Ecosystems

What is an Ecosystem? All the organisms living in a community (biotic) and all the abiotic factors that they interact with. Ecosystems receive energy from sunlight, Turned into chemical energy by autotrophic organisms consumed by heterotrophs Energy flows through ecosystems Matter is recycled throughout them.

Ecosystems in relation to Thermodynamics Energy cannot be destroyed only transformed = energy in an ecosystem brought in by the sun and released as heat. The total amount of energy stays the same. Chemical elements in ecosystems travel from trophic level to trophic level in an endless cycle unlike energy that needs the sun’s constant supply of energy.

Trophic Relationships in an Ecosystem Autotrophs/primary producers: support all other levels Heterotrophs/Primary Consumers/Herbivores: eat primary producers. Heterotrophs/Secondary Consumers: eat primary consumers Tertiary Consumers: eat Secondary Consumers Detritivores/Decomposers: consumers that get energy from organic material called detritus (dead things, feces).

Decomposers/Detritivores They make chemical energy available for producers in an ecosystem They decompose organic materials and transport chemical materials into soil, water and air. Main decomposers = fungi and prokaryotes

Factors Limiting Production in Ecosystems Primary Production= amount of light energy turned into chemical energy by autotrophs Solar Radiation: 1% of this is converted to chemical energy by primary producers, this is still enough for primary producers to produce 170 billion tons of organic material/year. Gross Primary Production (GPP): all primary production in ecosystem/ amount of light E turned into chemical E. Net Primary Production (NPP): GPP – E used by primary producers and consumers to live: Shows the storage of chemical energy that is available for consumers to use.

Production Forest has large biomass but primary production is lower than grasslands because grasslands do not accumulate plants (organisms eat them). Ecosystems have large ranges of production they create. Terrestrial Ecosystems make 2/3 of the worlds net primary production, marine ecosystems make 1/3.

Factors Inhibiting Primary Production in Marine Ecosystems Light: only penetrates to a certain depth in the water. Limiting Nutrient: something that needs to be added so that the production can increase in an area. (Nitrogen, Phosphorus) Nitrogen limits phytoplankton growth in ocean. Iron concentrations are low in oceans because dust from land gives iron to oceans so central Pacific/Atlantic don’t have a lot of iron. If there is not a lot of iron and iron is added then cyanobacteria grows and fixes nitrogen, then phytoplankton population increases. Nutrients available determine marine ecosystem primary production

Temperature and Moisture: Limit Terrestrial Production Warm, wet conditions = high production Dry, cold conditions = low productions Moderate Conditions = moderate production Evapo-transpiration : amount of water transpired by different plants and then evaporated by the land. (Increases when precipitation increases and light E available) Nitrogen + Phosphorus also limit terrestrial production.

Energy Transfer Trophic Efficiency is the percentage of production that is transported from one trophic level to the next one Most energy available at one level is not transported to the next level (only 5-20%) Ecosystems cannot have many top-trophic level carnivores because so much energy is lost up the trophic levels

Movement of Nutrients through Ecosystem Limited amounts of chemical elements are available to ecosystems. They are recycled throughout the ecosystem through biotic and abiotic factors. Carbon, Nitrogen, Sulfur, and Oxygen are recycled globally. Phosphorus, Potassium, Calcium, trace elements are recycled locally (Soil). Ecologists study chemical cycling in an ecosystem by adding radioactive isotopes to different elements they are tracing.

Biogeochemical Cycles (Water Cycle) Water Cycle: all organisms need it and it’s availability in an ecosystem affects processes. Processes in the Water Cycle – Evaporation, Condensation, Precipitation Transpiration by plants and groundwater flow that brings water to oceans

Biogeochemical Cycle (Carbon Cycle) The framework of organic molecules is carbon. Autotrophs take CO 2 and make organic molecules that autotrophs and heterotrophs can then use. Carbon comes from fossil fuels, soil, aquatic soil, oceans, plant + animal biomass, and the atmosphere Photosynthesis fixes CO 2 in the atmosphere CO 2 is also added into the atmosphere by cellular respiration (producers, consumers). Fossil Fuels and volcanoes also add CO 2 into atmosphere

Biogeochemical Cycle (Nitrogen Cycle) Limiting Plant Nutrient Mostly found in the atmosphere as nitrogen gas, but also found in soil, and aquatic sediment Enters ecosystem through bacterial nitrogen fixation in roots of plants

Biogeochemical Cycle (Phosphorus Cycle) Plants synthesize phosphate and plants absorb it to synthesize organic molecules Mostly comes from marine rocks When rocks disintegrate soil receives more phosphate

How Decomposition and Vegetation effect Nutrient Cycling Rate of nutrient cycling in different ecosystems are extremely different because of the rate of decomposition. Warm temperatures and moisture increase the rate of decomposition.

Human Impact Interrupts nutrient cycling. Farming depletes nutrients in some areas and creates too many in another. Humans add toxic materials to ecosystems. Acid Rain Ozone depletion Climate change

Toxins Humans bring toxins into ecosystems. Organisms ingest them and they accumulate in their bodies. Biological Magnification: Toxins becoming more concentrated in successive trophic levels in a food web. Top-Level carnivores most affected by toxins in ecosystem. Many toxins cannot be degraded.

Acid Precipitation Burning of fossil fuels (coal) releases sulfur and nitrogen oxides. The acids return to the earth as acid rain, snow, sleet, or fog. (pH under 5.6) Lowers pH of soil and water Causes problems for plants and animals. Fish populations decline. (Freshwater lakes)

Ozone depletion CFC : fluorocarbons: released into air and deplete ozone: emissions have been reduced due to policies in various countries – Freon, AC units – Burning styrofoam – aerosols

Climate Change Burning fossil fuels increased CO 2 levels in atmosphere. Deforestation: not using the CO2 If the rate of CO 2 levels keep increasing it will be double what it was at the beginning of the Industrial Revolution. CO 2 makes Earth retain more heat. (Greenhouse Effect) Increased temperature = melting polar icecaps = sea levels rising = flooding coastal areas Ozone layer thinning which makes increased UV radiation.