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Chapter 5: How Ecosystems Work

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1 Chapter 5: How Ecosystems Work
Energy Flow in the Ecosystem The Cycling of Matter How Ecosystems Change p

2 Key terms Photosynthesis Producer Consumer Decomposer
Cellular respiration Food chain Food web Trophic level Carbon cycle Nitrogen-fixing bacteria Nitrogen cycle Phosphorus cycle Ecological succession Primary succession Secondary succession Pioneer species Climax community

3 5.1 Energy Flow in the Ecosystem
Describe how energy is transferred from the sun to producers and then to consumers Describe one way in which consumers depend on producers List 2 types of consumers Explain how energy transfer in a food web is more complex than a food chain Explain why an energy pyramid is a representation of trophic levels

4 Life Depends on the Sun All life is dependent on the sun for energy.
Plants algae and some bacteria use the suns energy and convert it into sugars/carbohydrates by photosynthesis

5 From producers to consumers
Producer- autotrophs or self-feeders makes only energy by photosynthesis or chemosynthesis Consumer- other feeders or heterotrophs- eat other organisms to survive

6 Consumers- have to eat Heterotrophs- can not make own food, eat other organisms Grouped based on types of food they eat: Herbivores- eat producers (antelope) Carnivores- eat other consumers (lion) Omnivores- eat producers and consumers (grizzly bear) Detritivores- consumers that feed on wastes, dead organisms (vulture) Decomposers- break down organisms (bacteria, fungi) Ecology 2010

7 Cellular Respiration: Burning the Fuel
If oxygen is available, organisms can obtain energy from food by a process called cellular respiration. The summary of cellular respiration is presented below. In symbols: 6 O2 + C6H12O6  6 CO2 + 6 H2O + ATP (Energy) In words: Oxygen + Glucose  Carbon dioxide + Water + Energy The cell has to release the chemical energy in food molecules (like glucose) gradually, otherwise most of the energy would be lost in the form of heat and light. Cellular Respiration 2009

8 Energy transfer All organisms need energy to carry out essential functions, such as growth, movement, maintenance and repair, and reproduction. In an ecosystem, energy flows from the sun to autotrophs, then to organisms that eat the autotrophs, and then to organisms that feed on other organisms. The amount of energy an ecosystem receives and the amount that is transferred from organism to organism affect the ecosystem's structure. Ecology 2010

9 Energy Flow Transfer of energy from one organism to another
Trophic levels- organism’s position in a sequence of energy transfers Food chain- single pathway of feeding relationships between organisms in an ecosystem that results in energy transfer Food web- interconnected food chains Web cd 37 c, d, e Ecology 2010

10 Food Chains A food chain is a series of steps in which organisms transfer energy by eating and being eaten. Food chains can vary in length. An example from the Everglades is shown. Ecology 2010

11 Ecology 2010

12 Food Webs In most ecosystems, feeding relationships are much more complicated than the relationships described in a single, simple chain because many animals eat more than one kind of food. Ecologists call this network of feeding interactions a food web. An example of a food web in the Everglades is shown. Ecology 2010

13 Ecology 2010

14 Limitations on trophic levels
Only 10% of the energy available at one trophic levels is transferred to the next trophic level not enough to support more levels Higher tropic levels contain less energy  support fewer organisms Ecology 2010

15 Ecology 2010

16 Pyramids of Biomass and Numbers
The total amount of living tissue within a given trophic level is called its biomass. The amount of biomass a given trophic level can support is determined, in part, by the amount of energy available. Ecology 2010

17 Ecology 2010

18 Ecology 2010

19 Ecology 2010

20 5.2The Cycling of Materials
Describe the short term and long term process of the carbon cycle. Identify one way that humans are affecting the carbon cycle. List the three stages of the nitrogen cycle Describe the role that nitrogen fixing bacteria play in the nitrogen cycle Explain how the excess use of fertilizer can affect the nitrogen and phosphorus cycles.

21 Recycling in the Biosphere
Unlike the one-way flow of energy, matter is recycled within and between ecosystems. Elements pass from one organism to another and among parts of the biosphere through closed loops called biogeochemical cycles, which are powered by the flow of energy. Ecology 2010

22 4 major cycles Water cycle Carbon cycle Nitrogen cycle
Phosphorus cycle Web cd 37 f, g, h, 10min video Ecology 2010

23 Carbon Cycle Short term:
Plant convert carbon dioxide into carbohydrates during photosynthesis Consumers eat the plants break down carbon during cellular respiration Long Term: carbon converted into carbonates (bones and shells) limestone rock (largest carbon reservoirs) Carbon also converted into fats, oils, other energy storing molecules release into soil or air after the organism dies can form coal or natural gas(fossil fuels)

24 How Humans Affect the Carbon Cycle
Burn fossil fuels  release carbon into air 6 billion metric tons of carbon is released per year about ½ will remain in the air increasing CO2 into the air at steady rate  global warming increase the temperature of the Earth


26 The Nitrogen Cycle All organisms need nitrogen to build proteins
78% of the gases in the atmosphere Must be altered in a usable form Nitrogen fixing bacteria- bacteria that can fix nitrogen- take gas and transform it to a usable form (nitrate), key part in the nitrogen cycle Legumes- beans, peas, clover that bacteria can live in nodules Gets released into the soil plants absorb it and then consumers eat them Decomposers break down decaying and dying things putting the nitrogen back into the cycle


28 The Phosphorus Cycle Makes up cells of living organisms (bones and teeth) Plants get it from soil and water consumers get it from eating plants or other organisms Phosphorus goes from environment to organisms rarely occurs as a gas No soluble in water sink to bottom Fertilizers- contain nitrogen and phosphorus, great for plants and alga (algal bloom) can disrupt or deplete oxygen in aquatic ecosystems Acid Rain- burning fuel  nitric oxide is released  acid rain Video- Song- Acid rain-


30 5.3 How Ecosystems Change List two examples of ecological succession
Explain how a pioneer species contributes to ecological succession Explain what happens during old-field succession Describe how lichens contribute to primary succession

31 THINK ABOUT IT In 1883, the volcanic island of Krakatau in the Indian Ocean was blown to pieces by an eruption. The tiny island that remained was completely barren. Within two years, grasses were growing. Fourteen years later, there were 49 plant species, along with lizards, birds, bats, and insects. By 1929, a forest containing 300 plant species had grown. Today, the island is blanketed by mature rain forest. How did the island ecosystem recover so quickly? Ecology 2010

32 Succession- changes Ecological succession- gradual regrowth of a community of species Primary- development of a community in an areas that has not supported life previously, sand dune, rock Web cd 37 b Secondary- replace of species that follows the disruption (soil is present) Pioneer species- small, grow quick, reproduce quick, invade disturbed habitats Climax community- stable end pt Song: Ecology 2010

33 Primary Succession Volcanic explosions can create new land or sterilize existing areas. Retreating glaciers can have the same effect, leaving only exposed bare rock behind them. Succession that begins in an area with no remnants of an older community is called primary succession. Ecology 2010

34 Primary Succession For example, in Glacier Bay, Alaska, a retreating glacier exposed barren rock. Over the course of more than 100 years, a series of changes has led to the hemlock and spruce forest currently found in the area. Changes in this community will continue for centuries. Ecology 2010

35 Primary Succession The first species to colonize barren areas are called pioneer species. One ecological pioneer that grows on bare rock is lichen—a mutualistic symbiosis between a fungus and an alga. Ecology 2010

36 Secondary Succession Sometimes, existing communities are not completely destroyed by disturbances. In these situations, secondary succession occurs. Secondary succession proceeds faster than primary succession, in part because soil survives the disturbance. As a result, new and surviving vegetation can regrow rapidly. Secondary succession often follows a wildfire, hurricane, or other natural disturbance. We think of these events as disasters, but many species are adapted to them. Although forest fires kill some trees, for example, other trees are spared, and fire can stimulate their seeds to germinate. Secondary succession can also follow human activities like logging and farming. Ecology 2010

37 Why Succession Occurs Every organism changes the environment it lives in. One model of succession suggests that as one species alters its environment, other species find it easier to compete for resources and survive. For example, as lichens add organic matter and form soil, mosses and other plants can colonize and grow. As organic matter continues to accumulate, other species move in and change the environment further. Over time, more and more species can find suitable niches and survive. Ecology 2010

38 Climax Communities Ecologists used to think that succession in a given area always proceeds through the same stages to produce a specific and stable climax community. Recent studies, however, have shown that succession doesn’t always follow the same path, and that climax communities are not always uniform and stable. Ecosystems may or may not recover from extensive human-caused disturbances. Clearing and farming of tropical rain forests, for example, can change the microclimate and soil enough to prevent regrowth of the original community. Ecology 2010

39 Ecology 2010

40 Mount St. Helens: Back From The Dead
Part 1: Part 2: Part 3: Part 4: Part 5: Part 6:

41 More links

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