biology (C1 - C3)

• Characteristics of living things (organisms)

  • Movement
  • Respiration
  • Sensitivity
  • Growth
  • Reproduction
  • Excretion
  • Nutrition
• Acronym for characteristics of living things

  MRS GREN
• Non-living things may have some of these features, but only living things have all seven
• Movement

  Ability of organisms to move, either the whole organism or just part of it
• Respiration

  Chemical reactions that take place in cells to break down nutrients and release energy for metabolism
• Sensitivity

  Ability to detect and respond to changes in the internal or external environment
• Growth

  Permanent increase in size and dry mass of an organism
• Reproduction

  Process that makes more of the same kind of organism
• Excretion

  Removal of waste products of metabolism and substances in excess of requirements
• Nutrition

  Taking in of materials for energy, growth and development
• All living organisms are made up of one or more cells
• Viruses are not considered living organisms because they do not meet all seven characteristics
• Organ system


  A number of organs connected to perform a particular function
• Organ systems in the body


  • Digestive system
  • Respiratory system
  • Circulatory system
  • Skeletal system
  • Nervous system
• Digestive system


  • Stomach, pancreas, small intestine, large intestine
  • Breaks down food into smaller units called nutrients
  • Nutrients are absorbed into the blood
• Respiratory system


  • Airway, lungs, muscles of respiration
  • Helps in respiration or breathing
  • Brings oxygen into the body and removes carbon dioxide
• Circulatory system


  • Heart, arteries, veins, blood
  • Carries blood to all parts of the body
• Skeletal system


  • Bones
  • Gives shape and support to the body
  • Protects internal organs
  • Allows movement
• Nervous system


  • Brain, spinal cord, nerves
  • Receives messages from sense organs and other parts of the body
  • Sends orders for action
• Cell


  The basic unit of life
• Some living organisms such as animals and plants are made of hundreds of trillions of these basic units of life called cells
• Animal cell


  • Nucleus
  • Cell membrane
  • Cell cytoplasm
• Nucleus


  Structure that contains the genetic information (DNA) and controls the actions and reactions of the cell
• Cell membrane


  Border of the cell that acts as the gatekeeper and controls what enters and exits the cell, and enables neighbouring cells to stick to one another
• Cell cytoplasm


  Site of the cell's chemical reactions, including respiration which takes place in specialised structures called mitochondria
• Plant cell


  • Nucleus
  • Cytoplasm
  • Cell membrane
  • Cell wall
  • Chloroplasts
  • Vacuoles
• Cell wall


  Made of cellulose, provides support for the shape of the cell
• Chloroplasts


  Filled with chlorophyll, enable plant cells to absorb light for photosynthesis
• Vacuoles


  Filled with a watery substance containing dissolved sugars (cell sap), provide support for cell shape and store sugars
• Specialised cells


  • Red blood cells
  • Nerve cells
  • White blood cells
• Red blood cells


  Do not possess a nucleus, so they can absorb and transport as much oxygen as possible
• Nerve cells


  Have branched endings called dendrites to communicate with other nerve cells, and long axons along which electrical messages can travel
• White blood cells


  Enable us to fight infections, have a flexible cytoplasm to engulf pathogens (phagocytosis), and some produce antibodies to fight pathogens
• Over 60 percent of life on earth is so small that it can only be seen with a microscope
• These small things are called microbes or microorganisms
• There is estimated to be about two to three billion different species of these little microbes
• Microbes generate oxygen in the atmosphere and fix nitrogen in our soils so that plants can grow, forming the base of our food chains
• Main groups of microorganisms

  • Fungi
  • Bacteria
  • Viruses
  • Algae
• Fungi


  • Include mushrooms, yeasts, and molds
  • Some are beneficial (e.g. for bread and alcohol fermentation)
  • Some cause diseases
• Bacteria


  • Some are harmful, but many are extremely beneficial
  • We have about 100 billion bacterial cells living on our skin alone
  • Help boost our immune system and aid digestion
  • Used in making cheese, yogurt, and biogas