1 Foundations of Ecology
Learn how ecology connects organisms, interactions, and environmental conditions across levels of biological organization.
and the Environment
is the scientific study of relationships between organisms and their environments. An environment includes , or living things such as food sources and predators, and , or nonliving conditions such as water, light, temperature, and soil.
These components affect one another. For example, a plant depends on sunlight and soil moisture to grow, and its growth may provide food or shelter for other organisms. Organisms are shaped by their surroundings and can also change them.
Levels of Ecological Organization
Ecologists organize questions by scale, from individual organisms to all the places where life exists. These levels are connected rather than isolated: changes at one level can affect others.
Organism: An individual living thing. A cactus’s water-storing tissues, for example, help it survive in a dry habitat.
: Individuals of the same species living in the same area. All rabbits living in one grassland form a .
: All populations of different species living and interacting in an area. A grassland may include rabbits, grasses, hawks, insects, and fungi.
: A and the abiotic environment with which it interacts. A grassland includes its organisms as well as soil, air, water, sunlight, and local climate.
: The parts of Earth where life exists, encompassing all of Earth’s ecosystems.
For example, a change in rainfall can alter plant growth, which may then affect herbivore populations and the wider . Takeaway: Each larger level includes relationships among the components within it.
Interactions Among Organisms
Organisms interact with members of their own and other species. Individuals may compete for limited resources such as food, water, or nesting sites. Interactions between species include:
: One organism consumes another.
: An animal eats a plant or alga.
: One organism benefits while harming its host.
: Organisms use an overlapping limited resource.
: Both partners benefit. A pollinator, for instance, gets food from a flower while helping transfer pollen.
Environmental conditions also influence where organisms can live and how well they survive and reproduce. Because organisms both respond to and alter their surroundings, ecological relationships are reciprocal.
Putting the Levels Together: A Pond
A pond shows how ecological levels fit together. An individual frog is an organism, while all frogs of one species in the pond make up a . Frogs, algae, insects, fish, and other species together form the . The pond also includes such as water temperature, dissolved oxygen, sunlight, and sediment.
If water conditions change and insect numbers fall, frogs may have less food. This example connects an abiotic change to interactions among species and effects on populations. Takeaway: Understanding an means considering both its living and its nonliving environment.