Lecture 17: community dynamics Flashcards
(20 cards)
What is ecological succession?
A change in community structure (species composition) at a specific location through time.
What drives changes in species dominance and diversity during succession?
Shifting environmental conditions that alter species birth and death rates (b & d).
What is primary succession?
Succession at a site not previously occupied by a community (e.g., sand dunes, bare rock).
What is secondary succession?
succession at a previously occupied site after a disturbance (e.g., after a fire or flood)
What is a disturbance in ecology?
Any process that removes all or part of an existing community.
What are early successional (pioneer) species like?
r-selected: small, fast-growing, short-lived, high reproduction and dispersal, poor competitors.
How can small-scale disturbances affect diversity?
They create gaps that increase environmental heterogeneity and promote colonization.
What does the Intermediate Disturbance Hypothesis state?
Species diversity peaks at intermediate levels of disturbance.
What happens to diversity without disturbance?
Late species dominate, reducing diversity.
What happens with too much disturbance?
Community is stuck in early succession; low diversity.
just k selected, then wipe out, then k selected
Why are forest fires important in some ecosystems?
They maintain successional cycles and prevent fuel buildup that can lead to uncontrollable fires.
What are “controlled” or “prescribed” burns?
Human-managed fires to reduce fuel and maintain healthy ecosystems.
What is a habitat patch?
A homogeneous area with resources and conditions needed for a population to persist.
What factors affect species dispersal between patches?
Distance, habitat suitability between patches, and barriers like mountains or oceans.
What does Island Biogeography Theory propose about species richness?
It is a dynamic balance between colonization and extirpation.
How does distance from other patches affect colonization?
Greater distance reduces colonization rates → lower species richness (S)
How does patch size affect extirpation?
larger patches reduce extirpation rates → higher S due to more niches and resources.
What happens when colonization = extirpation?
Equilibrium species richness is reached; richness stable, composition may change.
What is the edge effect?
High species diversity due to mixed environmental conditions at the borders of habitat patches.
What’s the difference between edge and interior species?
Edge species tolerate variable conditions; interior species need stable environments.
