BIOLOGY A - (3.3.1 - 3.3.4) ORGANIMS EXCHANGE SURFACES

SURFACE AREA TO VOLUME RATIO (3.3.1)

SURFACE AREA TO VOLUME RATIO (3.3.1)

Why can very small organisms simply change substances across their surface

Because there is a big exchange surface but also a smaller distance from the outside of the organism to the middle of it

Why do smaller mammals need a high metabolic rate

Due to their high surface area to volume ratio they will lose heat quickly therefore a higher metabolic rate provides the energy required to maintain stable conditions

Why can larger mammals have a slower metabolic rate

Because they have a lower surface area to volume ratio therefore they lose heat more slowly

What are some examples of adaptations to increase surface area to volume ratio

Villi and micro villi - Absorbtion of digested food

Alveoili and bronchioles - Gas exchange

Spiracles and tracheoles - Gas exchange

Gill filaments and lamellar - Gas exchange

GAS EXCHANGE (3.2.2)

GAS EXCHANGE (3.2.2)

What is the formula for calculating rate of diffusion using FICK’S law

Rate of diffusion = (surface area x difference in concentration) / length of diffusion path

What is ventilation (breathing) controlled by

The diaphragm and the antagonistic interaction between the external and internal intercostal muscles

What is pulmonary ventilation

Pulmonary ventilation is the total volume of air that is moved into the lungs during one minute (dm3 min-1)

What is the formula for pulmonary ventilation

Pulmonary ventilation = tidal volume x ventilation rate

Why are alveoli epithelial cells very thin and surrounded by capillaries

To minimise diffusion distance and maintain a concentration gradient

What is the special adaptation that fish have to breathe called

Countercurrent flow to maintain the concentration gradient to enable diffusion to occur

How many layers of gills are there on both side of the head in a fish

4

What are gills made up of

Stacks of Gill filmanets which are covered in lamellae positioned at right angled to the filament

What does this help to achieve

A higher surface area so that when fish open their mouth water rushes in and over the gills and then out through a hole in their head

How does countercurrent exchange work

Water flows over the gills in the opposite direction to the flow of blood in the capillaries

What does counter current flow ensure

That equilibrium is not reached and that the diffusion gradient is maintained across the entire length of the Gill lamellae

How do insects respire

hey have Spiracles which are little openings along the abdomen which lead to the trachea

What does the trachea branch off into

Tracheoles which help to deliver the oxygen to all respiring cells

Give 3 adaptations of tracheoles for efficient gas exchange

Thin walls for short diffusion distance

Highly branched for shorter diffusion distance

Highly branched to provide large surface area for gas exchange

What is the main method of gas exchange at rest in insects

Diffusion

What method of gas exchange Is used during periods of high activity

Mass transport can occur

How does mass transport occur

The abdominal muscles contract and relax which actively moves air in and out of the tracheal system, helping to maintain the gradient for oxygen and carbon dioxide

What product is made when the insect is very active and respires anaerobically

Lactate

What effect does the production of lactate have on respiration

Lactate lowers the water potential in muscle cells which causes water at the ends of the tracheoles to move into the muscle cells via osmosis

Why is less fluid and more air in the tracheoles beneficial for respiration

Gases diffuse more quickly through air than through liquid

What two adaptations do Spiracles have to limit water loss

They can open and close to reduce water loss

They have hairs on them to trap humid air and reduce the water potential gradient, reducing evaopration

Why do stomata close at night

To reduce water loss by evaporation

What are xerophytic plants

Plants adapted to survive in environments with limited water

Name two adaptations to the leaves of xerohytes that helps retain water

Curled leaves trap moisture which increases local humidity

Thicker cuticles to reduce evaporation