chapter 19 Flashcards
Succession occurs in a community when
species replace each other over time.
the process by which the species composition of a community changes over time.
Succession
each stage of community change during succession.
Seral stage
the earliest species to arrive at a site; typically are able to disperse long distances & arrive quickly at disturbed sites
Pioneer species
: the final seral stage in the process of succession; generally composed of organisms that dominate in a given biome.
Climax community
how long can succession in a community take
weeks or months or hundreds of years
the clearest way to record succession in a community.
Direct observation of changes over time
What are the assumptions when using a chronosequence to document succession?
Various sites have similar abiotic conditions
The sites pass thru the same stages of growth
a sequence of communities that exist over time at a given location.
Chronosequence
can be used to identify the age of the pollen in each layer, and helps to determine the changes in plant species composition around the lake over hundreds or thousands of year
Carbon dating
the development of communities in habitats that are initially devoid of plants and organic soil, such as such dunes, lava flows, and bare rock.
Primary succession
examples of primary succession
Glacial retreat Roads Gravel pads in tundra Strip mines Sea cliff Landslides Volcanic islands Colonization of lava fields Bog succession
Secondary succession occurs
in a habitat that has organic soil but no plants.
the development of communities in disturbed habitats that contain no plants but still contain organic soil (e.g., plowed fields, forests uprooted by a hurricane
Secondary succession
secondary succession examples
Fallow farmland Fallow pastureland Treefall / canopy opening Area cleared by fire Slash & burn farming Cleared forest Flood Dieback Pest outbreak
The use of chronosequences assumes that
older and younger sites pass through similar seral stages
The best approach to analyzing succession is to use
chronosequences, pollen records, and long-term studies of single sites.
Streams undergo rapid succession because
organisms can move downstream from sites that are less disturbed.
What is the difference in the classic and modern explanations for the succession of ponds and lakes?
Succession in the modern model is attributed to periods of extended drought.
When a community experiences succession, which is a common pattern of change in species richness?
increase, plateau, decline
During succession, species richness
increases rapidly at first, followed by a plateau and a small decline.
Which would be a characteristic of an early-succession species?
low shade tolerance
a mechanism in which one species increases the probability that a second species can become established.
Facilitation
a mechanism in which one species decreases the probability that a second species will become established (e.g., by competition, predation, or parasitism).
Inhibition
when can inhibition can prevent movement toward a climax community.
Early in succession
when can inhibition can prevent pioneer species from colonizing and surviving.
Late in succession
we typically observe changing environmental conditions and a progression from small to large life forms when
succession occurs
Why are transient climax communities not stable?
frequent disturbances
a climax community that is not persistent; occurs when a site is frequently disturbed so a climax community cannot persist.
Transient climax communities
Small-scale disturbances in an area with a climax community can allow
growth of species that are not considered climax species
a successional stage that persists as the final seral stage due to periodic fires.
Fire-maintained climax community
