chapter 12 lesson 3 populations and communities · producers live near deep-sea vents. they use...

Reading Essentials Populations and Communities 255

CHAPTER 12

LESSON 3C

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Communities

Populations and Communities

Communities, Habitats, and NichesYou learned that a community is made up of all the species

that live in the same ecosystem at the same time. The place within an ecosystem where an organism lives is its habitat. A habitat provides all the resources an organism needs, including food and shelter. A habitat also has the right temperature, water, and other conditions the organism needs to survive.

Many species can live in the same habitat at the same time. This is possible because each species uses the habitat in a different way. A niche (NICH) is what a species does in its habitat to survive. For example, butterflies and ants can live in the same forest. The butterflies feed on flower nectar. The ants eat insects or plants. These species have different niches in the same environment.

Food EnergyAll living things use energy and carry out life processes such

as growth and reproduction. Organisms also need a constant supply of energy, in the form of food, to stay alive. How an organism gets energy is an important part of its niche.

What do you think? What do you think? Read the two statementsbelow and decide whether you agree or disagree with them. Place an A in the Before column if you agree with the statement or a D if you disagree. After you’ve read this lesson, reread the statements to see if you have changed your mind.

Before Statement After

No more than two species can live in the same habitat.

A cow is a producer because it produces food for other organisms.

Essential Question• How do populations in a

community interact?

ExplainScienceJournal

1. Think of an animal inyour environment and describe the niche they live in.

Word Originhabitat from Latin habitus, means “to live, dwell”

256 Populations and Communities Reading Essentials

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ProducersProducers are organisms that get energy from the

environment, such as sunlight, and make their own food. For example, most plants are producers. They get their energy from sunlight. They use the process of photosynthesis (foh toh SIHN thuh sus) and make sugar molecules to use as food. Some producers live near deep-sea vents. They use hydrogen sulfide and carbon dioxide and make sugar molecules.

ConsumersConsumers are organisms that get energy by eating other

organisms. Consumers are classified by the type of organisms they eat. • Herbivores eat producers. Herbivores include butterflies,

aphids, snails, mice, rabbits, fruit-eating bats, gorillas, andcows.

• Omnivores eat producers and consumers. Omnivores includecorals, crickets, ants, bears, robins, raccoons, and humans.

• Carnivores eat herbivores, omnivores, and other carnivores.They include scorpions, octopuses, sharks, tuna, frogs, insecteating bats, moles, and owls.

• Detritivores (duh TRI tuh vorz) consume the bodies of deadorganisms and wastes produced by living organisms. Theyinclude termites, wood lice, and earthworms. Scavengers aredetritivores that eat the bodies of animals killed by carnivoresor omnivores. Examples include hyenas, jackals, and vultures.Decomposers are microscopic detritivores. They cause thedecay of dead organisms or wastes produced by livingorganisms. Most decomposers are fungi and bacteria.

The Flow of EnergyProducers use energy from the environment and make their

own food. This is the first step in the flow of energy through an ecosystem. Most producers use photosynthesis. They convert the energy from sunlight into chemical energy stored in food. Others use chemosynthesis. Once energy from the environment is converted into food energy, it can be transferred to other organisms.

In an ecosystem, food energy is transferred from one organism to another. Food chains and food webs are models. Both of these models describe how energy is transferred through an ecosystem.

2. Imagine that you are anunderwater explorer. You just discovered a microscopic organism deep under the ocean surface where sunlight cannot reach and no food is available. Explain how this organism obtains energy.

NGSSS Check

Science Use v. Common UseconsumerScience Use an organism that cannot make its own food

Common Use a person who uses economic goods

3. Describe the diet of alocal herbivore in your community.

Describe


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Food ChainsA food chain is a simple model that shows how energy moves

from a producer to one or more consumers. Every food chain begins with a producer because producers are the source of all food energy in an ecosystem.

Food WebsMost ecosystems contain many food chains. A food web is a

model of energy transfer that can show how the food chains in a community are interconnected. A food web for a rain-forest community is shown below.

Energy PyramidsMost food chains have at least three links. Most have no

more than five. Why? Think about a blackberry plant. It changes light energy from the Sun to chemical energy. The energy is stored in the plant’s tissues. The plant uses some of that energy to carry out processes, such as growing blackberries. Some of the stored energy is lost as heat.

4. Identify a food web inyour community. List the producers, consumers, and decomposers.

NGSSS Check

Sun

Beetle

Fungus

Butterfly

Ants

Leaves

Flowers

HarpyeagleSloth

Scarlet macaw

Squirrelmonkey

Deadfruit


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When a robin eats blackberries, it gets only part of the energy stored in the plant. The robin uses some of the energy for its own life processes. Again, some of the energy is lost as heat. A falcon that eats the robin gets even less energy for its life processes.

As shown below, an energy pyramid is a model that shows the amount of energy in each link of a food chain. The loss of energy at each level helps explain why there are always more producers than carnivores in a community.

Relationships in CommunitiesThe populations that make up a community interact with

each other in many ways. Some species have feeding relationships. They either eat or are eaten by another species. Some species interact with another species to get the food or shelter they need.

Predator-Prey RelationshipsHungry squirrel monkeys fight over a piece of fruit. They do

not notice the harpy eagle flying above them. Suddenly, the harpy eagle swoops down and grabs one of the monkeys. The eagles and the monkeys have a predator-prey relationship. The eagle, like other predators, hunts other animals for food. The hunted animals, such as the monkey, are called prey.

5. Observe the pyramidand imagine you are a Florida panther looking for its next meal. Choose whether the robin or the hawk will give you more energy and explain your choice.

Explain

Review Vocabularypredatoran organism that survives by hunting another


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Predators help keep prey populations from growing too large. As you already learned, predators are one way that a prey population is kept from reaching the carrying capacity of the ecosystem. Predators often catch weak or injured members of a prey population. When the weak members are removed, more resources become available for the remaining members. This keeps the prey population healthy.

Cooperative RelationshipsThe members of some populations work together in

cooperative relationships for their survival. For example, leaf-cutter ants cooperate with each other and grow food. They work together to cut apart leaves and carry them to their underground nest. The ants do not eat the leaves. Instead, they eat the fungus that grows on the leaves. Squirrel monkeys live in groups. They cooperate with each other as they hunt for food and watch for danger.

Symbiotic RelationshipsSome species have such close relationships that they are

almost always found living together. A close, long-term relationship between two species that usually involves an exchange of food or energy is called symbiosis (sihm bee OH sus). There are three types of symbiosis. They are mutualism, commensalism, and parasitism.

Commensalism A symbiotic relationship that benefits one species but does not harm or benefit the other is commensalism. Plants called epiphytes (EH puh fites) grow on the trunks of trees and other objects. The roots of an epiphyte anchor it to the object. The plant absorbs nutrients from the air. The epiphytes benefit by getting living space and sunlight. The plants do not help or harm the tree. The trees are neither helped nor harmed by the plants. The epiphytes and trees have a commensal relationship.

Mutualism A symbiotic relationship in which both partners benefit is called mutualism. Boxer crabs and sea anemones have a mutualistic partnership. Boxer crabs and sea anemones live in tropical coral reef communities. The crabs carry sea anemones in their claws. The sea anemones have stinging cells that help the crabs fight off predators. The sea anemones eat leftovers from the crabs’ meals. Both partners benefit from the relationship.

6. Choose a predator fromyour local ecosystem. Explain how it obtains its energy. Then, describe its role in the food web.

NGSSS Check

8. Describe therelationship between the spider, a predator, and its prey, a butterfly.

NGSSS Check

7. Define Cooperativerelationships occur between (enter the correct answer in the space below)

a. members of differentspecies

b. members of the samespecies

c. members of any speciesthat live together


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Parasitism A symbiotic relationship that benefits one species and harms the other is parasitism. The species that benefits is the parasite. The species that is harmed is the host. Types of parasites and hosts are shown in the table below.

Heartworms, tapeworms, fleas, and lice are parasites. They feed on a host organism, such as a human or a dog. The parasite benefits by getting food. The host is harmed by losing blood. The host is usually not killed, but it can be weakened. For example, heartworms in a dog can cause the dog’s heart to work harder. The heart can fail after time, killing the host.

The fungi that cause ringworm and toenail fungus are other common parasites. The fungi feed on a protein in skin and nails.

The larvae of the hunting wasp are another example of parasites. The female wasp, stings a spider so it cannot move. Then she lays eggs in its body. When the eggs hatch, the wasp larvae eat the spider’s body.

Another example of parasitism is a plant called Cuscuta, or dodder. The dodder is a parasitic climbing vine. It is found in tropical and subtropical areas, like Florida. The vine wraps itself around a host plant. It inserts itself into the plant’s vascular tissue. Then the dodder’s original roots die. The vine lives off of the host’s nutrients.

9. Do you think thatCuscuta, or dodder, carries out photosynthesis to make food? Explain why or why not.

Explain

Parasitism

Parasite Host Result

heartworm dog causes a dog’s heart to work harderand eventually fail

ringworm, toenail fungus human fungi feed on a protein in skin andnails

hunting wasp spider wasps hatch in the spider and eat its body

Cuscuta, or dodder plant dodder inserts itself into plant’s vascular tissue, and lives off host’s nutrients

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Mini Glossary

END OF LESSON

Reread the statements at the beginning of the lesson. Fill in the After column with an A if you agree with the statement or a D if you disagree. Did you change your mind?

What do you think

Reread the statements at the beginning of the lesson. Fill in the After column with an A if you agree with the statement or a D if you disagree. Did you change your mind?

What do you think

1. Review the terms and their definitions in the Mini Glossary. Use at least one term from the MiniGlossary in a sentence to explain why many species can live in the same habitat.

2. Identify each type of relationship described in the table. Write the name of the relationship next toits description.

Symbiosis

Partner A Partner B Type of Relationship

Benefits is harmed a.

Benefits benefits b.

Benefits does not benefit and is not harmed c.

3. Describe some differences between producers and consumers.

commensalism: a symbiotic relationship that benefits one species but does not harm or benefit the other

consumer: an organism that gets energy by eating other organisms

detritivores (duh TRI tuh vorz): organisms that consume the bodies of dead organisms and wastes produced by living organisms

food web: a model of energy transfer that can show how the food chains in a community are interconnected

habitat: the place within an ecosystem where an organism lives

mutualism: a symbiotic relationship in which both partners benefit

niche (NICH): what a species does in its habitat to survive

parasitism: a symbiotic relationship that benefits one species and harms the other

producer: an organism that gets energy from the environment, such as sunlight, and makes its own food

symbiosis (sihm bee OH sus): a close, long-term relationship between two species that usually involves an exchange of food or energy

chapter 12 lesson 3 populations and communities · producers live near deep-sea vents. they use...

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