Energy Essential Knowledge Objectives 4.A.6 (a-d, g) 4.B.4 (b) - - PowerPoint PPT Presentation

Ecosystems and Energy

Essential Knowledge Objectives 4.A.6 (a-d, g) 4.B.4 (b)

Matter and Energy

• Energy enters, flows through, and exits an

ecosystem

• Matter cannot be created or destroyed, but it

can change form (recycled) – law of conservation of mass

• Chemical nutrients cycle within ecosystems

through biogeochemical cycles (carbon, nitrogen, phosphorus, water)

Matter and Energy

• Energy enters from the sun as radiation,

moves as chemical energy transfers through food webs, and exits as heat radiated back into space

Matter and Energy

Energy Flow in Ecosystems

• Energy flows through ecosystems from the sun

through producers to consumers

• Organisms within food webs and food chains

interact

• Food webs and food chains are dependent on

primary productivity

Primary Producers (Phototrophs)

• Plants, photosynthetic protists (algae),

chemosynthetic and photosynthetic bacteria (cyanobacteria)

• Convert solar energy into chemical energy

(glucose) through photosynthesis

Primary Producers (Chemotrophs)

• Chemosynthetic bacteria (prokaryotes) are the

primary producers of the deep-sea hydrothermal vent communities

• Convert inorganic chemicals (CO2, H2S, CH4)

into organic molecules (sugars) through chemosynthesis

Primary Productivity

• Primary productivity: The amount of light

energy converted to chemical energy (organic molecules) by autotrophs (photosynthetic and chemosynthetic) during a given time period in an ecosystem

• Influenced by changes in regional and global

climates and in atmospheric composition

Primary Productivity

• Food webs and food chains are dependent on

primary productivity – why?

• Represents the storage of chemical energy

that will be available to consumers in an ecosystem

GPP and NPP

• Gross primary productivity (GPP): total

primary production in an ecosystem (the amount of energy from light, or chemicals, converted to chemical energy of organic molecules per unit time

• Net primary productivity (NPP): equal to the

GPP minus the energy used by the primary producers for autotrophic respiration

Net Primary Productivity (NPP)

(write down the equation below in your notes)

Global Primary Production

Terrestrial Primary Production

Terrestrial Primary Production

• Temperature and moisture are the main

factors controlling primary production in terrestrial ecosystems

Aquatic Primary Production

Aquatic Primary Productivity

• Ocean phytoplankton are responsible for

approximately 50% of the global biosphere net primary production

• Global annual ocean primary production has

decreased due to an increase in global sea surface temperature – why? (thermocline)

• Light and nutrients are limiting factors

Light and Nutrient Limitation

• Solar radiation drives photosynthesis (not the
• nly variable controlling primary production)
• Limiting nutrients are elements that must be

added for production to increase, such as nitrogen and phosphorus

Consumers (Heterotrophs)

• Herbivores, carnivores, omnivores, detritivores,

decomposers

Role of Decomposers

Trophic Levels and Ecological Pyramids

Trophic Levels

• A trophic level is the

position that an

• rganism occupies in a

food chain or food web (what it eats, what eats it)

Ecological Pyramids

• Graphical representations designed to show

the biomass or bioproductivity at each trophic level in a given ecosystem

• Energy pyramid, biomass pyramid, and

pyramid of numbers

Energy Pyramid

• A graphical representation of energy flow in a

community of organisms

Trophic Efficiency

• Trophic efficiencies are generally only about

10% (90% of the energy available at one trophic level not passed on)

Trophic Efficiency

Pyramid of Net Production

Biomass Pyramid and Numbers Pyramid

• Biomass pyramids represent the total dry

mass of all organisms in one trophic level

• Numbers pyramids show the number of

individual organisms in one trophic level