Gas Exchange in Fish

Question 1

Properties of gas exchange

Answer 1

• Large surface area
• Thin (one layer of epithelial cells) - provide short diffusion pathway across gas exchange surface

Question 2

What does the organism do for gases across exchange surface?

Answer 2

Maintain concentration gradient

Question 3

How does single-celled organisms utilise diffusion?

Answer 3

Absorb and release gases by diffusion through their outer surface

Question 4

Why does single-celled organisms not need gas exchange?

Answer 4

• Large surface area
• Short diffusion pathway
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Question 5

Why do fish need adaptations?

Answer 5

Lower concentration of oxygen in water than air

Question 6

How does the water containing oxygen enter fish?

Answer 6

• By mouth and pass through the gills

Question 7

How is fish’s gills adapted?

Answer 7

• Made up of thin plates called gill filaments
• Gives big surface area for exchange of gases
• Covered in tiny structures called lamellae - increase SA more

Question 8

How is lamellae structurally adapted?

Answer 8

• Has lots of blood capillaries
• Thin surface layer of cells
• Speed up diffusion

Question 9

What is the counter-current system?

Answer 9

• Blood flows through the lamellae in one direction and water flows over in the opposite direction

Question 10

Why is the counter-current system useful?

Answer 10

• Maintains concentration gradient between water and blood
• Concentration of oxygen in water is always higher than that in the blood so diffuses as much oxygen as possible diffuses from the water into the blood

Question 11

Outline why countercurrent flow is an efficient means of exchanging gases across gills of fish.

Answer 11

A steady diffusion gradient is maintained over the whole length of gill lamellae

more oxygen diffuses from water into blood

Question 12

Mackeral are active, fast , swimming fish while plaice spend most of their lives moving slowly on the sea bed

There are differences in the gills of two types of fish

Suggest what this difference may be?

Answer 12

Mackerel have more gill filaments (large SA) compared to plaice

Question 13

Water flows over fish gills is one-way whereas the flow of air in and out of the lungs is two-way

Suggest the advantage to fish

Answer 13

Less energy is required because flow does not have to be reversed

Question 14

How does circulation of blood help?

Answer 14

Replaces blood that is saturated with 02

Question 15

How does ventilation of h20 help?

Answer 15

Replaces blood low in 02

Question 16

Describe and explain the counter-current system leads to efficient gas exchange across the gills of the fish:

Answer 16

Helps to maintain the concentration gradient between water and blood

Blood flows through lamellae in one direction and water flows over in opposite direction

Higher concentration of oxygen in water than blood , diffuses as much oxygen from water in blood

happens along the length of gill

Question 17

Amobeic gill disease (AGD) is caused by a parasite that lives on the gills of some species of fish. The disease causes the lamellae to be thicker and fuse together

AGD reduces the efficiency of gas exchange in fish. Give two reasons why:

Answer 17

Reduce the surface area of lamellae so it will be thicker

Longer diffusion pathway

Question 18

The volume of water passing over gills increases if temp of water increases

Suggest why:

Answer 18

Less oxygen dissolved in water

Increases volume of water passing through gills