Biology Unit 1: Understanding Organisms

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Fitness and Health

Fitness: your physical ability to complete exercise

Health: you ability to fight disease

Fitness can be measured by: 

  • strength
  • flexibility
  • stamina
  • agility
  • speed
  • cardiovascular efficiency
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Blood Pressure

Blood pressure is the pressure at which blood travels through vessels, measured in systolic pressure (maximum pressure) and diastolic (relaxed pressure). It is increased by:

  • stess
  • smoke
  • obesity
  • high alcohol intake

The risks of high blood pressure are:

  • burst blood vessels: stroke
  • kidney damage

Blood pressure can be lowered by completing regular exercise and a balanced diet.

The risks of low blood pressure are:

  • fainting: due to poor circulation to the brain
  • dizziness
  • poor circulation to toes and fingers
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Smoking can increase blood pressure by:

  • nicotine: directly increases blood pressure
  • carbon monoxide: causes the blood to carry less oxygen and so the heart has to beat faster to compensate for the lack of oxygen
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Heart Disease

Heart disease is caused by the restriction of blood flow to the heart caused by a high cholesterol, involving plaque lining the walls of the arteries. High levels of salt then increase the blood pressure which increases the risk of heart disease. 

The narrowing of the arteries can also make thrombosis more likely to happen as plaque may become dislodged by high blood pressure and block the artery, restricting blood flow once more. 

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Balanced Diet

A balanced diet varies upon age, gender, activity and belief. The main things required for a balanced diet are:

  • carbohydrates - made up of sugars like glucose and stored as starch and converted into glycogen (by insulin) to be stored in the liver
  • fats - made up of fatty acids and gylcerol and stored as adipose tissue around your organs
  • proteins: first class (from meat) and second class (from plants) proteins are made up of amino acids and can't be stored in the body and produce urea as a waste product. Your daily requirement or EAR is 0.6 x body mass in kg

To work out if you are overweigh or underweight you can calculate something called your BMI or your Body Mass Index. The equation is: BMI = body mass in kg / height in metres squared

The grading is then as follows:

  • 30+ = obese
  • 30-25 = overweight
  • 25-20 = normal
  • less than 20 = underweight
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Malaria and Vaccination

Malaria is a disease caused by a protozoan and parasite called plasmodium which feeds on human red blood cells. Plasmodium is transmitted by mosquitoes, which are vectors (carriers) for this, when they bite into the human host, injecting plasmodium into the blood stream. Malaria can be prevented through stopping mosquitoes biting you using a net or by preventing the production of more mosquitoes by draining stagnant water (where mosquitoes breed) or spraying it with insecticide.

Alternatively you can have a vaccination producing passive immunity. This is by:

  • inserting a harmless pathogen
  • pathogen produces toxins and antigens triggering immune response by white blood cells
  • white blood cells produce antibodies which engulf the antigens and kill it
  • memory cells (type of lymphocyte cells) remember the antibodies needed to fight malaria

Whilst passive immunity carries a small risk, it prevents a disease from spreading and avoids the potentially lethal effect without it.

Active Immunity is when the body is exposed to a pathogen naturally.

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Cancer and Medical Trials

There are two types of tumorous cells:

  • benign - slowly dividing cells like warts that are harmless
  • malignant - rapidly dividing cells 

Cancer can be prevented by using sunscreen (prevents skin cancer) and by not smoking (lung cancer). 

As new types of drug are introduced in order to treat cancer, trials are required to ensure their safety before mass use. This is by:

  • blind trial: a placebo (harmless ineffective drug) is used to make a control group as well as the real group and the patients don't know what they receive
  • double blind trial: as above but doctors don't know who has received which drug either to prevent favouritism
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You are able to see because light passes off an object, refracts through the cornea, passes through the pupil (light entering is controlled by the iris) and is focused on the retina by the lens. The optic nerve then carries the information to the brain. Humans have binocular vision. This means that the images from each eye are superimposed (layed on top of eachother) and the more similar the images are, the further away the object is.

To focus on distant or near objects the eye goes through a process called accomodation:

  • CCC - ciliary contract close - the ciliary muscles contract to see near objects and the suspensory ligaments relax
  • Then, to see distant objects, the suspensory ligaments contract and the ciliary muscles relax

There are also some problems in vision:

  • red - green colour blindness: caused by a lack of specialised cells in the retina
  • short sighted (you CAN see close but NOT far) - the eyeball is too long and so the lens focuses the image in front of the retina instead of on it (SHORT people have to stand IN FRONT). Requires concave lenses (SHORT people can stand in CAVES)
  • long sighted (you can't see close) - the eyeball is too short so the lens focuses the image behind the retina. Requires convex lenses. 
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Nerve Cells (AKA Neurones)

When you put your hand it boiling water, you immediately sense the heat and pain so pull it out very quickly. This is because the boiling water has acted as the stimulus for your nerves, this causes the path: 

receptor - sensory neurone - CNS (central nervous system) - motor neurone - effector (what part of the body moves; e.g. hand) - response (what you do; e.g. yank your hand out of the water)

Alternatively a spinal reflex arc is:

receptor - sensory neurone - relay neurone - motor neurone - effector 

These neurones are adapted for a quick and efficient transmission by having an insulating sheath around the nerve to promote effective transmission and also have branching dendrites to connect to pick up impulses. 

Between each step the arrival of a nerve impulse at a neurone triggers the release of a transmitter substance that can cross the space between two neurones (the synapse). The transmitter substance then binds with the receptor molecules in the membrane of the receiving neurone, allowing the impulse to continue.

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Drugs, Alcohol and Smoking

There are 5 types of drugs:

  • hallucinogens (LSD)
  • pain killers (paracetamol, aspirin)
  • performance enhancers (anabolic steroids)
  • stimulants (caffeine, nicotine) - they cause the heart rate to increase as well as increasing the amount of transmitter substance released across the synapse making responses faster
  • depressants (alcohol, tamazepam) - the increase your reaction times (longer thinking distance for example) by blocking the transmission of nerve impulses across the synapse by binding with the receptor molecules in the membrane of the receiving neurone.

The liver is also damaged when it breaks down alcohol as the toxic chemicals in it cause scarring. This is called liver cirrhosis. 

Cigerattes cause a smoker's cough because the smoke and dust stop iritate the epithelial cells and stop cilia in the lungs from moving mucus, this causes a build up of mucus and the cough.

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The body is damaged if it becomes unbalanced; if it gets too hot/cold, has too much water or carbon dioxide.This is why the hypothalamus gland in the brain senses the temperature and concentration of the blood in order to trigger a negative feedback (act to cancel out a change). The optimum temperature for the body is 36 degrees Celsius because this is the temperature at which the enzymes in the body work best, if it gets too hot they denature and will no longer work effectively.

A high temperature can cause heat stroke and dehydration (leading to death) and so the body adapted to have ways to cool down:

  • sweating: energy is transferred when the water produced by sweat glands evaporates off of the skin 
  • vasodilation: the vessels dilate (expand), allowing blood to flow closer to the surface of the skin and so more heat transfer can occur.

Alternatively, if too much heat is lost hypothermia can occur (can be fatal) and to prevent this vasoconstriction occurs. This is when the blood vessels constrict (get smaller), stopping the blood from flowing too close the surface of the skin and preventing heat loss

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It is important to control the sugar levels of the blood and this is done by a hormone called insulin. Insulin is able to convert the excess glucose in the blood from your food into glycogen to be stored in the liver. However, sometimes this is ineffective in an illness called diabetes:

  • Type 1 Diabetes: the pancreas doesn't produce any insulin so an insulin injection is required dependent upon the person's activity and diet
  • Type 2 Diabetes: body producing too little insulin or when the body doesn't react to it caused, most commonly, by a bad diet and therefore can be regulated by a more healthy diet
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Plant Growth and Hormones

Plant growth is controlled by hormones called auxins. They are found in the root and tip of the plant and on the shaded side of the plant because auxins are damaged by light. This causes the shady side of the plant to grow more (as do the shielded roots) because there is more auxin, causing plant curvature towards the light. This response to light is called positive phototropism, whilst the response by the roots is positively geotrophic as it grows with the pull of gravity. 

Auxins and other pant hormones can also be used commercially in:

  • weed killers: cause the plant to weed to grow too rapidly and die
  • rooting powder: causes the roots to grow faster
  • control seed dormancy: used in transport to stop them sprouting
  • accelerating or slowing growth
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Genetic Variation

You can inherit characteristics from your parents through your genes, as well as develop new ones through the environment. This can be predicted using a punnet square (a genetic diagram).  This is because your parents have different chromosomes (female - **, male - XY) and genes that combine to make you - the zygote. Genetic variation is also caused by mutations (random changes in chromosomes) and the rearrangement of genes during meiosis (producing gametes).

A gene can have different versions of itself. These are called alleles and can be dominant and recessive. The dominant allele is often the gene expressed (your phenotype) but together, dominant and recessive alleles make up your genotype (the genes you have). The recessive allele is only expressed in the absence of the dominant allele and can often be faulty, causing inherited disease. If you have two dominant or recessive alleles you are homozygous (think homosexual - same sex), if you have one of each you are heterozygous. 

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