Unit 7: Topic 1 - Introduction to Natural Selection Flashcards
What is the most important process in the theory of evolution?
The natural selection process supports the change over time of a population based on the favorable phenotypes presented and passed onto offspring.
What causes generational natural selection to occur?
(Darwin’s theory) More favorable phenotypes have greater fitness (survivability and reproducibility). The organisms with greater fitness will pass on their similar traits to their offspring. This happens when there are limited resources, and competition allows the organism with the greatest fitness to survive and pass on its traits. Another instance is when an organism has a beneficial mutation that allows it to have greater fitness than the other organisms in its species/population.
How does reproductive success relate to evolutionary fitness?
Greater evolutionary fitness results in greater reproductive success, as that organism will have its traits in more offspring, ultimately taking up the majority of its species.
How do abiotic factors relate to evolution.
Abiotic factors, such as the terrain or weather, will determine which phenotype is naturally selected for. Abiotic factors can also limit the growth of the population. For instance, if there is insufficient space for organisms to reproduce further, the population size is limited. Natural disasters spur on natural selection. For example, if a snowstorm placed a population under extremely low temperatures, only the organisms that could withstand the temperature would survive, and this would change the course of evolution for the organisms that lived on.
How do biotic factors relate to evolution.
Biotic factors, such as competition for limited resources and predation, affect which organisms in a population would be able to survive. Competition results in one of the species occupying a different niche (food source or area) or being driven to extinction. Predation results in the prey and predator evolving in a much faster time frame. The only organisms that will be naturally selected will be the organisms that can adapt to survive their predators and, similarly, the predators that can consume their prey.
What is stabilizing selection?
Stabilizing selection is when a population favors a non-extreme or median phenotypic trait. It is the most common type of selection. For example, white and black mice would not be naturally selected for if mice were introduced to an environment with a brown surface area, such as a forest floor. Instead, the non-extreme or middle-brown phenotype would be selected for. Click here
What is directional selection?
Directional selection is when a population favors a single extreme phenotypic trait. The population will shift towards one extreme. For example, England’s trees gradually got covered in soot during the Industrial Revolution, turning them from lighter to darker colors. As a result, black-peppered moths, an extreme phenotypic trait, were naturally selected instead of white-peppered moths due to environmental change. Click here
What is disruptive selection?
Disruptive selection is when a population favors both extreme phenotypic traits. The population will shift in two directions, away from the non-extreme or median. For example, light and dark-colored oysters can be selected for in an ocean environment due to light-colored oysters camouflaging with the rocks on the ocean floor and dark-colored oysters camouflaging with shadows cast by the rocks. Click here
