Biology: Keeping Healthy Essay

Candidates should use their skills, knowledge and understanding to: • evaluate information about the effect of food on health Additional guidance: Candidates will be given data to work from. 3 evaluate information about the effect of lifestyle on development of disease analyses and evaluate claims made by slimming programmed, and slimming products. Bal . 1. 1 Diet and exercise Additional guidance: a) A healthy diet contains the right balance of the different foods you need and the right amount of energy.

Carbohydrates, fats and proteins are used by the body to release energy and to build cells. Mineral ions and vitamins are needed in small amounts for healthy functioning of the body. A person is malnourished if their diet is not balanced. This may lead to a person being overweight or underweight. An unbalanced diet may also lead to deficiency diseases or conditions such as Type 2 diabetes. B) A person loses mass when the energy content of the food taken in is less than the amount of energy expended by the body. Exercise increases the amount of energy expended by the body. ) The rate at which all the chemical reactions in the cells of the body are carried out (the metabolic rate) varies with the amount of activity you do and the proportion of muscle to fat in your body. Metabolic rate may be affected by inherited factors. ) Inherited factors also affect our health; for example cholesterol level. Knowledge and understanding of the specific functions of nutrients and the effects of any delicately in the diet is not required e) People who exercise regularly are usually healthier than people who take little exercise.

The effect of exercise on breathing and heart rate is not required. 10 Bal . 1. 2 How our bodies defend themselves against infectious diseases Candidates should use their skills, knowledge and understanding to: • relate the contribution of Semisweet in controlling infection to solving modern problems with the spread of infection in hospitals • Additional guidance: Candidates will be given data to work from. Explain how the treatment of disease has changed as a result of increased understanding of the action of antibiotics and immunity evaluate the consequences of mutations of bacteria and viruses in relation to epidemics and pandemics evaluate the advantages and disadvantages of being vaccinated against a particular disease. A) Microorganisms that cause infectious disease are called pathogens. Additional guidance: b) Bacteria and viruses may reproduce rapidly inside the body and may produce poisons (toxins) that make us feel ill.

Viruses damage the cells in which they reproduce. C) The body has different ways of protecting itself against pathogens. D) White blood cells help to defend against pathogens by: Knowledge of the structure of bacteria and viruses is not required. Ingesting pathogens producing antibodies, which destroy particular bacteria or viruses producing antitoxins, which counteract the toxins released by the pathogens. E) The immune system of the body produces specific antibodies to kill a particular pathogen.

This leads to immunity from that pathogen. In some cases, dead or inactivated pathogens stimulate antibody production. If a large proportion of the population is immune to a pathogen, the spread of the pathogen is very much reduced. F) Semisweet recognized 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. 1 g) Some medicines, including painkillers, help to relieve the symptoms of infectious disease, but do not kill the pathogens. Additional guidance: h) Antibiotics, including penicillin, are medicines that help to cure bacterial disease y killing infectious bacteria inside the body. Antibiotics cannot be used to kill viral pathogens, which live and reproduce inside cells. It is important that specific bacteria should be treated by specific antibiotics.

The use of antibiotics has greatly reduced deaths from infectious bacterial diseases. Overuse and inappropriate use of antibiotics has increased the rate of development of antibiotic resistant strains of bacteria. I) Many strains of bacteria, including MRS., have developed resistance to antibiotics as a result of natural selection. To prevent further resistance arising it is important to avoid over-use of antibiotics. J) Mutations of pathogens produce new strains.

Antibiotics and vaccinations may no longer be effective against a new resistant strain of the pathogen. The new strain will then spread rapidly because people are not immune to it and there is no effective treatment. Higher Tier candidates should understand that: • Candidates should be aware that it is difficult to develop drugs that kill viruses without also damaging the body’s tissues. Knowledge of the development of resistance in bacteria is limited to the fact that pathogens mutate, producing resistant strains.

HTH only antibiotics kill individual pathogens tot the non-resistant strain individual resistant pathogens survive and reproduce, so the population of the resistant strain increases now, antibiotics are not used to treat non-serious infections, such as mild throat infections, so that the rate of development of resistant strains is slowed down. K) The development of antibiotic-resistant strains of bacteria necessitates the development of new antibiotics. Additional guidance: l) People can be unmissed against a disease by introducing small quantities of dead or inactive forms of the pathogen into the body (vaccination).

Vaccines stimulate the white blood cells to produce antibodies that destroy the pathogens. This makes the person immune to future infections by the microorganism. The body can respond by rapidly making the correct antibody, in the same way as if the person had previously had the disease. MR. vaccine is used to protect children against measles, mumps and rubella. Details of vaccination schedules and side effects associated with specific vaccines are not required. 12 m) Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants and antibiotics. For this: •

Petri dishes and culture media must be sterilized before use to kill unwanted microorganisms Subject Content inoculating loops used to transfer microorganisms to the media must be sterilized by passing them through a flame the lid of the Petri dish should be secured with adhesive tape to prevent microorganisms from the air contaminating the culture. N) In school and college laboratories, cultures should be incubated at a maximum temperature of 25 co, which greatly reduces the likelihood of growth of pathogens that might be harmful to humans. O) In industrial conditions higher temperatures can produce more rapid growth.

Suggested ideas for practical work to develop skills and understanding include the following: investigate the effectiveness of various antibiotic discs in killing bacteria growing microorganisms in Petri dishes to demonstrate sterile technique and growing pure cultures the use of pre-inoculated agar in Petri dishes to evaluate the effect of disinfectants and antibiotics computer simulations to model the effect of: balanced and unbalanced diets and exercise; the growth of bacterial colonies in varying conditions; action of the immune system and the effect of antibiotics and vaccines. Nerves and hormones

The nervous system and hormones enable us to respond to external changes. They also help us to control conditions inside our bodies. Hormones are used in some forms of contraception and in fertility treatments. Plants also produce hormones and respond to external stimuli. Candidates should use their skills, knowledge and understanding to: • evaluate the benefits of, and the problems that may arise from, the use of hormones to control fertility, including In Vitro Fertilization (IV) • evaluate the use of plant hormones in horticulture as headliners and to encourage the rooting of plant cuttings. 3 Bal . 2. 1 The nervous system ) The nervous system enables humans to react to their surroundings and coordinate their behavior. Additional guidance: b) Cells called receptors detect stimuli (changes in the environment). Receptors and the stimuli they detect include: Knowledge and understanding of the structure and functions of sense organs such as the eye and the ear are not required. Acceptors in the eyes that are sensitive to light receptors in the ears that are sensitive to sound receptors in the ears that are sensitive to changes in position and enable us to keep our balance receptors on the tongue and in the nose that are sensitive to Heimlich and enable us to taste and to smell receptors in the skin that are sensitive to touch, pressure, pain and to temperature changes. Additional guidance: c) Light receptor cells, like most animal cells, have a nucleus, cytoplasm and cell membrane.

A knowledge of the functions of the cell components is not required. D) Information from receptors passes along cells (neurons) in nerves to the brain. The brain coordinates the response. Reflex actions are automatic and rapid. They often involve sensory, relay and motor neurons. 14 e) Candidates should understand the role of receptors, sensory neurons, motor erroneous, relay neurons, synapses and effectors in simple reflex actions.

In a simple reflex action: impulses from a receptor pass along a sensory neurons to the central nervous system Subject Content at a Junction (synapse) between a sensory neurons and a relay neurons in the central nervous system, a chemical is released that causes an impulse to be sent along a relay neurons a chemical is then released at the synapse between a relay neurons and motor neurons in the central nervous system, causing impulses to be sent along a motor neurons to the organ (the effectors) that brings bout the response the effectors is either a muscle or a gland, a muscle responds by contracting and a gland responds by releasing (secreting) chemical substances. Bal . 2. 2 Control in the human body a) Internal conditions that are controlled include: Details of the action of the skin and kidneys and the control of blood sugar are not required. He water content of the body – water leaves the body via the lungs when we breathe out and via the skin when we sweat to cool us down, and excess water is lost via the kidneys in the urine the ion content of the body – ions are lost via the skin when we wheat and excess ions are lost via the kidneys in the urine temperature – to maintain the temperature at which enzymes work best blood sugar levels – to provide the cells with a constant supply of energy. B) Many processes within the body are coordinated by chemical substances called hormones. Hormones are secreted by glands and are usually transported to their target organs by the bloodstream. 15 c) Hormones regulate the functions of many organs and cells. For example, the monthly release of an egg from a woman’s ovaries and the changes in the thickness of the lining of her womb are controlled by hormones secreted by the pituitary gland ND by the ovaries. D) Several hormones are involved in the menstrual cycle of a woman.

Hormones are involved in promoting the release of an egg: follicle stimulating hormone (FISH) is secreted by the pituitary gland and causes eggs to mature in the ovaries. It also stimulates the ovaries to produce hormones including estrogen alternating hormone (LA) stimulates the release of eggs from the ovary estrogen is secreted by the ovaries and inhibits the further production of FISH. E) The uses of hormones in controlling fertility include: giving oral contraceptives that contain hormones to inhibit FISH production so that no eggs mature – oral contraceptives may contain estrogen and progesterone to inhibit egg maturation – the first birth-control pills contained large amounts of estrogen.

These resulted in women suffering significant side effects – birth-control pills now contain a much lower dose of estrogen, or are progesterone only – progesterone- only pills lead to fewer side effects Knowledge of the role of progesterone in the natural menstrual cycle, including details of negative feedback, is not required giving FISH and LA in a fertility drug to a woman whose own level of FISH is too low to template eggs to mature, for example in In Vitro Fertilization (IV) treatment – IV involves giving a mother FISH and LA to stimulate the maturation of several eggs. The eggs are collected from the mother and fertilized by sperm from the father. The fertilized eggs develop into embryos. At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother’s uterus (womb). 16 Bal . 2. Control in plants a) Plants are sensitive to light, moisture and gravity: their shoots grow towards light and against the force of gravity their roots grow towards moisture and in the direction of the force of gravity. Additional guidance: b) Plants produce hormones to coordinate and control growth. Again controls photocopies and gravitations (isotropic). C) The responses of plant roots and shoots to light, gravity and moisture are the result of unequal distribution of hormones, causing unequal growth rates. Candidates should enders tan the role tot again in photocopies and gravitations. D) Plant growth hormones are used in agriculture and horticulture as weed killers and as rooting hormones. Names of specific weed killers and rooting hormones are not required.