B7: Further Biology

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  • Created by: emmacram
  • Created on: 24-03-16 21:15

Vertebrates & Joint Movement

  • Vertebrates are animals that have an internal skeleton. Those that do not have an internal skeleton are called invertebrates. In vertebrate animals, the skeleton has two functions:
  • Support - the skeleton enables us to stand as well as enclosing important organs for protection, e.g. the brain is enclosed by the skull, and the ribs enclose and protect the heart and lungs.
  • Movement - the skeleton enables complex movement, from standing to sitting and from walking to running. Muscles are attached to various bones that enable arms and legs to act as levers to enable those movements. These movements could not happen in organisms without an internal skeleton.
  • Moving your arm requires more than just a single muscle. Muscles can only move bones by contracting. So, two muscles working in opposition to one another are needed to move an arm up and down, i.e. one muscle contracts while the other muscle relaxes, in other words, they work in antagonistic pairs.
  • For example to lift the lower arm, the biceps contracts and the triceps relaxes, vice versa.
  • If a tendon connecting the triceps to the bone was cut, the triceps would not be able to contract and the arm would remain in the up position.
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Structure/ Function of Joints

  • A joint is where two bones meet and work together. The bones have to be connected in some way that allows them to move while also staying in the same place relative to each other. This requires a number of different proteins to work together.
  • In a joint, such as the knee joint, there is a smooth layer of a stiff, inflexible protein called cartilage and a viscous fluid called synovial fluid. The purpose of cartilage and synovial fluid is to reduce friction and wear and tear between bones.
  • Ligaments are an elastic, fibrous tissue, made from collagen, which join bones together and stabilise them while still allowing movement.
  • Tendons are a tough fibrous tissue, made from collagen, which connect a muscle to a bone. Their purpose is to transmit the forces between the two. The force is only a pulling force.
  • Taken together, the specific properties of each part of a joint enable it to function correctly. If there is a problem with one part, the joint will not work correctly.
  • For example, if a tendon snapped then there would be no way of moving the bone. If knee cartilage was damaged then moving the leg would be a painful process, rather than a smooth one, due to the friction caused. For footballers, a torn knee ligament os a devastating injury that stops them playing for a season and can possibly end their career.
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Medical and Lifestyle History Assessment

  • When someone wishes to carry out an exercise regime, e.g. to train for a sport or to treat a condition such as obesity, it is important that the medical and lifestyle history of the person is examines beforehand. This helps to ensure that the exercise regime is effective and safe.
  • Practitioners who might develop an exercise regime include fitness instructors, doctors, nurses and physiotherapists, i.e. people who have had special scientific or medical training.
  • Important factors that a practitioner needs to consider when developing an exercise programme include the following:
  • Symptoms - visible or noticeable effects of a disease or condition on the body are usually noticed by the patient and can be used to identify problems.
  • Current medication - different medicines can sometimes conflict with each other and effect how the body responds under certain conditions, e.g. stress.
  • Alcohol consumption - high levels of alcohol consumed on a regular basis can cause physical problems. Body weight can increase to unhealthy levels and the kidney and liver can damage.
  • Tobacco consumption - there are many diseases and disorders directly related to smoking, such as lung cancer and bronchitis. Smokers have a higher risk of developing heart disease and high blood pressure. If a person exercises too much with these conditions, it could trigger heart failure.
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Developing an Exercise Regime

  • Level of physical activity - in general, the more exercise a person takes, the healthier they are. An individual who does little exercise is likely to get tired quicker, may have weak bones, and may have problems sleeping and concentrating. In such a case, an exercise regime would have to take account of the fact that the individual is not used to putting their body under physical stress.
  • Family medical history - some medical conditions can be genetic and therefore inherited. Genetic conditions such as heart disease need to be identified. If a family member is affected theen the person undertaking the exercise programme may also be.
  • Previous treatments - if a person is undertaking an exercise regime, it is useful to know what treatments they have had in the past. This can be a guide to designing the new regime, building on what previously worked and avoiding anything that did not.
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Body Mass Index

  • A person's height and mass can be used to determine their body mass index (BMI). The BMI is a guidline that helps to identify whether a person is a healthy mass. Formula for BMI is:
  • Body mass index = Body mass (kg) / [Height(m)] squared
  • The BMI does not take into account the proportion of body fat. So, along with the BMI, a physical test should be carried out to determine the amount of body fat. This can be done using callipers to measure the thickness of folded skin.
  • Fat is essential for the body. If the level of fat drops to below 6% in a man and 14% in a woman, then natural body processes that rely on fat are affected.
  • The amount of body fat required depends on what the person is doing. For example, a female athlete would need 14-20% and a male athlete 6-13%.
  • Generally, a person is regarded as obese if their body fat is more than 25% (in males) or more than 32% (in females), although age will alter this boundary.
  • An alternative to callipers is to use the conductivity of the skin to indicate the proportion of body fat.
  • If both the BMI and the body-fat proportion are high, the person needs to lose weight.
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Monitoring and Assessing Progress

  • A treatment of fitness-training regime needs to be monitored to check tht it is having the desired effect. It can then be modified depending on the patient's progress.
  • This is dependant on the accuracy of the monitoring techniques and the repeatability of the data. For example, measuring weight loss can be checked simply by standing on bathroom scales and checking the mass. However, our bodies lose and gain mass throughout the day, from eating, drinking and going to the toilet.
  • If a person checked their mass too often it would generate variable data that could not be relied upon. It would be better to measure body mass every few days and take the measurement at the same time of the day. This would make the data more reliable.
  • The human body can withstand a lot of exercise. However, excessive amounts (over-exertion or not properly prepared for exercise) can put the body under a lot of strain, which can lead to injuries. Injuries include sprain, dislocations and torn ligaments or tendons.
  • Dislocation - A sudden, severe impact can cause certain joints to become dislocated. A dislocation is where a joint becomes misaligned or the bones are disconnected from the joint. The unusual position of the bones is very painful and can also result in torn ligaments and tendons. Dislocated joints can often be mistaken for broken bones because they produce similar pain, misshapen body parts and severe swelling.
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  • A sprain is where an activity causes a stretch in a ligament beyond its natural capacity. Ankles, knees and wrists are all vulnerable to strains.
  • A sprained ankle can occur when the foot turns inward because this puts extreme tension on the ligaments of the outer ankle.
  • A sprained knee can be the result of a sudden twist. A wrist can be sprained by faling on an outstretched hand.
  • The symptoms of sprains are: swelling (due to fluid building up at the site of the sprain), pain (the joint hurts and may throb. The pain can increase if the injured area is pressed or moved in certain directions, or if weight is put on it) and redness and warmth (caused by the increased blood flow to the injured area).
  • When someone suffers a sprain the priority is to reduce swelling and pain, and aid rapid recovery and rehabilitation. The treatment follows the principle of RICE:
  • Rest - the patient rests and does not put pressure on the injured part of the body.
  • Ice - should be placed on the injured part for short periods to reduce swelling and bleeding (e.g. an ice pack, wrapped in fabric to prevent ice burns). // Compression - gentle pressure should be applied with a bandage to reduce the build-up of fluid that causes swelling.
  • Elevation- the injured part should be raised to reduce blood pressure and aid blood flow into the injured area.
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Torn Ligaments & Tendons & Physiotherapy

  • A particularly severe sprain could mean that ligament has been torn.Tendons can also be torn.
  • A torn ligament or tendon is very painful. Recovery can take a long time. The blood supply to ligaments and tendons is poor compared with other parts of the body, so the materials needed for repair (proteins, etc.) are slower to arrive.
  • A further consequence is that the bones connected to the ligament or tendon may not be in the correct position. If the tendon is torn, there is no way the limb can move - the muscle is effectively detached. Surgery may be required.
  • A physiotherapist specialises in the treatment of skeletal-muscular injuries. Physiotherapists understand how the body works and can help a patient to re-train or reuse a part of the body that is not functioning properly. This is normally achieved through various exercises to strengthen muscles that may have become weakened.
  • There are many different exercises and it is the job of the physiotherapist to choose the best course of treatment for each patient, e.g. an injured leg could be treating with this programme:
  • Warming up the joint by riding a stationary exercise bicycle, then straightening and raising leg.
  • Extending the leg while sitting (a weight may be worn on the ankle for this exercise).
  • Raising the leg while lying on the stomach. 
  • Exercising in a swimming pool.
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Circulatory System

  • Microscopic organisms do not need a circulatory system. Dissolved food and gases can diffuse through the cells easily. Once a certain size of organism is reached, diffusion is no longer effective. Cells that are out of reach of the gases and food cannot carry out respiration.
  • For larger organisms (e.g. an earthworm), a circulation system is needed. This involves a simple pump (a heart) forcing blood around the body. It ensures that all cells can get their dissolved nutrients and gases from the blood.
  • For the largest animals (e.g. mammals), a more efficient heart is needed as the organisms are larger still. The heart of these animals is effectively a double pump. Part of the heart pumps deoxygenated blood to the lungs to pick up oxygen and then returns the now oxygenated blood to the heart to be pumped around the rest of the body. This type of circulation is called double circulation.
  • The heart is a muscular organ in the circulatory system that beats automatically, pumping blood around the body. The rate at which the heart beats varies according to stress, exertion and disease.
  • Most of the heart is made of muscle. The left side of the heart is more muscular than the right side because it pumps blood around the whole body, whereas the right side only pumps to the lungs.
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Features of the Heart

  • Two atria, which are the smaller, less muscular upper chambers that receive blood coming back to the heart from the veins.
  • Two ventricles, which are the larger, more muscular lower chambers.
  • The vena cava is a larger vein that returns blood from the body into the right atrium.
  • The pulmonary arteries (one for each lung) transport blood to the lungs. Blood travels from the right ventricle to the lungs. The pulmonary arteries are the only arteries to carry deoxygenated blood.
  • The pulmonary vein returns blood from the lungs to the left atrium. It is the only vein that transports oxygenated blood.
  • The aorta is the largest artery in the body, taking oxygenated blood at high pressure to the whole body from the left ventricle.
  • There are arteries on the outside of the heart. The coronary arteries supply the heart with blood so that the heart cells can respire.
  • The pressures that build up inside the atria and ventricles are very high. Valves between each chamber and the arteries leaving the heart prevent the back flow of blood (which would stop the circulatory system from working).
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Heart and Blood

  • Valves are also found in veins in the rest of the body. Blood must only travel in one direction - if it moves back, it causes the valve to close (preventing further back flow).
  • If the valves in veins in the legs were to fail, varicose veins could form. This means that the blood does not move to where it should and it instead drops to the next working valve, causing inflammation and clots.
  • The blood transports glucose and oxygen to muscles and other cells. This is because all cells respire and need a supply of dissolved food and oxygen for this to take place. The blood then carries away from the cells waste products such as carbon dioxide (taking it back to the lungs so that it can leave the body).
  • Blood is a mixture of red blood cells, white blood cells, platelets and plasma.
  • Red blood cells transport oxygen from the lungs to the body. They have no nucleus which means they can be packed full of the red pigment haemoglobin, which binds to oxygen to form oxyhaemoglobin. Their bioconcave shape provides a larger surface through which oxygen can diffuse.
  • White blood cells have a nucleus and come in a variety of shapes. They defend the body against microorganisms; some white blood cells engulf and kill microorganisms while others produce antibodies to attack microorganisms.
  • Platelets are tiny particles found in blood plasma. They are not cells and do not have a nucleus. When a blood vessel is damaged, platelets are triggered to clump together to form a meshwork of fibres in order to form a clot and prevent blood leaving the body.
  • Plasma is a straw-coloured liquid that makes up around 55% of the total blood volume. It transports nutrients, antibodies, hormones and waste.
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Capillary Beds & Heat Stroke

  • Blood flows at high pressure from the heart in the artery. The blood reaches its destination via arterioles that branch off the artery and into capillary beds that surround cells.
  • The flow of blood through a capillary bed is very slow. The plasma leaves the blood and becomes tissue fluid. Tissue fluid enables the nutrients required by the cells (e.g. glucose for respiration, oxygen and hormones) to diffuse into the tissue cells.
  • The tissue fluid also collects and carries away some cellular waste products, such as carbon dioxide and urea. About 90% of the tissue fluid returns to the capillary bed, where it again becomes plasma. It leaves the capillary bed via venules and from there goes to the veins to continue its journey through the body.
  • Heat stroke is the result of an uncontrolled increase in body temperature, i.e. the body cannot lose heat fast enough. The core body temperature is 37 C. If it increases to 40 C this is life threatening. At 41 C the brain stops functioning properly, so it cannot trigger the effectors that would normally lead to heat loss. Common causes of heat stroke include exercising in very warm or humid conditions, and dehydration. Dehydration can be caused by increased sweating due to very hot temperatures and/ or excessive exercise. Dehydration stops sweating from taking place, which leads to the core body temperature increasing even further. If the body is not cooled down then death could rapidly occur.
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  • Homeostasis is the maintenance of a constant internal environment. It is achieved by balancing bodily inputs and outputs, while removing waste products. The body has automatic control systems, which ensure that the correct, steady levels of temperature and water are maintained. To maintain a constant body temperature, the heat gained by the body (including the heat that is released from respiration) has to be balanced with the heat that is lost.
  • Controlling body temperature requires temperature receptors in the skin to detect the external temperature, temperature receptors in the brain to measure the temperature of the blood, effectors (sweat glands and muscles), which carry out the response and the brain, which acts as a processing centre to receive information from the temperature receptors and to send signals to trigger the effectors.
  • The part of the brain that detects temperature changes in the blood, as well as processing and coordinating the response, is the hypothalamus.
  • If the temperature of the body is too high then heat needs to be transferred to the environment This is achieved through sweating, since evaporation from the skin releases more heat from the body. // If the temperature of the body is too low then the body starts to shiver. Shivering is the rapid contraction and relaxation of muscles. These contractions require energy from increased respiration and heat is released as a by-product, warming surrounding tissue.
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  • Vasodilation is the widening, and vasoconstricting is the narrowing, of the blood vessels (capillaries) that run very close to the surface of the skin.
  • In hot conditions, blood vessels in the skin dilate causing greater heat loss, i.e. more heat is lost from the surface of the skin by radiation.
  • In cold conditions, blood vessels in the skin constrict to reduce heat loss, i.e. less heat is lost from the surface of the skin by radiation.
  • The control of temperature is an example of effectors working antagonistically, which means a more sensitive, controlled response takes place.
  • Glucose is needed for respiration. When we eat foods containing carbohydrates, enzymes are needed to break them down into monomers. For example, the starch polymer is broken down into glucose monomers by the enzyme amylase.
  • Processed foods, as compared to fresh foods, are foods that have been changed from their naturally occuring state to make them healthier and/or for convenience.
  • Many processed foods have additives to improve shelf life, to make them more attractive and to make them taste better. Often sugar is added to the food in high levels in form of sucrose. Sucrose is a dimer of glucose and fructose monomers joined together. Sucrose is easily broken down in the small intestine into glucose and fructose. Fructose travels to the liver and is metabolised there, whiile glucose can then travel immediately in the blood. This causes an immediate increase in blood sugar level, which can cause problems for the body.
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Insulin and Diabetes

  • Insulin is a hormone produced by the pancreas. The presence of insulin causes cells to take in glucose from the blood. It effectively unblocks the cell so that glucose can enter; without the presence of insulin glucose cannot pass into the cell.
  • Inside the liver and muscle cells the glucose, if it is not immediately used in respiration, is converted into a storage carbohydrate called glycogen. Glycogen is a polymer made up of glucose monomers.
  • When glucose is absent, the body starts using fat as a source of energy instead.
  • The body alters the amount of insulin produced, depending on the amount of glucose in blood.
  • Diabetes is a condition that develops when glucose can no longe enter a cell to be used in respiration. This can be caused by a variety of reasons. There are two types of diabetes, which are caused in different ways.
  • Type 1 diabetes typically develops in young individuals up to the age of 40. It is where the insulin-producing cells in the pancreas are destroyed so the pancreas can't produce insulin. It is not known why this happens. However, it is sometimes triggered by a virus or other infection. I is treated by monitoring blood sugar levels and injecting insulin.
  • Type 2 diabetes is where the body does not produce enough insulin or the cells do not respond in the right way to insulin. As a result, the cells in the body are no 'unlocked' to allow the glucose in. Type 2 diabetes usually effects people over the age of 40, although it has been known to start as early as 25 in people from cultural backgrounds. There has been a large increase in people getting type 2 diabetes over the past few decades. This is believed to be due to a poor diet or obesity. Treating type 2 diabetes requires a controlled diet and exercise.
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Controlling Diabetes

  • Following a diet in which sugar is released slowly from food is a way of preventing or controlling type 2 diabetes. This is achieved by eating foods with a low glycemic index (GI).
  • The glycemix index is a measure of complexity of the carbohydrate inside the food. The more complex the carbohydrate, the lower the GI. If the carbohydrate is more complex then it will take longer to digest and break down into sugars, thereby preventing a sugar rush.
  • Low GI foods include wholemeal bread, fruit and yoghurt. Medium GI foods include basmati rice and table sugar. High GI foods include white bread, cornflakes and potatoes.
  • Eating foods high in fibre also helps to reduce blood sugar levels. Studies have shown that a high-fibre diet can reduce blood-sugar content by nearly 10%.
  • Exercise, along with a healthy diet (high in fibre and complex carbohydrates), helps to prevent cardiovascular disease and maintain a healthy body mass. When the body exercises, fat reserves are broken down and muscle is built up. This helps to keep the BMI in the correct range.
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Closed Loop Systems and 'Waste' Products

  • An ecosystem relies on inputs to ensure that growth can continue. If all of the inputs are met by most of the outputs from the ecosystem, then it is said to be a closed loop system.
  • This means that the waste from one part of the system is used by another part of the system. This is very efficient and means that, undisturbed, an ecosystem can remain that way for an indefinite period. A perfect closed loop system would mean that no waste was ever lost and the system could last indefinitely.
  • In reality, it is impossible to have a perfect closed loop system in an ecosystem. This is because organisms migrate out of the area and nutrients can be lost because they are transferred to another ecosystem by wind or water.
  • However, to be a stable ecosystem the outputs must be balanced by gains - a rainforest, such as the Amazon, is an example of this.
  • The 'waste' products in an ecosystem are oxygen (from photosynthesis), carbon dioxide (from respiration) and dead organic matter (fallen leaves, petals, fruit, faeces, etc.)
  • Although classed as being 'waste', it is only so for the organism that produced it. Other organisms may find the waste extremely useful, e.g. humans need oxygen (waste product of photosynthesis) and many drink alcohol (waste product from yeast).
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Using 'Waste' and Digestive Enzymes

  • The chemicals that make up 'waste' materials can be used either as a food or as reactants for different chemical reactions in the organism (i.e. plants, animals or microorganisms).
  • To break down food products, organisms often have to use digestive enzymes. Digestive enzymes break down large molecules into sizes that are small enough to break down large molecules into sizes that are small enough to pass through the intestine, so that they can be used to make new larger molecules.
  • If it were not for microorganisms, waste in the environment would build up to intolerable levels. Microorganisms use enzymes to break down the diferent food groups.
  • Proteins are broken down to amino acids by proteases.
  • Lipids (oils and fats) are broken down into fatty acids and glycerol by lipases.
  • Carbohydrates are broken down into sugars by carbohydrases (e.g. amylase).
  • As microorganisms can grow very rapidly, waste can be broken down very quickly.
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Reproduction in Animals

  • To reproduce successfully, organisms need to use a strategy that maximises the chances of the offspring reaching adulthood and reproducing themselves.
  • In most ecosystems there is competition between species. This means organisms have to invest energy and resources in achieving their goal of reproducing.
  • Females usually produce large numbers of eggs, while males produce large quantities of sperm. This ensures a high chance that at least one successful fertilisation will occur.
  • Growing offspring are a good source of food, so there is always a high chance that some of the offspring will be eaten by predators. Producing large numbers of offspring helps to mitigate against the loss.
  • With organisms such as frogs, the embryos develop together in a mass of frog spawn. This ensures that, even if some of the offspring are eaten, others will survive.
  • When the numbers of offspring are lower, the parents usually have to invest more time in staying with and protecting the offspring.
  • In mammals the offspring develop inside the body, so they are less likely to be eaten by predators. This means that the offspring are more likely to survive and therefore fewer are needed.
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Reproduction in Plants

  • Plants, which cannot move around, also have to employ strategies to ensure the success of the species. These strategies involve the following:
  • Flowers - to attract insects in sufficient numbers to ensure that reproduction occurs, large numbers of attractive-looking and nice-smelling flowers have to be produed. Not all flowers will be successfully fertilised.
  • Pollen - large quantities of pollen have to be produced. This is taken either by the wind (in wind-pollinated plants) or carried by insects (in insect-pollinated plants) to the destination plant. There is no guarantee that the pollen will land where it is supposed to.
  • Fruit - having been fertilised, the next stage in a flower's life cycle is to produce fruit. A fruit contains the seed and is grown to encourage animals to take the fruit and eat. Seeds, which are quite resilient, pass through the digestive system unharmed and are deposited in faeces. The faeces is a good source of nutrients (fertiliser), which will help the seed to grow. Not all seeds will be successful - they may be deposited in the wrong area, or chewed up and damaged. Therefore, large numbers of fruit needs to be produced to ensure that some of the seeds grow to adulthood, so that they can reproduce themselves.
  • It may seem wasteful producing large numbers of reproductive structures. However, in a stable ecosystem, the surplus reproductive structures that are unsuccessful are recycled.
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  • As well as contributing to the inputs and outputs of an ecosystem, organisms (particularly plants) have a big physical effect on the ecosystem itself. Plants have roots, which effectively bind the soil together. The larger the plant, the more extensive its root system. This means that the soil is bound together more effectively and is unlikely to be washed away.
  • The foliage of plants also reduces the effect of heavy rainfall washing away the surface soil. Most of the rainfall hits leaves, so water only gets to the surface gently and indirectly.
  • Vegetation can also alter the climate. It can prevent extremes of temperature by reducing the amount of carbon dioxide (a greenhouse gas) in the atmosphere. Rainforests transport a high quantity of water via transpiration. This means water is cycled from the ground to the air and this can stimulate cloud formation.
  • Humans benefit from and depend on ecosystems to provide a huge range of resources and processes. These are known as ecosystem services.
  • In 2004 the United Nations stated that humans are dependant upon ecosystem services and defined what a healthy ecosystem requires. These include providing clean air, water, soil, mineral nutrients, pollination and the presence of fish and game. If all of these are present, then the ecosystem is healthy.
  • Humans live in a linear system which has a take-make-dump model and not sustainable.
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Effects of Human Activity

  • Systems involving humans are not closed loop systems. Humans waste from households, agriculture and industry leaves the system as non-recycled waste, as well as though pollution from burning fossil fuels. This means the system is losing resources. Sometimes the waste can build up to harmful levels, which then affect other organisms.
  • Human activities can unbalance an ecosystem, changing the inputs and outputs so much that the ecosystem can no longer adapt. This means that the system is no longer a closed loop.
  • Houseolds produce waste which is an additional input to the ecosystem, changing its balance.
  • Industry produces large amounts of waste and pollution, which alter the environment. Carbon dioxide, although needed for photosynthesis, causes climate change through the process of enhanced global warming. Pollution by chemical waste can kill parts of food webs.
  • Fossil fuels are burned by homes, vehicles and industry, producing levels of carbon dioxide and other gases in much higher quantities than occur naturally.
  • In small enough quantities, the waste caused by human activity could be accommodated by the environment. However, with a growing population and industrial expansion, chemical waste has built up to harmful levels.
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Bioaccumulation / Removing Resources

  • Bioaccumulation is where a chemical that is deliberately or accidentally introduced into the environment starts to build up in concentration at each level in a food chain.
  • E.g. in Ontario, Canada, in 1970, mercury waste was released into nearby lakes from factories that were making batteries. Microorganisms in the sediment converted the mercury into a compound called methyl mercury. This then entered the food chain via phytoplankton. These were then eaten by small fish, which were eaten by other fish. As each organism ate a lot of the organisms in the previous trophic level, the concentration of methyl mercury increased. Eventually fishermen caught and sold the fish. Customers therefore consumed dangerously-high levels of methyl mercury. Consuming high levels of methyl mercury can cause speech problems, poor balance, heart attacks, blindness and birth defects.
  • When humans take away too many resources as biomass, then this reduces the amount available to be recycled within the ecosystem.
  • An example of this is over-fishing. Removing a few fish enables the ecosystem to adapt, but taking out too many disrupts the food chain and causes irreversible changes.
  • Biologists have carried out studies and have developed an explanation for what happens when humans take too many resources out of an ecosystem. This reduces the amount available to be recycled.
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Removing Vegetation and Eutrophication

  • Human activities have changed the landscape since the Stone Age. When the population was small, the environment was able to adapt. During the time of Henry VIII (1491-1547) mass deforestation occurred in England. Wood was removed to build the warships in his navy. As a result, the majority of England is no longer covered by forest.
  • An increasing population requires more food, so farming has replaced the natural vegetation with agricultural crops and livestock. The consequences of this land-use change include a loss of biodiversity (especially if the farming is a crop monoculture).
  • The removal of trees and shrubs to make way for livestock or crop plants can reduce the soil quality as it is more likely to be washed away by rain. Overgrazing by farm animals also removes the remaining plants and their roots, which bind the soil together.
  • When washed away, the soil ends up in nearby rivers and streams, silting them up and altering the flow of the water. If the farming is not managed properly, then ultimately what used to be forest can end up as desert which is called desertification.
  • The removal of natural resources is only sustainable if they are used at a rate at which they can be replaced. To try to ensure farming and fishing are sustainable, quotas and requirements for restocking or replanting are often imposed to allow ecosystems to recover from harvesting and to prevent over-fishing.
  • Eutrophication is where an excess of nutrients is put into a system, causing the productivity of the system to increase. This causes the balance of organisms to change, often drastically or irreversibly.
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Crude Oil

  • Crude oil is formed from the remains of plants and animals that died millions of years ago. The biomass is covered by silt and rock, and subjected to immense pressure and heat. Over millions of years, this causes the biomass to be converted into oil.
  • The Sun originally supplied the energy for the plants and animals to grow. In effect, all the energy that was stored in each plant and animal is now compressed in a much smaller space, in oil. When we burn oil, we are effectively using fossil sunlight energy.
  • Due to the immense length of time needed to create it, crude oil is regarded as being non-renewable and is not part of a closed loop system.
  • Sunlight is a sustainable source of energy - it will noy run out for another five billion years - and it allows sustainable agriculture and the growth of natural ecosystems.
  • Nowadays, when we understand more about how ecosystems work and how they can fail, we need to balance the need to conserve natural ecosystems with the needs of the human population. 
  • Creation of crude oil is as follows:
  • Marine animals and plants die and sink to the bottom of the seabed. // The plants and animal layer get covered with mud. //Over time, more sediment creates pressure, compressing the dead plants and animals into oil. // Oil moves up through porous rocks and forms a reservoir.
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Bacteria and Industrial Fermentation

  • Bacteria are ideally suited for industrial and genetic processes. This is due to rapid reproduction (bacteria can double in number every 20 minutes), the presence of plasmids (circular DNA molecules that can be transferred easily between bacteria), simple biochemistry (which makes the bacteria easier to understand and alter), their ability to make complex molecules (bacteria can produce molecules that can be used medicinally) and a lack of ethical concerns (when using bacteria, people do not regard them as the same as higher-order animals like rats and chimpanzees).
  • Bacteria and fungi can be grown on a small scale in test tubes. By maintaining the ideal conditions for a microorganism, it is possible to expand the process to an industrial (very large) scale using the process of fermentation and a fermenter.
  • A fermenter is a controlled environment that provides ideal conditions for microorganisms to live in, feed and produce the proteins needed.
  • A fermenter allows the continuous culture of large quantities of microorganisms or their products, namely: antibiotic and medicinal products - itt is possible to extract specific antibiotics and vaccines from bacteria and fungi grown in a fermenter, single-cell proteins/ hormones - insulin is a hormone that can be produced via bacteria in a fermenter, enzymes for commercial products and enzymes for food processing.
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Genetic Modification

  • DNA is the genetic material of all organisms and it contains the genes that code for the particular proteins an organism needs. Proteins produced by one organism may not necessarily be produced by another.
  • By carrying out genetic modification, the gene that produces a desirable protein can be inserted into another organism so that it also produces the required protein.
  • Once transferred into the target organism, the gene works and the target organism produces the new protein. The steps are as follows:
  • The target gene is selected and isolated. // The gene is now replicated.
  • The gene is inserted into the target bacterium by a vector. This could be a virus or a plasmid (double-stranded DNA molecule that replicates independantly of the bacterial chromosomal DNA). Viruses spread easily into cells. The virus incorporates the DNA with the target gene into the bacterium. The bacterium will now activate the gene and produce the protein. When using a plasmid, the plasmid is cut open and the gene inserted. The plasmids spread among the population of bacteria. Also, the plasmids are copied when the bacteria reproduce. This is the main way in which the plasmid increases in number.
  • The modified individuals are selected. It is usual to insert a gene for antibiotic resistance as well as the target gene. The specific antibiotic is applied to a plate of bacteria. Those bacteria with antibiotic resistance will also carry the desired gene and survive, while those that do not have antibiotic resistance will not have the desired gene and will therefore die. The surviving bacteria can then be harvested and grown in a fermenter.
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Using Genetic Modification & Genetic Testing

  • Genetic modification is now used to create an increasing number of drugs and hormones to treat patients. For example, genetically-modified microorganisms are used in the production of insulin for people who have diabetes. Millions of people suffer from this condition and require injections of insulin. Until recently, insulin was taken from pigs and cows. However, it is now possible to use genetically-modified bacteria to produce insulin. Genetic modification can also be used when growing crops. Farmers often have problems with weeds. By creating crops with resistance to a herbicide, the farmer can use that herbicide to kill weeds w/out destroying crop
  • The vast majority of DNA is identical in all humans. In fact, humans share 99.9% of their DNA with chimpanzees. Identifying specific individuals, rather than a species, requires a more specific technique - DNA profiling.
  • DNA profiling was invented by Sir Alec Jeffreys in 1985. It involves using specific areas of DNA that repeat regularly, called microsatellites.
  • Although variable, microsatellites are passed onto children. Everyone's microsatellites are different, a little like a fingerprint. This means that DNA profiling can be used to identify the paternity of a child or to identify the perpetrator of a crime.
  • DNA testing can also look for alleles of specific genetic disorders which enables people to find out the chance of getting a genetic disorder and take action in advance.
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Genetic Testing

  • Genetic testing involves extracting the DNA from cells. In forensic science, these can be from any type of cell. In a sample of blood, DNA can b extracted and isolated from white blood cells
  • Enzymes and detergents are used to release the DNA. Once the DNA has been washed and non-DNA material removed, it is subjected to a process called polymerase chain reaction(PCR) PCR is used to amplify the sections of the genome that are being investigated.PCR works by using the original DNA as a template and adding new copies using the enzyme,DNA polymerase, and primers (building blocks of DNA). PCR is a chain reaction because, once started, the DNA exponentially increases in quantity, so that in a short period of time there is plenty of identical DNA for the geneticists to work with.Gene probes (markers) are created that are mirror copies of the target allele or microsatellite region.The gene probes are attached to fluorescent chemical that emits ultraviolet light.If the target segment of DNA is present in the DNA sample, the gene probe will attach to it.
  • The samples are put into the wells of a polyacrylamide gel and an electric current is applied. The DNA fragments in the sample move down the gel at a rate determined by their charge and mass. This means that the genes separate out. This process is called Southern blotting. It is similar to the process of chromatography, which separates pigments. // Once separated, a special paper is placed on top of the gel. This absorbs the pattern of DNA. // If the labelled genes or alleles were present in the DNA sample they would produce ultraviolet light.
  • To identify the genes it is usual to run a set of test DNA sequences. This enables the geneticist to work out the relative sizes of the molecules in each band and to check they are what they should be by looking at relative position of the fluorescent band.
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  • Nanotechnology promises to revolutionise biology. It is the application of matter on an atomic scale. There are 1000000 nm in a mm.
  • Nanoparticles - these can deliver chemotherapy drugs directly to cancer cells.
  • Silver nanoparticles - silver has antimicrobial properties. It would be extremely expensive coating objects with silver. However, it is a lot cheaper using silver nanoparticles impregnated into different materials. Deodorants and bandages have been developed with silver added to them - the silver helps to kill microorganisms.
  • Tissue engineering - this is where scientists are looking to alter biological processes on an atomic scale.
  • Nanotechnology is being applied to the food industry. Wasted food is a big problem; it may end up in landfill. Food has to be sold with a use-by date telling the customer when it should be eaten. If the food is eaten after the given date it may have spoiled.
  • The use-by date is a scientific estimate, based on experiments. Samples of the food in question are placed on an agar plate. The plate is left and checked at intervals to see when the bacteria reach unsafe levels. However, as a precaution and because each batch of food varies, the use-by date is earlier than it could be.
  • Nanosensors are now being developed that can be incorporated into packaging. The sensors change colour when they detect the gases that are produced when food goes off.
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Nanotechnology/ Biomedical Engineering

  • Oxygen is a very reactive molecule that can cause rapid food deterioration. Manufacturers can prevent this by filling food bags with inert nitrogen gas. In addition, nanoparticles can be incorporated into packaging in order to prevent oxygen entering, improving the shelf life of the food product.
  • Nanoparticles have also been added to the plastic used to make fizzy drink bottles. This prevents carbon dioxide from leaking out, again improving the shelf life.
  • Methods such as those described above should help to reduce the amount of food that is thrown away.
  • Scientists and engineers are becoming more efficient at designing and creating replacement organs and body parts. This includes replacing faulty heart valves and designing pacemakers that keep the heart beating when the heart's own pacemaker (the sinoatrial node, a special tissue that causes the synchronisation of beating muscle) fails.
  • Replacement parts such as these have to be designed exceptionally well as they have to work perfectly on a daily basis.
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Stem Cell Technology

  • Stem cells are being used to reverse damage to the body.
  • Leukaemia - Stem cells can help to treat leukaemia, a disease that kills white blood cells. Blood cells are made from the body's own adult stem cells in the bone marrow. Traditionally, a leukaemia patient would need to have their own bone marrow removed and replaced with that from a tissue-matched donor. However, using stem cells  that have been harvested (and if necessary, genetically manipulated) from the patient's own body has a significant advantage. It means that the patient has a new complement of blood cells that are genetically the same as him/her. This reduces the need for a bone marrow transplant, which brings with it the risk of infection.
  • Spinal injuries - If a patient survives a broken spine, they will be paralysed from the break downwards. Spinal nerves do not re-grow, so this is a permanent and devastating injury. Stem cells are being investigated as they may allow the nerves to be reconnected and enable paralysed patients to move again.
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