Lecture 14

Question 1

Communities

Answer 1

• groups of interacting species that occur together at the same place and time
• Ecologists usually define communities based on physical/ biological characteristics

Question 2

Physically Defined

Answer 2

• might encompass all the species in a sand dune, a mountain stream, or a dessert

Question 3

Biologically Defined

Answer 3

• this approach emphasizes the importance of abundant species, such as trees
• Ex. kelp forest

Question 4

Ecologists usually consider a subset of _____

Answer 4

• species when they define and study communities

Question 5

Subset of Species can be Defined by

Answer 5

• taxonomic affinity
• guild
• functional group

Question 6

Taxonomic Affinity

Answer 6

• all bird species in a community

Question 7

Guild

Answer 7

• Group of species that use the same resources

Question 8

Functional Group

Answer 8

• Species that function in similar ways, but do not necessarily use the same resources
• Ex. C4 group

Question 9

Trophic Levels

Answer 9

• Primary producers (autotrophs) - plants and algae
• Primary consumers - herbivores
• Secondary consumer - carnivores
• Tertiary consumers - carnivores

Question 10

Food Webs

Answer 10

• tell little about the strength of interactions or their importance in the community
• do not include non-trophic interactions

Question 11

Horizontal Interactions

Answer 11

• competition

Question 12

Interaction Webs

Answer 12

• more accurately describe both the trophic (vertical) and non-trophic (horizontal) interactions than a traditional food wed

Question 13

Community Structure

Answer 13

• the set of characteristics that shape communities

Question 14

Species Richness

Answer 14

• the number of species in a community

Question 15

Species Evenness

Answer 15

• relative abundances compared with one another

Question 16

Species Diversity

Answer 16

• combines species richness and species evenness

Question 17

Biodiversity

Answer 17

• described diversity at multiple spatial scales
• From genes to species to communities
• Implicit is the interconnectedness of all the components

Question 18

Genetic Diversity

Answer 18

• affects the viability of populations
• Which in turn affects species diversity
• The number of community types in an area is critical to diversity at larger regional and latitudinal scales

Question 19

Rank Abundance Curve

Answer 19

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

Question 20

Relative Abundance

Answer 20

• suggest what species interactions might be occurring
• Community A, the dominant species might have a storing negative effet on the three rare species
• Experiments that add or remove species are used to explore these relationships

Question 21

Species Composition

Answer 21

• the identity of species in a community
• The identity of species is critical to understanding community structure

Question 22

Species Accumulation Curve

Answer 22

• species richness is plotted as a function of the total number of individuals that have been counted
• Curves can help determine when most or all of the species in a community have been observed

Question 23

Interaction of Multiple Species

Answer 23

• Communities can be characterized by complex networks of direct and indirect interactions that vary in strength and direction

Question 24

Direct Interactions

Answer 24

• occur between 2 species
• Ex. competition, predation, and facilitation

Question 25

Indirect Interactions

Answer 25

- occur when the relationship between 2 species is mediated by a third (or more) species

Question 26

A Trophic Cascade

Answer 26

- Strong linear relationship of direct effects between organisms that eat one another - The negatives are causing -/+ affects

Question 27

Trophic Facilitation

Answer 27

- a consumer is indirectly facilitated by a positive interaction between its prey and another species

Question 28

Competitive Networks

Answer 28

- competitive interactions among multiple species in which every species negatively interacts with every other species - Strong direct competition is buffered, competitive interactions weaker, and no one species dominates

Question 29

Interaction Strength

Answer 29

- magnitude of the effect of one species on the abundance of another species

Question 30

Dominant Species or Foundation Species

Answer 30

- have large effects on other species - This species’ diversity, by virtue of their considerable abundance or biomass

Question 31

Ecosystem Engineers

Answer 31

- they create, modify, or maintain physical habitats for themselves and other species - Are dominant species

Question 32

Keystone Species

Answer 32

- have a strong effect because of their roles in the community - Their effect is large in proportion to their biomass/ abundance - Usually influence community structure indirectly, via trophic means - Some can be ecosystem engineers (ex. beavers) - They are building dams that transform the swiftly flowing streams into marshes with wetland plants