Flashcards in chapter 18 Deck (54)
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31
Removal of a keystone species can cause
a community to collapse
32
keystones species that affect communities by influencing the structure of a habitat.
Ecosystem engineers
33
the hypothesis that more species are present in a community that experiences occasional disturbances than in a community with either frequent or rare disturbances.
Intermediate disturbance hypothesis
34
When disturbances are rare, populations
grow until resources are scarce, and competitively superior species become dominant
35
When disturbances are frequent, habitats
typically support a small number of species that are adapted to disturbances.
36
When disturbances occur at an intermediate frequency,
both types of species can persist
37
a linear representation of how different species in a community feed on each other.
Food chain
38
a complex and realistic representation of how species feed on each other in a community.
Food web
39
a level in a food chain or food web of an ecosystem.
Trophic level
40
the autotrophs that convert light energy and CO2 into carbohydrates through photosynthesis.
Producers
41
a species that eats producers.
Primary consumer
42
a species that eats primary consumers
Secondary consumer
43
a species that eats secondary consumers
Tertiary consumer
44
a species that feeds at several trophic levels.
Omnivore
45
within a given trophic level, a group of species that feeds on similar items (e.g., guilds of leaf eaters); members of the group are not necessarily related
Guild
46
an interaction between two species that does not involve other species
Direct effect
47
The direct effect of one species often sets off a chain of events that
affect other species in the community
48
an interaction between two species that involves one or more intermediate species.
Indirect effect
49
indirect effects in a community that are initiated by a predator.
Trophic cascade
50
Indirect effects can occur
between communities.
51
when the abundances of trophic groups are determined by the amount of energy available from producers
Bottom-up control
52
when the abundances of trophic groups are determined by the existence of predators at the top of the food web
Top-down control
53
If food webs have three trophic levels, top-down control by predators would
reduce the abundance of herbivores, leading to an increase in vegetation.
54
