Ecosystems Study Guide 1
Characteristics of Systems
System Parts:
 A system is a group of parts that work together as a unit. A system also has cycles
and processes that interact, or affect each other.
 Everything in a yard, including the house, plants, people, animals, hose, sprinkler,
and water, is part of a system. The people, plants, and animals are the living parts
of the system. The rest of what makes up a yard are the nonliving parts of the
system. Both the living and nonliving things play important roles in keeping the
yard system working right.
 The edges of the yard system are easy to see. It is easy to say what is inside and
what is outside the system. The edges of many natural systems aren’t so each to
see. Often, scientists must decide where the edges of a natural system will be for
the purposes of their studies.
 The parts of a system interact with other parts of the system. Most systems also
interact with the outside.
 The yard system is an open system because it takes in things called inputs from
outside the system. Energy from the sun is one input. Water is also an important
input. The water may come in the form of rain or from the city’s water supply.
 Open systems also let things out. Outputs are things that leave a system. One
output from the yard system is water. Some of the water in the yard runs off into
the street. Some evaporates into the air.
 The opposite of an open system is a closed system. A closed system has no inputs
or outputs. Very few systems are really closed. Most have some connection to the
Stability and Change
 All systems follow patterns of changes. You sometimes must look to see these
patterns because they occur over time. In a yard the cycle of periods of sunshine
and periods of shade each day is a pattern. They cycle of being wet and being dry
is another pattern. Patterns show a kind of stability.
 Stability means that over time the changes in a system cancel each other out. For
example, if something is added, it is later taken out. The system stays in balance.
 Stability is important because almost all natural systems have it. The yard system
has stability. The sun shines in part of the yard each morning. In the afternoon
that part is shady. The grass may dry out after a few days without rain, but
eventually it gets water from rain or from a sprinkler.
(Harcourt Science B6-B9)