Biology Unit 1 Revision

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• We need a balanced diet. Carbohydrates, fats and proteins help regulate energy release and cell building..
• Vitamins and minerals allow the bod to function in a healthy manner. Deficiency of these cause a person to be malnourished. This causes a person to be overweight or underweight.

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• A person loses mass if the energy expenditure through exercise exceeds the energy intake of the body.
• The speed that the body can carry out chemical reactions is called the metabolic rate. This is affected by exercise that is carried out and the proportion of muscle to fat in the body.
• Inherited factors also affect our health such as cholesterol level.

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• The body is perfect for microscopic life. This means that microbes can easily survive within us. This means we fall ill easily.
• Microbes that cause infections are called pathogens. Pathogens reproduce quickly inside the body crating poisons that make us ill. Viruses damage cells in which they reproduce.

1. The immune system.

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   • White blood cells help counteract pathogens by ingesting pathogens, producing antibdies which destroy particular bacteria or viruses or producing antitoxins which counteract the toxins and poisons released by the bacteria or virus.
   • Semmelweis recognised the importance of hand-washing in the prevention of spreading some infectious diseases. By insisting that doctors washed their hands before examining patients, he greatly reduced the number of deaths from infectious diseases in his hospital.
   • The immunisation process: 1. A small amount of the inactive form of the pathogen is put in the body. 2. This stimulates the white blood cells to produce the appropriate antibodies. 3. When the pathogen enters the body as an infection, the white blood cells can act quicker to combat the infection.
2. Medicine

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   • Specific antibiotics destroy bacterial diseases but not viral diseases. Improper use of antibiotics is leading to a higher rate of antibiotic resistance in bacteria.
   • Some medicines such as painkillers relieve the symptoms of an infection but do not kill the pathogens.

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• The nervous system enables organisms to react to their surroundings.
• Receptors in the body react to stimuli such as light, sound, touch, pressure, pain and movement.
• Information from receptors passes along cells (neurones) in nerves to the brain. The brain coordinates the response. Reflex actions are automatic and rapid. They often involve sensory, relay and motor neurones. 
• Reflex actions are quicker as they bypass the brain and the impulse is sent straight to the effector muscle usually as a sudden movement such as a blink.

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• Internal factors that are controlled include water level, ion levels, temperature and blood sugar levels.
• Most processes inside the body are controlled by hormones which are secreted by glands and passed through the body in the blood stream
• The Pituitary gland and the Ovaries in a woman release hormones which control the menstrual cycle.
• FSH ,produced in the Pituitary gland, stimulates the maturing of an egg and also stimulates the ovaries to produce other hormones such as Oestrogen.
• LH stimulates the release of an egg from the ovaries.
• Oestrogen stops the Pituitary gland from producing more FSH

1. Contraceptive Pills

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   • Contraceptive pills contain hormones such as Oestrogen and Progesterone which inhibits FSH production therefore inhibiting the maturing of eggs.
   • Early contraceptive pills contained a very high dose of Oestrogen which lead to massive side effects. These days, we lean towards Progesterone only pills.
2. Fertility Treatment

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   • IVF treatment involves giving the mother FSH and LH to stimulate egg production. The eggs are then extracted from the woman and fertilised by the male sperm. When embryos have formed, one or two are put back into the mother's uterus to form a baby.

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• Plants are sensitive to light, moisture and gravity.
• Plants produce a hormone called auxin. This stimulates and controls the rate of cell growth in the plant.
• Plant growth hormones are used as weed killer and rooting powder.

1. Drugs Testing

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   • Drugs must be tested to determine toxicity, effectiveness and optimum dosage.
   • Testing begins by using tissues and live animals as models to gauge how humans would react to the drug.
   • In clinical tests, healthy people are given small amounts of the drug as they have better immune systems in case the drug is toxic.
   • A double-blind test is carried out on patients with the targeted illness. Half of the patients are given a placebo which contains no drug and the other half are given the actual drug. Neither the patient nor the doctor know which is which. This allows the drugs effectiveness to be measured against psychological  effects.
2. Statins

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   • Statins are used to control cholesterol levels.
   • When travelling through the body, cholesterol is coated in a protein to form a lipoprotein. If there is too much cholesterol in the lipoprotein, it forms and LDL or  "bad cholesterol". This can cause it to lave a trail behind as it travels through the body which can clog up the body.
3. Thalidomide

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   • Thalidomide is a drug that was developed as a sleeping pill. It was also found to be effective in relieving morning sickness in pregnant women. Thalidomide had not been tested for use in pregnant women. Unfortunately, many babies born to mothers who took the drug were born with severe limb abnormalities. The drug was then banned. As a result, drug testing has become much more rigorous. More recently, thalidomide has been used successfully in the treatment of leprosy and other diseases.

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• The negative effects on society from illegal drugs is far inferior to that of legal drugs because illegal drugs are used less often.
• Drugs change the chemical processes in the brain to make the user become dependant on the drug.

1. Legal
   1. Nicotine

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      • Smoking raises heart rate and reduces most senses such as taste and smell.
      • Nicotine is known to cause many cancers along with breathing difficulties caused by tar build-up within the lungs.
   2. Alcohol

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      • Alcohol slows down the brain, it makes you feel relaxed. It reduces concentration hence driving under the influence is illegal. Coordination and behaviour is also negatively affected.
      • In the long term, alcohol can cause blood and liver disorders. Alcohol also affects the brain and can sometimes cause mental illnesses such as depression. It increases risk of major illnesses like cancer. Drinking can also harm fetuses during pregnancy.
2. Illegal
   1. Cannabis

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      • Cannabis smoke contains chemicals that can cause mental illness.
      • In the short-term, cannabis stimulates the brain to produce dopamine (this is where the slang term dope comes from) it is this chemical which makes you feel "high"
      • In the long-term, the active chemical within Cannabis (THC) affects the brains receptors to give similar effects to alcohol. Mental illnesses such as schizophrenia are also caused by the effects of THC.

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• There are several types of  drug that an athlete can use to enhance performance. Some of these drugs are banned by law and some are legally available on prescription, but all are prohibited by sporting regulations. Examples include stimulants that boost bodily functions such as heart rate; and anabolic steroids which stimulate muscle growth.

1. Animals

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   • Animals compete for food, habitat and mates.
   • Animals may adapt by changes in surface area, body fat and thickness of coat (temperature) and surface colour (camouflage).
2. Plants

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   • Plants compete for light, space and water and nutrients from the soil.
   • Plants may adapt by changes in surface area (on leaves especially), water storage tissues, height (for light) and root systems (stability).
3. Extremophiles

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   • Extremophiles are organisms that are tolerant to extremes in surroundings such as high/low temperatures, high salt and high pressure.

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• Changes in the environment can affect the distribution of species. eg. bird distribution is affected by seed type distribution. 
• The distributions of different types of lichens can be used as indicators of air pollutants. The distributions of aquatic invertebrates can be used as indicators of water pollutants.

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• The energy in light rays from the sun is the source of energy for most organisms. The transfer from light energy to chemical energy happens during photosynthesis in algae and small plants.
• The amount of biomass at each stage of the food chain is lower than the previous stage.
• Biomass is lost through waste production (excretion) and respiration.

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• Decay occurs when the material is digested by microorganisms. Microorganisms are most active in warm, moist, aerobic conditions.
• In a stable community, the processes which remove materials from the environment are balanced by those which return materials.

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• Carbon is taken from the atmosphere by plants and algae photosynthesising. When they respire, some of the carbon is returned as carbon dioxide.
• When these plants are eaten by animals, these animals return the carbon in respiration.
• When plants/animals die, the decomposers will eat them and take in the carbon in their bodies. When they respire, the carbon is returned to the atmosphere.
• Combustion of wood and fossil fuels releases further carbon into the atmosphere.

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• The reason that most organisms are similar to their parents is due to genes that are passed on in the sex cells from which the child develops.
• The reasons for differences in organisms can be caused by genes or the environment.

1. Asexual

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   • Asexual reproduction involves only one parent. The offspring are identical to the parent and are known as clones
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3. Sexual

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   • Sexual reproduction involves two parents. The offspring is formed by a fusion of gametes (sex cells). This means that the offspring are a mixture of the two parents.
4. Non-Natural Cloning

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   • People often intervene in the reproductive cycle of plants and sometimes animals. We often take cuttings from plants creating a clone of that plant. This is particularly useful if a plant has a certain characteristic that we want again.
   1. Tissue Culture

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      • Using small samples of tissue from a parent plant, we grow these using agar jelly into clones.
   2. Embryo Transplants

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      • Extracting embryo's from a mother before specialised cells form, splitting the embryo into multiple embryos and implanting into separate host mothers.
      • These are clones of one mother, not the host mother.
   3. Adult Cell Cloning

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      • The nucleus is removed from an unfertilized egg cell. The nucleus from and adult cell (eg. skin cell) is then placed within the empty egg. An electric shock then stimulates the cell into dividing.
      • These are clones of the adult from which the nucleus was extracted.

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• Darwin's theory of natural selection stated that all organisms have evolved fro simple organisms by characteristics that are needed to survive living on.
• This theory was only gradually accepted because it contravened religious ideology, there was sufficient evidence and other theories required to allow this theory to work were not discovered until 50 years later.

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• Other theories such as that of Lamark said that changes during an organisms lifetime could be inherited. We now know that this is impossible.