – to increase volume of gases
across membranes during active periods and high cellular respiration needs.
Air sacs / Abdominal
contraction
Expand/contract the chest
cavity using the intercostals muscles and diaphragm.
Poikilothermic OR Homeothermic?
Poikilothermic
Homeothermic
SA:Vol
Highest
Lowest
(1) On
your own paper, write statements that give reasons for the similarities and
differences describe in the table above:
e.g. In insects a specialised gas exchange
system is necessary because of increased size and the lowering SA/vol ratio.
Tracheal systems or gills have high SA and maintain overall SA needed for gas
exchange. In fish a specialised gas
exchange system is necessary because of increased size and the lowering SA/vol
ratio. Gills have high SA and maintain overall SA needed for efficient gas
exchange. In mammals a specialised gas
exchange system is necessary because of increased size and the lowering SA/vol
ratio. Lungs have high SA and maintain overall SA needed for efficient gas
exchange.
All
groups need to ventilate – fish gulp water, insects pump their abdomen by
muscular contractions and mammals expand/contract the chest cavity using the
intercostals muscles as well as those of the diaphragm. These movements ensure that the gases are brought
to/taken from the gas exchange surfaces rapidly – this is especially important
in regions of low 02 e.g. fish in stagnant water, mammals and
insects at high altitudes and during times of high physical exercise. This is because the energy demands of
exercise require increased 02 for cellular respiration and need to
remove rapidly the CO2 produced in respiration or the blood becomes
to acid.
In fish and mammals the gases are
transported in the blood. The red blood
cells have the pigment haemoglobin which increases greatly the oxygen carrying
capacity of the blood. The blood of
insects does not have such a pigment as it does not carry oxygen. Lack of an O2 carrying pigment
and/or close association between the transport and gas exchange systems is less
efficient than other animal groups and imposes size limitations.
Fish
obtain O2 from water where it is in lower supply than air, hence the
adaptation of the counter current system to enhance the concentration gradient
of O2 and CO2 between water and blood. Insects and Mammals have much larger supply
of oxygen available to them and as a result their gas exchange systems are
nearly as efficient as extracting oxygen as that of the fish.
Insects
and Fish are poikilothermic and so
require less oxygen for respiration. Compared with mammals that are
homeothermic and require more oxygen for respiration.
(2) On
your own paper, make a statement relating to the animals way of life. Insects has been done for you:
The
Insect Gas Exchange System permits a high rate of metabolism because the oxygen
is taken directly to the body tissues but is not suitable for large animals
hence most insects are small.
The
Fish Gas Exchange System is restricted to water as gills collapse when not
supported by water. Gills internal and
this provides them with protection
The Mammal Lungs are internal for physical
protection and to prevent dehydration. Transport system returns blood to heart
before moving to body tissues and this increases efficiency of oxygen delivery
to body cells. Total reliance on gas
exchange via internal lungs. (dry skin) allows exploitation of a wider variety
of habitats, wet – dry, aquatic – terrestrial etc.
(3) On
your own paper, give reasons why each group could not survive with the gas
exchange system of another
e.g. Insects could not survive with a gill system
or lung system as a gill system would dry out quickly as it would not be
constantly bathed in water and a lung system requires a close association with
the transport system to allow transport of gases to all body cells.
Fish
could not survive with a tracheal system or lung system as a tracheal system
would be too heavy and lungs would require huge amounts of water to extract
sufficient oxygen.
Mammals
could not survive with a tracheal system or a gill system as a tracheal system
would not be able to diffuse gases quickly enough because mammals have a
smaller surface to volume ratio compared that of insects and a gill system
would dry out quickly as it would not be constantly bathed in water.