Learning Experience 3 Everything Under the Sun · 2016-08-23 · 24 Learning Experience 3...

Learning Experience 3

Eve r y th ing Unde rthe Sun

What kinds of substances in the environment are essential for life? In LearningExperience 2, you determined that euglena respond to light. What otherresources in the environment are required to maintain the characteristics of life in organisms?

In this learning experience, you continue to identify resources that areessential to survival, specifically in the environment of a plant. Then you explorehow a plant uses these resources.

Discuss the following questions with your partner, and record your thinking inyour notebook. Be prepared to share your ideas with the class. You will use thewords and ideas discussed in class to construct a concept map. Your concept mapwill illustrate the resources plants require and how the resources might beobtained and used.1. What kinds of resources do you think plants require to maintain the

characteristics of life?2. How do you think plants use each of these resources?3. How do plants take in these resources from their environment?

1. Working with a partner, use the words identified in the class discussion tocreate a concept map. Identify which concept is the main idea. Decide howto group the remaining ideas based on how they relate to one another.

2. Pick linking words for the map that define the relationships between theconcepts. Linking words should not be concepts themselves.

3. Start constructing a map by branching one or two general ideas from themain concept. Add other, more specific concepts to the general ones as themap progresses.

TTASKASKTASK

Brainstorming

ProloguePrologue

21

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22 Learning Experience 3 Everything Under the Sun

4. Enclose each of the concepts in a box or circle. Use lines to connect theconcepts. Write a linking word on the line that tells why the concepts areconnected.

5. Look for opportunities to draw cross-linkages to connect concepts fromdifferent branches of the map.

6. Be prepared to discuss your map with the class.

You Light Up My LifeYou will use radish plants to investigate the resource requirements of a plant andto find out what happens if a plant does not obtain the resources it needs. You

then use this information to examine the biochemicalprocesses by which a plant obtains what it needs for survival.

What happens within a plant when it obtains the resourcesit requires? You may have already studied or examinedphotosynthesis in other classes. Photosynthesis is the processin which plants use the resources of sunlight, carbon dioxide(CO2), and water (H2O) to fulfill their needs for energy andfood. The components of the word refer to its functions:“photo” means light, and “synthesis” means putting together.

What structural components of a plant are important inobtaining and using resources? Look at the drawing of a plant inFigure 1.9. Below the soil surface, a highly branched root systembrings in water and minerals from the soil and anchors the plantin the ground. The stem contains a system of tubes that begins inthe root and runs all the way to the top of the plant. One set oftubes (xylem) in the stem conducts water and dissolved materialsdrawn from the soil up to the leaves (Figure 1.10). Another set oftubes (phloem) in the stem transports sugars, the products ofphotosynthesis, and other molecules throughout the plant.

The leaf is the major site of photosynthetic activity (seeFigure 1.11). Carbon dioxide enters the leaf through tiny holes inthe leaf’s surface called stomata. Water travels from the rootsthrough the stem and enters the leaf. Special cells in the leaf canabsorb energy from the sun using a molecule called chlorophyll.The water, carbon dioxide, and energy from the sun (solarenergy) are all essential components in the photosyntheticreaction. They come together in special cells in the leaf. As youwork with your radish plants, be sure to think about therelationship between the plant parts and the resources the plant needs.

ACTIVITY

leaf–location of photosynthesis

tubes–transport water, sugars,and other molecules

stem–contains tubes that run from

roots to leaves

roots

Figure 1.9A plant’s structure enables itto take up resources.

secondary phloem

primary phloem

primary xylem

secondary xylem

Figure 1.10The cross section of a stemshowing the phloem andxylem.© Clouds Hill Imaging Ltd./Corbis

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For each group of four students:

• 4 small pots of radish plants, each grown under one of these conditions:• in the light, under normal conditions• in the dark, under otherwise normal conditions• in a closed environment, under otherwise normal conditions• in a closed environment in the absence of carbon dioxide (CO2)

• 4 safety goggles• iodine solution• 4 petri dishes• 1 scalpel or utility knife• 1 forceps or tweezers• 1 beaker of distilled water• 1 wax marking pencil

For the class:

• 4 plant pots, 5–8 cm (2–3 in.)• potting soil• 1 pkg radish seeds• jars/beakers to cover plants and pots• trays• chart paper• 2 boiling water baths

MaterialsMaterials

Learning Experience 3 Everything Under the Sun 23

Topic: Plant AdaptationsGo to: www.scilinks.orgCode: INBIOH223

Figure 1.11Cross sections of a leaf showing stomata, phloem, xylem, and chlorophyll-containing cells (palisade mesophyll).

© Brad Mogen/Visuals Unlimited © Dr. Dennis Kunkel/Visuals Unlimited

© Ken Wagner/Visuals Unlimited

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• 100 mL hot 95% ethyl alcohol• 1 beaker (1000-mL) filled with tap water• 100 g sodium hydroxide (flakes or pellets)• medicine cups• 1 beaker (1000-mL) for waste iodine

1. At the beginning of this unit, you or your teacher germinated radish seeds under the following conditions:

• in the presence of light, air, soil, and water• in the presence of air, soil, and water; in the absence of light• in the presence of light, air, soil, and water (in a closed environment)• in the presence of light, air, soil, and water; in the absence of CO2 in the

air (in a closed environment)2. Compare the characteristics of the plants in each pot. Include height, color,

ability to grow, and any other characteristics you may notice.3. Label each of 4 petri dishes for one of the following: “light,” “dark,” “closed

normal,” or “closed no CO2.”4. Take 1 leaf from a plant in each pot.5. Identify each leaf you removed by notching it with a scalpel or knife. (For

example, use no notches for those grown under normal conditions, 1 notchfor those grown in the absence of CO2, etc.) Be sure to record in yournotebook how you marked each leaf (see Figure 1.12).

6. Immerse each leaf in boiling water for approximately 1 minute. Removefrom boiling water with forceps.

7. Remove the pigments (chlorophyll and others) by immersing each leaf inhot 95% ethyl alcohol.

8. When most of the pigment (color) has been removed, use forceps to removethe leaf from the hot alcohol. Dip each leaf in hot water again for a fewseconds. This will keep the leaf from becoming brittle.

9. Place each leaf in the proper petri dish and cover with iodine solution.Allow leaves to sit for a few minutes. Iodine is used to detect the presence ofstarch. Starch is a carbohydrate that is an essential substance found in allliving things. Iodine changes from brown to black or blue black in thepresence of starch.

STOP &T H I N K

PPROCEDUREROCEDUREPROCEDURE

SAFETY NOTE

Sodium hydroxide

can burn your skin. If itcomes in contact withskin or clothing, rinsewell with water.

N O T E

• The chemical

sodium hydroxide(NaOH) absorbs theCO2 gas in the air.Most of the CO2 canbe removed from theair by growing a plantin a closed system inthe presence of NaOH.• In your notebook,define the questionsbeing asked in thisexperiment and yourhypothesis.

radish leaves

notch cut out

One notch meansgrown in the absenceof CO2.

No notch meansgrown under normalconditions.

Figure 1.12Notching the leaves for identification.

SAFETY NOTE

• Boiling water can

cause burns. Ethyl alcohol can catch fire.• Iodine stains and is apoison. Be sure to cleanany spills thoroughlyand avoid contact withskin and clothing.

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10. Remove each leaf with forceps and dip it into the beaker of clear tap waterto rinse it. Pour iodine into the designated iodine waste beaker. Rinse outthe petri dish to remove any remaining iodine solution.

11. Place each leaf back in its petri dish.12. Compare the staining of each leaf. Record in words and drawings what you

observe.

You may wish to discuss with your group the responses to the Analysis questions.1. Prepare a laboratory report for this experiment in your notebook. Be sure to

include the following:a. the questions being asked;b. your hypothesis;c. the experimental design, or how the experiment was set up;d. the data or observations you made; ande. the analysis and conclusions (include your responses to the Analysis

questions that follow).2. In an experimental design, the condition to be tested is a variable. That is,

every condition in the experiment is held the same, or constant, exceptone—the variable. What was the variable in each of the experiments in theactivity You Light Up My Life? What were the conditions that were heldconstant?

3. The experiment in which the effect of CO2 was measured needed to bedesigned as a closed system. What is meant by a “closed system”? Whatwould have happened if the system had not been closed?

4. In addition to having only one variable, a good experiment will also have apositive control or samples in which the outcome is known because there isno variable. Which plants served as your positive control? That is, whichplants had all the appropriate resources? Which could be considered ashaving been grown under the best conditions regarding resources?

5. What do you think would eventually happen to the plants growing in thedark? to those growing without carbon dioxide? State your reasons.

6. Based on the experimental design, describe how you know starch is aproduct of photosynthesis. What would happen to those plants that wereunable to synthesize starch?

7. A chemical reaction takes place when the interaction of two or moresubstances results in the formation of a different substance or substances.The new substances have different physical and chemical properties thanthe starting substances. Chemical reactions are often expressed as anequation. For example, the reaction that results in water can be expressed asthe joining of two components to form a third:

oxygen + hydrogen → water

Write a word equation based on what you have observed in this activity.Your word equation should describe what you think happens when plants aregrown under appropriate environmental conditions with all the necessaryresources for photosynthesis.

ANALYSISANALYSISAAA


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How Does Your Garden Grow?How do plants get what they need to survive? This question has intrigued peoplefor centuries. Speculations about plants and their feeding habits have given riseto many stories; one such story follows.

On the island of Madagascar, off the east coast of Africa, the natives tell of astrange tree. This tree is an eater of meat, so they say—human meat. Theperson who ventures too close to the tree is seized by the tree’s long branchesand imprisoned. The branches wrap themselves so tightly around the victimthat no matter how hard he or she struggles, the trap holds fast. Then slowly,but with great strength, the tree pulls its victim into its hollow center. There thebody is digested, except for the bones, and the tree is nourished until anothervictim comes along.

From Plants that Eat Insects: A Look at Carnivorous Plants by Anabel Dean. Copyright 1977by Lerner Publications Company, a division of Lerner Publishing Group. Used by permission.All rights reserved.

In the following article, Isaac Asimov, scientist and writer of science fiction, asksthis question in greater detail. He presents one possible hypothesis based on anexperiment carried out in the 1600s.

Plants somehow supply the food. It must, somehow, come from somewhere. Itcan’t really form “out of nothing.” [Plants require soil, water, air, and sunlight togrow. How does a plant take these substances and use them?] . . .

The man who had the thought [to find out] was Jan Baptiste van Helmont,an alchemist and physician of the Low Countries, who lived and worked interritory that is now Belgium, but was then part of the Spanish monarchy.

Van Helmont had the notion that water was the fundamental substance ofthe universe (as, in fact, certain ancient Greek philosophers had maintained).If so, everything was really water, and substances that didn’t look like waterwere nevertheless water that had merely changed its form in some fashion.For instance, water was necessary to plant life. Could it be then, that, unlikelyas it might seem on the surface, plant tissue was formed out of water, ratherthan out of soil? Why not try and see?

In 1648, van Helmont concluded his great experiment, great not onlybecause it produced interesting and even crucial results, but because it wasthe first quantitative experiment ever conducted that involved a livingorganism. It was the first biological experiment . . . in which substances wereweighed accurately and the carefully noted changes in weights supplied theanswer being sought.

Van Helmont had begun by transplanting a shoot of a young willow tree intoa large bucket of soil. He weighed the willow tree and the soil separately. Nowif the willow tree formed its tissues by absorbing substances from the soil, then,as the willow tree gained weight, the soil would lose weight. Van Helmont carefully kept the soil covered so that no materials could fall into the bucketand confuse the manner in which the soil lost that weight.

Naturally, van Helmont had to water the willow tree; it wouldn’t growotherwise [see Figure 1.13].

For five years, van Helmont watered his tree with rainwater. It grew andflourished and at the end of the time, he carefully removed it from the bucket,knocked the soil from its roots and weighed it. In five years of growing, thewillow tree had added 164 pounds to its weight.

Very good! Now to weigh the soil after it had been dried. Had it lost 164pounds to the tree? Not at all. It had lost only two ounces!

READING

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The willow tree had gained a great deal of weight—but not from the soil.What was the only other substance that made contact with the willow tree, van Helmont asked himself. The answer was: Water.

From this, he deduced that it was from water that the plant drew itssubstance, not from the soil. He used the results of this experiment to arguethat water was indeed the fundamental substance of the universe, since if itcould change to plant tissue it could surely change to anything else as well.

Excerpted from Photosynthesis by Isaac Asimov. Copyright © 1968 by Isaac Asimov.Reprinted by permission of BasicBooks, a member of Perseus Books, L.L.C.

Record your responses to the following in your notebook.1. What question did van Helmont set out to investigate in his experiment?2. Was van Helmont’s experimental design a good one (based on what was

known at the time)? Why or why not?3. What conclusion did van Helmont reach about what constituted food for

plants? Was his conclusion valid based on the data he collected? Why orwhy not?

4. How do van Helmont’s conclusions compare to the conclusions you reachedin your plant experiment? Are they the same, different, or unrelated?Explain.

5. Redesign van Helmont’s experiment and predict the results.

Sunlight Becomes YouWhat does sunlight provide for a plant? How does a plant use CO2? What is“starch” and why does the plant need it?

The sunlight and air that a plant needs are used in the process ofphotosynthesis to generate food for a plant. Food is any substance that provides

ANALYSISANALYSISAAA


willow tree

soil coveredwillow shoot

1643 1648

Figure 1.13Van Helmont’s tree.

READING

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building blocks and energy for organisms. An example of food for a plant is the starchthat you measured in the activity You Light Up My Life. The process ofphotosynthesis can actually be separated into two related biochemical processes. Oneprocess depends on the presence of light; the other can take place in the absence oflight (see Figure 1.14). During the light-dependent reaction, energy in sunlight (solarenergy) is absorbed by chlorophyll. Chlorophyll is the green pigment that gives plantstheir characteristic color. The chlorophyll, in turn, transfers this solar energy toanother molecule. This molecule stores the solar energy as chemical energy.

The chemical energy obtained during the light-dependent part of photosynthesis (called the “light-dependent”) is then used in the light-independent process (called the “light-independent”). During this process, theatoms in carbon dioxide and water are rearranged to form new molecules ofsugar. Sugar is the substance that makes up starch. The sugar molecule containscarbon, oxygen, and hydrogen atoms; all of these were originally found in thecarbon dioxide and water. In addition to sugar, this reaction also generates waterand oxygen. The water and oxygen are formed from the hydrogen and oxygenatoms of the original water and carbon dioxide. The sugar molecule also


chemical energy

light (solar energy)

light-dependentreaction(a) water gaseous oxygen

light-independentreaction water(b) carbon dioxide

sugar

starch

Figure 1.14Two related processes of photosynthesis: the “light-dependent” and “light-independent” reactions.

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contains chemical energy in the bonds between the atoms. Thus, the sugar moleculebecomes the primary source of both energy and building materials for the plant.

The word equation that you created during the analysis of your experimentcan now be converted into a chemical equation:

12 H2O + 6 CO2 + energy → C6H12O6 + 6 H2O + 6O2

Plants require energy and building materials to carry out the processes of living.By the process of photosynthesis, plants obtain the nutrients and energy to grow,to respond to their environment, and to repair and maintain themselves. Withoutany one of the resources used in photosynthesis—air, water, sunlight—plants will“starve” to death. What happens to these molecules of C6H12O6 sugar in theplant? Some of them remain as simple sugars such as fructose or glucose. Glucose,or grape sugar, gives that fruit its distinctly sugary taste. Another abundant sugarin plants is sucrose. Sucrose is also called table sugar or cane sugar because of itshigh concentration in the stems (canes) of plants, such as the sugar cane plant.Sucrose is synthesized when fructose and glucose are joined together to form amolecule containing two separate sugar molecules (disaccharide). Sucrose is themajor sugar that is transported throughout a plant. It is the starting material formany other molecules in the plant.

Sugar molecules can also join together as links in long chains called polysaccharides. The starch that you tested for in the activity You Light Up MyLife is an example of a polysaccharide. Starch consists of many glucose moleculesjoined together. Starch serves as food storage for the plant; when food is needed,the starch is broken down into simple sugars. The sugars can then be transportedwherever in the plant they are needed as building blocks and energy sources.

Some sugars form the starting materials for other large molecules in the plant.Living things are made up of several large biomolecules in addition to sugars(carbohydrates). These biomolecules include proteins, lipids, nucleic acids, andfatty acids. In the next several learning experiences, you will explore what thesebiomolecules look like and how they are formed in living organisms.

Sugar and starch are the initial products of photosynthesis. They are producedin the cells that make up a plant’s leaves. As described earlier in this learningexperience, carbon dioxide from the air enters the leaf through tiny holes calledstomata. The stomata also allow release of oxygen back to the environment.Oxygen is one of the by-products of photosynthesis. In the leaf cells surroundingthe stomata, the interaction of carbon dioxide, water, and light forms sugars.(The water is brought to the leaf through the stem, and light energy is absorbedby the green pigment chlorophyll.) These sugars are transported through phloemin the stem to parts of the plant where they are needed. Some of the sugar isstored in the cells. Here it is converted into starch as a stored source of energyand building blocks.

All the nutritional needs of the plant are met between the photosyntheticactivities of the leaf and the absorbing activities of the root (which bring inminerals needed by the plant from the soil). And by using these processes, plantscan meet most of the nutritional needs of the rest of the living world.

Record your responses to the following in your notebook.1. Concept maps have a number of uses. For example, you can use a concept

map to analyze reading materials. Create a concept map from the reading“Sunlight Becomes You.” Your map should show how photosynthesis takes

ANALYSISANALYSISAAA


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place and how its products enable a plant to survive and maintain the characteristics of life. Include the following terms: photosynthesis, plants,sunlight, energy, chlorophyll, carbon dioxide, water, sugar, starch, leaf, stem,oxygen, root, biomolecules. (Use additional terms from the reading as youneed them.) Place each term in a circle and join the circles with linkingwords.

2. How might the plant and other organisms use the products of photosynthesis?Add these ideas to your map.

Hydroponics is a method for growing plants and crops in the absence of soil.Research hydroponics and describe how this method can supply all theresources that plants need. Describe why some agriculturists might choosethis method over more conventional methods.

If you have access to the Logal software program Biology Explorer:Photosynthesis, design and conduct your own extension of van Helmont’sresearch.

During the Vietnam War, defoliating agents were used as a form of warfare.These agents were designed to destroy plant life in areas where they wereused. Research the nature of the defoliating agents and how they worked.Explain why this form of warfare was considered effective by some,inhumane by others. Base your explanation on your understanding of the roleof photosynthesis in life.

The Wetlands Protection Act limits actions such as cutting down trees in wetlands areas. Describe what would happen to the populations of smallerplants living under trees that were removed. Explain your predictions. If youhave access to the Logal software program Biology Explorer: Photosynthesis,use the Independent Exploration “Sun and Shade Plants” to help you investigate the light requirements of different plants. Similarly, the Independent Exploration “Delicate Balance” may be helpful. This activityfocuses on different levels of water availability and humidity.

Changing climatic conditions alter the growth of plants. Explain how highertemperatures and greater concentrations of carbon dioxide influence thegrowth of plants and oxygen levels in the atmosphere. If you have access to the Logal software program Biology Explorer: Photosynthesis, use theIndependent Exploration “Origin of Fossil Fuels” to help you investigate the role of climate in plant growth.

E X T E N D I N G

CAREERFocus Landscaper and Grounds Manager Devin checks his clipboard

one last time before heading out with his crew. They have a busy day aheadof them. They have appointments at eight different homes in the Lakelandarea to landscape residential grounds. Projects for the day include plantingnew shrubs, spreading mulch, and mowing and fertilizing grass. The crew willalso plant a decorative flower garden and consult with a client about buildinga new front walkway.

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It’s mid-July and Devin is in the middle of his busiest season as alandscaper. Landscaping is a seasonal business, with steady work in thespring, summer, and fall. In the winter, Devin tries to keep busy by clearingsnow from walkways and parking lots. Devin’s landscaping business hasboomed since he started 4 years ago. He’s found that there is a lot ofdemand for residential landscapers, because many two-income families aretoo busy to landscape their yards.

After Devin graduated from high school, he wanted a career thatcombined his love of the outdoors and being physically active. So he found ajob with a landscaper in Lakeland. His supervisor trained him to operate themowers, trimmers, leaf blowers, and tractors, and to follow safety proceduresand proper planting procedures. But Devin was also interested in thebusiness end of landscaping. He discovered that most supervisors andowners have a formal education beyond high school. So he decided to goback to school for his associate’s degree. He took courses in landscapemaintenance and design, horticulture, botany, accounting, and English. Thatexperience gave Devin the background he needed to start his own business.

Now Devin is self-employed, providing landscape maintenance directly tocustomers on a contract basis. Although the vast majority of his time is spentat the site, he does have to manage all of the accounting and billing for hisbusiness, which includes sending invoices and tracking payments. SomedayDevin would like to become a Certified Landscape Professional. He canachieve his goal by taking an exam offered by the Associated LandscapeContractors of America (ALCA) and meeting certain education andexperience standards.

At the end of the day, Devin checks off the last house on his list. He sendshis crew home and heads to his home office to take care of the accounting.Completing some paperwork is actually a nice change after a tiring day ofphysically demanding work.

Botanist Hannah uses DNA analyses to determine the evolutionaryrelationships of the cinchona tree. She conducts these tests to ensure thatthe tree’s species name accurately reflects its genetic makeup. The cinchonatree is relatively well known for its use in making quinine sulfate to preventmalaria. But surprisingly little is known about where cinchonas fit in theevolutionary scheme. Hannah is on a mission to change that. Hannah worksat a world-class botanic garden. Her work is similar to putting the pieces of ajigsaw puzzle together. She determines how different cinchona speciesevolved and their degree of relatedness. Because several species ofcinchona trees exist, this is no easy task.

Traditionally, scientists used morphology or physical attributes, like leafshape and texture, to classify plants. But for more useful and accurateclassifications, Hannah compares their DNA sequences. The higher thenumber of base-sequence matches, the closer the evolutionary relationship.Hannah sees herself as an explorer. Knowing she is one of the first people tosequence a gene or a particular stretch of DNA energizes her. She feelsprivileged to be involved in such important and interesting work. Hannah’swork as a botanist allows her to pose questions and find the answers.

Hannah comes from a family of avid gardeners. From an early age, shewas fascinated by the life story of plants—how and why they grow from aseed to a mature plant. She found that a career in botany would combine herinterest in plants with science. Hannah attended a 4-year college to get herbachelor’s degree in plant biology. She then went on to get her master’sdegree in botany. Her classes focused on biology, math, chemistry, andphysics. But she’s also found her coursework in English, Latin, and history tobe invaluable in her day-to-day work.


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Hannah’s day not only consists of research in the botanical lab, but shealso helps run the lab. This involves doing the associated administrativetasks, such as ordering chemicals and equipment. She also does a lot ofwriting, including research papers, reports, and grant proposals.

To date, Hannah’s research has uncovered the fact that one cinchonaspecies is actually two distinct species. This finding will help scientists whoare working with cinchona trees to assess their medicinal properties to treatmalaria, which could potentially save lives. Ensuring that the name of a plantreflects its genetic makeup can have a huge impact on the production ofpharmaceutical products such as quinine.


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Learning Experience 3 Everything Under the Sun · 2016-08-23 · 24 Learning Experience 3...

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Transcript of Learning Experience 3 Everything Under the Sun · 2016-08-23 · 24 Learning Experience 3...