Texas Science Teacher Resource Hub

💡 What This Standard Actually Means

An ecosystem is alive with energy and matter flowing through it. The Sun pours energy onto plants every day. Plants use that energy to grow. A grasshopper eats the plant and now the energy and matter from that plant are inside the grasshopper. A bird eats the grasshopper. A hawk eats the bird. When the hawk eventually dies, decomposers like fungi and bacteria break the body down and return the matter to the soil, where new plants can use it again. That's the basic flow of a healthy food web: energy moves up the chain (and is mostly lost as heat at each step), matter cycles around in a loop.

This standard asks students to predict what happens when the ecosystem changes. The change can be all kinds of things: a long drought that kills lots of plants, a new species that eats the same food as a native species, a wildfire that wipes out a forest, a disease that kills frogs in a pond, a hurricane that floods a marsh. Whatever the change is, it disrupts the food web, and that means the energy flow and matter cycling change too.

If a drought kills off most of the plants in a meadow, less energy enters the food web from the Sun. Grasshoppers don't have enough food. Birds don't have enough grasshoppers to eat. Hawks don't have enough birds. Less matter cycles through the system because there's less plant material to start with. If a new predator gets introduced and starts eating frogs, the energy and matter that used to flow into the frogs now flows into the predator. Other animals that ate frogs might starve. Insects that frogs ate might explode in numbers. The takeaway: any change ripples through the entire web, changing how matter cycles and how energy flows. Kids should be able to take a food web diagram, change one thing, and trace the effects through the whole web.