Some medicines, including painkillers, only help to relieve the symptoms of disease. Antibiotics, including penicillin, are medicines that help to cure bacterial disease by killing infectivebacteria. Viruses can only live and reproduce within the cells in the body. This makes it difficult to kill them without also damaging the body's tissues. People can be immunised against disease by introducing a mild, or dead, form of the infecting organism into their bodies. The white blood cells respond by producing antibodies that will help to defend the body against a future attack by the infective organism. This is called active immunity. Small gro
A Level Biology Edited by Gabriel Tambwe Week No Learning Outcomes Le If a person has been exposed to a dangerous infective organism, antibodies to combat the infection may be injected to give them immediate protection. This is called passive immunity. 24 2.11 Humans as Organisms - Drugs Solvents, alcohol, tobacco and other drugs may harm the body. Solvents : affect behaviour; may cause damage to the lungs, liver and brain. Tobacco smoke contains substances which can cause: lung cancer; other lung diseases such as emphysema; disease of the heart and blood vessels. Alcohol: affects the nervous system by slowing down reactions and may lead to lack of self-control, unconsciousness or even coma; may cause damage to the liver and brain. Drugs change the chemical processes in people's bodies so that they may become dependent or addicted to them and suffer withdrawal symptoms without them. 25 4.1 Variation, Inheritance & Evolution - Variation Young plants and animals resemble their parents (have similar characteristics) because of information passed on to them in the sex cells (gametes) from which they have developed. The information is carried by genes. Different genes control the development of different characteristics. Differences in the characteristics of different individuals of the same kind may be due to
A Level Biology Edited by Gabriel Tambwe Week No Learning Outcomes Le differences in: the genes they have inherited (genetic causes); the conditions in which they have developed (environmental causes); or a combination of both. New forms of genes result from changes (mutations) in existing genes. Mutations occur naturally. The chance of mutations occurring is increased by: exposure to ionising radiations, including ultra-violet light, X- rays and radiation from radioactive substances; the greater the dose of radiation, the greater the chance of mutation; certain chemicals. There are two forms of reproduction: sexual reproduction - which involves the joining (fusion) of male and female gametes; asexual reproduction - where there is no fusion of cells and only one individual is needed for it to take place.
- Summer '17
- Jack Chenda
- Bacteria, Gabriel Tambwe