2.5 Ecosystem Functions

Major Functions of An Ecosystem Producers-Convert sunlight energy into organic matter Consumers- Use living organic matter as energy to grow and develop Decomposers- Break down the dead organic matter / return nutrients to the soil

ENERGY ENTERS THE ECOSYSTEM AS SUNLIGHT Only 2% of the light energy falling on plant is used to create energy The rest is reflected, or just warms up the plant as it is absorbed

Photosynthesis Process where plants use sun light energy to create chemical energy Photosynthesis: equation 6CO2 + 6H2O --> C6H12O6 + 6O2 Inputs: light energy, water, carbon dioxide Outputs: oxygen gas, sugar Energy transformations: Light to Chemical respiration backwards!

Respiration Process by which animals create energy through consumption of organic molecules (sugars) Respiration: C6H12O6 + 6O2 --> 6CO2 + 6H2O Inputs: oxygen gas, organic molecules (sugars) Outputs: carbon dioxide, energy in ATP, waste heat Energy transformations: chemical to heat Photosynthesis backwards!

Photosynthesis and Respiration Glucose / Oxygen CO2/ Water

Energy Transfers in Ecosystem ESSENTIAL QUESTIONS How can a species occupy two different trophic levels simultaneously in the same food web? Decomposers and consumers seem to be doing essentially the same thing. Why do environmental scientists bother to make a distinction between them? Energy transfers are always inefficient. In food chains roughly 90% of energy is lost as heat. Where does this heat go? Is this consistent with viewing the biosphere as a closed system? FLIPCAST— Food chains and the carbon cycle ESSENTIAL QUESTIONS What does the unit J.m-2.y-1 measure? Show that you understand the unit by breaking it down and explaining the significance of each component. Explain why the pyramid of biomass in aquatic ecosystems is often inverted? Why are harmful, non-biodegradable chemicals often found in higher concentrations in the bodies of creatures at the very top of food chains? 2.1.6 Define the terms species, population, habitat, niche, community and ecosystem with reference to local examples. FLIPCAST— Species concept CASE STUDY— California salamanders 2.1.7 Describe and explain population interactions using examples of named species. Include competition, parasitism, mutualism, predation and herbivory. Mutualism is an interaction in which both species derive benefit. Interactions should be understood in terms of the influences each species has on the population dynamics of others, and upon the carrying capacity of the others’ environment. Graphical representations of these influences should be interpreted. ESSENTIAL QUESTIONS Why do biologists say that no two species may occupy the same niche? What is the difference between interspecific and intraspecific competition? Parasites are harmful; but not too harmful. Why do most parasites not kill their hosts?   ENDGAME QUESTIONS: 1. WHAT BIG PICTURE IDEAS DO YOU NEED TO UNDERSTAND? 2. WHAT MUST YOU BE ABLE TO DO? 3. WHAT FACTS DO YOU NEED TO LEARN? ENDGAME—IB EXAMINATION REVIEW There is a menu containing the entire collection of “Essential Questions” from the various syllabus sections. Understanding these big picture ideas and being able to apply them in novel situations is the key to examination success in Environmental Sysytems and Societies. The is also a menu of “Facts and Skills” and a convenient review strategy called “Differentiations of Mastery.”  

Energy Flow Diagram

Water Cycle

Nitrogen Cycle

Carbon Cycle

Gross productivity Total energy captured or “assimilated” by an organism. Measured in joules (J) Plant (Gross Primary Productivity) GPP = sunlight energy used during photosynthesis Animals (Gross Secondary Productivity) GSP = food eaten - energy in faeces Energy is stored in leaf as sugars and starches, which later are used to form flowers, fruits, seeds,

Net productivity The energy left over after organisms have used what they need to survive. All organisms have waste energy and respiratory loss given off as heat, metabolism (R) Plants and animals have to use some of the energy they capture to keep themselves growing: They both move water and stored chemicals around Plants make flowers, fruits, new leaves, cells and stems Animals create cells and need to move muscles. Net productivity = Gross productivity - Respiration Energy or using symbols: NP = GP - R

Net Primary vs. Net Secondary Productivity (NPP) vs. (NSP) Calculate Net productivity for plants and animals NPP = GPP – R PLANTS NSP = GSP – R ANIMALS NSP GSP

Productivity in Food Web In a food web diagram, you can assume that: Energy input into an organism represents the GP Energy output from that organism to the next trophic level represents the NP GP-NP = R (respiration energy ) and/or loss to decomposers ?

Therefore… The least productive ecosystems are those with limited heat and light energy, limited water and limited nutrients. Example biome:_______________ The most productive ecosystems are those with high temperature, lots of water light and nutrients. Example biome:__________________

Now check you have understood! Draw a complete food web for an ecosystem of your choice, which should include: the sun and its energy named primary producers (at least 2) named primary consumers (at least 3) named secondary consumers (at least 2) named decomposers (at least 2) respiration energy loss (use red marker for this arrow) On your diagram use arrows to show direction of energy flow

Complete this energy flow diagram: Label GPP, NPP and R for the primary producer Add arrows to show missing energy pathways (5 in total) Fill in the blank box to explain why some sunlight is not fixed by plant SUN PLANT DECOMPOSERS RESPIRATION ……………………………. (~98% of energy is here) HERBIVORES

Draw your own energy flow diagram, rather like the one on the previous slide to show energy flows through the trophic levels in your food web. Include the following labels: Start with sunlight energy Include all trophic levels from your food web Include arrows showing energy moving from each trophic level to another and to decomposers Show energy lost in faeces Show Respiration loss (heat energy) USE RED MARKER! Label each individual arrow with a letter (A,B,C,D,E…) Use the lettered arrows to write an equation for GPP, NPP Write an equation for GSP, NSP for primary consumers

Respiratory loss by decomposers The data in the table below relate to the transfer of energy in a small clearly defined habitat. The units in each case are in kJ m-2 yr-1 Trophic Level Gross Production Respiratory Loss Loss to decomposers Producers 60724 36120 477 1° Consumer 21762 14700 3072 2° Consumer 714 576 42 3° Consumer 7 4 1 Respiratory loss by decomposers --- 3120 Construct an energy flow model to represent all these data – Label each arrow with the appropriate amount from the data table above. Use boxes to represent each trophic level and arrows to show the flow of energy Calculate the Net Productivity for NPP for Producers NSP for 1°Consumers, 2°Consumers, 3°Consumers NSP for Decomposers

ENERGY FLOW MODEL 1st. Carnivores Top Carnivores Producers Herbivores 60724 21762 1st. Carnivores Top Carnivores 714 7 Producers Herbivores 3072 42 477 1 Decomposers R=3120

Productivity Calculations NPP of Producers: 60724 - (36120+477) =24127 kJ.m-2.yr-1 NSP of 1 Consumer 21762 -(14700+3072) =3990 kJ.m-2.yr-1 NSP of 2 Consumer 714 -(576+42) =96 kJ.m-2.yr-1 NSP of 3 Consumer 7 -(4+1) =2 kJ.m-2.yr-1 NSP of Consumers: 22483 -(15280+3115) =4088 kJ.m-2.yr-1 NSP of Decomposers: (477+3072+42+1) -3120 =472 kJ.m-2.yr-1

How to measure primary productivity Harvest method – measure biomass and express as biomass per unit area per unit time. CO2 assimilation- measure CO2 uptake in photosynthesis and releases by respiration 02 production-Measure O2 production and consumption

Measuring productivity continued 4.Radiosotope method-use c14 tracer in photosynthesis. 5.Chlorophyl measurement- assumes a correlation between the amount of chlorophyll and rate of photosynthesis.