1. Ch. 5 How Ecosystems Work
Bellringer – Read in CH. 5 to answer these questions

2. Chapter 5 Objectives 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.

3. I. Energy Flow in Ecosystems
A. Life Depends on the Sun
Photosynthesis – when plants use sunlight to make sugar molecules
-performed by plants, algae, and some bacteria
- 6CO2 + 6H2O + solar energy = C6H12O6 + 6O2

4. I. Energy Flow in Ecosystems
Result of photosynthesis is energy rich molecules called carbohydrates
When an animal eats a plant some energy is transferred from the plant to the animal, and use this energy to
grow, move, and reproduce.

5. I. Energy Flow in Ecosystems
Producer – an organism that makes its own food – an autotroph
-organisms that perform photosynthesis
Consumer – organisms that get their energy by eating other organisms – heterotrophy
All organisms get their energy from the sun either by using it directly through photosynthesis like producers, or indirectly by eating producers or other consumers

6. I. Energy Flow in Ecosystems
In 1977 scientists discovered areas on the bottom of the ocean that were full of life even though sunlight did not reach
-deep ocean communities got their energy from bacteria who could use hydrogen sulfide from the hot water vents to make their own food
-these bacteria served as the food for other organisms so a whole ecosystem could be supported

7. B. What Eats What
Organisms can be classified by the source of their energy
Herbivores – consumers that eat only producers – plant-eaters
Carnivores – consumers that eat other consumers – meat-eaters
Omnivores – consumers that eat both producers and consumers – all-eaters
Decomposers – consumers that get their food by breaking down dead organisms -bacteria and fungi

8. C. Cellular Respiration: Burning the Fuel
Your body gets the energy out of the food by using the oxygen you breathe to break down the food
-you are then able to use the energy stored in the food
Excess energy is stored as fat or sugar.

9. C. Cellular Respiration: Burning the Fuel
Cellular respiration – process of breaking down food to yield energy
-occurs inside cells of most organisms including plant and animals
You use the energy to walk, breathe, think, or play a sport, to make more body tissues, fight disease, grow, stay healthy

10. D. Energy Transfer
Each time one organism eats another, a transfer of energy occurs
According to the second law of thermodynamics – at each energy transfer only 10% is available at the next level, the rest is lost as heat

11. You can trace the transfer of energy as it travels through an ecosystem by studying food chains, food webs, and trophic levels
Food chain – a sequence in which energy is transferred from one organism to the next as each organism eats another organism
In an ecosystem, energy flow is usually more complex because there are so many species interacting
Food web – shows many feeding relationships that are possible in an ecosystem

12. Food Web
Food Chain

13. Trophic Levels
Trophic level – each step in the transfer of energy through a food chain or web
-each time energy is transferred from one organism to another, some of the energy is lost as heat and less is available to organisms at the next level
90 percent of the energy at each trophic level is used to carry out the functions of living such as producing new cells, regulating body temperature, and moving around

14. Trophic Levels
10 percent becomes used as part of the organisms body and stored in its molecules – this is what is available to the next trophic level when one organism consumes another
Energy pyramid is used to visualize the loss of energy from one trophic level to the next
-each layer represents one trophic level

15. Trophic Levels
producers form the base because they contain the most energy
-herbivores make up the next level because they contain less energy
-carnivores that feed on herbivores make up the next level
-carnivores that feed on carnivores make up the top level

16. Trophic Levels

17. The decreased amount of energy at each trophic level affects the organization of an ecosystem
-because so much energy is lost at each level, there are fewer organisms at the higher trophic levels
-zebras and other herbivores outnumber lions on the African savanna by about 1000 to 1
-the loss of energy limits the number of trophic levels in an ecosystem
-rarely are there more than 4 or 5 trophic levels because the ecosystem does not have enough energy left to support higher levels

18. What would be at the very top of the pyramid?
only animals that feed on organisms at the top trophic levels are usually very small like parasitic worms, or fleas that require very small amounts of energy
decomposers get energy from all levels

19. Bellringer

20. Objectives List the three stages of the carbon cycle.
Describe where fossil fuels are located.
Identify one way that humans are affecting the carbon cycle.
List the tree 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. II. The Cycling of Materials
A. The Carbon Cycle
Carbon is an essential part of all living things
Carbon cycle – a process by which carbon is cycled between the atmosphere, land, water, and organisms
The carbon cycle is the movement of carbon from the nonliving environment into living things and back
Carbon is the essential component of proteins, fats, and carbohydrates, which make up all organisms.

22. The Carbon Cycle

23. The Long & Short of Cycles
-a short term cycle is when producers like plants convert CO2 in the air into glucose during photosynthesis
-when consumers eat the producers, the consumers obtain carbon from the carbohydrates
-consumers break down the food during cellular respiration some of the carbon is released back into the air as carbon dioxide
-some carbon enters a long-term cycle if carbon is converted into carbonates which make up the hard parts of bones and shells

24. As a Long Term Cycle
over millions of years carbonate deposits produce huge formations of limestone rocks
-limestone is one of the largest carbon sinks or carbon reservoirs on Earth
-carbon can be released into the soil or air after an organism dies and decomposes
-these molecules can form deposits of coal, oil, and natural gas underground called fossil fuels
-these are essentially stored carbon left over from bodies of plants and animals that died millions of years ago

25. Humans affect the carbon cycle
When we burn fossil fuels, we release carbon into the atmosphere as carbon dioxide
-cars, factories, and power plants rely on these fossil fuels to operate
-about 6 billion metric tons of carbon a year are released as CO2

26. Other Affects - 6 billion metric tons
-natural burning of wood or forest fires combined with fossil fuels to make this number
-half of this remains in the atmosphere, so over a period of years the amount of carbon dioxide in the atmosphere has steadily increased
-increased levels of carbon dioxide may contribute to global warming – an overall increase in the temperature of the Earth
-some excess CO2 is absorbed by the ocean which is another carbon sink, plants absorb some too

27. B. The Nitrogen Cycle
All organisms need protein which is essential for new cells - nitrogen is needed for proteins.
Nitrogen makes up 78% of the gases in the atmosphere, but organisms cannot take in and use atmospheric nitrogen

28. Nitrogen Fixation
Nitrogen must be altered, or fixed, before organisms can use it
The only organisms that can fix nitrogen is bacteria called nitrogen-fixing bacteria
-all organisms depend on these bacteria to supply nitrogen
Bacteria are an important part of nitrogen cycle

29. Nitrogen Cycle

30. Nitrogen cycle
Nitrogen cycle– a process in which nitrogen is cycled between the atmosphere, bacteria, and other organisms
-bacteria take nitrogen from the air and transforms it into molecules that living things can use
-the bacteria live within nodules on the roots of plants called legumes – beans, peas, clover
-they use sugars provided by the legumes to produce nitrogen-containing compounds like nitrates
-the excess nitrates are released into the soil

31. Animals get nitrogen by eating plants or other animals
After nitrogen cycles from the atmosphere into living things, it is returned to the atmosphere by bacteria
-decomposers are essential to the nitrogen cycle because the break down wastes such as urine, dung, leaves, and other decaying plant and animal matter and return the nitrogen that these organisms and wastes contain to the soil
-after decomposers return the nitrogen to the soil, bacteria transform a small amount of the nitrogen into nitrogen gas which returns to the atmosphere

32. C. The Phosphorus Cycle
Phosphorus is part of many molecules that make up the cells of living organisms
Essential in forming bones and teeth
Plants get phosphorus from soil and water, and animals get it by eating plants or plant-eaters

33. Phosphorus cycle
Phosphorus cycle – the movement of phosphorus from the environment to organisms and then back to the environment
-this cycle is slow and does not normally occur in the atmosphere because phosphorus rarely occurs as a gas
-phosphorus enters the cycle when rocks erode, small amounts of phosphorus dissolve as phosphate in soil and water
-plants absorb phosphates in the soil through their roots

34. Phosphorus cycle
-phosphorus also enters the cycle when added to soil and water when excess phosphorus is excreted in waste
from organisms and when organisms die and decompose
-some phosphorus also washes off the land and eventually ends up in the ocean
-phosphate salts are not soluble in water and so they sink to the bottom of the ocean and accumulate as sediment

35. Phosphorus Cycle

36. Human effects Humans effect the Nitrogen and Phosphorus cycle
-people often apply fertilizers to stimulate and maximize plant growth
-fertilizers contain both nitrogen and phosphorus
-the more nitrogen and phosphorus available to a plant, the faster and bigger the plant tends to grow
If excessive amounts of fertilizer are used, the fertilize can enter terrestrial and aquatic ecosystems through runoff

37. Phosphorus cycle
-this can cause rapid and over-abundant growth of algae resulting in an algal bloom – a dense, visible patch of algae that occurs near the surface of the water
(Eutrophication)
-bacteria break down the dead algae and plants depleting the oxygen from the water causing fish and other aquatic organisms to die

38. Nutrient Cycles can be harmful
When we burn coal, wood, or oil, a large amount of nitric oxide is release into the atmosphere
-this is a harmful gas and when it combines with oxygen and water vapor to form nitric acid (NOX)
-nitric acid dissolves in rain and snow contributing to acid precipitation

39. Bellringer

40. Objectives 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.

41. III. How Ecosystems Change
A. Ecological Succession
Ecological succession – a gradual process of change and replacement of the types of species in a community
Primary succession – a type of succession that occurs on a surface where no ecosystem existed before
-rocks, cliffs, sand dunes

42. Secondary succession
Secondary succession – the more common type of succession where succession occurs on a surface where an ecosystem has previously existed
-areas that have been disturbed by humans, animals or natural processes such as storms, floods, fires, earthquakes, volcanoes
Example – Mount St. Helens eruption wiped out everything

43. Mount St. Helens Succession
the first species to regrow were pioneer species – the first organisms to colonize any newly available area and begins the process of ecological succession
-pioneer species makes the area habitable for other species
-tend to be smaller species like mosses and grasses
-they are replaced by larger and larger organisms

44. climax community -climax community – a final and stable community
Natural fires caused by lightening are a necessary part of secondary succession
-some trees release seeds only when exposed to the heat of a fire
-minor fires remove the brush and deadwood that would otherwise contribute to major fires burning out of control
-some animal species feed on vegetation that only sprouts after fires

45. Ecological Succession

46. Old-field succession
Example of secondary succession is old-field succession
Old-field succession – occurs when farmland is abandoned when a farmer stops cultivating a field
-grasses and weeds quickly build up
-over time taller plants move into the area
-taller plants gradually replace smaller ones
-finally the slower growing trees like oaks, hickory, beech, and maple take over

47. Primary succession
Primary succession is much slower than secondary succession because it begins where there is no soil
-it can take several hundred to several thousand years to produce fertile soil
-lichens are usually the first pioneer species because they can live with no soil
Lichens are composed of a fungus and an algae

48. How it happens
as the lichen grows it breaks down the rock and soil slowly accumulates as dust particles in the air are trapped in cracks in the rock
-dead remains of lichens and bacteria accumulate in the cracks
-mosses may grow larger and break the rock even more, then they die and decay and add material and nutrients to the growing soil
-fertile soil is formed from broken rock, decayed organisms, water, and air

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50. Quick Lab