JAMB Biology Note- Ecology

Topic

Factors affecting the distribution of Organisms

Table of Contents

• Topic
  • Factors Affecting the Distribution of Organisms
    • i. Abiotic Factors
    • ii. Biotic Factors
  • Summary

Factors Affecting the Distribution of Organisms

Organisms are distributed across the Earth in particular patterns due to various factors that influence where they can survive and thrive. These factors can be divided into abiotic (non-living) and biotic (living) factors.

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i. Abiotic Factors

Abiotic factors are the non-living components of the environment that influence the distribution of organisms. These include physical and chemical elements of the environment.

1. Temperature:
   • Temperature affects the metabolic rate of organisms and influences where they can live. Organisms have specific temperature ranges within which they can survive.
   • For example, most tropical plants and animals are adapted to warm temperatures, while polar species are adapted to cold conditions.
2. Rainfall:
   • The amount of rainfall in an area influences the types of organisms that can live there. Areas with high rainfall support dense vegetation, while arid areas may have desert species adapted to drought conditions.
   • Rainfall also influences the availability of water for aquatic organisms.
3. Relative Humidity:
   • Humidity refers to the amount of moisture in the air. High humidity levels are ideal for certain species, particularly tropical plants and animals. Conversely, dry conditions may restrict the growth of certain organisms.
4. Wind Speed and Direction:
   • Wind can affect the distribution of organisms, particularly in terms of plant dispersal. Strong winds can carry seeds, spores, and pollen, facilitating the spread of plants.
   • Wind also contributes to the cooling or warming of an area, influencing the survival of organisms.
5. Altitude:
   • The altitude of an area affects the temperature, oxygen levels, and pressure. Higher altitudes tend to have colder temperatures and lower oxygen levels, which can limit the types of organisms found at these heights.
6. Salinity:
   • Salinity refers to the concentration of dissolved salts in water. Freshwater organisms are adapted to low salinity, while marine organisms are adapted to saltwater environments.
   • Estuaries, where freshwater meets seawater, have organisms that are adapted to varying levels of salinity.
7. Turbidity:
   • Turbidity refers to the cloudiness or haziness of water due to suspended particles. High turbidity can affect light penetration and reduce the ability of aquatic plants to photosynthesize, thus limiting the organisms that can survive in such environments.
8. pH:
   • pH measures the acidity or alkalinity of a substance. Organisms are adapted to thrive in specific pH ranges. For instance, freshwater organisms prefer a neutral or slightly alkaline pH, while some aquatic species are adapted to acidic conditions.
9. Edaphic (Soil) Conditions:
   • Soil type, texture, structure, nutrient content, and drainage capacity can greatly influence the distribution of plants and, consequently, animals.
   • For example, cacti are adapted to grow in sandy, well-drained soils, while water-loving plants are found in marshy soils.

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Equipment Used to Measure Abiotic Factors:

• Secchi Disc: Used to measure water turbidity by determining how far light penetrates into the water.
• Thermometer: Measures temperature, essential in determining the survival range of organisms.
• Rain Gauge: Measures the amount of precipitation (rainfall) in an area.
• Hygrometer: Measures the relative humidity in the air.
• Soil pH Meter: Measures the pH of soil to determine if it is acidic, neutral, or alkaline.

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ii. Biotic Factors

Biotic factors refer to the living components of the environment that influence the distribution of organisms. These include the activities of plants, animals, and humans.

1. Plant Activities:
   • Plants are primary producers in an ecosystem and can affect the types of animals that inhabit an area. The type and density of vegetation influence the number and types of herbivores that can live in an area, which in turn affects predators.
2. Animal Activities:
   • Herbivores, predators, and decomposers play significant roles in shaping ecosystems. For example, grazing by herbivores can limit the growth of vegetation, which in turn affects other species.
3. Human Activities:
   • Deforestation: The removal of forests for agriculture, logging, or urbanization can drastically alter ecosystems, leading to the displacement of species.
   • Pollution: Pollution, both air and water, can affect the health of organisms and their ability to survive in certain environments.
   • Climate Change: Human-induced climate change alters temperature and rainfall patterns, which in turn affects species distribution.
   • Agricultural Practices: Monoculture farming, the use of pesticides, and irrigation practices can influence the availability of resources for other organisms.

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Summary

• Abiotic factors such as temperature, rainfall, humidity, wind, altitude, salinity, turbidity, pH, and soil conditions significantly affect where organisms can live.
• Biotic factors include the influence of other living organisms, such as plants, animals, and human activities, which shape the distribution and survival of organisms.
• The interaction between abiotic and biotic factors determines the distribution patterns of organisms across different ecosystems.