How Ecosystems Work

1. How Ecosystems Work

2. The Sun • Life depends on the sun • The sun is the ultimate source of energy for almost all organisms • Photosynthesis – a series of chemical reactions that use light to convert water and carbon dioxide into sugar and oxygen • 6CO2 + 6H2O → C6H12O6 + 6O2 • Plants, algae and some bacteria do photosynthesis

3. Producers & Consumers • Producers – organisms that make their own food • Autotrophs – self-feeders • Get their energy directly from the sun • Consumers – organisms that get their energy by eating other organisms • Heterotrophs – other-feeders • Get their energy indirectly from the sun by eating producers or other consumers

4. Producers & Consumers

5. The Exception to the Rule • Deep-ocean ecosystems thrive where there is no sunlight • Producers make food from hydrogen sulfide from the hot ocean vents instead of sunlight • Other organisms then eat these producers

6. Types of Consumers • Herbivores – consumers that eat only producers (plant-eaters) • Carnivores – consumers that eat only other consumers (meat-eaters) • Omnivores – consumers that eat both plants and animals (eaters of all) • Decomposers – consumers that break down dead organisms

7. What Eats What

8. Respiration • Cellular respiration - gets the energy out of the food by using oxygen to break it down • All living things use cellular respiration to get energy from food • C6H12O6 + 6O2→ 6CO2 + 6H2O • Essentially the reverse of photosynthesis

9. Food Chains • Each time an organism eats another organism, energy is transferred • Food chain – a sequence in which energy is transferred from one organism to the next as each organism eats another

10. Food Webs • Ecosystems are much more complicated than a simple food chain • Food web – shows many feeding relationships in an ecosystem

11. Trophic Levels • Trophic level – each step in the transfer of energy through an ecosystem • Each time energy is transferred, less of it is available to organisms at the next level • Some energy is lost during the process of respiration; most is used for daily functions • About 90% of the energy is used; only 10% is left for the next trophic level

12. Trophic Levels

13. Water Cycle • Water moves between the Earth’s surface and the atmosphere • The sun provides the energy to drive the cycle • Evaporation – water changes from a liquid to a gas • Precipitation – water vapor cools and falls to Earth as rain, sleet, or snow • Groundwater – layer of water underground

14. Water Cycle • Living organisms move water about… • Carried within bodies (by drinking it or extracting it from food) • During respiration, water is excreted • Water also evaporates from the skin as sweat • Plant roots collect water from the soil • Some is used for photosynthesis • Some is evaporated or transpired from the leaves

15. Water Cycle • What are the 3 phases of water? • Solid • Ex. Glaciers, ice on the surface of a lake or pond • Liquid • Ex. oceans, rivers, streams, lakes • Gas • Ex. Water vapor • Water vapor cannot be seen, but we know that fog and clouds contain it

16. Water Cycle

17. Carbon Cycle • Carbon is an essential part of proteins, fats, and carbohydrates needed for life • Producers take CO2 from the atmosphere • Consumers eat the producers to obtain carbon • CO2 is released back to the atmosphere during cellular respiration • Fossil fuels store carbon that is then released when they are burned

18. Carbon Cycle • Four main reservoirs of carbon: • Atmosphere • Carbon dioxide, carbon monoxide • Terrestrial Biosphere • Includes freshwater, soil • Oceans • Dissolved carbon, living organisms in the ocean • Sediments • Fossil fuels

19. Carbon Cycle • Four processes involved in the carbon cycle: • Biological processes – photosynthesis, respiration & decomposition • Geochemical processes – release of carbon dioxide gas into the atmosphere by volcanoes • Mixed biogeochemical processes – burial of carbon-rich organisms and their conversion to fossil fuels • Human activity – mining, burning of fossil fuels

20. Carbon Cycle

21. Nitrogen Cycle • All organisms need nitrogen to build proteins • Nitrogen gas makes up 78% of the atmosphere • Nitrogen-fixing bacteria – Convert nitrogen from the air into ammonia (nitrogen fixation)

22. Nitrogen Cycle • Ammonia is converted into nitrates and nitrites, which plants and other producers can use (nitrification) • Bacteria convert nitrogen in the soil into atmospheric nitrogen (denitrification) • Decomposers return nitrogen to the soil

23. Nitrogen Cycle

24. Phosphorus Cycle • Phosphorus is an element that is part of many molecules that make up the cells of living organisms. • Plants get the phosphorus they need from soil and water, while animals get their phosphorus by eating plants or other animals that have eaten plants. • The phosphorus cycle is the cyclic movement of phosphorus in different chemical forms from the environment to organisms and then back to the environment.

25. Phosphorus Cycle Continued • Phosphorus may enter soil and water when rocks erode. Small amounts of phosphorus dissolve as phosphate, which moves into the soil. • Plants absorb phosphates in the soil through their roots. • Some phosphorus washes off the land and ends up in the ocean. • Because many phosphate salts are not soluble in water, they sink to the bottom and accumulate as sediment.

27. Fertilizers and the Nitrogen and Phosphorus Cycles • Fertilizers contain both nitrogen and phosphorus. • Excessive amounts of fertilizer can enter terrestrial and aquatic ecosystems through runoff. • Excess nitrogen and phosphorus can cause rapid growth of algae. • Excess algae can deplete an aquatic ecosystem of important nutrients such as oxygen, on which fish and other aquatic organisms depend.

29. Acid Precipitation • When fuel is burned, large amounts of nitric oxide is release into the atmosphere. • In the air, nitric oxide can combine with oxygen and water vapor to form nitric acid. • Dissolved in rain or snow, the nitric acid falls as acid precipitation.

30. Acid rain damage on gargoyle Trees killed by acid rain

31. Sulfur Cycle • Sulfur is one of the components that make up proteins and vitamins. • Proteins consist of amino acids that contain sulfur atoms. • Sulfur is important for the functioning of proteins and enzymes in plants, and in animals that depend upon plants for sulfur. • Plants absorb sulfur when it is dissolved in water. Animals consume these plants, so that they take up enough sulfur to maintain their health.

32. Sulfur Cycle Continued • Most of the earth's sulfur is tied up in rocks and salts or buried deep in the ocean in oceanic sediments. • Sulfur can also be found in the atmosphere. It enters the atmosphere through both natural and human sources. • Natural recourses: volcanic eruptions, bacterial processes, evaporation from water, or decaying organisms. • When sulfur enters the atmosphere through human activity, this is mainly a consequence of industrial processes where sulfur dioxide (SO2) and hydrogen sulphide (H2S) gases are emitted on a wide scale.

33. Sulfur Cycle Continued • When sulfur dioxide enters the atmosphere it will react with oxygen to produce sulfur trioxide gas (SO3), or with other chemicals in the atmosphere, to produce sulfur salts. • Sulfur dioxide may also react with water to produce sulphuric acid (H2SO4). Sulphuric acid may also be produced from demethylsulphide, which is emitted to the atmosphere by plankton species. • All these particles will settle back onto earth, or react with rain and fall back onto earth as acid depostion.

35. Rock Cycle • Group of changes • Igneous rock can change into sedimentary rock or into metamorphic rock • Sedimentary rock can change into metamorphic rock or into igneous rock • Metamorphic rock can change into igneous or sedimentary rock

36. Igneous Rock • Igneous rock forms when magma cools and makes crystals. • Magma is a hot liquid made of melted minerals. The minerals can form crystals when they cool. • Igneous rock can form underground, where the magma cools slowly. Or, igneous rock can form above ground, where the magma cools quickly.

37. Sedimentary Rock • On Earth's surface, wind and water can break rock into pieces. • The rock pieces, called sediments, drop from the wind or water to make a layer. • After a long time the sediments can be cemented together to make sedimentary rock. In this way, igneous rock can become sedimentary rock.

38. Metamorphic Rock • Baked rock does not melt, but it does change. It forms crystals. • Because this rock changes, it is called metamorphic. • Metamorphosis can occur in rock when they are heated to 300 to 700 degrees Celsius.

40. Succession • A regular pattern of changes over time in the types of species in a community • May take hundreds or thousands of years • Climax community – the community that eventually forms if the land is left undisturbed • Two types of succession • Primary succession • Secondary succession

41. Primary Succession • Occurs on surfaces where no ecosystem existed before • New islands created by volcanic eruptions • Land exposed when a glacier retreats • No soil exists • It takes several hundred to several thousand years to produce soil naturally • Pioneer species – first organisms to populate an area (usually lichens) • Lichens → mosses → grasses → shrubs → trees

42. Primary Succession

43. Secondary Succession • Occurs on a surface where an ecosystem has previously existed • Volcanic eruption, forest fire, abandoned farmland • Occurs much more quickly than primary succession because there is already fertile soil