Interactions and Interdependence
¨ Ecology is the scientific study of interactions among organisms and between
organisms and their environment, or surroundings.
¨ The word ecology is based on the Greek
word oikos, meaning house, which is also the root word for economy.
¨ The living world was perceived as a household with an economy in which each organism
plays a role.
¨ The “houses” comes in many sizes—from single cells to the entire
¨ The largest “house” is the biosphere.
¨ The biosphere contains the combined portions of the planet in which all of life exists, including
land, water, and air, or atmosphere.
¨ It extends 8 kilometers above and below the Earth’s surface.
¨ Interactions within the biosphere produce a web of interdependence between organisms
and the environment in which they live.
Levels of Organization
¨ The study of ecology ranges from the study of individual organisms
to populations, communities, ecosystems, biomes—and finally, to the entire biosphere.
Five Levels of Organization
1. Species is a group of organisms so similar to one another that they can breed and produce fertile offspring.
2. Populations are groups of individuals
that belong to the same species and live in the same area.
3. Communities a group of different
populations that live together in a defined area.
4. Ecosystem is a collection of all organisms
that live in a particular place, together with their nonliving, or physical, environment.
5. Biome is a group of ecosystems
that have the same climate and similar dominant communities.
¨ Ecologists use a wide range of tools and techniques to study the
¨ Scientists conduct modern ecological research using three basic
¨ Observing is the first step in asking ecological questions.
¨ The questions like:
a) What species live here?
b) How many individuals of each species are there?
¨ Experiments are used to test a hypothesis.
¨ An ecologist might set up an artificial environment in a lab to imitate and manipulate
conditions that organisms would encounter in the natural world.
¨ Because many ecological phenomena occur over long periods of time,
ecologists make models to gain insight into complex issues such as the effects of global warming on ecosystems.
¨ The models consist of mathematical formulas based on data collected
through observation and experimentation to make predictions about the future.