AP Environmental Chapter 9
Unit 2

Energy Flow
 Movement of energy through an ecosystem from the environment, through organisms, and then back to the environment
 Inputs:
 Energy fixed by organisms
 Energy transferred as heat through the air, water or land currents

Energy Flow
 Kinetic energy in the environment can be visible as heat in living organisms
 The infrared picture on the right shows clover leaves with and without ozone exposure

1 st Law of Thermodynamics
 “ Conservation of Energy”
 States that in any change energy is neither created or destroyed

2 nd Law of Thermodynamics
 Whenever work is done some energy is always lost to heat and cannot be efficiently recovered
 This decrease in order (disorganization of energy) is called entropy

2 nd Law of Thermodynamics
 For an ecosystem to function energy must continuously be added to replace energy lost by metabolic processes

Energy Efficiency
 As energy flows through a food web, it is degraded, and less and less is useable.
 Energy efficiency- the ratio of output to input
 The amount of useful work obtained from some amount of available energy

Energy Efficiency
 Trophic-level efficiency- the ratio of production of one trophic level to the production of the next trophic level.
 Never very high
 1-3% in natural ecosystems
 10% may be maximum
 90% of all energy lost as heat

Biological Productivity
 The goal of ecological communities is to efficiently use energy for the production of biomass
(biological material)
 Energy is the ultimate limiting factor for the growth of a species or population

Biological Productivity
 Biomass- the total amount of organic matter on
Earth or in any ecosystem or area.
 Usually measured as the amount per unit surface area
 Biological production- the capture of usable energy from the environment to produce organic compounds in which that energy is stored.

Biological Productivity
 Change in biomass over a given time is called net production.
 Three measures used for biological production
 Biomass
 Energy stored
 Carbon stored

Types of Production
 Autotrophs
 Make their own organic matter from energy source and inorganic compounds
 Primary production
 Most photosynthesize, some chemoautotrophs
 Heterotrophs
 Cannot make their own organic compounds and must feed on other living things
 Secondary production

Biological Productivity
• Primary production generates the most biomass
• Secondary production stores or uses biological energy through processes like tissue growth or respiration to create smaller amounts of biomass
• In a food chain decomposers carry out decomposition of biomass into abiotic nutrients

Biological Productivity
 Use of energy from organic matter by both heterotrophic and autotrophic organisms is done by respiration.
 Organic matter (glucose) combines with oxygen
 Releases energy stored in chemical bonds along with carbon dioxide and water
 Respiration- the use of biomass to release energy that can be used to do work.

Gross and Net Production
 Production of biomass for use as energy
 1. An organism produces organic matter in its body.
(gross production)
 2. It uses some of this new organic matter as a fuel for respiration.
 3. It stores some of the newly produced organic matter for future use. (net production)

Gross and Net Production
 Gross Primary Production(GPP) is the total amount of CO
2 that is fixed by the plant in photosynthesis.
 Net Primary Production (NPP) = GPP – Respiration
 Net Ecosystem Production (NEP) =
GPP – Respiration from all sources in the ecosystem

Primary Production
 There are 2 ways to measure the primary production of a biological community
 Rate of photosynthesis (measurement of CO2 depletion or O2 production)
 Rate of increase in plant biomass (weight of organic tissue)
What are the sources of errors in both methods for a natural environment?

Biological Productivity
 Depending on the situation involved there are different ways to measure productivity of a system
 Standing crop: measure of the biomass of a system at a single point in time (Ex: the amount of corn growing in a corn field)
 Energy output (Ex: machinery)

Biological Productivity
 Biomass can be gained through ingestion of chemical energy created by primary production
 Biomass is lost through excretion
(decomposition or respiration)
 Assimilation is the amount of biomass created overall
 Assimilation = ingestion-excretion

Biological Productivity
 Different ecosystems reach different levels of productivity based on environmental factors

Biological Productivity
 Worldwide production based on the area covered by the ecosystem globally

Ecological Succession
 Ecosystems are dynamic systems that are constantly changing and requiring change
 If systems are disturbed then the recovery process is called ecological succession

Ecological Succession
 Succession is represented by gradual changes in the species within a community over time
 Two types:
 Primary succession: the establishment of an ecosystem where one did not exist before
 Secondary succession: the re-establishment of an ecosystem after a disturbance where remnants of a biological community have been left behind

Primary Succession
 Begins in a place that has no soil and no living species
 The first species that move into an area are called pioneer species
Lichen is an example of a pioneer species that is able to break solid rock down into soil through chemical weathering processes


Primary Succession
Lichens: a symbiotic relationship between algal or cyanobacterial cells that are photosynthetic and a fungus.
 The fungi provides support, water and minerals and are able to decompose organic material.
 The algae or bacteria provide sugars through photosynthesis.

Primary Succession
 As lichens die they break down into organic material that enters the newly made soil
 Once nutrient rich soil has been created other small plant species are able to enter the ecosystem and find the nutrients necessary to survive

Primary Succession
 As small plants continue to add organic matter to the soil larger organisms are then able to be supported by the ecosystem

Secondary Succession
 With soil and some biologic activity in the environment secondary succession takes less time to develop nutrients to support larger organisms

Climax community
 A climax community is the goal of succession in an environment because it marks a period of stability after a disturbance and is characterized by mature organisms that are able to reach sustainability in the ecosystem

Succession patterns in NC
 The types of intermediate and climax plants that arise during succession depend on the surrounding environment
 Succession in most North
Carolina environments result in pine species during the intermediate phases that then give way to hardwood species like oak and hickory trees

Succession patterns in NC
 During the intermediate stages pine tree development occurs relatively quickly and creates a forest canopy that blocks sunlight from reaching shrubs and underbrush
 Without sunlight, the forest floor clears and creates a bed of leaf litter that chokes out new pine seedlings leaving room for the hardwood saplings to take root and thrive
 As hardwoods flourish they choke out the pine trees to reduce competition for nutrients

Succession Patterns in NC