Transcript Life From Life - Rocky View Schools

Biogenesis
The First Cells
Cell Theory
Cells and Technology
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.
 http://www.sumanasinc.com/webcontent/animations
/content/scientificmethod.html
Rudolf Virchow
 German physicist suggested the theory of
BIOGENESIS in 1858
 BIOGENESIS = LIVING ORGANISMS CAN ONLY
ARISE FROM OTHER LIVING ORGANISMS
Robert Hooke, Leeuwenhoek,
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 500X and becomes the
first person to describe single-celled
microorganisms.
More Discoveries
 Schleiden and Schwann: all plants and
animals were composed of cells
 Every cell has a nucleus so the nucleus
identifies the presence of a cell.
 but they still
believed in
abiogenesis.
More Discoveries
 Virchow sees cells dividing under the microscope,
and finds that bone cells develop from cartilage
cells. He concludes that cells can only arise from
other cells and the cell theory is born.
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
ASSIGNMENT:
 1. Fill in 3 variables and conclusion for Redi’s and
Pasteur’s experiments in your notes.
 Go to www.cellsalive.com/howbig.htm and check out
the huge range in cell sizes. Check out plant and
animal cells at
http://www.cellsalive.com/cells/3dcell.htm ! Make
sure you know what a cell membrane, nucleus,
cytoplasm and chloroplasts do, and what they look
like!
 Go to google images to see what lettuce cells and
cheek cells look like under the microscope.
 Do vocab 8-17