Community Ecology

Chapter 8

Objectives

• Summarize species types• Evaluate competition and predation• Compare and contrast symbiosis

What is a niche?

• Species’ way of life or functional role in an ecosystem

• Everything that affects its survival and reproduction– Range of tolerance for physical and chemical conditions– Types and amounts of resources it uses– How it interacts with other living and nonliving

components– Role it plays in energy flow and matter cycling

• How is this different from a habitat?

Fundamental vs. Realized

• Full potential range a species’ could theoretically use if no direct competition from other species

• Part of the fundamental niche a species actually uses

• Done to avoid competition for the same resources

Generalist vs. Specialist

• Have broad niche– Live in many places– Eat variety of food– Tolerate wide range of

environmental conditions

• Have narrow niche– Live in one type of

habitat– Only 1-2 types of food– Tolerate narrow range of

environmental conditions

Types of Species

• Native species

• Nonnative, exotic, or alien species

Types of Species

• Indicator

• Keystone

Why Should We Care About Alligators?

• Why are alligators considered a keystone species? How do they affect

• Do you think people should be allowed to kill alligators found on their property? Explain.

What might species compete for?

Intraspecific Competition

What makes a good territory?

Interspecific Competition

Interference Competition Exploitation Competition

Competitive Exclusion Principle

High

Low

Rel

ati

ve

po

pu

lati

on

den

sity

0 2 4 6 8 10 12 14 16 18

Days

Each species grown alone

Parameciumaurelia

Parameciumcaudatum

High

LowR

ela

tiv

e p

op

ula

tio

n d

ensi

ty0 2 4 6 8 10 12 14 16 18

Days

Both species grown together

Parameciumaurelia

Parameciumcaudatum

Reducing or Avoiding Competition

Why are Sharks Important?

Species Interaction

Who Benefits?

Who is Harmed? Examples

Predator-Prey

Parasitism

Mutalism

Commensalism

PredatorsIncrease Chance of Meal

PreyDefend or Avoid Predators

How is predation different from parasitism? How are they similar?

Objectives

• Explain community structure• Describe the theory of island biogeography

Community Structure

Ecotones and Edge Effects

Ants Birds

Latitude

Depth

Pollution

Spe

cie

s di

vers

ity 20

5

00 2,

000

4,000

6,000Depth (meters)

0 2,000 4,000 6,000

Depth (meters)

15

5

0

Coast Deep Sea

Snails Tube worms

Coast Deep Sea

0 2,000 4,000 6,000

Biod

iver

sity

Theory of Island BiogeographyHigh

Low

Ra

te o

f im

mig

ratio

no

r ex

tinct

ion

Equilibrium number

Immigration and extinction rates

Number of species on island

(a)

100

50

25

12.5

6.25

0 2,000 4,000 6,000 8,000 10,000

Distance from New Guinea (kilometers)

Num

ber

of

spec

ies

(per

cent

age

of

sam

ple

stu

died

)

100

1 10 100 1,000 10,000 100,000

Area (square miles)

Num

ber

of

amph

ibia

n an

d re

ptile

spe

cies

10

SABA MONTSERRAT CUBA

Hispaniola

Puerto Rico

Jamaica

Cuba

Montserrat

Saba

Redonda

Objectives

• Compare and contrast primary and secondary succession.

• Describe the factors that affect succession.• Evaluate the three types of stability

How do ecosystems respond to change?

• What happens after a forest fire?• What happens after a volcano?• What happens when climate changes?

Primary Succession

Secondary Succession

Succession and Wildlife

Primary Secondary

Primary or Secondary?

Disturbance and Succession

Intermediate Disturbance Hypothesis

Percentage disturbance

Spe

cies

div

ersi

ty

Succession Predictability

• Old View – predictable sequence leading to a climax community

• New View – ongoing process impacted by chance and biodiversity

Ecological Stability

• Inertia – persistence, resist change

• Constancy – maintain within limits, population

• Resilience – recover

Does diversity = stability?

Ecological Sustainability

• If diversity ≠ stability why conserve?

Precautionary principle

Succession, Disturbance and Stability

Draw a picture showing how disturbance can increase diversity. How is succession involved? How is stability involved?