Unit 1: What is Biology?Unit 2: EcologyUnit 3: The Life of a CellUnit 4: GeneticsUnit 5: Change Through TimeUnit 6: Viruses, Bacteria, Protists, and FungiUnit 7: PlantsUnit 8: InvertebratesUnit 9: VertebratesUnit 10: The Human Body

Unit 1: What is Biology? Chapter 1: Biology: The Study of Life

Unit 2: EcologyChapter 2: Principles of EcologyChapter 3: Communities and BiomesChapter 4: Population BiologyChapter 5: Biological Diversity and Conservation

Unit 3: The Life of a CellChapter 6: The Chemistry of LifeChapter 7: A View of the CellChapter 8: Cellular Transport and the Cell CycleChapter 9: Energy in a Cell

Unit 4: GeneticsChapter 10: Mendel and MeiosisChapter 11: DNA and GenesChapter 12: Patterns of Heredity and Human GeneticsChapter 13: Genetic Technology

Unit 5: Change Through TimeChapter 14: The History of LifeChapter 15: The Theory of Evolution Chapter 16: Primate EvolutionChapter 17: Organizing Life’s Diversity

Unit 6: Viruses, Bacteria, Protists, and FungiChapter 18: Viruses and BacteriaChapter 19: ProtistsChapter 20: Fungi

Unit 7: PlantsChapter 21: What Is a Plant?Chapter 22: The Diversity of PlantsChapter 23: Plant Structure and FunctionChapter 24: Reproduction in Plants

Unit 8: InvertebratesChapter 25: What Is an Animal?Chapter 26: Sponges, Cnidarians, Flatworms, and

RoundwormsChapter 27: Mollusks and Segmented WormsChapter 28: ArthropodsChapter 29: Echinoderms and Invertebrate

Chordates

Unit 9: VertebratesChapter 30: Fishes and AmphibiansChapter 31: Reptiles and BirdsChapter 32: MammalsChapter 33: Animal Behavior

Unit 10: The Human BodyChapter 34: Protection, Support, and LocomotionChapter 35: The Digestive and Endocrine SystemsChapter 36: The Nervous SystemChapter 37: Respiration, Circulation, and ExcretionChapter 38: Reproduction and DevelopmentChapter 39: Immunity from Disease

EcologyPrinciples of Ecology

Communities and Biomes

Population Biology

Biological Diversity and Conservation

Chapter 2 Principles of Ecology

2.1: Organisms and their Environment

2.1: Section Check

2.2: Nutrition and Energy Flow

2.2: Section Check

Chapter 2 Summary

Chapter 2 Assessment

What You’ll LearnYou will describe ecology and the work of ecologists.

You will identify important aspects of an organism’s environment.

You will trace the flow of energy and nutrients in the living and nonliving worlds.

• Distinguish between the biotic and abiotic factors in the environment.

Section Objectives:

• Compare the different levels of biological organization and living relationships important in ecology.

• Explain the difference between a niche and a habitat.

• What affects the environment also affects you.

• Understanding what affects the environment is important because it is where you live.

Sharing the World

• The study of plants and animals, including where they grow and live, what they eat, or what eats them, is called natural history.

• These data reflect the status or health of the world in which you live.

Studying nature

• The branch of biology that developed from natural history is called ecology.

• Ecology is the study of interactions that take place between organisms and their environment.

What is ecology?

• Scientific research includes using descriptive and quantitative methods.

• Most ecologists use both descriptive and quantitative research.

Ecological research

• They obtain descriptive information by observing organisms.

• They obtain quantitative data by making measurements and carrying out controlled experiments in the field and in the laboratory.

Ecological research

• The biosphere is the portion of Earth that supports living things.

• It extends from high in the atmosphere to the bottom of the oceans.

The Biosphere

• Although it is thin, the biosphere supports a diverse group of organisms in a wide range of climates.

• Living things are affected by both the physical or nonliving environment and by other living things.

The Biosphere

• The nonliving parts of an organism’s environment are the abiotic factors.

• Examples of abiotic factors include air currents, temperature, moisture, light, and soil.

The nonliving environment: Abiotic factors

• Ecology includes the study of features of the environment that are not living because these features are part of an organism’s life.

The nonliving environment: Abiotic factors

• Abiotic factors have obvious effects on living things and often determine which species survive in a particular environment.

The nonliving environment: Abiotic factors• This graph shows how the plant’s glucose

(food) production is affected by temperature.

5

10

15Food Production in Salt Bush

10 20 30 40 50Temperature (°C)

Food

pro

duct

ion

(mg

of g

luco

se/h

r)

The living environment: Biotic factors

• A key consideration of ecology is that living organisms affect other living organisms.

• All the living organisms that inhabit an environment are called biotic factors.

• All organisms depend on others directly or indirectly for food, shelter, reproduction or protection.

Levels of Organization• Ecologists study individual organisms,

interactions among organisms of the same species, interactions among organisms of different species, as well as the effects of abiotic factors on interacting species.

• Ecologists have organized the living world into levels—the organism by itself, populations, communities, and ecosystems.

Organism• An individual living thing that is made of

cells, uses energy, reproduces, responds, grows, and develops.

Interactions within populations• A population is a group of organisms, all of

the same species, which interbreed and live in the same area at the same time.

Interactions within populations• Members of the same population may

compete with each other for food, water, mates, or other resources.

• Competition can occur whether resources are in short supply or not.

Interactions within communities• Just as a population is made up of individuals,

several different populations make up a biological community.

Interactions within communities• A biological community is made up of

interacting populations in a certain area at a certain time.

Interactions within communities

• A change in one population in a community may cause changes in the other populations.

• Some of these changes can be minor, such as when a small increase in the number of individuals of one population causes a small decrease in the size of another population.

Interactions within communities

• Other changes might be more extreme, as when the size of one population grows so large it begins affecting the food supply for another species in the community.

Ecosystem• Populations of plants and animals that

interact with each other in a given area and with the abiotic components of that area.

Biotic and abiotic factors form ecosystems• An ecosystem is made up of interacting

populations in a biological community and the community’s abiotic factors.

• There are two major kinds of ecosystems—terrestrial ecosystems and aquatic ecosystems.

Biotic and abiotic factors form ecosystems

• Terrestial ecosystems are those located on land.

Table 2.1 Examples of EcosystemsTerrestrial Ecosystems

• Forest• Old farm field• Meadow• Yard• Garden plot• Empty lot• Compost heap• Volcano site• Rotting log

Aquatic Ecosystems

Freshwater• Pond• Lake• Stream• EstuarySalt water (marine)• Ocean• Estuary• Aquarium

Other Sites for Ecosystems

Human body• Skin• Intestine• MouthBuildings• Mold in walls, floors, or basement• Ventilation systems•BathroomsFood• Any moldy food• Refrigerator

Biotic and abiotic factors form ecosystems

• Aquatic ecosystems occur in both fresh- and saltwater forms.

Table 2.1 Examples of EcosystemsTerrestrial Ecosystems

• Forest• Old farm field• Meadow• Yard• Garden plot• Empty lot• Compost heap• Volcano site• Rotting log

Aquatic Ecosystems

Freshwater• Pond• Lake• Stream• EstuarySalt water (marine)• Ocean• Estuary• Aquarium

Other Sites for Ecosystems

Human body• Skin• Intestine• MouthBuildings• Mold in walls, floors, or basement• Ventilation systems•BathroomsFood• Any moldy food• Refrigerator

Biotic and abiotic factors form ecosystems• Freshwater ecosystems include ponds, lakes,

and streams.

Biotic and abiotic factors form ecosystems

• Saltwater ecosystems, also called marine ecosystems, make up approximately 70 percent of Earth’s surface.

Organisms in Ecosystems• A habitat

is the place where an organism lives out its life.

Organisms in Ecosystems• Habitats can change, and even disappear.

Habitats can change due to both natural and human causes.

Niche• Although several species may share a

habitat, the food, shelter, and other essential resources of that habitat are often used in different ways.

• A niche is the role or position a species has in its environment—how it meets its specific needs for food and shelter, how and where it survives, and where it reproduces in its environment.

Niche

• A species’ niche, therefore, includes all its interactions with the biotic and abiotic parts of its habitat.

• It is thought that two species can’t exist for long in the same community if their niches are the same.

Symbiosis

• The relationship in which there is a close and permanent association between organisms of different species is called symbiosis.

• Simbiosis means living together. Three kinds of symbiosis are recognized: mutualism, commensalism, and parasitism.

Mutualism• A symbiotic

relationship in which both species benefit is called mutualism.

Commensalism• Commensalism

is a symbiotic relationship in which one species benefits and the other species is neither harmed nor benefited.

Parasitism• Some interactions are harmful to one species,

yet beneficial to another.

• A symbiotic relationship in which a member of one species derives benefit at the expense of another species (the host) is called parasitism.

Parasitism• Parasites have evolved in such a way that

they harm, but usually do not kill the host species.

Parasitism• A predator is a type of consumer. Predators

seek out and eat other organisms.

Parasitism• Predation is found in all ecosystems and

includes organisms that eat plants and animals.

• The animals that predators eat are called prey.

Question 1The study of interactions that take place between organisms and their environment is __________.

D. biologyC. ecologyB. symbiosisA. abiosis

The answer is C. Ecology is a branch of biology that developed from natural history.

Question 2Which of the following is found in the biosphere?

D. constellation Orion

C. the Sun

B. maria

A. ozone layer

The answer is A. The biosphere is the portion of Earth that supports living things and extends high into Earth's atmosphere. Maria are dark-colored regions on the moon.

Question 3Which of the following is a biotic factor?

D. light

C. earthworm

B. soil

A. moisture

The answer is C. Biotic factors are all the living organisms that inhabit an environment.

Question 4A(n) __________ is a group of organisms, all of the same species, which interbreed and live in the same place at the same time.

D. habitat

C. ecosystem

B. population

A. biological community

The answer is B. Communities and ecosystems are comprised of more than one species. Habitat refers to the place an organism lives.

Section Objectives

• Trace the path of energy and matter in an ecosystem.

• Compare how organisms satisfy their nutritional needs.

• Analyze how matter is cycled in the abiotic and biotic parts of the biosphere.

How Organisms Obtain Energy

• One of the most important characteristics of a species’ niche is how it obtains energy.

• Ecologists trace the flow of energy through communities to discover nutritional relationships between organisms.

The producers: Autotrophs• The ultimate source of the energy for life

is the sun.• Plants use the

sun’s energy to manufacture food in a process called photosynthesis.

The producers: Autotrophs

• Other organisms in the biosphere depend on autotrophs for nutrients and energy. These dependent organisms are called consumers.

• An organism that uses light energy or energy stored in chemical compounds to make energy-rich compounds is a producer, or autotroph.

The consumers: Heterotrophs

• Heterotrophs include organisms that feed only on autotrophs, organisms that feed only on other heterotrophs, and organisms that feed on both autotrophs and heterotrophs.

• An organism that cannot make its own food and feeds on other organisms is called a heterotroph.

The consumers: Heterotrophs

• A heterotroph that feeds only on plants is an herbivore.

• Heterotrophs display a variety of feeding relationships.

The consumers: Heterotrophs• Some

heterotrophs eat other heterotrophs. Animals such as lions that kill and eat only other animals are carnivores.

The consumers: Heterotrophs• Scavengers eat animals that have already died.

The consumers: Heterotrophs• Some organisms, such as bacteria and fungi,

are decomposers.

The consumers: Heterotrophs• Decomposers break down the complex

compounds of dead and decaying plants and animals into simpler molecules that can be more easily absorbed.

Flow of Matter and Energy in Ecosystems

Autotrophs

First-order heterotrophs

Third-order heterotrophs Second-order

heterotrophs

Decomposers

Food chains: Pathways for matter and energy

• In a food chain, nutrients and energy move from autotrophs to heterotrophs and, eventually, to decomposers.

• A food chain is a simple model that scientists use to show how matter and energy move through an ecosystem.

Food chains: Pathways for matter and energy• A food chain is drawn using arrows to

indicate the direction in which energy is transferred from one organism to the next.

berries → mice → black bear

Food chains: Pathways for matter and energy• Most food chains consist of two, three, or

four transfers.• The amount of energy remaining in the final

transfer is only a portion of what was available at the first transfer.

• A portion of the energy is given off as heat at each transfer.

Trophic levels represent links in the chain• Each organism in a food chain represents a

feeding step, or trophic level, in the passage of energy and materials.

• A first order heterotroph is an organism that feeds on plants, such as a grasshopper.

Trophic levels represent links in the chain• A second order heterotroph is an organism

that feeds on a first order heterotroph.

• A food chain represents only one possible route for the transfer of matter and energy through an ecosystem.

Food webs• Ecologists interested in energy flow in an

ecosystem may set up experiments with as many organisms in the community as they can.

• The model they create, called a food web, shows all the possible feeding relationships at each trophic level in a community.

Energy and trophic levels: Ecological pyramids• An ecological pyramid can show how energy

flows through an ecosystem.

• The base of the ecological pyramid represents the autotrophs, or first trophic level. Higher trophic levels are layered on top of one another.

Energy and trophic levels: Ecological pyramids• The pyramid of

energy illustrates that the amount of available energy decreases at each succeeding trophic level.

Pyramid of Energy

Heat

Heat

Heat

Heat

0.1% Consumers

1% Consumers

10% Consumers

100% Producers

Energy and trophic levels: Ecological pyramids• The total energy transfer from one trophic

level to the next is only about ten percent because organisms fail to capture and eat all the food energy available at the trophic level below them.

Energy and trophic levels: Ecological pyramids• Some of the energy transferred at each

successive trophic level enters the environment as heat, but the total amount of energy remains the same.

Energy and trophic levels: Ecological pyramids

• A pyramid of numbers shows that population sizes decrease at each higher trophic level.

Pyramid of NumbersFox (1)

Birds (25)

Grasshoppers (250)

Grasses (3000)

Energy and trophic levels: Ecological pyramids• Biomass is the total

weight of living matter at each trophic level. A pyramid of biomass represents the total weight of living material available at each trophic level.

Pyramid of Biomass

1 kilogram of human tissue

10 kilograms of beef

100 kilograms of grain

Cycles in Nature

• Matter, in the form of nutrients, moves through, or is part of, all organisms at each trophic level.

• But matter is cycled and is not replenished like the energy from sunlight. There is a finite amount of matter.

The carbon cycle• From proteins to sugars, carbon is the

building block of the molecules of life.

• Linked carbon atoms form the frame for molecules produced by plants and other living things.

• Organisms use these carbon molecules for growth and energy.

The nitrogen cycleNitrogen in the atmosphere

Nitrogen-fixing bacteria in the

nodules on roots of leguminous plants fix atmospheric nitrogen.

Nitrogen-fixing soil bacteria

Some excess nitrogen evaporates from soil.

Nitrogen compounds released into

soils and acted upon by soil

bacteria

Released to the atmosphere

Assimilated by plants

Urine from animals

Dead plant matter

Decomposing organisms

Decomposers—bacteria and fungi—break down tissues and wastes and nitrogen-

containing compounds are released.

Converted to other nitrogen compounds

by soil bacteria

The phosphorus cycle• In the phosphorus cycle, phosphorus moves

between the living and nonliving parts of the environment.

Which of the following is a producer? Question 1

D. herbivore

C. decomposer

B. heterotroph

A. autotrophNucleusChloroplast

Mitochondrion

Eyespot

FlagellumPellicle

Contractile vacuole

The answer is A. Organisms that make energy-rich compounds are producers, or autotrophs.

NucleusChloroplast

Mitochondrion

Eyespot

FlagellumPellicle

Contractile vacuole

In a food chain, nutrients and energy move from __________ to __________.

Question 2

D. decomposers, autotrophs

C. heterotrophs, autotrophs

B. autotrophs, heterotrophs

A. autotrophs, autotrophs

The answer is B. The first level in all food chains is made up of producers.

berries → mice → black bear

A model of all the possible feeding relationships at each trophic level in a community is a(n) __________.

Question 3

D. food web

C. food matrix

B. food chain

A. food pathway

Chihuahuan raven Honey mesquite (pods eaten by beetles)

Pronghorn antelope

Gambel quail

JackrabbitDesert tortoise

Prickly pear cactus

Long-tail weasel

Coyote (top carnivore)

Roadrunner

Kangaroo rat (seed eater)

antsTexas horned

lizard

Red spotted toad Mexican

whiptail lizard

Mojave rattlesnake

The answer is D. A food web is a more realistic model than a food chain, because most organisms depend on more than one other species for food.

• Natural history, the observation of how organisms live out their lives in nature, led to the development of the science of ecology—the study of the interactions of organisms with one another and with their environments.

Organisms and Their Environment

Organisms and Their Environment• Ecologists classify and study the biological

levels of organization from the individual to ecosystem. Ecologists study the abiotic and biotic factors that are a part of an organism’s habitat. They investigate the strategies an organism is adapted with to exist in its niche.

• Autotrophs, such as plants, make nutrients that can be used by the plants and by heterotrophs. Heterotrophs include herbivores, carnivores, omnivores, and decomposers.

Nutrition and Energy Flow

• Food chains are simple models that show how energy and materials move from autotrophs to heterotrophs and eventually to decomposers.

• Food webs represent many interconnected food chains and illustrate pathways in which energy and materials are transferred within an ecosystem. Energy is transferred through food webs. The materials of life, such as carbon and nitrogen, are used and reused as they cycle through the ecosystem.

Nutrition and Energy Flow

Question 1Which of the following is a biological community?

D. the factors interacting in an aquatic ecosystem

C. the abiotic factors in the environment

B. the tadpoles living in a pond

A. the organisms living in your backyard today

The answer is A. A biological community consists of all the populations of different species that live in the same place at the same time and does not include abiotic factors. Changes in one of these populations may cause changes in the other populations of the community.

Question 2A(n) __________ is the place where an organism lives out its life.

D. community

C. habitat

B. niche

A. environment

The answer is C. A species' habitat is the place where it lives and its niche is the role it plays in its environment, including interactions with abiotic factors.

Question 3Compare commensalism and parasitism.

Haustorium Host cell

Fungal hypha

Both commensalism and parasitism are examples of symbiosis, in which organisms of different species live in close association, benefiting one species. In parasitism, one species derives benefit at the expense of the other, but in a commensal relationship the second species is not harmed.

Question 4Which of the following models best illustrates heat released at each trophic level of an ecosystem?

D. pyramid of biomass

C. pyramid of energy

B. food web

A. food chain

Pyramid of Energy

Heat

Heat

Heat

Heat

0.1% Consumers

1% Consumers

10% Consumers

100% Producers

The answer is C. The pyramid of energy shows energy available. Organisms at each trophic level use some energy in food for metabolism and some is given off as heat. The total amount of energy remains the same in accordance with the law of conservation of energy.

Question 5Compare the amount of energy available in the biosphere to the amount of matter here.

Both energy and matter are conserved: they may be transformed, but are not destroyed. However, sunlight is the primary source of all the energy utilized and transferred in the biosphere. It is always being replenished by the sun. In contrast, there is a finite amount of matter in the biosphere, which is cycled and not replenished.

Question 6Which of the following does not cycle into the atmosphere?

D. water

C. carbon

B. nitrogen

A. phosphorus

The answer is A. Phosphorus moves between the living and nonliving parts of the environment, but does not enter the atmosphere as a gas.

Rain washes phosphates from the land.

Phosphate weathers from rock.

Animal wastes

Plant wastes

Soil decomposers act on plant and animal wastes.

Short-term Cycle Long-term Cycle

Phosphates released into soil,.

Phosphates become available for plants

again.

Phosphates leach into streams from soil.

Decaying materials containing phosphates settle out into streams and oceans.

Geologic process of uplifting occurs over millions of years.

Phosphate enters streams and oceans from weathering rocks, runoff, and leaching, from soil.

New rock forms from sedimentation. Phosphate becomes locked in rocks.

Question 7Which type of organism consumes both plant and animal products?

D. omnivore

C. predator

B. carnivore

A. herbivore

The answer is D.Humans are omnivores and eat a variety of foods that include both plant and animal materials. The figure shows recommended food servings for good health.

Question 8Which of the following relationships is an example of mutualism?

B. orchids aided by growing on large plants neither harming nor benefiting the larger plants

A. Ants feeding on nectar of acacia trees while protecting the trees from other animals.

Question 8Which of the following relationships is an example of mutualism?

D. lions preying on zebras

C. ticks obtaining nutrients from a host animal

The answer is A. Ants and acacia trees both benefit from living in close association.

Question 9Compare a niche to a population.

AnswerA population is a group of organisms of the same species that live in the same place at the same time. A niche is the role a species has in its environment, and includes all its interactions with biotic and abiotic parts of its habitat.

Question 10How does water on Earth's surface get back into the atmosphere?

Precipitation

EvaporationRunoff

Groundwater

TranspirationEvaporation

Condensation

Oceans

The processes of evaporation of water in lakes and oceans and transpiration by plants both put water vapor into the air.

Precipitation

EvaporationRunoff

Groundwater

TranspirationEvaporation

Condensation

Oceans

Photo Credits

• Corbis• Digital Stock• Harris Biological Supplies, LTD• NOAA• PhotoDisc• Alton Biggs

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