First, let’s review Ch. 19.2 (changing populations)

Which term refers to a species that is at risk,

but not yet endangered?

A. B. C. D.

0 000

A. an extinct species

B. a threatened

species

C. an endangered

species

D. a migrating

species

45

What happens to a population if the birthrate of a species is higher than the death rate?

A. B. C. D.

0 000

A. It increases

B. It decreases

C. It remains the

same

D. It disappears

45

Which of these is the only species capable of developing ways to increase the carrying capacity of an environment?

A. B. C. D.

0 000

A. ducks

B. zebras

C. Monarch

butterflies

D. humans

45

Key deer are found on the islands of the Florida Keys

and feed on the native trees. Which is most likely to

happen to populations of key deer, if the forests are

cleared where they live?

A. They would increase in population.

B. They would decrease because of a loss of habitat.

C. They would migrate off the island onto the mainland.

D. They would become a new species because they would adapt to the new habitat.

They would

incr

ease in

...

They would

decr

ease b

e...

They would

mig

rate

off

t..

They would

beco

me a

n..

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45

1. What defines a community?

2. How do organisms in a community interact with each other?

Focus Questions

19.3: Communities

1. What defines a community?

How is a community

different from a

population & an

ecosystem?

Remember the 5 levels of ecosystem organization?

Organism

Population

Community

Ecosystem

Biosphere

• A community is made up of all the species that live in the same ecosystem at the same time.

• Habitat – the place within an ecosystem where an organism lives

• A Habitat provides all the resources an organism needs (food, water, shelter)

• A habitat has the right temperature, water, and other conditions the organism needs to survive.

1. What defines a community?

• An organism’s niche is an organism’s special role in its community (what makes it important).

• Different species have different niches in the same environment.

• Examples:

• Butterflies feed on nectar

• Sloths eat leaves

• Ants eat insects or plants

• Decomposers break down leaf litter

1. What defines a community?

• All living things use energy to carry out life processes such as growth and reproduction.

• How an organism obtains energy is an important part of its niche.

• Almost all the energy available to life on Earth originally came from the sun.

1. What defines a community?

Remember from Ch. 18:

• How does a producer get energy?

• How does a consumer get energy?

• How does a detritivore get energy?

• How does an herbivore get energy?

• How does a carnivore get energy?

• How does an omnivore get energy?

1. What defines a community?

A food web shows many food chains within a community and how they overlap.

• The populations that make up a community interact with each other in a variety of ways.

• Some species have feeding relationships, meaning they either eat or are eaten by another species.

2. How do organism interact with each other?

Predator/Prey relationships:

• Predators hunt the prey for food

• Predators help prevent prey populations from growing too large for the carrying capacity of the ecosystem.

• Examples:

• Harpy eagle & squirrel monkeys

• Sand lizards & insects

2. How do organism interact with each other?

Cooperative relationships:

2. How do organism interact with each other?

Symbiotic relationships:

• A close, long-term relationship between 2 species that usually involves an exchange of food or energy

2. How do organism interact with each other?

• Mutualism: (+/+)

• 2 different species – Both partners benefit

• Examples:

• Boxer crabs (gives leftover food) & sea anemones (helps fight off predators with sting)

• Watchman Goby & pistol shrimp, Shark & Remora fish

2. How do organism interact with each other?

• Commensalism: (+/0)

• 1 partner benefits, the other isn’t benefited or harmed

• Examples:

• Epiphytes living on trees, skin mites, cattle egrets

2. How do organism interact with each other?

• Parasitism: (+/-)

• 1 partner benefits (parasite), the other is harmed (host)

• Ex: heartworms, tapeworms, fleas, lice

• Ex: hunting wasp laying eggs into the spider so they will have food when they hatch

2. How do organism interact with each other?

What general term do scientists use to describe the close relationship between two or more organisms of different species that live in direct contact?

A. B. C. D.

0 000

A. Mutualism

B. Commensalism

C. Parasitism

D. Symbiosis

45

In parasitism, which organism benefits?

A. B. C. D.

0 000

A. Host

B. Partner

C. Parasite

D. Predator

45

Hookworms live inside the intestines of dogs. As the dog

eats, the hookworms consume partially digested food. As

a result of this nutrient diversion, the dog can become

malnourished and weakened. Which best describes the

relationship between the hookworms and the dog?

A. a parasitic relationship

B. a mutualistic relationship

C. a predator-prey relationship

D. a producer-consumer relationship

a parasit

ic re

lationsh

ip

a mutu

alistic

relatio

nship

a predato

r-pre

y relatio

...

a produce

r-consu

mer r

el...

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45

Orchids live on the branches of trees where they

have better access to sunlight and space. The

tree that they live on does not benefit from the

orchids, but they are also not harmed. Which

relationship is this?

A. Cooperative

B. Parasitism

C. Mutualism

D. Commensalism

E. Predator/prey

Cooperativ

e

Parasit

ism

Mutu

alism

Comm

ensalis

m

Predato

r/pre

y

0 0 000

45

Which term refers to everything a species does in its habitat to survive?

A. B. C. D.

0 000

A. Job

B. Niche

C. Habitat

D. Role

45

http://animalsymbiosis.weebly.com/index.html

• Each organism in a community has its own habitat and niche within the ecosystem.

• Within a community, each organism must obtain energy for life processes. Some organisms are producers and some are consumers.

• Some organisms have cooperative relationships and some have symbiotic relationships.

Carol & Don Spencer/Visual Unlimited/Getty Images

A scientist observes that both birds and

snakes in the same ecosystem depend on the

same mouse species as a food source. The

relationship between the birds and the snakes

is an example of

A. predation.

B. mutualism.

C. competition.

D. commensalism.

predatio

n.

mutu

alism

.

com

petitio

n.

com

mensa

lism

.

0 000

45

As the hawk population increases in an

ecosystem, the deer mouse population will

most likely decrease as a result of

A. decrease in food source.

B. increase in disease.

C. increase in predators.

D. decrease in habitat.

decrease

in fo

od sourc

e.

incr

ease in

dise

ase.

incr

ease in

pre

dators

.

decrease

in h

abitat.

0 000

45

How are animals that prey on other

animals classified?

A. herbivores

B. carnivores

C. autotrophs

D. decomposers

herbivo

res

carn

ivore

s

autotro

phs

decom

posers

0 000

45

If a fox and an eagle eat some of the same

organisms in an ecosystem, the relationship

between the fox and the eagle could be

classified as

A. competition.

B. mutualism.

C. predation.

D. parasitism.

com

petitio

n.

mutu

alism

.

predatio

n.

parasit

ism.

0 000

45

Lions tend to prey on primary consumers like zebras

and gazelles. If there were a sudden decline in a

population of lions, which ecological imbalance would

most likely occur in the habitat?

A. overgrazing

B. eutrophication

C. invasion by non-native species

D. overproduction of greenhouse gases ove

rgra

zing

eutrophica

tion

inva

sion b

y non-n

ative s.

..

overp

roduct

ion o

f gre

e...

0 000

45

• A population is all the organisms of the same species that live in the same area at the same time.

• Population sizes vary due to limiting factors such as environmental factors and available resources.

• Population size usually does not exceed the carrying capacity of the ecosystem.

Lesson 1: Populations

Lesson 2: Changing Populations

• Populations of living things can increase, decrease, or move.

• Populations can decrease until they are threatened, endangered, or extinct.

• Human population size is affected by the same three factors as other populations—birthrate, death rate, and environment.

Tom Brakefield/Getty Images

• A community is all the populations of different species that live together in the same area at the same time.

• The place within an ecosystem where an organism lives is its habitat and what an organism does in its habitat to survive is its niche.

• Three types of relationships within a community are predator-prey, cooperative, and symbiotic.

Lesson 3: Communities

Carol & Don Spencer/Visual Unlimited/Getty Images