3.1.5 Gas exchange in other organisms Flashcards
How do bony fish exchange gas?
-Exchange gases with the water in which they live.
-They use their gills to absorb oxygen. dissolved in the water and release CO2 into the water.
-O2 concentration will be much lower than in the air.
Explain the anatomy of the gaseous exchange system in bony fish.
Bony fish have five pairs of gills which are covered by a bony plate called the operculum.
-Each gill consists of two rows of filaments attached to a bony arch.
-Filaments are thin and surface is folded into many secondary lamellae.
What do the lamellae provide?
A large surface area, blood capillaries carry deoxygenated blood close to the surface of the secondary lamellae where exchange takes place
What is the countercurrent flow?
-Blood flows along the gill arch and out along the filaments to the secondary lamellae.
-The blood then flows through capillaries in the opposite direction to the flow of water over the lamellae. This creates a countercurrent flow.
What is an advantage of the countercurrent flow?
It absorbs the maximum amount of oxygen in the water.
How can bony fish keep ventilated?
-They can keep water flowing over the gills by using a buccal-opercular pump.
-The buccal cavity can change volume.
-Floor of mouth moves downwards drawing water in.
-Mouth closes and the floor is raised again by pushing water through the gills
-movement of the operculum are coordinated with the buccal cavity
-As water is pushed from the buccal cavity the operculum moves outwards
-Movement reduces pressure in opercular cavity helping water to flow through the gills.
What circulatory system do insects have?
An open circulatory system, they do not transport oxygen in blood. Circulation is slow and can be affected by body movements.
Explain how the tracheal system works.
-Supplies air directly to all the respiring tissues.
-Air enters the system by a spiracle.
-Air is transported into the body through tubes called tracheae
-These divide into smaller tubes called tracheoles.
-Ends of trachoeles are open and filled with tracheal fluid.
-Gaseous exchange occurs between the air in the tracheole and the tracheal fluid.
-Some exchange can also occur across the thin walls of the tracheoles.
What happens when insect’s tissues are active
-The tracheal fluid can be withdrawn into the body fluid in order to increase the surface area of the tracheole wall exposed to air.
-This means more oxygen can be. absorbed when the insect is active.
How do larger insects ventilate their tracheal systems?
-By movements of the body. This can be achieved by:
-Flexible walls, acts as air sacs that can be squeezed by action of the flight muscles. Repetitive contraction ventilate the system
-Movement of wings: Change size of thorax, as volume decreases air in tracheal system is put under pressure and air is pushed out . vice versa when volume increases.
-Locusts can. change size of volume of abdomen by specialised breathing movements, these co-ordinate with valves in the spiracles
