lecture 12: Organisms & Competition

Question 1

intraspecific vs interspecific

Answer 1

an interaction between individuals of the same species brought
about by a shared requirement for a resource in limited supply

same thing as above but different species

Question 2

problems with interspecific

Answer 2

negative effect on both species –each species contributes to the
regulation of the other population as well as its own
* less obvious effects than predation – reduction in growth, reproduction
and survival

Question 3

fundamental niche, realized niche, and niche overlap

Answer 3

full range of conditions/resources used by a species to
survive/reproduce (no overlap)

the portion of the fundamental niche a species actually exploits as a
result of competition
– Species may occupy the portion of their fundamental niche that does not allow the highest
growth and reproduction (fitness)
(little overlap)

when two or more species use a portion of the same resource (eg.
food, habitat) simultaneously (lots of comp)

Question 4

3 Outcomes of Competition

Answer 4

1. Coexistence without competition (not limited)
2. Coexistence with competition (moderately limited)
3. Competitive exclusion principle= two species that have the same resource requirements
   cannot coexist when those resources are scarce
   (one species eliminated)

Question 5

if there is Coexistence with competition (moderately limited), what are the outcomes

Answer 5

Asymmetrical Competition - one species is more strongly affected

Competitively Dominant – species least affected by competition

Resource partitioning – different species using the same resource at different times to minimize competition

Question 6

competition: evidence in plants and results

Answer 6

Plants compete with neighbouring plants of the same or different species

– results in changes in growth rates (plant size, shape), reproduction

Question 7

plants: Interactions are complicated by…

Answer 7

roots occupy soil
– Root competition - water & nutrients
– stems & leaves occupy atmosphere
– Shoot competition – light

Question 8

competition: evidence in animals

Answer 8

When two species compete for the same resources, the presence of one species can cause the other species to reduce its use of resources (niche contraction)

– expansion of a realized niche in the absence of another competing
species (Competitive Release)- the opposite of above

Question 9

Competitive release

Answer 9

the elimination of a competitor allows a previously limited species to expand its range or population

Question 10

If interspecific competition is often asymmetrical how are less competitive
species able to persist?: Environmental gradients

Answer 10

Abiotic conditions exist along a continuum where ideal conditions for
different species may shift over the range and alter competitive ability

Question 11

If interspecific competition is often asymmetrical how are less competitive
species able to persist?: temporal variations

Answer 11

Competing species may evolve to maximize their resource utilization at
different time periods to avoid competition

Question 12

If interspecific competition is often asymmetrical how are less competitive
species able to persist?:  Multiple Resources

Answer 12

Species are often competing over multiple resources with multiple
different adaptations (more
complicated picture).

Adaptations that make them competitively dominant for one
resource may not aid, or even hinder, their competitive ability for
others