Ecology - Week 10

Question 1

What is a niche?

Answer 1

combination of biotic and abiotic factors that create an environment in which the organism is able to thrive

• physical habitat (or home) in which a species is found
• all the resources a species uses (ie. food)
• function or role a species plays in a community of organisms (interactions)

Question 2

What is niche differentiation (niche segregation/separation/partitioning)?

Answer 2

competing species inhabit different niches
different 
- location/timing
- different resources
- using resources in different ways

Question 3

What does niche differentiation refer to?

Answer 3

these two competing species inhabit different niches in such a way that they are able to coexist:

• wherever the two species’ niches overlap, they will be in competition, which will reduce their fitness
• depending on how much this competition reduces their fitness, individuals that avoid competition by inhabiting a slightly different niche may end up having higher fitness
• if one of the species is a stronger competitor, it will be able to occupy more of its fundamental niche (excluding the weaker competitor)

Question 4

In terms of niches, which species may have higher fitness?

Answer 4

depending on how much this competition reduces their fitness, individuals that avoid competition by inhabiting a slightly different niche may end up having higher fitness

Question 5

What is a fundamental niche

Answer 5

full range of resources (conditions) a species is able to use (tolerate) in the absence of competition (and/or other negative interactions)

Question 6

What is a realized niche?

Answer 6

range of resources species are able to use in presence of competitors

Question 7

For any particular species, is the fundamental or realized niche larger?

Answer 7

fundamental niche will be larger

• think of the fundamental niche as the maximum range of resources an organism can make use of, under ideal conditions (ie. no competitors)
• where the niches of the two species overlap, there will be increased interspecific competition for resources
• this can limit an organism’s ability to thrive within that range, and effectively reduce the range of resources it is able to exploit

Question 8

What is intraspecific competition?

Answer 8

competition between conspecifics

Question 9

What is interspecific competition?

Answer 9

competition between heterospecifics

Question 10

When should we expect there to be competition for resources?

Answer 10

whenever niches overlap, and whenever resources are finite

Question 11

Why do individuals from the same species (conspecifics) often experience a larger amount of niche overlap?

Answer 11

because they belong to the same species, and share the same fundamental niche

Question 12

How is it possible for individuals from the same species (conspecifics) to display niche differentiation?

Answer 12

often, we can characterize a species as having a particular fundamental niche, however, in many cases conspecifics will have different fundamental and/or realized niches

Question 13

In the case of both intraspecific and interspecific competition, what should we expect?

Answer 13

because the supply of resources is finite/limited, resource use by some individuals will reduce the total amount of resources available to other individuals

Question 14

If an interaction between two individuals is a competitive interaction, what should we expect?

Answer 14

expect fitness of each individual to be higher when alone than when in the presence of a competitor