Abiotic Factors Drive Selection by Their Density-Independent Impact
- Abiotic factors, the non-living components of an ecosystem, shape populations by exerting density-independent selection pressures.
- Unlike biotic factors, which depend on interactions between organisms, abiotic pressures affect individuals regardless of population size or density.
Definition
Abiotic factors
A non-living component of the environment, such as temperature, light, or water availability, that influences the survival and reproduction of organisms.
Definition
Biotic factors
A biotic factor is a living organism that shapes its environment.
Examples of Abiotic Factors in Selection
- Abiotic factors influencing natural selection include:
- Temperature Extremes: Frost or heatwaves can selectively impact survival.
- Salinity: Organisms must tolerate specific salt concentrations in their habitat.
- Droughts and Floods: Water availability is a critical factor for both plants and animals.
- Soil and pH Levels: Soil composition and acidity affect plant survival.
In a marine ecosystem, biotic factors can include: algae, plankton, bacteria, plants, corals, fIsh, sharks, and jellyfish.
Density-Independent Abiotic Factors
- Density-independent factors affect populations regardless of their size or density.
- These factors often include extreme or catastrophic events, such as:
- Temperature Extremes: Heatwaves or freezing temperatures.
- Natural Disasters: Floods, wildfires, or earthquakes.
- Pollution: Chemical spills or air pollution.
- Climate Events: Droughts or hurricanes.
- Abiotic factors are density-independent because their impact remains constant regardless of population size.
- Frost in Plants: In a sudden frost, all plants in a population experience the same conditions.
- Differences in frost tolerance determine which individuals survive.
- Salt Concentrations in Salicornia: Marsh samphire thrives in salt marshes because its cells store excess salt, making it more tolerant to high salinity.
Natural Disasters Create Abrupt Selection Pressures
- These can include:
- Flooding: Destroys non-adapted plant species.
- Wildfires: Select for plants capable of resprouting or with fire-resistant seeds.
- Earthquakes: Alter habitats, favouring species able to adapt quickly.
Human Influence Drives New Selection Pressures
- In Mozambique, poaching pressure has acted as a selection pressure favouring tuskless elephants.
- In populations exposed to poaching:
- Tuskless elephants have a survival advantage, as they are not targeted for ivory.
- Over time, the frequency of tusklessness has increased, illustrating the role of human activity as an abiotic selection pressure.
How does the increase of tuskless elephants in Mozambique reflect the principles of negative feedback mechanisms seen in cells and our bodies?
Abiotic Pressures Drive Adaptation and Long-Term Change
- Abiotic factors drive natural selection by favouring individuals with traits that enhance survival in specific environments.
- Over time, these traits become more common in the population, leading to evolutionary change.
- Unlike biotic factors (e.g., predation or competition), abiotic factors do not depend on interactions between organisms.
- They are purely environmental.
Trade-Offs Limit Adaptations to Abiotic Factors
- Unpredictability: Abiotic factors like natural disasters are often sudden and unpredictable, making it difficult for populations to adapt quickly.
- Trade-offs: Adaptations to one abiotic factor may reduce fitness in other conditions. For example, plants adapted to drought may struggle in waterlogged soils.
- Human Impact: Pollution and climate change introduce new abiotic pressures, often faster than populations can adapt.
- How might climate change alter abiotic selection pressures in ecosystems worldwide?
- What ethical considerations arise when human activities disrupt these natural processes?
