GCSE Core Biology Revision 1

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Note on GCSE Core Biology Revision 1, created by georgie.proctor on 04/06/2014.
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Note by georgie.proctor, updated more than 1 year ago
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DIET AND EXERCISE balanced diet- carbs, proteins, fats, vitamins, minerals, fibre and water carbs, fats and proteins release energy for respiration and growth vitamins and minerals needed fr your body to work healthily- without- deficiency diseases- have to eat the right type of food Unbalanced diet can lead to malnourishment How much energy you need depends on gender, age and the amount of exercise you do- also temperature you live in (affects how hard your body works to maintain constant body temp) Rate of chemical reactions in cell (metabolic rate) varies from person to person- men generally have a higher metabolic rate- exercise increases- as changes proportion of muscle to fat in the body- basic metabolic rate is inherited and genetic WEIGHT PROBLEMS obesity- take in more energy than use- excess is stored- need some fat to cushion internal organs and keep you warm- vital energy store- being overweight or obese is a form of malnourishment Obesity can lead to arthritis, type 2 diabetes, high blood pressure and heart disease- also lower life expectancy To lose mass- reduce energy intake and exercise more Benefits of exercise- increases amount of energy used up, increases proportion of muscle to fat, makes heart healthier Slimming programmes deficiency diseases result from a lack of mineral ions and vitamins INHERITANCE, EXERCISE AND HEALTH inherited factors affect your appearance,metabolic rate, proportion of muscle to fat and the levels of cholesterol in your blood CHOLESTEROL- needed for your cell membranes to make vital hormones- two forms of cholesterol- one healthy and one unhealthy- if balance is wrong your risk of getting heart disease increases- for most people, eating a balanced diet means the liver can keep the balance of cholesterol correct- eating high fat food leads to increased levels of harmful cholesterol, but inheritance can also affect levels as well regular exercise lowers your blood cholesterol levels and helps keep the balance, also means less overweight, more muscle tissue, faster metabolic rate, less likely to be affected by problems like arthritis, high blood pressure and type 2 diabetes.  PATHOGENS AND DISEASE An infectious disease is caused by a micro-organism entering and attacking your body. People can pass these micro organisms from one person to another so infectious Micro-organisms which cause disease are called pathogens. Common pathogens are bacteria and viruses BACTERIA= single- celled living organisms that are very small- some cause disease but some are useful (yoghur and cheese, treat sewage and medicine) VIRUSES- even smaller- cause disease in every type of living organisms Once pathogens are inside your body they reproduce rapidly, BACTERIA split in two then produce toxins which affect your body- VIRUSES take over the cells of your body as they reproduce, damaging and destroying cells (rarely  produce toxins) Common disease symptoms are a high temperature, headaches and rashes- caused both by the damage and toxins produced by the pathogens and the way the body responds to the damage and toxins.  Catch an infectious disease when you pick up a pathogen from someone else who is infected with the disease SEMMELWEIS recognised the importance of hand-washing  in preventing the spread of infectious diseases in hospital- hard to get his ideas accepted as no-one had ever seen bacteria or viruses and doctor's didnt like the idea that they were causing the death of patients DEFENCE MECHANISMS How pathogens spread: Droplet infection = coughing, sneezing or talking, expel tiny droplets full of pathogens from your breathing system- eg. common coughs and flu Direct contact = direct contact of skin- eg impetigo and some STD's like Herpes Contaminated food and drink = raw or undercooked food or contaminated water- eg diarrhoea and salmonellosis- large numbers of micro-organisms taken into your gut Through a break in your skin = cuts and scratches- eg HIV/ Aids or Hepatitis Skin covers your body and acts as a body Blood contains platelets that form a clot over a cut, which dries into a scab- scab forms a seal over the cut, stopping pathogens getting in through the wound. Breathing system produces mucus which covers the lining of your lungs and tubes. It traps pathogens then is moved out your body or swallowed down into the gut- acid in stomach then kills the micro-organisms- stomach acid destroys most of the pathogens you take in through your mouth.  WHITE BLOOD CELLS- immune system- ingest micro-organisms (take them in and destroy them), produce antibodies (special chemicals, need a specific antibody for each pathogen, once one type has been produced, can be made again very quickly if the pathogen gets into the body again), produce antitoxins- (counteract toxins released by pathogens) USING DRUGS TO TREAT DISEASE Painkillers like aspirin and paracetemol relieve symptoms but dont affect the pathogen- immune system does this Use antiseptics and disinfectants to kill pathogens outside the body- too strong and poisonous to use inside the body ANTIBIOTICS kill bacteria- damage the bacterial cells without harming body cells- no effect on viruses as viruses reproduce inside body cells FLEMING- discovered penicillin antibiotic GROWING AND INVESTIGATING BACTERIA culture (grow) bacteria so we can see a colony- can then investigate what nutrients they need and what chemicals are best at killing them use a liquid or gel containing nutrients- a culture medium- contains carbs and various minerals- agar jelly in a petri dish have to be careful as want to produce harmless pathogens- always the risk f mutation- also want to keep the pure strains of micro-organism free from contamination from outside micro-organisms- thus health and safety procedures: Petri dish and agar is sterilised (use heat to sterilise glass dishes)- special oven called an autoclave often used or UV or gamma radiation Then inoculate the sterile agar with the micro-organisms you want to grow (sterilise the inoculating loop with a Bunsen burner flame, allow to cool then dip in the suspension of bacteria and use it to make zigzag streaks across the surface of the agar. replace the lid on the dish quickly to avoid contamination. Seal lid with tape to prevent further contamination or micro-organisms inside escaping. Don't seal all around the edge so O2 can get in and harmful anaerobic bacteria won't grow. Sealed Petri dishes are then kept warm so micro-organisms can grow- 25 degrees in schools to reduce likelihood of harmful pathogens growing- higher in industry CHANGING PATHOGENS some bacteria develop resistance to antibiotics- they have a natural mutation (change in genetic material) which means they are not affected by the antibiotic. Happens by chance and produces new strains of bacteria by natural selection As resistance increases, diseases caused by bacteria are becoming more difficult to treat. Antibiotics have been overused which has increased the rate at which antibiotic-resistant strains have developed individual resistant bacteria survive and reproduce, so pop of resistant bacteria increases antibiotics no longer used to treat non-serious infections- hopefully slowing down the development of resistant strains- right type of antibiotic must be used and people must finish their course of medicine.  nb: antibiotics dont affect viruses MRSA- resistant strain of bacteria- contributes to many hospital deaths- to prevent:

dont overuse antibiotics use correct type of antibiotic wash hands- sterile disposable clothing for staff patients with MRSA should be isolated hospitals kept clean

the flu virus mutates easily so every year there are new strains of virus that your immune system doesnt recognise no effective treatment against viruses at all Epidemic (one country) and pandemic (across several countries) IMMUNITY every cell has unique proteins on its surface called antigens. Antigens on micro-organisms are different to the ones on your own cells- the immune system recognises this- wbc's then make antibodies and destroy the pathogens- your white blood cells remember the right antibody needed for a particular pathogen- if you meet the same pathogen again, they can make the same antibody very quickly- immunity so first time you meet a pathogen you feel ill, second time you dont (pathogens killed before you have time to) VACCINATION- protected against serious diseases by immunisation or vaccination- given a vaccine made of a deadened for of the disease causing micro-organism- triggers your body's natural immune response to invading pathogens- wbc's develop the right antibodies against the pathogen without you getting ill so, if you meet the live pathogens, can make the antibodies faster and you are not affected. Use vaccines against bacterial and viral infections- can wipe out diseases if a large population is immunized (smallpox) very small risk within vaccines- but outweigh the consequences of not having- some people have forgotten this now serious diseases are becoming less frequent whooping cough scare story- extreme consequences scientists constantly looking for new antibiotics due to antibiotic- restistant strain issue:

in crocs- crocodillin scientists collecting soil samples to try and find another mould fish covered in slime resistant to damage and infection Honey

KEEPING HEALTHY

 RESPONDING TO CHANGE Nervous system reacts to your surroundings and coordinates your behaviour carries electrical signals (impulses) to react to changes in your surroundings very quickly changes in the environment (stimuli) are picked up by cells caused by receptors Receptor cells are usually found clustered together in special sense organs, such as your eyes and your skin nb: ears sensitive to sound and changes in position for balance sensory receptor detect a stimulus, the information (sent as electrical impulses) passes along special cells caused neurons (found in bundles of hundreds or thousands and known as nerves). impulse travels along the neuron until it reaches the CNS (brain and the spinal chord).  cells which carry impulses from your sense organs to your central nervous system are called sensory neurons cells carry information from the CNS to the rest of your body = motor neurons- the effector organs respond effector organs are muscles or glands- muscles respond by contracting, glands respond by releasing (secreting) chemical substances all receptor cells have a nucleus, cytoplasm and cell membrane REFLEX ACTIONS automatic responses= reflexes- help avoid danger and also take care of basic body functions (breathing and moving food through your gut) electrical impulse passes from the sensory receptor along the sensory neuron to the CNS. Then passes along a relay neuron (in the spinal chord) and straight back along a motor neuron. From there the impulse arrives at the effector organ= REFLEX ARC bypasses conscious areas of the brain- shorter time nerves not joined directly to each other, junctions are called synapses- impulse arrives in neuron, there are sacs there containing chemicals, chemicals are released into the gap between neurons, chemicals attach to the receptor site of the next neuron and set up a new electrical impulse an impulse also travels up the spinal chord to the conscious area of your brain so you know about the reflex action, but only after it has happened.  HORMONES AND THE MENSTRUAL CYCLE glands make and secrete hormones- hormones regulate functions of many organs and cells- menstrual cycle is an example of this, hormones made in woman's pituitary gland and her ovaries control her menstrual cycle- levels of different hormones rise and fall in a regular pattern menstrual cycle is about 28 days- each month lining of the womb thickens and an egg starts maturing in the ovary, about 14 days after the egg is released (ovulation), lining of the womb stays thick for several days after the egg has been released if egg is fertilized- pregnancy. If not, the lining and dead egg are shed from the body (period), all these changes brought about by hormones- made and released by the pituitary gland in the brain and the ovaries surge of hormones from the pituitary gland starts eggs maturing in the ovaries- these hormones stimulate the ovaries to produce the female sex hormone oestrogen FSH is secreted by the pituitary gland- it makes eggs mature in the ovaries. FSH also stimulates the ovaries to produce oestrogen oestrogen is made and secreted by the ovaries- it stimulates the lining of the womb to build up and inhibits (slows down production of FSH) other hormones involved are LH and progesterone as oestrogen levels rise, they inhibit FSH and encourage the production of LH by the pituitary gland. When LH levels reach a peak in the middle of the cycle, they stimulate the release of a mature egg. 

ARTIFICIAL CONTROL OF FERTILITY the contraceptive pill contains female hormones, particularly oestrogen- they prevent the release of any eggs, inhibits production of FSH so no eggs mature in the ovaries- some modern pills contain only progesterone with less side effects. FSH AND LH are used in fertility treatments to stimulate eggs to mature (and in IVF) IVF- doctors collect eggs from the ovary and fertilise them with sperm outside the body, develop into tiny embryos then inserted back into the womb of the mother- bypass faulty fallopian tubes ADS OF FERTILITY TREATMENT- using the pill results in smaller families so less poverty, controls population growth, mature eggs produced in fertility treatments can be stored DISADS- pill can cause health problems, fertility drugs can have some health risks for the mother and are expensive for society and parents, tragic if process fails, costs hospitals money to keep small premature babies alive, ethical issues (preventing conception is denying life) CONTROLLING CONDITIONS conditions inside your body = internal environment many processes inside body to keep conditions constant = homeostasis- involves nervous systems, hormone systems and many of your body organs controlling water and ions- take in when you eat and drink, lose when you breathe out and sweat (lose salt in your sweat as well), lose water and salt in your urine, which is made in your kidneys- kidneys can change the amount lost- concentrationi controlled by nerves and hormones controlling temperature- must be kept at 37 degrees for enzymes. sweat and shiver controlling blood sugar- insulin made in the pancreas  Homeostasis is the result of the coordination of your nervous system, your hormones and your body organs

HORMONES AND THE CONTROL OF PLANT GROWTH plants sensitive to light, water and gravity plant roots are sensitive to gravity and water, the roots grow towards moisture and in the direction of the force of gravity plant shoots are sensitive to gravity and light- shoots grow towards light and against the force of gravity plant responses happen as a result of plant hormones- response of a plant to light is phototropism, to gravity it's gravitropism- controlled by a hormone called auxin- response happens because of an uneven distribution of this hormone in the growing shoot or root, unequal growth rate and root or shoot bends in the right direction Phototropism- more auxin on the side of the shoot that is unlit, more growth, bends, once light falls evenly the levels will be equal on all sides and shoot will grow straight roots and shoots respond differently to gravity as auxin has different effects- root grows more on the side with the least auxin- shoot grows more on the side with the most auxin We use plant hormones to manage plants grown in the garden. Farmers use them to grow better crops- plant growth hormones are used as rooting powder during cuttings process (stimulates growth of new roots and helps the cutting grow into a new plant)- can use high doses as weed killers (rapid, uncontrolled growth kills them as they have broad leaves so absorb more weed killer than grass (grass isnt affected))

USING HORMONES Some people object to older women having babies plant hormones are very useful as weed killers but their use can damage the environment

COORDINATION AND CONTROL

MEDICINE AND DRUGSDEVELOPING NEW MEDICINES testing and trials ensure safe process. A good medicine is effective, safe (side effects), stable (able to be stored) and successfully taken into and removed from the body stages of testing- cells, tissues and organs- animals (used to show and predict side effects), human volunteers in clinical trials- low doses at first for side effects then to see if it treats the disease- bigger clinical trials to find the optimum dose-- tested to establish, effectiveness, toxicity and the most appropriate dose double blind trials- patients either given the placebo or the new medicine- neither doctors nor patients know who has received what- often placebo contains a different drug that is already used to treat the disease so patient isn't deprived of treatment Thalidomide problem- a sleeping pill that didn't go through stages of testing with pregnant animals- not safe for developing fetuses and lead to severe limb deformities- this tragedy led to new standards for medicine testing- thalidomide can treat some huge diseases but must be used very carefully HOW EFFECTIVE ARE MEDICINES statins are drugs that lower the amount of cholesterol in your blood may be side effects, and some patients will assume they can then eat unhealthily non-prescribed medicines can be uneffective or dangerous. The effectiveness of both prescribed and non-prescribed drugs can only be measured in proper double-blind trials DRUGS a substance that alters the way in which your body works- often come from plants- some drugs used for medicine, others for pleasure coffee, tea and alcohol- legal, heroine, cocaine and ecstasy- illegal because drugs affect the chemistry of your body they can cause great harm- with medicine worth the risk, recreational no benefit- lots of harm addiction- become dependant on drugs- experience withdrawal symptoms without hard drugs, such as cocaine and heroine, are very addictive and can cause health problems- illness like hepatitis, STDs and HIV/ aids especially if drugs are taken intravenously (via a needle) LEGAL AND ILLEGAL DRUGS recreational drugs affect the way your nervous system works, particularly your brain, drugs like caffeine, nicotine and cocaine speed up the activity of your brain (make you feel more alert and energetic), alcohol and cannabis slow down the responses of your brain (calm). Heroin stops impulses travelling in your nervous system (no pain). Cannabis produces vivid waking dreams Choosing which drugs to make illegal does not appear to be based on the scientific evidence of health damage alone cannabis may be linked to hard drugs because cannabis is illegal and has to be obtained from a drug dealer. Cannabis smoke contains chemicals which may cause mental illness in some people. Teenagers are particularly vulnerable to this effect

DRUGS IN SPORT performance enhancing drugs allow athletes to improve on their natural ability anabolic steroids are drugs that help build up muscle mass strong painkilling drugs (athletes during injury) are illegal long distance runners use a drug to stimulate their body to make more red blood cells fast reactions drugs for this and for steady hands in darts- slow down heart athletes found using illegal drugs are banned from competing ETHICS- training at high altitudes makes a hormone which increases red blood cell count, this is legal, injecting that hormone is illegal arguments athletes may use are wanting to win, not wanting to be left behind, regarding the health risks as scare stories and claiming their coaches were supplying them secretly considered unethical by most people- unfair advantage

ADAPTATION FOR SURVIVALADAPT AND SURVIVE living organisms can survive and reproduce in many conditions- hot deserts, permanent ice and snow, deep, salt-water oceans and tiny, freshwater pools in order to survive plants need light, carbon dioxide, water (to maintain cells and tissues) , oxygen and nutrients to produce glucose energy in order to survive (for energy and growth) animals need food from other living organisms, water and oxygen microorganisms need a range of things, some are like plants, some are like animals and some don't need oxygen or light to survive living organisms have special features known as adaptations plants get water and nutrients from the soil through their roots. Epiphytes are found in rainforests, have adaptations which allow them to live high above the ground attached to other plants- collect water and nutrients from the air, for reproduction- smelly so increase the chance of insects visiting and carrying pollen Animals adapt to help them get the food they need- teeth- difference between herbivores and carnivores. Also have adaptations to help them find and attract a mate extremophiles have adaptations enabling them to live in extreme conditions of salt, temperature or pressure many extremophiles are micro-organisms- high temps- bacteria known as thermophiles which have specially adapted enzymes that don't denature and work at high temps (45-80)- vice versa with cold temps most living organisms struggle to survive in a very salty environment because of problems with water balance- some organisms have adaptations to their cytoplasm so water doesn't diffuse out their cells- would burst in ordinary water. ADAPTATION IN ANIMALS animals in cold climates- reduce energy loss, small surface area to volume ratio (larger)- ratio falls as object gets bigger, SA of thinly skinned areas of the body like the ears are small, insulation (blubber or a thick fur coat), fat layer also produces a food supply to live off in winter when there's almost no food camouflage- important for predators and prey- many Arctic animals have coats that change colour depending on season (Arctic fox and hare)- year round camouflage animals in dry climates- deserts- temperature and water supply are main problems- many desert animals are adapted to need little or nothing to drink- behaviour- often active in the early morning and late evening when it isn't so hot. quite small so large SA:V ratio, large thin ears to increase SA for energy loss- thin fur- little body fat ADAPTATION IN PLANTS small openings called stomata that allow gases in and out for photosynthesis and respiration- water vapour also lost through these.- in hot, dry conditions photosynthesis and respiration takes place very quickly and so plants also lose water vapour very quickly- need adaptations- reduced SA and store water in their tissues changing surface area- a few desert plants have broad leaves with a large SA to collect the dew that forms in the cold evening- then funnel the water towards their shallow roots, some have curled leaves- reduce SA and traps a layer of moist air around the leaf- reduces amount of water loss, most have leaves with a very small SA- reduced water loss- thick waxy cuticle covering- cacti- spines not leaves collecting water- extensive root systems- wide or deep storing water- stored in tissues

COMPETITION IN ANIMALS best adapted organisms are most likely to win the competition for resources- most likely to survive and produce healthy offspring. Animals compete for food, territory and mates food: herbivores- the animals that eat a wide range of plants are most likely to be successful- more food sources, carnivores- compete for prey, animals best adapted to the area will be most successful, carnivores often have to compete with their own species for prey as well- long legs and sharp eyes are successful features to pass on to offspring- prey animals also compete to be the one that isn't caught (bright warning colours or containing poisons so predators avoid them) territory: competing for the best spaces mates: often males fight, or display (male peacocks) many animals are successful because they avoid competition with other species as much as possible COMPETITION IN PLANTS compete for light (photosynthesis, energy), water (photosynthesis and support), nutrients (make chemicals), and space why plants try to spread there seedling so no competition small plants in woodlands grow and flower early in the year before trees regrow their leaves (bluebells), leaves shed the previous autumn by trees have rotted down to produce nutrients in the soil have different types of roots- wide or deep so can get what they need without affecting each other plants in the shade will grow taller and develop leaves with a bigger SA adapted against animals- thorns, poisons spreading the seeds- use the wind (winged seeds of the sycamore tree or dandelion parachutes), mini-explosions, animal poop (berries, fruits and nuts), fruits that are sticky get caught up in the fur of a passing animal plants that grow fastest will compete successfully HOW DO YOU SURVIVE?- CASE STUDIES Figs and fig wasps- each different species of fig tree has its own species of pollinating wasps, female fig wasps have specially shaped heads for getting into fig flowers, they also have ovipositors that allow them to place their eggs deep in the flowers of the fig tree, male fig wasps vary- have adaptations to find a female- if a fig tree cannot attract the right species of wasp it won't be able to reproduce star-nosed mole- fastest predator in the world- totally blind so extremely sensitive to touch and smell venus fly traps- special traps containing nectar- insects are attracted- inside the trap are sensitive hair which trigger the trap when touched- trapping the insect- nutrients from the insects replace the lack of nutrients found in the poor peaty bog soil MEASURING ENVIRONMENTAL CHANGE factors affecting distribution- average temp and rainfall, light, pH- in water- oxygen levels, some animals can only live in areas with high dissolved O2 and vice versa, living organisms also affect the distribution of living organisms- species depend on one another environmental changes- non-living factors like changes in temp, O2 conc, sunlight, wind or rainfall- living factors- a new type of predator, new disease-causing pathogen measuring- non-living indicators- scientific instruments- rain gauges, thermometers, oxygen meters and dataloggers- living indicators- particularly good indicators of pollution (lichen- sensitive to air pollution- more polluted the air- the fewer lichen species there will be)- invertebrate animals as water pollution indicators- counting diff types of species gives a good indication and can be used to monitor any changes THE IMPACT OF CHANGE temps in UK rising- big impacts and changes in distribution- changes in distribution of birds as climate changes honey bees- dying out due to disease called CCD- bees vitally important in plant ecology- pollinate flowers- disease is affecting, as well as changes in temp affecting flowering patterns and so the bees' food supply, farmers chemicals reproducible data on the effect of environmental change are not always easy to collect or interpret

ENERGY IN BIOMASSPYRAMIDS OF BIOMASS radiation from the sun is the source of energy for all living organisms on Earth biomass is the dry mass of living material in living organisms- all built up using energy from the sun- often measured as the dry mass of biological material in grams biomass made by plants is passed on through food chains or webs- goes into the animals that eat the plant (original source always the sun) number of organisms goes down as go through the food chain- however number of organisms often does not accurately reflect what is happening to the biomass amount of biomass at each stage is less than it was at the previous stage- show this using a pyramid of biomass pyramid of numbers often different to a pyramid of biomass why biomass decreases- not all organisms at one stage are eaten by the stage above, some material and energy taken in is passed out as waste by the organism, energy used in respiration and movement as well as growth A large amount of plant biomass supports a smaller amount of herbivore biomass supports a smaller amount of carnivore biomass ENERGY TRANSFERS energy is lost in waste- not all energy eaten can be used- herbivores can't digest all of the plant material they eat- material they can't digest is passed out of the body in faeces, carnivores- can't ear hooves, claws, bones or teeth- so biomass lost when an animal eats more protein than it needs, excess is broken down and passed out as urea in the urine energy is lost due to movement- biomass used for respiration and movement- muscle contraction (also get hot) energy lost keeping a constant body temperature- much energy transferred by heating to the surroundings- mammals and birds do this particularly DECAY PROCESSES nutrients passed on through food chains and webs are recycled. trres shed leaves and animals produce droppings, plants die. Decomposers then break down the waste, returning the nutrients back to the environment- creates a stable cycle. the decay process- decomposers include bacteria and fungi, detritus feeders (maggots and some types of worms) often start the process of decay. They eat dead animals and produce waste material. The bacteria and fungi then digest everything- dead animals, plants and detritus feeders plus their waste. They use some of the nutrients to grow and reproduce and release waste products. Waste products of decomposers are CO2, H2O and nutrients- decaying is breaking down by micro-organisms This recycling makes sure the soil contains mineral ions that plants need to grow- decomposers also 'clean up' the environment Conditions for decay- micro-organisms work best in warm conditions, decay stops if too cold or hot (enzymes denature), also grow better in moist conditions (easier to dissolve food and prevents drying out), also need a supply of oxygen for respiration  we take advantage of decay processes to help us recycle our waste- in sewage treatment plants use micro-organisms to break down bodily waste. Then safe to release into rivers and the sea- sewage works provide optimum conditions for the micro-organisms- in compost heaps decomposers produce compost which can be used as fertiliser In a stable community the processes that remove materials are balanced by the processes that return materials

THE CARBON CYCLE one of the most important cycled materials is carbon. - all the main molecules that make up our bodies are based on carbon atoms combined with other elements amount of carbon on the earth is fixed- some is locked up in fossil fuels and only released when burnt, some is in carbonate rocks like limestone and chalk, CO2 in the air, also found dissolved in rivers and oceans all the time a relatively small amount of available carbon is recycled between living things and the environment = carbon cycle green plants and algae remove CO2 from the atmosphere for photosynthesis- carbon passed on to animals that eat the plants living organisms then respire and produce CO2 as a waste product- returned to the atmosphere- when plants, algae and animals die their bodies are broken down by decomposers (detritus feeders)- these decomposers respire and release CO2- ready to be taken up again by plants and algae in photosynthesis combustion- fossil fuels contain carbon which was locked away by photosynthesising organisms millions of years ago. When we burn these CO2 is produced and released back into the atmosphere when plants and algae photosynthesize, they transfer light energy into chemical energy in the food they make for millions of years, the carbon cycle has regulated itself. However, as we burn more fossil fuels we are pouring increasing amounts of CO2 into the atmosphere. May lead to global warming RECYCLING ORGANIC WASTE need to recycle our organic waste organic waste put in landfill sites doesnt rot easily- micro-organisms produce methane gas, a greenhouse gas. The waste also produces a smelly liquid that soaks into the ground and can pollute rivers make compost- good, natural fertiliser and reduces amount of rubbish sent to landfill- can be done on a small and large scale- faster if mixed so there is an air supply (oxygen), warmer speeds up process as does moist conditions- compost heaps, compost bins, balck bag composting and council composting (variety of different ways)

Keeping healthy

coordination and control

medicine and drugs

adaptation for survival

energy in biomass

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