1. Your questions…your review

2. The Nitrogen Cycle  78% of the troposphere is composed of nitrogen gas.  Nitrogen is an important element for the making of proteins, nucleic acids, and vitamins.

3. Processes convert nitrogen gas into compounds that can be used in the food webs:  Atmospheric electrical discharge makes nitrogen and oxygen gases react to form nitrogen oxide.  Specialized bacteria fix nitrogen gas into ammonia to be used by plants (nitrogen fixation).  Ammonia not used by plants may go through nitrification to form nitrite ions (toxic to plants) and nitrate ions (easily taken up by plants).

4. After nitrogen fixation and nitrification…  Plant roots absorb these dissolved substances called assimilation and use them to form DNA and proteins. Animals consume nitrogen through plants or plant-eating animals.  In ammonification, decomposer bacteria convert waste into simpler nitrogen-containing compounds such as ammonia and water-soluble salts containing ammonium ions.  Nitrogen returns to the atmosphere through denitrification by converting ammonia and ammonium ions into nitrite and nitrate ions and then into nitrogen gas and nitrous oxide gas.  This begins the cycle again.

5. Layers of the Atmosphere  Composed of different layers with different temperatures, pressures, and compositions. Fig. 17-2 p. 419

6. Soil  Particle Size

7. Soil  Difference between porosity and permeability

8. Soil  Soil horizons: series of layers with distinctive textures and compositions

9. Matter and Energy  Law of Conservation of Matter: we cannot create or destroy atoms only rearrange them into different spatial patterns (physical changes) or different combinations (chemical changes).  Matter is essential a closed system on Earth  We will eventually run out of matter.  There is “no away”  We have to deal with pollutants(degradable, biodegradable, slowly degradable, and nondegradable).  Matter can be recycled.

10. Matter and Energy  First Law of Thermodynamics/Conservation of Energy: in all physical and chemical changes, energy is neither created nor destroyed, but it may be converted from one form to another.  Energy input = energy output.  We can’t get something for nothing in terms of energy quantity.  Energy can be converted into different forms

11. Matter and Energy  Second Law of Thermodynamics: when energy is changed from one form to another, some of the useful energy is always degraded to lower quality, more dispersed, less useful energy.  Energy conversions result in lower quality energy that flows into the environment.  Energy cannot be recycled – there is a one-way flow of it.

12. Matter and Energy: How does this apply to living systems?  There is a one-way flow of high quality energy through materials and living things which is dispersed eventually as low-quality energy (heat).  Since matter is a closed system, it must be recycled (think chemical cycles).  Food chains indicate how energy flows through a sequence of organisms while a food web demonstrates the complex network of connecting food chains.  Pyramid of energy flow shows that there is a decrease in the amount of energy available for each trophic level.  Assumes 10% of energy is available to next trophic level.  Limits number of trophic levels.  Makes top carnivores the most vulnerable.

13. Matter and Energy: How does this apply to living systems?

14. Productivity  Gross primary productivity (GPP) is the rate at which producers convert solar energy into chemical energy as biomass.  Net primary productivity (NPP) is the amount of energy stored in organic molecules after respiration loss is factored. NPP = GPP – RL (respiration loss)  The planet’s NPP ultimately limits the number of consumers (including humans) that survive on Earth.

15. Productivity

16. Freshwater Lakes

17. Oligotrophic Lakes Fig. 7-21 p. 158

18. Eutrophic Lakes Fig. 7-21 p. 158

19. Speciation  Speciation: when two species arise from one where they can no longer breed and have fertile offspring.  Allopatric Speciation occurs through geographic isolation or reproductive isolation.  Sympatric Speciation occurs through a mutation or behavior difference.

20. Population Density

21. J-Curves and S-Curves  Exponential growth: occurs when resources are not limiting and a population can grow near intrinsic rate of increase or biotic potential.  Logistic growth: rapid exponential growth followed by a steady decrease in growth with time until population size stabilizes at carrying capacity (K). Also see Figure 9-4 on page 166

22. J-Curves and S-Curves

23. Natural Population Curves

24. r-Selected vs. K-Selected Species Fig. 9-10 p. 196

25. Survivorship Curves Fig. 9-11 p. 198

26. Age Structure Diagrams

27. Demographic Transitions