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Biology LibreTexts

24.1: Case Study - The Web of Life

  • Page ID
    22635
  • Case Study: Farming for Balance

    Camille grew up in a rural farming community, and both of her parents worked on a local farm. When pesticides were being applied to the crops, as in the picture below, her parents had to use special protective equipment such as coveralls, gloves, and respirators. This is because many pesticides, which are substances that protect plants from damage and destruction by pests such as insects, can be hazardous to human health if inhaled, consumed, or absorbed through the skin. Camille began to wonder — if pesticides can be dangerous to humans, do they have negative effects on other animals and the rest of the environment?

    farm
    Figure \(\PageIndex{1}\): Pesticide application on leaf lettuce in Yuma, Az. Image used with permission (Public Domain; Jeff Vanuga, USDA Natural Resources Conservation Service).

    As an adult, Camille noticed that some food items in the grocery store were labeled with a seal indicating they are organic — like the seal in Figure \(\PageIndex{3}\). Camille knew that organic food is generally grown without synthetic (man-made) pesticides, and she liked the idea of buying organic food to support this kind of agriculture. However, she also noticed that organic food tends to be slightly more expensive than conventionally-produced food, so she wanted to learn more about what “organic” means and whether organic agricultural practices are really better for the environment as a whole.

    Caution pesticide spray sign
    Figure \(\PageIndex{2}\): Manito Park in Spokane, WA. Image used with permission (CC BY 2.0; jetsandzeppelins).

    Camille did some research online and found out that organic food products in the U.S. are regulated by the U.S. Department of Agriculture (USDA). The USDA has a detailed set of requirements that describe the practices that farmers must use in order to label their food products as organic. These including not using most synthetic chemical substances, such as pesticides or fertilizer, on crops. Organic meat must come from animals that are fed organic feed and meet various other criteria. On the USDA’s National Organic Program website, Camille noticed the statement: “Organic is a labeling term for food or other agricultural products that have been produced using cultural, biological, and mechanical practices that support the cycling of on-farm resources, promote ecological balance, and conserve biodiversity in accordance with the USDA organic regulations.” This statement indicated to Camille that organic agricultural practices are beneficial for the environment, but how exactly do they provide these benefits?

    USDA organic seal
    Figure \(\PageIndex{3}\): USDA organic logo. Image used with permission (Public Domain; United States Department of Agriculture).

    As you read this chapter, you will learn about the science of ecology — that is, the study of the complex relationships between living organisms and the environment around them. You will see how interactions between different species and non-living components of the environment can come into balance, and how drastic changes can occur when this balance is altered. By the end of the chapter, you will have a better understanding of what is meant by resource recycling, ecological balance, and biodiversity, and the importance of these concepts. Then in the conclusion to this case study, you will learn specifically how these concepts relate to organic agricultural practices. This information can help you, as well as Camille, make a more informed decision about whether to choose organic foods.

    Chapter Overview: Ecology

    In this chapter, you will learn about ecology and how it relates to humans. Specifically, you will learn about:

    • How the biological world is organized into nested ecological hierarchies including the individual, population, community, ecosystem, biome, and biosphere.
    • Basic concepts in ecology including the ecosystem, niche, habitat, and the competitive exclusion principle.
    • The goods and services ecosystems provide to humans, including food and oxygen production.
    • The types of relationships between species in a community, including different types of symbiotic relationships, predation, and competition. The effect of community relationships on the evolution of adaptations and the extinction of species.
    • The two basic types of organisms in terms of how they obtain energy: autotrophs (producers) and heterotrophs (consumers). Types of heterotrophs including herbivores, omnivores, carnivores, and decomposers.
    • How energy flows through ecosystems from producers up through food chains and webs.
    • Trophic levels, which are the feeding positions in a food chain or web, starting with producers at the first trophic level and moving up through higher levels of consumers.
    • How the amounts of energy and biomass change from lower to higher trophic levels.How matter cycles through ecosystems in the form of biogeochemical cycles of water, carbon, nitrogen, and phosphorus.
    • Demography, which is the scientific study of human populations including size, geographic distribution, and structure, such as the number of people in different age groups in the population.
    • The age-sex structure of populations and how this may provide insight into political and socioeconomic change.
    • Exponential growth compared to logistic growth, the latter of which slows as the population reaches a size called the carrying capacity.
    • How the human population may currently be near the carrying capacity, which could result in environmental damage, disease, war, and famine; and how these negative effects are exacerbated by excessive use of resources by wealthier countries.
    • How zero population growth and strategies to reduce the fertility rate can help mitigate problems caused by overpopulation.
    • Projections of future human population growth and how these predictions are made.
    • Global climate change, and how human activities have intensified the greenhouse effect, causing global warming. Projections of future global warming; potential impacts of global warming on humans such as increased coastal flooding, lack of food and water, and violence; and how we can lessen the threat by moving away from fossil fuels towards cleaner sources of energy.

    As you read the chapter, think about the following questions:

    1. The use of some pesticides has been shown to kill bees. How could this affect an ecosystem?
    2. Synthetic fertilizers often have high amounts of nitrogen and phosphorus. Why do these fertilizers contain these elements? Can you predict any ecological disturbance that an excess amount of these elements might cause?
    3. Organic agricultural methods generally increase soil quality. What is soil quality, and how does it relate to biodiversity and biogeochemical cycles?