I can explain how energy flows through food chains, food webs, and food pyramids.

food chains: models that show the flow of energy from plant to animal, and animal to animal

trophic level: each step in a food chain

food chain 1

*Plants receive energy from sunlight and produce food in the form of carbs during photosynthesis.

food webs: models of the feeding relationships within an ecosystem

food pyramids: models that show the loss of energy from one trophic level to another


Every element of an ecosystem is dependent on each other and altering or adding just one thing can upset the balance of nature and cause a negative chain reaction.


I can describe how nutrients are cycled in an ecosystem.

Nutrients support growth and other life processes, and are produced and constantly recycled in the biosphere. They are accumulated for short or long periods of time in the atmosphere, oceans, and land masses (stores).

The Carbon Cycle

Carbon is an essential part of chemical processes that sustain life.


long-term stores: middle and lower ocean layers; coal, oil, and gas deposits, carbonate rocks from seashells

short-term stores: aquatic and terrestrial organisms, the atmosphere, top layers of the ocean

How Carbon Cycles

carbon 2

Forest fires, volcanic eruptions, factories and burning fossil fuels, and mining emit CO2 into the atmosphere.

carbon 3

Through photosynthesis, plants convert energy from the sun to produce glucose and oxygen (as a by-product). The oxygen is inhaled by an animal (or plant) and CO2 is exhaled back into the atmosphere through cellular respiration. The same process can be applied to aquatic ecosystems with cyanobacteria and algae.

carbon 4

Through predation, carbon from the prey is transferred to the predator.

Human Impact on the Carbon Cycle

Burning fossil fuels and mining has increased CO2 levels by 30% and is depleting long-term carbon stores. Agriculture and urban expansion reduces plants that absorb and clean CO2. Since CO2 is a greenhouse gas, the high levels of CO2 in our biosphere is trapped, creating global warming and climate change.

The Nitrogen Cycle

Nitrogen is important for the construction of DNA and proteins.


Nitrogen is mainly stored in the atmosphere (78%) as N2, in oceans, organic matter in soil, and terrestrial ecosystems and waterways.

How Nitrogen Cycles

Nitrogen is cycled through processes involving plants.

(the diagram below does not include human activities)

nitrogen 1

The are four steps in the nitrogen cycle – nitrogen fixation, nitrification, uptake, and denitrification. Above is a basic diagram explaining the steps, excluding in-depth processes, algae, and human interference.

Human Impact on the Nitrogen Cycle

Nitrogen has doubled in the last 50 years because of human activities like burning fossil fuels and treating sewage. Excess nitrogen-containing fertilizer from crops leaches into the waterways and enables algae to thrive (eutrophication) while the other organisms suffer.

The Phosphorus Cycle

Phosphorus is essential for life processes in plants and animals, such as phosphorus being a part of the molecule ATP and promoting root growth in plants and strong bones.


Phosphorus is trapped in phosphates found in rocks and in the sediments on the ocean floor and released through geologic uplift and weathering.

How Phosphorus Cycles

phosphor 2

Human Impact on the Phosphorus Cycle

Humans add excess phosphorus through mining for fertilizer and reduce phosphorus supplies by the slash-and-burning of forests.


Significant changes to the cycling of these three ( plus hydrogen and oxygen) impacts biodiversity and the harmony of nature. Carbon cycle changes increases global warming and climate change therefore influencing the food web; excess nitrogen creates competition amongst certain plant species impacting the food web as well; low phosphorous levels decrease the growth of algal species that are critical to many food chains. Humans cause the most harm to these cycles so it is imperative that we start caring for and preserving the environment before it reaches point where Earth is lifeless.


I can explain how chemicals can accumulate and cause harm to organisms in ecosystems.

Synthetic chemicals such as PCBs and POPs enter the environment in air, water, and soil. Plants take up these chemicals and through predation it builds and travels up the food chain (bioaccumulation), increasing in concentration with each trophic level (biomagnification). Heavy metals (such as lead, cadmium, and mercury) are lethal at low amounts  and also bioaccumulates and biomagnfies.

bioacc 1

Synthetic chemicals and heavy metals at high levels negatively effect an organism’s nervous, immune, and reproductive system, and cause birth defects in offspring and cancer. It also causes death.

When synthetic chemicals such as PCBs and POPs enter the food web they cause so many problems, especially when keystone species are affected. PCBs and POPs not only harm organisms, but it has a long half-life so they persist and wreak havoc in the environment for a long time. Heavy metals don’t degrade and can’t be destroyed.

bioacc 2

Numbers are not accurate, just used for example.
*Correction: Orcas (1000ppm)

bioacc 3

bioremediation: is the use of living organisms (plants and micro-organisms) to clean-up naturally, only faster through biodegradation

Micro-organisms naturally feed on chemicals to reduce them and plants (i.e. fescue, alfalfa, poplar trees) traps hazardous wastes in soil and reduces the spread of contaminants.


When chemicals and metals enter the food web, they not only devastate the system but they persist for many years. With understanding of how synthetic and organic chemicals, and heavy metals work we can learn from our mistakes and advance to new technologies and prevention methods to protect biodiversity and conserve the ecosystem.