THEORIES OF LIFE
Leonor Redondo
The first one that was developed although it obviously is not based in science, at first
people believed that we were created by a god or gods.
SPONTANEOUS GENERATION:
It is an obsolete theory that explains that life started or came from inorganic
organisms.
ARISTOTLE’S ACTIVE PRINCIPLE RESPONSIBLE FOR LIFE:
Aristotle believed that there was an "active principle" that gave life to living beings.
This active principle was based on the 4 basic elements for life according to Aristotle.
All the matter comes from the 4 basic elements: Fire, Water, Earth and Air.
People began to question the idea of spontaneous generation and some scientists did
experiments to discover if this theory was true. Finally they discovered other theories
that replaced the theory of spontaneous generation.
Experiments that proved this theory was incorrect:
REDI’S EXPERIMENT
Francesco Redi conducted an experiment in which he placed meat in jars, some open
and others sealed by a lid. Maggots only appeared in the open jars, but some critics
argued that the lid prevented air from passing through, which they believed was
necessary for spontaneous generation. Redi repeated the experiment, this time
covering the jars with gauze which allowed air to pass through but still prevented flies
from laying eggs on the meat, and it happened the same so finally the theory of
spontaneous generation was disproved.
PASTEUR’S EXPERIMENT
Pasteur used flasks of meat broth, boiling them to kill any microorganisms. Some
flasks were left open and others with a swan's neck, which allowed air to pass through
, but kept out dust and microorganisms. While bacteria grew in the open flasks, in the
swan's neck flasks did not, proving that the microorganisms came from the
environment and not from the broth. This experiment finally ends with the theory
of spontaneous generation. Eliminated free cell formation
theories that replaced some principles of spontaneous generation→
CELL THEORY:
The principles of cell theory:
- All living organisms are made up of one or more cells.
- The cell is the smallest unit that performs vital functions.
- All cells come from other pre-existing cells.
- The cell contains the genetic material (DNA)
- The essential functions of organisms take place within cells.
There were many scientists that contributed to his theory:
- Francesco Redis: His experiment
- Zacharias Janssen: He created the first microscope, which allowed the
observation of cells and smaller organisms.
- Anton van Leeuwenhoek: He created his own microscope and by observing
dental tartar he was the first to record the existence of microorganisms which
he called animalcules.
- Robert Hooke: He coined the term cell. He called them that because when
he observed them they reminded him of the cells of monks.
- Matthias Schleiden: He proposed that plants are made of cells.
- Theodor Schwann: He proposed that animals are made of cells.
Leonor Redondo
The first one that was developed although it obviously is not based in science, at first
people believed that we were created by a god or gods.
SPONTANEOUS GENERATION:
It is an obsolete theory that explains that life started or came from inorganic
organisms.
ARISTOTLE’S ACTIVE PRINCIPLE RESPONSIBLE FOR LIFE:
Aristotle believed that there was an "active principle" that gave life to living beings.
This active principle was based on the 4 basic elements for life according to Aristotle.
All the matter comes from the 4 basic elements: Fire, Water, Earth and Air.
People began to question the idea of spontaneous generation and some scientists did
experiments to discover if this theory was true. Finally they discovered other theories
that replaced the theory of spontaneous generation.
Experiments that proved this theory was incorrect:
REDI’S EXPERIMENT
Francesco Redi conducted an experiment in which he placed meat in jars, some open
and others sealed by a lid. Maggots only appeared in the open jars, but some critics
argued that the lid prevented air from passing through, which they believed was
necessary for spontaneous generation. Redi repeated the experiment, this time
covering the jars with gauze which allowed air to pass through but still prevented flies
from laying eggs on the meat, and it happened the same so finally the theory of
spontaneous generation was disproved.
PASTEUR’S EXPERIMENT
Pasteur used flasks of meat broth, boiling them to kill any microorganisms. Some
flasks were left open and others with a swan's neck, which allowed air to pass through
, but kept out dust and microorganisms. While bacteria grew in the open flasks, in the
swan's neck flasks did not, proving that the microorganisms came from the
environment and not from the broth. This experiment finally ends with the theory
of spontaneous generation. Eliminated free cell formation
theories that replaced some principles of spontaneous generation→
CELL THEORY:
The principles of cell theory:
- All living organisms are made up of one or more cells.
- The cell is the smallest unit that performs vital functions.
- All cells come from other pre-existing cells.
- The cell contains the genetic material (DNA)
- The essential functions of organisms take place within cells.
There were many scientists that contributed to his theory:
- Francesco Redis: His experiment
- Zacharias Janssen: He created the first microscope, which allowed the
observation of cells and smaller organisms.
- Anton van Leeuwenhoek: He created his own microscope and by observing
dental tartar he was the first to record the existence of microorganisms which
he called animalcules.
- Robert Hooke: He coined the term cell. He called them that because when
he observed them they reminded him of the cells of monks.
- Matthias Schleiden: He proposed that plants are made of cells.
- Theodor Schwann: He proposed that animals are made of cells.
