CHAPTER 5 Community Ecology

Question 1

Populations are linked by interspecific interactions that impact the survival & reproduction of the species involved.
“_______”

Answer 1

community ecology
SYNECOLOGY

Question 2

____________ is the study of the interaction between individual species with their environment.

____________is the study of interactions among two or more species or a population with their environment.

Answer 2

Autecology

Synecology

Question 3

Community Structure

• −an assemblage of populations living close enough together for potential interaction
• −most abundant, highest biomass, powerful control over occurrence and distribution of other species.
• −NOT necessarily most abundant, exert strong control due to their ecological roles or niches… Sea Otters!!!
• • number of species & abundance

Answer 3

Community
Dominant Species
Keystone Species
Richness

Question 4

Biodiversity

Communities with higher diversity are:
* More productive and more ____ regarding their productivity
* Better able to ________ from environmental stresses
* ________ to invasive species, organisms that become established outside their native range

Answer 4

stable
withstand and recover
More resistant

Question 5

Species Diversity

Formula

Answer 5

Species Richness
(# of different species)
+
Relative Abundance
(proportion of each different species represents of all the individuals in the community)

Question 6

A keystone species is one that has a ____ effect on the composition of the community.
Removal of keystone species causes a ________ in species richness

Sea otters eat sea urchins which are fierce competitors having a diet of kelp

Answer 6

strong
decrease

Question 7

means that the population sizes and number of species remain constant over time (Equilibrium)

Stability ________ when the ecosystem can withstand disturbances

________ – events that change communities, remove organisms, or alter resource availability.

Answer 7

community stability/ stability
increases
Disturbances

Question 8

Components of Stability

________ – force needed to change the community.
________ – ability of the community to return to prior state (equilibrium) after perturbation.
Elasticity – how ____ to equilibrium
Amplitude – how much ____, and still return to some kind of equilibrium.

Answer 8

Resistance
Resilience
quickly community returns
disturbance community can tolerate

Question 9

Ecological Disturbances

A community in equilibrium is generally _ and __

________ or changes in the environment can throw a community into disequilibrium.

Severe disturbances can cause ________ to environment.

Answer 9

stable and balanced.
Disturbances
permanent change

Question 10

Human activities cause more disturbance than natural events but usually reduce species diversity in communities because they do
________ but keep communities constantly disturbed, and hence in an early colonization.

Answer 10

not allow recovery after disturbance

Question 11

Climax Community

A mature stable community that is the ________ of ecological succession.

This type of community remains the ____ through out the time, if it is not disturbed.

A stable group of plants and animals which is the end result of succession process.

Answer 11

final stage
same

Question 12

• areas of land that are bordered by water
• can serve almost as a laboratory for the study of biogeography

Answer 12

island

The biota of an island is simpler than that of a continental area, and the interactions are easier to understand.

Question 13

There are three types of islands:

1. Islands that were originally part of a ________, but were separated by rising sea levels (land-bridge islands).
2. Islands that are part of a ____.
3. ____ which formed over geological “hotspots”.

Answer 13

nearby continent
volcanic island arc
Seamount chains

Question 14

is the geographical analysis of the biodiversity of the plant and animal species on islands.

Also called insular biogeography.

The species studied in island biogeography include species on land, in freshwater areas, and in the sea.

Answer 14

island biogeography

Question 15

The Theory of Island Biogeography

The theory of island biogeography relates the ________ of the island and the degree of isolation of the island.

Answer 15

number of species on an island to the land area

Question 16

The Theory of Island Biogeography

Proposed by ________ and ____ in the 1960s.

• The theory states that smaller, more isolated islands have ____ numbers of plant and animal species.
• Larger, less isolated islands have a ____ number of plant and animal species and biodiversity.
• Larger, less isolated islands are overall easier for species to find and contain a ____ of habitats.

Answer 16

Robert H. MacArthur and Edward O. Wilson
fewer
higher
diversity

Question 17

The Theory of Island Biogeography

This theory is substantiated by an idea called the ____
* The —– is that a species will have a greater success rate immigrating, or establishing a new home, to a larger island than on a smaller island. The rate of immigration is higher on larger islands due to a higher chance of a species finding the larger island and being able to survive there.

Answer 17

target effect

Question 18

Principle of Island Biogeography

Two significant factors that contributes to the rate of species change are:

Answer 18

the area of the island (size)
It’s distance from the mainland (Isolation)

Question 19

Factors Influencing Species Diversity

Answer 19

Extinction

Immigration

Emigration

Question 20

• is the dying out of a species.
• occur as a result of many environmental and evolutionary factors.
• On an island, dying out of species reduces the overall number of species and the biodiversity.
• Smaller, more isolated islands have a higher rate of —.

Answer 20

extinction

Question 21

• It is the establishment of a home by a species in a new habitat.
• Species are able to immigrate when the habitat meets their needs for survival.
• Species have a greater chance of being able to immigrate to a new island when the island is larger.
• Islands that are more isolated are harder for the species to find and get to. A higher level of immigration contributes to island biodiversity.

Answer 21

immigration

Question 22

• It is the departure of a species from its established habitat.
• Species emigrate from habitats because the home no longer satisfies their needs to survive or thrive.
• —- contributes to the decrease of biodiversity on an island.

Answer 22

emigration

Question 23

Island populations are more likely to go extinct than those on mainland, for several reasons:
1. Populations are typically —-.
1. They have —- genetic diversity.
1. They were — originally adapted to the island habitat.

Answer 23

smaller
less
not

Question 24

Equilibrium & Theory of Island Biogeography

• describes the balance of —- of species on an island.
• Equilibrium is a term that describes the condition of —- amongst several influential factors.
• It state or condition where there is a balance between the rate of species —- on an island.

Answer 24

extinction and immigration
balance
arrival and departure or extinction

Question 25

It is the steady and gradual change in a species of a given area with respect to the changing environment.

The ultimate aim of this process is to ________

All the communities that we observe today around us have undergone succession over a period of time since their existence.

Answer 25

succession
reach equilibrium in the ecosystem.

Question 26

Types of Ecological Succession

Answer 26

Primary Succession

Secondary Succession

Cyclic succession

Question 27

What types of ecological succession?

• Occurs when there are no traces of the original community remaining, including vegetation and soil.
• Pioneer species, such as lichens, are the first to colonize.
• The environment change as new species move in, adding nutrients and generating habitat.

Answer 27

primary succession

Question 28

• Occurs when a disturbance dramatically alters a community but does not completely destroy it.
• Common after disturbances such as fire, logging, or farming.
• Occurs significantly faster than primary succession.

Answer 28

secondary succession

Question 29

This is only the change in the structure of an ecosystem on a cyclic basis. Some plants remain dormant for the rest of the year and emerge all at once. This drastically changes the structure of an ecosystem

Answer 29

cyclic succession

example: cicadas, lay dormant for many years and emerge all at once, drastically changing the ecosystem

Question 30

“A ________ is an intermediate stage of ecological succession advancing towards the climax community.”

A ——– is replaced by the subsequent community. It consists of simple food webs and food chains. It exhibits a very low degree of diversity. The individuals are less in number and the nutrients are also less.

Answer 30

seral community

Question 31

Types of Seres

1. Succession in aquatic habitat.
2. Succession in dry habitat.
3. Succession on a bare rock surface.
4. Succession initiating on sandy areas.
5. Succession starting in saline soil or water.
6. Succession of microorganism on dead matter
7. Development of vegetation in an era.

Answer 31

1. Hydrosere
2. Xerosere
3. Lithosere
4. Psammosere
5. Halosere
6. Senile
7. Eosere

Question 32

Change is the only constant in the universe and the environment is not an exception so is ecological succession. The environment has been dynamic over the life history of the Earth due to several factors:

1.Change in — factors.
2.The —– in the communities.

Answer 32

climatic and physiographic
activities of individuals

Question 33

How Ecological Succession takes place?

Succession will continue until the environment reaches it’s final stage —-

Answer 33

the Climax Community

Question 34

This occurrence of a relatively different sequence of the community over some time in the same area is known as ________. Each phase of —– is called a ________. The initial sere was known as Pioneer seral stage.

While due to disturbance by the community from the later seral stage, it may acquire an earlier seral stage this is relatively rare in occurrence as generally community moves towards the climax.

Answer 34

ecological succession
Sere or seral stage

Question 35

Models of Succession

Answer 35

Facilitator
Tolerate (Competition)
Inhibition

Question 36

is one of the mechanisms of succession where earlier organisms exploit the habitat and act as a Pioneer species. They are most capable of occupying and establishing on the site. Hence this initial species at a given successional stage make the environment more suitable for the lateral successional stage.

Answer 36

facilitator

Only certain species can establish (pioneers)
Modify environment making it more suitable for later species.
Early species eliminated through competition for resources by later arrivals
Sequence continues until current residents no longer facilitate invasion and growth of next species or until no species exists to invade and grow in presence of current adult population

Question 37

e.g. Lepraria (crustose), Pamelia (foliose), and Usnea (fruticose) are lichens that act as —- and break down rock into soil, also play an important role in symbiotic nitrogen fixation and make the soil more fertile for organisms in the next ecological succession stage.

Answer 37

Pioneer species

Question 38

All species in the successional stage have the capacity of establishing on a newly disturbed site. The existing organism in the successional stage has very little impact on later successional stages. The existing species won’t oppose (not severely) or even favour the newly invaded species.

Answer 38

tolerance

Example:
All organisms can start at the same time but due to different life cycles and life histories, they show dominance at different times.

Question 39

Tolerance

• Individuals on any species can arrive and exist as adult under prevailing conditions.
• Modification of environment has little to do with subsequent recruitment of later successional spp.
• Early species eliminated through competition for resources by later arrivals.
• Sequence continues until current residents no longer facilitate invasion and growth of next species or until no species exists to invade and grow in presence of current adult population.

Question 40

Species in the existing successional stage (early species) makes the site less suitable for the development of other species. Hence, they restrict the invasion of invasive species by making the environment less suitable or harsher for upcoming species.
Modification of the environment by early occupants makes it less suitable for recruitment of later successional species (early w/ good colonizing ability).
Early species persist as long as undamaged.
Replacement only occurs when damaged (external force) replaced by more resistant species

Answer 40

inhibition

Question 41

Some plants secrete chemicals to make the soil less suitable for germination and growth of invasive species

Answer 41

allelopathy