Lecture : Chapters 19-20 Community Dynamics and Landscape Dynamics

Question 1

Community

Answer 1

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

Question 2

Characteristics of communities

Answer 2

species richness, evenness, diversity, composition

Question 3

How do communities change?

Answer 3

Agents of change act on communities across all temporal and spatial scales

Question 4

zonation

Answer 4

change in community structure across the landscape

Question 5

succession

Answer 5

change in community structure over time

Question 6

gradual change

Answer 6

subtle changes include gradual turnover of dominant speices (due to competition), predation and disease

Question 7

catastrophic change

Answer 7

coral death due to bleaching events, the tsuanmi of 2004 which resulted in replacement of some coral species with other species, or no replacement at all

Question 8

Succession

Answer 8

gradual change in species composition in communities over time

Question 9

disturbance

Answer 9

restarts succession

Question 10

succession

Answer 10

results from both biotic and abiotic factors

Question 11

abiotic factors

Answer 11

form of climate, soils, nutrients and water, vary over daily, seasonal, decadal and longer time scales

Question 12

disturbance

Answer 12

discrete event that disrupts community structure and function by injuring or killing some individuals. It also creates opportunities for other individuals.

Question 13

Diseases

Answer 13

initiate community change by causing death or slow growth of a species

Question 14

ecosystem engineers

Answer 14

keystone species can influence community change

Question 15

sere

Answer 15

entire sequence of succession including all comunities during the process

Question 16

seral stage

Answer 16

a distinct community at a point in the succession. Each stage has a characteristic structure and species composition

Question 17

early successional species

Answer 17

high fecundity, effective dispersal, rapid growth, smaller size, good colonizers

Question 18

late successional species

Answer 18

low fecundity, less effective dispersal and colonization, slower growth rate, larger and live longer. However, they have the ability to grow, surive and compete when resources are scarce

Question 19

primary succession

Answer 19

involves the colonization of habitats devoid of life (e.g. volcanci rock, galicaiton). Very slow. Inhospitable initial conditions

Question 20

Seconday succession

Answer 20

involves reestablishment of a community in which some, but not all, organissm have been destryoed by disturbance (e.g. logging, fire, agriculture). Occurs on previously occupied sites

Question 21

Hetereotrophic succession

Answer 21

refers to succession in heterotrophic commmunities involved in decomposition.

studies of succession often vocus on vegetative change, but the roles of animals, fungi, bacteria and other microbes are equally important

Question 22

Henry Cowles

Answer 22

A pioneer of “dynamic ecology”, especially on the sand dunes of Lake Michigan. he developed the concept of ecological succession

Question 23

intermediate disturbance hypothesis, first proposed by Connell 1978

Answer 23

Species diversity should be greatest at intermediate levels of disturbance

At low levels of disturbance, competition determines diversity. At high disturbance levels, many species can not survive or establish

Question 24

Three Models of Succession

Answer 24

Facilitation
Inhibition
Tolerance

Question 25

Facilitation model

Answer 25

Early succesional species modify the environment in ways that benefit later successional species to invade and grow to maturity. The sequence of species facilitaions leads to a climax commnity

Question 26

Climax community

Answer 26

Composed of dominant species that persist over many years and provide stability that can be maintained indefinitely. Only disturbance resets the system.

Question 27

Inhibition model

Answer 27

involves strong competitive interactions. It assumes early species modify conditions in negative ways that hinder both early and later successional species from invading. Eventually early individuals and short-lived species die releasing space for long-lived species

Question 28

Tolerance model

Answer 28

assumes the earliest species modify the environment, but in neutral ways that neither benefit nor inhibit later species. Later species can invade and grow as they can efficiently exploit the available resources

Question 29

Landscape Dynamics

Answer 29

Landscape ecology emphasizes broad spatial scales and the ecological effects of the spatial patterning of ecosystems

Question 30

Fragmentation

Answer 30

Usually accompanied by habitat loss
Results in
- decrease in total habitat area (and thus in total metapopulation size)
- increase in the number of populations
- decrease in average population size
- increase in the length of edges
- decrease in the proportion of “interior habitat”

Question 31

Abiotic changes influence species composition and distribution

Answer 31

Abiotic changes in temperature, light and moisture at the edge of forests

Species composition changes as a function of edge

Question 32

regional differences in species diversity are influenced by area and distance, which determine the balance between immigration and extinction rates

Answer 32

an important concept in biogeography is the species-area relationship: species richness increases with area sampled

Question 33

Species-area curves plot species richness (S) of a sample against area (A) of the sample

Answer 33

The relationship between S and A is estimated by linear regression

S=zA+c

Question 34

island

Answer 34

any kind of isolated area surrounded by dissimilar habitat

Question 35

theory of island biogeography (MacArthur and Wilson, 1967)

Answer 35

A theoretical model to explain how area and distance to mainland influence the equilibrium numbe rof species on an island

Number of species depends on balance between immigration and extinction rates

Question 36

Corridors

Answer 36

Strips of habitat with the designated or incidental function of increasing dispersal among populations

• act as travel pathways
• provide basic requirements for foraging, breeding, refugia