genbio1

• Biology


  The science of life and living organisms
• The word biology is derived from the Greek words: bios, meaning life, and logos, meaning study
• Spontaneous generation


  The hypothetical process by which living organisms develop from nonliving matter
• For much of history, people believed that animals could come from non-living sources
• Beliefs about spontaneous generation

  • Frogs developed from falling drops of rain
  • Mice arose from sweaty underwear
  • Flies arose from decaying meat
• Abiogenesis


  Also known as spontaneous generation
• Authorities

  • People believed what they were told by "authorities" such as the Church, or the ancient Greek philosopher Aristotle
  • Many people believed this idea since they simply accepted what they were told, specifically by the authorities
• Aristotle


  A Greek philosopher who first proposed that life could arise from non-living matter if the material contained "pneuma" or vital heat
• Jan Baptista van Helmont


  A Flemish scientist that put forth the idea that mice could appear out from wheat kernels and rags left out in an open container for 3 weeks
• Recipe for mice


  1. Put a soiled shirt and grains of wheat in a jar and let them ferment

  2. Mice form after 21 days
• Francisco Redi


  Italian physician & poet who attempted to disprove the theory of spontaneous generation
• Redi's experiment

  1. Involved two jars and decaying meat: one with a wax seal and the other left in the open

  2. Wax sealed vessels failed to produce maggots whereas decaying meat left in the open were full of them
• Redi concluded "The flesh of dead animals cannot engender worms unless the eggs of the living being deposited therein."
• Redi's critics said


  • You have too many variables
  • There is a lack of access and a lack of air
  • We ALL know that everything needs air
  • Of course no flies grew!
  • You haven't proven anything
• Redi's 2nd experiment


  1. He covered the jars with fine mesh

  2. Flies laid eggs on the mesh and no maggots were able to reach the meat
• Redi concluded "All living beings come from seeds of the plants or animals themselves."
• John Needham


  English Clergyman who wondered whether the idea of spontaneous generation applied to microbes
• Needham's experiment

  1. Prepared various broths and showed that they contained microbes

  2. Boiled them and showed that there were no longer any microbes

  3. Ensured the stoppers were loose, so that air would not be excluded

  4. After a few days, microbes had reappeared
• Needham concluded that microbes spontaneously generated from the non-living broth
• Needham's error was that microbes could have come from the air
• Lazzaro Spallanzani


  Italian Naturalist who rejected Needham's conclusions
• Spallanzani's experiment

  1. Repeated Needham's experiment but boiled the broth a little longer and sealed it shut (hermetically sealed – absolutely airtight)

  2. No growth of microbes was seen
• Needham criticized Spallanzani's experiment

  • You boiled it TOO LONG
  • You spoiled the vegetative power by boiling
  • You killed the ability of the broth to give life
  • Life can still come from broth - but the broth must not be "damaged" by boiling
• Spallanzani's 2nd experiment


  1. Did time boilings and left some jars, as Needham had, with leaky seals to ensure "active principle" was not damaged

  2. Boiling did not damage the broth's ability to support life. Growth depended on the seal only
• Louis Pasteur


  French chemist who entered a contest sponsored by French Academy of Sciences to prove or disprove Spontaneous generation
• Pasteur's experiment

  1. Used swan-necked flasks, which allowed the entry of air but trapped microbes along its neck

  2. Showed no growth after many days

  3. Pasteur showed that the active principle was not damaged. At any later time, he could tip the flask, this allowed nutrient broth to contact the dust and carry microbes into the broth
• Cell theory


  The development and refinement of magnifying lenses and light microscopes made observation and description of microscopic organisms and living cells possible
• Hans and Zacharias Janssen


  Invented the first compound microscope when they put two of their lenses together in a tube
• Robert Hooke


  Discovered and came up with the name "cells" while looking through a microscope at a piece of cork
• Anton van Leeuwenhoek


  Observed some of the first living cells under a simple microscope and named these small organisms "animalcules"
• Robert Brown


  Discovered the nucleus in the plant cells of an orchid
• Matthias Jakob Schleiden


  A German botanist who concluded that all plant tissues are composed of cells
• Theodore Schwann


  Viewed animal tissues under a microscope and observed that animal tissues are made of cells. Proposed the two tenets of the cell theory: 1) All organisms are composed of one or more cells, 2) The cell is the structural unit of life
• Rudolph Virchow


  Collaborated with the other two scientists and developed cell theory. He made the third tenet of the cell theory: "All cells come from pre-existing cells."
• Three main principles of cell theory


  • All living organisms are made up of cells
  • Cells are the most basic unit of life
  • All cells arise from pre-existing cells
• Compound light microscopes

  Use glass lenses like the early microscopes Robert Hooke used
• Modern compound light microscope


  Uses electricity, a source of light, and can magnify images up to 1000x without blurring
• Transmission electron microscope (TEM) and the scanning electron microscope (SEM)

  Can magnify specimens up to 500,000x
• Basic properties of cells

  • Highly complex and organized
  • Possess a genetic program and the means to use it
  • Capable of producing more of themselves
  • Acquire and utilize energy
  • Carry out a variety of chemical reactions
  • Engage in mechanical activities
  • Able to respond to stimuli
  • Capable of self-regulation (Apoptosis is the death of cells)
  • Evolve
• Basic types of cells

  • Eukaryotes
  • Prokaryotes