Lecture: Chapter 17-18 Community Structure and Factors of Influence Flashcards

1
Q

Communities

A

Groups of interacting species that occur together at the same place and time

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2
Q

Synergistic

A

The interactions are synergistic; they make communities into something more than the sum of their parts

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3
Q

What are communities?

A

In practical terms, ecologists usually define communities based on physical or biological characteristics.

Physical: all the species in a sand dune, a mountain stream or a desert

Biological: all the species associated with a kelp forest, a freshwater bog, or a coral reef

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4
Q

Taxonomic affinity

A

All bird species in a community

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5
Q

Guild

A

Group of species that use the same resources

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6
Q

Functional group

A

species that function in similar ways, but do not necessarily use the same resources

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7
Q

Species diversity and species composition are important discriptors of community structure

A

Community structure is the set of characteristics that shape communities

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8
Q

Species richness

A

the number of species in a community

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9
Q

Species evenness

A

Relative abundances of species comapred with one another. how many individuals belong to each species - are they distributed fairly equally or rather unequally

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10
Q

Species diversity

A

Combines species richness and species evenness

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11
Q

Shannon index

A

H = -E(pi)(ln(pi))

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12
Q

Species diversity (and biodiversity) are often used more broadly to mean the number of species in a community

define biodiversity

A

Biodiversity describes diversity at multiple spatial scales, from genes to species to communities.

  • species diversity
  • genetic variation
  • habitat variation (spatial heterogeneity)
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13
Q

Rank abundance curves

A

Plot the proportional abundance of each species (pi) relative to the others in rank order

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14
Q

Species accumulation curves

A

species richness is plotted as a function of the total number of individuals that have been counted

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15
Q

Species composition

A

identity of species in a community

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16
Q

Two communities could have identical species diversity values, but have completely different species.

A

The identity of species is critical to understanding community strucutre

17
Q

Dominant species or foundation species

A

Have large effects on other species, and thus species diversity, by virtue of their considerable abundance or biomass

18
Q

Keystone species

A

Strong effects because of their roles in the community. Disproportionate impact on the community relative to their abundance or biomass

19
Q

Keystone predators

A

predators that often function as keystone species within communities

20
Q

Food webs

A

Conceptual models of the trophic interactions within communities. Organize species and describe interactions based on trophic or energetic interactions

21
Q

Trophic Levels

A

Primary producers: plants and algae
Primary consumers: herbivores
Secondary consumers: carnivores
Tertiary consumers: carnivores

22
Q

control of energy flow - bottom-up

A

The bottom-up view: the abundance of organisms at a trophic level is determined by the trophic level below it

23
Q

control of energy flow - top-down

A

The top-down view: Energy flow is governed by predator consumption rates at the highest trophic lvel, which influences multiple trophic levels below them. HSS (Hairston, smith, slobodkin) hypothesis. “The world is greeen’

24
Q

Trophic cascade

A

Change at one trophic level results in alternating responses of trophic levels below.

Mediated by “trophic” relations - feeding

25
How are communities characterized?
By complex networks of direct and indirect interactions that vary in strength and direction
26
Direct interactions
occur between two species (e.g. competition, predation)
27
indirect interactions
Occur when the relationship between two species is mediated by a third (or more) species
28
trophic cascade
a carnivore eats an herbivore (a direct negative effect on the herbivore) the decrease in herbivore abundance has a positive effect on a primary producer
29
The keystone predator effect
A predator witha species prefernece selectively removes competitive dominant species allows other species that would be excluded by the dominant competitor to persist
30
species richness
differs among communities due to variation in regional species pools, abiotic conditions and species interactions
31
resource partioning
among the species in a community reduces compeition and increases species richness. Competing species coexist by using resources in different ways/