1. What adaptation allows CAM plants to live successfully in desert environments? 1.their roots are extensive but shallow, allowing any rainfall to quickly collect 2.their stomata are permeable to CO 2 and O 2 but not water, allowing water to be retained while photosynthesis continues 3.they utilize a cyclic photosynthetic pathway exclusively and don't require water as an input for photosynthesis 4.they collect and store CO 2 at night, then release it during the day when light energy is available for photosynthesis 5.their thylakoid membranes are impermeable to water 12345

2. One product of the light-dependent reactions is NADPH; why is NADPH significant? 12345 1.it is a photosynthetic waste product designed to remove surplus hydrogen and energy-depleted electrons from the chloroplast 2.NADPH is a component of electron recycling; it passes an electron to one of the pigment molecules 3.NADPH donates electrons and hydrogen ions to carbohydrate synthesis during the light-independent phase of photosynthesis 4.the molecule dissociates to form free oxygen and NADP 5.NADPH donates hydrogen ions to the gradient forming in the thylakoid compartment

3. Englemann's studies of photosynthesis showed that Spirogyra used which colors of light most effectively? 1.violet and yellow 2.red and yellow 3.red and violet 4.blue and yellow 5.green and yellow 12345

4. How can the green color of most plant leaves be explained? 1.green light most effectively supports photosynthesis; it is absorbed and causes plants to appear green 2.excited pigment electrons emit green light when falling back to their unexcited energy states 3.the green wavelengths have the wrong energy characteristics for photosynthesis and green light is simply reflected from the plant's leaves 4.green light is transmitted by the leaf, explaining why both the top and bottom of the leaf appear green 5.plant leaves reflect both blue and yellow light; the combination of these colors appears green to the human eye 12345

5. What simple molecule, released during photosynthesis, changed both the atmosphere and the biochemistry of life on early Earth? 1.carbon dioxide, or CO 2 2.carbon monoxide, or CO 3.nitrogen, or N 2 4.ammonia, or NH 3 5.oxygen, or O 2 12345

6. When stomata are closed in a photosynthesizing plant leaf, the concentrations of CO 2 ________ and O 2 ________. 1.increase, increase 2.decrease, increase 3.decrease, decrease 4.increase, decrease 12345

7. During the fall, leaves often become red or yellow as ________. 1.new pigments are added to exploit the changing quality of light as the season changes 2.the chlorophylls break down and no longer mask the presence of other accessory pigments 3.pigments that once reflected the red and yellow wavelengths now absorb them 4.environmental cooling lowers the electron energies of various pigments 5.photosystems damaged by time permit excited electrons to fall back to their resting states, releasing their energy as red and yellow light 12345

8. The colors of light visible to the human eye correspond to ________. 1.variations in photon speed 2.the relative balance between light's particle-like and wave- like qualities 3.the wavelengths of the photons 4.the composition and mass of the photons 5.the angle the light strikes the human eye 12345

9. Carbon that is converted to carbohydrate in the light-independent pathways comes from ________. 1.carbon dioxide 2.glucose 3.starch 4.water 5.various organic compounds produced by autotrophs 12345

10. Biologists hypothesize that the C3 and C4 pathways ________. 1.evolved from the more primitive CAM pathway as plants adapted to live in habitats other than moist, swampy ones 2.developed in those aquatic plants that lack stomata 3.represent photosynthetic strategies that allowed primitive photoautotrophs to utilize habitats where light intensities are very low 4.evolved as a desert adaptation, since neither pathway requires water as a source of photosystem electrons 5.evolved at different times in response to differences in atmospheric composition 12345

11. Cacti display many adaptations for desert living, including ________. 1.stomata that open at night rather than during the day 2.thick surface layers that limit water loss 3.succulent leaves 4.the CAM pathway for carbon fixation 5.all of the choices 12345

12. Where do the light-independent reactions occur? 1.in the inner chloroplast membrane 2.in the thylakoid 3.in the outer chloroplast membrane 4.in the stroma 5.in the photosystem complex 12345

13. What statement best summarizes the balance between carbon fixation through photosynthesis and carbon release through human activity? 1.at the present rate of photosynthesis, the atmosphere will be depleted of CO 2 within one million years 2.photosynthesis currently removes less CO 2 than human activity releases, but inorganic processes remove the excess, resulting in stable atmospheric amounts 3.the total production of CO 2 is precisely balanced by photosynthesis 4.since photosynthesis is globally limited by the availability of CO 2, increases from human activity are quickly captured by plant growth 5.human activities release more CO 2 than photoautotrophs can fix; significant atmospheric changes are possible 12345

14. The electrons needed to replace those transferred from photosystem II are supplied by ________. 1.rubisco 2.photosystem I 3.NADPH 4.water 5.ATP synthase 12345

15. A variety of human activities, including ________, threatens to reduce the growth of marine photoautotrophs and disrupt marine food webs. 1.enrichment of marine waters with fertilizers 2.the introduction of raw sewage 3.the disposal of industrial wastes 4.the warming of surface waters 5.burning fossil fuels 6.all of the choices 12345

16. Earth's earliest photoautotrophs were anaerobic; how did they adapt to the increasing concentrations of oxygen created by advances in photosynthesis? 1.many were unable to adapt and simply perished in an early mass extinction event 2.some species evolved chemoautotrophic pathways and were able to occupy extreme habitats like sea-floor hydrothermal vents 3.the ancestors of most modern bacteria evolved metabolic pathways that could detoxify oxygen 4.some became restricted to anaerobic habitats such as swamps and sediments 5.all of the choices 12345

17. Photorespiration, which reduces sugar synthesis, occurs when ________. 1.plant tissues become anaerobic 2.oxygen concentrations rise above critical levels and begin reacting with ribulose bisphosphate 3.plants switch from the C3 to the C4 pathway 4.oxaloacetate is formed within the mesophyll cells 5.stomata open after extended periods of closure, allowing a temporary influx of oxygen 12345

18. What term is used to describe those organisms that can make their own food? 1.allotroph 2.autotroph 3.heterotroph 4.saprobe 5.chemotroph 12345

19. What statement best summarizes the light-dependent reaction? 1.carbon dioxide and water are combined to produce sugar and oxygen 2.ATP created in the Calvin-Benson cycle is used to synthesize carbohydrate 3.chlorophyll a oscillates between a reduced and oxidized form 4.light energy is converted to the chemical bond energy of ATP 5.light energy is used to assemble water molecules from atmospheric oxygen and NADPH 12345

20. The term carbon fixation is used to describe the ________. 1.conversion of organic compounds into fossilized rock 2.conversion of organic compounds into oil and oil- related products 3.incorporation of environmental carbon into stable, organic compounds 4.transfer of carbon from one organic compound to another 5.incorporation of organic remains to the sediments forming the ocean floor 12345