Lesson Goal

During the lesson "Life in the Earth System," students will use models to illustrate the relationships between components of living and nonliving systems.

NGSS Standards

Properties of Systems

A system is a set of interacting components (or parts) considered to be a distinct entity for the purpose of study or understanding. Systems exist on all scales, from atoms to the universe, and can be living or nonliving.

Inputs and Outputs

The inputs and outputs of different types of systems include energy, matter, and information. Outputs are generated when the inputs are processed in some way. In the case of a cellular phone, a radio signal (an input) is converted to vibrations (an output) that you detect as sound.

Open and Closed Systems

Systems can be categorized according to the flow of inputs and outputs. In an open system, the inputs and outputs flow into and out of the system. In a closed system, the flow of one or more inputs and outputs is limited in some way. An isolated system is a system in which all of the inputs and outputs are contained within the system.

Controls

The components of a system include the controls that help keep the system working properly by monitoring and managing the inputs and outputs. Controls can be automatic, manually set, or a combination of both. An important system control is feedback. Feedback is information from one step of a cycle that acts to change the behavior of a previous step of a cycle. So, feedback is output that becomes input. A feedback loop is formed when an output returns to become an input in the same system that generated the output.

System Organization

Systems can range in size and in complexity. More complex systems generally have more levels of organization than simpler systems. For example, organisms, or living things, are systems made up of smaller systems, such as organs, tissues, and cells. Two organisms that interact also can make up a system, such as a bird that pollinates a plant. On a larger scale, you are a system that is part of an ecosystem, or a community of organisms, and their physical environment. You also are part of the larger Earth system.

EXPLAIN The scuba diver is a living system. The scuba gear, or self-contained underwater breathing apparatus, is a system of air exchange. How are these two systems interacting? What are the inputs and outputs of these systems?

Put your best explanation for how these two systems interact in the padlet below.

System Models

Suppose that an engineering team is designing a new airplane. If they were to build a full-sized airplane for a performance test of each different design, the cost and the time would be impractical. A more practical option would be to use a smaller scale model of the airplane to study and analyze the various components of the system. A model is a pattern, plan, representation, or description designed to show the structure or workings of an object, system, or concept. You might think of a model simply as a smaller scale physical representation of a larger system. However, models are not limited to physical objects. Other types of models include computer simulations, conceptual diagrams, and mathematical equations, as shown in the Types of Models table.

Systems Biology

We can apply systems thinking to biology. Systems biology studies biological systems as an integrated whole. This approach allows scientists to consider biological phenomena at different scales and examine how the components of a biological system interact. By considering the larger picture, biologists are better able to identify emergent properties of the system. An emergent property is a property that a system has but that its component parts do not have, that is, the sum is greater than its parts. For example, cells are self-contained systems that can function independently. However, when combined, similar cells form tissues, which can perform functions that the individual cells could not.

Language is a more recognizable example of a system with emergent properties. Its basic components are the sounds that combine to form words. The emergent properties are the meaning of the words made from these sounds. Another level of emergent properties comes from combining words into sentences that can convey meaning the words cannot do individually.

Similarly, DNA is a molecule that carries the genetic code of all organisms. The code consists of just four bases represented by the letters A, T, G, and C. The sequence of these bases in DNA provides coded instructions for making thousands of different proteins. Each protein is made of a specific arrangement of amino acids coded for by DNA. The emergent property of DNA is the information that codes for proteins.

To understand living things better, we can study the systems in which they live. One of these systems is our home planet—Earth. The Earth system includes all of the solids, liquids, and gases; all living and nonliving objects; and all of the different forms of energy within Earth’s boundary. Earth is made up of smaller systems, such as the biosphere, where all living things exist and interact. The biosphere in turn includes many smaller subsystems of living things in both aquatic and land environments. Earth itself exists within larger systems, such as the solar system and the Milky Way galaxy.

Matter stays within the Earth system, but energy enters the system in the form of sunlight and exits in the form of heat. In the Earth system, light energy is converted into other forms of energy. This drives the transformations of matter from one form to another as it cycles through the system.

Organization of the Earth System

Scientists use a system model to better understand interactions within the Earth system. The Earth system is organized into five interconnected systems, or spheres: geosphere, hydrosphere, biosphere, atmosphere, and anthrosphere.

The geosphere is all the solid features of Earth’s surface, such as mountains, continents, and the seafloor. It also includes everything below Earth’s surface. The hydrosphere is all of Earth’s water, including water in the form of liquid water, ice, and water vapor. The biosphere is the area of Earth where life exists. The atmosphere is all of the air that envelops Earth’s solid and liquid surface. The anthrosphere is the portion of Earth’s environment that has been constructed or modified by humans.

Ecologists can study ecosystems at different scales. They may study an individual organism, such as a mule deer, to learn more about factors that affect that species. They may also study an entire population of mule deer. A population is a group of the same species that lives in the same area. Multiple populations of different species form a community. In the Sierra Nevada, an ecologist may study how a community of mule deer, Belding’s ground squirrels, and birds in a certain giant sequoia grove interact with one another.

Not all ecosystems are terrestrial, or land-based. About 71 percent of Earth’s surface is covered with water, and it, too, is home to living organisms. These water-based ecosystems are called aquatic ecosystems. There are two main categories of aquatic ecosystems: salt water, or marine, and fresh water.

A biome is a major regional or global distribution of organisms, characterized by specific climate conditions and plant communities. There are several different types of biomes. The plants and animals of each biome are adapted to living in that particular environment. Many different ecosystems make up a biome, and each ecosystem has specific biotic and abiotic factors that interact and are interdependent.

Characteristics of Living Things

Scientists use a set of characteristics to define living things. In general, all living things are made up of one or more cells and require an energy source. Living things grow and change over time and reproduce by making copies of themselves or by having offspring. Living things also respond to changes in their environment. Homeostasis is the maintenance of constant internal conditions in an organism. Although temperature and other environmental conditions are always changing, the conditions inside organisms usually stay quite stable. Maintaining stable internal conditions is critical to an organism’s survival.

Homeostasis within an ecosystem requires that all components have a dynamic interaction with each other. Removing one of the components can disrupt the balance that exists within the ecosystem.

On the Padlet below, rearrange the predators, prey and food sources and connect all components of the Yellowstone ecosystem.

Take the quiz below to evaluate your knowledge of systems.