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What is Natural Selection?

What is Natural Selection?

Natural selection is an evolutionary process in which individuals with survival-promoting traits reproduce at higher rates. These favorable traits become more common within a population or species. Naturally selected traits initially arise via random genetic mutations. In order for selection to occur, there must be variation within a population, the trait controlling the variation must be heritable, and there must be an evolutionary advantage for variation in the trait.

Limits to Natural Selection

Limits to Natural Selection

Organisms that are well-adapted to their environment are more likely to survive and reproduce. However, natural selection does not lead to perfectly adapted organisms. Several factors constrain natural selection.

Types of Selection

Types of Selection

Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural selection can be directional, stabilizing, or disruptive. Directional selection favors one extreme trait and shifts the population towards that phenotype while selecting against individuals displaying alternate traits. Stabilizing selection favors an intermediate trait with a narrow range of variation. Deviation from the optimal phenotype towards an...

Mutation, Gene Flow, and Genetic Drift

Mutation, Gene Flow, and Genetic Drift

In a population that is not at Hardy-Weinberg equilibrium, the frequency of alleles changes over time. Therefore, any deviations from the five conditions of Hardy-Weinberg equilibrium can alter the genetic variation of a given population. Conditions that change the genetic variability of a population include mutations, natural selection, non-random mating, gene flow, and genetic drift (small population size).

Frequency-dependent Selection

Frequency-dependent Selection

When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to as frequency-dependent selection. Frequency-dependent selection may occur between species or within a single species. This type of selection can either be positive—with more common phenotypes having higher fitness—or negative, with rarer phenotypes conferring increased fitness.

In-vitro Mutagenesis

In-vitro Mutagenesis

To learn more about the function of a gene, researchers can observe what happens when the gene is inactivated or “knocked out,” by creating genetically engineered knockout animals. Knockout mice have been particularly useful as models for human diseases such as cancer, Parkinson’s disease, and diabetes.

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Related Experiment Video

Updated: Apr 2, 2026

Mutagenesis and Functional Selection Protocols for Directed Evolution of Proteins in E. coli

Mutagenesis and Functional Selection Protocols for Directed Evolution of Proteins in E. coli

Published on: March 16, 2011

When natural selection gives gene function the cold shoulder.

Asher D Cutter¹, Richard Jovelin¹

¹Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, ON, Canada.

Bioessays : News and Reviews in Molecular, Cellular and Developmental Biology

|September 29, 2015

Summary

This summary is machine-generated.

Organismal selection doesn't always optimize gene function. Evolution can lead to gene loss or degradation, even with beneficial mutations elsewhere, challenging the idea that biochemical activity dictates a gene's evolutionary path.

Keywords:

gene function genome evolution natural selection

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Mutagenesis and Functional Selection Protocols for Directed Evolution of Proteins in E. coli

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Area of Science:

Evolutionary biology
Genomics
Molecular evolution

Background:

Organismal selection is often assumed to optimize gene function.
However, gene evolution is complex and not solely driven by biochemical activity improvement.

Purpose of the Study:

To review diverse evolutionary processes affecting gene function.
To challenge the notion that biochemical activity solely determines a gene's evolutionary fate.

Main Methods:

Review of existing evolutionary logic and empirical evidence.
Analysis of mechanisms driving gene functional change and loss.

Main Results:

Natural selection can cause gene functional degradation or loss.
Linkage to favored loci, adaptation by gene loss, and selfish genetic elements impact gene evolution.
Stabilizing selection can lead to molecular divergence.

Conclusions:

A gene's evolutionary trajectory is not solely determined by its biochemical function.
Diverse evolutionary mechanisms contribute to complex patterns of genome evolution.