Chapter 2, Section 1
Sources of Energy
The process by which a cell captures energy in sunlight and uses it to make food is called photosynthesis (foh toh sin thuh sis). The term photosynthesis comes from the Greek words photo, which means “light,” and synthesis, which means “putting together.”
Nearly all living things obtain energy either directly or indirectly from the energy of sunlight captured during photosynthesis. Grass obtains energy directly from sunlight, because it makes its own food during photosynthesis. When the zebra eats the grass, it gets energy that has been stored in the grass. Similarly, the lion obtains energy stored in the zebra. The zebra and lion both obtain the sun’s energy indirectly, from the energy that the grass obtained through photosynthesis.
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Figure 1Energy From the Sun The sun supplies energy for most living things, directly or indirectly. Relating Cause And Effect How does sunlight provide food for the zebra?
Plants manufacture their own food through the process of photosynthesis. An organism that makes its own food is called an autotroph (awt oh trahf). An organism that cannot make its own food, including animals such as the zebra and the lion, is called a heterotroph (het ur oh trahf). Many heterotrophs obtain food by eating other organisms. Some heterotrophs, such as fungi, absorb their food from other organisms.
Figure 2Autotrophs and Heterotrophs Grass, which makes its own food during photosynthesis, is an autotroph. Zebras and lions are heterotrophs, because they cannot make their own food.
For: The Photosynthesis Process
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