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Chapter 3 The BiosphereLevels Within Levels

On a sheet of paper, list all of the types of organisms that you have seen in the past week. (plants, humans, insects, etc.) Make some sort of diagram that shows how the organisms on your list interact with one another.

•Do some of the organisms provide energy or nutrients to others?

• What would happen if all of the plants on your diagram died?

Section 3-1

Interest Grabber

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3-1 What is Ecology?

Ecology – the scientific study of interactions among organisms and their surroundings.

Ecologists – scientists who study the environment

Biosphere – the combined portions of the planet in which all of life exists, including land (lithosphere), water (hydrosphere), and air (atmosphere).

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Levels of Organization(From least inclusive to most inclusive)

1) Species – the individual organism.

2) Populations – a group of organisms of one species that interbreed and live in the same place at the same time.

3) Communities – a collection of interacting populations.

4) Ecosystems – made up of the interactions among the populations in a community. This could include their habitat (the place where an organism lives out its life) or its niche (the role and position a species has in its environment)

5) Biome – a group of ecosystems that have the same climate and similar dominant communities.

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Section 3-1

Figure 3-2 Ecological Levels of Organization

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Energy Flow

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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3-2 Energy Flow

Food Chains – a diagram that show the flow of energy from green plants to consumer organisms

Grass rabbit hawk

Food Webs – a diagram that shows the many possible food chains that exist in an ecosystem.

Trophic Levels

The first step in any food chain is always the producer. The second step is always the herbivore. Since the herbivore is the first consumer, it is sometimes referred to as the first order or (primary) consumer. The second consumer is the second order (secondary) consumer. Next is the third order (tertiary) and fourth (quaternary) consumer. Decomposers may be at any step except the first.

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Trophic Levels AHSGE!!!

Fourth order consumers (Quaternary) Heterotrophs

Third order consumers (Tertiary) Heterotrophs

Second order consumers (Secondary) Heterotrophs

First order consumers (Primary) Heterotrophs

Producers Autotrophs Available Energy Decreases

Heterotrophs- rely on other organisms for their food; Herbivores, Carnivores, Omnivores, Detritivores (feed on dead matter)e.g. mites, earthworms, snails. Decomposers (break down organic matter) e.g. bacteria and fungi.

Autotrophs- plants, some algae, and certain bacteria capture energy from the sun and use that energy to make their own food. Autotrophs make food automatically!

Fact: Sunlight is the main energy source for life on earth.

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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?

Section 3-2

Interest Grabber continued

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Food Chain vs. Food Web AHSGE!!!

A food web contains many overlapping food chains so it is much more complex than a

single food chain.

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Section 3-2

Figure 3-8 A Food Web

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Pyramid of NumbersShows the relativenumber of individualorganisms at eachtrophic level.

Biomass PyramidRepresents the amount ofliving organic matter at each trophic level. Typically, thegreatest biomass is at the base of the pyramid.

Energy PyramidShows 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?

Section 3-3

Interest Grabber continued

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3-3 Cycles of Matter

Biogeochemical Cycles – the flow of chemicals between the environment and the organisms

Matter is constantly recycled within and between ecosystems.

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THE WATER CYCLE

Heat evaporates water from oceans, lakes, and streams. Water is then carried into the atmosphere where it condenses and returns to the Earth in the form of precipitation. Plants release water from their leaves through transpiration. This is a continuous cycle.

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Condensation

Seepage

Runoff

Precipitation

TranspirationEvaporation

RootUptake

Section 3-3

The Water Cycle

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THE CARBON CYCLE

The Carbon Cycle is driven by photosynthesis and respiration. In photosynthesis plants take in carbon dioxide and water to produce glucose and oxygen. The plant’s role is to produce an organic carbon compound called glucose. During respiration, organisms use oxygen and glucose to produce carbon dioxide and water. Carbon dioxide is released into the atmosphere by respiration as well as many other activities. This is a continuous cycle that occurs between plants and animals.

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CO2 inAtmosphere

CO2 in Ocean

Section 3-3

Figure 3-13 The Carbon Cycle

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THE NITROGEN CYCLE

Over 78% of the air is nitrogen gas, but in this form it is useless to organisms. Most living organisms use nitrogen only in the form of nitrates and ammonia. The conversion of nitrogen gas to ammonia is called nitrogen fixation. This process is carried out by bacteria located in the roots of legumes (peas and beans). Other bacteria convert ammonia into nitrates and nitrites. Plants then take in the nitrates. Animals eat the plants, and we obtain nitrogen. Other bacteria in the soil convert nitrates back into nitrogen. This process is called denitrification. Then the nitrogen gas is returned to the atmosphere for the cycle to begin again.

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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

All organisms require phosphorus. Plants obtain phosphorus from the soil, and animals obtain phosphorus from plants. When animals and plants die, they return phosphorus to the soil.

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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