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Levels Within Levels

An ecosystem is a collection of all the organisms that live in a particular place, together with their nonliving, or physical, environment. Within an ecosystem, there are several levels of organization. Your school and its grounds are similar to an ecosystem.

Section 3-1

Interest Grabber

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1. What living things are found in and around your school?

2. What nonliving things are found in your school?

3. Into what large groups are the students in your school divided?

4. Into what smaller groups are these large groups divided?

5. Are these groups ever divided into even smaller groups? If so, what are these groups?

Section 3-1

Interest Grabber continued

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3–1 What Is Ecology? A. Interactions and Interdependence B. Levels of Organization C. Ecological Methods

1. Observing 2. Experimenting 3. Modeling

Section 3-1

Section Outline

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Interactions and Interdependence • Ecology is the scientific study of interactions among organisms and between organisms and their environment. • The largest environment in which living organisms can be found is called the biosphere. • It extends 8 km above Earth’s surface to about 11 km below the surface of the ocean. • Interactions within the biosphere produce a web of interdependence between organisms and the environment in which they live. • Earth has an ever-changing, or dynamic, biosphere.

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Levels of Organization

• To understand relationships within the biosphere, ecologists ask questions about events and organisms that range in complexity from a single individual to the entire biosphere.

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Section 3-1

Figure 3-2 Ecological Levels of Organization

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Ecological Methods

• Regardless of the tools they use, scientists conduct modern ecological research using three basic approaches: observing, experimenting, and modeling. All of these approaches rely on the application of scientific methods to guide ecological inquiry.

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Ecological Methods

Chemical Testing

Sites

Computer/ Calculators

Written Record

Magnifying Tools

Measuring Tools

Observation Experiment Model Building Field site Experimental plots,

field sites, laboratory Many sites for data collecting

Tapes, compass, Global Positioning System, thermometer, sensors

Tapes, compass, Global Positioning System, thermometer, sensors

Aerial views, Global Positioning System, weather balloons

Binoculars, microscope, telescope

Binoculars, microscope, telescope

Satellite images

Notes, automated data storage

Notes, automated data storage

Automated data storage

Test kits Test kits Large database, multiple sensors

Mathematical analysis and graphics, statistics

Mathematical analysis and graphics, statistics

Mathematical analysis and graphics, statistics, simulations

Section 3-1

Compare/Contrast Table

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Pass It Along

Energy flows in one direction through an ecosystem, from the sun or inorganic compounds to producers (organisms that can make their own food) through various levels to consumers (organisms that rely on other organisms for food). Your body gets the energy and materials it needs for growth and repair from the foods you eat.

Section 3-2

Interest Grabber

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1. Make a list of five foods that you like to eat. Indicate whether the food comes from a plant (producer) or an animal (consumer).

2. Like many birds, chickens eat grains, which are seeds. Where do seeds come from?

3. Meat comes from beef cattle. What do cattle eat?

4. Construct a diagram showing how one of your favorite foods obtains its energy. Include as many levels as you can.

Section 3-2

Interest Grabber continued

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3–2 Energy Flow A. Producers

1. Energy From the Sun 2. Life Without Light

B. Consumers C. Feeding Relationships

1. Food Chains 2. Food Webs 3. Trophic Levels

D. Ecological Pyramids 1. Energy Pyramid 2. Biomass Pyramid 3. Pyramid of Numbers

Section 3-2

Section Outline

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Flow of Energy

sun

Producer (Autotrophs)

Photosynthesis (CO2 + H2O + Energy O2 + Glucose)

(sun)

Plants Bacteria Algae

Light rays

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Chemosynthesis

Deep Sea Vents Hot Springs Tidal Marshes

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Flow of Energy

Consumers (Heterotrophs)

Respiration (O2 + Glucose --> CO2 +H2O + Energy)

(ATP)

Herbivore Carnivore Omnivore Detritivore Decomposer

Plants Animals Both Remains Breaks Down Material

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Feeding Relationships

• Energy flows through an ecosystem in one direction, from the sun, or inorganic compounds, to autotrophs and then, to various heterotrophs. • This energy is passed along in a series of steps in which organisms eat or are eaten. • This is called a food chain.

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Food Webs

• A food web is a series of food chains that overlap in an ecosystem. • Trophic Level - each step in a food chain. • Each consumer depends on the trophic level below it for energy.

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Energy Pyramid

• Only part of the energy that is found in a trophic level is passed on to the next. • Why? • The organisms use the energy to carry out the life processes. • Only about 10% of the energy is passed on to the next trophic level.

Ecological Pyramids

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Biomass Pyramid

• The total amount of living tissue within a given trophic level is called biomass. • Biomass is express in terms of grams of organic matter per unit area. • The biomass pyramid expresses the amount of potential food available for each trophic level in an ecosystem.

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Pyramid of Numbers

• This pyramid is based on the number of organisms found in the ecosystem. • Most of the time, the shape of the pyramid is the same as the biomass and energy pyramids. • However, sometimes the shape changes. An example would be a forest ecosystem.

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Pyramid of Numbers Shows the relative number of individual organisms at each trophic level.

Biomass Pyramid Represents the amount of living organic matter at each trophic level. Typically, the greatest biomass is at the base of the pyramid.

Energy Pyramid Shows the relative amount of energy available at each trophic level. Organisms use about 10 percent of this energy for life processes. The rest is lost as heat.

Section 3-2

Ecological Pyramids

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It’s Raining, It’s Pouring

How many times have you had to change your plans because of rain? It probably didn’t help if someone tried to cheer you up by saying, “But we really need the rain.” However, rain is important. If it didn’t rain, how would living things on land get water?

Section 3-3

Interest Grabber

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1. When rain falls on the ground, it either soaks into the soil or runs across the surface of the soil. When rainwater runs across the land, what body of water might collect the rain?

2. From here, where might the water flow?

3. After the rain, the sun comes out and the land dries. Where does the water that had been on the land go?

4. Construct a diagram that would illustrate all the places a molecule of water might go. Begin with a raindrop and end with a cloud.

Section 3-3

Interest Grabber continued

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3–3 Cycles of Matter A. Recycling in the Biosphere B. The Water Cycle C. Nutrient Cycles

1. The Carbon Cycle 2. The Nitrogen Cycle 3. The Phosphorus Cycle

D. Nutrient Limitation

Section 3-3

Section Outline

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Recycling in the Biosphere

•  Unlike the one-way flow of energy, matter is recycled within and between ecosystems.

•  Matter is passed from one organism to another and from one part of the biosphere to another through biogeochemical cycles.

•  Matter can cycle through the biosphere because biological systems do not use up matter, they transform it.

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The Water Cycle

•  All living things require water to survive as it moves through the ocean, atmosphere and land.

•  Water enters the atmosphere through the processes of evaporation and transpiration and becomes vapor.

•  As the vapor cools, it condenses to form tiny droplets. •  When the droplets get large enough, they fall back to

Earth in the form of precipitation. •  When it reaches the surface of the Earth, it runs off back

to the river and streams or it enters the ground water supply.

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Section 3-3

The Water Cycle

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Nutrient Cycles

•  The food you eat provides energy and chemicals that keep you alive. All the chemical substances that an organism needs to sustain life are its nutrients.

•  Every living organism needs nutrients to build tissues and carry out essential life functions. Like water, nutrients are passed between organisms and the environment through biogeochemical cycles.

•  There are three nutrient cycles: 1.  The Carbon Cycle 2.  The Nitrogen Cycle 3.  The Phosphorus Cycle

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The Carbon Cycle •  Carbon is a key ingredient of living tissue. It is an important component

of animal skeletons and is found in several kinds of rocks. •  Carbon combined with oxygen forms carbon dioxide which is found in

the atmosphere. •  The four main processes that moves carbon through the biosphere: 1.  Biological processes, such as photosynthesis, respiration, and

decomposition, take up and release carbon and oxygen. 2.  Geochemical processes, such as erosion and volcanic activity, release

carbon dioxide to the atmosphere and ocean. 3.  The burial and decomposition of dead organisms and their conversion

under pressure into fossil fuels, store carbon underground. 4.  Human activities, such as mining, burning of forests and fossil fuels,

release carbon dioxide into the atmosphere.

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CO2 in Atmosphere

CO2 in Ocean

Section 3-3

Figure 3-13 The Carbon Cycle

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The Nitrogen Cycle

•  Many forms of nitrogen occur naturally in the biosphere. •  Nitrogen Gas makes up 78 % of the atmosphere. •  Ammonia, nitrates and nitrites are found in waste products

•  Humans add nitrogen by adding fertilizers to soil. •  Bacteria can convert nitrogen gas into ammonia through a process

called nitrogen fixation. •  Other bacteria change ammonia into nitrates or nitrites which are then

absorbed by producers to make proteins. •  When organisms die, decomposers return nitrogen to the soil as

ammonia. •  Other bacteria convert ammonia into nitrogen gas through

denitrification.

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N2 in Atmosphere

NH3

NO3-

and NO2-

Section 3-3

Figure 3-14 The Nitrogen Cycle

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The Phosphorus Cycle •  Phosphorus is essential to living

organisms because it forms part of important life-sustaining molecules such as DNA and RNA.

•  Unlike carbon, nitrogen and water, phosphorus does not enter into the atmosphere.

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Nutrient Limitations •  Ecologists are interested in the rate in which organic

matter is produced in an ecosystem. This is called primary productivity.

•  One factor that controls the amount of growth in that ecosystem is the amount of available nutrients.

•  When an ecosystem is limited by a single nutrient that is scarce or cycles very slowly, this substance is called a limiting nutrient.

•  Nitrogen is the limiting nutrient in sea water. •  Phosphorus is the limiting nutrient in lake, rivers, and

streams. •  When an aquatic ecosystem receives a large input of a

limiting nutrient, an algal bloom results.

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Video

Click the image to play the video segment.

Cycles in Nature The latest discoveries in preserving the environment Links from the authors on exploring ecology from space Interactive test

For links on energy pyramids, go to www.SciLinks.org and enter the Web Code as follows: cbn-2032. For links on cycles of matter, go to www.SciLinks.org and enter the Web Code as follows: cbn-2033.

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Interest Grabber Answers

1. What living things are found in and around your school? Living things in the school are students, teachers, principal, assistant principals, clerical staff, custodians, lunchroom staff. Students may also include animals in science labs. Living things around the school include grass, trees, shrubs, insects, birds, and so on.

2. What nonliving things are found in your school? The building, furniture, desks, books, papers, and so on

3. Into what large groups are the students in your school divided? 9th, 10th, 11th, 12th grades, or years

4. Into what smaller groups are these large groups divided? Classes

5. Are these groups ever divided into even smaller groups? If so, what are these groups? Students may say that science classes are divided into lab groups; other classes may be divided into groups for projects.

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Interest Grabber Answers

1. Make a list of five foods that you like to eat. Indicate whether the food comes from a plant (producer) or an animal (consumer). Student lists will be individualized. One possible example would be a hamburger, which comes from a cow or steer.

2. Like many birds, chickens eat grains, which are seeds. Where do seeds come from? Seeds come from plants.

3. Meat comes from beef cattle. What do cattle eat? Cattle eat grass or grains.

4. Construct a diagram showing how one of your favorite foods obtains its energy. Include as many levels as you can. Student diagrams will be individualized based on their food choice. Using the hamburger example, the beef in the hamburger comes from cattle. The cattle feed on grass or grain. Grass or grains are plants, which use energy from the sun to make their own food.

Interest Grabber Answers

1. When rain falls on the ground, it either soaks into the soil or runs across the surface of the soil. When rainwater runs across the land, what body of water might collect the rain? Possible answers: a stream, river, pond, or lake

2. From here, where might the water flow? Into a river, and eventually into the ocean

3. After the rain, the sun comes out and the land dries. Where does the water that had been on the land go? It evaporates and becomes a gas in the atmosphere.

4. Construct a diagram that would illustrate all the places a molecule of water might go. Begin with a raindrop and end with a cloud. Student diagrams may include the following: a raindrop —> lawn —> a stream —> river —> large lake —> atmosphere —> cloud.

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