Key Concept 1: Organisms interact with both living and nonliving
things to survive in their ecosystems.
An ecosystem is a community of living and nonliving things in their
environment.
The living or biotic components of an ecosystem are: the plants, animals
(including humans), fungi, and microorganisms living within a particular
geographic area. For example, in a desert, the cactus, sagebrush, desert grasses,
wildflowers, coyotes, snakes, lizards, desert mice, birds, scorpions, bacteria, etc,
represent the living part of a desert ecosystem. The living parts of an
environment provide a source of food, a way to reproduce, and protection. For
some creatures, other living things may be their habitat (home) or their social
group. When other organisms are competitors or predators, that living part of
the environment becomes a survival challenge. As energy from the Sun is
transferred from producers to consumers and finally to decomposers, all of
nature becomes interdependent. The study of human impact on living things has
led to eco-friendly or “green” practices to lessen the harmful effects of human
activity and technology on ecosystems.
Living things can be studied at increasing levels of interaction: the response of
a single organism, a population of similar organisms, or a community of different
organisms that live together in an ecosystem.
The nonliving or abiotic components of an ecosystem are: sunlight, atmosphere
and weather, temperature, soil, rock, landforms, bodies of water, glaciers,
volcanoes, man-made structures, etc. For example, in a desert, the sand, Sun,
lack of water, rocks, hot air, etc., represent the abiotic elements in that
ecosystem. The nonliving parts of an environment supply the sunlight, water,
oxygen, carbon dioxide, nitrogen, minerals, and shelter necessary for life.
Nonliving elements can also present survival challenges when they threaten life
such as flooding, drought (dry spells), or pollution caused by human activity.
Life within an ecosystem is interdependent. A delicate balance exists in nature
so that all living things must interact with other organisms and with their
environment in order to survive and reproduce. As energy from the Sun is
transferred from producers to consumers and finally to decomposers, all of
nature becomes interdependent. Any change to a single component in that
ecosystem can have profound impact on the entire ecosystem.
Key Concept 2: Plants interact with living things such as animals and
other plants in complex ways and also require nonliving things, such
as carbon dioxide, water, and sunlight.
Plants need nonliving things to survive such as carbon dioxide in the air,
sunlight from above, and water brought up by their roots to survive.
Through the process of photosynthesis, plants, as producers, change
sunlight, carbon dioxide (produced by animals), and water to make
glucose or plant food. As a by-product, plants release oxygen which
animals need.
Plants interact with living things. Energy, minerals, and nutrients stored
in plants are transferred to the animals when plants are eaten. Animals
like insects or birds also pollinate flowers by spreading pollen grains that
fertilize plant seeds. Animals also end up spreading seeds that get stuck
to their fur or inside fruit carried off to be eaten and left on the ground.
These loose seeds end up taking root under the right conditions and
grow new plants and flowers.
Key Concept 3: Animals depend on other living things, such as plants
and other animals, and nonliving things, such as air and water, to
survive.
Animals breathe the oxygen in the air produced by plants. Animals use
this oxygen carried in blood to cells and exchanged for carbon dioxide
which is released (which plants will use). Animals also depend on other
nonliving elements for survival such as water, the correct temperature
from the Sun, and soil/rocks/landforms for shelter. The energy, minerals,
and nutrients stored in plants are transferred to the animals when plants
are eaten. Some plants provide more than food for animals; plants can
also serve as shelter. For example, tree trunks or flowers can become a
habitat for birds, mammals, or insects.
Animals that depend on different kinds of living things for food are
grouped into herbivores (animals that eat plants), carnivores (animals
that eat other animals), omnivores (animals that eat both plants and
animals), and decomposers (bacteria and fungi that break down dead
organisms for food). Animals that hunt other animals are called predators.
Animals that are hunted are called prey.