Gas Exchange

Question 1

What do fish use for gas exchange?

Answer 1

Counter current system

Question 2

Explain the counter current system fish use for gas exchange

Answer 2

1. Water, containing oxygen, enters the fish’ mouth and passover the gills
2. Each gill is made of thin plates called gill filaments, which give a big SA
3. The gill filaments are covered in lamellae which increase SA even more
4. The lamellae have lots of blood capillaries and thin surface layer of cells to speed up diffusion
5. Blood flows through the lamellae in one direction and water flows in the opposite direction - this maintains a large conc gradient between the water and the blood. The conc of oxygen in the water is always high than in the blood, so as much oxygen diffuses into the blood as possible

Question 3

How do insects exchange gases?

Answer 3

Air filled pipes called tracheae

Question 4

How do insects use tracheae for gas exchange?

Answer 4

1. Air moves into the tracheae through pores on the surface called spiracles
2. Oxygen travels down the conc gradient towards the cells
3. The tracheae branch off into smaller tracheoles which have thin, permeable walls and diffuses directly into respiring cells
4. Carbon dioxide from cells moves down its own conc gradient towards the spiracles to be released

Question 5

How do insects move air in and out of the spiracles?

Answer 5

Rhythmic abdominal movements

Question 6

Where is the main gas exchange surface in a plant?

Answer 6

Surface of the mesophyll cells in the leaf

Question 7

How do plants exchange gases?

Answer 7

The mesophyll cells are inside the leaf. Gases move in and out through stomata in the epidermis. The stomata can open to allow gas exchange, and close to stop water loss. Guard cells control the opening and closing of stomata

Question 8

What do insects do if they’re losing too much water?

Answer 8

They close their spiracles using muscles. They have a waterproof, waxy cuticle all over their body and tiny hairs around their spiracles, both help reduce evapouration

Question 9

How do guard cells work?

Answer 9

Water enters the guard cells, making them turgid, which opens the stomata. If the plant gets dehydrated, the guard cells lose water and become flaccid, which closes the pore

Question 10

What are plants called that are adapted to warm, dry or windy habitats?

Answer 10

Xerophytes

Question 11

What are four xerophytic adaptations?

Answer 11

1. Stomata sunken in pits to trap moist air
2. A layer of hairs on the epidermis
3. Curled leaves with the stomata inside
4. Waxy, waterproof cuticles