Biol-K 341 Ecology and Evolution Exam 1 Notes
Biol-K 341 Ecology and Evolution Exam 1 Notes BIOL-K 341
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This 16 page Bundle was uploaded by adamgschroeder13 on Tuesday September 13, 2016. The Bundle belongs to BIOL-K 341 at Indiana University Purdue University - Indianapolis taught by Dr. Xang in Fall 2016. Since its upload, it has received 7 views. For similar materials see Principles of Ecology & Evolution in Biology at Indiana University Purdue University - Indianapolis.
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Review Topics for Exam I – Principles of Ecology. Fall 2016 Ecology – Introduction 1. What is the origin of the term “ecology”? How do you define “ecology”? a. ‘Ecology’ Origin: a. Eco = Oikos (greek), means household/home b. First coined by German biologist Ernst Haeckel in 1869 b. Definition of ecology: No universally accepted definition. Could be “Study of the Structure and function of Nature” (according to Eugene P. Odum). 2. What does ecology study? a. Ecology is a biological discipline that studies many different things, ranging from bio to chem, physics, hydrology, math, etc. b. Ecology is a science of interactions. It studies the interactions of organism with their biotic (living) and abiotic (nonliving) environments c. Studies organisms at different organizational levels i. Organism lives in abiotic and biotic environment 1. Abiotic everything that’s nonliving (water, air, etc) 2. Biotic – everything that’s living 3. KNOW: An individual organism is the unit of natural selection. ii. Population – living things of the same species in one area 1. KNOW: A population is the unit of evolution. iii. Community – more than one population in one area iv. Ecosystem – exchange of materials and energy between a system and the outside v. Landscape: More than one ecosystem vi. Biosphere – the global scale of ecology 3. What are the contributions to ecology by some of scientists mentioned in class? a. Carl Ludwig Willdenow (17651812) and Heinrich Alexander von Humboldt (17691859) i. Pointed out that regions of the world with similar climates support vegetation similar in form ii. Concluded that the form and function of plants within a region reflects constraints imposed by the physical environment. In other words, climate bring about the distribution of plants, it is the most important factor. b. Johannes Warming (18411924) i. Studied tropical forests in Brazil ii. Wrote first textbook on plant ecology (Plantesamfund) (lots of influence on early ecology) c. Christensen Raunkiaer i. Classified plants in a unique way d. Charles Darwin i. Came up with natural selection and evolution, author of the “Origin of Species” e. Gregor Mendel (18221884) 1 i. Studied in his garden the transmission of characteristics from one generation of pea plants to another. Father of genetics. ii. Darwin and Mendel’s theories came together to provide the mechanisms for understanding the link between organism and their environment – the focus of ecology. f. Henry C. Cowles: i. Studied succession of plants on the Indiana sand dunes (Lake Michigan) in 1897 ii. Established plant succession as a central concept of modern ecology; the idea that there is a succession of plants replaced over and over again over time. iii. Studied Warming’s first textbook on ecology g. Rachel Carson i. Wrote Silent Spring (1962), one of the 50 most influential books ever. ii. Brought environmental problems to the attention of the public iii. Showed that chemical poisons and pollutants are recycled throughout the environment iv. Led to the ban of DDT in the US v. Also led to the creation of the EPA in the US h. Eugene P. Odum (19132002) i. Father of modern ecology ii. Established the Odum school of Ecology at the University of Georgia Abiotic Environments 1. Fate of the incoming solar radiation. a. Solar Radiation i. Essential for all life forms on earth ii. Takes 8 minutes for radiation to travel from sun to earth’s atmosphere 1. “Weakened” by the time it reaches earth 2. Incoming radiation = Some of it is reflected by the atmosphere, some is absorbed by atmosphere. 3. 51% actually makes its way to the surface of the earth. From there, different things happen, but realize that energy stays constant. iii. Of the solar radiation that gets to earth’s atmosphere, about 50% is absorbed by surface of the earth iv. Light that reaches the surface: 1. Can hit different surfaces: snow, ice, trees, bodies, grasses, water 2. What is albedo? a. ALBEDO –how much light is reflected back off the surface of an object once light hits it i. The fraction of incident radiation that is reflected by a surface or body ii. For direct light (light that strikes at a 90 degree angle), the albedo for the following systems: 1. Water surface = 2%, most light will go right through water at a 90 degree angle. a. If light hits at another angle, albedo is bigger (more reflection) 2. Forests = 530% depending on its canopy closure, the thicker the forest the lower the albedo 2 a. Waxy leaves reflect more sunlight back into space. 3. Snow and ice = 4590% = HIGH ALBEDO a. Asians have thicker eyelids than Europeans because Asian ancestors were in snow more. 3. Know the relationship among vapor pressure, saturation vapor pressure, vapor pressure deficit and dew point temperature, i.e., the relationship graph between temperature and saturated vapor pressure. a. Climate i. Weather is a short term description (1 day to 1 week); climate is a long term idea. b. Relative Humidity –water content in the air is defined in terms of vapor pressure (unit: megapascal or Mpa) i. Vapor pressure amount of pressure water vapor exerts independent of dry air. In other words, the pressure that a given concentration of water molecules exerts in the atmosphere. ii. Saturation VP –the pressure that water vapor exerts when the air is moisture saturated (can hold no more water) 1. If you add water to something that is saturated, the water will condense. iii. VP deficit = saturation VP – Current VP iv. Dew point temperature –the temp at which saturation VP is achieved for a given water content of the air 1. If you decrease the temp, the air’s moisture capacity is decreased 2. Curve below –saturation VP as a function of air temp 3. When temp increases, VP increases as well, since atmosphere can hold more water at higher temperatures. v. How to calculate Rel. Humidity = current VP/Saturation VP x 100 1. So, if you decrease temperature, relative humidity goes up, since the saturation VP curve goes down as temperature goes down. If you decrease the denominator, you increase the relative humidity overall. vi. Current temp is greater than or equal to dewpoint temp (so dewpoint temperature is ALWAYS lower than or equal to current temperature) vii. Difference between dew point and current temp is large = drier air; small difference = wetter air. When dew point temperature equals current temperature, relative humidity is 100%. viii. When these two temperatures are the same it is uncomfortable, too much water, rain. ix. Same relative humidity, different temperature, which air has more moisture? 1. – high temperature. more moisture air is able to hold 3 4. What are the characteristics of El Nino and La Nina? What are their effects? You should be able to tell El Nino and La Nina events from either an SST or SST anomaly graph. a. EL NINO: i. American side of Pacific Ocean is the east side, Asian side is west side. ii. Normal Year West Pacific (Asia) is warmer than East (South America) 1. The atmosphere above the eastern South Pacific Ocean is dominated by a persistent high pressure zone, while a low pressure zone dominates the west. 2. This difference in pressures drives the trade winds from east to west along the equator 3. At the same time, high above the ocean surface, this wind circulation is completed as it blows from west to east. This is known as the WALKER CIRCULATION 4. Wind blows from high pressure to low pressure (east to west in normal year) 5. Moisture over western part rises and goes to east 6. Water Temperature is warmer in the west than east a. Trade winds pile up warm surface water in the west Pacific: i. Sea surface is about ½ meter higher at Indonesia than at Ecuador ii. Sea surface temperature is about 8 degrees Celsius in the west than in South America, due to an UPWELLING of cold water from deeper levels iii. What is El Nino? During an El Nino year, West Pacific (Asia) is colder than East (S. America) 1. A disruption of the normal ocean atmosphere system in the tropical pacific ocean 2. Originally recognized by the fishermen off the coast of south America as unusually warm water in the pacific 3. El Nino means ‘little boy’ or ‘Christ child’ which was used for the tendency of the phenomenon to occur around Christmas 4. Called “warm event”. 5. Happens every 47 years. iv. How does El Nino happen? 1. Trade winds relax in the central and western pacific leading to a depression of the thermocline in the eastern pacific and an elevation of the thermocline in the west. 4 2. Southern Oscillation (SO) happens during El Nina: A seesaw of air pressures on the eastern and western halves of the pacific 3. The result is a rise in sea surface temp and a drastic decline in primary productivity in eastern pacific. This is due to the fact that no upwelling occurs in the East in an El Nino year. Normally, upwelling happens when the cold deep water (Nutrientrich) comes to the surface of the Eastern Pacific Ocean (S. America area) to replace the surface water that is being blown westward. So, normally, Eastern Pacific has colder surface water that is nutrient rich. In an El Nino year, upwelling doesn’t happen, and nutrient rich water doesn’t come to the surface, so productivity decreases and lots of animals, fish, and plankton die. Plankton (zooplankton and phytoplankton) are at the bottom of the ocean food chain, so when they die, fish die, and when fish die, birds die (they starve). v. ENSO Index (El Nino Southern Oscillation) 1. Indicates long term trends of El Nino events 2. El Nino is sometimes followed by La Nina. 3. El Nino seems to happen more frequently and stronger now than in the past. vi. Possible causes of El Nino 1. Underwater earthquakes on the ocean floor a. Disrupts the normal ocean system 2. The pacific tries to respond on an annual time scale with the sun, but it cannot because it’s too wide. This causes anomalies like El Nino. a. Trying to warm up 3. No one knows the exact cause of the phenomenon, but we know it is caused by more than one factor vii. Consequences of El Nino 1. Causes excessive moisture across the southern tier of the US and in Peru (leads to destructive flooding) 2. Galapagos Islands (western S. America) had vegetation growth during their normal dry season because of too much rainfall in an El Nino year. 3. Western coast of the pacific ocean is very dry a. Drought in the west pacific and brush fires in Australia 4. The suppression of upwelling of nutrient rich cold water in the eastern pacific leads to decline in fishery and bird populations on the coast of Americas in El Nino years. a. 85% of the sea birds in Peru were killed in the 19821983 El Nino event. 5. Effect can be felt as far away as Antarctica a. The number of weddell seal births declines every four to seven years, coinciding with El Nino, probably caused by fish decline during El Nino years. 6. Reduce corn harvest in East Africa (southeast) because of dryness. Dryness = less rainfall = lest harvest of crops. b. LA NINA: i. What is it? 1. Refers to a period when ocean temperatures across the central and eastern tropical Pacific Ocean are cooler than normal. 2. Occurs after some but not all El Nino years. 3. La Nina means little girl. Called “anti El Nino”, cold event, or cold episode ii. During a La Nina year, blue color extends farther to the center of SST graph. iii. Effects of La Nina 5 1. Americas are very dry, Australia and SE Asia are very wet, and SE Africa is very wet. iv. Consequences 1. Warm winters in the SE US, colder than normal winters from the Great Lakes to the pacific northwest 2. The 1988 La Nina has been tied (inconclusively) to Bangladesh floods and Midwest US droughts v. ENSO Index 1. Trend of La Nina shows that La Nina has decreased in strength and become less frequent in recent years. SST Anomaly Graphs on Right Top = Normal Year Middle = El Nino Bottom = La Nina 5. What are some greenhouse gases? Which ones are the most important? How does the greenhouse effect happen? (Combined two of his questions into one) a) Greenhouse gases to know a. CO 2 b. Methane (CH ) 4 c. Chlorofluorocarbons (CFC) d. Nitrous Oxide (N 02 b) What is the most important greenhouse gas on Earth? Trick Question on Exam. Answer: H 0 an2 CO 2 a. Water vapor – the most important; it contributes to ¾ of the greenhouse effect. (Water vapor is what makes clouds in the atmosphere, and they contribute big time to greenhouse effect) b. CO 2The most important humanmade (anthropogenic) greenhouse gas i. It contributes to ½ of the humanmade greenhouse effect c) The Greenhouse Effect – What is it and how does it happen? 6 a. What is it? i. The trapping of solar energy in the atmosphere by greenhouse gases. ii. Leads to higher temperature on the surface of the earth and in the lower atmosphere. iii. It is essential for life on earth, since it keeps the earth’s average surface temp at about 15º C iv. Without greenhouse gases, the planet’s temp would be 18º C, too cold for most life on earth. v. Venus has a thick atmosphere and too much greenhouse effect, so its temp. is too hot vi. Mars is the opposite: it has a thin atmosphere that leads to temperatures that are too cold for life b. The “greenhouse effect” that people talk about in the media refers to the anthropogenic greenhouse effect (human made, CO ), 2hich might have adverse effects on life on Earth: GLOBAL WARMING i. Rise in global mean temperature, Melting of ice caps, and Flooding of lowlying areas 6. What is PAR? What is its range of wavelength? a. PAR = photosynthetically active radiation (i.e. light that plants can use to do photosynthesis) b. Units (KNOW THIS): (photon) c. The wavelength range for PAR is that of visible light (400 – 700 nm), since plants can only utilize visible light 7. What are the most important photosynthetic pigments? Differences between chlorophyll a & b? a. There are two important groups of photosynthetic pigments: chlorophylls and carotenoids i. Chlorophylls are the most important to plants. b. Two types of chlorophylls: Chlorophyll a and chlorophyll b i. Chlorophyll a 1. Peak 1: Optimum PAR at ~450 nm 2. Peak 2: Optimum PAR at ~680 nm (Higher than b) 3. Does not function at a larger range of the visible spectrum when compared to chlorophyll b ii. Chlorophyll b 1. Peak 1: Optimum PAR at ~510 nm (Higher than a) 2. Peak 2: Optimum PAR at ~610 nm 3. Functions better than chlorophyll a 4. Does not function at a shorter range of visible spectrum when compared to chlorophyll a iii. Both chlorophyll a and chlorophyll b don’t absorb at 550 nm at all (green wavelength); they reflect 550 nm light, and that’s why plants look green. 8. What is LAI? How do you calculate LAI? Which forest has a more dense canopy, one with an LAI of 3, or one with an LAI of 5? 2 2 a) LAI = Leaf Area Index = total leaf area (m )/ground area (m ) a. A dimensionless measure of the amount of leaf cover b. An LAI of 4: i. A given area of ground would be covered by 4 times that area of leaves. c. Example: a forest covers a circular area has three canopies: top, middle, and low i. Top canopy 58 m , middle 48 m , low 38 m , so total leaf area = 144 m 2 ii. Ground area must be known to calculate radius of circle 5.64 m 7 1. Area = 100 m 2 iii. 144/100 = 1.44 = LAI d. A canopy with LAI of 5 is more dense than a canopy of LAI of 3 b) Forest a. At the top, 100% light hits the canopy, but as the light makes its way down, it gets less and less intense, and at the bottom, the light is much less than at first (most has been blocked by leaves) 9. What is the law that can be used to describe light attenuation within a forest canopy or in an aquatic environment such as a lake? kLAI a) LambertBeer’s Extinction Law Beer’s Law: I =I e z 0 a. I z–light reaching any vertical position z in the canopy b. I o–radiation incident at the top of canopy c. LAI –cumulative leaf area index above z d. K –light extinction coefficient (will be given on exam) e. At the top of the canopy Io = Iz b) Can also be applied to an aquatic environment a. Iz = Ioe kz i. Io light intensity at the surface ii. Iz –light intensity at depth z iii. K –light extinction (attenuation) coefficient c) Examples: Calculating stuff from Beer’s Law a. K =0.45, what is LAI at a point in the canopy where the light is half of the intensity at the canopy top? i. 0.5 = e 0.45 ln(.5) = lne x .45(LAI) ln(.5) = .45LAI LAI = ln(.5)/.45 =1.54 b. What is the percentage of light that reaches a forest floor if LAI=0? Answer = 100% c. A forest has an LAI of 3 and has 1/2 of light reaching the forest floor. If the LAI increases to 4, what is the percentage of light that reaches the forest floor? Answer = about 39.7% 10. What are some key characteristics of water? How does a hydrogen bond form? a) Characteristics of Water i. High Specific Heat ii. High Surface Tension iii. Adhesion/Cohesion/Capillarity iv. Water is essential for life on Earth v. Earth’s surface is approximately 70% ocean a) Approx 75% of Earth’s fresh water is in glaciers and ice sheets a. 1/5 is in the Great Lakes b) Water molecules are linked to each other by hydrogen bonds. a. In each water moleuclue, the oxygen atom attracts more than its fair share of electrons. This results in a partial negative charge on oxygen and slight positive charge on hydrogen atoms. b. Hbonding is important in maintaining structural integrity of DNA and proteins c) Water exists to a great extent in the soil. So how does water move from soil up canopy of a tree? a. Hydrogen bonds, evaporation creates a gradient to pull water from soil through trunk and up into leaves, and out into atmosphere = TRANSPIRATION. Transpiration happens through the leaves. b. At the same time, gravity tries to pull water down. There’s a height limit on how tall a tree can grow because gravity would overcome evaporating force and tree would not get water. 8 11. What is a soil profile and what is a soil horizon? a. Soil consists of: i. Solids 1. Most important solids are Sand, Silt, and Clay (Size wise: Sand>Silt>Clay) ii. Liquids water iii. Gases –carbon dioxide, methane b. Soil Profile –vertical cut through a body of soil. Each ‘soil horizon’ is a distinct layer of soil i. A horizon –uppermost layer, surface soil. darkest part. Has organic materials. Has roots of plants, has lots of small bugs/organisms. ii. B horizon –middle layer, has some minerals, not as much organic material as A layer. iii. C horizon –lightest in color, not much biological activity happens here. Has rocks, so it isn’t too affected by weathering over time. 12. What are the five major factors in soils formation? Parent material –the unconsolidated mass on which soil formation takes place (main factor in soil formation) Climate –radiant energy and water in different areas leads to different type of soil. Ex. Soil in Florida is different than that of Indiana. Topography –affect soil development through its effect on climate o Soil on the top of a mountain vs. soil found in the valley Soil in valley is richer, thicker than that in a mountain Biota –vegetation, animals, bacteria, and fungi o Types of soil determines what types of plants can grow there o Types of plants growing will also alter the soil characteristics. o So both affect each other. Time –formation of soil requires time. o Young soil is usually more fertile than old soil 13. What are the most important soil orders in the Midwest? Answer: Mollisol and Alfisol a) There are 12 soil orders worldwide: Just know two of them: a. Mollisol –well developed soils high in organic matter and calcium (base), very productive i. Has dark brown – black surface horizon color ii. Prone to calcification (calcium rich) iii. Along with Alfisol, most important in the Midwest (includes Indiana) and rest of the country iv. Both are found in the Midwest –most productive area of country “breadbasket of the US” b. Alfisol –moist, moderately weathered mineral soils. Not as productive as mollisol, but still productive. Has welldeveloped horizons. i. Corn and soybeans 14. What is the Law of the Minimum? Who developed this law? A little background info: Essential elements for plants and animals a. Constituent Elements –basic constituents of all organic matter i. Carbon, oxygen, hydrogen b. Macronutrients – (Macro implies that these elements are needed in high numbers) i. Nitrogen, phosphorus, potassium c. Micronutrients –only needed in small, trace quantities i. Calcium, iron, manganese, boron, cobalt, copper, molybdenum, zinc, iodine d. Fertilizers 9 i. Percentages of nitrogen, phosphorus (phosphate P O )2a5d potassium (potash K O) a2e usually written on fertilizer bags. Fertilizers can have calcium and iron as well. e. So, what is the Law of the Minimum? i. If one nutrient is deficient, the plant growth will be limited even if the supply of all other essential elements is adequate. ii. The most important nutrient is the one in limited supply (will be exam question) f. Who developed the Law of the Minimum? Justus von Liebig i. German chemist, Father of agricultural chemistry and the fertilizer industry 15. Have some idea about soil pH in the north (e.g., Minnesota) and in the south (e.g., Florida). Why do soils in the north and the south differ in pH and in color? pH = negative log of hydrogen ion concentration. o Example: in a solution with hydrogen ion concentration of 10 mol/L 4 pH = log (10 ) = (4) = pH of 4 Most soils have a pH of 310 Soils in south are usually acidic, o Soil is brown or red color (oxides of iron or magnesium lead to this color) o Accumulation of Aluminum in the soil causes acidity Higher temperature leads to higher precipitation, which washes away potassium and calcium and allows aluminum to accumulate, leading to high acidity) 3+ 2+ + o Al + H 2 Al(0H) + H Soils in the north are usually basic o Soil is darker color (higher concentration of organic matter/dead plant and animal materials leads to this color) o Forms calcium carbonate and calcium hydroxide, these bases lead to a basic pH (accumulation of calcium) 2CaCO +32H O 2 Ca(HCO ) + Ca3 2) 2 Adaptation 1. What is the definition of adaptation? a. Any heritable behavior, morphological, or physiological trait that maintains or increases the fitness of an organism under a given set of environmental conditions i. Ex. If one animal is adapted to low temperature, it will not do well in hot temperature. ii. Ex. Plants grown at higher elevations will be shorter than plants grown at lower elevation. 2. What are autotrophs and heterotrophs? What are some examples of each group? a. Autotrophs (primary producers): organisms that produce organic material from inorganic chemicals and some source of energy i. Examples: plants, algae, trees, etc. b. Heterotrophs (secondary producers): Organisms that are unable to manufacture their own food from inorganic materials and thus rely on other organisms, living and dead, as a source of energy and nutrients i. Examples: animals, fungi, most bacteria, etc. 3. What is transpiration? What do some plants do to reduce the amount of water lost through transpiration during midday? 10 a. Transpiration: Loss of water vapor from a plant to the outside atmosphere (happens through stomata) b. Water goes up through Xylem (one of vascular tissue types) c. Plants close their stomata to prevent water lost during the hottest part of the day (about 2:30), and this causes a temporary decrease in photosynthetic rate, since CO2 isn’t coming in. So there is a tradeoff between H20 leaving, and CO2 coming in. 4. Be able to describe how water moves from soil to the leaves and to the atmosphere. a. Process is driven by transpiration and by a water potential gradient in which the atmosphere has a low water potential and the soil has a high water potential b. Adding salt to soil will drastically reduce water potential of the soil, will stop it from going up into roots and leaves of tree 5. What is photosynthesis? What are the roles of CO , H O,2and2chlorophylls in photosynthesis? a. Photosynthesis: Use of light energy by plants to convert carbon dioxide and water into simple sugars i. Chlorophyll is a pigment that functions to capture light energy in thylakoid discs and use it to convert carbon dioxide and water into simple sugars 6. What are light and dark reactions and where do they happen in a plant cell? What are the major steps in light and dark reactions? a. Photosynthesis takes place in two steps i. Light reactions –happens in thylakoids of grana in the chloroplasts 1. Photolysis takes place on the inside of the thylakoid membrane. Photolysis is the splitting of water molecules into hydrogen ions, electrons, and oxygen gas 2. Energy storing molecules ATP are created 3. NADPH is produced from NADP and H+ 4. ATP and NADPH are important, since they are used in the dark reactions ii. Dark reactions (Calvin Cycle) –happens in stroma of chloroplasts 1. Six molecules of carbon dioxide combine with 6 molecules of ribulose 1,5 bisphosphate (RuBP, which has 5 carbons) a. This forms 6 6carbon unstable complexes (so a total of 36 carbons) 2. Each 6carbon complex is then split into two 3carbon molecules (3PGA), results in 12 total 3. Each 3PGA is converted to one molecule of G3P (So now we have 12 3C complexes =36 carbon atoms total, just like before. Carbon is conserved.) 4. Ten of the 12 G3P molecules are restructured and become RuBP (30 Carbon atoms) 5. So, in the end, there is a net gain of 2 G3P molecules (6 carbons total) become sugars for plant growth a. One molecule of glucose (6 carbons in one molecule of glucose) is produced 6. Rubisco –the enzyme that catalyzes the first step in the Calvin cycle is ribulose 1,5 bisphosphate carboxylaseoxygenase (Rubisco) a. The most abundant protein on Earth, and the most important enzyme on earth b. Can catalyze two types of rxns –carboxylase and oxygenase 11 Diagram showing Light (Left side) and Dark (right side) steps of photosynthesis 7. What are the major differences between C , C and CAM plants? What do 3PGA and OAA stand for? 3 4 a. C3, C4 and CAM plants iii. C3 plants –The plants that produce 3carbon (3PGA – 3phosphoglyceraldehyde) during the initial steps of dark reactions 1. C3 plants have a thick palisade 2. The 3Carbon Pathway a. 6CO a2d 6RuBP 6RuBP and 1 molecule of glucose iv. C4 plants –The plants that produce 4carbon oxaloacetic acid (OAA) instead of 3PGA. 1. Very developed bundle sheath cells –Krantz Anatomy (which is not found in C3 plants) 2. Not much difference between palisade and mesophyll 3. The 4Carbon Pathway a. (phosphoenolpyruvate) PEP + CO2 OAA i. Enzyme: PEP carboxylase in mesophyll cells of plants that surround the Krantz structure. b. OAA is converted to malic acid, aspartic acid or other acids depending on the species of the plant c. Malic acid migrates into the bundle sheath cells where it is converted to pyruvic acid (3 carbons) and carbon dioxide. i. Malic acid acts as a carrier, from one leaf to another. Then it gets decarboxylated. d. Pyruvic acid returns to mesophyll cells to form more PEP. Carbon dioxide returns to the Calvin Cycle. e. C4 pathway = CO concentration + Calvin Cycle 2 v. CAM Plants – (Crassulacean Acid Metabolism photosynthesis) 1. 4carbon OAA is produced from PEP and CO2 during dark reactions at night. (same as C4 plant, but this step occurs at night in CAM plants) a. Enzyme: PEP carboxylase 2. OAA –converted to malic acid and stored in vacuoles. 12 3. During daytime, malic acid diffuses out of vacuoles, then is converted into pyruvic acid and CO2 (inside chloroplasts). a. Enzyme: rubisco 4. CO2 enters the Calvin Cycle, pyruvic acid goes back to first step to produce more CO2 5. Enzymes are in the same cell but are active at different times of the day. vi. C4 and CAM plants have additional steps before CO2 enters the C3 pathway. All three pathways contain the Calvin Cycle. 1. The plants that have C3 pathway only are called C3 plants. 8. What are the adaptive advantages of each photosynthetic pathway? Know some examples of classic C , 3 C 4and CAM plants. 1. C3 Plants advantages: a. More efficient that C4 and CAM plants under cool and moist conditions and under normal light b. Requires fewer enzymes and no specialized anatomy (Remember, Krantz is required in C4) c. Most plants are C3 plants. Ex: maple, oak, wheat. i. Its safe to say all trees are C3 plants. d. Bad thing? C3 plants have poor water use efficiency (WUE) i. WUE how efficient a plant can make carbohydrates using 1 unit of water –the amount of CO that 2 can be fixed per unit of water lost through the stomata ii. WUE of C3 plants? 1000 volumes of water lost per vol of CO fixed (i2e. LOTS of water lost) 2. C4 plants advantages: e. Photosynthesize faster than C3 plants under high light intensity and high temperatures because the carbon dioxide is delivered directly to rubisco, not allowing rubisco to react with oxygen and undergo photorespiration. f. Have better WUE than C3, because PEP carboxylase (enzyme) brings in CO faster and do2s not need to keep stomata open as much, so less water is lost than in C3. g. WUE of C4 plants: 300 vol of water lost per vol of CO fixed 2 h. Get their CO fr2m mesophyll cells i. Evolved when atmosphere’s [CO2] was lower than today’s [CO2] (395 ppm) C3 plants came first, and C4 plants evolved from C3. j. Ex: corn, sugarcane, sorghum grasses, but wheat and rice are also grasses and are C3 plants. So, grasses are not conclusively C3 or C4, some are in both categories. 3. CAM Plants Advantages k. Have the best WUE (Only 10 vol of water lost per vol of CO fixed) 2 l. Better WUE than a C3 plant under arid conditions, due to opening of stomata at night when transpiration rates are lower (no sunlight, lower temps, lower wind speeds, lower water lost through stomata) m. Ex: crassula, cacti, orchids. i. Crassula (edible house plant) –Are the leaves more or less acidic at night? 1. Malic acid is formed and stored in the vacuole over night, so the leaves are more acidic at night. So pH is lower at night. 9. C plants were theorized to have evolved in response to a lower CO level in the atmosphere in the past. 4 2 What is the CO lev2l in today’s atmosphere? a. CO in2 oday’s atmosphere = 395 ppm 10. What are the different variants of C plant4 and how are they identified? Given at least one example of each? 13 a. The variants are named after the enzymes that catalyze the decarboxylation reaction in the bundle sheath cells b. NADPME (NADP – malic enzyme) (most important/common) i. Ex: Corn, Sugarcane, Sorghum (liquor) c. NADME (NAD – malic enzyme) i. Ex: Pigweed (purple color) and Millet d. PEPCK (Phosphopyruvate Carboxykinase) i. Ex: Guinea Grass 11. Do you expect the proportion of C 4pecies to the total number of species to increase or decrease if you walk from Texas northward? a. Decrease, because the climate becomes cooler and less arid, and C4 plants are most abundant in dry arid climates. So, south has more C4 than north on a map. 12. What are the differences between photorespiration and dark respiration of plants? What purposes does each serve? Where do they happen inside a plant cell? b. Photorespiration and Dark Respiration vii. Rubisco RuBP carboxylase/oxygenase 1. RuBP + CO2 –Calvin Cycle (carboxylase) 2. RuBP + O2 –photorespiration viii. PHOTORESPIRATION –RuBP + O2 3PGA + phosphoglycolate (rubisco catalyzes the rxn and CO 2is a byproduct) 1. Occurs in chloroplasts, peroxisomes, and mitochondria 2. Can only happen when light is available 3. Photorespiration has no obvious physiological function 4. Absent in C4 plants ix. DARK RESPIRATION (i.e. CELLULAR RESPIRATION) 1. Glucose pyruvic acid acetyl CoA (in cytoplasm) 2. Krebs Cycle (Citric Acid, TCA cycle) –mitochondria (matrix) 3. Electron transport system –mitochondria (inner membrane) 4. Mitochondria a. Jelly like substance –matrix 5. Purpose: dark respiration provides energy for plant growth and maintenance. 6. Dark respiration happens in living cells 24 hours a day, all the time. a. Happens in plants and animals (including humans) x. Photosynthesis vs. Respiration 1. Photosynthesis is the making of carbohydrates (glucose) a. Anabolism b. Only autotrophs can carry out photosynthesis 2. Respiration is braking down carbohydrates a. Catabolism b. Autotrophs and heterotrophs have respiration 13. Know the photosynthetic light response curve well, esp. the key points in the curve and what they tell us about photosynthetic responses. Look below at the curve (graph) a. Dark Respiration Point (DRP): area where light is less than LCP. 14 i. Here, there is no photosynthesis, but cellular respiration is happening. So, the plant is emitting CO t2 the environment. b. Light Compensation Point (LCP): a point at which there is 0 net CO upta2e i. At LCP: Photosynthetic rate equals cellular respiration rate, so no net CO 2 ii. Unit is the unit of PAR iii. Varies from plant to plant based on the amount of light exposure over time iv. If PAR exceeds this point than there is a net gain of carbon, but if PAR falls short, there is a net loss of carbon v. Shade intolerant species – have high LCP (desert plant) vi. Shade tolerant species – have low LCP (plant that grows in the shade) c. Light Saturation Point (LSP): point at which the uptake of CO can increase no further with an 2 increase in PAR i. Photosynthetic rate continues to increase as PAR increases until it gets to the light saturation point (second red arrow). At this point, any light greater than light saturation point will not do anything to net photosynthesis rate, since capacity for photosynthesis has been saturated. d. Light Saturated Photosynthetic Rate: The max photosynthetic rate (I.e. rate at the LSP) e. Maximum rate of net photosynthesis: a plateau in the uptake of CO as P2R increases f. Other adaptations to water stress i. Waxy layer on leaves –prevents excess water loss ii. Plants grow in shade –cooler and more moist For graph on the right: Bottom Blue arrow: DRP Top Blue Arrow: Light Saturated Photosynthetic rate Leftmost red arrow: LCP Rightmost red arrow: LSP 14. What are the differences between Rubisco and PEP carboxylase in terms of their adaptations to temperature? a. Rubisco: enzyme is active only during the day b. PEP Carboxylase: enzyme is active only at night 15. What are the sources of carbon, hydrogen and oxygen for plants? What about the major mineral nutrients? a. Carbon Dioxide and Water give plants C, H, and O b. Major mineral nutrients come from soil (includes N, P, K, Ca, etc.) 15 16. What is root/shoot ratio? How do plants adapt to different nutrient environments? a. Scientists use a ratio to show how much of a plant’s resources are allocated to a specific component of the plant (root vs. shoot). Shoot is everything nonroot. b. Root:Shoot Ratio = root biomass/shoot biomass c. Another ratio: Root fraction: Root biomass/total biomass d. Highly enriched soil creates a smaller root to shoot ratio (since the high amount of nutrients go towards creating more leaves, increasing shoot); whereas poor soil creates a larger root/shoot ratio to compensate for low nutrients (nitrogen), resources must be allocated towards roots e. Pay attention on exam; he might ask shoot:root ratio instead of root:shoot ratio. Shoot:root is simply the opposite ratio (1/3 would become 3/1) 16
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