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Tracing the flow of energy from the sun through different living things.
Did you know that the sandwich you ate for lunch is actually 'recycled' sunlight? Every single bite of food you take connects you to a giant energy puzzle that starts millions of miles away in space!
Every food chain starts with the sun. But animals can't just stand in the sunshine to get full! Only producers—like plants, algae, and some bacteria—can turn sunlight into food. They use a process called photosynthesis. Think of producers as the 'chefs' of nature; they take raw ingredients like sunlight, water, and air to cook up energy-rich sugar. Without producers, no other living thing could survive because they are the only ones who can 'trap' the sun's energy for everyone else to use.
Quick Check
Why is a sunflower considered a producer?
Answer
Because it uses sunlight to create its own food through photosynthesis.
Since animals cannot make their own food, they must eat plants or other animals. These organisms are called consumers. Scientists group them by what they eat: Herbivores eat only plants (like cows), Carnivores eat only meat (like wolves), and Omnivores eat both (like humans!). In a food chain, energy moves from the 'eaten' to the 'eater.' We use an arrow to show this. For example, means the energy is moving into the rabbit.
Let's look at how energy moves in three steps: 1. Producer: Green Grass (takes energy from the sun). 2. Primary Consumer: Grasshopper (eats the grass). 3. Secondary Consumer: Bluebird (eats the grasshopper). The chain looks like this: .
Quick Check
If a frog eats a fly, which way does the arrow point in a food chain diagram?
Answer
The arrow points from the fly to the frog ().
What happens when a plant or animal dies? The energy doesn't just vanish! Decomposers, like fungi (mushrooms) and bacteria, go to work. They break down dead things and waste into nutrients. These nutrients go back into the soil, helping new producers grow. It is the ultimate recycling system! While a food chain looks like a straight line, it is actually part of a never-ending cycle of energy.
Energy is lost at every step of the chain. Only about of the energy an animal eats is stored in its body to be passed to the next animal. 1. If a plant has units of energy... 2. The deer that eats it only gets units (). 3. The wolf that eats the deer only gets units (). This is why there are usually fewer lions than there are blades of grass!
In the real world, most animals eat more than just one thing. A squirrel eats seeds, but it also eats nuts and fruit. A fox might eat a squirrel, but it also eats mice or birds. When you connect all the overlapping food chains in one area, you get a food web. A food web is a complex map that shows how all living things in an ecosystem are connected. If one part of the web changes—like if all the bees disappear—it can affect every other animal in that web.
Imagine a pond food web. What happens if the large fish are removed? 1. The small fish (which the large fish used to eat) will increase in number. 2. These many small fish will eat all the tiny water insects. 3. Without insects to eat the algae, the pond becomes covered in green slime. This shows how one change can 'ripple' through the entire web!
Which of these is always at the very beginning of a food chain?
What do the arrows in a food chain represent?
A food web is just a collection of many overlapping food chains.
Review Tomorrow
Tomorrow morning, look at your breakfast and try to name the producer, the consumer, and the path the energy took to get to your plate.
Practice Activity
Draw a food web for your backyard or a local park. Include at least one producer, two consumers, and a decomposer like a mushroom!