Where is the exchange system of oxygen in fish ?
Gills
The gills
How do gills have a large surface area ?
Gills
The gills consist of thin plates called gill filaments. These are also covered in lamellae.
How does lamellae speed up diffusion ?
Gills
- They increase the surface area
- They have lots of blood capillaries
- They have a thin surface layer of cells
How does the counter-current system in fish work ?
Gills
- water enters the fish through its mouth.
- The blood flows through the gills in the opposite direction to the water.
- This maintains a large concentration gradient down the whole length of the gill - there’s always a higher concentration of oxygen in the water than the blood so that it can diffuse down its gradient into the blood.
How does air enter an insect ?
Insects
Through pores on its surface called spiracles.
Explain how gas exchange works in insects
Insects
- Insects use rhythmic abdominal movements to move air into the spiracles by changing the pressure.
- Air enters the insect through pores called spiracles on the insect’s surface.
- The air enters tracheae (tubes with rings of chitin) and then these branch into tracheoles which are smaller tubes that are go into individual cells.
- The oxygen diffuses down its concentration gradient from the air in the tracheoles into the cells.
- Carbon dioxide then diffuses down its concentration gradient out of the cell and towards the spiracles.
How does air move in and out of spiracles
Insects
Insects use rhythmic abdominal movements to move air into and out of the spiracles by changing pressure
How are the tracheoles a good exchange surface ?
Insects
- They have thin permeable walls so the diffusion distance is short
- They are branched so there is a large surface area
- They enter tissues so short diffusion distance
How are tracheae strengthened ?
Insects
They have rings of chitin
How is gas exchange in insects a fast system ?
Insects
There’s no need for gases to bind to pigments like haemoglobin, also oxygen doesn’t need to travel in the blood stream to get to cells
Why can insects not be larger ?
Insects
Because gas is diffusing directly in and out of their body so bigger size would mean more cells and therefore a greater diffusion distance so gas exchange would not be efficient for the insect.
What can happen to tracheoles when the insect is resting ?
Insects
Tracheoles can fill with fluid to limit diffusion
What happens to active insects?
Insects
lactic acid concentration increases in the muscle cells, this draws water into the cells by osmosis
What adaptations do insects have to minimize water loss ?
Insects
- They have a small surface area to volume ratio
- A tough waxy, waterproof exoskeleton which stops them from drying out
- They have the ability to close spiracles using their muscles
- Spiracles have hairs to trap humid air.
- All of this reduces evaporation
Where is the main exchange surface in plants ?
Plants
the mesophyll cells as they have a large surface area and air gaps.
How do gases enter and exit a plant cell ?
Plants
gases move in and out of the cells through stomata, the stomata are opened and closed by guard cells.
What adaptations to plant cells have for gas exchange ?
Plants
- Many stomata in the lower epidermis open in the sun light to allow for gases to exchange in and out of the leaf.
- Thin cell walls minimize the diffusion distance.
- Close contact between cells and air spaces allow for efficient gas exchange for photosynthesis and respiration.
How do guard cells open and close the stomata to control water loss ?
Plants
- Stomata are usually kept open during the day for gas exchange. water enters the guard cells, making them turgid and open the stomata pores.
- If plants start to dehydrate the guard cells turn flaccid, closing the pore.
How are xerophytic plants adapted to their dry environment ?
Plants
- Stomata are sunk in pits and trap moist air, this reduces the concentration gradient of water between the leaf and the air. This reduces water loss by evaporation.
- A layer of hairs on the epidermis trap humid air around the stomata.
- Curled leaved with stomata inside, protect them from the wind and therefore evaporation
- A reduced number of stomata limit water loss
- waxy waterproof cuticle on leaf and stems reduce water loss by evaporation.
What happens during inspiration ?
Ventilation
- The diaphragm and external intercostal muscles contract causing the diaphragm to flatten and the ribcage to move upwards and outwards.
- This increases the volume of the the thoracic cavity resulting in lower pressure compared to the atmosphere.
- Air moves down this pressure gradient into the trachea and lungs.
Which ventilation process in humans requires energy ?
Ventilation
Inspiration
What happens during expiration ?
Ventilation
- The external intercostal muscles and diaphragm muscles relax causing the ribcage to move down and in and the diaphragm curves into a dome shape.
- This decreases the thoracic cavity volume causing pressure to increase higher than the atmospheric pressure.
- Air travels down this pressure gradient out of the lungs into the atmosphere.
What happens during forced expiration ?
Ventilation
- Internal intercostal muscles contract whilst the external intercostal muscles and diaphragm relax
- this causes the diaphragm to curve into a dome shape and the ribcage moves more downwards and inwards
- causing the thoracic cavity’s volume to greatly decrease
- meaning the pressure increases higher than the atmospheric pressure.
- More air moves down this pressure gradient out of the lungs and into the atmosphere.
How is the alveoli adapted for gas exchange ?
Ventilation
- They have/ create a large surface area so more gas can diffuse in and out at once for gas exchange.
- They have a thin exchange surface: The alveolar epithelium is only one cell thick so there’s a short diffusion path so gas exchange can occur quicker.
- Theres a good blood supply through the network of capillaries, this maintains a steep concentration/ diffusion gradient for gas exchange to occur quicker.
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Topic 1 - Biological molecules92
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Topic 1 - More Biological molecules49
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Topic 2 -Cell structure70
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Topic 2 -Cell Membranes38
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Topic 2 - The immune system43
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Topic 3 - Gas exchange33
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Topic 3 - Transport systems in Animals61
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Topic 3 - Transport Systems in Plants22
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Topic 4 - Genetic information31
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Topic 4 - Genetic variance and biodiversity63
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Topic 5 - Photosynthesis and Respiration40
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Topic 5 - Energy Transfer in Ecosystems38
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Topic 6 - Stimuli and Response52
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Topic 6 - Nervous Coordination51
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Topic 6 - Homeostasis35
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Topic 7 - Genetics22
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Topic 7 - Populations and Evolution41
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Topic 8 - Mutations and Gene Expression40
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Topic 8 - genome project and gene technologies47
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Statistics And Maths14
