Study Notes on Ecosystems and Biotic/Abiotic Factors

Biosphere to Ecosystems

Importance of Soil Water

  • Soil water is crucial for plants and exists in three forms:

    • Hygroscopic Water

    • Water molecules cling to soil particles through adsorption.

    • This water is not available to plants.

    • Capillary Water

    • Found between soil particles.

    • This form of water can be absorbed by plants.

    • Seepage Water (Gravitational Water)

    • Initially available to plants as it seeps through upper soil layers.

    • Becomes inaccessible to plant roots as it moves to deeper layers.

    • Also known as borehole water.

  • Visual Representation:

    Water molecules ==> Soil particles

Soil Acidity

  • Acidic Soil
    • Commonly found in regions with high rainfall.
    • Rainwater leaches salts from the soil, replaced by H⁺ ions, leading to low pH levels.
    • Most plants prefer neutral or slightly alkaline soil.

Abiotic Factors Affecting the Environment

  • Several abiotic factors influence the physical nature of an environment:
    1. Physiographic Factors
    • Includes appearance, gradient, topography, and locality.
    1. Soil Factors (Edaphic Factors)
    • Covers soil types, texture, profiles, and moisture levels.
    1. Temperature
    • Considers day and night temperatures and their influence on climate.
    1. Atmospheric Gases
    • Comprises composition of air and wind patterns.
    1. Water
    • Encompasses the water cycle and plant adaptations.
    1. Light
    • Involves light intensity and radiation periods (length of day).
    1. Fire
    • Includes surface and crown fires, relevant to ecosystems like Fynbos.

Biotic Factors in Ecosystems

  • Biotic Factors
    • Comprise the living components of an ecosystem, which include:
    • Plants
    • Animals
    • Microorganisms (e.g., bacteria that are sometimes difficult to categorize).

Producers and Energy Conversion

  • Producers (Green Plants)
    • Contain chlorophyll and are responsible for producing energy in ecosystems.
    • Convert radiant energy into a usable form through photosynthesis.
    • Classified as autotrophic organisms as they can trap energy and create organic compounds from inorganic materials.

Consumers

  • Consumers
    • Are heterotrophic organisms reliant on energy stored in organic compounds produced via photosynthesis.
    • Types of consumers include:
    • Herbivores
      • Primary consumers that feed on plants.
    • Carnivores
      • Secondary or tertiary consumers that feed on other animals.
  • Decomposers
    • Play a vital role in all levels of the ecosystem by decomposing dead organic matter (plants and animals), allowing nutrients to re-enter the ecosystem—part of the "cycle of life".

Consumer Behavior

  • Predators
    • Hunt, kill, and eat their prey.
  • Scavengers
    • Consume dead organisms and remain dependent on remnants left by predators (e.g., vultures).
  • Opportunistic Feeders
    • Such as baboons, which eat various available food sources.