2. Ecosystems Trophic LevelsTrophic Levels –Food Chains & Webs Energy FlowEnergy Flow Ecological PyramidsEcological Pyramids –Number pyramids –Biomass pyramids –Energy pyramids Biological MagnificationBiological Magnification

3. Food chains are usually made up of four to five trophic levels. All food chains begin with Producers (autotrophs), organisms which have the ability to make their own “food” or organic compounds. –Photo-autotrophs use ________ to make their own organic compounds. Ex) –Chemo-autotrophs use ____________________ to make their own food or organic compounds. Ex) Energy Flow in Ecosystems Occurs in Food Chains sunlight inorganic compounds Plants, photosynthetic algae, etc Sulfur bacteria in deep sea vents

4. Consumers lack the ability to make their own organic compounds Consumers (heterotrophs) must obtain all their nutrients by eating or consuming other organisms. –Primary consumers eat producers. These organisms can also be described as ____________, or plant-eaters. –Secondary consumers eat primary consumers (and sometimes producers as well). Thus they can also be described as ____________ or ___________, accordingly. herbivores carnivores omnivores

5. So what happens to all the dead producers and consumers? _____________ obtain their energy by breaking down (dead) organic matter into inorganic substances & compounds._____________ obtain their energy by breaking down (dead) organic matter into inorganic substances & compounds.Ex) The actions of decomposers allow the return of these more basic inorganic compounds to the soil or water. What happens to these compounds in the soil next? (Think about this.)The actions of decomposers allow the return of these more basic inorganic compounds to the soil or water. What happens to these compounds in the soil next? (Think about this.) Decomposers fungi, bacteria, some insects / animals

7. A food web is made up of a number of interconnected food chains. At what trophic level is the cricket which eats the plants? At what level is the mouse which eats the plants and the cricket?

8. Interactions Among Trophic Levels in a Food Web Both negative & positive interactions occur in a food web:Both negative & positive interactions occur in a food web: –Predators have a __________________ on their prey –Upper-level carnivores can have an ________ positive effect on producers and vice versa (how?) Food web dynamics are extremely complex due to these direct & indirect interactions!Food web dynamics are extremely complex due to these direct & indirect interactions!

9. Energy Flow Through Ecosystems is One-Way Energy enters most ecosystems as _______.Energy enters most ecosystems as _______. A tiny percent of this light energy is captured for use by producers during photosynthesisA tiny percent of this light energy is captured for use by producers during photosynthesis –During photosynthesis, light energy is converted to chemical energy (in the form of glucose sugar and other chemical compounds). Light + H 2 O + CO 2  C 6 H 12 O 6 + O 2 sunlight

10. Energy Flow Through Ecosystems is One-Way When these organic compounds are broken apart during cellular respiration, energy is made available (in the form of ______) to do cellular work: muscle contraction, repair of tissues, reproducing, etc.When these organic compounds are broken apart during cellular respiration, energy is made available (in the form of ______) to do cellular work: muscle contraction, repair of tissues, reproducing, etc. C 6 H 12 O 6 + O 2  ATP + H 2 O + CO 2 As work is accomplished, energy escapes the body in the form of HEAT, which is released into the environment and dissipates into spaceAs work is accomplished, energy escapes the body in the form of HEAT, which is released into the environment and dissipates into space Once energy has been used by an organism and lost as HEAT, it is no longer available for re-useOnce energy has been used by an organism and lost as HEAT, it is no longer available for re-use Ecosystems rely on a continuous input of energy from the _____, or some other source (chemical).Ecosystems rely on a continuous input of energy from the _____, or some other source (chemical). ATP SUN

11. Ecological Pyramids

12. 37 g/m 2 minnow 11 g/m 2 snapper Ecological Pyramids are a way to display different characteristics of a food chain of a given ecosystem Pyramids of numbers show the relative number of organisms in each trophic levelPyramids of numbers show the relative number of organisms in each trophic level Pyramids of biomass show the relative amount of living organic material in each trophic level (dry weight)Pyramids of biomass show the relative amount of living organic material in each trophic level (dry weight) 1 tuna 74 seaweed 12 minnow 5 snapper 1.5 g/m 2 tuna 809 g/m 2 seaweed

13. Pyramids of Numbers and Biomass Pyramids of numbers or biomass are often widest at the base and get smaller as you go up the food chain…Pyramids of numbers or biomass are often widest at the base and get smaller as you go up the food chain… BUT, this is not always the case… (Why?)BUT, this is not always the case… (Why?)

14. Pyramids of Numbers 1 hawk Grassland Temperate Forest 3 small birds 15 crickets 50 producers2 producers How can a pyramid of numbers have a smaller number of producers than it does primary consumers? ________________

15. Pyramids of Biomass Here is the base of a biomass pyramid that is smaller than the level above it… How is this possible? In this case, the smaller mass of phytoplankton (algae, etc.) ________________________________ –This allows a small amount of producers to sustain a larger mass of primary consumers. reproduces as quickly as it is eaten

16. 10% “Rule”: On average, only 10% of the energy is conserved as biomass in the transfer from one level to another.10% “Rule”: On average, only 10% of the energy is conserved as biomass in the transfer from one level to another. The remaining 90% is used during metabolism and is “lost” in the form of ______, __________, _____________, etc.The remaining 90% is used during metabolism and is “lost” in the form of ______, __________, _____________, etc. Pyramids of Energy Pyramids of energy show the relative amount of energy stored in the tissues (biomass) of all the organisms in each trophic level.Pyramids of energy show the relative amount of energy stored in the tissues (biomass) of all the organisms in each trophic level. Pyramids of energy always are widest at the base and get narrower toward the top. WHY?Pyramids of energy always are widest at the base and get narrower toward the top. WHY? HEATmovement waste material

17. Energy Pyramids show us how to minimize our impact on the Earth Food energy available to the human population at different trophic levels: 730,000 Cal/yr (2,000 Cal/day) x (365 days/yr) = 730,000 Cal/yr to support one person What is the difference in getting those calories from corn directly v. beef? (7,300,000 Cal of corn to feed cows) - (730,000 Cal to feed people) = 6,570,000 extra Calories of corn 730,000 Cal/yr 7,300,000 Cal/yr

18. Pollution & Food Chains

19. Early days of the DDT era. 1945, New York, Jones Beach State Park: DDT spraying for mosquito control. Pollution and Food Chains Chemical pesticides (like DDT) have helped us fight disease and increase agricultural productivity, but not without an ecological cost.

20. Rachel Carson: environmentalist American marine biologist & nature writer worked for US Bureau of Fisheries 1950’s interested in environmental problems caused by pesticides 1962 authored Silent Spring, documenting impact of pesticides like DDT on environment http://en.wikipedia.org/wiki/Rachel_Carson http://www.johnehrenfeld.com/2010/01/rachel-carson-and-green-chemis.html Silent Spring brought these concerns to the general public and is credited with helping launch modern environmental movement

21. Biological Magnification of Non-biodegradable Toxins DDT is ______________________DDT is ______________________ –Once eaten by living things it cannot be broken down for removal from the body –Instead, it is stored in the body -- mostly in fat tissue DDT ______________ as you proceed up the food chainDDT ______________ as you proceed up the food chain –Although producers may only have small concentrations in their cells, much higher concentrations are found in top consumers due to magnifying effects of food chain. (Can you explain how this happens?) –This can occur with non- biodegradable toxins such as mercury & other heavy metals non-biodegradable accumulates The concentration of DDT found in the lower levels of the food chain may not be significantly harmful…but the higher concentrations found at the top of the chain can be very dangerous

22. Effects of DDT Dead peregrine falcon embryo (development almost completed) found in a nest in SW Scotland, May 1971. Further analysis revealed this egg contained one of the highest concentrations of DDT ever recorded in a bird in Great Britain. DDT causes a bird’s liver to break down the hormones that make calcium available during egg production in females. The result is thin-shelled, fragile eggs. Birds at the top of food chains, such as the peregrine falcon, the osprey, and the bald eagle were/are the principal victims. With the banning of DDT in many countries (in 1972 in the US), dramatic recoveries have been observed in populations of all three species. With the banning of DDT in many countries (in 1972 in the US), dramatic recoveries have been observed in populations of all three species. Fact: The time for 95 % breakdown for DDT in the environment is 10 years.