Section 2: Resources

Nutrient Cycles Game — Card Explanations

Bacteria

"These tiny bacteria helped you, a nutrient, move from the soil to the roots of a plant. Move ahead 2 spaces."

This card helps students to think on a microscopic level about how nutrients are assimilated by plants from the soil. Nitrogen is an important example. Nitrogen as it exists in the air—nitrogen gas (N₂)—is un-useable in the living world. The forms that are useable are nitrate (NO₃) and ammonia (NH₃). Nitrogen-fixing bacteria that live in the soil and in the roots of certain plants (e.g., legumes) take in nitrogen gas molecules (N2) and transfer the nitrogen into ammonia molecules (NH₃). Nitrifying bacteria take in ammonia (NH₃) and transfer the nitrogen into nitrate molecules (NO₃). Nitrogen in these forms can then enter and be used by plants.

Because it is an essential function to help move nutrients through terrestrial ecosystems, the player-nutrients move two spaces.

"Microbes help you decompose. Move ahead 2 spaces."

This card also helps students think about how nutrients transfer on a microscopic level. Microbes include a diverse range of microscopic organisms, primarily from the Eubacteria and Archaea (bacteria and bacteria-like organisms) and Protists (mostly single-celled plant-like, animal-like, and fungus-like organisms). They play an essential role in decomposition by helping release nutrients.

Students get to move two spaces because microbes are ubiquitous and play a vital role in nutrient cycling.

Plants

"Sunshine! Through photosynthesis, these plants make their own nutrients. Move ahead 3 spaces."

"As a nutrient, you help these plants grow. Move ahead 3 spaces."

"April Showers! Along with carbon dioxide and sunlight, the rain helps these plants make sugar and oxygen. Eventually, these nutrients will be cycled through the ecosystem. Move ahead 3 spaces."

These cards help students to understand that plants play an important role in supplying ecosystems with nutrients. Plants are called autotrophs, which means "self-feeder." They create some of their own nutrients through photosynthesis. By using carbon dioxide, water, and light energy, they form sugar, oxygen and water (6CO₂ + 12 H₂O + Light energy → C₆H₁₂O₆ + 6O₂ + 6H₂O). The sugar acts as a primary source of matter and energy for the plant. Two primary ways in which plants provide nutrients to the ecosystem are by being consumed or through decomposition.

With this series of plant cards, students move three spaces to emphasize the important role that plants as primary producers to fuel nutrient cycling.

Animals

Large Mammals

"This big bear ate the berries you were in for breakfast. Move ahead 1 space."

"This deer ate the leaf you were in. Move ahead 1 space."

"Once you were a nutrient inside this little prairie dog. Now, you are stored inside a wolf's belly. Move ahead 2 spaces."

These cards help students think about one primary way that nutrients are passed through an ecosystem: consumption by herbivores, carnivores, and omnivores. When a bear, an omnivore, eats a berry, the berries' sugar, which contains carbon and other nutrients in the berry are passed to the bear. Similarly, when a deer, an herbivore, eats a leaf, the carbon and other nutrients inside the leaf are transferred to the deer.

These are both instances of primary consumption. Thus, they are worth only one space. When a wolf, a carnivore, eats a prairie dog, however, it is considered secondary consumption. Therefore, in the game, the player moves ahead 2 spaces, because more matter has been transferred between the prey and its predator.

"Children playing help leaves decompose. As a nutrient, the leaf you are in is one step closer to becoming part of the soil."

This card helps students understand that humans and other animals can help decomposition through mechanical processes such as playing in a leaf pile, walking through a forest, or by other physical means. Of all the processes that help nutrients cycle through decomposition, human impact is relatively small, compared to fungi or bacteria. Therefore, the card is only worth one space.

"This bear ate a lot of berries. He passed along what was left over, providing extra nutrients to the ecosystem. Move ahead 4 spaces."

"You were excreted by this deer. Move ahead 4 space."

These cards help students think about the effect of nutrients as they are digested and processed by animals and passed from the body as solid or liquid wastes. These wastes are loaded with nutrients that animals didn't use for growth and maintenance. Because animal wastes are nutrient-rich, this card is worth 4 spaces.

Note: Elimination is the process of passing solid wastes. Excretion is the process of passing liquid (nitrogenous) wastes.

Worms

"When this worm digested organic matter, it was broken up into the soil and nutrients were released. You became free to move around the ecosystem. Move ahead 1 space."

This card helps students to think about how the process of decomposition helps break up organic matter. When things decompose, nutrients are released. Because worms are so ubiquitous in rich soil, the encounter is worth two spaces.

Insects

"You took flight with this butterfly. Move ahead 1 space."

"As a tiny nutrient inside some pollen, you catch a free ride on these bees' antennae! Move ahead 1 space."

"This guy chewed you up and spat you out. Move ahead 2 spaces."

These cards help students to consider the role of insects in nutrient cycling. The card depicting the bee and the butterfly help students consider other physical ways that nutrients flow in an ecosystem: through bits of organic material stuck to animal carriers. Also, beetles and other insects play an important role in decomposition. In these ways, as well as by eating and generating wastes, insects help to facilitate nutrient cycling.

The number of spaces students move varies because the ways in which insects contribute to nutrient cycling varies. They play a large role in decomposition, but the movement of nutrients, which stick to the outside of their bodies, is relatively small.

Fungi

"You move from the soil to the inside of these fungi. Move ahead 1 space."

This card helps students to understand that fungi play a vital role in decomposition. Fungi are classified in their own kingdom. They acquire their nutrients by absorbing small organic molecules from their surroundings. Along with bacteria, fungi are the primary decomposers in ecosystems. Without fungi and bacteria, carbon, nitrogen, and other nutrients would remain unavailable for new generations of life.

Natural Disturbance

"Wildfire! Nutrients released during a small, natural fire. Move ahead 5 spaces."

This card helps students understand that wildfire is a natural part of the process of nutrient cycling in an ecosystem. Although large fires, such as the catastrophic 1988 fires in Yellowstone, can be so intense that nutrients may be lost, smaller fires actually help release nutrients. In cool temperate areas, decay is slow and logs, leaves, and needles pile up on the forest floor. Fire reduces this material to mineral-rich ash. Nutrients are released and recycled during this process. Fire also creates openings in the forest. Sunlight penetrates these gaps, warming the soil and stimulating new growth from seeds and roots.

Removal of Nutrients

"This mushroom was harvested and sent to the supermarket. Instead of decomposing on the forest floor, you'll be preserved in the mushroom, inside a cool grocery store. Lose a turn."

"Your forest was logged. As a nutrient inside a log, you were taken to a lumber mill instead of decomposing on the forest floor. Lose a turn."

This helps students think about what happens when natural resources are taken from an ecosystem. At the Hubbard Brook Experimental Forest in the White Mountains of New Hampshire, ecologists clear cut 15.6 acres of forest to test the effect of logging on nutrient cycling. They found that when plants are not available to regulate the flow of nutrients (and are removed with their nutrient stored) nutrients are lost from the ecosystem.

Although the biomass of fungi harvested by humans is far less than the biomass of trees, the same things happen on a smaller scale. That is, since fungi play an essential role in decomposition, when they are taken from an ecosystem, those nutrients that would otherwise be released are kept in unusable forms for the rest of the ecosystem.