Gas exchange in fish

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  • Created by: zoolouise
  • Created on: 02-05-16 14:57
What do gills have?
One-way current of water kept flowing by a ventilation mechanism. Many folds to increase the surface area for gas exchange. Large surface area as density of water prevents gills from collapsing on top of each other.
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What are the two main types of fish?
Cartilaginous fish which have a skeleton made of cartilage. e.g. sharks. Bony fish which have a skeleton made of bone. e.g. salmon
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What are some facts about cartilaginous fish?
They include sharks. They have gills in five spaces on each side and they're called gill pouches, these open at gill slits.
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Why is the ventilation mechanism for cartilaginous fish less efficient compared to bony fish?
No mechanism to force water over the gills, they must swim. Parallel flow so diffusion can only take place until 50% oxygen concentration is reached in the blood, equilibrium is reached so no more diffusion occurs.
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Why is the ventilation mechanism for cartilaginous fish less efficient compared to bony fish?
Gas exchange in parallel flow doesn't take place across the whole gill lamellae, it stops when the oxygen concentration in the blood and water area are equal.
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What are some facts of bony fish?
They have a skeleton made of bone. Gills are covered by a flap called the operculum and are protected. They don't open directly on the side of the fish as they do in cartilaginous fish. They live in freshwater and seawater.
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Why is ventilation needed?
To maintain a continuous, unidirectional flow.
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What happens in ventilation?
Water is forced over the gill filaments by pressure differences, pressure in the mouth cavity is higher than in the opercular cavity. Operculum acts as a valve and pump, lets water out and pumps water past gill filaments. Mouth also acts as a pump.
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How do fish take in water?
Mouth opens. Operculum closes. Floor of the mouth is lowered. Volume inside mouth cavity increases. Pressure inside mouth cavity decreases. Water flows in as external pressure is highr than pressure inside the mouth.
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How is water forced out over the gills?
Mouth closes. Operculum opens. Floor of the mouth is raised. Volume inside mouth cavity decreases. Pressure inside mouth cavity increases. Water flows out over gills as pressure in mouth cavity's higher than opercular cavity and outside.
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How many pairs of gills do bony fish have?
Bony fish have pour pairs of gills, each gill is supported by a gill arch.
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What are some features of gills in bony fish?
Along each girll arch there's thin projections, gill filaments on the gill filaments and gill lamellae. They're held apart by water flowing between them. They provide a large surface area. Gills stick together collapse out of water as no gas exchange
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What happens in counter-current flow?
Water moves from the mouth cavity to opercular cavity then into gill pouches, water flows between gill lamellae. Blood in gill capillaries flows in oppsite direction to water flowing over gill surface. This is why it's called counter-current flow.
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What does the water have in counter-current flow?
The water has a higher concentration than the blood, diffusion happens along the whole gill lamellae. 80% of the oxygen is removed from the water, high extraction of oxygen is important as water contains less oxygen than air.
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What do gills provide?
A specialised respiratory surface. Large surface extended by gill filaments and gill lamellae. Extensive network of blood capillaries, blood carrying haemoglobin allowing efficient diffusion of oxygen into blood and carbon dioxide out.
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Card 2

Front

What are the two main types of fish?

Back

Cartilaginous fish which have a skeleton made of cartilage. e.g. sharks. Bony fish which have a skeleton made of bone. e.g. salmon

Card 3

Front

What are some facts about cartilaginous fish?

Back

Preview of the front of card 3

Card 4

Front

Why is the ventilation mechanism for cartilaginous fish less efficient compared to bony fish?

Back

Preview of the front of card 4

Card 5

Front

Why is the ventilation mechanism for cartilaginous fish less efficient compared to bony fish?

Back

Preview of the front of card 5
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