This view is a variation of the gaia hypothesis

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This view is a variation of the Gaia Hypothesis Original version (aka Strong Gaia Hypothesis ): Earth is like a living organism Animals and plants maintain homeostasis in the atmosphere by adjusting rates of respiration and photosynthesis, like organs in a body. Ensures conditions remain conducive to life Controversial Newer version (aka Weak Gaia Hypothesis ) Life “coevolves” with the atmosphere; changes in one can trigger changes in the other. No actual homeostasis; life does not actively maintain atmospheric conditions that are conducive to life. More widely accepted
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The nitrogen cycle Atmosphere an important compartment Human impact: Fertilizers Internal combustion engines (release N 2 O, NO, NO 2 )
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The phosphorus cycle Lithosphere important; little atmospheric involvement Human impact: fertilizers; waste
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Both atmosphere and lithosphere are important Human impact: fossil fuel burning --> acid rain The sulfur cycle
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REEF question What is Simpson’s index of diversity for the community shown below? (Recall, D is the probability of picking 2 individuals at random that are of the same species) Species # ind’ls A 30 B 20 C 20 D 10 E 10 F 10 a) 0.2 b) 0.5 c) 0.8 d) 1.25 e) 5.0 Answer below
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