Communities are always changing (ecological succession) Flashcards
The process of succession in a community is …?
The change in species composition over time
Who am I?
Each stage of community change during the process of succession.
Seral stages
Who am I?
The earliest species to arrive at a site
Pioneer species
What is the final serial stage in the process of succession?
Climax community
Who am I?
The development of communities in habitats that are initially devoid of plants and organic soil (e.g.: Sand dunes, lava flows, exposed soil after glacier retreat.)
Primary succession.
Who am I?
the development of communities in habitats that have been disturbed and include no plants but still can contain organic soil. (As time passes, plants are colonizing the area)
Secondary Succession
Who am I?
Any relatively discrete event in time that disrupts ecosystem, community or population structure and changes resources, substrate availability or the physical environment.
Disturbance
What are the 3 sources of disturbance and give an example for each.
- Biotic: outbreak of insects
- Abiotic: Fires, storms
- Human-driven: accidental spill of oil in the water
a) Fill in the blank : Disturbance drives ____.
b) Explain the above statement.
a) diversity
b) more species are present in a community that occasionally experiences disturbances than in a community that experiences frequent or rare disturbances.
Fill in the blank:
a) When disturbance is very high, only ___ species will be able to persist in the community.
b) When disturbance is moderate, diversity is ____ because species that arrived at both early and late stages will be able to coexist.
c) When disturbance is not frequent, communities will be mainly composed of ___ species and outcompete and exclude ___ species.
a) pioneer
b) maximized
c) climax, pioneer
a) T/F: The composition of ecological communities stays stagnant over time.
b) As such, ecological succession represents the ___, ___ and ___ pattern of colonization and extinction on a site by species populations.
a) False: changes in time
b) nonseasonal, directional, continuous
Early (pioneer) and late succession (climax) species possess different traits: in general, ___ species are better dispersers but weak competitors. ___ species are poor dispersers but strong competitors.
pioneer, climax
Ecological succession ___ (Never/eventually) comes to an end. Disturbance events ___ (stop/reset) the successional process pushing communities back to earlier seral stages. Therefore, the idealized concept of climax communities is ___ (hardly/often) observed in nature, and landscapes are better represented by a mosaic of different seral stages.
never, reset, hardly
What allows species in early and late successional stages to coexist in the landscape?
Disturbance. As such, species diversity increases at intermediate levels of disturbance (i.e., the intermediate disturbance hypothesis)
Who am I (Fire-independent biomes, fire-sensitive biomes, fire-dependent biomes)
a) When fire never or very rarely happens either because climatic conditions do not permit it or because there is not enough biomass to carry fire (deserts, glaciers, etc)
b) Damaged by fire that disrupts ecological processes.
c) Where species evolved in the presence of periodic fires and depend on them to complete their life-cycle.
a) Fire-Independent biomes
b) Fire-Sensitive biomes
c) Fire-Dependent biomes
