Science

• Respiration


  A chemical reaction which occurs in each one of the cells in the human body. It releases energy stored food called glucose, and without it the cells would die.
• Aerobic respiration


  Slowly releases lots of energy stored in glucose. It occurs in the tiny parts of the cells called mitochondria which are found in cytoplasm.
• Aerobic respiration


  1. Glucose + Oxygen

  2. Carbon Dioxide + Water
• Gas exchange


  Oxygen in the air moves into the blood, and carbon dioxide in the blood moves into the air.
• Diffusion


  The particles in the air are gas, and they are moving around freely. The oxygen in the air moves from the air, through the thin-walled cells and into the blood.
• Formation of oxyhaemoglobin


  Oxygen moves into the blood, it dissolves and combines with the haemoglobin forming a compound called oxyhaemoglobin which is bright red in colour.
• Ventilation


  The process of breathing
• Inhalation


  Diaphragm muscle contracts and moves downwards, and the intercostal muscle contracts and moves the ribs upwards and outwards. This increases the volume of the lungs, which reduces pressure inside, and so air moves into the lungs to equalize it.
• Exhalation


  Diaphragm muscle relaxes and moves upwards, and the intercostal muscle relaxes and moves the ribs downwards and inwards. This reduces the volume of the lungs, which forces air outwards.
• Structure of air movement

  • Nose/mouth
  • Trachea (windpipe)
  • Bronchus
  • Bronchioles
  • Alveoli
  • Lungs
• Structure of air movement out

  • Lungs
  • Alveoli
  • Bronchioles
  • Bronchus
  • Trachea (windpipe)
  • Nose/mouth
• Plasma


  The liquid that makes up more than half of the blood in the human body. It is mainly made of water and is pale yellow. It carries all the platelets, rbc, wbc, dissolved glucose, dissolved salts, hormones, enzymes, and waste products like carbon dioxide.
• Red Blood Cells


  • They are the most numerous cells in the human body. In one drop of blood, there are around 3-5 million red blood cells. RBC are made in bone marrow. They do not contain a nucleus or a mitochondria to maximize the amount of oxygen they can carry. They have dips on both sides to maximize their surface area to absorb oxygen as quickly as possible. They do not contain a mitochondria because to stop them from using up all the oxygen for themselves instead of delivering it elsewhere.
• White Blood Cells


  • In a drop of blood, there are around 10,000-20,00 white blood cells, and even more if a person is ill. WBC form part of our immune system to keep us safe from infections and diseases. WBC are made in bone marrow. The 1st type of WBC are Phagocytes which form a finger-like structure when the Pathogen comes closer and engulfs it and kills it. The 2nd type of WBC are Antibodies which are Y-shaped and stick on to the Pathogen and kills it.
• Solute


  A substance that dissolves into a solvent, and is added in a small scale.
• Solvent


  A substance which a solute dissolves in, and is added in a large scale.
• Solution


  Always transparent. It can be coloured or colourless. E.g.- Sugar solution
• Solubility


  How soluble a substance is
• Increasing temperature increases solubility
• Independent variable


  The variable you change
• Dependent variable


  The variable you measure
• Control variable


  The variable you keep the same
• Chromatogram


  The resulting image on the paper after chromatography experiment
• Pencil should be used to draw the baseline on chromatography paper, not pen
• Types of solutions


  • Soluble
  • Insoluble
  • Concentrated
  • Dilute
  • Saturated
• Adaptations


  Features of organisms that help them to live and reproduce in their habitat
• Habitat


  The place where an organism naturally lives
• Non-living things in the desert that affect organisms

  • Light
  • Temperature
  • Soil
  • Water
  • Air
• Ecosystem


  A network of interactions between all the living organisms in a habitat, and all the non-living things around them
• Ecology


  The study of organisms in their natural habitat
• Native species


  Organisms that are living in their natural habitat
• Invasive species


  Species that have been introduced to the ecosystem where they do not belong
• Extinct


  No longer existing. E.g.- Dinosaurs
• Eradicate


  To destroy or completely get rid of a species
• Atoms


  Tiny particles of matter
• The word 'atoms' comes from a Greek word which means 'cannot be split'
• Sub-atomic particles of an atom and their charge

  • Protons - positive electrical charge
  • Neutrons - no electrical charge
  • Electrons - negative electrical charge
• Structure of an atom

  The protons and neutrons are packed into a dense nucleus at the centre and the electrons go around the nucleus
• Electrostatic attraction


  The force that holds individual atoms together
• J.J. Thompson's model of the atom

  Plum Pudding Model - The electrons were randomly scattered throughout the structure of the atom on top of positively charged matter