Life

• Life


  A complex system of processes that distinguishes living organisms from non-living matter
• Life


  • Results from the coupled cycling of elements in an aqueous solution, ultimately driven by radiant energy to attain maximum complexity
• Characteristics of life

  • Organization
  • Homeostasis
  • Metabolism
  • Reproduction
  • Growth and Development
  • Response to Stimuli
  • Evolution
• Organization

  According to the Modern Cell Theory, all living things are made of cells
• Unicellular


  • Has one cell
• Multicellular


  • Has multiple cells (these cells can be arranged into tissues that make up organs that can be part of an organ system = biological levels of organization)
• Homeostasis


  Living things maintain a relatively stable internal environment despite external conditions
• Homeostasis


  • Maintaining a certain pH range for enzymes to work correctly
  • Maintaining a certain temperature and water concentration
• Feedback systems


  In place to maintain homeostasis
• Metabolism


  Life involves intricate chemical processes, from metabolism to cellular reactions
• Metabolism


  A way to capture energy and use it for processes (including the process to keep homeostasis)
• Autotrophs (Plants)


  • Can capture light energy to make glucose in a process known as photosynthesis
• Heterotrophs (Animals)


  • Typically need to eat something and then digest it in order to obtain glucose
• Both autotrophs and heterotrophs

  Break down glucose in cellular respiration to make ATP energy
• Reproduction

  Living things are capable of reproducing
• Reproduction


  • Unicellular bacteria can copy DNA and split into two
  • For most animals, it involves sperm and egg cells uniting to make a fertilized egg (zygote) which will eventually develop into a baby
• Growth and Development

  Living organisms have the genetic material to code for its development and growth
• Growth and Development


  • A baby pony will grow up and develop into a grown-up pony because its genetic materials contain the instructions for this development and growth
• Response to Stimuli

  Living things detect changes in their surroundings and respond to them
• Internal Stimuli


  • If a living thing feels the need to eat, this can be due to the coordination of body systems internally alerting it that it is hungry
• External Stimuli


  • If a living thing senses danger, its external stimulus may cause it to flee
• Responses to stimuli may not be obvious, e.g. plants responding to light
• Evolution


  Life is a self-sustaining system capable of Darwinian evolution
• Evolution


  • Occurs over a period of time
  • Acts on populations
  • The gene frequencies in a population of living organisms can change over time due to mechanisms (e.g. natural selection)
  • Some genes can code for certain traits that result in higher reproductive fitness, while some genes may code for traits that lower reproductive fitness (both in one particular environment)
  • Can result in adaptation