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Population Growth

Population Growth

Population size is dynamic, increasing with birth rates and immigration, and decreasing with death rates and emigration. In ideal conditions with unlimited resources, populations can increase exponentially, which plots as a J-shaped growth rate curve of population size against time. This type of curve is characteristic of newly-introduced invasive species, or populations that have suffered catastrophic declines and are rebounding.

Conservation of Small Populations

Conservation of Small Populations

Small population sizes put a species at extreme risk of extinction due to a lack of variation, and a consequent decrease in adaptability. This weakens the chances of survival under pressures such as climate change, competition from other species, or new diseases. Large populations are more likely to survive pressures such as these, as such populations are more likely to harbor individuals that have genetic variants that are adaptive under new stresses. Small populations are much less...

Hardy-Weinberg Principle

Hardy-Weinberg Principle

Diploid organisms have two alleles of each gene, one from each parent, in their somatic cells. Therefore, each individual contributes two alleles to the gene pool of the population. The gene pool of a population is the sum of every allele of all genes within that population and has some degree of variation. Genetic variation is typically expressed as a relative frequency, which is the percentage of the total population that has a given allele, genotype or phenotype.

Genetic Drift

Genetic Drift

Natural selection—probably the most well-known evolutionary mechanism—increases the prevalence of traits that enhance survival and reproduction. However, evolution does not merely propagate favorable traits, nor does it always benefit populations.

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).

Conservation of Declining Populations

Conservation of Declining Populations

Conservation of declining population focuses on ways of detecting, diagnosing, and halting a population decline. The approach uses methods to prevent populations from going extinct.

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Related Experiment Video

Updated: Mar 20, 2026

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Following the Dynamics of Structural Variants in Experimentally Evolved Populations

Published on: February 3, 2023

Harvest-induced evolution and effective population size.

Anna Kuparinen¹, Jeffrey A Hutchings², Robin S Waples³

¹Department of Environmental Sciences University of Helsinki Helsinki Finland.

Evolutionary Applications

|June 2, 2016

Summary

This summary is machine-generated.

Fishery-induced evolution can impact effective population size (N e). Harvest primarily reduces N e through lower recruitment, not adult mortality, and evolution can help restore genetic variability.

Keywords:

contemporary evolution fisheries management life history evolution population genetics – empirical wildlife management

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Predicting the Effectiveness of Population Replacement Strategy Using Mathematical Modeling

Predicting the Effectiveness of Population Replacement Strategy Using Mathematical Modeling

Published on: July 4, 2007

Area of Science:

Evolutionary biology
Fisheries science
Population genetics

Background:

Fishery-induced evolution (FIE) is well-studied, but its impact on effective population size (N e) is less understood.
Effective population size (N e) is crucial for evolutionary potential and genetic diversity.

Purpose of the Study:

To investigate how fisheries harvest affects effective population size (N e) in exploited populations.
To determine the relationship between harvest, census size (N), and the N e/N ratio under different mortality scenarios.

Main Methods:

Simulations of Atlantic cod populations subjected to harvest.
Artificial manipulation of cod life tables.
Analytical methods to assess changes in N e, N, and the N e/N ratio.

Main Results:

Harvest-induced reductions in N e are primarily driven by decreased recruitment.
Increased adult mortality from harvest can paradoxically increase the N e/N ratio.
In evolutionary scenarios, N e recovered rapidly post-harvest and exceeded pre-harvest levels.

Conclusions:

Harvest's impact on N e is mainly through recruitment, not adult mortality.
Evolutionary adaptation can provide a long-term buffer against genetic diversity loss caused by fishing.
Understanding N e dynamics is critical for sustainable fisheries management and conservation.