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What Is Ecology?

The study of the relationships between living organisms and their physical environment.

Ecology provides information about the benefits of ecosystems, and how we can use Earth’s resources in ways that leave the environment healthy for future generations.

Ecologists study these relationships among organisms and habitats of many different sizes, ranging from the study of microscopic bacteria growing in a fish tank, to the complex interactions between the thousands of plant, animal, and other communities found in a desert.

{ Ecological Society of America. http://www.esa.org/esa/education-and-diversity/what-does-ecology-have-to-do-with-me/ }
The ecosystm of this oasis can be found in the middle of scrub desert { http://www.geography4kids.com/files/land_ecosystem.html }

An ecosystem includes:

all of the living organisms in an area, along with the non-living parts of the environment (weather, ground/rocks, Sunlight, soil, atmosphere, rain).

Ecosystems depend on the energy that moves in and out of that system.
You could have an entire ecosystem underneath a big rock.
On the other hand, you could be talking about the overall ecosystem of the entire planet (biosphere).

An ecosystem can be as small as a puddle or as large as the Pacific Ocean.

Energy flows through ecosystems in one direction

From the Sun, through photosynthetic organisms (including green plants and algae),
to herbivores, to carnivores and then to decomposers.


Energy flow through an ecosystem

{ image from http://karimedalla.wordpress.com/2013/05/01/5-1b-energy-in-ecosystems/ }

Each rectangle in an energy pyramid shows the amount of energy per square meter of area.
Each rectangle is always smaller the level below it.
Why? There is a loss of energy as we move from one “trophic level” to the next.  Where is this energy lost to?
* Some organisms die, and rot, without being eaten
* As the organism, it constantly takes in food & energy every day – and then loses most of this energy as body heat – “waste heat.”
* Even when an organism is eaten, not all parts of it are edible. The inedible parts contain energy that is “lost” to the predator.


The Carbon Cycle

{ http://eschooltoday.com/ecosystems/the-carbon-cycle.html }

The carbon cycle is very important to all ecosystems, and ultimately life on earth. The carbon cycle is critical to the food chain.

Living tissue contain carbon, in proteins, fats and carbohydrates. The carbon in these (living or dead) tissues is recycled in various processes.

Human activities like heating homes and cars burning fuels (combustion) give off carbon into the atmosphere.
During cellular respiration, animals also introduce carbon into the atmosphere in the form of CO2 (carbon dioxide.)

CO2 in the atmosphere is absorbed by green plants (producers) to make food in photosynthesis.

When animals feed on green plants, they pass on carbon compounds to other animals in the upper levels of their food chains.

Animals give off CO2 into the atmosphere during respiration.

CO2 is also given off when plants and animals die: Decomposers (bacteria and fungi) break down dead plants and animals (decomposition) and release the carbon compounds stored in them.

Very often, energy trapped in the dead materials becomes fossil fuels which is used as combustion again at a later time.


Human influences on some ecosystem processes

Some Ways Humans Adversely Influence Ecosystems

The nitrogen cycle

{ http://eschooltoday.com/ecosystems/the-nitrogen-cycle.html }

Nitrogen makes up  78% of our atmosphere. It is in the form of a nitrogen molecule, N2 (two N atoms bonded together.)

Plants can not use N2 directly from the air. N2 is unreactive.

N2 gas therefore needs to be converted into nitrate compound in the soil. This is done by nitrogen-fixing bacteria in soil, or on plant root nodules. N2 can also be fixed in the soil by lightning.

Consider the diagram below:

1. Nitrogen is introduced to the soil by precipitation (rain, lightning).

2. Nitrates don’t only come from Nitrogen in the air. They can also be obtained by the conversion of ammonia, commonly used in fertilizers by nitrifying bacteria in the soil. Some root nodules can also convert nitrogen in the soil into nitrates.

3. Plants build up proteins using nitrates absorbed from the soil.

4. When animals like cows, eat these plants, they in turn use it to build animal protein.

5-6. When these animals (cows) defecate, urinate or die, the urea, excreta or carcass are broken down by decomposers. The nitrogen is re-introduced into the soil in the form of ammonia.

7. Nitrates in the soil can also be broken down by denitrifying bacteria (in specific conditions) and sent into the air as nitrogen. This process can help make the soil infertile, because it will lack the nitrates needed for plant use.

Once nitrogen gets back into the air, the cycle continues.


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