Ecosystems & Communities: Organisms and their Environments

1. Ecosystems & Communities:Organisms and their Environments Chapter 15

2. Energy and chemicals flow within ecosystems 15.6 Energy flows from producers to consumers.

5. First Stop: Primary Producers

6. First Stop: Primary Producers • ecosystem: producers or consumers • primary producers: plants, algae (some), bacteria • convert light energy from sun into chemical energy through photosynthesis • chemical energy = food • consumers eat or absorb their food • energy stored in chemical bonds of carbohydrate, protein, and lipid molecules is captured and harnessed for consumers’ own movement, reproduction, and growth

7. Second Stop: Primary Consumers – the Herbivores

8. Third Stop: Secondary Consumers – the Carnivores

9. Fourth Stop: Tertiary Consumers – the “Top” Carnivores

10. Food Chain

11. Food Web

12. Food Web

13. Food Chains & Food Webs • A change in one link in a food chain will affect the other links. • The table on the next slide gives one example of a food chain and the trophic levels represented in it:

14. Food Chains & Food Webs

15. Chain Reaction Game

17. Energy Flows through a Food Web Losses at every “step” in a food chain Inefficiency of energy transfers

18. A grasshopper eats a plant. A mouse eats the grasshopper. A snake eats the mouse. A hawk could eat the snake or the mouse. In this food web, how would we categorize the hawk? • Producer • Primary consumer • Secondary consumer • Tertiary consumer • Quaternary consumer • 4 and 5

19. Summary 15.6 Energy from the sun passes through an ecosystem in several steps. First, it is converted to chemical energy in photosynthesis. Herbivores then consume the primary producers, the herbivores are consumed by carnivores, and the carnivores, in turn, may be consumed by top carnivores.

20. Summary 2, 15.6 Detritivores and decomposers extract energy from organic waste and the remains of organisms that have died. At each step in a food chain, some usable energy is lost as heat.

21. Energy and chemicals flow within ecosystems 15.7 Energy pyramids reveal the inefficiency of food chains.

22. Biomass • biomass: total weight of all living organisms in a given area • only about 10% of the plants in an ecosystem is converted into biomass • Food Energy Pyramid • flow of energy through a food chain • trophic level: position that an organism occupies in a food chain - what it eats, and what eats it • African savannas and grasslands sustain more species of higher-order carnivores than any other terrestrial ecosystem

24. Food Energy Pyramids flow of energy through a food chain trophic level: position that an organism occupies in a food chain - what it eats, and what eats it

27. You go out to eat at a fancy restaurant. You have a salad, salmon, and for dessert ice cream! Which part of the meal was the most energy efficient food for you to eat? • Salad* • Salmon • Ice cream • 2 and 3

28. Summary 15.7 Energy from the sun passes through an ecosystem in several steps known as trophic levels. Energy pyramids reveal that the biomass of primary producers in an ecosystem tends to be far greater than the biomass of herbivores. The biomass transferred at each step along the food chain tends to be only about 10% of the biomass of the organisms being consumed, due to energy lost in cellular respiration. As a consequence of this inefficiency, food chains rarely exceed four levels.

29. Energy and chemicals flow within ecosystems 15.8 Essential chemicals cycle through ecosystems.

30. Chemical Reservoirs Each chemical is stored in a non-living part of the environment. Organisms acquire the chemical from the reservoir, a non-living part of the environment. The chemical cycles through the food chain (biogeochemical cycles). Eventually, the chemical is returned to the reservoir.

31. The Most Important Chemical Cycles Carbon Nitrogen Phosphorus Sulfur

33. Carbon Cycle Game

34. Fossil Fuels • created when large numbers of organisms die and are buried in sediment lacking oxygen • In absence of oxygen, at high pressures, and after very long periods of time, organic remains are ultimately transformed into coal, oil, and natural gas • burning coal, oil, and natural gas releases large amounts of carbon dioxide • increases average CO2 concentration in the atmosphere • current level of CO2 in the atmosphere is the highest it has been in almost half a million years

35. Global CO2 levels are rising in general, but they also exhibit a sharp rise and fall within each year – why?

36. Why less CO2 in Summer in the Northern Hemisphere? • The plants consume CO2in photosynthesis. • They photosynthesize more in the summer. • The Northern Hemisphere has more land plants because it has more land.

38. Fertilizers Because it is necessary for the production of every plant protein, and because all nitrogen must first be made usable by bacteria, plant growth is often limited by nitrogen levels in the soil. For this reason, most fertilizers contain nitrogen in a form usable by plants.

41. Algal Blooms or Eutrophication • When too much fertilizer is released into the water in any lake, algae and bacteria will grow unopposed. • These will use up all of the oxygen in the water and kill other species. • Water will be fouled, slimy and unfit for recreation.

43. Sulfur Cycle component of protein  cycles in both a gas and sedimentary cycle source : earth's crust enters the atmosphere as  hydrogen sulfide (H2S) during fossil fuel combustion, volcanic eruptions, gas exchange at ocean surfaces, decomposition

44. Sulfur Cycle H2S is immediately oxidized to sulfur dioxide (SO2)  SO2 + water vapor  H2SO4 (falls to earth in rain) Too much sulfuric acid (H2SO4) in the atmosphere constitutes acid rain   sulfur in soluble form is taken up by plant roots, incorporated into amino acids such as cysteine travels through food chain eventually released through decomposition

45. How is carbon recycled back to the atmosphere in the carbon cycle? It is “fixed” by bacteria. It is a product of cellular respiration. Burning of fossil fuels. 2 and 3. All of the above.

46. Why do commercial fertilizers usually contain usable forms of nitrogen and phosphorous? These chemicals are not efficiently recycled in the soil. Nitrogen and phosphorous need to be “fixed” by bacteria or the plant. Nitrogen and phosphorous are found at high levels in the atmosphere but not in the soil. Nitrogen and phosphorous only enter the soil through erosion.

47. Summary 15.8 Chemicals essential to life—including carbon, nitrogen, and phosphorus—cycle through ecosystems. They are usually captured from the atmosphere, soil, or water by growing organisms; passed from one trophic level to the next as organisms eat other organisms; and returned to the environment through respiration, decomposition, and erosion. These cycles can be disrupted as human activities increase or decrease the amounts of the chemicals used or released to the environment.

48. Species interactions influence the structure of communities. 15.9 Interacting species evolve together.