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40 Cards in this Set
- Front
- Back
As the cell size increases what happens to the surface: volume ratio?
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It decreases - The diffusion pathway is longer and therefore diffusion would be slower. |
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What is gas exchange?
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The process by which oxygen reaches cells & carbon dioxide is removed from them.
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Talk about Unicellular Organisms (Amoeba)...
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- Small Size = Extremely large SA:V - Gas exchange across the whole body surface. - Permeable membrane allows diffusion of gases. - Aquatic organism = moist surface allows gases to dissolve and diffuse. - Specialised exchange organs not needed. |
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Talk about Simple Multicellular Organisms (Flatworm)...
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- Small size - Evolved a flattened shape to overcome the problem of increase in size. = Large SA:V, no cell is too far from the surface (short diffusion pathway) = no need for specialised pathway organs. - Permeable surface - Aquatic - moist surfaces allow gases to dissolve and diffuse. |
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Talk about Earthworms...
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- Multicellular organism - Terrestrial organism but has developed tube shape - Lives in damp conditions - Secretes mucus = surface is moist so gases can easily difuse - Elongated shape = large SA:V - Blood vessels close to the body surface so gases can easily diffuse in/out. - Blood circulates in vessels = maintains concentration gradient for diffusion of oxygen in/ carbon dioxide out. |
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Why do large multicellular organisms require a specialised gas exchange surface?
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1. As size of organism increases = decrease in SA:V. 2. Diffusion across body surface is insufficient to provide enough oxygen. 3. Larger organisms are more metabolically active = higher oxygen demand.# 4. Diffusion pathway is too large = slower. 5. So need a specialised exchange surface between organism & external environment. 6. Need method of transport to distribute gases around body. 7. Have toughened body surface so have internal gas exchange surfaces. |
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In order to achieve the max. rate of diffusion, all respiratory surfaces must be...
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1. Permeable 2. Moist 3. Thin 4. Large SA:V 5. Maintenance of a concentration gradient.
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What type of gas exchange surfaces to amphibians (frog) have?
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- Larvae/tadpole live in water = gills - Adults are terrestrial = skin- when inactive & skin & lungs- when active.
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Describe the structure of an amphibian lung?
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- Simple - Little infolding of the gas exchange tissues. |
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What is a benefit of having internal lungs?
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- Reduce heat loss. - Reduce water loss - Protection by ribcage or exoskeleton |
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Give 2 functions of the reptile ribs?
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1. Provide support & protection of organs 2. Enable ventilation of lung |
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How does the structure of the reptile lungs differ from that of amphibian lungs?
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Reptile lungs have more complex internal structure, w/ in-folded tissue to increase the surface area for more efficient gas exchange while amphibians' are more simple with little infolding.
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The respiratory system of birds...
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- More efficient that other vertebrates. - Ventilation is assisted by a system of air sacs connected to the lungs. - Air sacs act as bellows. - Fresh air passes through respiratory system in one direction = ensures no residual stale air is left in lungs. - First - fresh air to posterior sacs, into lungs, then anterior sacs, then exits through trachea. - Ventilation is brought by the movement of the ribs. - Contraction of flight muscles ventilates the lungs.
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Respiratory system for insects...
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- Do not use blood to transport gases. - Air diffuses into insects through holes called spiracles. - Spiracles lead to a system of branched chitin lined air tubes called tracheae. -Spiracles open & close. - During periods of activity, movements of the abdomen ventilate the tracheae. |
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Why is it important the spiracles can open & close like valves?
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- To allow exchange of gases. - To reduce water loss. |
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What structural feature ensures that the tracheae remain open?
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Chitin lines the tracheae keeping it open.
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Advantages of tracheal system:
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- No respiratory pigment needed = less energy need to produce it & move it. - Oxygen alone moves faster than oxygen in blood. - Reduces water loss - Oxygen is supplied directly to tissues.
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Problems caused by living in water?
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- Water contains less oxygen. - Rate of diffusion is slower in water. - Water is a dense medium so doesn't flow as freely . |
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Discuss Cartilaginous Fish... E.g. Sharks
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- Skeleton made entirely of cartilage - On each side of its head has 5 gill clefts which open @ gill slits. - Water is taken in & forced through gill when floor of the mouth is raised. - Use parallel flow.
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Explain parallel flow. |
- Gill capillaries on the same direction of the water. - Efficient at first b/c has a very steep concentration gradient. - But halfway along the gill lamellae equilibrium is reached & diffusion of oxygen & carbon dioxide is no longer possible. |
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Bony Fish E.G Salmon |
- Have an internal skeleton made of bone. - Gills are covered w/ a flap called the operculum. - Use counter current flow. |
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Explain Counter Current flow.
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- Water flows in opposite direction to blood flow. - Blood always meets water w/ a higher oxygen concentration. - Concentration gradient is maintained over the whole length of the gill lamellae. - Counter current flow is more efficient than parallel flow as it results in a higher blood saturation level.
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How many gills on each side does a head of a bony fish?
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4
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How does water pass through the gills in a fish?
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-Water is taken in through the mouth, passes over the gills & is expelled via the operculum. - Movements of the buccal cavity floor & operculum allow a one-way current of water to flow through the gills for the exchange of gases. |
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Ventilation Mechanism in Fish...
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Water flows in - Mouth - open - Operculum - Closes - Floor of Buccal Cavity - Lowers - Volume - Increases - Pressure - Decreases Water flows out = opposite. |
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The structure of gills of a bony fish...
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- Gill arch - thin filaments - gill lamellae. - Gill lamellae has large SA for gas exchange. - Blood circulates through capillaries in the gill plates. |
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What will happens if the gills were dry?
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- Shrink so smaller SA= less efficient - Not moist so hard for gases to diffuse easily. |
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What is the reason for 'C' shaped cartilage in the trachea?
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- Allows for expansion & stops it from collapsong
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What is the name of the airtight compartment of the body that encloses the lungs?
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Thorax.
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Explain how ventilation occurs in the human lungs.
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Inspiration - External Intercostal Muscles = Contract - Ribs = Out & Up - Diaphragm = contracts & flattens - Volume of the Thorax = Increases - Pressure in the Thorax = Decreases - Outside Air Pressure = Higher than in the lung Expiration = Opposite |
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Why are alveoli suitable for gas exchange?
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- Large number = large SA for diffusion of gases. - Moist - Gases dissolve easily - Permeable - Walls are 1 cell thick - short diffusion distance. - Each alveolus has an extensive capillary network - circulation of blood maintains the concentration gradient. |
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What is a surfactant and why is it important?
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- Chemical substance that covers surface of alveoli - Reduces surface tension & prevents the alveoli from sticking together & collapsing when breathing out. |
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What is the function of the plural membrane?
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Lubricates & causes cohesion in the lungs.
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What is the use of a respiratory pigment?
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To increase the oxygen carrying capacity of the blood (haemoglobin)
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How are leaves adapted for gas exchange?
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- Mesophyll layer is covered in water = moist - Flat leaf blade = large SA:V - Stomatal Pores = Permeable - Air spaces in space in spongy mesophyll rapid diffusion = short diffusion distance
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How is leaf adapted for photosynthesis?
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- Large SA:V to absorb as much light as possible. - Leaves can orientate themselves towards the sun. - Leaves are thin to allow light to penetrate lower layers. - Cuticle & epidermis are transparent to allow light to pass through to the mesophyll below. - Palisade cells are elongated and densely packed together & contain many chloroplast. - Chloroplast can rotate & more within the mesophyll cells to maximise light absorption. - Intercellular air spaces allow carbon dioxide to diffuse into cells, oxygen & water vapour to diffuse away.
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Info about the stomata...
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- Found in the wax cuticle on the underside of the leaf. - They allow carbon dioxide to enter & oxygen to leave. - 2 Guard cells surround each stomata. |
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What is unusual about guard cells?
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- They are only epidermal cells that contain chloroplast. - They have unevenly thickened cell walls. |
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What happens to the guard cells when the open & close?
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Open - Inner cell wall is thick & outer wall thin = turgid
Close - Guard cells become flaccid the pores close.
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The Mechanism for Stomatal Opening... |
- Potassium ions are actively transported from the epidermal cells into guard cells.
- Stored starch (insoluble) in guard cells is converted into malate (soluble) by enzymes in cytoplasm. - Water potential in GC is lowered so water enters by osmosis. - GC become turgid & curve apart b/c the outer cell walls are thinner than the inner cell walls. |