s8pe-fmup-CA10-CA19
12/19/05
3:19 PM
MAZER
Page CA19
of Life Science
All living things share common characteristics.
Despite the variety of living things on Earth, there are certain characteristics common to all. The basic unit of life is the cell. Any living thing, whether it has one
cell or many, is described as an organism. All organisms are characterized by
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organization—the way the organism’s body is arranged
growth––the way that an organism grows and develops over its lifetime
reproduction—the way that an organism produces offspring like itself
response—the ways an organism interacts with its surroundings
All living things share common needs.
All living things have three basic needs: energy, materials, and living space. These
needs must be met for the organism to stay alive. Energy enables an organism
to carry out all the activities of life. The body of every organism needs water and
other materials. Water is important because most of the chemical reactions in a
cell take place in water. Organisms also require other materials. Plants, for example, need carbon dioxide to make energy-rich sugars, and most living things
need oxygen. Living space is the environment in which an organism gets the
energy and materials it needs.
Living things meet their needs through interactions
with the environment.
The environment is everything that surrounds a living thing. This includes
other organisms as well as nonliving factors, such as rainfall, sunlight, and soil.
Any exchange of energy or materials between the living and nonliving parts
of the environment is an interaction. Plants interact with the environment by
capturing energy from sunlight and changing that energy into chemical energy
that is stored in sugar. Animals can interact with plants by eating the plants and
getting energy from the sugars that plants have made.
The types and numbers of living things change over time.
A species is a group of living things so closely related that they can produce
offspring together that can also reproduce. Scientists have named about 1.4
million different species. The great variety of species on Earth today is called
biodiversity. Different species have different characteristics, or adaptations,
that allow the members of that species to get their needs met in a particular
environment. Over the millions of years that life has existed on Earth, new
species have come into being and others have disappeared. The disappearance of a species is called extinction. Studying fossils of extinct organisms
is one way that scientists have of seeing how living things have changed
over time.
Unifying Principles CA19
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