1. Chapter 5: How Ecosystems Work 5-1 Energy Flow in Ecosystems
Today’s Objectives:
Demonstrate an understanding of Ch. 4.
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 energy transfer in a food chain.
Explain why an energy pyramid is a representation of trophic levels.

2. Life Depends on the Sun
Nearly all energy in an ecosystem ultimately comes from the sun.
Photosynthesis: plants use sunlight to make sugar (carbohydrates)
CO2 + H2O + Sun  C6H12O6 + O2
Carbon dioxide + water + solar energy  glucose (sugar) + oxygen
Carbohydrates: energy-rich molecules used by organisms.
Chemosynthesis (an exception)
Some deep-ocean bacteria can use hydrogen sulfide to make their own food without sunlight
So, how do we burn this fuel???
Cellular Respiration – breaking down food to yield energy
C6H12O6 + O2  CO2 + H2O + Energy

3. What Eats What in an Ecosystem
Energy Source
Examples
Producer
a.k.a.
autotroph
Makes its own food through photosynthesis or chemosynthesis
Plants, algae, some bacteria
Consumer
heterotroph
Gets energy be eating producers or other consumers
Animals (mice, starfish, elephants, turtles, humans, ants), fungi, some protists and bacteria

4. Types of Consumers in an Ecosystem
Energy Source
Examples
Herbivore
Producers (plants)
Cows, sheep, deer, grasshoppers
Carnivore
Other consumers (“meat”)`
Lions, hawks, snakes, spiders, sharks, alligators, whales
Omnivore
Both producers & consumers (“meat & veggies”)
Bears, pigs, gorillas, rats, raccoons, cockroaches, some insects, humans (most)
Decomposer
Breaks down dead organisms in an ecosystem and returns nutrients to soil, water, and air
Fungi and bacteria

5. Energy Transfer Through Ecosystems
Primary Productivity: amt. of organic material that the photosynthetic organisms of an ecosystem produce
- Determines the energy budget (amount of available energy) of an ecosystem!

6. Trophic Level = Energy Level
1st T.L. = producers (plants, algae, bacteria)
2nd T.L. = primary consumers (herbivores- eat the producers)
3rd T.L. = secondary consumers eat herbivores (carnivores & omnivores)
4th T.L. = tertiary / top consumers (carnivores that consume other carnivores)

7. Food Chain: linear path of energy transfer through the trophic levels of an ecosystem
ex. PlantRatSnakeEagle

8. Food Web: network of feeding relationships in an ecosystem
Food Web: network of feeding relationships in an ecosystem *organisms usually feed at several trophic levels

10. Energy Transfers Between Tropic Levels are Very Inefficient
Biomass: dry weight of living tissue used to determine the amount of energy present in trophic levels
10% Rule: On average, only 10% (90% less) of the energy or biomass in any trophic level will be incorporated into the next level.

11. Pyramid of Energy/Biomass: block diagram that portrays the flow of energy through an ecosystem.

14. Energy Loss Limits the Number of Tropic Levels in an Ecosystem
Most terrestrial (land) ecosystems involve only 3 or, rarely, 4 trophic levels
Too much energy is lost (mostly as HEAT) at each level to allow more levels!

15. Food Web & Pyramid Cut & Paste
Groups of 2
Create - 1 Pyramid, 1 Web
*arrows go from food source to food consumer*
Label all – Autotroph, heterotroph, consumer, producer, decomposer, herbivore, carnivore, omnivore

16. 5-2 The Cycling of Materials
Biogeochemical Cycles: Materials Cycle (recycled/reused) Between Organisms and the Nonliving Environment
Water, Carbon, Nitrogen, and Phosphorous are essential for life – each is recycled.

18. The Water Cycle It’s driven by the sun
condensation: gas to liquid
precipitation: water falls to the earth’s surface
Runoff
groundwater
transpiration: “Plant Sweat” water evaporating from the leaves of plants
respiration: organisms give off water vapor
evaporation: liquid to gas
How humans affect the water cycle: When forests are cut down, the water cycle is disrupted and less moisture is returned to the atmosphere.

20. The Carbon Cycle Linked to the flow of energy.
Atmospheric CO2 (carbon dioxide)
Carbon taken in by plants (enters the living portion of the carbon cycle) through photosynthesis.
Heterotrophic Nutrition (animals eat plants)
Organisms release CO2 through cellular respiration.
Fossil Fuels (coal, oil, natural gas) – stored carbon left over from bodies of plants and animals that died millions of years ago
Combustion – burn fossil fuels – releases CO2 back into the atmosphere
Decomposition – carbon from carbohydrates in organisms (converted into fats, oils, etc.) is released into the soil or air after an organism dies – some can form deposits of fossil fuels
carbonates - hard parts of bones & shells – don’t break down easily
carbon sinks (carbon reservoirs {store more carbon than they release}) – over millions of years carbonate deposits produce huge formations of limestone rocks (one of the largest carbon sinks on Earth)
- the ocean is also a carbon sink

21. How humans affect the carbon cycle:
Burning fossil fuels releases CO2 into the atmosphere (cars, factories, power plants, forest fires, etc.). The amount of CO2 is steadily increasing and contributes to global warming (an overall increase in the temperature of the Earth).
Deforestation (cutting down/burning forests) adds CO2 to the atmosphere as forests are burned (mainly to create agricultural land), and by destroying trees that take CO2 out of the atmosphere by photosynthesis.

22. The Nitrogen Cycle

23. The Nitrogen Cycle
Nitrogen – needed by organisms (DNA, amino acids / proteins…)
1. Nitrogen Gas (N2) - 79% of air, BUT not usable by plants
Part I: Nitrogen Fixation – making nitrogen gas (N2) into nitrogen that plants can use (ammonia, nitrates)
2. N2—lightning nitrates (dissolved in rain)
3. N2—heat/pressurefertilizer
9. N2—bacteriaammonia
Part II: Food Web
4, 5. Absorption of nitrogen by Plants – make amino acids / protein
6. Nutrition - Animals eat plants – nitrogen moves through food web
7. DECAY excretions/dead stuff—bacteriaammonia
Part III: 8. Denitrification
Nitrates—bacterianitrogen gas

24. How humans affect the nitrogen cycle:
1. Fertilizers and the Nitrogen & Phosphorous Cycle
Fertilizers – contain nitrogen & phosphorous
More nitrogen and phosphorous = faster/bigger plant growth
Excessive amounts of fertilizer runoff land and enter terrestrial and aquatic ecosystems / nearby water ways
Causes Algal Bloom: rapid and over abundant growth of algae – dense, visible patches near the surface of the water
Algal blooms and plants and animals that break down algae can deplete nutrients (like oxygen) from aquatic ecosystems
Fish and other aquatic organisms need oxygen to survive
2. Acid Precipitation
Burning fuel releases nitric oxide (a harmful gas) into the atmosphere
Nitric oxide + water vapor  nitric acid
Acid Precipitation = nitric acid dissolved in rain / snow

25. 5-3 How Ecosystems Change
Ecological Succession: replacement of one kind of community by another over time
ex. lichengrassbushespineoak

26. Primary Succession: nothing has grown there before (rocks, cliffs, sand dunes, new volcanic islands)
Secondary Succession: there has been previous growth – disturbed by humans (abandoned fields, forest clearings) , animals, or natural processes (storms, floods, earthquakes, volcanoes
Fire & Secondary Succession: natural fires (caused by lightning) are a necessary part of succession (some species of trees release seed during fires, removes brush and deadwood that would otherwise fuel even bigger fires)
Old-field Succession: when farmland is abandoned
Pioneer grasses & weedsperennial grassesshrubspine foresthardwood forest

27. Secondary Succession 12 years after the eruption of Mt. St. Helens

28. Pioneer Organisms / Pioneer Species = 1st organisms – 1st organisms to colonize a newly available area
Commonly bacteria or lichens (can live w/out soil and help break down rock surfaces into soil)
Lichens: fungus & algae together
Climax Community: when succession ends - among the most stable of ecosystems, remaining relatively unchanged for long periods of time

29. Pioneer Organisms
Lichen Plants growing through cracks in a parking lot.