Evolution: Darwin’s Theory Flashcards
(11 cards)
Who were the two key influences of Darwin’s work?
1: Charles Lyell
2: Thomas Malthus
How did Charles Lyell influence Darwin’s work?
Darwin read “Principles of Geology” by him. He proposed that geological processes operate at the same rate today as they do in the past, that the earth was very old, and was still constantly changing. (Uniformitarianism) Darwin began thinking about living organisms in this same way.
How did Thomas Malthus influence Darwin’s work?
Upon his return from the Galapagos, Darwin knew organisms evolved, but didn’t have an explanation for how. He read Thomas’ “Essay on the Principle of Population”. It states plant and animal populations grow much faster than their food supply, leading to populations decreasing from starvation, disease, and war. Food increases arithmetically, populations increase exponentially. Darwin began thinking about competition for resources within populations, developing his theory of evolution.
What is Darwin’s Theory of Evolution/it’s components?
Overpopulation:
- Darwin noticed organisms try to produce many offspring. More than is needed to sustain the population.
Competition:
- In spite of many produced offspring, not all survive due to food, space, and shelter being limited. Organisms compete for these necessities.
Variations:
- Within any species, characteristics vary greatly. Species members differ in size, shape, abilities, etc; all of which are inherited.
Adaptations:
- Because variations exist, some individuals have advantages in resource competition due to advantageous adaptations.
Natural Selection:
- Better adaptations give organisms better survival chances, ergo better chances to reproduce and pass on these advantages. Nature selects which organisms survive and reproduce.
Speciation:
- Favourable adaptations accumulate and unfavourable ones dissipate in species over time. These accumulated changes eventually birth a new species.
Did Darwin know of genetics?
No, Darwin did not know of genetics. It was only later that scientists link his work with Mendel’s, giving Darwin a genetic basis for variations. (Modern synthesis)
Who was Alfred Russel Wallace?
He developed the same theory as Darwin at the same time as him, though Darwin’s was published first.
Compare Lamarck and Darwin.
Lamarck: View of evolution focused on individuals. Believed organisms evolved in response to environmental changes.
Darwin: view of evolution focused on populations. Believed organisms evolved prior to environmental changes, and these evolutions allowed them to withstand environmental changes.
Important notes on evolution:
- Environmental change is key to evolution. It’s the main directing force.
- Mutations/Genetic recombination are sources of new variations. Variation is characteristic of populations, not individuals.
- Evolution benefits species, not individuals. Individuals don’t evolve, populations do. Individuals are only naturally selected.
- Change in gene pool frequency means a population is evolving.
- Natural selection isn’t always random. Better adaptations are selected which increases chance to reproduce and pass on traits.
What did we learn from peppered moths?
1: How environmental change can affect a species’ evolution in a short time.
2: How adaptations that are useful in one environment may not be in others.
3: The moths’ gene pool changed with the environment. Most biologists define evolution as the shift in a population’s gene pool.
What is Natural selection?
Organisms with beneficial adaptations have greater survival chances in particular environments, thus better chances of reproduction to pass on said traits. Nature selects the organisms that survive/reproduce. Cannot occur without variation.
What is Artificial selection?
Humans decide which organisms survive and pass on traits. Done to get desired traits and weed out undesirable ones. May cause problems by causing persistence of certain traits from generation to generation.
