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INTRODUCTION TO BIOLOGY
How does life begin?
• There were 2 theories:
– Spontaneous generation
– Biogenesis
Spontaneous Generation
• Process by which life begins when ethers
enter nonliving things
• Francesco Redi conducted an experiment
to disprove this theory
Redi’s Experiment
• During Redi’s time maggots were
•
•
•
thought to come from rotting meat
Redi placed meat in an open jar and
maggots appeared on the meat
Redi placed meat in a closed jar and no
maggots appeared
Critics of Redi suggested that the ethers
could not enter the container which is
why the maggots did not appear
Redi’s Revised Experiment
• Redi placed meat in a jar covered
•
with a mesh cloth to allow ethers to
enter but nothing else
Maggots did not appear on the
meat
Biogenesis
• Principle that life comes only from life
• After Francesco Redi disproved the theory
of spontaneous generation, Louis Pasteur
conducted an experiment to prove
biogenesis
Pasteur’s Experiment
• Broth is placed in a flask with a
•
•
•
curved neck to prevent dust from
entering the broth
The broth is heated and after
one year, the broth was still free
of bacteria
The curved neck is broken off so
that dust can now enter the flask
After one day, the broth was
cloudy and filled with bacteria
Characteristics of Life
• Organization: living things are
organized; the basic unit of organization is
the cell
• Energy: living things use sound, light and
chemical energy; all living things take in
energy from the environment and use it
for their life processes
• Growth and Development:
– Growth is an increase in size
– Development is a change in shape or form
Characteristics of Life (cont.)
• Reproduction: process by which new
living things are formed
• Response and Adaptation:
– Response includes migration, movement,
color changes, etc.
– Adaptation is a way for an entire population
of organisms to respond to long-term changes
in their surroundings; these are passed on
from generation to generation
Levels of Organization
Atom
Molecule
Cell
Tissue
Organ
Organ System
Organism
Population
Community
Ecosystem
Biosphere
Population, Community, Ecosystem
& Biosphere
• Population: group of organisms of the
same species that live together in a
particular location
• Community: include all organism
populations in a particular location
• Ecosystem: all the communities and the
non-living parts in a particular location
• Biosphere: thin layer of air, land and
water on the surface of the earth