Energy from the Sun Running kicking a ball singing reading a book sleeping all these activities require energy Your brain needs energy to think your heart needs energy to beat and your lungs need energy to breathe In fact all living organisms need energy for ten major processes 4
10 Life Processes Together these processes are called an organism’s metabolism Growth life is always growing and developing Absorption transporting materials through membranes Reproduction creating more organisms of your own species Digestion grinding up and using food substances Excretion releasing wastes from the organism Response to stimuli responding to changes in the environment Movement even plants move Assimilation building new materials from nutrients Respiration breathing Circulation distributing fluid such as blood throughout the body Touch Me Not Plants can move just like all other living creatures but it’s usually too slow for a person to see Not so with the touch-me-not or bashful plant Mimosa pudica When someone touches or shakes the leaves of this plant it immediately folds up and droops Scientists believe the plant is trying to protect itself from harm After a few minutes the leaves reopen 5
People get that energy from food including plants and animals Animals get their food from other animals or from plants Plants are the source of all other creatures energy but where do plants get their energy They get it from food too but they make it themselves Think back to when you observed the sun’s rays shining through a window or a cloud Imagine if you could take a big bite out of those sunbeams In a sense you do that every time you eat Plants make food using energy from the sun and that same energy eventually makes its way to us in our food 6
Plants must have light to make Growing Toward the Light energy If they are growing in a place with limited amounts of light the plant will actually grow toward the light source This phenomenon is called phototropism You can watch it in action if you plant a seed in a pot and set it just out of reach of the window The new plant will grow toward the window to get the light it needs It starts with the sun’s rays Those rays are actually waves of light and heat coming into the atmosphere Energy that travels in waves is called radiant energy The sun is Earth’s main source of radiant energy But people’s bodies cannot use that energy in its raw form Plants convert and store solar energy into atoms and link them together into molecules These molecules contain stored energy When molecules are mixed together the chemical reactions that result release chemical energy the plant can use 7
