1. Ch. 19 - Communities and Ecosystems

2. 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 species- passing nutrients from plants to animals

3. 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.

4. 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.

5. 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.