Environmental Science: Ecosystems, Pesticides, and Succession

Posted on May 16, 2026 in Biology

Answer Key: Ecology and Environmental Impact

1. Habitat Fragmentation and Farming

  1. Habitat Fragmentation: This occurs when a large ecosystem is split into smaller sections by roads, buildings, or farms, making it difficult for animals to find shelter, food, or mates.
  2. Alternative Farming Practices:
    • Crop rotation
    • No-till farming
    • Organic farming

    Example: No-till farming involves planting crops without turning over the soil, which reduces erosion, retains moisture, and protects soil organisms.

2. Pesticides and Bioaccumulation

  1. Problems with Pesticide Use:
    • Poisoning of non-target species like birds and insects.
    • Water pollution via chemical runoff into rivers and lakes.
    • Development of pest resistance, requiring stronger chemicals.
  2. Toxin Dynamics:
    • Bioaccumulation: Toxins slowly collect inside a single organism.
    • Bioamplification: Toxin levels increase at each level of the food chain.
  3. Soil Quality: Loam is the ideal soil type due to its balanced mix of sand, silt, and clay, which supports healthy plant growth.

3. Ecosystem Threats and Pollution

  1. Invasive Species: Species like the Zebra Mussel compete with native organisms for food and habitat, disrupting the food chain.
  2. Measurement: PPM stands for “parts per million.” (1000 L = 1,000,000 mL).
  3. Pesticide Residues: Small amounts of chemicals remaining on food or in water can harm humans and wildlife over long-term exposure.
  4. Great Pacific Garbage Patch: Cleanup is essential to protect marine life and prevent microplastics from entering the food chain, though it remains a significant logistical challenge.

4. Ecological Processes

  1. Eutrophication: Fertilizer runoff causes excessive algae growth. When algae die, decomposers consume oxygen, leading to oxygen depletion in water bodies.
  2. Natural Wildfires: Fires support biodiversity by clearing dead vegetation, returning nutrients to the soil, and enabling fire-dependent species to reproduce.
  3. Pesticide Impacts:
    • Human Health: Pesticides can accumulate in body fat and affect fetal development in pregnant or nursing mothers.
    • Bird Populations: Chemicals cause thin eggshells and poor chick health, leading to population decline.
    • Organic Benefits: Organic farming reduces synthetic chemical intake, protecting both human health and wildlife.
  4. Habitat Management Strategies:
    • a. Cut small patches.
    • b. Leave a buffer along streams.
    • c. Cut irregular shapes.
    • d. Create meandering or wavy roads.
    • e. Build dirt roads.

5. Advanced Ecological Analysis

  1. Trout Population Decline: Caused by eutrophication (oxygen depletion) or rising water temperatures, which reduce dissolved oxygen levels.
  2. Concentration Comparison: 1 ppm is greater than 899 ppb because 1 ppm equals 1000 ppb.
  3. Secondary Succession: Abandoned farmland undergoes secondary succession, progressing from grasses and weeds to shrubs, and eventually to a mature forest of beech, maple, and oak.