APES Chapter 3

Ecosystem Ecology

Ecosystem boundaries are not always clearly defined. This is because the characteristics of an ecosystem depend on:

• Climate in that location

• Presence of water

• Precipitation

• Ability of soil to retain water

Therefore, the boundaries of an ecosystem are dependent on the biotic and abiotic factors. A well defined ecosystem will have easily identifiable biotic and abiotic components, where as a poorly defined system will not.

A cave is an example of a well defined ecosystem due to:

• Identifiable Biotic Factors

• Identifiable Abiotic Factors

A cave has specific and identifiable animals and microorganisms adapted to live in that environment, as well as a distinct temperature, salinity, and water stream.

Other ecosystems are more difficult to define, mainly terrestrial. This is because the ecosystem boundaries are subjective. Examples of what they may be defined by are:

• range of a specific species

• topographic features

• administrative eg. Yellowstone

The Biosphere is the combination of all the ecosystems on earth.

Movement of Energy throughout an ecosystem begins with the photosynthesis of an autotroph or producer. An autotroph is an organism that uses energy from the sun to produce usable energy. This is done through photosynthesis****.

Chemical & Word Equation for Photosynthesis:

6 H^2O + 6 CO^2 in the presence of sunlight & chlorophyll → C^6H^12O^6 + 6O^2

Water + Carbon Dioxide in the presence of sunlight & chlorophyll → Glucose + Oxygen

Chemical & Word Equation for Aerobic Respiration:

6O^2 + C^6H^12O^6 → 6H^2O + 6CO^2 + ATP

Oxygen + Glucose → Water + Carbon Dioxide + Energy

Cellular respiration is the process by which cells unlock the energy of chemical compounds. Aerobic respiration is the process by which cells convert glucose & oxygen into carbon dioxide, water, and energy. This is different than anaerobic respiration, which is when cells convert glucose into energy without oxygen. This creates lactic acid. This lactic acid buildup is what creates muscle pain while exercising. Photosynthesis, however, is the opposite of respiration. It is when producers convert carbon dioxide and water in the presence of sunlight and chlorophyll into glucose and oxygen.

Energy moves through organisms in trophic levels, or the successive levels of organisms consuming one another. The first tropic level is always the producer, the second is the primary consumer, the third is the tertiary consumer, and so on.

Food Chain: the sequence of consumption from producers through tertiary consumers

Food web: a complex model of how energy and matter move between trophic levels

Scavenger: an organism that consumes dead animals

Detritivore: an organism that specializes in breaking down dead tissues and waste products into smaller particles

Decomposers: Fungi and bacteria that convert organic matter into small elements and molecules that can be recycled back into the ecosystem

The gross primary productivity (GPP) of an ecosystem is a measure of the total amount of solar energy captured by the producers by photosynthesis over a given amount of time. This is different from the net primary productivity, which subtracts the energy respired. This establishes the rate of biomass, or the total amount of mass of all living organisms in a given area. The amount of biomass present at a specific time is the standing crop. A trophic pyramid can be a pyramid of biomass, numbers, or energy.

Biogeochemical Cycles