2.2 Flashcards
What affects rate of diffusion
Surface area
Diffusion pathway
Concentration gradient
Unicellular organisms gas exchange
High surface area to volume ratio
Small distance to centre - short diffusion pathway
Dont need specialised gas exchange surfaces
What is the gas exchange surface of Amoeba
Cell membrane
Flatworms gas exchange
Multicellular Long and flat High surface area:volume Short diffusion path to centre of the body No specialised gas exchange surface
Gas exchange surface of the flatworm
External body surface
Earthworms gas exchange
Multicellular
Terrestrial
Long cylindrical shape - high SA:V
Diffusion distance to centre is too large for diffusion alone to supply oxygen at a sufficient rate to sustain metabolic requirements
Closed Circulatory system - maintain diffusion gradients
Blood vessels close to external surface - short diffusion path to blood
No specialised gas exchange surface
What is the gas exchange surface of an earthworm
External body surface
Amphibia gas exchange
Multicellular animals
Aquatic and terrestrial modes of life
Thin moist skin
Closed circulatory system - at rest is it sufficient to supply the oxygen needs
Active - primitive lungs which are internal to reduce water and heat loss
Not highly folded like mammals but do increase SA
List the general features of specialised gas exchange surface of larger multicellular animals
- large surface area
- short diffusion pathway
- ventilation mechanisms
- permeability to gases
- moist surfaces
Why are ventilation mechanisms needed in gas exchange
To maintain a concentration gradient
Why is a moist surface needed
Oxygen can dissolve in water and diffuse across gas exchange surface
What features of gas exchange surfaces help to maintain diffusion gradients
Ventilation mechanisms
Circulation of blood
What is the surface of fish covered in
Scales - impermeable to water and gases
Where do fish exchange gases
Gills - gill filaments and gill plates
What are gills covered by
Operculum
What does the operculum do
Open to let stale water out
Close to increase pressure within gill cavity during ventilation movements le
What does each gill cavity contain
4 gills supported on bony gill arches
Describe the structure of gills
Feathery
Consist of many gill filaments
What are the gill filaments covered with
Many lamellae/gill plates at right angles to increase surface area
Describe lamellae of fish
Very thin and close to capillaries - short diffusion path for oxygen and carbon dioxide
Function of gill rakers
Filter large particles out of the water preventing damage to delicate gill filaments
Where are gill rakers found
Other side of gill arches