6) Exchange Flashcards
Why do organisms need to exchange substances with their environment?
To supply cells with oxygen and nutrients and remove waste products like CO₂ and urea.
How does SA:V ratio affect exchange?
Smaller organisms have a higher SA:V ratio, making diffusion more efficient.
Why do large animals need specialised exchange surfaces?
Because their low SA:V ratio and higher metabolic rates require efficient exchange mechanisms.
How do single-celled organisms exchange substances?
By simple diffusion across the cell membrane due to short diffusion distances.
Why is diffusion not sufficient in multicellular organisms?
Because of low SA:V ratios and long diffusion distances.
What do multicellular organisms use for exchange?
Specialised exchange organs and mass transport systems.
What is mass transport in mammals?
The circulatory system transporting substances like oxygen, glucose, and waste.
How does body size affect heat exchange?
Smaller organisms lose heat faster due to a larger SA:V ratio.
What is the effect of shape on heat exchange?
Compact shapes minimise heat loss; elongated shapes increase it.
What behavioural adaptation helps hippos lose heat?
Spending time in water.
Why do small desert animals produce less urine?
To reduce water loss due to their high SA:V ratio.
Name 3 features of efficient gas exchange surfaces.
- Large surface area
- Short diffusion distance
- Good blood supply.
Why is movement of the environmental medium important?
To maintain a diffusion gradient, e.g. ventilation in lungs.
What structures make up the insect tracheal system?
Tracheae, tracheoles, and spiracles.
How does lactate production in insects aid gas exchange?
It draws water out of tracheoles, pulling in more air.
What is the counter-current flow in fish gills?
Blood flows opposite to water to maintain a diffusion gradient.
How do lamellae aid gas exchange in fish?
They increase surface area and reduce diffusion distance.
Where does gas exchange occur in plants?
In the mesophyll cells via stomata.
What controls the opening and closing of stomata?
Guard cells.
What adaptations reduce water loss in insects?
Waterproof cuticle, closing spiracles, and small SA:V ratio.
What are xerophytes?
Plants adapted to dry environments.
How do stomata in pits help xerophytes?
They trap moist air, reducing the water potential gradient.
Why do mammals have lungs?
To meet the high demand for oxygen due to large volume and metabolic rate.
What supports the trachea and bronchi?
Rings of cartilage.
What do alveoli do?
Facilitate gas exchange; they’re surrounded by capillaries.
What muscles are involved in breathing?
Diaphragm and intercostal muscles.
Describe what happens during inspiration.
Thorax volume increases → lung pressure drops → air enters.
Describe what happens during expiration.
Thorax volume decreases → lung pressure rises → air exits.
How do oxygen and CO₂ move across alveoli?
By diffusion down their concentration gradients.
Name two adaptations of alveoli.
Thin walls and large surface area.
How is pulmonary ventilation calculated?
Tidal Volume × Breathing Rate.
What is the typical tidal volume in adults at rest?
About 0.5 dm³.
