Population-Ecology

Environmental Science Overview

Definition of Population

  • A population is a group of individuals of a single species living in a particular area and interacting with each other.

Population

  • Studies how ipopulations change within an environment.

  • Changes can be long-term or short-term.

Key Population Metrics

  • Population Size: Total number of individuals.

  • Population Density: Average number of individuals per unit area or volume.

  • Age Structure: Proportions of individuals at different life stages.

  • Distribution Patterns: How individuals are spread out in a habitat (Random, Clumped, Uniform).

Principles of Population Dynamics

  • Individuals are born and die; populations change size based on:

    • Birth Rate (Natality): Production of individuals over time.

    • Death Rate (Mortality): Loss of individuals over time.

    • Biotic Potential: Maximum reproductive capacity under ideal conditions (food, absence of predators).

Factors Affecting Biotic Potential

  • Number of offspring per breeding period.

  • Survival to reproductive age.

  • Duration of reproductive age.

  • Age at which reproduction begins.

Mating Systems

  • Monogamy: Pair bonding.

  • Polygamy: Multiple mating partners.

  • Promiscuity: No long-term bonds.

Population Interactions

  • Organisms interact within their environments to survive and attain maturity. Environmental conditions can impact survival and growth.

Types of Interactions

  • Competition: When individuals or populations vie for resources.

  • Predation: One organism hunts another for nutrition.

  • Commensalism: One organism benefits, the other is unaffected.

  • Parasitism: One organism benefits at the expense of another.

  • Mutualism: Both species benefit from the interaction.

  • Amensalism: One is harmed while the other is unaffected.

Community and Ecosystems

  • Community: Collection of populations living in an ecosystem at a specific time.

  • Communities are often defined by their dominant species.

Factors Shaping Community Structure

  • Climate and topography.

  • Availability of food resources.

  • Adaptability of species.

  • Species interactions and overall population size changes.

Characteristics of Biological Communities

  • Physical Features: Relative size and stratification of populations.

  • Species Composition: Richness and abundance of species.

  • Niches: Number and diversity of ecological niches.

Community Structure

  • An ecotone is a zone of tension between different communities.

  • Structural layers include:

    • Canopy: Tallest tree layer.

    • Understorey: Layer of shrubs.

    • Herb Layer: Composed mainly of herbs.

    • Forest Floor: Ground layer of organic materials.

Aquatic Community Structure

  • Influenced by light penetration, temperature, and oxygen supply.

  • Zones in lakes include littoral, limnetic, and profundal zones.

  • Ocean zones: Pelagic, Neritic, and Oceanic zones, varying by depth and light conditions.

Habitats and Niches

  • Each species occupies a specific niche shaped by natural selection and evolution.