BIOL 104 - Unit 4 Flashcards
How does biodiversity change?
Define community.
A group of interacting species in the same place @ same time
What is community disturbance?
any relatively discrete event in time that disrupts ecosystem, community, or population structure and changes resource availability/physical environment
what is succession?
repeatable/sequential change in community composition over time after a disruption
primary succession and example
succession with new parent material. mt. saint helen
secondary succession and example
when plants/animals re-establish after a disturbance (ex: australian bushfires)
draw a graph of succession with axis of frequency of disturbance and intensity of disturbance
how does succession work? (4)
- colonizers arrive after disturbance (opportunistic species: r-selected)
- other species arrive, possibly community development
- theoretically reach “climax community” under stable environment
- disturbance resets succession
what are some examples of plants throughout succession
annual, perennial plants/grass, shrubs, softwood trees (pines), hardwood trees
differentiate between “r” and “K” selected species
r: exponential, density independent, high mortality for offspring, unstable enviro (jellyfish)
K: logistic growth, density-dependenet, low mortality for offspring, stable enviro
Name 3 different mechanisms for succession
- Tolerance
- Inhibition
- Facilitation
Tolerance
No critical interactions between early and late succession. Success of a species is limited by its tolerance to a specific limited factor (like Nitrogen). Early-successional species have no impact on establishment of later successional species. later successional species have better tolerance
inhibition
early succession makes it harder for later succession to survive. later succession are prevented until early dies and opens us space for late to grow (environmental stress/consumers)
facilitation
early successional species change environment so enviro is more hospitable for later successional species to invade
primary succession is always governed by ______ model
facilitation
secondary succession is governed by _____ models
facilitation, inhibition, and tolerance!
Under the inhibition model, what stage of succession plants can colonize a site after disturbance?
any stage, but usually late-stage wins over long term because they die less frequently
In the tolerance model, what effect do early succession species have on late succession?
No effect. Late succession species tolerate early succession species and late do better because they are better competitors for resources and light.
autogenic vs allogenic processes
autogenic: internal processes within closed community
allogenic: external processes ensure systems are never in equilibrium (immigration of new species, seasonal changes in weather/sunlight)
Describe intermediate disturbance hypothesis
species diversity is highest when disturbance freqency and intensity are intermediate
Define resilience
ability of a community to return back to its original state after a disturbance
resistance
ability of a community to withstand a disturbance
return time
time required to return to equilibrium after a disturbance
What is the relationship between recovery time and resilience?
shorter recovery time = higher resilience
What happens when the threshold of a distrubed system state is passed?
The environment adapts an alternate stable state. (think coral reefs to bleached reefs)
Defining difference between primary and secondary succession?
secondary: build from existing material
primary: start from ground zero, new substrate
adaptive radiation
process in which organisms diversify rapdily from an ancestral species into multitude of new forms
single lineage produces descendants w/ wide variety of adaptive forms
characterized by rapid diversification
what does adaptive radiation require
ecological opportunity
Define ecological opportunity
reduced competition for resources that allows species to quickly diversify and fill different niches previously occupied by another species
