Biology Unit 3 Revision

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Define osmosis
Osmosis is the movement of molecules from an area of high concentration to an area of low concentration through a semi permiable membrane
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An example of osmosis
Water molecules
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How do dissolved substances move?
Active transport and Diffusion
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How does water move across boundaries?
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When doing sport what needs to be replaced in cells?
Water and ions as they are lost during sweating. If not the cells don't work properly
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How is the effectiveness of an exchange surface increased?
Having a large surface area - Being think, to provide a short diffusion path - (in animals) having an efficient blood supply - (in animals for gaseous exchange) being ventilated
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In humans how is the surface area in the lungs increased?
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In humans how is the surface area in small intestine increased?
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How do the villi provide a larger surface area?
Have an extensive network of capillaries to absorb the products of digestion by diffusion and active transport. They have a single layer of surface cells and a very good blood supple to apply quick absorption
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How are the lungs separated by the upper and lower part of your body?
The lungs in the upper part of the body (thorax) protected by the ribcage and separated from the lower part of the body (abdomen) by the diaphragm
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Why does the breathing system take place?
So that oxygen from the air can diffuse into the bloodstream and carbon dioxide can diffuse out of the bloodstream into the air
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How does the air move into the lungs?
The ribcage moves up and out and the diaphragm becomes flatter -Intercostal muscles and diaphragm contract - thorax volume increase
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What is the breathing system called?
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How does air move into the lungs?
The intercostal muscles and diaphragm contract, so the thorax volume increases which decreases the pressure, drawing in air.
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How do we breath out?
The interoastal muscles and diaphragm relax, the thorax volume decreases which increases the pressure so air is forced out.
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How does the iron lung work/?
A giant case from the neck to the abdomen(head poking out). Air was pumped out of the case so that the pressure was dropped drawing air into the lungs. Air was pumped into the case so that the air in the lungs was forced out.
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The exhange systems in plants
Carbon dioxide enters leaves by diffusion and most of the water and mineral ions are absorbed by the roots
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How is the surface area of the roots increased?
Root Hair Cells
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How is the surface area of the leaves increased?
The flattened shape and internal air spaces
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What do plants have to obtain carbon dioxide from the atmosphere and to remove oxygen produced in photosynthesis?
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When is evaporation most rapid?
In hot, dry and windy conditions
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If plants lose water faster than it is replaced by the roots what to the stomata do?
Close to prevent wilting
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Where do plants mainly lose water vapour?
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What is the size of stomata controlled by?
Guard cells which surround them
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What does the circulatory system transport?
Substances around the body
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The heart is an organ and pumps blood around the body, What is the heart wall made of?
Muscle tissue
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What are the 4 main chambers in the heart called?
Left atria, Right atria, Left ventricle and Right ventricle
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Describe how the blood flows through the heart
Blood enters the atria of the heart. The atria contracts and forces blood into the ventricles. The ventricles contract and force the blood out of the heart. Valves in the heart ensure that blood flows in the correct direction. B
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How does blood flow to and from the heart?
From the heart to the organs through arteries and returns through the veins.
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Why are there 2 different circulation systems?
One for the lungs and one for all other organs of the body
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Describe an artery
Thick walls often containing muscle and elastic fibres
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Describe a vein
Thinner wall than an artery and often have valves to prevent back-flow of blood.
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What are used if arteries being to narrow and restrict blood flow?
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What are stents?
Tubes that are inserted inside arteries, making sure the blood can pass through to the heart muscle.
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Why are stents important for someone with coronary heart disease?
If an artery is blocked, stents lower the risk of a heart attack and keeps the heart beating
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What is a capillary?
Thin walled blood vessle - Involved in the exchange of material at the tissues
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Describe a capiliary
Arteries branch into them. They have permeable walls, so substances can diffuse in and out of them. They supply food and oxygen and take away waste like CO2
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What is blood?
A tissue and consists of a fluid called plasma in which red blood cells, white blood cells and platelets are suspended
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What does blood plasma transport?
Carbon dioxide from the organs to the lungs. Soluble products of digestion from the small intestine to other organs. Urea from the liver to the kidneys
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What do red blood cells transport?
Oxygen from the lungs to the organs
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Describe red blood cells and what they do/
Have no nucleus. They are packed with a red pigment called haemoglobin. In the lungs haemoglobin combines with oxygen to form oxyhaemoglobin. In other organs oxyhaemoglobin splits up into haemoglobin and oxygen
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Describe a white blood cell
Have a nucleus and form part of the body's defense system against microorganisms
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Describe a platelet?
Small fragments of cells and have no nucleus. They help blood to clot at the site of a wound
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What is an xylem tissue
Transports water and mineral ions from the roots to the stem and leaves. It's made of dead cells joined together
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What is an Phloem tube?
Carries dissolved sugars from the leaves to the rest of the plant, including the growing regions and storage organs. Made of living cells with small holes in the ends and transport goes in both direction.
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What is the transpiration system?
Caused by evaporation and diffusion. The movement of water from the roots through the xylem and out of the leaves
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What may happen if the water or ion content of the body is wrong?
Too much water may move into or out of the cells and damage them
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How does a healthy kidney produce urine?
First filtering the blood. Reabsorbing all the sugar. Reabsorbing the dissolved ions needed by the body. Reabsorbing as much water as the body needs. Releasing urea, excess ions and water as urine
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How are people treated if they suffer from kidney failure?
Having Kidney dialysis machine or by having a healthy kidney transplant
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What does treatment by dialysis do?
Restores the concentrations of dissolved substances in the blood to normal levels and has to be carried out by regular intervals
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What happens in a dialysis machine?
A person's blood flows between partially permeable membranes. The dialysis fluid contains the same concentration of useful substances as the blood. This ensure that glucose and useful mineral ions are not lost. Urea passes out from the blood
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What happens in a kidney transplant?
The diseased kidney is replaces with a healthy one from a donor. However the donor kidney may be rejected by the immune system unless precautions are taken
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Why would a kidney be rejected?
Antigens are proteins on the surface of cells. The recipient's antibodies may attack the antigens on the donor organ as they do not recognise them as part of the patients body
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How do you prevent rejection of the transplanted kidney?
A donor kidney with a 'tissue-type' similar to that of the recipient is used. The recipient is treated with drugs that suppress the immune system
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How is the body temperature monitored and controlled?
By the thermoregulatory centre in the brain. This centre has receptors sensitive to the temperature of the blood flowing through the brain.
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What happens if the core body temperature is too high?
Blood vessels supplying the skin capillaries dilate so that more blood flows through the capillaries and more heat is lost. Sweat glands release more sweat which cools the body as it evaporates
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What happens if the core body temperature is too low?
Blood vessels supplying the skin capillaries constrict to reduce the flow of blood through the capillaries. Muscles may 'shiver' (their contraction needs respiration) which releases some energy to warm the body
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What controls the blood glucose concentration?
Pancreas. This produces the hormone insulin, which allows the glucose to move from the blood into the cells
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What hormone (other than insulin) is produced by the pancreas when blood glucose levels fall?
Glucagon. This causes glycogen to be converted into glucose and be releases into the blood.
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Which type of diabetes is a disease in which a person's blood glucose concentration may rise to a high level because the pancreas does not produce enough of the hormone insulin/
Type 1
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What may waste pollute?
Water - with sewage, fertiliser or toxic chemicals. Air - with smoke and gases such as sulfur dioxide which contributes to acid rain. Land - with toxic chemicals such as pestisides and herbicides which may be washed from the land into waterways
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What has large-scale deforestation in tropical areas, for timber and to provide land for agriculture done?
Increased the release of CO2 into the atmosphere (because of burning and the activities of microorganisms). Reduced the rate at which CO2 is removed from the atmosphere and 'locked uo' for many years as wood
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Levels of carbon dioxide and methane in the atmosphere are increasing and contribute to 'global warming'. An increase in the Earth's temperature of only a few degrees Celsius may..?
Cause big changes in the Earth's climate, Cause a rise in sea level, Reduce biodiversity, Cause changes in migration patterns, Reult in changes in the distribution of species
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How may biofuels be produced?
Natural products by fermentation.
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How may biogas be produced?
Can be produced by anaerobic fermentation of a wide range of plant products or waste material containing carbohydrates
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Card 2


An example of osmosis


Water molecules

Card 3


How do dissolved substances move?


Preview of the front of card 3

Card 4


How does water move across boundaries?


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Card 5


When doing sport what needs to be replaced in cells?


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