Teacher Information! Necessary materials: Presentation (ppt.) Teacher Information! Necessary materials: PowerPoint Guide If teacher has internet access, the following YouTube video would be a good tool at Slide 12 “Trophic Level Cascades Complete” at http://www.youtube.com/watch?v=yg5ieYKvYI8 **all relevant terms are bolded. (**Unit 2 does not use Managing Our Natural Resources)

Ecosystem Productivity Intro to Range--OBJ 4: PPT Ecosystem Productivity PowerPoint adapted from: http://www.miracosta.cc.ca.us/home/rmooney/Ecology.pdf http://www.globalchange.umich.edu/globalchange1/current/lectures/kling/energyflow/energyflow.html  very good online resource that further explains primary productivity. Principles of Ecology

Students will be able to… Intro to Range--OBJ 4: PPT Students will be able to… Discuss trophic levels and energy flow in ecosystems

Intro to Range--OBJ 4: PPT Food chains Definitions reviewed: Producers  autotrophs make up the base of an ecosystem Consumers  eat other living organisms Detrivores/decomposers  consume dead organisms and fecal wastes Review terms from “Food Chains & Webs” PowerPoint.

Intro to Range--OBJ 4: PPT Primary productivity The rate at which producers capture & store energy in their tissues Gross = total Net = after respiration The most productive ecosystems in the world  estuaries, swamps, marshes, tropical rain forest Temperate forests are also highly productive.

Net primary production per unit area of the world’s common ecosystems Intro to Range--OBJ 4: PPT Net primary production per unit area of the world’s common ecosystems Figure from: http://www.globalchange.umich.edu/globalchange1/current/lectures/kling/energyflow/energyflow.html

Factors influencing primary productivity Intro to Range--OBJ 4: PPT Factors influencing primary productivity Climate & nutrients Morphology & size of organism Rainfall Temperature Season Soil (mineral & nutrient availability) Numerous factors influence primary productivity, especially climate and nutrient availability.

Pathways of energy flow Intro to Range--OBJ 4: PPT Pathways of energy flow Energy from primary productivity can flow through 2 categories of food webs Grazing food webs Producer  Primary consumer  Secondary consumer  tertiary consumer… Detrital food webs Energy flows from producers to detrivores & decomposers Grazing food webs are what we usually think of when we hear the term food web. The producer (plant) is eaten by the primary consumer (herbivore) which is eaten by the secondary consumer (carnivore) which is eaten by the tertiary consumer (carnivore) and so on. Detrital food webs focus on the energy flow from the producer to detrivores and decomposers—returns nutrients to soil. These two food webs overlap when, i.e., mushrooms (detrivore) are eaten by a consumer. How do people disrupt the flow of food chains and webs?  clearing habitat for urban/industrial/farm development, introducing (accidentally or intentionally) invasive, nonnative organisms, chemicals from industry and agriculture, plastic waste in ocean gets consumed by fish which in turn get consumed by baby seabirds, baby seabirds can’t pass or digest the plastic so they die. There are many examples of human disruption of food webs.

Intro to Range--OBJ 4: PPT Trophic levels Feeding levels with respect to primary source of energy Producers & consumers each occupy a different trophic level Energy is lost at each level See next slide for diagram.

Intro to Range--OBJ 4: PPT Image from: http://www.britannica.com/EBchecked/topic-art/606499/15/Transfer-of-energy-through-an-ecosystem Note that energy is lost as heat at each trophic level. Ask students if they think there can be more than four trophic levels in an ecosystem. There can be, but this doesn’t occur often (more than five trophic levels would be even more uncommon) because of the amount of energy that is lost by the time the tertiary consumer is reached.

Intro to Range--OBJ 4: PPT Biomass The total weight of all living organisms Biomass at each trophic level  biomass pyramid Biomass pyramid (grams/m2) 809 37 11 1.5 Producers Herbivores Primary carnivores Top carnivores Detrivores/ decomposers 5 If you weighed up all the biomass at each trophic level you could plot it as a “biomass pyramid” of the ecosystem. Keep in mind that herbivores = primary consumers, primary carnivores = secondary consumers, etc. Again, note how energy is lost at higher trophic levels. Measuring biomass is a way to measure the productivity of an ecosystem.

Intro to Range--OBJ 4: PPT Energy flow pyramid The amount of energy in each trophic level can also be estimated and plotted in a pyramid Energy flow pyramid (kcal/m2/year) 20,810 3,368 383 21 Producers Herbivores Primary carnivores Top carnivores Detrivores/decomposers 5,060 For most ecosystems, the amount of energy and biomass decreases at higher trophic levels. Based on the energy flow and biomass pyramids, how would you expect the number of higher-level consumers (top predators) to compare to lower trophic-level organisms (producers and primary consumers)?  There are fewer predators than herbivores, and fewer herbivores than producers. People are generally the top predator of all food webs. The world human population is over 6 billion. What implications could this have for food chains? The number and type of primary producers supported by an ecosystem will control the type and number of consumers in the system. Alternately, top consumers in the system can have exceptional control over the structure of their ecosystem  Bottom up vs. top down control. See YouTube video “Trophic Level Cascades Complete” at http://www.youtube.com/watch?v=yg5ieYKvYI8 for discussion on bottom up vs. top down effects (about 5 minutes long).

Why do energy and biomass decrease at higher trophic levels? Intro to Range--OBJ 4: PPT Why do energy and biomass decrease at higher trophic levels? Not all biomass is consumed from one trophic level to next Not all that is consumed is turned into biomass Shorter food chain/web = less loss of energy Supports idea that vegetarianism is the best way to feed a large population… Not all biomass is consumed from one trophic level to the next Not all that is consumed is turned into biomass A. Most energy is used for body activity (energy is released as heat) B. Some biomass is lost as inorganic nutrients (CO2) C. Some that is consumed is not digested and is lost as undigested fecal waste D. Result: The shorter the food chain or web, the less the loss of usable, high quality energy.  this supports the idea that man should be vegetarian in order to feed a large population. But see next slide…

Intro to Range--OBJ 4: PPT Vegetarianism Results in a decrease of human position on food chain This won’t solve world hunger Only 25% of earth’s land can be farmed We need ruminants So if we more efficiently use energy by placing ourselves lower on the food chain (by being vegetarians), couldn’t this increase our food supply (increase energy)? It wouldn’t work. Non-farmable pastures and grasslands are important energy sources to us… Humans can’t eat grass (or corn stalks or cottonseed hulls  byproducts of crop production) but ruminants (eg., cows) can. Ruminants convert grasses and crop residue into an energy source that we can use (meat, milk). Less than half the dry matter produced by crops is edible by humans. The remaining residues (stalks, leaves, husks) can be converted to human food only by animals like cattle.

The “Cellulose Dichotomy” Cellulose  most abundant, naturally-occuring organic molecule on earth Humans can’t digest it Ruminants can digest it Cattle, sheep, goats Deer, bison, antelope, moose, elk “Hind-gut fermentors” can digest cellulose Horses, rabbits, some rodents cellulose

Intro to Range--OBJ 4: PPT Review Discuss trophic levels and energy flow in ecosystems