MICROSCOPE AS BIOLOGY- A LEVELS CAMBRIDGE

1. Biogenesis
The First Cells
Cell Theory
Cells and Technology

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

3. 1. Living things need energy

4. 2. Living things produce wastes

5. 3. Living things respond and
adapt to their environment

6. 4. Living things reproduce

7. 5. Living things grow

8. 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

9. 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…….

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

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

12. 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.

13. 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.

15. Redi and Pasteur attempt
to disprove abiogenesis
 http://www.sumanasinc.com/webcontent/animat
ions/content/scientificmethod.html

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

17. Robert Hooke, Microscopes and
the Cell Theory

18. 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!

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

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

21. 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.

22. 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

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