ECOSYSTEM ECOLOGY

Ecosystem: The organisms in a particular area and the physical environment with which they interact. (Abiotic factors: energy, water, carbon, nitrogen, phosphorous) All the biotic and abiotic factors in a community.

Fig Microorganisms and other detritivores Tertiary consumers Secondary consumers Primary consumers Primary producers Detritus Heat Sun Chemical cycling Key Energy flow

Energy Flow through Ecosystems Energy flows through ecosystems as organisms capture and store energy, then transfer it to organisms that eat them. These organisms are grouped into trophic levels...

Trophic Levels: Route of energy flow - food chain - food web - pyramid of numbers

Pyramid of Numbers

Question: “Why are big fierce animals rare?” Charles Elton, 1927

Answer: Because of the way energy flows through communities...

Ecosystem Energy Budgets: Primary Productivity (PP) Secondary Productivity (SP1, SP2…)

Photosynthesis powers primary productivity. Primary Productivity (PP) The annual productivity of an area is determined primarily by sunlight, temperature, and moisture. Rate at which energy or biomass is produced per unit area by plants (primary producers)

Which of these ecosystems accounts for the largest amount of Earth’s primary productivity? A)Tundra B)Savannah C)Salt marsh D)Open ocean E)Tropical rainforest

Figure 56.5 Distribution of Primary Terrestrial Production Worldwide

Positive Correlation Between Productivity and Sunlight

Positive Correlation Between Productivity and... Precipitation Temperature

Net primary production (g/m 2 ·yr) Fig Tropical forest Actual evapotranspiration (mm H 2 O/yr) Temperate forest Mountain coniferous forest Temperate grassland Arctic tundra Desert shrubland 1,500 1, ,000 2,000 3,000 ·

Secondary Productivity (SP1, SP2…) rate of production of new biomass from PP by heterotrophic organisms (primary and secondary consumers) positively correlated with rainfall...

Fig Primary producers 100 J 1,000,000 J of sunlight 10 J 1,000 J 10,000 J Primary consumers Secondary consumers Tertiary consumers

Where does all the energy go???

Fig Cellular respiration 100 J Growth (new biomass) Feces 200 J 33 J 67 J Plant material eaten by caterpillar

Ecological Efficiency: Percent of energy transferred from one trophic level to the next.

Three categories of transfer efficiency are required to predict energy flow from PP to SP1 to SP2... 1)consumption efficiency 2)assimilation efficiency 3)production efficiency

1) consumption efficiency (CE) % of total productivity at one trophic level that is consumed by the next highest level (remainder not eaten)

Green World Hypothesis Plants have many defenses against herbivores

2) assimilation efficiency (AE) % of ingested food energy that is assimilated (i.e. digested), and thus potentially available for growth, reproduction (remainder lost as feces)

AE is higher in carnivores (~80%) than in herbivores (20-50%). WHY? A)Carnivores chew their food more. B)Herbivores chew their food more. C)Plant tissues are not as easy to digest as meat. D)Meat is not as easy to digest as plant tissues.

Elephant dung

3) production efficiency (PE) % of assimilated energy that is incorporated into new biomass (growth, reproduction) (remainder lost as respiratory heat)

PE of endotherms (<10%) is lower than PE of ectotherms (30-40%). WHY? A)Because endotherms have feathers and fur. B)Because endotherms move more quickly than ectotherms. C)Because ectotherms move more quickly than endotherms. D)Because ectotherms get energy from the sun.

SP1 is the % of PP that is incorporated at the next highest trophic level… SP2 is the % of SP1 that is incorporated at the next highest trophic level… This is NEVER 100%.

And that is why big fierce animals are rare! Energy loss at each trophic level limits the length of a food chain...

Atmosphere LithosphereHydrosphere Living Organisms + Detritus Biogeochemical Cycles

In studying cycling of water, carbon, nitrogen, and other chemicals, ecologists focus on four factors: –Biological importance of each chemical –Major reservoirs for each chemical –Forms in which each chemical is available or used by organisms –Key processes driving movement of each chemical through its cycle

Water is essential to all organisms 97% in the oceans 2% in glaciers and polar ice caps 1% in lakes, rivers, and groundwater The Water Cycle Evaporation, transpiration, condensation, precipitation, and movement through surface and groundwater

Carbon-based organic molecules are essential to all organisms Carbon reservoirs include fossil fuels, soils, solutes in oceans, plant and animal biomass, and the atmosphere The Carbon Cycle CO 2 taken up via photosynthesis and released via respiration Volcanoes and burning of fossil fuels contribute CO 2 to atmosphere (2.9 B metric tons/yr)

CO 2 CO 2 concentration (ppm) Temperature Average global temperature (ºC) Year Greenhouse Gases and Global Warming

Global Temperature Changes

Nitrogen is a component of amino acids, proteins, and nucleic acids Main reservoir of nitrogen is in atmosphere (N 2 ) N 2 converted to NH 3 via nitrogen-fixing bacteria The Nitrogen Cycle NH 3 decomposed to NH 4 +, which can be decomposed to NO 3 – by nitrifying bacteria; both assimilated by plants Denitrifying bacteria convert NO 3 – back to N 2

How Bears Feed Salmon to the Forest The run of salmon leads to a major flow of nutrients into estuaries and coastal watersheds

Bears catch salmon in river and consume them in forest; on average, half the carcass is not eaten. Bears’ fat tissue is virtually nitrogen-free, so most of nitrogen in salmon protein is excreted as urine and feces.

Measurements of nitrogen isotope ratios in tree rings shows that nitrogen from salmon is incorporated into trees and enhances their growth Nitrogen 14 from atmosphere Nitrogen 15 from salmon