the study of life

• Biology


  The study of plants or any living organism
• What biology is the study of

  • Cells - structure or functions
  • The human body
  • Ecology
  • Life in general
  • Geo science related
• Cells


  The smallest unit of life, all living things are composed of cells or cell product
• Functions of life (MR SHENG)

  • Metabolism - undertake essential chemical reactions
  • Reproduction - produce offspring, either sexually or asexually
  • Sensitivity - respond to internal and external stimuli
  • Homeostasis - maintain a stable internal environment
  • Excretion - removal of waste products
  • Nutrition - exchange materials with the environment and obtain energy
  • Growth - move & change shape or size
• Water composition


  2 hydrogen atoms bonded to 1 oxygen atom (H2O)
• Covalent bonding


  Unequal sharing of electrons, creating polarity
• Water's polarity


  Leads to weak associations like hydrogen bonds
• Hydrogen bonds


  Give water unique physical, cohesive/adhesive, and solvent properties
• Surface Area to Volume Ratio


  Cells require chemical energy through metabolism and material exchange with the environment, which is linked to surface area and volume respectively. Growing cells aim to maintain a high surface area to volume ratio for optimal survival.
• Specialised cells


  • Increase surface area for efficient material transfer (e.g., intestinal tissue with villi and microvilli)
• Small animals


  Have a high surface area relative to volume, losing heat rapidly and requiring more energy
• Large animals


  Have a progressively smaller surface area compared to volume, losing less heat and needing less food
• Light Microscopes


  Used to look at cells
• Electron Microscopes (EM)


  Used to look at cells
• Transmission EM


  • Uses transmitted electrons (electrons that are passing through the sample) to create an image
• Scanning EM


  • Creates an image by detecting reflected or knocked-off electrons
• Advantages of Light Microscopes

  • Cheap
  • Portable
  • Produces colour images
  • Different stains can be used to highlights different features
  • Can sometimes use live materials
• Disadvantages of Light Microscopes

  • Material has to be transparent (thin or sliced into thin sections
  • Low resolution
  • Maximum magnification is 1000X to 1500X
• Advantages of Electron Microscopes

  • High resolution
  • High magnifications (x200 000)
  • SEM can produce 3D images
• Disadvantages of Electron Microscopes


  • Expensive equipment
  • Large equipment
  • Requires highly toxic chemicals for processing
  • Time consuming & requires skill
  • Produces B&W images
  • Materials must be dead
• Magnification


  Calculation: Image size (with rule) / Actual size (according to scale bar)
• Actual size


  Calculation: Image size (with ruler) / Magnification