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Related Concept Videos

Speciation Rates01:07

Speciation Rates

Speciation can proceed at markedly different rates, and evolutionary biologists commonly describe these differences through the models of gradualism and punctuated equilibrium. Both patterns explain how new species arise, but they differ in the tempo and continuity of evolutionary change. In both cases, evolutionary change arises from heritable variation within populations, with natural selection often shaping traits that improve survival and reproduction under specific environmental conditions.
Theories of Dissolution: Diffusion Layer Model01:15

Theories of Dissolution: Diffusion Layer Model

Dissolution, the process by which drug particles dissolve in a solvent, is explained by the diffusion layer model, a theoretical framework that simulates the absorption of oral drugs and allows us to analyze experimental data.
This process starts with a thin layer, saturated with the drug, forming at the interface between the solid and liquid. The solute then diffuses from this layer into the main solution. The Noyes-Whitney equation suggests that the rate of dissolution relies on the diffusion...
Diffusion01:21

Diffusion

Diffusion is a type of passive transport. In passive transport, a substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across the space. For example, take the diffusion of substances through the air. When someone opens a perfume bottle in a room filled with people, the perfume is at its highest concentration in the bottle and is at its lowest at the edges of the room. The perfume vapor will diffuse, or spread away, from the...
Diffusion01:12

Diffusion

Diffusion is the passive movement of substances down their concentration gradients—requiring no expenditure of cellular energy. Substances, such as molecules or ions, diffuse from an area of high concentration to an area of low concentration in the cytosol or across membranes. Eventually, the concentration will even out, with the substance moving randomly but causing no net change in concentration. Such a state is called dynamic equilibrium, which is essential for maintaining overall...
Distribution and Dispersion00:54

Distribution and Dispersion

Ecology is the study of how organisms interact with their environment and with one another. An important aspect of ecology is understanding where species are found and how individuals are distributed within those areas. The geographic range of a species refers to the total area where its members are located, while dispersion describes the pattern of spacing of individuals within that range.Geographic Range and Dispersion PatternsWithin a species’ geographic range, individuals may be distributed...
Passive Diffusion: Overview and Kinetics01:17

Passive Diffusion: Overview and Kinetics

Passive diffusion is a critical process that allows small lipophilic drugs to cross the cell membrane along a concentration gradient. This mechanism's efficiency depends on four primary factors: the membrane's surface area, the drug's lipid-water partition coefficient, the concentration gradient, and the membrane's thickness.
When administered orally, drugs establish a substantial concentration gradient between the gastrointestinal (GI) lumen and the bloodstream, expediting their diffusion into...

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Related Experiment Video

Updated: Jul 6, 2026

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level
06:55

Synthesis of Cyclic Polymers and Characterization of Their Diffusive Motion in the Melt State at the Single Molecule Level

Published on: September 26, 2016

Evolution of conditional dispersal: a reaction-diffusion-advection model.

Xinfu Chen1, Richard Hambrock, Yuan Lou

  • 1Department of Mathematics, University of Pittsburgh, Pittsburgh, PA 15260, USA. xinfu@pitt.edu

Journal of Mathematical Biology
|March 5, 2008
PubMed
Summary

This study models competing species dispersal, finding that differing movement strategies can lead to coexistence. Excessive movement towards favorable environments can cause extinction, suggesting intermediate dispersal rates evolve.

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Last Updated: Jul 6, 2026

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Area of Science:

  • Mathematical Biology
  • Theoretical Ecology
  • Evolutionary Dynamics

Background:

  • Understanding species coexistence is crucial in ecology.
  • Dispersal strategies significantly impact population dynamics and competition outcomes.
  • Environmental heterogeneity influences species interactions and evolutionary trajectories.

Purpose of the Study:

  • To investigate the evolution of conditional dispersal in competing species.
  • To explore how differences in advection rates affect species coexistence.
  • To identify mechanisms driving the evolution of dispersal strategies in heterogeneous environments.

Main Methods:

  • Development and analysis of a Lotka-Volterra reaction-diffusion-advection model.
  • Simulation of two competing species with varied dispersal strategies (diffusion and advection).
  • Examination of population dynamics in response to environmental gradients.

Main Results:

  • Coexistence is possible when one species exhibits stronger biased movement (advection) along environmental gradients.
  • If both species have strong advection, overcrowding occurs, leading to the extinction of the stronger-moving species.
  • Selection may act against excessive advection, favoring intermediate dispersal rates.

Conclusions:

  • Conditional dispersal and environmental gradients offer a novel mechanism for species coexistence.
  • Evolutionary pressures can select against extreme advection, promoting intermediate movement strategies.
  • The study highlights the importance of dispersal evolution in shaping ecological communities.