Download Ch. 20

Ch. 20
Community Ecology
What is predation?
• Predator eats prey
What are three adaptations of
predators?
• What makes them good at finding,
capturing, and consuming prey?
– acute smell
– heat sensing pits
– venom
– sticky webs
– teeth/mouthparts
– camouflage
– speed
List three adaptations of prey?
• What makes them good at escaping,
avoiding, or warding off predators?
– fleeing
– hiding
– warning coloration
– resembling something inedible
– deceptive markings
– chemical defenses
What is mimicry?
• One species resembles another
What are the two types of
mimicry?
• Batesian – harmless species
resembles a harmful one
• Mullerian – 2 or more dangerous or
distasteful species look similar
What are some plant prey
adaptations?
• Thorns, spines, sticky hairs, tough
leaves, chemical defenses
Define interspecific
competition
• Two or more species
using the same limited
resource
Intraspecific –
same species
competing
Interspecific –
different
species
competing
Competitive Exclusion
• A species is eliminated from a
community because of competition
What is symbiosis?
• Close long-term relationship between
two organisms.
• 3 types:
– Parasitism (-/+)
– Mutualism (+/+)
– Commensalism (+/0)
• Parasitism : one benefits (parasite), one is
harmed (host)
• Exp. fleas, ticks, tapeworms
• Mutualism: both benefit
• Exp. ants and acacia trees
• Commensalism: one benefits, other is
neither helped nor harmed
• Exp. cattle egrets and cape buffalos, sharks and
remoras
Patterns in Communities
Succession
What is succession?
• Gradual sequential re-growth of a
community.
Ecological succession
• Gradual, sequential regrowth of a
community
• years or decades
• usually after a disturbance
Mt. St. Helens
What’s the difference between
primary and secondary succession?
• Primary – no soil previously; area
previously did not support life
• Secondary – soil already intact; follows
disruption of a pre-existing community
Primary succession
• Begins with virtually lifeless area
without soil, then…
– bacteria
– lichens & mosses
{
make
soil
Once there’s soil, other plants can
grow:
– grasses
– shrubs
– trees
When is primary succession likely
to occur?
•
•
•
•
On bare rock
Sand dunes
After volcanic eruption
On concrete (like an abandoned
parking lot)
What is a pioneer species?
• First species in an area
• Predominate early succession
• Characteristics: small, grow quickly,
reproduce quickly, disperse seed
easily
What organisms are typically found
in the early stages of primary
succession?
• Lichens – form soil → Grasses/weeds
→ Mosses → Eventually larger plants
and finally trees
• Large conifers may be found in the
end stage of primary succession in
northern latitudes (pines, balsams,
spruces)
Secondary succession
• Existing community cleared,
but base soil is still intact
burning releases
nutrients formerly
locked up in the
tissues of tree
the disturbance
starts the process
of succession
over again
When is secondary succession likely
to occur?
• After forest fires, strong storms,
farming, logging, mining
Organisms found in early stages of
secondary succession?
• Weeds → Perennial grasses and
shrubs → Hardwood trees eventually
(deciduous forest)
Climax Community
• Plant community dominated by trees
• Representing final stage of natural
succession for specific location
– stable plant community
– remains essentially unchanged in species composition
as long as site remains undisturbed
• birch, beech, maple,
hemlock
• oak, hickory, pine