Surface area to Volume ratio and Gas Exchange Unit 3.1 Flashcards
What are properties of single celled organisms? (3 points)
- Large surface area to volume ratio
- Substances like O2 can diffuse directly in and out of organism
- Size of cell is limited
Why do multicellular organisms need exchange organisms and transport systems? 3 points
Because diffusion across outer membrane is too slow because:
- Some cells deep within the body so there is a large diffusion distance
- Smaller SA:vol ratio so the rate of diffusion not fast enough to support needs
What is the trend in the size of an organism and the SA to volume ratio?
-The larger the organism the smaller the SA:volume ratio
How can surface area to volume ratio be increased? 2 points
- A flattened shape
- Specialised exchange surfaces with large areas
How do smaller animals maintain there body temperature?
- Due to larger SA:volume ratio smaller animals loose heat more easily
- High metabolic rate to maintain body temperature -eg mammals and birds
What are two body shape adaptations to increase or decrease heat exchange?
- Large ears - large SA to volume ratio more heat lost to surroundings - animal cools faster in hot climate
- Small ears - small SA to volume ratio less heat lost to surroundings- animal keeps heat in cold climate
What is a physiological adaptation to lower heat loss in animals?
-Hibernation - lowers metabolic rate and body temp, less heat loss
What are 2 behavioural adaptations to increase or decrease heat exchange?
-Huddling- eg in penguins- smaller sa to vol ratio- less heat loss
What are 5 features of specialised gas exchange surfaces?
- Large SA:VOL ratio
- Very thin
- Selectively permeable
- movement of environmental medium (maintain concentration gradient
- transport system
What is the equation for rate of diffusion?
rate of diffusion = surface area x concentration gradient / diffusion distance
How is SA:VOL ratio increased for mammals in gas exchange?
Many small alveoli which form branching bronchioles
many narrow capillaries
How is rate of diffusion maximised?
- Large SA:VOL ratio
- Short diffusion distance
- high concentration gradient
How is diffusion distance for gas exchange in mammals decreased?
Capillaries embedded in alveolus wall
Walls of alveoli and capillaries one squamous epithelial cell thick
How is concentration gradient in animals increases to maximise gas exchange?
-low concentration of oxygen in blood pumped from heart
-circular system removes O2 brings CO2
-ventilation system removes CO2 brings O2
high conc gradient
O2 and Co2 diffuse from high to low conc gradient
Explain the mechanism that causes forced expiration.
- internal intercostal muscles contract
- external intercostal muscles relax
- causes decrease in volume of chest
- air is forced down a pressure gradient
Explain gas exchange in insect’s.
- Respiration creates conc gradient
- Rhythmic abdominal movements allow air to diffuse in through spiracle
- Spiracles open and close -> oxygenated air can be stored in air sacks
- Air travels through many narrow branched tracheoles which penetrate muscles tissue and lie alongside cells
- CO2 diffuses out O2 diffuses in
How does insect’s movement increase gas exchange
- water in tracheoles
- Movement
- > anaerobic respiration produces lactic acid
- > lowers water potential in cells
- > water moves into cells by osmosis
- > increased tracheole surface area for diffusion
How is rate of diffusion maximised in insects?
- Many narrow branched tracheoles
- > increased SA:VOL ratio
- tracheoles penetrate muscle tissue and lie along side cells
- > decreased diffusion distance
- Respiration
- > increased conc grad
How do insect’s limit water loss?
Insects have a small Sa:Vol ratio which means they could loose water easily, to limit this they have:
- Impermeable cuticle made of chitin except on spiracles
- Spiracles can open and close to prevent water loss in hot climate
Explain Ventilation in fish
- Valve closes, mouth open, Buccal chamber expands
- > Pressure decrease
- > water flows in through mouth
- Mouth closes, Valve opens, Buccal chamber contract
- > Pressure increased
- > water forced over llamella gills and flows out through valve
How do fish increase SA:VOL ratio to maximize gas exchange?
- 4 pairs of gills
- Each have many filaments
- Each filament has many lamella
How have fish adapted a short diffusion distance to maximize gas exchange?
- Walls of lamallae and capillaries are one squamous epithelial cell thick
- Walls of capillaries and lamallae close together
Explain counter current flow
- Water and blood flow in opposite directions
- This creates a concentration gradient across the length of the Gill plate
- Oxygen moves from high concentration in water is lower concentration in blood
- Higher saturation of oxygen in blood than with parallel flow
Explain gas exchange in leaves of a plant
- Spongy mesophyll photosynthesise reducing conc CO2 and increasing conc O2 in air spaces in leaf
- Creates concentration gradient
- CO2 diffuses out O2 diffuses in to leaf
- Occurs at bottom of leaf(lower temp less water loss)
How do plants maximise gas exchange
- Flat shape
- > Increased SA:VOL ratio
- Many small stomata
- > Allow air movement in and out of leaf
- Air spaces in leaf
- > decrease diffusion distance between air and mesophyll
How do plants limit water loss
-Stomata open and close to balance has exchange and water loss
How do insects maintain a concentration gradient
-Rythmic abdominal movements to pump oxygen in/carbondioxide out
What is the difference between trachea and tracheae
Trachea found in animals, tracheae found in insects
How do we breathe in?
-Diaphragm muscle contracts and diaphragm flattens
-External intercostal muscles contract in ribcage pulled up
-Volume of thoracic cavity increase and pressure decreases to below atmospheric pressure
-Air moves into lungs down a pressure gradient
How do we breathe out?
-Diaghragm muscle rexales and moves up
-External inetcostal muscles relax and ribcage moves down
-Causes the volume of the thoricic cavity to decrease and the pressure to increase above atmospheric pressure
-Air moves out of lungs down a pressure gradient
