2.2 Adaptations for gaseous exchange Flashcards
What must all respiratory surface be? And why
- thin (short diffusion pathway)
- permeable to gases
- moist (allows gases to dissolve)
- large S.A : Vol ratio
What are some additional features not present in single celled organisms, insects or plants?
- good blood supply to maintain the conc gradient
- ventilation mechanism to maintain conc gradient
As organisms increase in size, what is required? Why?
a specialised gas exchange surface is required to increase the area available
Give an example of an unicellular organism, why doesn’t it need a specialised gas exchange surface?
Amoeba
- the S.A is large enough to meet the needs of the organism and therefore the materials can be exchanged directly across its thin and permeable membrane
Why is the conc gradient always maintained in unicellular organisms?
bc the cytoplasm is constantly moving
Why do larger organisms need a specialised gas exchange surface?
the S.A : Vol ratio decreases so diffusion across body surface doesn’t meed the needs of the organism
What is a consequence of maintaining a moist respiratory surface in terrestrial animals? How is this minimised?
water loss, minimised by having internal gas exchange surface: lungs
What is the adaptation for gas exchange in a Flatworm?
flattened body to reduce diffusion distance and to increase overall S.A
What are the adaptations for gas exchange in a Earthworm?
- secretes mucus to maintain a moist surface
- low metabolic rate to reduce O2 requirements
- network of blood vessels and blood containing haemoglobin for the transport of O2
- CO2 is transported largely in the blood plasma
What are the adaptations for gas exchange in Amphibians? eg frogs and newts
- moist and permeable skin w/well developed capillary network beneath the surface
- lungs that are used when more active
What are the adaptations for gas exchange in Reptiles? eg snakes
- internal lungs like amphibians, but more complex and larger surface
What are the adaptations for gas exchange in Birds?
- flight generates a high metabolic rate and high O2 requirement so birds have efficient ventilation mechanism to increase the conc gradient across the lung surface
What are a fish’s specialised gas exchange surface? What else does this mechanism contain?
- gills which have gill filaments, gill rakers ad gill arches and lamellae (gill plates)
How do gills have a large S.A?
due to gill filaments
Why must water be forced over the gill filaments in aquatic organisms?
water is a dense medium w/low O2 content so water must be forced over the gill filaments
What prevents gills from collapsing?
The gill filaments
Why do fish die out of water?
b/c the gills collapse and the filaments stick together, reducing the S.A for absorption of O2
Why do the gills have an extensive network of capillaries?
to allow efficient diffusion of O2
What are the two types of different fish and their different mechanisms?
- Cartilaginous fish - parallel flow
- Bony fish - counter-current flow
How do cartilaginous fish ventilate their gills?
They swims and open their mouths, allowing H2O to pass over the gills
Why is gas exchange only possible over part of the gill filament surface?
As an equilibrium is reached which prevents further diffusion and reduces the oxygen that can be absorbed into the blood
Define parallel flow
the blood and water flow in the same direction at the gill lamellae, maintaining the concentration gradient to the point where blood and water concentration is equal.
Define counter-current flow
the blood and water flow in opposite directions at the gill lamellae maintaining the concentration gradient along their entire length
Why is counter-current flow more efficient?
bc diffusion is maintained along the entire length of the gill filament bc the conc of O2 in H2O is always higher than the blood so eqm is never reached.
What are the steps in the ventillation mechanism in bony fish? (water intake)
- mouth opens
- floor of buccal cavity lowers
- opercular valve closes
- volume increase so pressure decreases
What are the steps in the ventillation mechanism in bony fish? (water expulsion)
- mouth closes
- floor of buccal cavity rises
- opercular valve opens
- volume decreases so pressure increases
