active transport

  • Root hairs are specialised for absorbing water and mineral ions
  • They have a big surface area to absorb things 
  • concentration of mineral ions is higher in the soil that in the root hair cell so it uses active transport to take them in
  • Active transport allows the plant to absorb minerals against a concentration gradient but it requires energy from respiration and transport proteins
  • when theres a higher concentration of glucose in the gut they diffuse naturally into the blood but sometimes theres a lower concentration in the gut so active transport  allows nutrients to be taken into the blood
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Water flow through plants

Phloem tubes transport food:

  • made of columns of living cells with small holls at the end
  • they transprt food substances to growing regions and storage organs
  • transport goes in both directions

Xylem tubes take water up:

  • Made of dead cells joined end to end with a hold down the middle
  • carry water and minerals from the root to the stem and leaves in the transpiration system


  • The loss of water from a plant caused by evaporation and diffusion from the leaves
  • Lack of water in leaves means more water is drawn up from the roots through xylem.  This is the transpiration stream of water
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Circulatory systems - The heart

  • Humans have a double circulatory system
  • The first one takes in deoxygenated blood to the lungs to get oxygen then returns it to the heart.
  • The second one pumps oxygenated blood around all the organs. The blood gives up its oxygen to the body cells and the deoxygenated blood is pumped back to the heart to go back to the lungs again
  • The heart has valves to make sure blood always flows in the same direction
  • It has four chambers: right atrium, right ventricle, left atrium and left ventricle 
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Circulatory system - Blood vessels

  • Arteries carry blood away from the heart
  • Capillaries are involved in the exchange of materials at the tissues
  • Veins carry blood to the heart


  • heart pumps blood out at high pressure so artery walls are strong and elastic
  • walls are thick compared to lumen
  • contains thick layers of muscle and elastic fibres so they can spring back


  • arteries branch into capillaries
  • theyre really tiny
  • carry blood close to every cell to exchange substances with them
  • permeable walls so substances can diffuse in and out
  • supply food and oxygen. take away co2
  • walls are one cell thick, decreasing diffusion distance


  • capillaries join up to form veins
  • blood is at lower pressure in the veins so walls arent as thick
  • bigger lumen to help blood flow
  • contain valves to make blood flow in the right direction
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Circulatory system - The blood

Red blood cells

  • carry oxygen from lungs to all cells
  • concaved shape for larger surface area to absorb oxygen
  • no nucleus to carry more haemoglobin
  • in the lungs, haemoglobin combines with oxygen to make oxyhaemoglobin. In the tissues, oxyhaemoglobin splits to give oxygen to cells

white blood cells

  • change shape to engulf unwanted microorganisms
  • produce antibodies to fight microorganisms
  • produce antitoxins to neutralise toxins produced by microorganisms
  • they have a nucleus


  • small fragment of cells and have no nucleus
  • help blood to clot a wound, stopping blood pouring out and microorganisms getting in
  • lack of platelets cause excessive bleeding and bruising


  • pale straw coloured liquid which carries:
  • red and white blood cells and platelets
  • nutrients like glucose and amino acids
  • carbon dioxide
  • urea
  • hormones
  • antibodies and antitoxins
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Circulation aids - artificial blood

Artificial Blood

  • when someone loses blood, remaining blood can still be pumped round as long as the volume of their blood can be topped up
  • artificial blood is a blood substitute, a salt solution
  • it is safe as long as it has no air bubbles and can keep someone alive if they lose two thirds of their red blood cells and gives them time to make new blood cells. if not, they can have a blood transfusion
  • artificial blood products that replace function of red blood cells are being developed
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Circulation aids - heart


  • artificial hearts are mechanical devices put into a person to pump blood. 
  • in most cases they are a temporary fix until a donor heart is found. in some cases, it is a permanent fix
  • They're not rejectedby the immune system as they are made of metals and plastics which are not recognised by the body as foreign 
  • surgery to fit one can lead to bleeding and infection. they dont work as well as natural ones. parts could wear out or the motor could fail. blood doesnt flow through as smoothly which could lead to blood clots so patients have to take drugs to thin their blood which can cause problems with bleeding.
  • If just the heart valves are faulty, they can be replaced with mechanical valves
  • replacing a valve is easier than a whole heart transplant but is still a major surgery and there is still problems with blood clots. 
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Circulation aids - stents

  • coronary heart disease is when arteries get blocked by fatty deposits which causes arteries to become narrow so blood flow is restricted and can cause a heart attack
  • stents are tubes fitted inside arteries to keep them open making sure blood can pass through to heart muscles to keep the persons heart beating
  • stents lower risk of people with conorary heart disease getting a heart attack
  • over time the artery can narrow again as stents irritate the artery and make scar tissue grow.
  • patient has to take drugs to stop blood clotting on the stent
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Homeostasis is the maintenance of a constant internal environment 

  • body temperature cant get too hot or cold
  • water content mustn't get too high or low
  • ion content level
  • blood sugar level
  • amount of carbon dioxide 
  • amount of urea

thermoregulatory centre is in the brain and controls your temperature. contains receptors which are sensetive to temperature of blood in the brain and the skin

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homeostasis- thermoregulatory

too hot:

  • hairs lie flat
  • sweat is produced and then evaporates off the skin which removes heat
  • blood vessels supplying the skin dilate so blood flows closer to the surface of the skin. This makes it easier for heat to be transferred from the blood to the environment.

too cold:

  • hairs stand up to trap an insulating layer of air
  • no sweat is produced
  • blood vessels supplying skin capillaries constrict to close off skins blood supply
  • you shiver which requires respiration which releases some energy to warm the body
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Kidneys and homeostasis

Removal of urea:

  • proteins cant be stored by the body so excess amino acids are converted into fats and carbohydrates
  • this process occurs in the liver. urea is produced as a waste product from these reactions
  • urea is poisonous. released to bloodstream by liver. kidneys filter it out of blood. temporarily stored in bladder in urine

Ion content

  • ions such as sodium are taken into body as sodium
  • if ion content is wrong, balance between ions and water meaning too little/much water drawn in by osomosis which can damage cells
  • some ions are lost in sweat
  • balance is maintained by kidneys and removed in urine

Water content

  • water is removed in urine, in sweat and in the air we breathe out
  • we cant control water we breathe out but we do control liquids consumed, amount sweated out and amount secreted by kidneys in urine
  • on a cold day, if you dont sweat, youll produce more urine which will be dilute and pale
  • on a hot day, you sweat a lot, so youll produce less urine which will be dark and concentrated
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sports drinks

  • they contain water, sugar and ions
  • water and ions replace those lost in sweat
  • sugar replaces the sugar used up by muscles during exercise
  • sports drinks manufacturers claim their products with rehydrate you faster than water 
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Kidney function

Nephrons are the filtration units in kidneys


  • high pressure squeezes water, urea, ions and sugar out of blood and into the Bowman's capsule
  • membranes between blood vessels and Bowmans capsule act like filters
  • big molecules like protein and blood cells are not filtered through. they stay in the blood


  • Useful substances are reabsorbed back into the blood
  • sugar, sufficient ions and sufficient water are reabsorbed by active transport

Release of wastes

  • remaining substances continue out of the nephron, into the ureter and down to the bladder as urine
  • waste substances are urea, excess ions and excess water
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Kidney failure - dialysis

KKidneys remove waste substances from the blood

  • If kidneys dont work properly, waste substances build up in the blood and you cant control your ion or water levels
  • people can be kept alive with dialysis or a kidney transplant


  • done regularly to keep concentrations of dissolved substances at normal levels
  • persons blood flows alongside a selectively permeable barrier, surrounded by dialysis fluid. its permeable to things like ions and waste substances
  • dialysis fluid has same concentration of dissolved ions and glucose as healthy blood
  • only waste substances like urea, excess water and excessions diffuse across barrier
  • people have procedure 3 times a week for 3-$ hours each
  • may cause blood clots or infections
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Kidney failure - kidney transplant

  • kidney transplant is currently only cure for kidney failure
  • transplanted from people who have died suddenly(not by disease etc) or from an alive person as we have 2 kidneys
  • donor kidneys can be rejected by the bodys immune system as the foreign antigens of the kidney are attacked by the patients antibody
  • a donor with a closely matched tissue type has to be used 
  • patient is also treated with drugs that suppress the immune system
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controlling blood glucose

  • eating foods containing carbs put glucose in the blood from the gut
  • the normal metabolism removes glucose from the blood
  • vigorous excersise removes more glucose from the blood
  • levels of glusocse in the blood must be kept steady. changes in blood glucose are monitored and controlled by the pancreas using insulin and glucagon
  • insulin secreted by the pancreas makes the lover turn glucose to glycogen
  • glucagon secreted by pancreas makes liver turn glycogen into glucose
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Type 1 diabetes

  • pancreas produces little or no insulin
  • people must avoid foods rich in simple carbohydrates and exercise after eating
  • people inject insulin into blood at mealtimes
  • amount of insulin injected depends on persons diet and how active they are
  • insulin is made by genetic engineering
  • not as accurate as having a normal working pancreas so they still may have long term health problems
  • diabetics can have a pancreas transplant which means they wont have to inject insulin but the body can reject it and immunosuppressive drugs and expensive and often have serious side efects
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human impact on the environment

  • population is rising v quickly due to modern medicine and farmung which reduces people dying from disease and hunger
  • the huge population means we are using up the world resources for building supplies etc.
  • more people demand a higher standard of living with luxuries so more raw materials are being used ie. oil for plastics
  • more energy is being used for manufacturing
  • raw materials are being used quicker than their being replaced so we are running out fast
  • we are also producing more waste which produces harmful pollution when disposed
  • Water affected by sewage and toxic chemicals from industries which pollute lakes, etc. which also affect the plants and animals who rely on the water. also fertiliser is washed into water
  • Land affected by the use of toxic chemicals for farming. also we bury nuclear waste underground and dump on landfill sites
  • Air affected by smoke and gas released into atmosphere which pollutes the air (sulfur dioxide causing acid rain)
  • humans reduce amount of land and resources available to other animals and plants by buildings, farming, dumping waste and quarrying for metal ores.
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Carbon dioxide and the greenhouse effect

  • carbon is present in the air as carbon dioxide
  • many processed lead to co2 being released eie. burning of fossil fuels
  • too much co2 causes global warming
  • co2 in sequestered 'locked up' in natural stores; oceans, lakes and ponds, green plants stored as carbon compounds as plant remove co2 through photosynthesis and peat bogs

co2 and methane 

  • temp. of earth is a balance between heat it gets from sun and heat it radiates back into space
  • gases in atmosphere act like an insulating layer. They absorb most of the heat that would be radiated back out into space and redirect it back in all directions including Earth
  • This means that the Earth can stay warm at night
  • the gases that keep the heat in are called greenhouse gases and the amount of the 2 main ones, co2 and methane, is rising v quickly
  • This causes the Earth to heat up too much which is global warming. global warming is a climate change which causes other types of climate change like changing rainfall patterns
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  • deforestation is the cutting down of forests and is harmful when its done on a large scale
  • It is done for various reasons; to prvide timber for building materials, to clear land for farming for more crops for food ot biofuels and to produce paper from wood

Four main problems of deforestation

  • MORE METHANE IN THE ATMOSPHERE. rice is grown in warm, waterlogged conditons which produce methane. cattle produce methane 
  • MORE CARBON DIOXIDE IN THE ATMOSPHERE. from trees when they are burned to clear land. organisms feeding on dead release waste product of respiration
  • LESS CARBON DIOXIDE TAKEN IN. trees cut down so less co2 taken in for photosynthesis
  • LESS BIODIVERSITY. rainforests cut down which destorys habitats. this is a problem as there are probably useful products from animals/plants that havent been discovered yet and are being killed
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destruction of peat bogs

  • bogs are acidic and waterlogged areas. plants that live in bogs dont fully decay because there isnt enough destruction. the partly-rotted plants gradually build up to form peat.
  • carbon in the plants are stored in the peat
  • peat bogs are often drained so the area can be used for farmland or cut up to use as fuel. peat is also used as compost.
  • peat starts to decompose when drained so co2 is released
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climate change

  • sea gets warmer and expands so sea levels rise. low lying places like the maldives will be flooded
  • warm temperatures mean ice melts so water stored on land (ice) makes sea levels rise
  • regions suffer more extreme weather because of changes to weather patterns
  • distribution of animal and plant species may change. animals that need hot weather would have more places to go. animals that need cold weather wouldnt have as many places to go 
  • biodiversity could be reduced as they are unable to survive in the change of climate
  • changes in migration pattern

biodiversity- the variety of different species in a habitat

  • recording temperature using satellites
  • recording ocean currents
  • data is useful if it covers a wide are on a wide time scale
  • observations on a small area arent useful
  • observations over a short period of time arent useful
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biofuels - fermentation


  • fuels made by fermentation of natural products
  • fermentation is when yeast or bacteria break down sugars by anaerobic respiration
  • glucose -> ethanol +carbon dioxide + energy
  • sugar cane juices cane be used or the glucose from maize starch
  • ethanol is distilled to seperate it from yeast and remaining glucose
  • some countries used gasohol which is a mixture of ethanol and petrol
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biofuels - biogas


  • 70% methane and 30% carbon dioxide
  • different microorganisms are used to produce biogas. they ferment plant and animal waste which contains carbs. sludge waste from sewage etc. is used to make biogas on a large scale
  • Its made in a fermentor called a digester or a generator
  • fermentor needs to be kept at constant temperature to keep the microorganisms respiring and a constant pH so bacteria can function at an optimum level
  • biogas cant be stored as a liquid so has to be used straight away for heating, cooking, lighting or to power a turbine to generate electricity.
  • small biogas generatorsmake enough gas for a village or familt to use in cooking stoves, lighting and heating
  • human waste, waste from pids and food waste can be used
  • by-products are used to fertilise crops and gardens
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using biogas generators

Batch generators

  • make biogas in small batches
  • manually loaded up with waste which is left to digest and by-products cleared away after each session

continuous generators

  • make biogas all the time
  • waste continuously fed in and biogas produced at a steady rate
  • suited to large-scale biogas projects

biogas generators need to have:

  • an inlet for waste material
  • an outlet the digested material to be removed from
  • an outlet so that the biogas can be piped to where it is needed
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using biogas generators

factors to consider when designing a generator:

  • COST. continuous are more exensive because things are mechanically pumped in and out
  • CONVENIENCE. batch generators are less convenient as they have to be continually loaded, emptied and cleaned manually
  • EFFICIENCY: gas is produced most quickly at 35 degrees. generators need to be kept somewhere warm or need to be insulated
  • POSITION: waste will smell so keep away from homes. best located near the waste source

Economic and environmental factors

  • co2 released was taken in by plants which lived recently so theyre 'carbon neutral' 
  • doesnt produce lots of sulfur dioxide or nitrogen oxides
  • burning methane as a biogas means its not released into the atmosphere
  • raw materials are cheap and readily available
  • better fertiliser than undigested dung
  • biogas saves women in other countries having to collect wood for fuel
  • gets rid of animal and human waste that would otherwise lie around causing disease and polluting water supplies
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Managing food production

Efficiency of food production can be improved by:

  • reducing number of stages in the food chain (less energy used up)
  • restricting energy lost by farm animals (intensive farming) so animals kept close together in an indoor space so theyre not using up energy by moving around and keeping warm. 
  • developing new food sources like mycoprotein 


  • protein from fungi
  • used to make meat substitutes for vegetarians
  • fusarium is main source
  • grown in a fermentor using glucose syrup
  • oxygen is suppiled with nitrogen as ammonia and other minerals
  • fermentor is sterilised using steam so other microorganisms cant grow in it
  • efficient way to feed people
  • doesnt need a lot of space
  • good for developing countries that dont have a lot of meat 
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problems with food production and distribution

  • people think animals living in unnatural conditions is cruel. growing demand for organic meat 
  • crowded conditions for animals means diseases spread easily
  • to prevent disease, animals take antibiotics which would then get into humans when eaten. microbes in humans then develop immunity to these antibiotics so theyre less effective as medicines
  • animals need to be kept warm which often requires fossil fuels
  • fish is being fed to instensly farmed animals even when fish stocks are low

food being transported from a place far away is expenisive and bad for the enviroment(planes) 

  • overfishing is decreasing fish stocks
  • fishing quotas - limits on number and size of fish that can be caught in certain areas
  • net size - limits on mesh size depending on what fish is being caught. this reduces number of unwanted fish that have been accidentally caught. also, younger fish can slip through the net so they can reach breeding age
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