dna – october 4, 2010 1.what is the difference between parasitism and mutualism? how do we...
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DNA – October 4, 2010
1. What is the difference between parasitism and mutualism? How do we represent those using symbols?
2. What’s the difference between species richness and relative abundance?
3. Community 1: 30A, 30BCommunity 2: 20A, 10B
What is the species richness for community 1 and community 2? What is the relative abundance?
Community Ecology: Trophic Structures
Ms. KlinkhachornOctober 4, 2010
AP Biology
Trophic Structure
• “troph” refers to feeding, nourishment• Feeding relationships within a community
• All energy that we consume can be traced back to the sun
Food Chains
Grass Mouse Hawk
• Show transfer of energy and nutrients up feeding levels (trophic levels)
• When drawing feeding relationships, arrow points toward the organism receiving the nutrients
Food Webs• Food web = visual organizer that represents
possible feeding relationships in a community– Linked food chains
• Give a more accurate picture of what is happening compared to food webs
• Show trophic levels
Bottom of the Food Web• Always start with producers• Then consumers– Primary– Secondary– Tertiary
Decomposers and Detrivores
• Top of the food web – prevention of waste buildup
• Detrivore = organism that eats dead organisms– Example: vulture
• Decomposer = breaks down dead organisms and returns nutrients to the soil– Example: bacteria
Food Web Limits
• Typically no more than 5 links in the chain• 2 Theories– Energy is not transferred efficiently (you lose
energy as you go up the levels)• Energetic hypothesis
– Long food chains aren’t very stable due to population fluctuations• Dynamic stability hypothesis
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