Population Growth, Regulation & Biodiversity Conservation

Posted on Feb 18, 2026 in Geography

Population Growth and Regulation

📈 Population: Growth and regulation

Population ecology studies the factors that affect the size, distribution, density, and age structure of populations. Population size is dynamic, influenced by inputs and outputs.

Population Growth

The size of a population (P_t) at a given time (t) is determined by four fundamental factors:

Where:

• P_0 is the initial population size.
• N is natality (birth rate / number of births).
• I is immigration (inward movement of individuals).
• M is mortality (death rate / number of deaths).
• E is emigration (outward movement of individuals).

When births and immigration exceed deaths and emigration, the population grows. When the reverse is true, the population declines.

Models of Population Growth

Two primary mathematical models describe population growth trends:

1. Exponential Growth (J-Shaped Curve)

• Concept: Occurs when resources (food, space, etc.) are unlimited or not yet limiting.
• Rate: The population’s growth rate increases rapidly and continuously, proportional to its current size.
• Curve: When population size (N) is plotted against time (t), it produces a J-shaped curve.
• Equation: dN/dt = rN
  • r is the intrinsic rate of natural increase (per capita birth rate minus per capita death rate, b − d).
• Relevance: This model is not sustained indefinitely in nature but can be observed in populations (like bacteria or invasive species) introduced into a new, resource-rich environment for a short period.

2. Logistic Growth (S-Shaped Curve)

• Concept: A more realistic model that accounts for the fact that resources in nature are limited.
• Carrying capacity (K): The maximum population size that a specific environment can sustain indefinitely, given the available resources.
• Rate: Growth is initially exponential but slows as the population approaches K due to increasing environmental resistance (scarcity of resources, increased competition).
• Curve: Plots as an S-shaped (sigmoid) curve.
• Equation: dN/dt = rN ((K - N) / K)
  • The term (K - N) / K represents the degree of environmental resistance. As N approaches K, this term approaches zero and the growth rate approaches zero.
• Relevance: Most natural populations tend to follow the logistic growth model.

Population Regulation

Population regulation is the process by which environmental factors limit population size, often keeping it near the carrying capacity (K). These limiting factors are classified based on how their effect relates to population density.

1. Density-Dependent Factors

Definition: Factors whose impact on population growth (mortality or natality) increases as population density increases. They act as a negative feedback loop, preventing the population from growing indefinitely.

Nature: Generally biotic (living) factors.

Examples:

• Competition: Intense contest for limited resources (food, water, shelter) within a species (intraspecific) or between species (interspecific).
• Predation: Predators often focus on prey populations that are denser, increasing the prey’s death rate.
• Disease/Parasitism: Diseases spread more easily and rapidly in crowded populations.
• Waste Accumulation: High density can lead to the buildup of toxic waste products.

2. Density-Independent Factors

Definition: Factors whose impact on population growth is unrelated to population density. They affect individuals equally regardless of how crowded the population is.

Nature: Generally abiotic (non-living) factors.

Examples:

• Weather/Climate: Extreme temperatures, droughts, or severe winter conditions.
• Natural Disasters: Fires, floods, volcanic eruptions, or earthquakes.
• Pollution: Chemical or environmental changes that affect all organisms in an area similarly.

These two types of factors often interact in complex ways to determine the precise size and fluctuation of a population over time.

To see the difference between these two growth patterns visually, check out this video: Logistic vs Exponential Growth: Population Ecology.

Population Interactions

Below are common types of species interactions that shape population dynamics:

1. Competition

• Definition: Interaction between individuals of the same or different species competing for a shared resource.
• Types:
  • Intraspecific competition: Competition within the same species.
  • Interspecific competition: Competition between different species.
• Effects: Can lead to reduced growth, survival, and reproduction.

2. Predation

• Definition: Interaction where one organism (predator) captures and consumes another organism (prey).
• Effects: Regulates prey populations and influences predator populations.

3. Parasitism

• Definition: Interaction where one organism (parasite) benefits at the expense of another organism (host).
• Types:
  • Endoparasites: Live inside the host’s body.
  • Ectoparasites: Live on the host’s body.
• Effects: Can harm the host’s health and reduce its fitness.

4. Commensalism

• Definition: Interaction where one organism (commensal) benefits and the other organism (host) is neither harmed nor benefited.
• Examples: Remora fish and sharks; epiphytes on trees.
• Effects: Commensal benefits while the host is unaffected.

Other Interactions

There are additional interaction categories, the most notable of which is:

5. Mutualism

• Definition: Interaction where both organisms benefit from each other’s presence.
• Examples: Bees and flowers; clownfish and sea anemones.
• Effects: Both organisms experience increased fitness and benefits.

Biodiversity

🌿 Concept of biodiversity

Biodiversity (short for biological diversity) is the variety of life on Earth at all levels of biological organization. It encompasses the totality of genes, species, and ecosystems in a region.

Biodiversity is essential because it forms the web of life upon which humanity depends for food, water, medicine, a stable climate, and economic growth.

Three Levels of Biodiversity

Biodiversity is typically measured and studied at three fundamental levels:

• Genetic diversity: The variation of genes within the individual members of a single species.
  • Significance: Higher genetic diversity allows a species to adapt better to environmental changes (like disease or climate change) because it increases the chances that some individuals will possess traits necessary for survival.
• Species diversity: The variety of species within a specific region or ecosystem. Measured by the number of different species (species richness) and the relative abundance of those species (species evenness).
• Ecosystem diversity: The variety of different habitats, ecological communities, and ecological processes within the biosphere (e.g., deserts, forests, grasslands, oceans, and wetlands).
  • Significance: Maintaining this diversity ensures that various ecological processes (like nutrient cycling and water purification) are sustained.

Conservation of Natural Resources

Conservation of natural resources refers to the protection, preservation, management, and efficient use of the Earth’s natural resources to ensure sustainable benefits for both present and future generations.

The core goal of conservation is sustainable development, which means using resources at a rate that allows them to regenerate or be replaced by natural processes.

Main Objectives of Conservation

• Preservation of diversity: Protecting species, genetic, and ecosystem diversity (i.e., biodiversity conservation).
• Sustainable utilization: Using resources (like timber, fish, or water) at a rate that allows for their natural replenishment.
• Maintenance of ecological processes: Ensuring essential life-supporting systems (like the water cycle, soil formation, and carbon sequestration) remain functional.

Methods of Conservation

Conservation efforts span various resources and employ both general and specific strategies:

I. General Strategies (The 3 R’s)

• Reduce: Minimizing the use of resources (e.g., consuming less energy, limiting water usage).
• Reuse: Finding new uses for items instead of discarding them.
• Recycle: Processing used materials (like paper, plastic, or metal) into new products.

II. Specific Conservation Methods

The video The Three Levels of Biodiversity – YouTube provides a visual explanation of genetic, species, and ecosystem diversity, which are central to the concept of biodiversity and its conservation.