Biology Unit 1

• A combination of a balanced diet and regular exercise is needed to help keep the body healthy
• Our bodies provide an excellent environment for many microbes which can make us ill once they are inside us
• Our bodies need to stop most microbes getting in and deal with any microbes which do get in
• Vaccination can be used to prevent infection
• Healthy diet


  Contains the right balance of the different foods you need and the right amount of energy
• Nutrients in a healthy diet


  • Carbohydrates
  • Fats
  • Proteins
  • Mineral ions
  • Vitamins
• Malnourished


  Diet is not balanced, may lead to being overweight or underweight, deficiency diseases or conditions such as Type 2 diabetes
• Weight loss


  Energy content of food taken in is less than the amount of energy expended by the body
• Exercise


  Increases the amount of energy expended by the body
• Inherited factors affect health, e.g. cholesterol level
• People who exercise regularly are usually healthier than people who take little exercise
• Pathogens


  Microorganisms that cause infectious disease
• 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
• Immunity


  The immune system produces specific antibodies to kill a particular pathogen, if a large proportion of the population is immune the spread of the pathogen is reduced
• Semmelweis recognised the importance of hand-washing in preventing the spread of infectious diseases
• Medicines


  Some help to relieve symptoms of infectious disease but do not kill pathogens, others (antibiotics) help to cure bacterial disease by killing infectious bacteria
• Antibiotics cannot be used to kill viral pathogens
• Overuse and inappropriate use of antibiotics has increased the rate of development of antibiotic resistant strains of bacteria
• Mutations of pathogens produce new strains, antibiotics and vaccinations may no longer be effective against a new resistant strain
• The development of antibiotic-resistant strains of bacteria necessitates the development of new antibiotics
• MMR vaccine is used to protect children against measles, mumps and rubella
• Sterile technique for investigating microorganisms


  1. Petri dishes and culture media must be sterilised before use

  2. Inoculating loops must be sterilised by passing through a flame

  3. Petri dish lid secured with adhesive tape to prevent air contamination
• In school and college laboratories, cultures should be incubated at a maximum temperature of 25 °C
• In industrial conditions higher temperatures can produce more rapid growth
• The nervous system enables humans to react to their surroundings and coordinate their behaviour
• Receptors and the stimuli they detect


  • Receptors in eyes sensitive to light
  • Receptors in ears sensitive to sound
  • Receptors in ears sensitive to changes in position
  • Receptors on tongue and nose sensitive to chemicals
  • Receptors in skin sensitive to touch, pressure, pain and temperature changes
• Light receptor cells


  Have a nucleus, cytoplasm and cell membrane like most animal cells
• Simple reflex action


  1. Impulses from receptor pass along sensory neurone to central nervous system

  2. At synapse between sensory and relay neurone, chemical released causes impulse along relay neurone

  3. Chemical released at synapse between relay and motor neurone causes impulse along motor neurone to effector

  4. Effector is muscle or gland, muscle contracts or gland secretes
• Hormones


  Chemical substances secreted by glands and transported in bloodstream to regulate functions of organs and cells
• Hormones involved in menstrual cycle


  1. Follicle stimulating hormone (FSH) secreted by pituitary gland causes egg maturation and stimulates ovaries to produce oestrogen

  2. Luteinising hormone (LH) stimulates release of eggs from ovary

  3. Oestrogen secreted by ovaries inhibits further FSH production
• Uses of hormones in controlling fertility


  • Oral contraceptives containing oestrogen and progesterone to inhibit egg maturation
  • Fertility drugs containing FSH and LH to stimulate egg maturation for IVF
• Plant responses


  Shoots grow towards light and against gravity, roots grow towards moisture and in direction of gravity
• Plant hormones


  Auxin controls phototropism and gravitropism
• Plant growth hormones are used in agriculture and horticulture as weed killers and as rooting hormones
• Scientists are continually developing new drugs
• Testing new medical drugs


  1. Tested in laboratory using cells, tissues and live animals

  2. Tested in clinical trials with healthy volunteers and patients, starting with very low doses
• Effects of misuse of legal recreational drugs

  Alcohol and nicotine may have adverse effects
• Drug dependence and addiction


  Drugs change chemical processes so people become dependent or addicted and suffer withdrawal symptoms without them
• Organisms are well adapted to survive in their normal environments
• Drugs (including alcohol and heroin) may have adverse effects on the heart and circulatory system