The Biosphere, Ecosystems, and Communities

Ecology is the scientific study of interactions among organisms and between organisms and their environment.
It helps us understand and control our interactions with the environment.

Species; populations; communities; ecosystem; biome.

They produce a web of interdependence between organisms and the environment in which they live.

They are essential to the flow of energy through the biosphere.

They capture energy from sunlight or chemicals and use that energy to produce food. It fuels the assembly of simple inorganic compounds into complex organic molecules which combine and recombine to produce living tissue.

Photosynthetic organisms use light energy to power chemical reactions that convert carbon dioxide and water into energy-rich carbohydrates and oxygen.
Chemosynthetic: Produce food relying on energy within chemical bonds of inorganic molecules.

Producers and then consumers.

Each step in a food chain is called a trophic level.

A food web links all the food chains in an ecosystem together.

An ecological pyramid shows the relative amounts of energy or matter contained within each trophic level in a food chain.

Biomass is the total amount of living tissue within a given trophic level. A biomass pyramid represents the amount of potential food available for each trophic level in an ecosystem.

The numbers of individual organisms at each trophic level.

When water molecules evaporate from the ocean or a lake, or are transpired from trees, they enter the atmosphere as water vapor. The water vapor condenses and returns to earth as precipitation. Much of the water enters a river that carries the runoff or seeps into the ground and is taken up through the roots.

All living things require water to survive.

In the atmosphere, carbon is present as carbon dioxide. Plants take it in through photosynthesis or it is found in the ocean. Sometimes animals feed on carbon and then respire it into the environment. Sometimes, decomposed plants depose carbon into fossil fuels, which are then burned through human activity. Sometimes, photosynthesis and decomposition occur in the ocean, leading to carbonate rocks which are then uplifted and erode or cause volcanic activity. It may also lead to feeding and respiration.

Carbon is a key ingredient of living tissue and rocks. It is an important component of the atmosphere.

Nitrogen in the atmosphere may go to the ground, where it is fixated by bacteria and turns into NH3. NH3 may be taken up by producers or turn into NO3- and NO2-, which are then taken by producers, used by consumers, excreted, and return to NH3. NO3- and NO2- may also undergo denitrification and return to the atmosphere.
Atmospheric nitrogen may also enter fertilizer, where it is taken up by producers, reused by consumers, and then excreted into NH2.
Atmospheric nitrogen may also undergo nitrogen fixation and turn into NO3- and NO2-.

All organisms require nitrogen to make amino acids, which are used to build proteins.

Phosphorous heads from sediments to the ocean to the land to organisms and back.

Phosphorous forms part of important, life-sustaining molecules such as DNA and RNA.

A nutrient that cycles slowly through the environment and limits it.

Trapping of heat by atmosphere; latitude; transport of heat by winds and oceans; precipitation; shape and elevation of land.
It is important because species vary in their tolerances for climates outside their normal range.