Gas Exchange (INSECTS + FISH+ PLANTS)

Question 1

Explain how a fish maintains efficient gas exchange

Answer 1

The blood in the capillaries flows in the opposite direction to the water flowing over the surface of the gill filament .
This maintains a steep diffusion concentration gradient across the WHOLE GILL FILAMENT so diffusion can occur

Question 2

What type of circulatory system do insects have

Answer 2

Open circulatory systems

Question 3

What system do insects use to perform gas exchange

Answer 3

Tracheal system

Question 4

Describe how the tracheal system works

Answer 4

1)Oxygen diffuses into insect through spiracles which insects can open and close
2)Oxygen moves into trachea and into smaller and smaller tracheoles.
3) Tracheoles allow oxygen to directly diffuse to the cells of the insect for areobuc respiration

–> aerobic respiration of cells maintains a concentration gradient for diffusion to occur (oxygen in, carbon dioxide out)

Question 5

What can more active or larger insects do to increase movement of gasses

Answer 5

Pump their abdomen

Question 6

Describe adaptations of insects that help reduce water loss

Answer 6

–> If insects are loosing so much water they can close their spiracles
–> They have a thick waxy cuticle
–> Have tiny hairs around spiracles to reduce evaporation

Question 7

Describe some adaptations of the tracheal system for efficient gas exchange

Answer 7

Tracheoles have thin walls so short diffusion distance to cells
Highly branched tracheoles so short diffusion distance to cells AND large surface area for gas exchange;
Tracheae provide tubes full of air so fast diffusion through into insect tissues;
Fluid in the end of the tracheoles moves out into tissues during exercise so faster diffusion through the air (than through liquid) to the gas exchange surface;
Body can be moved by muscles to pump air so maintains concentration gradient for oxygen / carbon dioxide (note that this pumping is only needed during vigorous activity)

Question 8

Give an example of xerophytic plants

Answer 8

Marram grass

Question 9

Give some adaptions of xerophytic plants that help them reduce water loss

Answer 9

Curled leafs: Curled leaf with stomata inside, protecting them from windy conditions which would have otherwise increased transpiration

Sunken stomata - sunk in pits to trap water vapour, reducing concentration gradient of water between leaf and air which reduces evaporation and transpiration

Thick waxy cuticle on leaves - reduces evaporation

Epidermal hairs - traps moist air which reduces water potential gradient and rate of transpiration

Lower epidermis - no stomata, reduced loss of water as there is less places water can escape from