Principles of Ecology

Ecology is the study of interactions that take place between organisms and their environment. Ecological research combines info and techniques from many scientific fields.

Living things are found in the air, on land and in the waters of earth. The biosphere is the portion of earth that supports living things. The biosphere extends from high in the atmosphere to the bottom of the oceans.

The nonliving parts of an organisms environment are the abiotic factors. Ex. Air currents, temperature, moisture, light and soil. Abiotic factors in an environment affect living things and can effect which organisms survive.

Biotic factors are all the living organisms that inhabit an environment. All organism depend on others in some way. Ex. Food, shelter, reproduction, protection

Ecologists have organized the living world into levels: The organism by itself Populations Communities Ecosystems

A population is a group of organisms, all the same species, which can interbreed and live in the same area at the same time. How organisms share the resources can determine how far apart they live and their number.

A biological community is made up of interacting populations in a certain area at a certain time. A change in one population can cause a change in another.

An ecosystem is made up of interacting populations in a biological community and the community’s abiotic factors. There are terrestrial (land) ecosystems and aquatic(water) ecosystems.

A habitat is the place where an organisms lives out its life. Habitats can change and even disappear. Can you think of examples?

A niche is all strategies and adaptations a species uses in its environment How it meets its specific needs for food and shelter How and where it survives and reproduces.

Symbiosis is the relationship in which there is a close and permanent association between organisms of different species. There are three kinds: mutualism, commensalism and parasitism.

Mutualism occurs when two species of organisms benefit from living in close association. Can you give examples?

Commensalism occurs when one species benefits and the other is neither harmed nor benefited. Can you give examples?

Parasitism occurs when one species is harmed while the other is benefited. Can you give examples?

The ultimate source of energy is the sun. Plants use the sun’s energy through a process called photosynthesis. An organism that makes its own food is called an autotroph.

An organism that cannot make its own food and feeds on other organisms is a heterotroph. These are called consumers and are either herbivores, carnivores or omnivores.

Some heterotrophs are scavengers and don’t kill for food but rather eat animals that have already died. Some organisms are decomposers and break down and release nutrients from dead organisms.

Matter flows through the levels of the ecosystem from producers to consumers. Trapped energy is also transferred from one level to the next and some is lost as heat.

Food chains are one way to show how matter and energy flow through an ecosystem. This is done using arrows to show the direction that energy travels from one organism to the next.

Each organism in a food chain represents a feeding step or trophic level. A first order heterotroph feeds on plants(ex. Grasshopper), while a second order heterotroph feeds on a first(ex. Bird that eats grasshoppers.

Food webs are more complex and show all the possible feeding relationships in a community. Food webs are more realistic and represent a network of interconnected food chains.

Ecological pyramids are another way to show how energy flows through an ecosystem. The pyramid of energy shows how the amount of available energy decreases at each trophic level.

Unlike energy matter is cycled through ecosystems rather than replenished by the sun. The atoms of carbon, nitrogen and others elements in living matter has been here since life began.

The water cycle not only recycles water but it purifies it as well, as only pure H2O is evaporated from areas that have impure water.

Carbon is the building block of the molecules of life and cycles from CO2 to autotrophs to heterotrophs and back to CO2 again through a variety of pathways.

Nitrogen is necessary for many molecules of life including amino acids and proteins. It cycles from gases to complex biomolecules back to gases.

All living organisms need phosphorus for growth and development All living organisms need phosphorus for growth and development. Plants obtain it from the soil. Animals obtain it by eating plants. It cycles either by decomposing animals returning it to the soil(short-term) or by being incorporated into rock and eventually releasing it back to the soil(long-term).