1. 3.3 Energy Flow in Ecosystems

2. Food Chains and Food Webs
Food Chain- series of steps in which organisms transfer energy by eating or being eaten.
Energy flows in a one way stream
From primary producer to various consumers

3. Food Chains and Food Webs
Phytoplankton- mixtures of floating algae. (primary producer of the ocean)
Zooplankton: small, swimming animals that feed on marine algae (primary consumer of the ocean)

4. Food Chains and Food Webs

5. Food Webs
Food Web- a network of feeding interactions in an ecosystem .
Food webs contain numerous food chains within them.
Many organisms die without being eaten so decomposers and detritivores play a big role.

6. Food Webs and Disturbance
It is difficult to determine how food webs will react to changes in the environment.
Natural disasters also play a huge role in food web disturbances.

7. Trophic levels and Ecological Pyramids
Trophic level- each step in a food chain or food web.
Ecological Pyramids- show the relative amount of matter or energy contained within each trophic level in a food chain or food web.
RULE of TEN- only 10% of the total energy available in a trophic level makes it to the next level above it.

8. Ecological Pyramids
There are three different types of ecological pyramids: pyramids of energy, pyramids of biomass, and pyramids of numbers.
Ecological pyramid (pyramid of energy): show the relative amount of energy available at each trophic level

9. Biomass (Pyramids of Biomass): show the total amount of living matter at each trophic level
The amount of biomass a given trophic level can support is determined, in part, by the amount of energy available at that particular level.
A pyramid of numbers shows the relative number of individual organisms at each trophic level in an ecosystem.

10. Primary producers have the most energy, followed by the primary consumers. After several trophic levels, the amount of available energy is too low to support a population, which is why the number of trophic levels is limited.

11. Example:

12. A team of ecologists observed feeding patterns of several populations in the desert. The energy pyramid shown below depicts the feeding patterns the ecologist observed. 

13. Which of the following best explains the difference in the amount of available energy in the trophic levels of the desert ecosystem?
A. There is less energy available in the producers because their tissues are less dense than those at higher trophic levels.
B. There is more energy available in the second trophic level because less energy is needed for hunting compared to the higher trophic levels. 
C. There is more available energy in the birds of prey because they have greater muscle mass for storing energy than organisms in lower trophic levels have. 
D. There is less available energy in the fourth trophic level because of the loss of energy through metabolism in each of the lower trophic levels.

14. Answer:
D. There is less available energy in the fourth trophic level because of the loss of energy through metabolism in each of the lower trophic levels.
Each successive trophic level contains about 10% of the available energy from the previous trophic level. The other 90% is lost as heat to the atmosphere through metabolism by the organisms in that level.

15. If several species of carnivores are removed from an ecosystem, the most likely effect on the ecosystem will be:
A. An increase in the kinds of autotrophs
B. A decrease in the number of abiotic factors
C. A decrease in stability among populations
D. An increase in the rate of succession

16. Answer: C

17. Which of these organisms would most likely be found at the top of an energy pyramid? 
A. clams - a primary consumer
B. sardines - a primary consumer
C. sharks - a secondary consumer
D. kelp - a primary producer

18. Answer: C.
sharks - a secondary consumer Energy pyramids show the amount of available energy with the lowest levels having the most energy. Producers are found at the bottom of the pyramid, while secondary consumers would be found at the top.

19. Which of the following statements is true about natural systems? 
A. Consumers form the bottom levels of both the energy pyramid and the biomass pyramid.
B. Producers are at the bottom level of both the energy pyramid and the biomass pyramid.
C. Producers are at the bottom of the energy pyramid, but at the top of the biomass pyramid.
D. Consumers are at the bottom of the energy pyramid, but at the top of the biomass pyramid.

20. Answer: B.
Producers are at the bottom level of both the energy pyramid and the biomass pyramid. Both the biomass pyramid and the energy pyramid have producers at the bottom. Producers account for most of the biomass and most of the available energy in any given ecosystem.

21. 3.4 Cycles of Matter

22. Recycling in the Biosphere
Unlike the one-way flow of energy which gets used or released as heat, matter is recycled within and between ecosystems. Constantly getting reused.

23. Biogeochemical Cycles
Biogeochemical Cycles- elements pass from one organism to another and among parts of the biosphere through closed loops powered by the flow of energy.
Photosynthesis
Cellular respiration
Water cycle
Carbon cycle
Nitrogen cycle
Phosphorus cycle
Processes involved in the biogeochemical cycle are biological processes, geological processes , and chemical processes.

24. Biological Processes- consist of any and all activities performed by living organisms such as eating, breathing, “burning” food, and eliminating waste.
Geological Processes- include volcanic eruptions, the formation and breakdown of rock, and major movement of matter within and below the earth’s surface.
Chemical and Physical Processes- include the formation of clouds and precipitation, the flow of running water, and the action of lightning.
Human Activity- mining and burning of fossil fuels, clearing of land for building and farming, and the use of fertilizers.

25. The Water Cycle (Hydrologic)
Water continuously moves between the oceans, atmosphere, and land.
Water is evaporated,condensed, precipitated, and then goes through the cycle again and again.
Water evaporates when it changes from a liquid to water vapor, which is the gas state of water.
Evaporation occurs on the surface of the ocean and other bodies of water.
Transpiration is the evaporation of water through plant leaves.

27. Nutrient Cycles
Nutrients- chemical substances that organisms need to sustain life.
Every organism needs nutrients to survive.

28. The Carbon Cycle Carbon is a major component of all organic compounds.
In the atmosphere, carbon exists as Carbon Dioxide (CO2)
Oceans store carbon
Photosynthesis is one of the few processes that remove carbon dioxide from the atmosphere.
Most processes of the carbon cycle involve energy changes.
CO2 added to the atmosphere by….
Volcanoes and fires
Animal Respiration
Humans (burning fossil fuels -- factories, cars, etc.)
Geologic forces can turn accumulated carbon into carbon-containing rocks or fossil fuels.

29. Carbon cycle
Carbon Dioxide  Plants (photosynthesis)  Carbohydrates in plants  animals eat the plants  use the carbohydrates for energy release carbon as CO2 through cellular respiration When organisms die, carbon from their body is decomposed/geologic process stored in the earth as fossil fuels released into the atmosphere are carbon dioxide

31. The Nitrogen Cycle Nitrogen gas (N2) – 78 % of earth’s atmosphere.
Nitrogen fixers (special bacteria): convert nitrogen (N2) gas into ammonia.
Decomposers: break down dead matter and release nitrogen containing compounds into the soil (or water).
Denitrification: bacteria convert nitrates back to nitrogen (N2) gas.

32. Phosphorus cycle Phosphorus is found in rocks and ocean sediments.
Forms a part of vital molecules such as DNA and RNA.
As rocks gradually wear down, phosphorus is released.

33. Difference of Phosphorus Cycle
Carbon, oxygen, and nitrogen all form gases in the atmosphere, but phosphorus does not form a common gas.
Unlike the other biogeochemical cycles, the phosphorus cycle is confined to the biosphere, hydrosphere, and geosphere.

34. Nutrient Limitation
Limiting nutrient - A nutrient that is in short supply and limits the growth of primary producers is called a limiting nutrient (scarce or cycles slowly in ecosystem).
Even if ample sunlight and water are available the primary productivity of an ecosystem may be limited by the availability of nutrients.

35. Nutrient Limitation in Soil
The growth of crop plants is typically limited by one or more of the nutrients that must be taken up by plants through their roots.
Most fertilizers contain large amounts of nitrogen, phosphorus, and potassium.
All nutrient cycles work together like gears.

36. Nutrient Limitations in Aquatic Ecosystems
The open oceans of the world are nutrient-poor compared to many land areas. Nitrogen is often the limiting nutrient in marine environments and phosphorus is normally the limiting nutrient in aquatic environments(lakes)
After heavy rains aquatic systems can receive large levels of nutrients.
Algae blooms are when algae covers the water’s surface and disrupt the functioning of an ecosystem due to increase in nutrients.

37. Examples:

38. The diagram below shows the cycling of nutrients in an ecosystem.
The removal of which of the following groups would cause an immediate decrease in the amount of energy flowing through the system? 
A. Producers
B. Consumers
C. Decomposers
D. Inorganic nutrients

39. Answer:  A
Producers Producers gather energy from the sun and convert it to useable molecules for consumers. Removing producers from any food chain or web will cause an immediate decrease in available energy.

40. In a process called transpiration, plants get rid of excess water through pores in the leaves called stomata. This excess water is then released into the atmosphere as part of the water cycle. Which of the following terms best describes how the released water enters the atmosphere?
A. condensation
B. precipitation
C. evaporation
D. capillary action 

41. Answer:
C. Evaporation
Water that is released by plants through transpiration evaporates into the atmosphere to rejoin the water cycle.

42. The water cycle would not occur if which of the following were missing?
A. bacteria B. autotrophs C. carbon dioxide
D. solar energy

43. Answer: D

44. Leaves fall from deciduous trees in autumn
Leaves fall from deciduous trees in autumn. The carbon in these leaves is returned to the atmosphere through which of the following processes? A. Condensation B. decomposition C. photosynthesis D. transpiration

45. ANSWER: B