Ch 52: Community Ecology

Question 1

biological community

Answer 1

all the populations of interacting species living within a defined area

Question 2

Commensalism

Answer 2

occurs when one species benefits but the other species is unaffected (+/0)

Question 3

Competition

Answer 3

occurs when individuals use the same resources—resulting in lower fitness for both (−/−)

Question 4

Consumption

Answer 4

occurs when one organism eats or absorbs nutrients from another, increasing the consumer’s fitness but decreasing the victim’s fitness (+/−)

Question 5

Mutualism

Answer 5

occurs when two species interact in a way that confers fitness benefits to both (+/+)

Question 6

EX of commensalism

Answer 6

epiphytic orchid grows on a tree host

-uses its excess sap as nutrients

Question 7

Intraspecific competition

Answer 7

same species

density dependent

Question 8

Interspecific competition

Answer 8

occurs when members of different species use the same limiting
can be direct or indirect (ex of indirect: species eats food while destroying food source of another’s)

Question 9

Niche

Answer 9

range of resources and conditions that species can tolerate

Question 10

EX: Paramecium

Answer 10

when both species of bacteria put together, their carrying capacities decreased (forced to share food/resources)
However, eventually the weaker species (P.Caudatum) declined dramatically and starved (could not compete)

Question 11

Competitive Exclusion principle

Answer 11

When superior species uses all the resource space of its competitor, the inferior competitor will disappear

Question 12

Fundamental niche

Answer 12

total theoretical range of environmental conditions that a species can tolerate

Question 13

Realized niche

Answer 13

portion of the fundamental niche that a species actually occupies, given limiting factors such as competition with other species (smaller)

Question 14

How did J.Connell test the Competitive Exclusion Principle?

Answer 14

He removed one of the competitors and observed the response by the remaining species

Question 15

EX: competitive exclusion of Chthamalus barnacles from the lower intertidal zone by Semibalanus barnacles

Answer 15

Chtalamus lives in upper tidal
Semibalanus in lower

Chthamalus do not occur in the lower intertidal zone b/c they are outcompeted by Semibalanus

Question 16

Fitness trade-off

Answer 16

an inevitable compromise in adaptation
If individuals are extremely good at competing for a particular resource, they are probably less good at enduring drought conditions, warding off disease, or preventing predation

Question 17

Herbivory

Answer 17

consumption of plant or algal tissues by herbivores

Question 18

Predation

Answer 18

killing and consumption of most or all of another individual (the prey) by a predator

Question 19

Endoparasites

Answer 19

live inside a host’s body and are usually simple and wormlike
ex:tapeworms

Question 20

Ectoparasites

Answer 20

live outside of hosts and typically have adaptations for harvesting fluids from hosts
ex: ticks & mistletoe

Question 21

Parasitoids

Answer 21

free living as adults but have endoparasitic larvae. Parasitoidism is almost always fatal to hosts

Question 22

Constitutive/standing defences

list

Answer 22

defences that are always present and include
–Cryptic colouration and object resemblance
–Escape behaviour
–Toxins and other chemicals
–Schooling and flocking
–Defence armor and weapons

Question 23

Constitutive Defences

Grasshopper EX

Answer 23

resemblance to a leaf enables this grasshopper to escape detection

Question 24

mimicry

Answer 24

the close resemblance of one species to another

Question 25

Batesian mimicry

Answer 25

when nontoxic prey species resemble dangerous prey species. One species benefits

Question 26

Müllerian mimicry

Answer 26

when two harmful prey species resemble each other. Both benefit

Question 27

inducible defences

Answer 27

traits produced in response to the presence of a predator

Question 28

EX: Are mussel defences induced by the presence of crabs?

Answer 28

Average shell thickness is significantly higher downstream in the presence of crabs.
Mussel increase investment in defence when they detect crabs; shell thickness is an inducible defence

Question 29

How can parasites ensure that they get to new hosts?

EX: nematodes

Answer 29

Nematods infect ants -have red end that looks like a berry, therefore eaten by birds
Nematods need birds to complete their life cycle

Question 30

Mutualisms are dynamic

EX: treehoppers

Answer 30

Treehoppers are small insects that feed by sucking the sugar out of the phloem of plants. They secrete honeydew from their posteriors. Ants harvest the honeydew for food

Question 31

Do we see mutualism between ants and treehoppers?

Answer 31

TH benefit only when spiders are common. Ants benefit more when spiders are rare

Question 32

Key attributes of community structure (4):

Answer 32

1. The total number of species
2. The general types and outcomes of interactions among all species
3. The relative abundance of those species
4. The physical aspects that matter -including abiotic factors (size or altitude gradient) and biotic factors (physical structure provided by the dominant vegetation type)

Question 33

food chain

Answer 33

Multiple consumption interactions linked

Question 34

food web

Answer 34

A summary of some or all of the consumption interactions in a community
Multiple food chains combined

Question 35

Bottom-up influences

Answer 35

from plants/algae up the food chain

-amount of nutrients, sunlight, water, etc. determine abundance of primary producers

Question 36

Top-down influences

Answer 36

consumer limits prey pop

ex: wolves don’t tolerate coyotes; coyotes eat mice, so mice—and then hawk—populations have increase

Question 37

Ecosystem engineers

Answer 37

Not only serve as primary producers but also create physical structure that provides habitat for other organisms
Ex: beavers dam streams, making habitat for aquatic animals like frogs and turtles

Question 38

Trophic cascade

Answer 38

When change in top-down influencers cause clear effects 2-3 links away on food web

Question 39

Disturbance

Answer 39

any strong, short-lived disruption to a community that changes the distribution of living or nonliving resources

Question 40

A disturbance’s impact is a function of three factors:

Answer 40

1. Type of disturbance
2. Frequency of disturbance
3. Severity of disturbance

Question 41

EX: Giant sequoia shows damage after a fire..

Answer 41

through their growth rings

- trees withstand many fires within its lifetime and regrow their bark around burned

Question 42

In Primary succession…

Answer 42

organisms colonize bare mineral soil (e.g. volcanic ash, land slide)

Question 43

In secondary succession…

Answer 43

soil is already present, so recovery is faster than primary succession

Question 44

Early successional communities are dominated by species that…

Answer 44

–Are short lived
–Are small in stature
–Disperse their seeds over long distances

Question 45

Late successional communities are dominated by species that…

Answer 45

–Long lived
–Large
–Good competitors for light and nutrients

Question 46

Facilitation

Answer 46

existing species help those that arrive

Question 47

Tolerance

Answer 47

existing species do not affect the arrivals

Question 48

Inhibition

Answer 48

presence of one species inhibits the success of another

Question 49

species richness

Answer 49

number of species present in a given community

Question 50

species diversity

Answer 50

weighted measure that incorporates a species’ relative abundance