Community Ecology

Question 1

What is a biological community?

Answer 1

an assemblage of populations of various species living close enough for potential interaction

Question 2

What are interspecific interactions?

Answer 2

relationships between species in a community
Can affect the survival/reproduction of each species

Question 3

What are the two types of competition?

Answer 3

Intraspecific competition occurs when members of the same species compete for a resource
Interspecific competition occurs when different species compete for resources.

Question 4

What was G.F. Gause experiment about?

Answer 4

grew two types of bacteria, found that each bacteria grew logistic growth model by themselves, but when competitive exclusion occurs when both are in the same culture

Question 5

What is the competitive exclusion principle?

Answer 5

states that two species competing for the same limiting resources cannot coexist in the same place

Question 6

What is resource partitioning?

Answer 6

species evolve to minimize competition by “partitioning” their resources

Question 7

What is the difference between a species’ fundamental niche and realized niche? (for spatially partioning)

Answer 7

fundamental- niche potentially occupied by that species
realized- niche actually occupied by that species
as a result of competition, a species fundamental may differ from its realized niche

Question 8

How can species partition their ecological niches temporally?

Answer 8

When two nocturnal species are competing, one may turn diurnal (active during the day)

Question 9

What is character displacement?

Answer 9

Morphologically similarity and use of resources tend to be more divergent in sympatric populations of two species than in allopatric populations of the same two species

Question 10

What is predation?

Answer 10

refers to the interaction where one species, the predator, kills and eats the other, the prey
predators have many adaptations relating to feeding, such as claws, teeth, etc.

Question 11

What are some behavioral defenses?

Answer 11

hiding, fleeing, self-defense

Question 12

What is aposematic coloration?

Answer 12

Animals with effective chemical defense often exhibit bright warning coloration

Question 13

What is mimicry and which species exhibit this?

Answer 13

mimicking of the appearance of another species
The mimic octopus can take the appearance of more than a dozen marine

Question 14

What is herbivory?

Answer 14

refers to an interaction in which an herbivore eats parts of a plant or alga
Led to evolution of plant mechanical and chemical defense and adaptations by herbivores

Question 15

What is symbiosis?

Answer 15

individuals of two or more species live in direct and intimate contact with one another. Interactions among symbionts could be helpful, harmful, or neutral
ex : mutualism, parasitism, and commensalism

Question 16

What is mutualism?

Answer 16

(+/+ interaction), interspecific interaction that benefits both species
obligate: one species can’t survive without the other
Facultative: both species can survive alone

Question 17

What are some types of mutualisms?

Answer 17

pollination: involve pollen dispersal in exchange for nutrients
tropic: involve partners specialized for obtaining energy and nutrients
Defensive: involve species that receive food or shelter from their partners in return for a defensive function
Dispersive: involve animals that transport and disperse seeds in return for the nutritional value of fruits.

Question 18

What is parasitism?

Answer 18

(+/- interaction), the parasite derives nourishment from another organism (the host), which is harmed in the process

Question 19

What are the different types of parasites?

Answer 19

Endoparasites live in the body of their host, while ectoparasites live on the external surface of a host

Question 20

What is commensalism?

Answer 20

(+/0 interaction), interaction between species that benefits one of the species, but neither harms nor benefits the other

Question 21

What is facilitation?

Answer 21

Species can have positive effects on (+/+ or +/0) on the survival and reproduction of other species without necessarily living in the direct and intimate contact of a symbiosis

Question 22

What are two fundamental features of community structure?

Answer 22

species diversity and tropic structure (feeding relationships)

Question 23

What is species diversity?

Answer 23

variety of organisms that make up the community
made up of species richness and relative abundance

Question 24

What is species richness?

Answer 24

total number of different species in the community

Question 25

What is relative abundance?

Answer 25

proportion each species represents of the total individuals in the community

Question 26

How to directly compare species diversity across communities?

Answer 26

Use the Shannon diversity index
H= -(pA * lnpA + pB * lnpB + pC * lnpC)
where A,B, and C is the relative abundance of each species
Larger values of H means more diversity.

Question 27

How to determine microbial diversity using molecular tools?

Answer 27

the number and abundance of the different sequences of a particular gene in a sample can be used to approximate the number and abundance of microbial species in a sample

Question 28

What are benefits of higher diversity?

Answer 28

more productive and more stable in their productivity
better able to withstand and recover from environmental stresses
more resistant to invasive species

Question 29

What is tropic structure?

Answer 29

The feeding relationships between organisms in a community - key for community structure

Question 30

What is the food chain and the food web?

Answer 30

Food Chain: the transfer of energy up the tropic levels
Food Web: Food chains are not isolated form each other but linked together

Question 31

What is the energetic hypothesis?

Answer 31

The length of the food chain is limited by the inefficiency of energy transfer along the chain
only 10% of the energy stored in on tropic level is converted to energy in one above it

Question 32

Which species have a large impact on community structure?

Answer 32

Dominant species are those that are most abundant or have the highest biomass
Keystone species exert strong control on a community by their ecological roles
Foundation species can dramatically alter their physical environment

Question 33

What is an example of a keystone species?

Answer 33

A sea star’s presence in an environment allows for 20 species present, while without it only 3 species existed.

Question 34

What were the two views of if biological communities are at equilibrium?

Answer 34

Traditional view: most biological communities are in equilibrium
Current view: most biological communities are chance assemblages of species, not in equilibrium

Question 35

What is a disturbance?

Answer 35

an event, such as a storm, fire, or flood that changes a community by removing organisms from it or altering resource availability

Question 36

What is the intermediate disturbance hypothesis?

Answer 36

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

Question 37

What is the correlation between equilibrium and disturbances?

Answer 37

The norm for most communities is that they are not in equilibrium and that they change constantly because of disturbances.

Question 38

What is ecological succession?

Answer 38

sequence of community and ecosystem changes after a disturbance

Question 39

What is primary and secondary succession?

Answer 39

Succession: result of changes induced by vegetation itself
Primary succession occurs when no soil exists when succession begins
Secondary succession beings in a area where soil remains after a disturbance