4.2

• Essential idea: Ecosystems require a continuous supply of energy to fuel life processes and to replace energy lost as heat.

Ecosystem

A community and its abiotic environment

• The sun is the main source of energy for most ecosystems

• All life that you see on Earth’s surface relies either directly or indirectly on sunlight

https://www.youtube.com/watch?v=GSVv40M2aks

4.2.U1 Most ecosystems rely on a supply of energy from sunlight.

• During photosynthesis, producers use sunlight as an energy source to make chemical energy

• Light dependent reactions use sunlight to produce ATP and NADPH (energy carrying molecules)

• ATP and NADPH go on to provide the energy needed in the Calvin Cycle to convert CO2 (inorganic carbon compound) to high energy carbohydrates (organic carbon compound)

4.2.U2 Light energy is converted to chemical energy in carbon compounds by photosynthesis

• The organic molecules (carbs, lipids, protein) found in the producers are referred to as chemical energy because of the energy stored in their bonds

• Producers can release this energy when they do cellular respiration

• This chemical energy can also be passed on to heterotrophs through feeding

4.2.U2 Light energy is converted to chemical energy in carbon compounds by photosynthesis

4.2.U3 Chemical energy in carbon compounds flows through food chains by means of feeding.

• Food chain:

– The arrow is pointing at the organism doing the consuming because that is where the energy will flow to

Helioconius butterfly

http://4.bp.blogspot.com/_XlUWKcZV7wg/TGK9bg09fAI/AAAAAAAAAXs/EpokiiPbkQA/

s1600/Heliconius_erato_001.JPG

Passionflowerhttp://en.wikipedia.org/wiki/File:Violet_Passion_Flower.jpg#filelinks

JaguarTegu lizard

http://en.wikipedia.org/wiki/Tupinambis

4.2.U3 Chemical energy in carbon compounds flows through food chains by means of feeding.

Food webs show all of the feeding relationships within a habitat. Read this research article and generate a food web.

The state of the oceans, part 2: Delving deeper into the sea's bounty. John Tibbetts

4.2.U3 Chemical energy in carbon compounds flows through food chains by means of feeding.

Food webs show all of the feeding relationships within a habitat.

4.2.U3 Chemical energy in carbon compounds flows through food chains by means of feeding.

Energy Losses in Ecosystems• Respiration releases energy which is used by organisms and

converted to heat

o The energy released is needed for cell activities such as:o Synthesizing DNA, RNA, and proteino Active transport (pumping molecules or ions across

membranes AGAINST concentration gradients)o Moving things around in the cell (ex: chromosomes,

vesicles or protein fibers in muscle cells)

4.2.U4 Energy released from carbon compounds by respiration is used in living organisms and converted to heat.

• Heat energy is unusable to organisms and is lost to the environment and in turn lost from ecosystemso It is lost from the ecosystem because once heat has radiated it cannot be

taken back for use

• Reasons for energy loss between trophic levels:• Heat energy lost from respiration• Organic material not consumed• Not all parts of consumed matter digested or absorbed by consumer• Energy lost in feces and passes to decomposers instead

• As a result, food chains are limited in length

Energy Losses in Ecosystems

4.2.U5 Living organisms cannot convert heat to other forms of energy. AND 4.2.U6 Heat is lost from ecosystems.

• Energy flows from one trophic level to the next– Producers get their energy from the sun through

photosynthesis.– Energy then flows from the plant to the primary

consumer that eats it– The energy transfer continues from one level to

the next• Transfer of energy through trophic levels is

inefficient

4.2.U7 Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.

• Each level only passes approximately 10% of the energy on to the next level (10% Law) – Why?– Some of the energy is used for growth and

maintenance of the organisms itself– Some of the energy is lost as heat during metabolic

processes – Some of the energy is locked in chemical bonds that

consumers cannot break (ex. Cellulose, hair, bones, etc.)

• Less and less energy is available to subsequent levels

4.2.U7 Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.

• Energy is continually supplied by sun but is lost at each trophic level

• As a result, each level is always smaller than the one before

• Unlike energy, there is a finite and limited supply of nutrients. Therefore, nutrients must be recycled

4.2.U7 Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.

4.2.S1 Quantitative representations of energy flow using pyramids of energy.

4.2.U7 Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels.

• Biomass is an estimate of the mass of all the organisms within a trophic level

• It is expressed in units of mass per unit area per unit time• Just as not all energy is passed from one trophic level to the next,

not all biomass gets passed on eithero Carbon dioxide is lost during cellular respirationo Water is lost during transpiration & evaporation from skino Waste products including urea are excreted

Summary: