Evolutionary Biology arose from two very Important questions; 1) What were the patterns in nature’s diversity? 2) How did these patterns come to be?
Darwin’s theory of evolution by natural selection challenged the idea that people of the time had. People believed that God made all the animals and plants that live on Earth. Prior to Charles Darwin, people acknowledged that there was a system in nature, but they did not acknowledge transmutation. Transmutation is defined as the changing of a species over time. Darwin started piecing together his theory on Natural Selection between late 1830’s and early 1840’s.
This is when Darwin proposed the mechanism that gives rise to change in populations over time, is defined as Natural Selection.
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Darwin proposed that:
- Individuals within a population are variable
- Some of these variations are heritable
- In every generation, more offspring are produced than can survive. Provides a “struggle for existence”
- Survival and reproduction of individuals is not random. Individuals with more favorable variations survive and reproduce at higher rates. These individuals are naturally selected.
Prior to Darwin, there were many theories about evolution and geology. For example the ancient Greeks believed that plants and animals are classified by their method of transport. Some of these previous theories are what influenced Darwin in his formation of these view, which will be discussed at a later stage in this essay.
Darwin conducted several research projects on animals and plants in order to learn the critical process of evolution. It was during his research work in Galápagos Islands that made him understand the theory of evolution. In his findings, he observed birds dwelling in different islands displayed minor differences in their physical features. On one occasion he found out that different species of Finches birds had different beak sizes and shapes. After analysis, he discovered that the difference in beak sizes and shapes were because of food available in that particular island. Overall, he noted that each finch species was well-suited for its environment and role. So, their beaks had adapted to provide a sufficient way of collecting food and feeding. For example, species that ate large seeds tended to have larger, tough beaks, while those that ate insects had thiner, sharp beaks. Darwin returns home and came to the conclusion that adaptations and origin of new species are closely linked processes. Darwin outlined his two key ideas: evolution and natural selection.
Evolution
Darwin proposed the following points:
- species can change over time
- new species come from pre-existing species
- all species share a common ancestor
Darwin referred to the organism change in their heritable traits over generations as descent with modification. We presently now know it as Evolution.
Natural Selection
Darwin proposed Natural Selection as a mechanism of Evolution. Natural Selection explained how populations could evolve in such a way that they became better suited to their environments over time. Darwin’s concept of Natural Selection was based on many crucial concepts, such as the following.
Traits are usually heritable: In living organisms, many characteristics are inherited, or passed down from parent to offspring.
More offspring are produced than can survive: Organisms are capable of producing more offspring than their environments can support. May be due to lack of food, lack of mates or lack of habitat. Therefore, there is competition for limited resources in each generation.
Offspring vary in heritable traits: The offspring in any generation will be slightly different from one another in their traits. For example, size, color, shape and many more. Many of these features will be heritable.
Based on his observations, Darwin came to the following conclusions:
In a population, some individuals will inherit traits that give them the upper hand in surviving and reproducing. Those individuals with the helpful traits tend to survive longer and in return, produce more offspring.
These helpful traits are heritable, and due to the fact that these helpful traits allow individuals to leave more offspring, the traits will tend to become more frequent as the population grows (in the next generation)
Over generations, the population become more adapted to their environment.
These observations and conclusions allowed Darwin to explain and understand the patterns he had seen during his research.
Prior to Darwin there were many theories about evolution and geology that influenced Darwin in his formulation of his views.
Baptiste Lamarck
Lamarck was a French naturalist. Lamarck was one of the first few scientists to propose that species change over time. Although he was right about species changing over time, his idea of how they changed was wrong. His idea of inheritance of acquired characteristics meant that if an organism changes during its life to adapt to its environment, those changes would then be passed down to its offspring. This statement is clearly untrue but his idea of species changing over time is in alignment with Darwin’s ideas on natural selection.
Thomas Malthus
Malthus was an English economist. In his essay titled “Principle of Population”, Malthus stated that human populations grow faster than the resources they depend on. When the population becomes too large, disease and famine could potentially occur, which kills of the weaker individuals. Malthus argued that only a fraction of the population will survive and reproduce. Malthus’ principle of population caused Darwin to think about the importance of overpopulation and the effect it potentially has. Darwin concluded that it was necessary to have variability in different populations and that the fittest do survive.
Charles Lyell
Lyell was an English geologist. Lyell proposed that gradual geological processes have gradually shaped Earth’s surface. Lyell also proposed that the earth was older than what everyone believed at the time. Lyell’s proposal influenced Darwin’s idea to believe that life forms could also change over time.
To conclude, Darwin’s proposal on Evolution and Natural selection are true and can be proved with research he had conducted. Darwin also was influenced by theories prior to him
