Natural Selection

Definition

Natural selection is a fundamental mechanism of evolution where organisms better adapted to their environment tend to survive and produce more offspring. This process drives the evolution of species by favoring traits that enhance survival and reproduction, leading to a gradual change in the population over generations. It plays a crucial role in shaping biodiversity, influencing how life emerges and transitions through different stages.

5 Must Know Facts For Your Next Test

1. Natural selection occurs when individuals with advantageous traits have a higher chance of survival and reproduction, gradually leading to the prevalence of those traits in the population.
2. Mass extinctions can create new ecological niches, allowing for rapid evolution and the emergence of new species through natural selection as survivors adapt to fill these roles.
3. Natural selection contributes to speciation by driving populations to adapt to different environments, leading to reproductive isolation over time.
4. The concept of survival of the fittest is often misunderstood; it refers more to reproductive success than mere survival, as many factors influence fitness.
5. Natural selection works on existing variation within a population, meaning it cannot create new traits but rather selects for or against those already present.

Review Questions

• How does natural selection explain the emergence of diverse life forms following mass extinctions?
  • After mass extinctions, the available ecological niches increase as many species disappear. Natural selection then allows the surviving organisms to adapt rapidly to these new niches. This adaptive radiation leads to the emergence of diverse life forms as populations evolve specific traits that enhance their chances of survival and reproduction in changing environments.
• In what ways does natural selection influence the characteristics that define life during major evolutionary transitions?
  • Natural selection plays a pivotal role during major evolutionary transitions by promoting traits that enhance survival and reproductive success. For example, during the transition from single-celled to multi-celled organisms, natural selection favored increased cooperation among cells, leading to complex life forms. This process highlights how natural selection shapes not only individual traits but also broader patterns of life through evolutionary history.
• Evaluate the long-term impacts of natural selection on biodiversity and the overall evolutionary process.
  • Natural selection has significant long-term impacts on biodiversity by fostering the adaptation and specialization of species. Over time, it can lead to increased diversity as populations evolve distinct characteristics suited to their environments. This process drives speciation and can result in complex ecosystems with interdependent species. Additionally, natural selection interacts with other evolutionary mechanisms, such as genetic drift and gene flow, contributing to the dynamic nature of evolution across generations.

Related terms

Adaptive Radiation: The rapid evolution of diversely adapted species from a common ancestor in response to environmental challenges and opportunities.

Fitness: A measure of an organism's ability to survive and reproduce in a particular environment compared to other organisms.

Genetic Drift:

A random process that can cause gene frequencies to change over time in small populations, influencing evolution alongside natural selection.