Life From Life Biogenesis The First Cells Cell

Life From Life üBiogenesis üThe First Cells üCell Theory üCells and Technology

What is Life? There are 5 main characteristics that scientists have decided are present in living things They are…

1. Living things need energy

2. Living things produce wastes

3. Living things respond adapt to their environment

4. Living things reproduce

5. Living things grow

Abiogenesis or Biogenesis? pg. 258 - 259 Abiogenesis – believed for 2000 years – living things can appear from non-living things Controlled experiments disproved abiogenesis and led to new theory – BIOGENESIS

Francesco Redi (1668) Placed meat in an uncovered jars Placed meat in jars covered with cheesecloth (air but not flies could pass through) A few days later…….

Maggots were found in uncovered jars only! Redi was convinced that maggots are not reproduced by abiogenesis.

Although Abiogenesis was disproved, scientists still did not know how new forms of life appeared.

LOUIS PASTEUR 1822 - 1895 Investigated FERMENTATION, a process that converts grape juice to wine, barley to beer, sours milk. He hypothesized that the “active principle” in the air that caused this convention was an organism.

Pasteur’s Experiment • HYPOTHESIS: air itself is the “active principle” because it contains microbes. TEST: exclude air from nutrient broth and it will not teem with life.

Redi and Pasteur attempt to disprove abiogenesis http: //www. sumanasinc. com/webcontent/anima tions/content/scientificmethod. html

Rudolf Virchow German physicist suggested theory of BIOGENESIS in 1858 BIOGENESIS = LIVING ORGANISMS CAN ONLY ARISE FROM OTHER LIVING ORGANISMS

Robert Hooke, Microscopes and the Cell Theory

Microscopes and the Cell Theory pg. 261 - 265 Robert Hooke 1665 – saw cork “boxes” which reminded him of monk cells so he called them “cells” However, it was decades before scientists realized that cells were an amazing discovery and were common to all living things!

More Discoveries Anthony van Leeuwenhoek builds a microscope that could magnify up to 500 X and becomes the first person to describe single-celled microorganisms.

More Discoveries Schleiden and Schwann determine that plants and animals were composed of cells but they still believed in abiogenesis.

More Discoveries Virchow concludes that cells can only arise from other cells and the cell theory is born. Virchow concludes that cells can only arise from other cells.

Current Cell Theory All organisms are composed of one or more cells The cell is the smallest functional unit of life All cells are produced from other cells

Microscopes pg. 266 - 268 Complete your notes using your textbook