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Unit Concept Map and
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Ideal Student Response Central Question: How do plants get their food? What is food for plants?
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| Just like all living things plants need food. Food is what provides living things with the energy to live and grow. Some things we sometimes call food really don't provide energy for living things, so they really aren't food. Like water. Living things need water, but it does not provide them with their energy. It is not food. So plants need to get energy but they don't get it from water. They get their food in a very different way than animals (including humans). Animals have to take food into their bodies. But plants can do something that animals/humans cannot. They can make food inside of their bodies. | |
This is how plants make their food inside themselves. |
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They take in carbon dioxide (from the air) through the holes in their leaves, and water through their roots. The carbon dioxide and water travel inside the plant to cells in the leaf. The leaf is made up of many cells, and some of these cells are the places where the plant makes food. These cells need the water and carbon dioxide and also sunlight to make the food. Sunlight provides the energy for this chemical reaction. Chlorophyll is the green pigment in leaf cells that can catch the sun’s light and use it for changing carbon dioxide and water into energy-containing food. This is the only substance that can catch light energy and use it to change light energy into energy stored in food. Humans cannot make their own food because we do not have things that plants have such as chlorophyll. The carbon dioxide and water are transformed into a totally new substance that contains energy -- it is food in the form of sugar. Because a totally new substance is made, this process is an example of a chemical change. This chemical change that happens inside plants is called photosynthesis. It is a very complicated process and scientists still do not completely understand it. After the food is made in the leaf cells, it has to travel all over the plant to feed all the cells in the plant. The whole plant is made up of cells and each cell needs food to live. So food travels through the veins in the plant to all the cells. Sometimes a plant makes more food than it can use right away. So it stores food in what we call fruits and vegetables (like the carrot, potato, apple). Food also gets stored in the seeds. Then when the seed falls off the plant and lands in a good spot where it gets water, the embryo inside the seed can start to grow using food stored in the seed's cotyledon. That food came from photosynthesis done by the mother plant! When the embryo has used all the food up in the cotyledon, it has to start making its own food (photosynthesis). A seed can start to grow in the dark because it can use food stored in the cotyledon, but it needs light to stay alive so that it can make its food. |
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