Life and Its Beginning
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an idea that life could appear from non-living matter or inanimate object.
Spontaneous generation or abiogenesis
abiogenesis is proposed by who and contradicted by who?
proposed by Aristotle and contradicted by Francesco Redi
is the belief that life originates from pre-existing life
Biogenesis
spontaneous generation is disproved by whose experiments?
it is disproved by Redi and Pasteur’s experiments
explain Francesco Redi’s experiment
disproved abiogenesis using maggots that arose in decaying meat (maggots in meat in open container; no maggots in sealed containers)
tested whether or not microorganisms can appear spontaneously after boiling
John Needham (Needham’s Experiment)
English scientist that tried to disprove spontaneous generation
John Needham
explain Needham’s experiment:
sealed a bottle of gravy, then heated it to kill any life; found life several days later, which he claimed came from the gravy. FLAW w/ his experiment: the flask was not sealed and was exposed to air
stated that life occurred from something that entered the unsealed flask and that it was the one responsible for life to grow
Lazzaro Spallanzani
disproved Needham’s experiment
Spallanzani’s Experiment
explain Spallanzani’s experiment:
used the same method as Needham’s but used two containers (one unsealed, and one sealed) using broth in flasks that were both heated, he waited for growth. no growth in sealed flask, growth in unsealed flask.
suggests that new bacteria appear only when they are produced by existing bacteria
Louis Pasteur
explain Pasteur’s experiment:
using control and experimental groups he checked for cell growth. in the control group no growth was observed because it is sealed; while in the experimental group where neck is broken, outside air can carry microorganism leading to cell growth.
Pasteur’s conclusion:
cells can only arise from pre-existing cells
Early beliefs about the Origin of life
• Divine creation • Spontaneous origin • Panspermia • Electric spark theory • Deep-sea vent theory • Physio-chemico theory
it is believed that life forms and everything in the universe were created through a super natural power rather than naturalistic mean
Divine creation
life evolved from inanimate matter; before life could evolve, simple molecules combined to form complex molecules
Spontaneous origin
life arose outside earth and life that forms were transported from another planet to seed life on earth
Panspermia
it proposes that a meteor or cosmic dust may have carried to earth significant amount of organic molecules which started the evolution of life
Panspermia
life originated from chemical substances through a gradual process of change under the influence of reducing atmosphere (absence of free molecular oxygen in the primitive earth)
Physico-chemico theory
lightning may have provided the spark needed for life to begin
Electric spark theory
can generate amino acids and sugars from an atmosphere loaded with water, methane, ammonia, and hydrogen
Electric spark theory
suggests that life may have begun at a submarine hydrothermal vents spewing key hydrogen-rich molecules
Deep-sea vent theory
their rocky nooks could then have concentrated these molecules together and provided mineral catalysts for critical reaction
Deep-sea vent theory