Natural Selection

Definition

Natural selection is the process through which organisms better adapted to their environment tend to survive and produce more offspring. This mechanism is a key driver of evolution, where genetic variations arise primarily through mutations, leading to differences in traits among individuals. Over generations, favorable traits become more common in a population, illustrating how natural selection acts on genetic variation to shape the diversity of life.

5 Must Know Facts For Your Next Test

1. Natural selection operates on existing genetic variation within a population, and mutations serve as the primary source of this variation.
2. The concept of survival of the fittest relates to natural selection, emphasizing that those with advantageous traits are more likely to reproduce and pass those traits on.
3. Natural selection can lead to speciation, where populations diverge into distinct species over time as they adapt to different environments.
4. Different types of natural selection include directional selection, stabilizing selection, and disruptive selection, each shaping traits in unique ways.
5. Human activities can influence natural selection by creating new environmental pressures, leading to rapid changes in species' traits.

Review Questions

• How does natural selection contribute to the process of evolution in populations?
  • Natural selection contributes to evolution by favoring individuals with traits that provide an advantage in their environment, allowing them to survive and reproduce more effectively. As these advantageous traits become more common over generations due to the reproductive success of those individuals, the overall genetic makeup of the population shifts. This gradual change in allele frequencies exemplifies how natural selection drives evolutionary change and increases the adaptation of species.
• Compare and contrast natural selection with genetic drift, highlighting their roles in shaping genetic variation.
  • Natural selection and genetic drift are both mechanisms that affect genetic variation but operate under different principles. Natural selection involves differential survival and reproduction based on advantageous traits, leading to adaptive changes in a population over time. In contrast, genetic drift is a random process that can lead to significant changes in allele frequencies due purely to chance events, especially in small populations. While natural selection is a non-random process favoring specific traits, genetic drift can lead to loss or fixation of alleles without regard for their adaptive value.
• Evaluate the impact of human-induced changes on natural selection and its implications for biodiversity.
  • Human-induced changes such as habitat destruction, pollution, and climate change significantly alter environmental pressures on species. These changes can accelerate natural selection by creating new challenges that organisms must adapt to quickly. This rapid shift may lead to increased extinction rates as some species fail to adapt, while others may develop new traits that allow them to thrive. The implications for biodiversity are profound, as these dynamics can result in reduced genetic diversity within populations and even the emergence of new species adapted to altered environments.

Related terms

Genetic Drift: A random process that can lead to changes in a population's allele frequencies, affecting genetic variation independently of natural selection.

Adaptation: A trait that enhances an organism's fitness in its environment, often resulting from the process of natural selection.

Mutation: A change in the DNA sequence of an organism, which can introduce new genetic variation that may be subject to natural selection.