LIFE STARTS WITH PLANTS From tiny patches of grass clinging to cliffs to giant trees as tall as towers plants are found all over the world If there is sunlight water and air plants can grow and some plants can exist with even less More than three hundred thousand different species of plants have been discovered Scientists believe that there are This juniper tree in Yosemite National Park in central California is able to grow on a rocky cliff 4
a great many more species that are still unidentified New plant species continue to be found in less explored areas of the world such as tropical forests Think About It New plants are often found in tropical forests Why do you think tropical forests have so many different plant species Most plants are rooted in one place and are not able to move around A stiff material called cellulose makes up their cell walls and gives them shape Through a process called photosynthesis plants create their own food In many many ways humans and animals depend on plants Without plants life as we know it could not survive on Earth Many animals like these impalas in Kenya graze on plants for their primary source of food 5
ENERGY SOURCE Plants are autotrophs This means that they create their own energy They do this through photosynthesis a process that requires sunlight chlorophyll water and carbon dioxide Chlorophyll is a substance naturally found inside green plants It allows plants to absorb energy from the sun With this energy plants Plants use photosynthesis to transform light energy from the sun into chemical energy 6
Most plants contain chlorophyll This natural substance is what gives green plants their color change the water in the soil and the carbon dioxide in the air into oxygen and nutrients The oxygen is released into the air Some of the nutrients are used and the rest are stored Photosynthesis is vital to life on Vocabulary Autotrophs are organisms that can make their own food from substances that do not come from other living things Earth Without photosynthesis there would be no plants and without plants there would be no food for humans and animals As producers that make their own food plants are the start of most food chains This means that nearly all living things depend on plants for energy 7
