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 leads to the gradual evolution of species, as advantageous traits become more common within populations over time. The concept emphasizes the importance of environmental pressures and genetic variation in shaping biodiversity, influencing processes like speciation, extinction rates, and adaptive changes within ecosystems.

5 Must Know Facts For Your Next Test

1. Natural selection operates on existing genetic variation within a population, meaning that it cannot create new traits but can favor those that are already present.
2. The process can lead to adaptive radiation, where species rapidly evolve to exploit different ecological niches due to varying environmental pressures.
3. In sympatric speciation, natural selection drives divergence within a single population, often due to behavioral changes or resource use that lead to reproductive isolation.
4. Background extinction rates are influenced by natural selection, as species that cannot adapt to changing environments may fail to survive and ultimately become extinct.
5. Natural selection can also work in parapatric speciation, where adjacent populations evolve distinct characteristics due to different selective pressures in their respective environments.

Review Questions

• How does natural selection contribute to the process of sympatric speciation within a population?
  • Natural selection plays a crucial role in sympatric speciation by favoring individuals with traits that allow them to exploit different resources or habitats within the same geographic area. As these individuals become increasingly specialized, they may develop reproductive barriers that prevent interbreeding with the original population. Over time, this leads to the emergence of distinct species as natural selection drives divergence based on varying ecological preferences and adaptations.
• Discuss how background extinction rates relate to natural selection and the evolutionary dynamics of species.
  • Background extinction rates are a reflection of natural selection's role in shaping biodiversity. Species that are unable to adapt to changing environmental conditions or competition from other organisms face higher risks of extinction. Natural selection can influence these dynamics by favoring traits that enhance survival and reproduction under specific circumstances. Consequently, species that lack advantageous adaptations may be lost from the ecosystem, highlighting the connection between natural selection and the overall health and stability of biological communities.
• Evaluate the impact of natural selection on adaptive radiation and how this process shapes biodiversity in response to environmental changes.
  • Natural selection is a driving force behind adaptive radiation, as it encourages rapid diversification when organisms encounter new environments or ecological opportunities. This process leads to the development of distinct species with specialized adaptations tailored to specific niches. As environmental changes occur, such as climate shifts or the introduction of new resources, natural selection promotes variations that enhance survival in these altered conditions. The result is an increase in biodiversity, with numerous species evolving from a common ancestor as they adapt to fill diverse roles in their ecosystems.

Related terms

Survival of the Fittest: A phrase often used to describe the natural selection process, emphasizing that individuals with traits better suited for their environment are more likely to survive and reproduce.

Genetic Drift: A mechanism of evolution that involves random changes in allele frequencies within a population, which can lead to significant changes over time, especially in small populations.

Adaptive Traits: Characteristics or features that enhance an organism's ability to survive and reproduce in its specific environment, shaped by the pressures of natural selection.