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COMMUNITY ECOLOGY
OBJECTIVES:
• Describe types of relationships among organisms.• Compare primary and secondary succession.
Community Interactions
Community = a group of populations of different species living close enough to interact.
Types of Interactions:•Competition,•Predation,•Symbiosis.
Competition
• The competitive exclusion principle states that when two species compete for the same resource or niche, eventually the one with the slight reproductive advantage will eliminate the other.
Predation• A true predator kills and eats the
other animals (prey).
• A parasite spends most or all of its life living on another organism (host) and feeding on its tissues.
• A herbivore is an animal that eats plants.
SymbiosisSymbiosis = “living together”; several types:
Mutualism =
both species benefit.
Parasitism =
one organism benefits and the other is harmed.
Commensalism = one organism benefits; the other is neither harmed nor benefited.
Ecological Succession
http://www.youtube.com/watch?v=V49IovRSJDs
Succession – gradual change in the composition of species over time; frequently following a disturbance.
1. Primary succession - succession on a new site by pioneer species such as lichens; eventually larger plants replace the pioneer species.
Lichen = fungus living with algae or cyanobacteria (mutualism).
Example: colonization after volcanic eruption.
Primary succession
2. Secondary succession – changes occurring where soil and vegetation already exist.
Example: gradual changes after a fire.
• Climax community =stable, mature community that undergoes little succession.
Secondary succession
Hmm…1. Does primary or secondary succession take longer? Why?
2. Are pioneer species r-selected or K-selected species?
3. How do species cause changes in the habitat that will result in different species composition?
Species Diversity= measures the number of different species in a community and the relative abundance of each species.
Dominant species have the highest biomass (the sum weight of all members of a population).
Keystone species have a strong influence on the survival of other species; their removal results in dramatic changes in the makeup of species in a community.
Keystone species examples: sea otter, grizzly bear, wolf.
Invasive species:http://www.youtube.com/watch?v=HAY_UsGjyZk
An introduced (non-native) species that may compete with native species for resources such as food, space, and water.
Examples: tamarisk, zebra mussels, kudzu.
Note: Most non-native species are not invasive.
Hmm…• How do keystone species maintain balance in ecosystems?
• How does the introduction of a non-native species influence the balance of an ecosystem?
MATH CONNECTION
The daily caloric requirements for male versus female killer whales (orcas) is shown below:
• Male killer whale: 308,000 kcal/day• Female killer whale: 187,000 kcal/day
Calculate the average caloric value of a sea otter assuming a male orca consumes five sea otters each day to meet its caloric requirement. Give your answer to the nearest hundredth.