As Ocr Biology - Ventilation In Fish And Insects

Front 1

What is the name of the gas exchange systems in fish?

Back 1

A counter-current system.

Front 2

There is a ........ concentration of oxygen in ......... than in air. So fish have a special ......... to get enough of it.

Back 2

1. lower

2. water

3. adaptation

Front 3

Explain the counter-current system in fish. Give details on the structure of the system.

Back 3

• Water, containing oxygen, enters the fish through its mouth and passes out through the gills.
• Each gill is made of lots of thin branches called gill filaments or primary lamellae, which give a big surface area for exchange of gases.
• The gill filaments are covered in lots of tiny structures called gill plates or secondary lamellae, which increase the surface area even more.
• Each gill is supported by a gill arch.
• The gill plates have lots of blood capilaries and a thin surface layer of cells to speed up diffusion.
• Blood flows through the gill plates in one direction and water flows over in the opposite direction. This is called a counter-current system.
• It maintains a large concentration gradient between the water and the blood.
• The concentration of oxygen in the water is always higher than that in the blood, so the maximum amount of oxygen can diffuse into the blood from the water.

Front 4

How are fish gills ventilated in bony fish?

Back 4

• The fish opens its mouth, which lowers the floor of the buccal cavity (the space inside the mouth). The volume of the buccal cavity increases, decreasing the pressure inside the cavity. Water is then sucked in to the cavity.
• When the fish closes its mouth, the floor of the buccal cavity is raised again. The volume inside the cavity decreases, the pressure increases, and the water is forced out of the cavity across the gill filaments.
• Each gill is covered by a bony flap called the operculum (which protects the gill). The increase in pressure forces the operculum on each side of the head to open, allowing water to leave the gills.

Front 5

What do insects use to exchange gases?

Back 5

Tracheae.

Front 6

What are trachaea?

Back 6

Microscopic air-filled pipes which insects use for gas exchange.

Front 7

Air moves into the tracheae through pores on the insect's surface called ..........

Back 7

spiracles

Front 8

What direction does oxygen move in the concentration gradient (gas exchange in insects)?

Back 8

Oxygen moves down the concentration gradient towards the cells.

Front 9

What direction does carbon dioxide move in the concentration gradient?

Back 9

Carbon dioxide from the cells move down its own concentration gradient towards the spiracles to be released into the atmosphere.

Front 10

Explain how the tracheae branch off (inside the insect). What does this structure do?

Back 10

• The tracheae branch off into smaller tracheoles which have thin permeable walls and go to individual cells.
• The tracheoles also contain fluid, which oxygen dissolves in.
• Oxygen then diffuses from this fluid into the body cells.
• Carbon dioxide diffuses in the opposite direction.

Front 11

What do insects do to change the volume of their bodies to move air in and out? What do larger insects do when flying to move air in and out?

Back 11

• Rhythmic abdominal movements.
  
• Larger flying insects use wing movements to pump their thoraxes too.