Biology (B7) Revision Notes

• All vertebrates have an internal skeleton which is needed for support and movement

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• At a joint, bones are held together by ligaments.
• Ligaments have a high tensile strength but are slightly elastic. This means they stabilise the joint, but ensure movement can still take place.

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• The end of a bone is covered with a smooth layer of cartilage
• This reduces the friction between the bones, and can act as a shock absorber
• Membranes release synovial fluid at joints to lubricate a joint, allowing movement by reducing friction.

• Tendons attach muscles to bones and muscles to other muscles.
• Muscles move bones at a joint through contraction.
• As tendons can't stretch, a muscle contraction leads to tendons pulling on the bone, transmitting the force from the muscle to the bone
• As muscles can only pull on bones (they can't push), muscles work in agnostic pairs. When one muscle contracts, the joint moves in one direction, when the other muscle contrasts, the joint moves in the opposite direction

• Fitness is a measure of how well you can do physical activity. Exercise increases fitness.
• When you're not exercising, your blood pressure and heart rate are at resting level. When you exercise, they increase. The time it takes for them to return to the resting level is your recovery period. If you are fitter, you have a shorter recovery period.

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Information is needed to start a exercise regime

• Health Problems. Symptoms of any previous issues that may affect your ability to exercise
• Current Medication. Some medication may affect your ability to exercise
• Previous fitness treatments. What has worked and what hasn't worked in the past
• Lifestyle Factors. Smoking and heavy drinking may affect your ability to exercise
• Family History. Illnesses can run in families, this could be important when designing a regime
• Current physical activity. So the regime will be challenging but won't  injure you

• BMI is a measure of fitness which uses mass and height

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• BMI isn't always accurate as muscle is more dense that fat. If you are fit and muscular, you may be classed outside the 'normal range'.

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• Accuracy.  Depends on the equipment used
• Reliability. If the experiment was repeated, you'd get the same result

Injuries can come about as a result of excessive exercise

• Sprains. Damage to a ligament, which is usually caused by too much stretching. Causes damage and pain
• Dislocations. When a bone comes out of its socket, due to a heavy fall. Causes severe pain
• Torn ligaments. When the ligament tears, causing more severe pain than a sprain. Can lead to loss of control of the joint, as the bones are no longer firmly attached together
• Torn tendons. When a tendon tears, caused by a muscle contracting in one direction, but it's being pulled in the opposite direction. Causes pain.

RICE

The main symptons of a sprain are swelling and pain, so the treatment helps reduce this

• Rest. To avoid further damage
• Ice. To reduce swelling by reducing the temperature and blood flow to the injured area.
• Compression. Placing a bandage around the injured area to reduce swelling and prevent further damage from excess movement. Not too tight, or will cut off blood flow
• Elevation. Raising an injured limb as high as possible. Makes it easier for blood to flow back to the heart and so reduces swelling.

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Physiotherapists treat skeletal-muscular injuries

• Physiotherapists treat more serious injuries
• They may give treatment (to reduce pain and swelling) and therapy (such as laser treatment) to speed up healing
• They can give advice on the best exercises for rehabilitation after an injury
• These may be graded exercises, which steadily rebuild the strength of a muscle or joint

• Blood transports various substances around the body through the circulatory system.
• It carries oxygen and glucose to the muscles and takes carbon dioxide (a waste product) away from them

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• Red blood Cells. They transport oxygen from the lungs to the rest of the body. They don't have a nucleus, so they can be packed with haemoglobin, which binds to oxygen. They have a biconclave, which gives them a larger surface area to bind with oxygen.
• Plasma. The liquid that transports nutrients (glucose and amino acids) and waste (urea and carbon dioxide)
• White blood cells. To fight infection
• Platelets. Small cell fragments that help blood to clot at a wound site

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•  Humans have a double circulatory system - which means its two circuits joined together
• The first one pumps deoxygenated blood to the lungs, the second pumps newly oxygenated blood around the body 

How blood is pumped through the heart

• Blood enters the right atrium through the vena cava
• The right atrium fills with blood and contracts, pumping it through valves (which prevent backflow of blood) to the right ventricle
• The right ventricle fills with blood and contracts, pumping it through the pulmonary artery to the lungs, where it becomes oxygenated
• The newly oxygenated blood enters the left atrium through the pulmonary vein
• The left atrium fills with blood and contracts, pumping it through valves to the left ventricle
• The left ventricle fills with blood and contracts, pumping it through the aorta to the rest of the body
• The left ventricle has a thicker wall than the other chambers as it has to pump the blood a further distance

• Arteries branch into capillaries, small blood vessels
• These capillaries have permeable walls, which allow substances to diffuse in and out
• A network of capilaries in a tissue is called a capillary bed
• As blood passes through a capilary bed, small molecules (like oxygen, glucose and water) are forced out of the capillaries, forming a tissue fluid which surrounds the cells.
• These substances can then diffuse out of the tissue fluid into the cells
• Water chemicals (like carbon dioxide and urea) diffuse out of the cells into the tissue fluid, and back into the capillaries
• The tissue fluid allows cells to get the substances they require with each capillary supplying every single cell.

• The body has to balance the amount of heat lost and heat gained in order to keep the core body temperature constant
• Temperature receptors in the skin detect a change in the external body temperature and temperature receptors in the hypothalamus detects temperature change in the blood
• Some effectors work antagonistally, so as one effector heats, the other cools. This brings about a very precise temperature, allowing a more sensitive response

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• The receptors (in the skin and in the hypothalamus) detect the core body temperature is too high
• The hypothalamus acts as a processing centre, receiving the information from the receptors and triggering effectors, which produce a response to conteract the change

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• The receptors (in the skin and in the hypothalamus) detect the core body temperature is too low
• The hypothalamus acts as a processing centre, receiving the information from the receptors and triggering the effectors, which produce a response to conteract the change

When you're too hot

• Vasodilation. The blood vessels which are close to the surface of your skin get bigger in diameter (dilate). The warm blood is closer to the surface of the skin and so loses more of its heat to the surroundings
• Sweat. Sweat glands produce more sweat.When the water in sweat exaporates, it cools the body. Excercising can lead to excess sweating. This results in water loss, which could lead to dehydration. If you're dehydrated, you sweat less, which means your core body temperature increases

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When you're too cold

• Vasoconstriction. The blood vessels which are close to the surface of your skin get smaller in diameter (constrict). Less blood gets to the surface of the skin, so less heat is lost to the surroundings.
• Shivering. Your muscles rapidly contract, increasing the rate of respiration and warming the tissue surrounding the muscles.

• Processed foods are high in simple sugars, which are quickly absorbed into the blood stream
• This causes a rise in blood sugar level
• The body needs to control the amount of sugar in your blood. The pancreas releases insulin, causing sugar to be removed from the blood

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 Type 1 Diabetes

• Where the pancreas stops producing insulin
• This means your blood sugar could rise dangerously high
• Controlled by injecting insulin into the bloodstream at mealtimes, to control the sugar level

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Type 2 Diabetes

• Sometimes called late onset diabetes as it usually develops later in life. Develops as a result of obesity or poor diet.
• Occurs when the body no longer responds to its own insulin or doesn't make enough insulin
• Controlled by exercise and a carefully controlled diet

• Someone who suffers from type 2 diabetes can keep their blood sugar level steady by eating foods high in fibre and complex carbohydrates
• These types of food are digested more slowly than simple sugars, so the sugar is absorbed into the blood over a longer period of time
• This means the blood sugar level rises more slowly, so the body can remove the sugar through respiration before it becomes too high

• A perfect closed loop system has no waste, as the output to one part of the system is used as the input to another part
• An Ecosystem is a type of closed loop system, as most of the output (waste) is recycled as food or reactants for other organisms in a system

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• Oxygen. It's a waste product of photosynthesis, but is used as a reactant for respiration
• Carbon Dioxide. It's a waste product of respiration, but is used as a reactant for photosynthesis
• Dead organic matter (fallen petals, leaves, fruit and faeces). Used by microorganisms as food
• Mineral nutrients (nitrogen). Produced by microorganisms when their digestive enzymes break down organic matter. These nutrients are then absorbed and used by plants

• No ecosystem is a perfect closed loop system, as there is always some energy lost: e.g.
• Organic matter and nutrients carried out of an ecosystem by air or water
• Organisms migrating to another ecosystem

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• However, in a stable ecosystem, the outputs are balanced by the inputs
• For example, in a rainforest, the loss of water through rivers is balanced by the amount of rainfall

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• Many organisms produce large quantities of reproductive structures (eggs, sperm, pollen, flowers and fruit) as it increases the chance of successful reproduction
• However, this is not wasteful as the the surplus are recycled in the ecosystem

• Large amounts of vegetation grow in a stable environment, such as a rainforest. This is beneficial because:

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• It promotes cloud formation
• It prevents extremes of temperatures.
• It reduces soil erosion. This is because leaves protect soil from direct rainfall, and roots help bind the soil together

• Humans depend on ecosystems to provide clean air, water, food (like fish and game), fertile soil (which provides mineral nutrients) and pollination. This is a 'ecosystem service'

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 Human Systems are open loop systems

• Human systems create non-renewable waste, which can't be recycled in the system
• Many human systems use fossil fuels such as crude oil as an energy source. This produces waste emissions that can't be recycled in the system. Not only this, but these fuels take  millions of years to form, from the decay of dead organisms. As they take so long to form, they can't be made again within a system

• Human actions can unbalance natural ecosystems by changing inputs and outputs.

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For Example: 

• Fertilisers. Farmers give plants extra nutrients such as nitrates to encourage growth. However, this leaves too many nutrients in the ecosystem, and can lead to eutrophication (see later)
• Biomass. Humans take biomass for their own use. Overfishing removes food sources for some organisms and unsustainable timber harvesting removes an organism's food sources and habitat
• Vegetation. Humans often clear natural areas of vegetation to grow agricultural crops and raise livestock.This can reduce biodiversity. It can also increase soil erosion, leading to the silting of rivers (when soil is washed into rivers, making them more likely to flood, as they can hold less water). It also results in desertification, where land becomes infertile, so can't hold much vegetation
• Waste. Human activity creates non-renewable waste, which can bioaccumulate.

• Sustainability means meeting the needs of today's generation without harming the environment, so future generations can still meet their needs
• To use resources sustainably, we have put fishing quotas in place, to prevent over-fishing and stop extinction. We have also planted new trees to make wood and paper production sustainable.

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•  The sun's energy is sustainable, as it can't be used up by human activities: the amount of sunlight we'll have available to us in the future won't be affected by how much sunlight we use in the present
• In natural ecosystems, sunlight is used as a  sustainable energy source which is used for photosynthesis. It is initially stored as carbohydrates, and is transferred between organisms when they're eaten
• In agriculture, sunlight can also be a sustainable energy source. Sunlight could be used to power equipment in sustainable agriculture.
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• There is tension between communities as to whether ecosystems should be damaged to get the resources they need, or whether the ecosystem should be protected but they get fewer resources from it.

• Nitrates are leeched into a lake by rain
• These nitrates encourage algal bloom on the surface of the lake
• These algae prevent light from reaching plants and other algae below them
• These organisms die, as they can't photosythesise
• Bacteria decompose these dead organisms, using up the oxygen
• The oxygen can't be replaced, as photosynthesis is only taking place at the surface of the lake
• Animals which are below the surface of the lake and need oxygen to survive (such as fish) will suffocate

• Reproduction. They reproduce rapidly under the right conditions, so products can be made quickly
• Plasmids. They have plasmids, so can be genetically modified to produce the product required
• Simplicity. The biochemistry is quite simple - fewer reactions happen in microorganisms than in humans. This means you can make microorganisms produce things without causing them any major problems
• Ability. They can make complex molecules that are difficult to produce artificially
• Ethics. There are no ethical concerns with using microorganisms

• Bacteria and fungi can be grown on a large scale, this is fermentation. This produces...

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• Antibiotics. Some microorganisms can produce medicines on a large scale
• Food. Some fungi produce a single-celled protein which is used as a meat substitute for vegetarians. Enzymes can also be used for food production. A mix of enzymes called rennet is used to produce cheese, and chymosin can be used as a substitute for rennet.
• Washing powders. Enzymes produced by bacteria can make biological washing powders, as they help to break down stains. Amylase can remove carbohydrate stains, and lipases get rid of fat stains
• Biofuels. Yeast is used to produce ethanol. Microorganisms can be used to produce biogas, which is used for heating, cooking and lighting.

• Genetic Modification is where a gene is transferred from one organism to another
• The organism with the transferred gene will then produce a protein using the instructions in that gene
• Even though the gene came from a different organism, the protein will still be made, as all organisms use the same genetic code

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Steps

• Isolate the gene responsible for producing the desired protein and replicate it
• Join the gene to a vector (these are usually plasmids and viruses)
• Use the vector to insert the gene into the new cells
• Select the individual cells that have been successfully modified

Medicines

• Insulin can be produced cheaply, quickly and in large quantities through genetic modification
• The gene for human insulin production is transferred straight from a human into bacteria, which is in a fermenter
• As the insulin produced is the same as human insulin, there is less chance of an allergic reaction

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Crops

• Some plants have natural resistance to herbicides
• If we cut out the gene responsible for resistance, we can make other plants herbicide resistant - this is useful for farmers
• However, this is expensive, and some people are worried the gene may be transferred into plants into wild plants (e.g. weeds) and make them hard to kill. Also herbicide-resistant crops may encourage the use of weedkillers, which could reduce biodiversity, and could get into food chains

Genetic Testing (testing for a genetic disorder caused by a faulty gene)

• DNA Sample. Isolating DNA from a white blood cell to test for a genetic disorder
• Gene Probe. To identify a faulty gene, you produce a gene probe - a strand of bases complimentary to the faulty gene. The gene probe is then mixed with the DNA. If the gene is present, the probe will stick to it, and it will lock together perfectly. In order to find the probe, a fluorescent chemical marker is stuck to the end of the sequence of bases. The marker will glow if the faulty gene is present, and show you its position on the chromosome.

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Nanotechnology

•  Nanotechnology uses tiny structures that are about the size of small molecules. It can be used to make food last longer (adding nanoparticles to plastic keeps out oxygen and moisture). It could also be used to change the packaging's properties depending on conditions (packaging changing colour when milk goes off)

Stem Cells

• Tissues and organs grown from carbon can be used to treat illnesses.
• Leukaemia is cancer of the blood or bone marrow. Stem cells could be grown to replace bone marrow
• In the future, stem cells could be used to treat spinal cord injuries by replacing damaged nerve tissues

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 Biomedical Engineering

• Using engineering techologies to improve human health, by creating replacement body parts
• Pacemakers help to maintain a regular heartbeat through producing an electric current
• Faulty heart valves could be replaced with animal or mechanical valves.