Download Chapter 21 - Green Local Schools

Community Ecology
Ch. 20
(20-1) Species Interactions
• 5 major types
– Predation
– Competition
– Parasitism
– Mutualism
– Commensalism
Predation
• 1 species benefits (predator) while the
other species gets eaten (prey)
• Adaptations:
– Mimicry
– Secondary compounds
– Physical abilities
Predation (cont.)
• Mimicry: harmless species resembles a
poisonous or distasteful species
– Ex: king snake mimics poisonous coral
snake
• Secondary Chemicals: poisonous or
bad-tasting chemicals made from
metabolism
– Ex: poison ivy/oak
Competition
• Caused by niche overlap of 2 or more
species
• Can lead to:
– Competitive exclusion
– Character
displacement
– Resource partitioning
Competitive
Exclusion
• 1 species is
eliminated due to
competition for
same limited
resource
– 2 barnacle
species
Character Displacement
• Evolution of anatomical differences that
reduce competition
– Darwin’s finches
Resource Partitioning
• Species reduce
their use of
shared resource
thus decrease
competition
– Warbler feeding
Symbiosis
• Relationship b/w different species living
in close contact w/ each other
• 3 types:
1. Parasitism
2. Mutualism
3. Commensalism
Parasitism
• 1 species benefits (parasite) while the
other species is harmed (host)
• 2 types:
– Ectoparasite: external
• Ticks, fleas, leeches
– Endoparasite: internal
• Tapeworms
Mutualism
• Both species benefit from one another
– Pollinators & plants
Commensalism
• 1 species benefits while other is not
affected
– Cattle egrets
& Cape
buffalo
(20-2) Properties of
Communities
• 3 community characteristics:
– Richness: # of species it contains
– Diversity: how common a species is
– Stability: resistance to change
• Richness improves stability
Species Richness Patterns
• Communities closer to the equator have
more species
• Species-area effect: larger areas
usually contain more species than
smaller areas
Succession
• Gradual, sequential re-growth of
species in an area
2 Types of Succession
• Primary: development of a community in
an area that never had life before
– Bare rock, sand dune
– Extremely slow process
• Secondary: change of community
makeup after a disturbance
– Farming, flood, fire
– ~100 yrs to return
Key Terms
• Pioneer species: predominate in
early succession
– Small, fast-growing, & fastreproducing
– Ex: weeds, crabgrass
• Climax community: community make-up
that will last for a long time
– Stable end result of succession