Ecosystems maintain themselves by cycling energy and nutrients obtained from external sources. At the first trophic level, primary producers (plants, algae, and some bacteria) use solar energy to produce organic plant material through photosynthesis.

ENERGY FLOW THROUGH ECOSYSTEM

EXAMPLE OF ENERGY FLOW THROUGH AN ECOSYSTEM

The low rate of energy transfer between trophic levels makes decomposers generally more important than producers in terms of energy flow. Decomposers process large amounts of organic material and return nutrients to the ecosystem in inorganic form, which are then taken up again by primary producers.

LAWS OF THERMODYNAMICSthe four laws of thermodynamics define fundamental physical

quantities (temperature, energy, and entropy) that characterize thermodynamic systems.

ZEROTH LAWThe law is intended to allow the existence of an empirical parameter, the temperature, as a property of a system such that systems in thermal equilibrium with each other have the same temperature.FIRST LAWThe first law of thermodynamics may be stated in several ways:

The increase in internal energy of a closed system is equal to the heat supplied to the system minus work done by it.

SECOND LAWThe second law of thermodynamics asserts the irreversibility of natural processes, and the tendency of natural processes to lead towards spatial homogeneity of matter and energy, and especially of temperature.

EXAMPLE OF TROPHIC STRUCTURE

THIRD LAW the third law of thermodynamics is sometimes stated as follows:The entropy of a perfect crystal of any pure substance approaches zero as the temperature approaches absolute zero.At zero temperature the system must be in a state with the minimum thermal energy.

TROPHIC STRUCTURE

The Ocean / Biotic Structure » Trophic LevelsAll organisms in an ecosystem can be placed in trophic levels depending on what energy source they rely upon and how they provide energy for other organisms in the food web. With the exception of life near hydrothermal vents in the deep ocean, life is always dependent directly or indirectly on the energy from the sun.

ENERGY FLOWThe food chain consists of trophic levels, or the levels within the food chain in which energy is transformed. Due to basic principles of thermodynamics, energy is always lost to the environment any time an organism at one trophic level uses the energy from the trophic level below.

Food chain in a Swedish lake. Osprey feed on northern pike, which in turn feed on perch which eat bleak that feed on freshwater shrimp.A food chain is a linear sequence of links in a food web starting from species that are called producers in the web and ends at species that are called decomposers in the web. A food chain also shows how the organisms are related with each other by the food they eat.

FOOD CHAIN

EXAMPLE OF FOOD CHAIN

FOOD WEB

A food web (or food cycle) is the natural interconnection of food chain and generally a graphical representation (usually an image) of what-eats-what (a finella) in an ecological community. Another name for food web is a consumer-resource system.

EXAMPLE OF FOOD WEB

ENERGY TRANSFERS AND EFFICIENCY

Energy cannot be created or destroyed but it can be transformed from one form to another.When energy is transferred by an appliance the energy is converted from one form to another.  Some of the energy will be usefully transferred by the device and some will be wasted (transferred to a non-useful form). Eventually all the energy will go to warming up the surroundings, there is still the same amount of energy as you had at the start but because it is spread out it is more difficult to use.

ECOLOGICAL SUCCESSION

Ecological succession is the observed process of change in the species structure of an ecological community over time. The time

scale can be decades (for example, after a wildfire), or even millions of years after a mass

extinction.

The community begins with relatively few pioneering plants and animals and develops

through increasing complexity until it becomes stable or self-perpetuating as a climax community.

EXAMPLE OF ECOLOGICAL SUCCESSION