Ch.16-Community Dynamics

Question 0

Physical caracteristics

Answer 0

Aquatic community - have to be in water

Dry community- only certain organisms can live there

Question 1

Community

Answer 1

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

Question 2

Biological characteristics

Answer 2

Coral- built a habitat in an ocean

tree- creates a community

Question 3

Taxonomic subsets (1)

Answer 3

all the species in one taxonomic group w/in the community

Ex: birds

Question 4

Guilds (2)

Answer 4

a group of organisms that make their living in similar ways

Ex: herbivores, seed eater, pollen eater, fungivores

Question 5

Functional Types (3)

Answer 5

a group of species with similar morphological, physiological, behavioral, biochemical, or environmental characteristics/ responses
- don’t necessarily use the same resources
ex; aphids and mosquitos

Question 6

trophic levels (4)

Answer 6

a group of species that obtain energy in similar ways

Question 7

Food Web

Answer 7

a summary of the feeding relationships within an ecological community

Question 8

Subdividing communites

Answer 8

4 main ways
1-taxonomic subsets
2-Guilds
3-Functional types
4-Trophic level

Question 9

How to measure food webs

Answer 9

• watch interactions occur
• examine stomach contents
• examine waste contents
• determine if known prey is present and assume it eaten
• analyze stable isotopes of predator tissue

Question 10

Food web representaions

Answer 10

trophic relationships(=who eats who) in all or part of a community
-can be species, functional groups, taxonomic groups

Question 11

Community food web

Answer 11

trace an entire set of trophic interactions within a community

Question 12

Interaction web

Answer 12

describes both trophic (vertical) and non-trophic (horizontal) community interactions

Question 13

Species interactions

Answer 13

the strength of interactions among species may very from pair to pair
-ex; kangaroos eating grass vs. ant eating grass

Question 14

interaction strength

Answer 14

the degree to which one species affect another

• can be calculated, but is difficult to calculate for entire community
• requires experimental manipulation

Question 15

How to quantify interaction strength:

Answer 15

interactor and target: cage an area and remove interactor

-Large change in target abundance=strong interaction

Question 16

Indirect interactions: Mutualism

Answer 16

(acacia tree and ant mutualism)

Question 17

Indirect interactions: competition

Answer 17

Interference competition: Species A (-)->resource<-(-/+) Species B
~indirect interactions between species A and B

Question 18

Indirect interaction: Competition

Answer 18

Apparent competition: Occurs between two prey species eaten by the same predator(s)
~ex: snails and clams are both eaten by ocutpus

Question 19

Some species have very large effects on whole communites

Answer 19

Large interaction strength

-can be direct or indirect

Question 20

Dominant Species

Answer 20

• Tend to be larger and or extremely abundant
• may provide habitat or food for other species
• may be good competitors for space, nutrients, or light

Question 21

Keystone species

Answer 21

-Found in relatively low abundance and low biomass
-Have a disproportionate effect on community structure
~Ex: sea stars, sea otters, jaguars, beavers, elephants, prairie dogs

Question 22

Types of keystone species

Answer 22

1. Keystone Predators (ex: sea otters)
2. Keystone food resource (Ex: Figs)
3. Keystone habitat modifier (ex: Beavers)
4. Keystone ecosystem processor (ex: Decomposers)

Question 23

Trophic interactions

Answer 23

Involve direct and indirect interactions-Can be:

Bottom-up or Top-Down

Question 24

Bottom-up

Answer 24

-Size of a trophic level is determined by rate of production of its food resource
Ex: Aquatic ecosystem
~primary produces increases-> herbivores increase-> Carnivores increase

Question 25

Top-Down

Answer 25

-Higher Trophic levels determine the size of levels below
-Trophic cascades: effects of predators on prey that alter species in lower trophic levels
Ex: remove sea otters -> Sea urchins increase -> Primary producers are reduced by sea urchins

Question 26

Trophic cascades

Answer 26

effects of predators on prey that alters species in lower trophic levels

Question 27

Why care about interaction strength?

Answer 27

• species with high interaction strength can dramatically affect community structure
• addition or removal of a high-impact species will have dramatic effects on the community