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Jan 1, 1000
Pansemia Theory
It suggests that life could have existed on another planet and moved to Earth by meteorites, comets etc. -
Jan 1, 1000
Chemical Evolution Theory
This theory states that the first living organisms that appeared on Earth arose from inorganic matter in a time when the chemical environment and conditions of the planet were very different from today’s conditions. -
Jan 1, 1000
Creationism and Fixed Species
Creationismstates that life on Earth was created by God, in one or multiple ‘creation events’
Fixed speciesbelieves that the different forms of life that had been individually made by the Creator have stayed immutable over the history of life. -
Jan 1, 1000
Theory of Spontaneous Generation
4th Century BC - 1864
People, believed that higher living organisms, including man, had a divine origin; however, simple living organisms could come into being by spontaneous generation (non-living objects can give rise to living organisms). It was common knowledge. Louis Pasteur carried out an experiment and by 1864 proved that microorganisms did not arise by spontaneous generation. -
Lamark's Theory of Evolution 2
- Lamarck believed that the modifications an organism acquires during its lifetime are passed to its offspring (inheritance of acquired characteristics).
- One species cannot transform into any other species, but only into a similar one where the species can evolve gradually. Flaws:
- There is no evidence to prove that innate tendency (vital impulse) of organisms toward complexity.
- Acquired characteristics are not inherited as they are not genetic.
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Lamarck’s Theory of Evolution 1
- Evolution was driven by an innate tendency towards higher and greater complexity.
- This innate tendency to perfection is influenced by environmental changes, therefore becoming better adapted to their environments. These environmental changes would create ‘new needs’ in organisms, needing to use certain organs or characteristics more than others.
- The function makes the organ. So, organisms could acquire certain characteristics throughout its lifetime, and lose others.
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Catastrophism
Georges
Cuvier (1769-1832), explained the existence of fossils based on the view of Earth’s history known as catastrophism; during catastrophic events (such as floods or drought), species, created by God, would die. -
Darwin's Theory of Evolution 1
Not all gametes produced by an individual end up becoming zygotes; not all zygotes become adults; and not all the adults survive and reproduce. So, production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of offspring surviving each generation. -
Darwin's Theory of Evolution 2
Survival in the struggle for existence is not random, but depends in part on the hereditary constitution of the surviving individuals. Those individuals whose inherited characteristics fit them best to their environment are likely to leave more offspring than less fit individuals. -
Georges-Louis Leclerc Compte de Buffon
He proposed that species had not been created as they appeared, but rather that species of the time were modified forms of common ancestors. He writes that living creatures evolve according to natural laws. -
Georges-Louis Leclerc Compte de Buffon
He studied animals and plants fossils, proposing that species had not been created as they appeared, but rather that species of the time were modified forms of common ancestors. He writes that living creatures evolve according to natural laws. However, his heretical* ideas were later recanted under pressure. -
Neo-Darwinism
It brings together Charles Darwin's theory of the evolution of species by natural selection with Gregor Mendel's theory of genetics as the basis for biological inheritance.
We can define evolution as the natural selection (which is seen through differential reproduction), that acts upon genetic variations (which are the outcome of mutations or sexual recombination) which appear among the members of a population.