Gas Exchange In Animals Flashcards
What does the amount of oxygen an organism needs depend on
Volume
The rate that oxygen is absorbed depends on
Surface area available for gas exchange.
The surface area to volume ratio of an organism effects:
-surface adapted for use for gas exchange
-the level of activity of the organism
What happens to an organism when they increase in size. Answer in terms of surface area to volume ratio
Surface area to volume ratio decreases so specialised respiratory surfaces are needed
Explain why insects cannot use their external surface for gas exchange
They are covered by an impermeable cuticle to reduce water loss by evaporation
Explain what spiricles are and where they are located
Pairs of spiricles are located on the segments of the thorax and abdomen. These are holes that lead to tubes called tracheae leading to tracheoles
Explain what tracheoles are and why they have fluid
Tracheoles enter muscle cells directly. They have fluid at the end for dissolving and diffusion of oxygen
Why, during flight, does the tracheoles have less fluid and what happens during flight
Shorten diffusion path and whole -body contractions ventilate the tracheal system by speeding up air flow through spiricles
Why do fish require a specialised gas exchange surface
- they have smaller surface area to volume ratio
- relatively active so have high metabolic rates making oxygen requirements high
-they require a ventilation mechanism to maintain concentration gradient for gas exchange
Why do fish require a ventilation mechanism
To push water (now dense with low O2) over high surface area gill filaments
What does removal of water do to gill filaments
Causes gill filaments to collapse, stick together and the gas exchange surface becomes to small for survival
Describe movement of water in ventilation of fish
- Mouth opens, floor of buccal cavity lowers so volume increases, pressure decreases so water flows in
- Mouth closes, floor of buccal cavity raises, increasing pressure pushing water over the gills
3.pressure in gill cavity increases and water forces operculum open and leaves through it
What are the gills made up off and what are they used for
Gill filaments made of gill plates/ lamellae - increase gas exchange surface across which the water flows
Gill Rackers -prevent large particulates entering and blocking the gills
Requirements for gas exchange surfaces
- be moist in terrestrial animals
-be thin (short diffusion pathway)
-have large surface area
-be permeable to gases
-have good blood supply to maintain concentration gradient (larger organism only)
Describe what type of gas exchange parallel flow
Where water and blood flow in same direction, equilibrium is reached and oxygen and diffusion reaches no net movement halfway across gill plate
Describe counter current flow in fish
If the water and blood flow in opposite directions across the gill plate, the concentration gradient is maintained and oxygen diffuses into the blood across the entire gill plate
How has an amoeba adapted to gas exchange
- single cell
-large surface area to volume ratio
-rate of oxygen through external surface meets demand. Oxygen demand is low - there is a short diffusion distance to the middle of the cell
How has a flatworm adapted to gas exchange
-multicellular
-smaller surface area to volume ratio
-flattened body to reduce diffusion distance so rate of oxygen diffusion through body surface meets demand
How has an earthworm adapted to gas exchange
-multicellular
- even bigger surface area to volume ratio
-body surface still used for gas exchange but circulatory system needed to distribute oxygen. Blood vessels are close to skin surface and blood has haemoglobin with a high affinity for oxygen
- mucus secreted to moisten surface and slow moving to reduce oxygen demand
Describe inspiration in humans
- External intercostal muscles contract and pull the rib cage up and out
- Outer pleural membrane is pulled out. This reduces pressure in the pleural cavity and the inner pleural membrane is pulled outwards
- This pulls on the surface of the lungs and causes an increase in volume of the alveoli
- Alveoli pressure decreases to below atmospheric pressure and air is dreams into the lungs
Describe expiration in humans
- External intercostal muscles relax and ribcage goes down and in
- Outer pleural membrane is pulled in increasing pressure in the pleural cavity and the inner pleural membrane is pulled downwards
- This causes a decrease in volume of the alveoli
- Alveoli pressure increases and air is drawn out of the lungs
What does amphibia contain for gas exchange
Soft, moist skin
When does gas exchange occur over the skin in amphibia
At rest
If not at rest how does an amphibia perform gas exchange
Oxygen and carbon dioxide circulate through a closed circulation system containing haemoglobin.
