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                                                                         TOPIC 2.3: FLOWS OF ENERGY AND MATTER


Energy "flows" through the ecosystem in the form of carbon-carbon bonds. When respiration occurs, the carbon-carbon bonds are broken and the carbon is combined with oxygen to form carbon dioxide. This process releases the energy, which is either used by the organism (to move its muscles, digest food, excrete wastes, think, etc.) or the energy may be lost as heat. The dark arrows represent the movement of this energy. Note that all energy comes from the sun, and that the ultimate fate of all energy in ecosystems is to be lost as heat. Energy does not recycle!!

In this unit we will seek to quantify the relative importance of different component species and feeding relationships. This unit is a minimum of 6 hours.


Significant Ideas:

  • Ecosystems are linked together by energy and matter flows.

  • The Sun's energy drives these flows, and humans are impacting the flows of energy and matter both locally and globally.


Big questions:

  • What strengths and weaknesses of the systems approach and the use of models have been revealed through this topic?

  • How are the issues addressed in this topic of relevance to sustainability or sustainable development?

  • Why are maximum sustainable yields equivalent to the net primary or net secondary productivity of a system? Why would harvesting biomass at a rate greater than NPP or GPP be unsustainable?

  • How can systems diagrams of carbon and nitrogen cycles be used to who the effect of human activities on ecosystems? What are the strengths and weaknesses of such diagrams?


2.3.U1 As solar radiation (insolation) enters the Earth's atmosphere, some energy becomes unavailable for ecosystems as this energy is absorbed by inorganic matter or reflected back into the atmosphere

  • Explain the fate of solar radiation as it reaches Earth.

Solar energy is any type of energy generated by the sun.

​About 30% of the solar energy that reaches Earth is reflected back into space. The rest is absorbed into Earth’s atmosphere. Just as the incoming and outgoing energy at the Earth’s surface must balance, the flow of energy into the atmosphere must be balanced by an equal flow of energy out of the atmosphere and back to space.

Clouds, aerosols, water vapor, and ozone directly absorb 23 percent of incoming solar energy. Evaporation and convection transfer 25 and 5 percent of incoming solar energy from the surface to the atmosphere. These three processes transfer the equivalent of 53 percent of the incoming solar energy to the atmosphere. If total inflow of energy must match the outgoing thermal infrared observed at the top of the atmosphere, where does the remaining fraction (about 5-6 percent) come from? The remaining energy comes from the Earth’s surface.

The radiation warms the Earth’s surface, and the surface radiates some of the energy back out in the form of infrared waves. As they rise through the atmosphere, they are intercepted by greenhouse gases, such as water vapor and carbon dioxide. 

Greenhouse gases trap the heat that reflects back up into the atmosphere. In this way, they act like the glass walls of a greenhouse. This greenhouse effect keeps the Earth warm enough to sustain life. 


  • Almost all energy that drives processes on Earth comes from the sun.

  • This is called solar radiation and is made up of visible wavelengths (light) and those wavelengths that humans cannot see (UV and infrared).

  • Some 60% of this is intercepted by atmospheric gases and dust particles. Nearly all UV light is absorbed by ozone.

  • Both ultraviolet and visible light energy (short wave) are converted to heat energy (long wave), following the laws of thermodynamics.

2.3.U2 Pathways of radiation through the atmosphere involve a loss of radiation through reflection and absorption as shown in figure 4 (below)

  • Explain pathways of incoming solar radiation incident on the ecosystem

  • The systems of the biosphere are dependent on the amount of energy reaching the ground, not the amount of energy reaching the outer atmosphere. This amount varies according to the time of day, the season, the amount of cloud cover and other factors.

  • Most of this energy is not used to power living systems, it is reflected from soil, water or vegetation or absorbed and re-radiated as heat.

  • Of the energy reaching the Earth's surface, about 35% is reflected back into space by ice, snow, water and land.

  • Some energy is absorbed and heats up the land and seas.

  • Of ALL the energy coming in, only about 1-4% of it is available to plants on the surface of the Earth.

2.3.U3 Pathways of energy through an ecosystem include: conversion of light energy to chemical energy, transfer of chemical energy from one trophic level to another with varying efficiencies, overall conversion of ultraviolet and visible light to heat energy by an ecosystem, re-radiation of heat energy to the atmosphere.

  • ​Describe and explain the transfer and transformation of energy as it flows through an ecosystem.

Matter also flows through ecosystems linking them together. This flow of matter involves transfers and transformations 

The distinction between storages of energy illustrated by boxes in energy-flow diagrams (representing the various trophic levels), and the flows of energy or productivity often shown as arrows (sometimes of varying widths) needs to be emphasized. The former are measured as the amount of energy or biomass per unit area and the latter are given as rates, for example, J m–2 day–1.

Not all solar radiation ends up being stored as biomass. Losses include:

  • reflection from leaves

  • light not coming in contact chloroplasts

  • light of different wavelengths

  • transmission of light through the leaf

  • inefficiency of photosynthesis


This energy is captured by green plants which convert light to chemical energy (glucose).The chemical energy (glucose) is then transferred from one trophic level to the next.The percentage of energy transferred from one trophic level to the next is called the ecological efficiency(energy used for growth (new biomass)) x 100 energy supplied


2.3.U4 The conversion of energy into biomass for a given period of time is measured as productivity
[You need to be able to measure biomass and productivity experimentally. You could design experiments to compare productivity in different systems]

  • ​Define productivity

Productivity is the conversion of energy into biomass over a given period of time. It is the rate of growth or biomass increase in plants and animals. It is measured per unit are per unit time, for instance grams per square meter per day (g m−2 d−1).

Primary production is highest were conditions for growth are optimal, where there are high levels of insolation, good water supply, warm temperatures and high nutrient levels.

You can then divide primary productivity into gross and net profits.

  • *GROSS is the income

  • *NET is the incomes minus costs

Secondary productivity depends on the amount of food there is and the efficiency of the consumers turning this into new biomass. Unlike the primary productivity net productivity involves feeding or absorption.


2.3.U5 Net primary productivity (NPP) is calculated by subtracting respiratory losses (R) from gross primary productivity (GPP). NPP = GPP - R
[The distinction between storages of energy illustrated by boxes in energy-flow diagrams (representing the various trophic levels), and the flows of energy or productivity often shown as arrows (sometimes of varying widths) needs to be emphasized.


The former are measured as the amount of energy or biomass per unit area and the latter are given as rates, for example, J m-2 yr-1]
​[Values for GPP and NPP should be compared from various biomes]

  • Define the term net primary productivity

  • Define the terms and calculate the values of net primary productivity (NPP) from given data.


The amount of organic matter or biomass produced by an individual organism, population, community or ecosystem during a given period of time is called productivity.

Primary production refers to all or any part of the energy fixed by plants possessing chlorophyll. The total amount of solar energy converted (fixed) into chemical energy by green plants (by the process of photosynthesis) is called 'Gross Primary Production' (GPP).

A certain portion of gross primary production is utilized by plants for maintenance (respiration energy loss) and the remainder is called 'Net Primary Production (NPP)' which appears as new plant biomass. It is more useful to measure Net Primary Production (NPP). The remainder of glucose produced from photosynthesis is deposited in and around cells representing the stored dry mass. The accumulation of dry mass is usually termed biomass. Biomass provides a useful measure of the production and use of resources.

Use the equation NPP = GPP – R; where R = respiratory loss. 

Primary production is the foundation of all metabolic processes in an ecosystem, and the distribution of production has a key part in determining the structure of an ecosystem.

  • Gross primary productivity (GPP): is gained through photosynthesis in primary producers.

  • Net primary productivity (NPP): is the gain by producers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses. (Available for consumers in ecosystem)


2.3.U6 Gross secondary productivity (GSP) is the total energy or biomass assimilated by consumers and is calculated by subtracting the mass of fecal loss from the mass of food consumed. GSP = food eaten - fecal loss
[The distinction between storages of energy illustrated by boxes in energy-flow diagrams (representing the various trophic levels), and the flows of energy or productivity often shown as arrows (sometimes of varying widths) needs to be emphasized. The former are measured as the amount of energy or biomass per unit area dn the latter are given as rates, for example, J m-2 yr-1]
​[The term assimilation is sometimes used instead of secondary productivity]

  • Define the term gross productivity

  • Define the terms and calculate the values of both gross primary productivity (GPP)  from given data.

Production also occurs in animals as Secondary Production. Importantly though animals do not use all the biomass they consume. Unlike the primary productivity net productivity, secondary involved feeding or absorption.

Secondary production is the generation of biomass of the consumer in a system. This is driven by the transfer of organic material between trophic levels, and represents the quantity of new tissue created through the use of assimilated food. Secondary production is sometimes defined to only include consumption of primary producers by herbivorous consumers,but is more commonly defined to include all biomass generation by heterotrophs. This is the reason only.

2.3.U7 Net secondary productivity (NSP) is calculated by subtracting respiratory losses (R) from GSP.

  • Define net secondary productivity

  • Define the terms and calculate the values of net secondary productivity (NSP) from given data.

Secondary production is the generation of biomass of heterotrophic (consumer) organisms in a system. This is driven by the transfer of organic material between trophic levels, and represents the quantity of new tissue created through the use of assimilated food.

Production which occurs in animals is known as secondary production. The net quantity of energy transferred and stored in the somatic and reproductive tissues of heterotrophs over a period of time is called secondary productivity.

Gross secondary production in animals equals the amount of biomass assimilated or biomass eaten less feces. As in the case of plants herbivores and carnivores ingest the food material out of which a part gets assimilated and a part is egested. A large part of the assimilated energy is consumed during metabolic process like respiration, growth, reproduction etc and the rest is available to be laid down as new biomass.

The Net Secondary Production (NSP) = Energy assimilated from the food eaten - faeces – energy consumed for respiration. Secondary productivity indicates about food resources available to the heterotrophic populations, including man, in the food chain.

​Use the equation NSP = GSP – R; where GSP = food eaten – faecal loss and R = respiratory loss

  • Gross secondary productivity(GSP): is gained through absorption in consumers.

  • Net secondary productivity(NSP): The gain by consumers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses.

2.3.U8 Maximum sustainable yields are equivalent to the net primary or net secondary productivity of a system.

  • Define maximum sustainable yield

Maximum sustainable yield is e—Equivalent to the NSP or NPP of system.  This information can be and important number for farmers who are trying to predict how much money they will get for their product. Farmers are often paid by how much biomass (often measured by weight/acre) that their crop yields. Modern agricultural economists spend many months predicting yields which drives prices of the food you buy.  


2.3.U9 The carbon and nitrogen cycles are used to illustrate this flow of matter using flow diagrams. These cycles contain storages (sometimes referred to as sinks) and flows, which move matter between storage

  • Describe and explain the transfer and transformation of materials as they cycle within an ecosystem.​


Along with energy, water and several other chemical elements cycle through ecosystems and influence the rates at which organisms grow and reproduce. About 10 major nutrients and six trace nutrients are essential to all animals and plants, while others play important roles for selected species (footnote 3). The most important biogeochemical cycles affecting ecosystem health are the water, carbon, nitrogen, and phosphorus cycles.

The carbon cycle involves the processes of photosynthesis and respiration. Carbon dioxide plays an important role in photosynthesis. Plants use energy from light to split water molecules; they then use carbon dioxide to synthesize carbohydrates. One of the products of this reaction is oxygen. Photosynthesis is the major source of oxygen in Earth’s atmosphere. For some 1.5 billion years before green plants were on Earth, algae and bacteria provided the photosynthesis needed to build Earth’s oxygen levels to the point that respiration of both plants and animals could occur.

Nitrogen is an element that is often a limiting factor for plant growth. Although atmospheric nitrogen is abundant, it is not in a form that plants can readily access. The nitrogen molecule found in the atmosphere must be split and recombined with atoms to form molecules that are soluble in water. This is called nitrogen fixation.


Typically nitrogen is fixed in the form of ammonium or nitrate ions. Some of this fixing occurs in the atmosphere due to lightning. Most nitrogen is fixed by bacteria. When plants and other organisms die, through leaching and the activities of other bacteria the nitrogen is returned to the atmosphere ready to begin the cycle again.

Nitrogen Cycle

2.3.U10 Storages in the carbon cycle include organisms and forests (both organic), or the atmosphere, soil, fossil fuels and oceans (all inorganic)

  • Draw and label the carbon cycle. Label the biotic and abiotic phases

  • ​Identify where carbon is stored

  • Define carbon fixation

  • Define carbon budget

Carbon is stored in organisms and forests, the atmosphere, soil, fossil fuels, and in the oceans. —Places where carbon is stored are called Carbon Sinks —The oceans are the largest carbon sinks, holding many times more carbon than all the forests on earth combined. —Climate change is affecting how much carbon the ocean can hold.

2.3.U11 Flows in the carbon cycle include consumption (feeding), death and decomposition, photosynthesis, respiration, dissolving and fossilization
[The roles of calcification, sedimentation, lithification, weathering and volcanoes in the carbon cycle are not required]​

  • Draw and label the carbon cycle. For each flow, draw storages as boxes, arrows to represent the size of the flow

The carbon cycle is one of the major biogeochemical cycles describing the flow of essential elements from the environment to living organisms and back to the environment again. This process is required for the building of all organic compounds and involves the participation of many of the earth's key forces. The carbon cycle has affected the earth throughout its history; it has contributed to major climatic changes, and it has helped facilitate the evolution of life.

Flows in the carbon cycle are divided into:

  • herbivores feeding on producers

  • carnivores feeding on herbivores

  • decomposes feeding on dead organic matter

  • carbon dioxide from the atmosphere dissolving in rainwater.


  • photosynthesis converts inorganic material into organic matter

  • photosynthesis transforms carbon dioxide and water into glucose

  • respiration converts organic storage into inorganic matter

  • combustion transforms biomass into carbon dioxide nd water

  • fossilization transforms organic matter in dead organisms into fossil fuels

Carbon Cycle Animation

2.3.U12 Storages in the nitrogen cycle include organisms (organic), soil, fossil fuels, atmosphere and water bodies (all inorganic).

  • Draw and label the nitrogen cycle. For each flow, draw storages as boxes, arrows to represent the size of the flow

Nitrogen is stored in organisms, soil, fossil fuels, atmosphere, and bodies of water. Places where nitrogen is stored are called Nitrogen Sinks.

The nitrogen cycle, similarly to the other biochemical cycles, cycles nitrogen from storage pools into directly usable forms and back again. The atmosphere acts as vast storage reservoir for nitrogen because it is 78 percent nitrogen. Because of this, the atmosphere is the largest storage reservoir of nitrogen.


Nitrogen is also stored in: watershed in soil, groundwater, ocean water, sediment and plant matter (dead and living). Human activities are increasing nitrogen's storage in groundwater. It has been seen that groundwater in developed countries stores significantly more carbon than that of developing countries. In nature groundwater is a fairly small and insignificant storage reservoir. 

Nitrogen is contained in both inorganic and organic molecules/reservoirs. Organic reservoirs that contain nitrogen include: amino acids, peptides, nucleic acids and proteins. Each of these molecules is vital to an organisms survival which emphasizes the importance of the nitrogen cycle. Examples of inorganic molecules that contain nitrogen include man-made fertilizers and ammonia. These molecules are less important to both the survival of organisms and the nitrogen cycle itself.

2.3.U13 Flows in the nitrogen cycle include nitrogen fixation by bacteria and lightning, absorption, assimilation, consumption (feeding), excretion, death and decomposition, and denitrification by bacteria in water-logged soils.
​[Detailed knowledge of the role of bacteria in nitrogen fixation, nitrification and ammonification is not required]

  • Draw and label the nitrogen cycle. Label the biotic and abiotic phases

  • Draw and label the nitrogen cycle. For each flow, draw storages as boxes, arrows to represent the size of the flow​Identify where nitrogen is stored

  • Define nitrogen fixation, nitrification, denitrification, decomposition and assimilation

  • Describe the Haber process

  • Define carbon budget

The nitrogen cycle represents one of the most important nutrient cycles found in terrestrial ecosystems. Nitrogen is used by living organisms to produce a number of complex organic molecules like amino acids, proteins, and nucleic acids. 

Flows in nitrogen cycle are

  • herbivores feeding on producers

  • carnivores feeding on herbivores

  • decomposers feeding on dead organic matter

  • plants absorbing nitrates through their roots

  • removal of metabolic waste 


  • lightening transforms nitrogen in the atmosphere into NO3

  • nitrogen-fixing bacteria transform nitrogen gas in the atmosphere into ammonium

  • nitrifying bacteria transform ammonium into nitrite and nitrate

  • denitrifying bacteria transform nitrates into nitrogen

  • decomposers break down organic nitrogen into ammonia

  • nitrogen from nitrates is use by plants to make proteins


2.3.U14 Human activities such as burning fossil fuels, deforestation, urbanization and agriculture impact energy flows as well as the carbon and nitrogen cycles

  • Discuss the human impact on the carbon and nitrogen cycle

Human activities have greatly increased carbon dioxide levels in the atmosphere and nitrogen levels in the biosphere. Altered biogeochemical cycles combined with climate change increase the vulnerability of biodiversity, food security, human health, and water quality to a changing climate.

Human activities have increased atmospheric carbon dioxide by about 40% over pre-industrial levels and more than doubled the amount of nitrogen available to ecosystems. Similar trends have been observed for phosphorus and other elements, and these changes have major consequences for biogeochemical cycles and climate change.

Altered biogeochemical cycles together with climate change increase the vulnerability of biodiversity, food security, human health, and water quality to changing climate. However, natural and managed shifts in major biogeochemical cycles can help limit rates of climate change.​


Applications and Skills

2.3.A1 Analyse quantitative models of flows of energy and matter

Storages, yields and outputs should be included in the form of clearly constructed diagrammatic and graphical models.


2.3.A2 Analyse the efficiency of energy transfers through a system.

Large amounts of energy are lost from the ecosystem between one trophic level and the next level as energy flows from the primary producers through the various trophic levels of consumers and decomposers. The main reason for this loss is the second law of thermodynamics, which states that whenever energy is converted from one form to another, there is a tendency toward disorder (entropy) in the system.

​​2.3.A3 Discuss human impacts on energy flows, and on the carbon and nitrogen cycles.

​Humans clearly disrupt many, if not all biogeochemical cycles and in the process threaten many ecosystems. In resent years human activities have directly or indirectly affected the biogeochemical cycles that determine climatic conditions of earth. It is imperative to mention that, managing and understanding environmental problems caused by climate change would require an understanding of the biogeochemical cycles.


Biogeochemical cycles always involve equilibrium states: a balance in the cycling of the element between spheres. However, overall balance may involve elements distributed on a global scale and that is why a disruption in one cycle causes a disruption in all other cycles. Below is a summary of how human activities have contributed to disruption of biogeochemical cycles. For impacts on specific cycles, the reader should refer to the sites where these cycles are presented.

Phosphorus fertilizers: Human influences on the phosphorus cycle come mainly from the introduction and use of commercial synthetic fertilizers. Use of fertilizers mainly has affected the phosphorus and nitrogen cycles. Plants may not be able to utilize all of the phosphate fertilizer applied; as a consequence, much of it is lost from the land through the water run-off. The phosphate in the water is eventually precipitated as sediments at the bottom of the water body. In certain lakes and ponds this may be redissolved and recycled as a problem nutrient.


Animal wastes or manure may also be applied to land as fertilizer. If misapplied on frozen ground during the winter, much of the fertilizer may be lost when ice melts and forms runoff. In certain areas very large feed lots of animals, may result in excessive run-off of phosphate and nitrate into streams. Other human sources of phosphate are in the out flows from municipal sewage treatment plants. Without an expensive tertiary treatment, the phosphate in sewage is not removed during various treatment operations. Again an extra amount of phosphate enters the water.

Mining of Fossil fuels: Humans have interfered with the carbon cycle where fossil fuels have been mined from the earth crust. Had fossils not been discovered prior to industrial revolution, they could have remained there until now. Carbon dioxide is number one green house gas contributing to global warming and climate change. Additionally, clearing of vegetation that serve as carbon sinks has increased the concentration of carbon dioxide in the atmosphere.

Production of Sulphur dioxide: Human impact on the sulfur cycle is primarily in the production of sulfur dioxide (SO2) from industry (e.g. burning coal) and the internal combustion engine. Sulfur dioxide can precipitate onto surfaces where it can be oxidized to sulphate in the soil (it is also toxic to some plants), reduced to sulphide in the atmosphere, or oxidized to sulphate in the atmosphere as sulphuric acid (a principal component of acid rain). Sulphur compounds play a big role in the climate system because they are important for the formation of clouds.

Additionally, a lot of sulphur is brought into the air by volcanic eruptions. A strong eruption can emit particles up to the stratosphere hence leading to cooling down of the planet.

Cultivation of legumes and use of nitrogen fertilizers: As a result of extensive cultivation of legumes, creation of chemical fertilizers, and pollution emitted by vehicles and industrial plants, human beings have more than doubled the annual transfer of nitrogen into biologically available forms. Humans have significantly contributed to the transfer of nitrogen gases from Earth to the atmosphere, and from the land to aquatic systems through four main processes:

The application of nitrogen fertilizers to crops has caused increased rates of denitrification and leaching of nitrate into groundwater. The additional nitrogen entering the groundwater system eventually flows into streams, rivers, lakes, and estuaries. In these systems, the added nitrogen can lead to eutrophication.

Increased deposition of nitrogen from atmospheric sources because of fossil fuel combustion and forest burning. Both of these processes release a variety of solid forms of nitrogen through combustion.

Livestock ranching. Livestock release a large amounts of ammonia into the environment from their wastes. This nitrogen enters the soil system and then the hydrologic system through leaching, groundwater flow, and runoff.

Sewage waste and septic tank leaching.

2.3.S1 Construct a quantitative model of the flows of energy or matter for given data.

2.3.S2 Calculate the values of both GPP and NPP from given data.

Gross primary productivity (GPP): is gained through photosynthesis in primary producers.
Net primary productivity (NPP): is the gain by producers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses. (Available for consumers in ecosystem)

Primary productivity:

  • where R = energy used in respiration

  • NPP = GPP – R

​2.3.S3 Calculate the values of both GSP and NSP from given data.

​Gross secondary productivity(GSP): is gained through absorption in consumers.
Net secondary productivity(NSP): The gain by consumers in energy or biomass per unit area per unit time remaining after allowing for respiratory losses.

Secondary productivity:

  • NSP = GSP – R

  • GSP = food eaten – faecal loss

  • where R = respiratory loss

Classroom Material
Energy Flow Diagrams worksheet
Eating at a Lower Trophic Level worksheet
Ecological Cycle Diagram Project 
Energy Flow Through an Ecosystem reading = Annenberg Learner
Transfer and Transformation of Energy Through an Ecosystem poster
Calculating Gross and Net Productivity worksheet
NPP Internet activity
Primary Productivity Internal Assessment - in class
Human Impact of Biogeochemcial Cycles - Global Change article


Useful Links
2.3 Energy Flows by NicheScience 
2.3 Materials Cycle by NicheScience
Calculating Productivity


This activity, prepared by Newport High School, will help you improve your ability to calculate productivity from data.
Energy Flow - Mrs. Kings Bioweb
Howard Odum and his work - Learn more about Howard Odum and his work at Wikipedia
Carbon Cycle Game - Windows 2 Universe
Carbon Cycle - BBC Bitesize
Carbon Cycle Online Modeling - Annenberg Learner
Water Cycle Interactive - EPA
Water Cycle Game - Southeast Water
Nitrogen Cycle Interactive - Classzone
Nitrogen Cycle Animation - Vermont County Extension Service
The Nitrogen Cycle - Nature
Primary Productivity - eHow
Primary & Secondary Productivity - Sciencebitz
Ecological Productivity, Ecological Integrity And Its Efficiency Factors - Environmental About
Primary Productivity - LabBench
Net Primary Productivity NASA Map - NASA
Insulation & NPP - NASA
Measuring Primary Productivity - LabBench
Terrestrial Primary Productivity - Nature
Primary Productivity in Plants - Physical Geography
NPP Images - NASA Earth Observatory
Measuring Secondary Productivity
NPP By Biome - NASA
Quizlet Transfer and Transformation

In The News
Why Restoring Nature Could Be the Key to Fighting Climate Change - Time,  15 Oct 2015
As large animals disappear, the loss of their poop hurts the planet - Washington Post - 25 Oct 2015


  • ​The Sun’s energy drives energy flows, and throughout history there have been “myths” about the importance of the Sun—what role can mythology and anecdotes play in the passing on of scientific knowledge?



  • Human impacts on the flows of energy and matter occur on a glbal scale


​Video Clips

In this NASA eClips video segment learn how NASA uses CERES, a satellite in our Earth observing system, to make accurate measurements of energy leaving the Earth. Discover how NASA studies the interactions of clouds with sunlight and heat to determine how much heat is emitted back into space. Demonstrations are used to help support the segment.




















Looks at the processes that are fundamental to all ecosystems. First the concepts of primary productivity, trophic levels, food chains, energy pyramids and the flow of energy through ecosystems are introduced. The program then explains how carbon, nitrogen, phosphorous and water cycle through ecosystems and how human activities can disrupt these cycles and throw them out of balance leading to accelerated eutrophication in lakes in the case of phosphorous imbalances and global warming in the case of carbon imbalances.




















In this video Paul Andersen explains how energy flows in ecosystems. Energy enters via producers through photosynthesis or chemosynthesis. Producers and consumers release the energy from food through cellular respiration. An explanation of gross primary productivity and net primary productivity are included. Energy and biomass in ecological pyramids show energy efficiency.






















Hank introduces us to biogeochemical cycles by describing his two favorites: carbon and water. The hydrologic cycle describes how water moves on, above, and below the surface of the Earth, driven by energy supplied by the sun and wind. The carbon cycle does the same... for carbon!





















What exactly is the carbon cycle? Nathaniel Manning provides a basic look into the cyclical relationship of carbon, humans and the environment.






















Hank describes the desperate need many organisms have for nutrients (specifically nitrogen and phosphorus) and how they go about getting them via the nitrogen and phosphorus cycles.



















This video shows the gross primary productivity of the world's land areas for the period 2000-2009 as calculated from Terra's MODIS instrument. The original 8-day average GPP data has been smoothed to a 24-day average to make the animation less noisy. This version adds a date and colorbar to the animation




















NPP is basically how much carbon is stored in the biosphere. It has been found that not all carbon from burning fossil fuel carbon goes into the air, and that the ocean can only take half of the remainder.






















Flows of Energy and Matter (2.3)

Nutrient Cycles

Water Cycle Website---- Video
Carbon Cycle Website ----Video--- Animation
Nitrogen Cycle Website ---- Animation
Phosphorous Cycle Website--- Animation


Equilibrium and Resilence

How Wolves change Rivers

Photosynthesis and Respiration

Photosynthesis vs Respiration
Technical differences
Connecting Photosynthesis and Cellular Respiration
Photosynthesis vs Resipiration Game


Productivity and Biomass

The Energy Flow: Primary productivity at high trophic levels
Gross vs Net Productivity summary
Environmental Factors affecting Plant Productivity 
Biomass and Productivity
​Biomass and production
​Experiment - NPP and GPP light experiment using DO

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