Community Ecology

Question 1

Community

Answer 1

an association of interacting species inhabiting a defined area at a particular scale over a particular span of time

Question 2

Communities are often considered as

Answer 2

associations of a particular group
taxonomic, guilds(live same way), life form, functional

Question 3

Foundational species

Answer 3

Species which provide a key role in shaping structure within a community
coral reefs

Question 4

Keystone species

Answer 4

Species that have a disproportionate impact the community structure relative to the abundance of other species
If removed, the loss of keystones leads to a dramatic change in structure

Question 5

Invasive species

Answer 5

Species that are not native to the habitat and disrupt the community
* Characterized by an ability to grow quickly and reduce local biodiversity

Question 6

Community structure includes:

Answer 6

-the relative abundance of species within the
community
-the number of species & diversity
-species composition

Question 7

Community diversity is a combination of the

Answer 7

1) Total number of species there are as well as
2) their relative abundance

Question 8

Species Richness (s)

Answer 8

the number of species in a community

Question 9

Species Evenness

Answer 9

the relative abundance of the various species within a community.

Question 10

Species Diversity

Answer 10

a measure of diversity that increases with species evenness and species richness

Question 11

Species abundance

Answer 11

measure of how common or rare a species is

Question 12

how can species abundance be measured (3)

Answer 12

1)Number of individuals
2) Species cover- visual estimation(algae, plants)
3) Species biomass

Question 13

measuring Species biomass

Answer 13

• Quantifiable as fresh or dry weight(plants), slow and destructive, precise

Question 14

measuring number of individuals

Answer 14

Used when organisms form distinct
entities, like birds.
not useful for clonal organisms

Question 15

measuring species cover

Answer 15

Visual estimation. Used when identifying individuals is
not trivial, like in algae, plants. Quick and non-destructive but less precise

Question 16

Species dominance

Answer 16

communities include a dominant species usually
few species will be dominant or rare. Most species in the community will occur in moderate abundances

Question 17

if only one or two species dominate a
community,

Answer 17

a majority of the interactions within that community
will involve those species

Question 18

bundance is usually quantified in__________ – and graphed using a _______________ distribution

Answer 18

relative terms, lognormalw

Question 18

in species abundance distributions, most species have
very few species have

Answer 18

intermediate abundances
high numbers or low numbers

Question 19

why does overlooking rare species happen often in abundance curves?

Answer 19

the more you sample, the more species you will find and will come closer to a lognormal distribution curve

Question 20

the more diverse a community is

Answer 20

the more stable it is

Question 21

Gamma diversity

Answer 21

OVERALL diversity within a region / landscape

Question 22

Alpha diversity

Answer 22

Diversity within a particular area within a region / landscape
* Consider it a subset of gamma

Question 23

Beta diversity

Answer 23

a measure of the diversity among locations within a region.
* Usually measured as the amount of species change between
ecosystems, calculated as:
* gamma divided by alpha.
β diversity tells you how different patches are from each
other

Question 24

Species evenness

Answer 24

-The relative population size of each species
-An ecosystem dominated by one species will have
low evenness
ie species being represented equally

Question 25

Biodiversity=

Answer 25

species richness and evenness

Question 26

Shannon-Wiener diversity Index

Answer 26

(H’)

Question 27

s =

Answer 27

number of species in community

Question 28

pi =

Answer 28

proportion of the ith species.

Question 29

Rank Abundance Curves:\
where are high abundance species plotted

Answer 29

Plot of relative abundance of species against their rank in
abundance
-The flatter the curve (aka, decreased slope), the more even the community
-Dots ranked according to their abundances, with high-abundance species plotted on the left side of the curve.

Question 30

What are the factors that increase / decrease biodiversity?

Answer 30

(1) Time-more time to evole and colonize, higher biodiversity
(2) Global change-pollution, invasive species decrease biodiversity
(3) Complexity-more complex envonments more biodiversity
(4) Exploitation and limitation, some predator, nutrient limitation, decrease competition and increase biodiversity

Question 31

how does environment complexity influence biodiversity

Answer 31

heterogenous environment –> more niches, more biodiversity
homogenous environment –> less niches, less biodiversity

Question 32

Species composition:

Answer 32

the species that occur in a given community at a given time

Question 33

How does species diversity influence ecological function?

Answer 33

1. complementarity
   2.facilitation
   3.species selection

Question 34

complementarity

Answer 34

-A given ecological service will be at its greatest for
communities in which all resources and/or
microenvironments are being exploited / occupied.
-a single species with a single niche can only
make use of a fraction of the environmental variation

Question 35

Facilitation

Answer 35

-Some species may enhance the growth of others
ie reduce salinity
-May be particularly important in stressful environments

Question 36

Species selection / sampling effect

Answer 36

-Basic idea is that species differ in the inherent rates of delivery of ecological services
As the number of different species increase in a community over time, the odds of said community containing at least one species with enhanced function increases
-is not a benefit of diversity per se, but rather it increases the probability of enhanced ecosystem function.

Question 37

Increases in genetic diversity can lead to an

Answer 37

increases in
species diversity within a community.

Question 38

Genotypes likely differ in

Answer 38

• how species forage to resources,
• where plants put roots and leaves,
• susceptibility to disease,
• ability to outcompete rivals.