Biology B1A-B1H

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  • Created by: Molly
  • Created on: 31-05-12 13:44

The Heart

Systolic pressure - is the maximum pressure the heart produces

Diastolic pressure- is the blood pressure between heart beats

Systolic/diastolic = ___mmHg = blood pressure

Blood pressure is produced when muscles contract.

High blood pressure causes strokes, brain damage, parylsis and loss of speech.

Causes of high blood pressure - fatty foods, lack of exercise, salt, stress, smoking

Low blood presure causes poor circulation, dizziness and fainting

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Measuring Fitness


Stamina (Endurance)


Agility (How easily you can move)


Cardiovascular efficiency (How good good your heart is at supplying your tissues with oxygen/how well your circulatory system works)

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Arteries carry blood away from the heart. Blood in the arteries is under pressure because of the contractions of the heart muscles. This allows blood to reach all parts of the body.

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Cigarettes contain nicotine and carbon monoxide.

Smoking increases blood pressure by increasing heart rate. Nicotine increases heart rate and carbon dioxide reduces the oxygen-carrying capacity of the blood. It combines will the haemoglobin in red blood cells, preventing oxygen combining with the haemoglobin. This causes an increase in heart rate to compensate for the reduced amount of oxygen carried in the blood.

Smoking increases the risk of lung cancer, and cancer if the mouth, throat and oeasophagus.

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Heart Disease

Blood vessels called the coronary arteries supply blood to the heart muscles. If they become blocked, a heart attack can happen.

Fatty deposits build up in the contrary arteries.

A blood clot can form can form on a fatty deposit.

The blood clot can block a coronary artery.

Some heart muscle cells do not get the oxygen and nutrients they need.

These cells start to die.



High blood pressure

High levels of salt (can lead to increased blood pressure) and saturated fat in the diet (can lead to a build up of cholesterol in the arteries, causing a plaque and narrowing the arteries)

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Balanced Diet


Carbohydrates - simple sugars such as glucose, high-energy source

Fats - fatty acids and glycerol, high-energy source

Protein - amino acids, growth and repair, emergency source of energy

Minerals - iron, to make the haemoglobin needed to make red blood cells

Vitamins - vitamin c, prevents scurvy

Fibre - prevents constipation


Balanced diets are different for different people, for example women need more iron in their diets to replace iron lost in menstrual blood, children and teenagers need more protein for growth and older people need more calcium to protect against degenerative bone diseases (osteoporosis).




Physical activity

Religious reasons

Personal reasons (vegetarians)

Medical reasons

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Being overweight can cause the following:

Diabetes - the body is unable to control the amount of sugar in the blood

Arthritis - joints become worm, inflamed and painful

Heart disease

Breast cancer

BMI = mass (in kg)/(height in m)2*

*squared not x2

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Children and teenagers need more protein for growth. Pregnant women and new mothers who are breast feeding also need more protein, which is why EAR is not always accurate.

EAR (in g) = 0.6 x body mass (in kg)

Kwashiorkor, a disease caused by protein defiency - common in developing countries, caused by overpopulation (too many people for the land and the resources) and limited investments in farming methods (few tractors or artificial fertilisers).

The body does not store protein. It stores fats around organs and under skin as adipose tissue. Carbohydrates are converted in fats or stored in the liver as glycogen.

Proteins from animals are first class proteins; they contain all the essential amino acids, including those the body can't make.

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Pathogens are microorganisms that cause disease. The immune system can destroy pathogens that manage to enter the body.

Bacteria - cholera

Viruses - flu

Fungi - athlete's foot

Protozoa - malaria

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Parasites are organisms that live on or in a host organism. The parasite benefits fronthis arrangement but the host suffers. Parasites cause us harm by damaging our cells or releasing toxins.

Malaria is caused by a protozoan (a type of single-celled organism) . Malaria is spread by mosquitoes. The malaria parasite is passed on when the mosquito feeds. Mosquitoes are vectors because they spread malaria but do not cause it. The spread of malaria can be controlled if contact with the vector if avoided, for example putting up mosquito nets or killing mosquitoes with insecticides. The parasite can be killed by giving infected people drugs such as Lariam.

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Pathogens reproduce once inside the body. Viruses reproduce inside cells and damage them, while escaping to infect more cells. Bacteria produce toxins (poisons). Cell damage and toxins causes symptoms of infectious diseases.

Pathogens contain certain chemicals that are foreign to the body called antigens.

White blood cells:

Engulf pathogens and destroy them

Produce antibodies (proteins that have a chemical 'fit' to a certain antigen) to destroy pathogens

Produce antitoxins that neutralise the toxins released by pathogens

When a White blood cell with the appropriate antibody meets the antigen, it reproduces quickly and makes many copies of the antibody to neutralise the pathogen. This is immunity. Active immunity, more specifically because you make your own antibodies. Passive immunity is when you receive antibodies (when you have been prescribed antibiotics).

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Cancer happens when cells begin to divide out of control. Smoking increases the rusk of lung cancer, using sunscreen reduces the risk of skin cancer and eating more fruit and vegetables reduces the risk of bowel cancer.

Benign tumours - grow slowly and are usually harmless

Malignant tumours - grow more quickly and may spread throughout the body

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Body Defenses

The skin - difficult to penetrate, protection from physical damage, microbe infection and dehydration.

Blood clotting - forms a sort of mesh made up of platelets and fibrin mesh.

Mucus - traps dust and microbes, which is then carried away by the cillia.

Stomach acid - Hydrocholoric acid kills mircoorganisms in food and drink.

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Immunity 2

Vaccinations involves putting a small amount of an inactive form of a pathogen or a dead pathogen into the body. Vaccines can contain:

Live pathogens treated to make them harmless

Harmless fragments of the pathogen

Toxins produced by pathogens

Dead pathogens

These all act as antigens, when injected into the body they stimulate white blood cells to produce antibodies against the pathogen.

Bacteria can be become resistant to certain antibiotics (MRSA). To slow down or stop the development of other strains of resistant bacteria, we should avoid unnecessary use of antibiotics and complete the full course.

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The Nervous System

The sense organs contain receptors (groups of specialised cells that can detect changes in the environment (stimuli)) that are sensitive to the stimuli. Each sense organ has receptors that are sensitive to particular kinds of stimulus.

Receptors found in:

Eyes - sensitive to light

Ears - sensitive to sound and position of the head

Tongue - sensitive to chemicals in food

Nose - sensitive to chemicals in the air

Skin - sensitive to touch, pressure, pain and temperature

Central nervous system - Brain and spinal cord and peripheral nerves

Nerve impulses travel through the axons of neurones - nerve cells.

Reflex actions are fast, automatic and protective responses.

Human vision is binocular, which gives us a good perception of depth.

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Most animal cells have a nucleaus, cytoplasm and cell membrane. Light receptors have these components too.

When a receptor is stimulated, it sends a signal along the nerve cells, also called neurones, to the brain which then co-ordinates a response.

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The Eye

Cornea - refracts (bends) light into the eye

Iris - controls how much light enters the pupil

Lens - focuses light onto the retina

Retina - contains the light receptors

Optic nerve - carries impulses from the eye to the brain

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Light passes through the eyeball to the retina. It is refracted by the cornea and lens , so that light is brought to focus on the retina.

Our eyes sit side by side, each eye captures a slightly different view. This is called binocular vision. When signals from the two eyes reach the brain, they are superimposed and processed into a single picture with depth. We get a 3D picture and can judge distances well.

Most birds and lizards have monocular vision - their eyes are on each side of their head. This gives them a greater field of view, which is useful for spotting predators. However, they have poor depth perception.

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Vision Defects

Short-sight (Myopia) - the lens focuses the sharpest image in front of the retina, instead of on it, this is caused by the eyeball being elongated, the distance between the lens and the cornea is too great. It can be corrected by placing s concave lens in front of the eye.

Long-sight (Hypermetropia) - the lens focuses the sharpest image behind the retina, instead of on it, often age-related and due to a loss of elasticity in the lens. It is corrected by placing a convex lens in front of the eye.

Colour blindness - an inherited condition, people with colour blindness have a lack of receptors or defects in them.

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Neurones are nerve cells. They carry information as tiny electrical signals.

Sensory - carry information from our senses to the brain and spinal cord

Motor - carry information from the brain and spinal cord to muscles to make things move

Relay - carry information between other neurones

Synapses - a tiny gap where two neurones meet. Signals cross this gap using chemicals. One neurone releases the chemical into the gap. The chemical diffuses across the gap and makes the next neurone transmit an electrical signal.

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Reflex Actions

Sometimes a very quick response is needed, one that does not need the involvement of the brain. This is a reflex action.


Stimulus -> receptor -> sensory neurone -> relay neurone -> motor neurone -> effector

Receptor detects a change in the environment (stimulus), sensory neurone sends signal to relay neurone, motor neurone sends signal to effector, effector produces response.


A muscle contracting

A gland releasing (secreting) a hormone or other chemical

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Drugs are chemicals that alter the way our body works.

Class A - most dangerous

Class C - least dangerous

Depressant - slows down brain activity, alcohol, solvents, temazepam

Stimulant - increases brain activity, nicotine, ecstasy, caffeine

Hallucinogen - changes what we see and hear, LSD, cannabis

Painkiller -reduces pain, aspirin, heroin

Performance enhancer - improved athletic performance, anabolic steriods

Stimulants cause more neurotransmitter molecules to diffuse across the synapse

Depressants stop the next neurone sending nerve impulses - they bind to the receptor molecules it needs to respond to the neurotransmitter molecules.

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The cells lining the trachea (windpipe), bronchi and bronchioles (the branches inside the lungs) are damaged by cigarette smoke. These epithelial cells have tiny hair-like cilia on their surface. These cilia move to push mucus out of the lungs. Damaged cells cannot do this, leading to a build-up of mucus and a smoker's cough.

(See smoking for information on Nicotine and Carbon Monoxide)

Tars - tobacco contains tar, tar is a carcinogen, carcinogens cause cancer.

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Short-term effects - sleepiness, impaired judgement, balance and muscle control. This leads to blurry vision and slurred speech. Blood flow to the skin is also increased, which can cause it to go red.

Long-term effects - damage to the liver and the brain.

The liver removes alcohol from the bloodstream. It has enzymes that break down the alcohol but the products of the reactions involved are toxic. They damage the liver and over time this leads to cirrhosis.

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Maintaining a constant internal environment of the body is called homeostasis. The nervous system and hormones are responsible for this.

Carbon dioxide - levels must be controlled to avoid the blood becoming too acidic or too alkaline.
Body temperature - shivering, sweating, altering blood flow to the skin, temperature is kept at 37 degrees because this is the temperature at which enzymes work best.
Body's water content - stopping too much water from entering or leaving cells, lungs when we exhales, skin by sweating, body, in urine produced in the kidneys.

Low temperatures can cause hypothermia and death.
High temperatures can cause dehydration, heat stroke and death.

Gaining heat - respiration, shivering, exercise
Reducing heat - sweating

Body temperature is monitored by a part of the brain called hypothalamus. If you are too hot or too cold, it sends nerve impulses to the skin. Blood vessels supplying blood to the skin can dilate or swell (vasodilation). More heat can be carried by the blood to the skin, where it can be lost to the surroundings.

Blood vessels van shrink down again (vasoconstriction). It reduces heat loss from the skin once the body's temperature has returned to normal.

This sort of control is a 'negative feedback mechanism'. The body's internal environment is kept almost constant by cooling it when it is too hot, and warming it when it is too cold.

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Hormones are chemicals secreted by glands in the body. Different hormones affect different target organs.

The bloodstream transports hormones from the glands to the target organs. Bodily reactions to hormones are usually slower and longer lasting than nervous reactions.

The Pancreas produces insulin which controls blood sugar levels. Insulin travels in the bloodstream.

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Blood Sugar

Glucose is a sugar needed by cells for respiration. It is important that the concentration of glucose in the blood is maintained at a constant level.

Insulin, a hormone secreted by the pancreas, controls blood sugar levels in the body. It travels from the pancreas to the liver in the bloodstream. As with other responses controlled by hormones, the response is slower but longer lasting than if it had been controlled by the nervous system.

Glucose level:

Too high - insulin secreted into the blood, liver converts glucose into glycogen, level goes down.

Too low - insulin not secreted into the blood, liver does not convert glucose into glycogen, level goes up.

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Too much glucose in the blood:

Pancreas prouces insulin which enters blood, insulin allows glucose to be absorbed by body cells, blood glucose reduced.

Too little glucose in the blood:

Insulin not produced by the pancreas, less glucose absorbed by body cells, blood glucose increased.

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Type 1 - usually develops during childhood, affects children and teenagers and adults under 40, the pancreas stops making enough insulin, it is controlled by injections of insulin for life and an appropriate diet.

Type 2 - usually develops during later life, affects adults over 40 and people who are overweight, the body no longer responds to its insulin, controlled by exercise and an appropriate diet.

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A 'tropism' is a growth in response to a stimulus. Plants grow towards sources of water and light, which they need to survive and grow.

Auxin is a plant hormone produced in the stem tips and roots, which controls the direction of growth. Plant hormones are used in weedkillers, rooting powder and to control fruit ripening.

Plants need light and water for photosynthesis. They have developed responses called tropisms to help make sure they grow towards sources of light and water.

  • Positive tropisms – the plant grows towards the stimulus
  • Negative tropisms – the plant grows away from the stimulus.

Shoot - positive phototropism (grow towards the light), negative geotropism (grow against the force of gravity)

Root - negative phototropism (grow away from the light), positive geotropism (grow in the direction of the force of gravity)

The tropisms of shoots mean that they are likely to grow into the air, where there is light for photosynthesis.

The tropisms of roots mean that they are likely to grow into the soil, where there is moisture.

Tropisms are controlled by plant hormones called auxins. These water-soluble chemicals move through the plant in solution.

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Plant Hormones

Weed killers - attack some plants but not others, contains growth hormone that causes the weeds to grow too quickly, absorbed in larger quantities by the weeds rather than the beneficial plants.

Rooting powder - makes stem cuttings quickly develop roots, contains growth hormones.

Fruit ripening - some slow the ripening of fruits and others speed it up, useful for delaying ripening during transport or when fruit is displayed in shops.

Dormancy - stops seeds germinating until conditions are ideal for growth, can be used to remove the dormancy of a seed so it can germinate at all times of year, can also be used to make plants grow bushier, make them flower or control the growth of hedge plants.

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Auxins are mostly made in the tips of the shoots and roots, and can diffuse to other parts of the plant. Auxins change the rate of elongation in plant cells, controlling how long they become. Shoots and roots respond differently to high concentrations of auxins. Cells in shoots grow more, cells in roots grow less.

If the tips of a seedling have been removed, no auxin is produced and the shoots do not grow longer.

If the tips have been covered so light cannot reach them, the auxin is in the same concentration on both sides of the shoots, so they grow longer evenly on both sides.

If one side of the tips are in more light than the other side, the auxin is in a greater concentration on the shaded side, causing the cells there to grow longer than the cells on the light side.

Auxins have the opposite effect on root cells. In a root, the shaded side contains more auxin, but this time the shaded side grows less than the light side. This causes the root to bend away from the light.

Auxins are also involved geotropisms. In a root placed horizontally, the bottom side contains more auxin than the top side. This makes the bottom side grow less than the top side, causing the root to bend in the direction of the force of gravity.

In a shoot placed horizontally, the bottom side contains more auxin than the top side. This makes the bottom side grow more than the top side, causing the shoot to bend and grow against the force of gravity.

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DNA, Genes and Chromosomes

DNA (deoxyribonucleic acid) molecules are large and complex. They carry the genetic code that determines the characteristics of a living thing.

Except for identical twins, each person’s DNA is unique. This is why people can be identified using DNA fingerprinting. DNA can be cut up and separated, forming a sort of 'bar code' that is different from one person to the next.

A gene is a short section of DNA. Each gene codes for a specific protein by specifying the order in which amino acids must be joined together.

The cell’s nucleus contains chromosomes made from long DNA molecules.

The diagram shows the relationship between the cell, its nucleus, chromosomes in the nucleus, and genes.

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Gametes are sex cells. The male gametes are the sperm, and the female gametes are the eggs.

Gametes contain half the number of chromosomes as body cells do. They contain half the genetic information that body cells do

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An individual is homozygous for a certain gene if they have two identical alleles. They are heterozygous for a certain gene if they two different alleles.

The genotype is the genetic makeup of an individual. For example, it is the particular combination of alleles.

The phenotype is the characteristics expressed by an individual. For example, it is the actual eye colour.

Inherited disorders are caused by faulty genes, which are mostly (but not always) recessive alleles. For example, cystic fibrosis is an inherited disorder that affects the cell membranes, causing the production of thick and sticky mucus. It is caused by a recessive allele, which means that it must be inherited from both parents.

Scientists are now able to test adults and unborn babies for alleles that can cause genetic disorders. However, the scientific information produced raises many issues that science cannot address. For example, should a couple with a one in four risk of having a child with cystic fibrosis take the gamble, or decide not to have any children at all? If a woman becomes pregnant with a child that is going to have cystic fibrosis, should she have the child, or choose to have an abortion?

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