PDF Understanding Global Change Model (Pages 9-12)

Living things affect one another, and are therefore parts of each others’ environment. A biotic factor is any living part of the environment with which an organism might interact. Biotic factors important to a heron, for example, might include the fish and frogs it eats, predators that eat herons, a...

Living things affect one another, and are therefore parts of each others’ environment. A biotic factor is any living part of the environment with which an organism might interact. Biotic factors important to a heron, for example, might include the fish and frogs it eats, predators that eat herons, and other species that compete with them for food or space. Physical factors also affect organisms. An abiotic factor is any nonliving part of the environment, such as sunlight, heat, precipitation, humidity, wind or water currents, and soil type. For example, a heron could be affected by abiotic factors such as water availability and quality, temperature, and humidity. The difference between biotic and abiotic factors may seem clear. But many so-called abiotic factors are strongly influenced by organisms, which means that they aren’t entirely abiotic! Bullfrogs, for example, often hang out in soft “muck” along the shores of ponds. You might think that muck is a strictly abiotic factor, because it contains nonliving particles of sand and mud. But typical pond muck also contains decomposing organic material from plants and animals that live in and around the pond. Those remains decompose because they serve as “food” to bacteria and fungi that break down organic matter. That’s a lot of “biotic” mixed in with “abiotic”! “Abiotic” conditions around a pond’s mucky shore are also shaped by organisms. Trees and shrubs around the pond provide shade from strong sun, affecting the amount of sunlight and the range of temperatures the muck experiences. Those plants can also provide protection from dry winds, affecting the humidity of air above the muck. Plant roots determine how much soil washes into the pond during heavy rains. If pine trees grow nearby, decomposing needles make the soil acidic. Decomposing oak leaves, on the other hand, make soil more alkaline. Our model has three main parts, each of which represents a category of ecological concepts and processes. We will be building this model, step by step, adding icons that represent various phenomena as we describe them. The model’s middle ring, labeled “How the Earth System Works,” represents Earth’s global systems: events, processes, and cycles within the biosphere, atmosphere, geosphere, and hydrosphere. This part of the model includes phenomena discussed in this chapter, including the global climate system. This model also includes cycles of matter, energy flow, and interactions among organisms. The model’s outer ring, labeled “Causes of Global Change,” represents human activities and nonhuman events and processes that drive changes in those global systems. The model’s inner circle, “Measurable Changes in the Earth System,” contains the kinds of changes in global systems that scientists can measure. These measurements include changes in climate, sea level, air and water quality, and so on. We emphasize “measurable changes” to emphasize that these represent actual data, not hypotheses. This model, like most models, can’t describe everything as perfectly as we would like. For example, the biosphere includes parts of the atmosphere, hydrosphere, and geosphere. The hydrosphere includes water in both the atmosphere and the geosphere. And some scientists consider frozen water—snow, ice, glaciers, and so on—separately, as the cryosphere. Still, you will see that this model provides a useful framework for organizing information, demonstrating cause and effect, arguing from evidence, and examining connections among ecological events and processes. The model includes changes in global systems that scientists can measure, and the effects those changes have on ecological systems, including human society. How do we build and use our model? In this unit, you will learn about many events, processes, and interactions. That’s where the Understanding Global Change model comes in. The model serves as an “information organizer.” Whenever we discuss ecological events and processes, each will be assigned a visual symbol, or icon. Some icons represent processes in Earth’s systems. Other icons represent causes of global change. Still other icons represent measurable changes. As we learn about these events and processes, we will add we build the model, you will see how all these pieces fit together to make a picture of the way our planet operates. It will help you create concept maps that show how different aspects of weather and climate influence organisms, and how various causes of global change can influence climate. You will notice that this model includes phenomena and crosscutting concepts from both biology and earth science, because those phenomena are always interacting on a global scale. As you build the model, you can use it to explore connections among causes and effects in global change.dd their icons to the model like you would assemble a puzzle.