Ecology: Communities

Organizational Hierarchy of Life Most Complex Least Complex biosphere ecosystem community population organism organ system organ Living tissue cell organelle macromolecule Non-living molecule atom sub-atomic particles

Term Definition Population Community Ecosystem Biosphere Individuals of one species that occupy a given environment Community All populations in a common environment Ecosystem Organisms in community plus nonliving factors Biosphere Zones of air, land and water at earth’s surface occupied by living things

Interactions in Communities -Competition -Predation -Symbiosis

Competition Relates to Niche Overlap Degree of competition is proportional to the overlap in ecological niches of competing species Ecological niche = total way of life of all members of a species --Habitat --Physiological needs such as temperature, moisture, nutrients --Behavior --Interactions with other species

Outcomes of Competition Competitive Exclusion = One species eliminates the other Grown in Separate Flasks Grown in the Same Flask

Outcomes of Competition Resource Partitioning: Use of small differences in environment to fulfill needs Figure: 39.2 Title: Resource partitioning Caption: Each of these five insect-eating species of North American warblers searches for food in different regions of spruce trees.

Outcomes of Competition Character Displacement: Through natural selection, two species diverge in characteristics that overlap

Theoretical vs. Actual Niche Theoretical Niche Defined by Physiological Limits: needs for food, water, temperature Actual Niche Portion of Theoretical Niche that is used, limited by competition

Competition Between Two Species of Barnacles for Region Near the Ocean Surface Barnacle C, theoretical niche Barnacle C, Actual niche theoretical and Barnacle B, actual niche

Applying Your Knowledge Character Displacement Competitive Exclusion Resource Partitioning Which one involves the use of different features of the environment so that two species can coexist in the same area? Which one involves physical changes in two separate species? Which one involves the elimination of one of the competing species?

Effects of Predation Predation = eating of live organisms Eliminates old and weak individuals Regulates numbers of both predators and prey Coevolution of predator and prey Regulates diversity of populations in community “A keystone species plays a major role in determining community structure, one that is out of proportion to its abundance in the community. Removal of the keystone species dramatically alters the community.” When Pisaster present, 15 species can be sustained, including mussels, limpets, barnacles, chitons. Only 8 species remain after removing Pisaster, mussels (favorite food of Pisaster) and barnacles predominate. “Mussels outcompeted algae and other invertebrates.” The sea star Pisaster is a keystone species in aquatic communities in the Pacific Northwest.

Population Cycles in Predators and Prey Figure: 38.E1 Title: Population cycles in predators and prey Caption: Snowshoe hares and their lynx predators are graphed on the basis of the number of pelts received by the Hudson Bay Company.

Coevolution of Predator and Prey Camouflage hides prey

Symbiosis Close Interaction Between Species Parasitism One helped , other harmed

Symbiosis Mutualism Both helped

Symbiosis Commensalism One helped, other neither helped nor harmed

Applying Your Knowledge Mutualism Commensalism Parasitism Which type of symbiosis is operative if A barnacle attaches to a whale so it can feed on organisms encountered as the whale swims but the whale is unaffected by the barnacle? Athlete’s foot fungus starts growing between your toes?

Will the Monarch Butterfly be affected by the development of herbicide resistant crops?