Transcript Life Comes From Life

Life Comes From Life
Notes 2.1c
Life Comes From Life
• Living things arise from living things
through reproduction.
• Today we know that flies come from flies.
• But 400 years ago, people believed that
life could appear from non-living material.
• For example, people thought flies came
from rotting meat.
Life Comes From Life
• The mistaken idea that living things can
arise from nonliving sources is called
spontaneous generation.
• It took hundreds of years of experiments to
convince people that spontaneous
generation does NOT OCCUR!
Redi’s Experiment
• Time: 1600s
• Scientist: Francesco Redi – Italian
• Redi designed an experiment to show that
flies do not arise from decaying meat.
• Remember: A controlled experiment is
when you carry out 2 experiments at the
same time with only 1 difference between
them.
Redi’s Experiment
• In Redi’s experiment, the manipulated
variable was whether or not to cover the
jar.
Redi’s Experiment
Pasteur’s Experiment
• Time: Mid 1800s
• Scientist: Louis Pasteur – French
• He demonstrated that new bacteria
appeared in broth only when they were
produced by existing bacteria.
Conclusions
• The experiments of Redi and Pasteur
helped to convince people that living
things do not arise from nonliving material.