Biology Y8

• Substances needed


  • Carbohydrates
  • Proteins
  • Fats and oils (lipids)
  • Vitamins
  • Minerals
• Nutrients


  Substances that provide the raw materials for making other substances that the body needs
• Tests to find substances in foods

  • Starch makes iodine solution go blue-black
• Nutrition information labels


  • Tell us what the food contains
  • Give the amount of energy in kilojoules (kJ)
  • Indicate the amount of energy more active people need
• Eating too much


  Can lead to malnutrition, heart disease, and cancer
• People starve


  Can lead to malnutrition and deficiency diseases like scurvy
• Digestive system


  • Organs help speed up digestion
  • Digestive juices contain enzymes that break down food
• Digestion


  1. Pulling food into the mouth (ingestion)

  2. Saliva breaks down starch

  3. Food is swallowed down the esophagus

  4. More digestive juices are added in the small intestine to break down carbohydrates, proteins, and lipids

  5. Digested soluble food is absorbed into the blood

  6. Undigested food is removed as waste
• Small intestine


  • Wall is folded and covered with villi to increase surface area
  • Wall is one-cell thick to allow easy diffusion of small molecules into the blood
  • Digested food molecules are carried in the blood plasma
• The surface area is the total area of the faces of a three-dimensional object
• Plant kingdom


  Organisms that have green leaves, cell walls made of cellulose and can photosynthesise
• Genus


  Second last group in the classification of organisms
• Species


  Last group in the classification of organisms
• Scientific name


  Two-word name used to identify each species
• Biodiversity


  The range of species in an area
• We should preserve biodiversity because organisms depend on one another, we won't be able to make use of organisms if they become extinct, and more biodiverse areas recover better from natural disasters
• Sexual reproduction


  Reproduction that needs two parents to produce sex cells or gametes which fuse to produce a fertilised egg cell or zygote
• Sexual reproduction in plants

  1. Gametes produced by reproductive organs

  2. Pollen grains carried by insects (pollination)

  3. Pollen grain grows pollen tube to egg cell

  4. Nucleus from male gamete joins with nucleus of egg cell to form zygote

  5. Zygote grows into embryo and ovule becomes a seed
• Flowers


  • Brightly coloured and scented petals to attract insects
  • Rough pollen grains that can stick to insect's body
  • Sticky stigma to collect pollen from insect
  • Nectary produces sugary nectar to attract insects
• Seed dispersal


  Fruits are used to disperse seeds, preventing new plants competing with parent plants
• Seed dispersal methods


  • Eaten by animals and seeds come out in faeces
  • Carried on animal fur
  • Carried by the wind
  • Exploded and scattered
• Seed germination


  Requires water, oxygen and warmth (WOW) to start chemical reactions, break down food store and allow cells to swell
• Seed germination


  1. Root grows first

  2. Shoot grows

  3. New leaves open and photosynthesis can start
• A growing plant needs light, air, water, warmth and nutrients called mineral salts (LAWWN)
• Asexual reproduction


  One parent plant produces offspring (e.g. using runners or tubers)
• Sampling


  Taking a small sample of a larger population to estimate what the larger population is like
• Quadrat


  • Used to take samples of plant populations to estimate the larger population
  • More samples taken, the more accurate the estimate but the longer it takes
• Aerobic respiration


  Series of chemical reactions that can be summarised as glucose + oxygen -> carbon dioxide + water, releasing energy
• Anaerobic respiration


  Does not require oxygen, used to release energy from glucose when more energy is needed than can be supplied by aerobic respiration
• Anaerobic respiration


  Causes muscles to tire quickly, releases less energy than aerobic respiration
• EPOC (excess post-exercise oxygen consumption)


  Extra oxygen needed after strenuous exercise to replace oxygen lost and provide oxygen for increased aerobic respiration
• Gas exchange


  Swapping one gas for another
• Organs used for gas exchange

  • Gills (fish)
  • Skin (frogs)
  • Stomata in leaves (plants)
  • Lungs (humans)
• Breathing


  1. Diaphragm contracts and moves downwards, rib muscles contract and lift ribs up and outwards (inhalation)

  2. Diaphragm relaxes and moves upwards, rib muscles relax and move ribs down and inwards (exhalation)
• During exercise


  Breathing rate and pulse rate increase
• Organs used for gas exchange

  • Gills (e.g. fish)
  • Skin (e.g. frogs)
  • Stomata in leaves (plants)
  • Lungs
• Ventilation and breathing


  1. Breathing in (inhalation)

  2. Breathing out (exhalation)
• When you exercise, your breathing rate (number of breaths per minute) and your pulse rate (number of times your heart beats per minute) increase
• This is because your cells need more oxygen and glucose for respiration
• Breathing


  The movement of the diaphragm and attached ribs that changes the volume of the chest