What are some characteristics of life?

1. What are some characteristics of life?

2. What are some characteristics of life? • Breathing • Eating • Moving • Reproducing • Contains cells Which of these is different from an automobile?

3. What is life? • Life is organized units of chemical reactions in a state of equilibrium (homeostasis). • All chemical reactions involve the transfer of energy (usually in the form of heat).

4. Thermodynamics The study of the transfer of energy. Types of energy: • Kinetic- energy of objects in motion • Potential- energy stored in objects

5. Examples of Energy • Rolling rock (kinetic) • Rock sitting at the top of a cliff (potential) • Waterfall (kinetic) • Air temperature (kinetic) • A can of gasoline (potential) • An apple (potential) • A molecule of water vapor (potential and kinetic)

6. Not all energy is useful to life. • Chemical energy stored in the bonds of certain compounds is most useful (ATP). • Dissipated heat like that in the air or water or that radiating off your arms as we speak is least useful.

7. Life is maintained by converting potential energy stored in chemical bonds into kinetic energy involved in life’s actions.

8. Laws of Thermodynamics • First Law: Energy is neither created nor destroyed in the context of a system. • Energy can change forms but the sum of all energy of a system remains the same. • The same is also true for matter. • Second law: In any transfer of energy, some energy dissipates and becomes unusable. • There is always less useful energy at the end of a process than at the beginning. • Systems tend to go from a state of order to a state of disorder.

9. Energy flow through the ecosystem • What form does energy take in the ecosystem?

10. Energy flow through the ecosystem

11. Photosynthesis 6C02 + 6H20 + sun  6O2 + C6H12O6 • Carbon fixation • Occurs in green plants • Glucose is the basic form of food used by most cells

12. Respiration 6O2 + C6H12O6  6C02 + 6H20 + energy • Reverse of Photosynthesis • Equivalent to burning • Converts stored energy in glucose into usable energy for life’s activities. • Occurs in practically all living things.

13. (Autotrophs) (Heterotrophs) The food chain-A linear transfer of food (energy) from one organism to the next.Trophic levels- major categories of feeding groups in a food chain.

14. Trophic Levels • Producers- Capture solar energy into chemical energy. Also called autotrophs (produce food). • Consumers- Unable to convert solar energy into food, they must capture and consume already produced food. (heterotrophs). • Primary Consumers- Consume food produced by producers. (Herbivores, omnivores) • Secondary Consumers- Consume primary consumers (Insectivores, omnivores, predators) • Tertiary consumers- Consume secondary consumers (carnivores, omnivores). • Decomposers- breakdown tissue of dead to make it useful again for plants.

15. Interconnected Food Chains make up a food web.

16. Keystone Species • Species that contribute disproportionately more to the balance and structure of a ecosystem. • Example: top predator that control populations of their prey, which in turn influence other organisms.

17. Trophic Triangle Observation: There are fewer consumers than producers and fewer higher level consumers than low level consumers.

18. Trophic pyramids: Examples Source: Silver Spring marine ecosystem Pyramid of numbers (# of individuals/area) Pyramid of Biomass (grams/area) Pyramid of energy (kcal/area/time) Originally introduced by C. Elton

19. There are fewer consumers than producers. Why? Laws of Energy (thermodynamics): • Second Law- Some energy is always lost as it is transferred (usually in the form of heat). • less available energy means fewer organisms can be sustained as energy is transferred from one trophic level to the next.

20. Where does the Lost Energy Go? • Not all food is captured and eaten by organisms belonging to the next trophic level, the rest eventual dies and decomposes. • Some food cannot be digested and exits as waste. (this is food from which no energy was extracted) • Only 10% of digested food becomes part of an organism's body tissue; the rest is used to maintain life (respiration, movement, digestion, heat production, etc).

21. Quantified Energy Flow through the Food Chain

22. Summary of Energy Flow

23. Biochemical Cycles Biomass Production (Carbon fixation) • The carbon cycle: • Carbon sinks are large storages of biomass (carbon based chemicals). • Carbon dioxide is the earth’s major greenhouse gas. Photosynthesis Atmospheric carbon: CO2 Biomass Utilization (respiration, burning, combustion)

24. Biochemical Cycles • Nitrogen Cycle- Nitrogen is a major element of protein (building blocks of life) • 78% of earths atmosphere is N2 (nitrogen gas). • N2 is very stable and non-reactive, thus unusable by most organisms. • Nitrogen fixation by bacteria converts it into a usable form (NH3 and NO2 and NO3) • Legume plants (peas, soybean) have a symbiotic relationship with nitrogen fixing bacteria in their root.

25. Nitrogen Cycle • Most of the fixed nitrogen simply cycles through the food chain. • Only a small degree of nitrogen fixation occurs naturally. • Equally a small degree of nitrogen is denitrified back into Nitrogen gas.

26. Nitrogen Cycle (continued) • During the past century we have doubled the amount of fixed nitrogen mostly in the form of fertilizer, creating a huge in-balance in the cycle. • Eutrophication- Rapid aging of lakes and ponds. Caused by fertilizer runoff that stimulated dense vegetative growth (faster than can be grazed), that can eventually choke the lake to death.

27. Thought Questions • The second law of Thermodynamics basically says that systems tend to move toward a state of disorder, yet life itself is a state of high organization. Does this mean that life is doomed to eventually end? Moreover, how could have life began in the first place? • We rarely see food chains with more than 3 links (i.e. Having quaternary consumers). Why do you think this is so?

28. Thought Questions • Since most of the energy is lost from one trophic level to the next does this mean you will gain more energy eating food that belongs to the lowest trophic level (i.e. vegetation)? • In some communities such as marine systems, ecologists find that there is much more biomass at any given moment in the consumer trophic levels than at the producer trophic level. This pattern seems to contradict conventional understanding of energy dynamics in an ecosystem. What is going on in these systems? Doesn’t this violate our understanding of energy flow through the system?

29. Thought Questions (cont.) • Many environmentalist favor increased consumption of vegetarian food instead of meat. Part of their argument is that doing so saves land. How is this possible? Doesn’t a chicken take up less space than a field of corn?? Can we trust those wacky tree huggers? • Certain pesticides like DDT will build up in the tissue of organisms. Scientists have found that top level predators tend to be particularly vulnerable to subsequent poisoning, explain how this is so given our understanding of food webs and and energy flow through trophic levels. • Scientist have recently discovered an ecosystem found at the bottom of the ocean that utilizes heat energy from thermal vents to drive food chains. What impact might this discovery have on the prospects of life beyond earth?

30. The average cost of rehabilitating a seal after the Exxon Valdez oil spill in Alaska was $80,000. At a special ceremony, two of the most expensively saved animals were released back into the wild amid cheers and applause from onlookers. A minute later, in full view, a killer whale ate them both.