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 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