Evolution & Origin of Life: Theories, Experiments & Evidence
Evolution & Origin of Life
Early Experiments & Theories
Redi’s Experiment
Francesco Redi investigated the spontaneous generation of maggots by placing meat in three jars: one open, one covered with fabric, and one sealed. Maggots only appeared in the open and fabric-covered jars, suggesting they arose from flies, not spontaneously.
Pasteur’s Experiment
Louis Pasteur further disproved spontaneous generation by using swan-neck flasks containing sterilized broth. The broth only decomposed when exposed to air, demonstrating that microorganisms caused decomposition, not spontaneous generation.
Oparin’s Theory & Miller’s Experiment
Oparin proposed that life arose from a “primordial soup” of organic molecules formed in Earth’s early atmosphere. Miller’s experiment supported this by simulating early conditions and producing amino acids, the building blocks of life.
Panspermia Theory
This theory suggests life or its building blocks arrived on Earth from outer space.
The Present Day Hypothesis
One hypothesis suggests life originated near deep-sea hydrothermal vents, where inorganic matter and energy could have formed organic molecules.
Evolutionary Theories
Fixism
Fixism, supported by Georges Cuvier, held that species are unchanging and were created as they are.
Lamarckism
Jean-Baptiste Lamarck proposed the inheritance of acquired traits, where organisms develop characteristics in response to their environment and pass them on to offspring.
Darwinism
Charles Darwin’s theory of evolution by natural selection proposed that individuals with advantageous traits are more likely to survive and reproduce, leading to changes in populations over time.
Neo-Darwinism
This incorporates genetics and Mendel’s laws into Darwin’s theory, explaining variation through sexual reproduction, genetic recombination, and mutations.
Theory of Punctuated Equilibrium
Eldredge and Gould proposed that evolution occurs in rapid bursts followed by periods of stability, with new species arising from sudden changes.
Endosymbiosis Theory
Lynn Margulis proposed that eukaryotic cells arose from symbiotic relationships between different types of bacteria.
Evolutionary Developmental Biology
This field studies how changes in genes during embryonic development can lead to the evolution of new species.
Gradualism vs. Punctuated Equilibrium
Gradualism suggests evolution occurs through slow, continuous changes, while punctuated equilibrium proposes rapid bursts of change followed by stability.
Evidence for Evolution
Embryological Evidence
Similarities in embryos of different species suggest evolutionary relationships.
Fossil Evidence
Fossils provide evidence of past life and show how species have changed over time.
Molecular Evidence
Similarities in DNA and protein sequences indicate evolutionary relationships between organisms.
Biodiversity
Biodiversity refers to the variety of life on Earth, which is a result of millions of years of evolution.