Chapter 54

Question 1

Biological Community

Answer 1

An assemblage of populations of various species living close enough for potential interaction. For example, the carrier crab carries a sea urchin on its back for protection against predators.

Question 2

Ecologists call relationships between (different) species in a community _.

Answer 2

Interspecific interactions

Question 3

Examples of interspecific interactions are:

Answer 3

• Competition
• Predation
• Herbivory
• Symbiosis (parasitism, mutualism, and commensalism)

Question 4

Interspecific interactions can affect the _ of each species, and the effects can be summarized as positive (+), negative (-), or no effect (0).

Answer 4

Survival and reproduction

Question 5

Interspecific Competition

Answer 5

Occurs when species compete for a resource in short supply; -/- interaction

Question 6

Strong competition can lead to _, local elimination of a competing species (weaker of two species gets excluded).

Answer 6

Competitive exclusion

Question 7

The competitive exclusion principle states that…

Answer 7

…two species competing for the same limiting resources cannot coexist in the same place.

Question 8

Ecological Niche

Answer 8

The sum of a species’ use of biotic and abiotic resources

Question 9

An ecological niche can also be thought of as an organism’s _.

Answer 9

Ecological role

Question 10

Ecologically similar species can coexist in a community if there are one or more significant _ in their niches.

Answer 10

Differences

Question 11

Resource Partitioning

Answer 11

Differentiation of ecological niches, enabling similar species to coexist in a community

Question 12

Fundamental Niche

Answer 12

The niche potentially occupied by a species (could theoretically live there)

Question 13

Realized Niche

Answer 13

The niche actually occupied by a species

Question 14

As a result of _, a species’ fundamental niche may differ from its realized niche. For example, the presence of one barnacle species limits the realized niche of another species.

Answer 14

Competition

Question 15

G.F. Gause’s classic experiment on _ using three Paramecium species shows this principle in action.

Answer 15

Competitive exclusion

Question 16

Sympatric Species

Answer 16

Live in the same geographic region

Question 17

Allopatric Species

Answer 17

Live in different geographic regions

Question 18

Character Displacement

Answer 18

A tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species

Question 19

An example of character displacement is…

Answer 19

…variation in beak size between populations of two species of Galapagos finches.

Question 20

Predation

Answer 20

An interaction in which one species, the predator, kills and eats the other, the prey; +/- interaction

Question 21

Some feeding adaptations of predators are:

Answer 21

• Claws
• Fangs
• Poison

Question 22

Prey display various defensive adaptations. Behavioral defenses include:

Answer 22

• Hiding
• Fleeing
• Forming herds or schools
• Self-defense
• Alarm calls

Question 23

_ and _ defenses protect species such as porcupines and skunks, respectively.

Answer 23

Mechanical; chemical

Question 24

Animals with effective chemical defense often exhibit bright _. Predators are particularly cautious in dealing with prey that display such coloration.

Answer 24

Warning coloration

Question 25

_ makes prey difficult to spot.

Answer 25

Cryptic coloration (camouflage)

Question 26

In some cases, a prey species may gain significant protection by mimicking the appearance of another species. In _, a harmless species mimics a harmful model.

Answer 26

Batesian mimicry

Question 27

_ can also be used by predators to approach prey. For example, the mimic octopus can take on the appearance and movement of more than a dozen marine animals.

Answer 27

Mimicry

Question 28

Herbivory

Answer 28

An interaction in which an herbivore eats parts of a plant or alga; +/- interaction

Question 29

_ has led to evolution of plant mechanical and chemical defenses and adaptations by herbivores.

Answer 29

Herbivory

Question 30

Symbiosis

Answer 30

A relationship where two or more species live in direct and intimate contact with one another

Question 31

What are the three types of symbiosis?

Answer 31

- Parasitism - Mutualism - Commensalism

Question 32

Parasitism

Answer 32

One organism, the parasite, derives nourishment from another organism, its host, which is harmed in the process; +/- interaction

Question 33

Parasites that live within the body of their host are called _.

Answer 33

Endoparasites

Question 34

Ectoparasites

Answer 34

Parasites that live of the external surface of a host

Question 35

Many parasites have a complex _ involving a number of hosts.

Answer 35

Life cycle

Question 36

Some parasites change the _ of the host in a way that increases the likelihood that the parasite will be transmitted to the next host.

Answer 36

Behavior

Question 37

Parasites can significantly affect the _ of their host population.

Answer 37

Survival, reproduction, and density

Question 38

Mutualistic Symbiosis (Mutualism)

Answer 38

An interspecific interaction that benefits both species; +/+ interaction

Question 39

Mutualism can be:

Answer 39

- Obligate, where one species cannot survive without the other - Facultative, where both species can survive alone

Question 40

Commensalism

Answer 40

One species benefits and the other in neither harmed nor helped; +/0 interaction

Question 41

_ interactions are hard to document in nature because any close association likely affects both species.

Answer 41

Commensal

Question 42

In general, a few species in a _ exert strong control on that community's structure.

Answer 42

Community

Question 43

Two fundamental features of community structure are:

Answer 43

- Species diversity | - Feeding relationships (trophic structure)

Question 44

_ of a community is the variety of organisms that make up the community.

Answer 44

Species diversity

Question 45

Species diversity has two components:

Answer 45

- Species richness, the number of different species in the community - Relative abundance, the proportion each species represents of all individuals in the community

Question 46

Communities with higher diversity are:

Answer 46

- More productive; they produce more biomass (the total mass of all organisms) - More stable in their productivity - Better able to withstand and recover from environmental stresses - More resistant to invasive species, organisms that become established outside their native range

Question 47

Trophic Structure

Answer 47

The feeding relationships between organisms in a community

Question 48

Trophic structure is a key factor in _.

Answer 48

Community dynamics

Question 49

Food Chains

Answer 49

Link trophic levels from producers to top carnivores

Question 50

Certain _ have a very large impact on community structure.

Answer 50

Species

Question 51

Such species are _ or play a pivotal role in community dynamics.

Answer 51

Highly abundant

Question 52

Dominant Species

Answer 52

Those that are most abundant or have the highest biomass

Question 53

One hypothesis suggests that _ are most competitive in exploiting resources. Another hypothesis is that they are most successful at _.

Answer 53

Dominant species; avoiding predators

Question 54

Keystone Species

Answer 54

Exert strong control on a community by their ecological roles, or niches

Question 55

In contrast to dominant species, _ are not necessarily abundant in a community.

Answer 55

Keystone Species

Question 56

Disturbance

Answer 56

An event that changes a community, removes organisms from it, and alters resource availability

Question 57

The types of _ and their frequency and severity vary among communities.

Answer 57

Disturbances

Question 58

_ and _ are significant sources of disturbance in many ecosystems.

Answer 58

Storms; fire

Question 59

Intermediate Disturbance Hypothesis

Answer 59

States that moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance

Question 60

High levels of disturbance exclude many _ species.

Answer 60

Slow-growing

Question 61

Low levels of disturbance allow _ to exclude less competitive species.

Answer 61

Dominant species

Question 62

The large-scale fire in Yellowstone National Park in 1988 demonstrated that communities can often respond very _ to a massive disturbance.

Answer 62

Rapidly

Question 63

Ecological Succession

Answer 63

The sequence of community changes after a disturbance

Question 64

Primary Succession

Answer 64

Occurs where no soil exists when succession begins

Question 65

Secondary Succession

Answer 65

Begins in an area where soil remains after a disturbance

Question 66

Abandoned agricultural land may return to its original state through _.

Answer 66

Secondary succession

Question 67

_ have the greatest impact on biological communities worldwide.

Answer 67

Humans

Question 68

Both terrestrial and marine ecosystems are subject to _.

Answer 68

Human disturbance

Question 69

Human disturbance to communities usually reduces species _.

Answer 69

Diversity