Adaptations for gas exchange in fish
- Created by: Emily Cartwright
- Created on: 27-05-14 18:32
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- Adaptations for gas exchange in fish
- Fish are more active than invertebrates so have a higher demand for oxygen
- Fish use water instead of air as their gas exchange medium
- However, water contains less oxygen than air and is more dense so the rate of diffusion in water is slower
- To meet their oxygen demand, fish have developed specialised gas exchange surfaces in the form of gills on gill lamellae
- To increase gas exchange efficiency, water is forces over the gills by pressure changes in the body which maintain a continuous, unidirectional flow
- Gills are made up of many folds to increase the surface area over which water can flow and gases can be exchanged
- The density of the water stops the gills from collapsing and lying on top of each other which would reduce surface area
- Gills are made up of many folds to increase the surface area over which water can flow and gases can be exchanged
- To increase gas exchange efficiency, water is forces over the gills by pressure changes in the body which maintain a continuous, unidirectional flow
- There are two types of fish, catagorised according to the material that makes up their skeleton;
- Cartilaginous Fish
- e.g. Sharks and Rays
- Skeleton made from cartilage
- Most live in the sea
- Just behind the head on each side they have 5 gill clefs which open at gill slits
- Water enters the mouth and is forced through the gill slits when the roof of the mouth is raised
- Blood flows through the gill capillaries in the same direction as the sea water (parallel flow)
- Water enters the mouth and is forced through the gill slits when the roof of the mouth is raised
- Parallel flow
- Only 50% of oxygen diffusion occurs
- Only half the length of the lamella is used for gas exchange
- Inefficient
- Blood - As distance across lamellae increases, so oxygen saturation increases up to about 50%
- Water - As distance across lamellae increases, so oxygen saturation decreases up to about 50%
- At 50%, equilibrium is reached, so maximum saturation is 50%
- Water - As distance across lamellae increases, so oxygen saturation decreases up to about 50%
- Blood - As distance across lamellae increases, so oxygen saturation increases up to about 50%
- Inefficient
- Only half the length of the lamella is used for gas exchange
- Only 50% of oxygen diffusion occurs
- Bony Fish
- Counter Current Flow
- Maximum concentration of oxygen in blood achieved
- Diffusion occurs across the entire length of the lamellae
- Equilibrium is never reached, concentration gradient is maintained
- Efficient
- Maximum saturation reached at 75%
- Blood - As distance across the lamellae increases so oxygen saturation increases
- Water - As distance across the lamellae increases, so oxygen saturation increases
- Blood - As distance across the lamellae increases so oxygen saturation increases
- Maximum saturation reached at 75%
- Efficient
- Equilibrium is never reached, concentration gradient is maintained
- Diffusion occurs across the entire length of the lamellae
- Maximum concentration of oxygen in blood achieved
- Skeleton made of bone
- Live in freshwater and the sea an exist in greater numbers than cartilaginous fish
- Gills covered with a flap called the operculum
- Bllod flows through the gill capillaries in the opposite direction to the water
- Adaptations for gas exchange
- Gills are found just behind the head in the pharynx
- There are four pairs of gills
- On each side of the fish, a flap covers and protects the gills
- Each gill is supported by a gill arch and along each gill arch are many pairs gill filaments and on these are the gas exchange surfaces - the lamellae
- The lamellae are formed by numerous thin folds lying on top of each other
- Each gill is supported by a gill arch and along each gill arch are many pairs gill filaments and on these are the gas exchange surfaces - the lamellae
- On each side of the fish, a flap covers and protects the gills
- There are four pairs of gills
- Out of the water, the gill collapses as the gill filaments lie on top of each other and stick together
- In water, the gill filaments are supported and the lamellae provide a large surface area
- The lamellae have lots of blood capillaries, these take up oxygen from the water and carbon dioxide passes out
- Fish blood also contains haemoglobin, which increases the efficiency of transportation in the bloo
- The lamellae have lots of blood capillaries, these take up oxygen from the water and carbon dioxide passes out
- In water, the gill filaments are supported and the lamellae provide a large surface area
- Gills are found just behind the head in the pharynx
- Ventilation Mechanism
- Fish ventilation is unidirectional because water is too dense to move in two directions
- Water is forced over the gill filaments by pressure differences which maintain a continuous, unidirectional flow
- The fish opens it's mouth. The muscles in the buccal cavity floor contract and the buccal cavity floor is lowered
- There is an increase in the volume of the buccal cavity and a decrease in the pressure. The pressure is lower than outside the body, so water flows in from an area of high pressure to low pressure
- Furthur pressure changes then force water from the buccal cavity over the gills and the deoxygenated water then flows out of the fish
- There is an increase in the volume of the buccal cavity and a decrease in the pressure. The pressure is lower than outside the body, so water flows in from an area of high pressure to low pressure
- The fish opens it's mouth. The muscles in the buccal cavity floor contract and the buccal cavity floor is lowered
- Water is forced over the gill filaments by pressure differences which maintain a continuous, unidirectional flow
- Fish ventilation is unidirectional because water is too dense to move in two directions
- Counter Current Flow
- Cartilaginous Fish
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