3 Exchange Flashcards
What’s a xerophyte
Plants with a restricted supply of water, that have evolved a range of other adaptations to limit water loss through transpiration
Where does the most water loss occcur?
The leaves
Explain a thick cuticle
A waxy cuticle is waterproof but still allows up to 10% of water loss. The thicker the cuticle the less water that can escape
Eg. Holly leaf
Explain the rolling up of the leaves
Most leaves have their stomata confined to the lower epidermis- rolling protects this area by trapping air so it becomes saturated with water- increasing its water potential.
There’s no water potential gradient between the inside and outside of the leaf so there’s no water loss
Eg. Marram grass
Explain hairy leaves
A thick layer of hair on the lower epidermis traps still moist air on the leaf surface so the water potential gradient is reduced so less water is lost by evaporation
Eg. Heather plant
Explain stomata in pits and grooves
Trap still moist air to reduce water potential gradient so less water loss
Eg. Pine trees
Explain a reduced SA:vol
Slower rate of diffusion
Rate of water loss is reduced
Why must the volume of oxygen needed to be absorbed and the volume of carbon dioxide needed to be removed be large?
-humans are large with a large volume of living cells
-humans maintain a high body temp related to having a high metabolic and respiratory rates
Why are lungs inside the body
-air is not dense enough to support and protect the delicate structure
-the body would lose a lot of water and dry out
What is the trachea
Tube surrounded by rings of cartilage that prevent collapse when the air pressure inside falls when breathing in
What are the bronchi
Two divisions of the trachea
Similar to the trachea- produce mucus to trap dirt particles and have cilia that move dirt mucus to throat
What are the bronchioles
Walls made of muscles that allow them top constrict to control flow of air in and out of the alveoli
What’s between the alveoli
Collagen and elastic fibres so they can stretch to fill with air
What’s ventilation
The maintenance of the diffusion of gases across the alveolar epithelium
What happens in inspiration
Inhalation
What happems in expiration
Exhalation
What’s the diaphragm
Sheet of muscle that separates the thorax from the abdomen
DESCRIBE THE METHOD OF INHALATION
ACTIVE PROCESS
-external intercostal muscles contract, internal relax
-ribs are pulled upwards and outwards, increasing the thorax volume
-the diaphragm muscle contracts causing it to flatten which also increases the volume
-this results in a reduction of pressure
-air is forced in down the pressure gradient
DESCRIBE THE METHOD OF EXPIRATION
PASSIVE PROCESS
-internal intercostal muscles contract, external relax
-ribs are pulled downwards and inwards, decreasing the thorax volume
-the diaphragm muscle relaxes causing it to push up which also decreases the volume
-this results in a increase of pressure
-air is forced out down the pressure gradient
Describe the pathway taken by an oxygen molecule from an alveolus to the blood.
Diffuses from the alveolus across the alveolar epithelium, then across the endothelium into the blood.
What should you say instead of the alveolus has a “thin membrane”
The membrane is one cell thick
