burgeoned, they liberated vast quantities of
oxygen (O 2 ), which radiation in the upper
atmosphere converted to ozone (O 3 ), which in
turn absorbed ultraviolet light and prevented
much of it from reaching the earth’s surface.
Land life was now possible.
The challenging life of the plant. Plants are
rooted to one spot in the earth, where they
absorb water and minerals from the soil,
carbon dioxide and oxygen from the air, and
light energy from the sun, and transform these
inorganic materials into plant tissues — and
into nourishment for insects and other
animals. Plants defend themselves against
predators with a variety of chemical weapons,