Transcript Part 1 - glenbrook s hs

Ch. 19 - Communities and Ecosystems
How do organisms interact in a community?
Properties of a community:
• Diversity - variety of different
kinds of organisms - richness and
relative abundance of organisms
(see left)
• Form of Vegetation -types and
features of plants determine kinds
of animals in a community
• Stability - community’s ability to
resist change and return to its
original species composition after
being disturbed.
• Trophic structure - feeding
relationships among the speciespassing nutrients from plants to
animals
Interactions in Communities:
• Interspecific competition - various kinds of interactions between species.
Competition for resources (such as food), with competing species, or with ones
own population.
Ex: Competitive exclusion principle : in Paramecium populations (see above).
- 2 species that are so similar that they compete for same limiting resources
cannot coexist in the same place. The inferior competitor will be eliminated.
• Ecological niche - the total of a
species’ use of biotic and abiotic
resources - how it fits into an
ecosystem; its “job.”
• Resource partitioning differentiation of niches that enables
similar species to coexist in a
community. One species may evolve
enough to use a different set of
resources. Ex: lizards (see left)
• Predation: Predator = consumer
Prey = food species (including
plants)
• Predator Adaptations: acute senses,
claws, teeth, stingers, poisons
• Plant Defenses: chemical toxins in
plants, thorns
• Animal Defenses - hiding, fleeing,
cryptic coloration (camouflage),
warning coloration.
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Batesian mimicry - a palatable or
harmless species mimics an
unpalatable or harmful model.
Ex. Viceroy butterfly mimics
Monarch butterfly (tastes bad)
Mullerian mimicry - 2 or more
unpalatable species resemble each
other. Ex: cuckoo bee and yellow
jacket (see left)
Keystone predator - a species that
reduces the density of the strongest
competitors in a community. Helps
maintain species diversity. Ex: sea
stars eating abundant mussels
Q: What would happen if humans
removed the sea stars?
A: More mussels, mussels would eat
much of the kelp, sea otters would
disappear.