OCR A Biology A level notes on exchange surfaces, transport in animals and transport in plants. Cornell notes with diagrams and key words. Summarised notes and easy to understand. Achieved A* using these notes. Contains everything the specification requires since written against the specification.
Corne 3.1.1f ns when and they carry air into the insects
ll Mechanisms of oxygen body. The tubes are lined by spirals
Notes ventilation and demands build of chitin, which keep them open if
gas exchange in up e.g. insect they are bent or pressed.
fish and insects is flying? Chitin is relatively impermeable to
Insects have an gas to little gaseous exchange occurs
exoskeleton which How is in the trachea.
does enable gaseous
gaseous exchange exchange The trachea divides into tracheoles.
to take place, controlled? Each tracheole is a single, greatly
What elongated cell with no chitin lining so
are therefore insects
have evolved to What are they are freely permeable to gas.
spiracl
deliver the oxygen alternative Trachioles are spread throughout the
es?
directly to the cells methods of tissues of the insect and a large
and to remove the increasing the number of tracheoles run between
carbon dioxide in level of cells and into the muscle fibres (the
the same way. gaseous site of gas exchange).
exchange?
Spiracles are small In most insects, air moves along the
openings along the trachea and tracheoles by diffusion
What thorax and alone, reaching all the tissues. The
is the abdomen of most vast number of tiny tracheoles give a
trache insects which has very large SA for gaseous exchange.
a? valves. Spiracles Oxygen dissolves in moisture on the
allow air to enter walls of the tracheoles and diffuses
(and leave) the into the surrounding cells.
insect and flow
into the system of Towards the end of the tracheoles
trachea. there is tracheal fluid which limits the
penetration of air for diffusion.
Spiracles contain
sphincters which A lactic acid build up in the tissues
allow the spiracles results in water moving out of the
to be open or tracheoles by osmosis which exposes
closed. The more SA for gaseous exchange.
spiracle sphincters
are kept closed as
much as possible The extent of gas exchange in most
to minimise water insects is controlled by the opening
loss. and closing of the spiracles.
Trachea are tubes - Mechanical ventilation of the
What
within the insect trachea system – air is actively
is
respiratory system pumped into the system by
trache
which lead to muscular pumping movements of
al
tracheoles. These the thorax and abdomen.
fluid?
are the largest - Collapsible enlarged trachea or
tubes of the insect air sacs, which act as air
reservoirs. They are used to
What respiratory increase the amount of air moved
happe system, up to through the gas exchange
1mm in diameter
1
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