1. Ecosystems: What Are They and How Do They Work?
Chapter 4
Ecosystems: What Are They and How Do They Work?

2. ECOLOGY
Ecology is the study of the connection between organisms and their living and non-living environments.
The average number of organisms that can be sustained in an ecosystem is known as carrying capacity.
Food, water, and shelter are known as limiting factors.
Ecology is the study of the interaction or connection between organisms and their living and non-living environments.

3. F O C U S E D on in L G Y L E V S of O R G A N I Z T Biosphere
Ecosystems
Communities
Populations
Organisms

4. Population Species Community Biome Biosphere Ecosystem
Look at the hierarchy here. Species is the lowest on this hierarchy. This lists from the smallest “unit” to the largest, the Biosphere.
Biosphere
Ecosystem
Species is the lowest on this hierarchy and Biosphere is the largest.

5. Which of these graphs shows a stable population?
homeostasis

6. What are the major parts of the Earth’s life-support systems
What are the major parts of the Earth’s life-support systems? The Spheres of Life.
Atmosphere – thin envelope or membrane of air around the planet
troposphere – inner layer of the atmosphere (extends 11 miles above sea level)
stratosphere – next layer, 11 to 30 miles above Earth’s surface, lower portion contains the ozone layer
Hydrosphere – consists of the Earth’s water
Lithosphere – Earth’s crust and upper mantle; contains nonrenewable fossil fuels and minerals, and renewable soil chemicals (nutrients) needed for plant life
Biosphere – portion of the Earth in which living (biotic) organisms exist and interact with one another and with their nonliving (abiotic) environment

7. Atmosphere (troposphere, stratosphere)
Oceanic crust
Continental crust
Vegetation
and animals
Biosphere
Lithosphere
Upper mantle
Soil
Crust
Asthenosphere
Rock
Lower mantle
core
What are the major parts of the Earth’s life-support systems? The Spheres of Life.
Atmosphere – thin envelope or membrane of air around the planet
troposphere – inner layer of the atmosphere (extends 11 miles above sea level); contains most of Earth’s air
stratosphere – next layer, 11 to 30 miles above Earth’s surface, lower portion contains the ozone layer for filtering out the sun’s UV rays
Hydrosphere – consists of the Earth’s water
Lithosphere – Earth’s crust and upper mantle; contains nonrenewable fossil fuels and minerals, and renewable soil chemicals (nutrients) needed for plant life
Biosphere – portion of the Earth in which living (biotic) organisms exist and interact with one another and with their nonliving (abiotic) environment
Mantle
Crust
(soil and rock)
Biosphere
(Living and dead
organisms)
Atmosphere (troposphere, stratosphere)
(air)
Lithosphere
(crust, top of upper mantle)
Hydrosphere
(water)

8. Solar Capital Solar Energy in = Energy out radiation Reflected by
atmosphere (34%)
UV radiation
Radiated by
atmosphere
as heat (66%)
Lower stratosphere
(ozone layer)
Visible
light
Greenhouse
effect
Absorbed
by ozone
Troposphere
Heat
Absorbed
by the earth
Solar Capital: flow of energy to and from the Earth.
Heat radiated
by the earth
Earth

9. ECOLOGY
Abiotic – All of the non-living elements in an ecosystem like air, water, and temperature.
Biotic – All of the living elements in an ecosystem.

10. Biotic Factors in an Aquatic Ecosystem

11. Abiotic Factors in Terrestrial and Aquatic Ecosystems
• Sunlight
• Temperature
• Precipitation
• Wind
• Latitude (distance from equator)
• Altitude (distance above sea level)
• Fire frequency
• Soil
• Light penetration
• Water currents
• Dissolved nutrient concentrations (especially N and P)
• Suspended solids
• Salinity
Abiotic factors in terrestrial and aquatic ecosystems

12. Ecotones: Ecosystem Boundaries

13. Tolerance
Range of Tolerance: range of chemical and physical conditions that must be maintained for populations of a particular species to stay alive and grow, develop, and function normally.
Law of Tolerance: the existence, abundance, and distribution of a species in an ecosystem are determined by whether the levels of one or more physical or chemical factors fall within the range tolerated by the species.

14. Abundance of organisms
Population Size
Low
High
Temperature
Zone of
intolerance
physiological stress
Optimum range No
organisms
Few
Lower limit
of tolerance
Abundance of organisms
Upper limit
Range of tolerance for a population of organisms, such as fish,
to an abiotic environmental factor—in this case, temperature.

15. Ecology
Biodiversity is the number and variety of organisms found within a certain region.
Extinction is when a species is no longer in existence.
Endangered means a species is in danger of extinction throughout all of a significant portion of its range.

16. ECOLOGY
Food Chain – A chain illustrating the organisms and their food source.
Grass grasshopper bird

17. A food chain illustrates the transfer of energy from one trophic level to the next.

19. ECOLOGY
Food Web – multiple chains assembled into one large web.

20. that shows the relationship between the organisms in
ECOLOGY
Ecological Pyramid
A food chain
that shows the relationship between the organisms in
each trophic level.

21. Ecological Pyramid of Numbers
The figures represent number of individuals counted at each trophic level.

22. Ecological Pyramid of Biomass
The total dry weight of organisms in a particular trophic level is referenced as biomass.
BIOMASS =
# of organisms x
the weight of an average individual
biomass

23. Ecological Pyramid of Energy
Energy in ecosystems flows from producers to consumers.
Energy is depicted in kilocalories.
Ecological efficiency: % of usable
energy transferred from one trophic level to the next. (Average is about 10%.)
Ecological Pyramids of Energy
Energy in ecosystems flows from producers (photosynthetic organisms) to consumers (herbivores and carnivores). Ecological pyramids of energy usually depict the amount of living material (or its energetic equivalent) that is present in different trophic levels. In this diagram, energy is depicted in kilocalories.
Primary producers convert only about 1% of the energy in available sunlight. The average amount of energy that is available to the next trophic level is about 10%. Because so much energy is utilized in building and maintaining organisms, food chains (series of feeding relationships) are usually limited to just three or four steps. Pyramids of energy can not be inverted.

24. Ecological Pyramid of Energy

26. Nutrient Cycles
Cycling of materials between the environment and organisms.
Chemical and biological processes.
Examples:
Water cycle
Carbon cycle
Nitrogen cycle
Phosphorus cycle
Sulfur cycle
Oxygen cycle
Biogeochemical Cycles
Chemical elements essential to life are available in limited amounts and must be cycled between living organisms and the environment. Because these processes involve both chemical and biological processes, they are called biogeochemical cycles. Elements such as carbon (from carbon dioxide), hydrogen, and nitrogen move between the atmosphere and organisms, while elements such as phosphorus, calcium, potassium, magnesium, sodium, and iron enter into organisms from the soil. The four primary biogeochemical cycles are water, nitrogen, carbon, and phosphorus.

27. Water (Hydrologic) Cycle
Condensation
Rain clouds
Precipitation
Transpiration
from plants
Precipitation
Precipitation
to ocean
Transpiration
Evaporation
Surface runoff (rapid)
Evaporation
From
ocean
Runoff
Infiltration and
percolation
Surface runoff
(rapid)
Groundwater movement (slow)
Ocean storage
Groundwater movement (slow)

28. Carbon Cycle Carbon Cycle
Carbon, in the form of carbon dioxide, comprises about 0.03 percent of the atmosphere. Worldwide circulation of carbon atoms is called the carbon cycle. Since carbon becomes incorporated into molecules used by living organisms during photosynthesis, parts of the carbon cycle closely parallel the flow of energy through the earth’s living systems. Carbon is found in the atmosphere, the oceans, soil, fossil deposits and living organisms. Photosynthetic organisms create carbon-containing molecules (known as “organic” compounds), which are passed to other organisms as depicted in food webs. Each year, about 75 billion metric tons of carbon are trapped in carbon-containing compounds through photosynthesis. Carbon is returned to the environment through respiration (breakdown of sugar or other organic compounds), combustion (burning of organic materials, including fossil fuels), and erosion.

29. Nitrogen Cycle Nitrogen Cycle
A major component of the atmosphere, nitrogen is essential for all living things. However, most organisms are unable to use the gaseous forms of nitrogen present in the atmosphere. In order for nitrogen to be usable by most organisms, it must be “fixed,” in other words, combined with oxygen, hydrogen or carbon to form other molecules. Nitrogen fixation can happen during rainstorms, which yields nitrate and ammonium ions. Nitrogen also can be fixed biologically by free-living and symbiotic bacteria. Leguminous plants, for example, host nitrogen-fixing bacteria in root nodules allowing them to capture nitrogen and incorporate it into proteins and other molecules.
Unlike other organisms, nitrogen fixing bacteria are able to convert atmospheric nitrogen to ammonia, which then can serve as raw material for the incorporation of nitrogen into other molecules. The other four important steps in the nitrogen cycle are: (1) assimilation (reduction of nitrate ions [NO2-] inside plants to ammonium ions [NH4+], which are used to manufacture proteins and other molecules; this conversion requires energy); (2) ammonification (release of excess nitrogen in the form of ammonia [NH3] and ammonium ions [NH4+] by soil-dwelling bacteria and some fungi during the decomposition of complex organic compounds such as proteins, and nucleic acids); (3) nitrification (the oxidation of ammonium ions or ammonia by free-living, soil dwelling bacteria to nitrates [NO2-]; and (4) denitrification (the conversion of nitrate to gaseous nitrogen [N2 ] by free-living bacteria in soil; this conversion yields energy and occurs in conditions with low levels of oxygen).

30. Nitrogen Cycle Nitrogen Fixation: bacteria convert nitrogen to ammonia
Nitrification: bacteria convert ammonia to nitrite and nitrate, which are used by plants
Assimilation: plant roots absorb ammonia and nitrate
Ammonification: decomposers convert dead organisms and waste to simpler compounds
Denitrification: bacteria convert ammonia back into nitrite and nitrate, which are released into the air (cycle begins again)

31. Phosphorus Cycle Erosion Phosphate Rock Phosphate Mining
Fertilizer containing phosphates
Animal waste
Uplifting into rocks
Animal Excretion
Dissolved Phosphates

32. The Sulfur Cycle