Chapter 53 COMMUNITY ECOLOGY

How species within a community interact affect the species survival and reproduction.

Community: ______________________________________________________________________________________________________________

______________________________________________________________________________________________________________________________

Section 53.1 A community’s interactions include and are linked by:

• competition

• _________________________

• herbivory

• symbiosis (_________________________ , _________________________ , _________________________)

• _________________________

Types of Interactions Among Species in a Community

competition - ____________________________________________________________________________________________________________

______________________________________________________________________________________________________________________________

1.

a. _____________________________________________- When two organisms of the same species are in

competition for the same resource

b. _____________________________________________- When two different species are in competition for the

same resource.

i. Competition can be for resources such as

1. Food

2. _____________________________________________

3. _____________________________________________

4. _____________________________________________

c. Strong competition can lead to competitive exclusion

1. Competitive exclusion principle: ___________________________________________________

____________________________________________________________________________________________

2. A slight reproductive advantage will lead to the elimination of the inferior

species

3. Competitive exclusion does ________________ lead to species diversity

ii. As a result of competition (-/-)

1. A species’ fundamental ________________ may be different from its realized niche

2. Competitive ________________

3. Resource ________________

4. Reduction in________________species

5. Reduction in ________________ species

2. The ecological niche-___________________________________________________________________________________________

______________________________________________________________________________________________________________________

a. The ‘job’ or ‘role’ of an organism.

b. Example: Snake—

i. Snake aerates soil (effect on abiotic environment)

ii. Snake eats mouse (effect on biota)

iii. Snake is food for hawk (effect on biota)

c. The niche concept allows restatement of the __________________________________________principle

d. Two species __________________________________________ coexist in a community if their niches are

__________________________________________

e. However, ecologically similar species can coexist in a community

i. If there are one or more significant difference in their niches

ii. This IS an example of the competitive __________________________________________principle

iii.

1.

3. Resource partitioning: _________________________________________________________________________________________

______________________________________________________________________________________________________________________

1. Resource partitioning enables similar species to _________________________________in

a community

2. Most likely to occur b/w __________________________________________ populations of

species with similar ecological niches

ii.

4. Character displacement:

______________________________________________________________________________________________________________________

______________________________________________________________________________________________________________________

a. There is a tendency for characteristics to be more ______________________________ in sympatric

populations of two species than in ____________________________________ populations of the same two

species

b. Sympatric population: __________________________________________________________________________________

_____________________________________________________________________________________________________________

i. Think S stands for __________________________________________

c. Allopatric population: ___________________________________________________________________________________

_____________________________________________________________________________________________________________

d. ThinkA stands for __________________________________________

i.

5. predation - _______________________________________________________________________________________________________

______________________________________________________________________________________________________________________

a. One individual ________________________________ and one individual is _________________________________

b. Predators have __________________________________________ that allow them to get food suchas:

i. sharp, flesh-eating teeth

ii. camouflage aka __________________________________________

iii. __________________________________________

iv. __________________________________________

v. __________________________________________

c. Prey have __________________________________________that allow them to survive, such as:

i. Camouflage

ii. __________________________________________ (looking like another organism)

iii. producing poisons or irritating chemicals.

d. Types of Animal Defenses against predation

i. __________________________________________- When an animal is camouflaged by its coloring.

ii. __________________________________________- When a poisonous animal is brightly colored as a

warning to other animals.

1. Can be Colors sounds smells

2. Stripes on skunk

3. Red Berries

4. Cuttlefish (Emit ink much like an octopus)

5. Black widow spider

6. Rattlesnake shaking its tail

iii. __________________________________________- When an animal that is

__________________________________________ has evolved to mimic the coloration of a poisonous

animal.

1. Model must be harmful

2. Mimic really has no defense mechanism

3. Predator must be able to learn

4. Model must be easily recognizable

iv. __________________________________________- When two bad tasting species resemble each

other, so that predators will learn to avoid both of them equally.

6. herbivory - _____________________________________________________________________________________________________

a. Some plants protect themselves with

i. chemical toxins

ii. spines

iii. thorns.

7. parasitism - ______________________________________________________________________________________________________

a. One individual _________________ and one individual is _________________

b. The difference between predation and parasitism is that in predation one individual is __________

immediately, while in parasitism the parasite_________________on the host for a long time.

c. Examples: leeches, ticks, fleas, lice, mosquitoes, and tapeworms

8. Disease - __________________________________________________________________________________________________________

______________________________________________________________________________________________________________________

______________________________________________________________________________________________________________________

a. Pathogens, disease-causing agents

b. Are typically bacteria, viruses, or protists

9. mutualism - ______________________________________________________________________________________________________

______________________________________________________________________________________________________________________

a. Example: Ants on acacia tree: __________________________________________________________________________

_____________________________________________________________________________________________________________

_____________________________________________________________________________________________________________

b. Example #2 ______________________________________________________________________________________________

_____________________________________________________________________________________________________________

10. commensalism - _________________________________________________________________________________________________

______________________________________________________________________________________________________________________

a. Example: A buffalo moves through the grass forcing insects to move which then get eaten by

birds.

b. Example #2

53.2 Dominant and keystone species exert strong control on community structure

1. Species Diversity- ___________________________________________________________________________________________

______________________________________________________________________________________________________________________

b. Two component of species diversity

i. Species richness-_________________________________________________________________________________

ii. Relative abundance-- Differences in the abundance of different species within a

community.

iii. Which community has a greater species diversity and why?

_____________________________________________________________________________________________________

2. Trophic structure- _____________________________________________________________________________________________

a. Is a key factor in community dynamics

b. Describes _________________factors

c. Food chain- ________________________________________________________________________________________________

d. Autotrophs—photosynthetic or __________________________________

e. Heterotrophs—Consume other organisms for energy

Practice Questions

o The __________________________________of an organism is the position it occupies in a food chain

o What is the original source of energy for all food chains/webs? _________________

o How much energy is lost from one trophic level to the next? _________________

o How much energy is available from one trophic level to the next? _________________

o Is the sun a trophic level? _________________

o How much energy is lost from the flower to the snake? _________________

o How much energy is available at the mouse? _________________

3. __________________________________-Is a branching food chain with complex trophic interactions

4. Limits on food chain length

a. Each chain in a food web is usually only a few links long. Two hypotheses that explain food chain

length.

i. energetic hypothesis: _________________________________________________________________________________

ii. dynamic stability hypothesis: ________________________________________________________________________

iii. Which hypotheses has the most data supporting it? _________________________________________________

5. Explain how a dominant species can affect an ecosystem.

a. __________________________________Are those species in a community that are most abundant or have

the highest biomass

1. _________________—total dry organic content of an organism

b. Exert powerful control over the occurrence and distribution of other _________________

c. One hypothesis suggests that _________________ species are most competitive in

exploiting_________________ resources

d. Another hypothesis for dominant species successful that they are most successful at avoiding

predators

6. Keystone __________________________________________________________________________________________________________

______________________________________________________________________________________________________________________

a. Example #1:

b. Example #2:

c. If the removal of ONE species reduces the species diversity the species removed is most likely a

__________________________________

7. Ecosystem engineers:

a. __________________________________A species that has a positive effect on the survival and

reproduction of other species in a community and that contributes to community structure.

i. Example 1: __________________________________

ii. Example 2: __________________________________

8. Bottom up and top down controls

a. The bottom-up model of community organization:

b. Proposes a unidirectional influence from lower to higher trophic levels

c. In this case, the presence or absence of abiotic nutrients

d. Determines community structure, including the abundance of primary producers

9. The top-down model of community organization

a. Proposes that control comes from the trophic level above

b. In this case, predators control herbivores, which in turn controls herbivores.

c. Long-term experiment studies have shown that communities can shift periodically from

bottom-up to top-down

Concept 53.3: Disturbance influences species diversity and composition

Stability-- _________________________________________________________________________________________________________________

______________________________________________________________________________________________________________________________

Don’t forget—ecosystems such as a desert or the tundra is an example of a stable community.

Communities are constantly changing after disturbances

1. What is a disturbance?

a. Is an event that _________________a community

b. Removes/adds _________________________________ from/to a community

c. Alters resource availability

d. Frequently related to __________________________________ activity

e. Can create vacated ecological niches that other species can fill

f. Examples

i. Fires—can be significant and/or necessary

10. Hurricanes

11. Floods

12. Human

g. Intermediate disturbance/moderate disturbance-- ___________________________________________________

____________________________________________________________________________________________________________

2. Human disturbance

a. Greatest impact on ___________________________________________________

i. Logging

ii. Clearing for urban development

iii.

iv.

b. __________________________________ species diversity

3. Ecological succession:

a. Ecological succession – ______________________________________________________________________________

_____________________________________________________________________________________________________________

b. Disturbances such as fires, landslides, hurricanes, and floods change the species diversity in

communities.

c. primary succession - _________________________________________________________________________________

____________________________________________________________________________________________________________

i. Such as bare rock, sand dunes, an island formed by volcanic eruption, or a retreating

glacier.

ii. Often occurs very slowly (usually prokaryotes, lichens, and mosses are first to appear).

iii. Some plants are referred to as facilitators.

1. Example: _________________Grow on bare rock and break it down into soil/organic

content as it is acidic

d. secondary succession - _______________________________________________________________________________

____________________________________________________________________________________________________________

i. Such as after a forest fire, strong storm, farming, logging, or mining.

ii. The soil is left intact.

iii. Occurs __________________________________primary succession

iv. ___________________________________________________Early-arriving species

1. May facilitate the appearance of __________________________________ species by making

the environment more __________________________________

2. May inhibit establishment of __________________________________ species

3. May tolerate later species but have no impact on their establishment

Concept 53.4: Biogeographic factors affect community diversity

Island Equilibrium Model

• Two key factors correlated with a community’s species diversity are its

__________________________________and its__________________________________

1. The two key factors in equatorial-polar gradients of species richness are probably evolutionary

history (older) and climate

a. History

i. The greater age of __________________________________environments

ii. May account for the greater __________________________________ richness

b. Climate

i. At equator—lots of __________________________________

1. Longer growing __________________________________

2. Fewer __________________________________due to less seasonal change

3. Species diversity is especially great in the tropics

ii. Poles—__________________________________ diversity

1. _________________ niche here which requires very specialized individuals/species

2. Species richness generally _________________ along an equatorial-polar gradient

3. Species richness increases as you move _________________the equator

4. As latitude _________________, species diversity decreases.

iii. The two main climatic factors correlated with biodiversity

1. Are _________________input and _________________availability

2. Community evapotranspiration is a reflection of

a. Solar radiation

b. Temp

c. Water availability

2. Area Effects

a. The species-area curve quantifies the idea that all other factors being equal, the

_________________ the geographic area of a community, the _________________ the number of

species

b. A species-area curve of North American breeding birds supports this idea

c. Species richness on depends on __________________________________, distance from the

__________________________________, immigration, and extinction.

d. Studies of species richness on the Galápagos Islands support the prediction that species

richness increases with island size

Review—Size of island and distance from mainland affect the number of species.

Concept 53.5: Contrasting views of community structure are the subject of continuing debate

Integrated and Individualistic Hypotheses

1. Two different views on community structure

a. The integrated hypothesis of community structure

i. Describes a community as an assemblage of closely _________________ species, locked

into association by mandatory _________________ interactions

ii. Focuses on how organism interact.

iii. For example, predator/prey relationships

iv. Predicts that the _________________or _________________of particular species depends on the

presence or absence of other species

b. The individualistic hypothesis of community structure

i. Proposes that __________________________________ are loosely organized associations of

independently distributed species with the same___________________________ requirements

ii. Discrete __________________________________ boundaries are important

iii. Strong ____________________influences (water, temp, etc.)

iv. Community structure changes along a gradient

v. Bottom up.

Rivet and Redundancy Models

1. ____________________________________________________________________

a. Suggests that all species in a community are linked together in a tight web of interactions

b. Also states that the loss of even a single species has strong repercussions for the community

2. ____________________________________________________________________

a. Proposes that if a species is lost from a community, other species will fill the gap

REVIEW!

Ecological concepts that promote species diversity

3. Keystone species: A species that is not necessarily abundant in a community yet exerts strong

control on community structure by the nature of its ecological role or niche.

4. Patchy environments: Clumped distribution—determined by resource availability

5. Moderate disturbances: Ensures that no species can stick around too long to dominate—

prevents interspecific competition.

6. Migration: Different species at different times of year.

7. Climate/Seasons: Different species at different times of year.