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EarthSystemsScience

This lesson is taken from an education module developed for Challenger Center’s Journey through the Universe program. Journey through the Universe takes entire communities to the space frontier.

Start the Journey at www.challenger.org/journey.

Challenger Center, Challenger Center for Space Science Education, and the Challenger Center logotype are registered trademarks of Chal leng er Cen ter for Space Science Education. No portion of this module may be re pro duced with out written permission, except for use within a Journey com mu ni ty. ©2002, Challenger Center for Space Science Education.

January 2002

Funded by grants from NASA’s Minority University Research and Education Division and Offi ces of Space Flight, Space Science, and Earth Science

CHALLENGER CENTER’S JOURNEY THROUGH THE UNIVERSE2

Lesson 1: What is Necessary forLife?

Lesson SummaryStudents perform two experiments intended to investigate vary-ing conditions for growing plants and bacteria. In the first ex-periment, students strive for optimal growing conditions forplants. In the second experiment, the students grow bacteria inilluminated and dark environments, and discover that life formscan survive without the presence of sunlight. As a result of theexperiments, students realize that the necessary resources for lifeare water, nutrients, and a source of energy. These resources drivethe basic biochemical process of life on Earth: the production ofsugars through photosynthesis or chemosynthesis. Students ex-amine the flow of resources – nutrients and energy – throughfood chains in an ecosystem. They discuss how interaction be-tween the Earth systems is essential for maintaining a healthybiosphere.

Lesson DurationFour 45-minute classes over 1 or 2 six-week periods, with weekly10-minute observations and daily 5-minute maintenance

Grade Level

9-12

ESSENTIAL QUESTIONWhat are the resourcesnecessary for life to thrive?

OBJECTIVESStudents will be able to:◗ Perform experiments

designed to growplants and bacteria ina controlled environ-ment.

◗ Identify the resourcesnecessary for life:liquid water, nutrients,and a source of energy.

◗ Explain the productionof sugars throughphotosynthesis andchemosynthesis.

◗ Explain how resourcesflow through anecosystem.

CHALLENGER CENTER’S JOURNEY THROUGH THE UNIVERSE 3

Science Overview

The Earth is filled with life. Almost everywhere we havelooked, we have found life. As investigations of more ex-treme environments on Earth are conducted, our under-standing of where life might exist, what is necessary forlife, and even the very origin of life on Earth has had to berevised. As a result, there is a more comprehensive under-standing of the close-knit interactions between living or-ganisms and their environment. These advances have alsoallowed the search for signs of life elsewhere in the uni-verse to mature to the science of astrobiology.

What is Life?It might seem easy to determine whether something is aliveor not. A dog running in the park is alive, but a car drivingdown the street is not. But how could we prove that one isalive while the other is not (see Figure 1)?

There is no firm scientific definition of life, no single prop-erty that distinguishes entities that are alive from those thatare not. Instead, there are several characteristics that areshared by most life forms on Earth, such as reproduction orreplication; growth; metabolism; capability to maintain aninternal environment, separate from its surroundings withthe help of a membrane or a wall (e.g., cells); movement;and adaptation to the environment.

However, the problem with defining life by using a collec-tion of properties is that some non-living entities (such as afire) have many characteristics from the list, while someorganisms that probably are living (such as a virus) possessonly a few of them. Instead, some scientists define life as a

CORE 9-12 STANDARDS

NRC StandardsCONTENT STANDARD C4:◗ The atoms and molecules

on the earth cycle amongthe living and nonlivingcomponents of the bio-sphere.

◗ Energy flows throughecosystems in one direc-tion, from photosyntheticorganisms to herbivores tocarnivores and decomposers.

Figure 1. The difficulty of defining life exactly is demonstrated by comparing a dog (left), a car (middle)and a virus (right). It is difficult to prove conclusively that a dog and virus alive, a car is not, since theyshare many of the same characteristics. [Picture credits: http://www.free-graphics.com/clipart/Animals/

Brush_Stroke/thumbnails2.shtml (dog, car); http://spaceresearch.nasa.gov/research_projects/ros/eb.html (virus)]


NRC Standards, cont.

CONTENT STANDARD C5:◗ The energy for life prima-

rily derives from the sun.Plants capture energy byabsorbing light and using itto form strong (covalent)chemical bonds betweenthe atoms of carbon-con-taining (organic) molecules.These molecules can beused to assemble largermolecules with biologicalactivity (including proteins,DNA, sugars, and fats). Inaddition, the energy storedin bonds between theatoms (chemical energy)can be used as sources ofenergy for life processes.

◗ As matter and energy flowsthrough different levels oforganization of livingsystems — cells, organs,organisms, communities —and between living systemsand the physical environ-ment, chemical elementsare recombined in differentways. Each recombinationresults in storage anddissipation of energy intothe environment as heat.Matter and energy areconserved in each change.

self-contained chemical system capable of undergoing bio-logical evolution. This provides a long-term view of life –governed by adaptation and evolution – combined with theshort-term processes guiding the lives of individual organ-isms. The long-term processes guide our understanding ofthe evolution of life on the scale of the biosphere, while short-term processes can be used to determine conditions that arenecessary for life forms to exist.

The Basic Process of Life on Earth: The Production of SugarsThe basic process of life on Earth is the production of glu-cose sugar from water and carbon dioxide with the help ofan energy source. Sugars are important for life because theyare a way to convert inorganic carbon into organic carbon,and to store energy inside living organisms.

The production of glucose from inorganic carbon can be writ-ten as:

water + carbon dioxide + energy ➔ glucose + waste

There are two basic sources of energy for this process. Theone we are most familiar with is sunlight: plants capture sun-light with chlorophyll and use the energy to produce sugarthrough photosynthesis. The waste product is oxygen, andthe formula for the production of glucose can be written as:

6H2O + 6CO2 + sunlight ➔ C6H12O6 + 6O2

The other way to produce energy is through chemosynthe-sis, which uses geothermal or chemical energy as the energysource. As complex chemical compounds are broken into sim-pler ones, energy is released. Chemosynthetic organisms usethis energy to produce sugars. For example, micro-organismscan extract energy from hydrogen sulfide (H2S) and othercompounds billowing out from volcanic vents in the oceanfloor. The same basic equation for the production of sugarsapplies, but in this case, the by-product (waste) of the pro-cess is sulfates (compounds of sulfur and oxygen) instead ofoxygen gas. There are other forms of chemosynthesis usedby living bacteria; for example, the required energy may comefrom oxidizing compounds such as hydrogen gas, carbonmonoxide, ammonia, or hydrosulphuric acid.


Necessities of LifeBased on our understanding of how living organisms operate,and as the equation for the production of sugar indicates, the basicrequirements for life are◗ Nutrients◗ Liquid water◗ Source of energyAs our knowledge of the diversity of life on Earth has grown,this list has become rather vague about the nature of “nutrients”and “energy.”

Nutrients are the raw materials that living organisms need toconstruct and maintain their cellular structure. The most impor-tant chemical elements needed by living organisms include car-bon, nitrogen, oxygen, phosphorus, and sulfur. Different organ-isms require different kinds of nutrients. In fact, nutrients requiredby some living beings may be toxic to others.

Water is important because it is one of the molecules required inthe production of sugars; it is also part of many other chemicalreactions in living organisms. In addition, chemicals importantfor life processes can be dissolved in liquid water and transportedto different parts of the organism. Many biologically importantchemical processes can occur only in a water solution. Since thisis not possible if the water is frozen or in gaseous form, life pro-cesses require liquid water. It is, therefore, not surprising that lifediscovered to date seems to be limited to a temperature range ofabout -15˚C to 115˚C; under the right conditions, water can beliquid over this entire range.

All organisms require energy to stay alive. Energy is needed tomaintain the internal organization of living organisms, as well asfor a variety of biological activities, such as making moleculeslike DNA, transmitting signals between nerve cells, and causingmuscles to contract to allow effective movement.

Organisms that get energy directly from sunlight are called au-totrophs, while chemoautotrophs use chemosynthesis as thesource of energy. In both cases, the organism extracts energy di-rectly from the environment to convert inorganic substances touseable food. Heterotrophs get energy by eating autotrophs,chemoautotrophs, or other heterotrophs. They use the energy


stored in sugars in the organisms they consume to get energy topower their own life processes. Animals are heterotrophs.

Resources in an EcosystemLiving organisms, their physical environment, and the relation-ships between them can be described as an ecosystem. For ex-ample, a forest is an ecosystem. Food chains describe relation-ships between living organisms in a habitat and the foods theyeat. For example, a food chain may link grasses on a field, rabbitsthat eat the grasses, and foxes that eat the rabbits. Sometimes theinteraction in a particular environment involves many kinds ofliving organisms connected through a complex network of foodchains, forming a food web.

Food chains describe the flow of energy and nutrients throughthe ecosystem, from the inorganic environment to and throughthe biological components and back. Autotrophs andchemoautotrophs form the first link of all food chains on Earth.They take inorganic substances and convert them into organicsubstances. They also take energy from the environment throughphoto- or chemosynthesis and make it available for biologicalactivity. They are the primary producers in an ecosystem. Anexample of a primary producer is a plant in a forest.

Living organisms that eat primary producers for nutrients andenergy are primary consumers. An example is a rabbit eating theleaves of a plant. Secondary consumers – predators – eat the pri-mary consumers, for example a fox eating the rabbit.

Figure 2. A simple food chain in a forest: rabbit eats the leaves of a plant, a fox eats the rabbit, a beareats the fox. Energy and nutrients flow from the environment to the plant, from the plant to the rabbit,and on to the fox and the bear. Ultimately nutrients are recycled back to the environment by decompos-ers. [Picture credit: http://www.free-graphics.com/clipart/Animals/Brush_Stroke/thumbnails2.shtml]


Autotrophs and chemoautotrophs always are primary produc-ers, while heterotrophs may serve a variety of roles. Herbivoresalways are primary consumers, while carnivores are secondaryconsumers. Omnivores (e.g., humans and bears) can be eitherprimary or secondary consumers in an ecosystem.

There may be further steps in the process – a larger predator likea bear may eat the fox – in the form of tertiary consumers. Ulti-mately, the last link in the food chain is the decomposers, such asbacteria and fungi, that break down dead plants and animals intosimple nutrients. The nutrients then go back into the soil to beused again by plants. The atoms and molecules that make upnutrients circulate between the organic and inorganic componentsof an ecosystem. At each stage in the food chain, the nutrients arechanged to a form that can be stored within the organism andused as a source of energy later. At each stage, waste productsare also created. For an example of a simple food chain, see Fig-ure 2.

Energy also goes through transformations as it passes throughthe food chain. First, the energy of sunlight, or the geothermal orchemical energy of the environment, is transformed into chemi-cal energy stored as chemical bonds of sugars in the primary pro-ducers. As primary producers are eaten by primary consumers(and further by secondary consumers), the energy undergoes fur-ther transformations into other useful forms of chemical storage.

While energy flows through food chains, some of it is lost intothe environment as heat. The fraction of energy that living or-ganisms convert into stored chemical energy from the totalamount available determines their ecological efficiency. Most or-ganisms are able to convert only a small fraction of available en-ergy; that is, they have low ecological efficiency. Plants changeonly about 0.1-1% of sunlight into stored chemical energy. Ani-mals can convert 10-20% of the energy released by the food theyeat into stored chemical energy. All stages of the food chain loseenergy, and the process can be described in terms of a pyramid ofenergy (see Figure 3). Primary producers form the base of thepyramid, primary consumers make the second layer, while sec-ondary consumers form the upper layers. The pyramid shapeindicates that more energy flows through the primary producersin an ecosystem than through primary consumers, etc.


The pyramid of energy is related to the pyramid of biomass (seeFigure 3). Biomass describes the total mass of living material in aspecific area. In addition to actual living parts of organisms, thebiomass may include dead parts of organisms (such as the hairand nails of an animal). The shape of the pyramid of biomass isdue to two factors: not everything at the lower layers gets eatenby the upper layers, and not everything that is eaten gets digestedand put into biomass in the upper layers. The study of the biom-ass in different components of an ecosystem provides informa-tion on the relationship between species in that environment. Forexample, on land the biomass of plants is usually greater thanthe biomass of herbivores. In the oceans the biomasses are about

Figure 3. Example of a pyramid of biomass or a pyramid of energy.In both cases, the layers consist of primary producers, primaryconsumers, secondary (and possibly tertiary) consumers. Thepyramid of biomass shows the amount of biological matter that theecosystem is capable of supporting. The pyramid of energy shows theflow of energy through an ecosystem and how some energy at eachstep is lost into the environment as heat. The exact shapes of thepyramids vary from one ecosystem to another. For example, in oneecosystem the primary producer layer in the pyramid of biomassmay be twice as wide as the primary consumer layer, indicating thatin that ecosystem, much more producer matter is required to supportthe consumers. [Picture credit: http://www.free-graphics.com/clipart/Animals/Brush_Stroke/thumbnails2.shtml (images of bear, fox, rabbit,plant)]


the same. This suggests that the conditions in the oceans are fa-vorable for fast growth of small plants that are able to support agreater number of herbivores than land plants can.

SuccessionLiving organisms change the environment by taking chemicalcompounds and energy from the environment and by producingwaste and heat. Chemical compounds are returned to the envi-ronment when organisms die. In many cases, changes caused byliving organisms to the environment are minute, but in others,the changes caused by deposited products may be large enoughto change it to a new kind of environment. Other species mayfind this new environment desirable, even if the original envi-ronment might not have been to their liking. This concept of liv-ing organisms causing changes in their environment, and in thismanner creating conditions favorable for other species, is calledsuccession. Sometimes, the changes in the living organisms’ en-vironment is caused by non-biological effects. In both cases, thegradual changes occurring over time are called ecological suc-cession.

An example of ecological succession is a forest recovering from afire. After the fire has devastated the forest, grasses and wild-flowers reappear first. Shrubs and trees come back later, followedby animals that depend on the food provided by the plants fortheir existence. The new plants change the environment from theburned-down forest to a thriving ecosystem through the processof succession. Figure 4 shows an example of succession in a for-est after clearcutting removes part of the forest.

Biosphere as an Earth System

Figure 4. Example of a succession in a forest in Saskatchewan. After part of a forest is removed in aclearcut, grasses are the first to return. Later, shrubs and small trees return, and eventually the forestprogresses toward an old-growth forest, called climax forest. [Picture source: Saskatchewan Interactive Website, University of Saskatchewan; http://interactive.usask.ca/ski/forestry/ecosystems/forest_succession.html]


The living organisms inhabiting the biosphere – the region onand near the surface of Earth where conditions are hospitable forlife – are dependent on the other components of the Earth sys-tem: geosphere, atmosphere, and hydrosphere. Living organismstake inorganic nutrients from the ground, from the oceans andlakes, and from the atmosphere. They use geothermal or chemi-cal energy, or sunlight traveling through the atmosphere, to pro-cess inorganic molecules into organic matter. Waste products and,ultimately, deceased bodies will be returned to the inorganic com-ponents of the Earth system. In this manner, the matter on Earthcirculates from inorganic matter to organic matter and back again.The Earth is a well-balanced, interconnected system, and inter-action between all its components is essential to the well-beingof all systems, including the biosphere and the organisms inhab-iting it.

An example of the effect of the biosphere on other components ofthe Earth system is the impact that the emergence of life had onthe atmosphere. Earth’s early atmosphere was very different fromthe oxygen-rich atmosphere today (about 21% of the air is madeup of oxygen). The chemical composition of the oldest rocks inthe Earth’s crust shows that significant molecular oxygen (O2)could not have been present, because materials in the rock oxi-dize (that is, combine with oxygen) rapidly when exposed to oxy-gen-rich air. It is thought that much of the early atmosphere wasmade of volcanic gases such as ammonia, carbon dioxide, carbonmonoxide, methane, and nitrogen, and there were only trace con-centrations of molecular oxygen present. This kind of atmosphereis called a reducing atmosphere – it is not oxidizing and allowssubstances that quickly degrade in the presence of molecular oxy-gen to accumulate. This low-oxygen situation persisted untilabout 2 billion years ago. By this time, life had a chance to evolveand spread for about a billion years, and molecular oxygen wasbeing generated by living organisms, as a by-product of photo-synthesis, at such high levels that it began to accumulate in theatmosphere. The life forms largely responsible for the build-upof oxygen are cyanobacteria (often called blue-green algae). Overthe next couple of billion years, oxygen levels in the atmosphererose, and Earth’s early, reducing atmosphere was replaced by thepresent-day oxygen-rich atmosphere.

Looking for Life Elsewhere in the Universe


Astrobiology is the study of the origin of life on Earth and thepossibility of life elsewhere in the Universe. Since Earth is theonly place in the Universe where we know life exists, the searchfor signs of life elsewhere is based on what we know about theproperties of life here on Earth. The question of what is necessaryfor life is central to this study, because it can be used to deter-mine what kind of conditions are required for life to exist else-where in the Universe.

The first step in assessing whether a planet or a moon is a candi-date for hosting extraterrestrial life is to determine whether thebasic requirements for life are met there. In addition to the basicrequirements of life discussed above – nutrients, liquid water, asource of energy – a comfortable environment is also thought tobe necessary. For example, the environments in which life formsthrive need to be protected from harmful high-energy radiationthat destroys the basic molecules of living chemistry (ultraviolet,X-rays, gamma rays, and high-energy particle radiation from theSun). On some planets and moons, strong magnetic fields andthick atmospheres (like those on Earth) can provide adequateprotection, or life forms could have developed under some pro-tective cover, such as rocks or ice.

There currently are three possible places in the Solar System whereastrobiologists believe life forms could exist or once could haveexisted. Mars is thought to have had liquid water in the distantpast. Some scientists suggest Martian meteorites may have fos-sils of ancient Martian life forms, but the evidence has not beenconclusive. Jupiter’s moon Europa may have a liquid water oceanunderneath its icy surface, with life forms living in environmentssimilar to the ocean floor on Earth. The third possibility is Saturn’smoon Titan. The composition of Titan’s atmosphere is such thatcomplex molecules similar to those believed to have led to theemergence of life on Earth could form there. All of these possi-bilities are being actively investigated. Scientists also are alert forsigns of life outside of our Solar System, but these studies are atvery early stages.

Searches for extraterrestrial life in the Solar System are expectedto find only signs of microbial life, because it is the most likelykind to be found outside of Earth. Even on Earth, most of thebiomass still is in microbes. Micro-organisms thrive in extremeconditions that are much easier to find on planets or moons, than


the environment comfortable for humans. Even the discovery ofmicrobial life outside of Earth would be significant, because itwould suggest that as long as conditions are right for life formsto survive, life can develop.

The study of extremophiles is most valuable for understandingthe possibility of extraterrestrial life. Extremophiles are life formsthat live in extreme conditions, right at the edges of what scien-tists believe life can tolerate and still survive. Examples of theseconditions include high-acidity, high-temperature, low-tempera-ture, high-radiation, and high-pressure environments. Since noknown planets or moons offer conditions as cozy for life as Earth,life forms that may exist elsewhere are probably similar toextremophile life forms adapted to an extreme (by terrestrial stan-dards) environment . Extremophiles on Earth can serve as a guideto the possibilities for life elsewhere. An important natural labo-ratory to study thriving ecosystems depending on the presenceof extermophiles are hydrothermal vents.

Hydrothermal VentsHydrothermal vents are essentially geysers on the sea floor. Theyform along mid-ocean ridges, underwater mountain ridgesformed along tectonic plate boundaries. In some instances, thepeaks of the ridges rise above the ocean surface, forming islandssuch as Iceland. At the plate boundaries, new sea floor is createdwhen the plates spread apart slowly, about 1-2 cm per year. Inaddition to hydrothermal vents, mid-ocean ridges feature under-water earthquakes and volcanoes. Vents are created when magma– volcanic molten rock – underneath the ocean floor heats up coldwater seeping through cracks in the rocks. This water, heated toboiling, rises to the ocean floor and surges into the ocean as hotwater spring, an underwater geyser. The water is usually rich inminerals swept up from beneath the ocean floor.

Hydrothermal vents have been a subject of intense study sincethe first ecosystems were discovered near the vents in 1977. Theexistence of these ecosystems was a great surprise, because untilthen it was thought that photosynthesis was the only way to sup-port the first link of the food chains on Earth. The discovery ofthese thriving ecosystems ushered in the recognition of chemo-synthesis as an alternative to photosynthesis to provide the basisfor food chains.


Hydrothermal vents allow scientists to study exotic, chemical-based ecosystems in a real-life laboratory. Even though chemo-synthetic organisms exist in more familiar surroundings (such asthe muddy water the students use in their experiment), hydro-thermal vents offer an excellent opportunity to study ecosystemsthat are built entirely on chemosynthetic bacteria as the first linkin the food chains. Some scientists have even suggested thesekinds of vents may be similar to hot environments where life be-gan on Earth billions of years ago, rather than environments closeto the traditional image of Darwin’s warm pond. The conversionof non-biological chemistry to actual biology may have happenedduring the interaction of rocks and circulating hot water. For thisreason, the study of hydrothermal vents may provide unique cluesto understanding the possibility of life having developed on plan-ets and moons outside of Earth.


Lesson Plan

Warm-up◗ Discuss with the students properties of living entities. Show

a picture of a mammal – a bear in a forest, for example. Askstudents to come up with properties of the bear that indicateit is alive. Go through the list and observe which of theproperties apply to humans, as well. Now show a picture ofa non-living entity in the same environment – for example, aforest fire. Go through the list written for the bear andobserve which properties apply to the non-living entity. Pickanother living entity in the same environment, but a differ-ent kind (i.e., plant or bacteria). Go through the list again. Inmost cases, there should be some properties of the mammalthat apply to the other living being, but also to the non-living entity, as well as properties that the other living entitymight not have, but the non-living might. Illustrate to thestudents the difficulty of determining exactly how we cantell an entity is alive.

◗ Explain that scientists looking for different forms of life onEarth face a similar problem. Many scientists use the long-term definition of life as a baseline, but this makes quickdeterminations of whether an entity is alive difficult. Theproblem becomes even more severe when trying to investi-gate the possibility of life elsewhere in the universe. Sincewe do not have a good understanding of how to define life,scientists are first concerned with basic life processes, andwhat living organisms need to survive.

Pre-Assessment◗ Have students hypothesize and write down their thoughts

on what living things need to survive. Gather the lists forcomparison with the results at the end of the lesson. Ex-plain to the students that they will test their hypotheses intwo experiments.

STUDENT MATERIALS

Activity 1:(per group)◗ Worksheets 1-2 (1 copy

per student)◗ 3 Containers for plant

growth experiment (8-10 inch diameter flowerpot works well)

◗ Soil, enough to fill thepots

◗ Package of seeds (fast-growing seeds workbest, same seeds for allgroups)

◗ Water◗ scaleMaterials may differ based onthe experiments the studentscreate.


ACTIVITY 1: Optimal Conditions forPlant Growth

Preparation & Management◗ Bring, purchase, or have students bring from their

homes pots, soil, and seeds.

TEACHING TIP

◗ In Activity 1, we recommend that edible herbs be used as theplants to grow. This way, the end products of the experimentcan be used instead of just thrown away, graphically demon-strating how primary consumers depend on primary produc-ers. Basil works particularly well for this experiment.

◗ Decide whether you want to have the students performthe experiment as competition or collaboration. If youchoose competition, the goal of each group is to growas much biomass as they can with as few resources aspossible. If you choose collaboration, different groupscan be assigned varying growing conditions. Theadvantage of competition is to give students an addi-tional reason to perform the experiment well – whichgroup will win? The advantage of collaboration is thatvariations in growing conditions that are thought to bedisadvantageous can be used by some groups, since inthis case the idea is to experiment with a variety ofgrowing conditions without competition.

◗ The students are asked to weigh their pot several timesduring setup, because it is the easiest way to measurethe weight of the ingredients. Once something new isadded to the pot, subtracting the “old” weight from the“new” weight gives the weight of the added ingredient.

◗ The students are asked to weigh their pot weekly tomonitor how much the contents of the pot change.Weighing the pots will provide information on howmuch plant mass has grown. Just adding the mass ofthe water is not sufficient, because some of the waterwill evaporate (how much depends on the humidity ofthe air).

Activity 2:(per group)◗ Student Worksheets 3-

5 (1 copy per student)◗ 2 500-milliliter gradu-

ated cylinders orcolumns

◗ Black mud (enough tofill the graduatedcylinders)

◗ 80 g of CaSO4 (Plasterof Paris: found in anyhardware store)

◗ 2 jars or beakers formixing

◗ Stirring rods◗ Organic straw or filter

paper bits (tear stripsof lab filter paper)

◗ 3 liters of pond water,salty sea water, orswamp water

◗ 4 grams baking soda◗ 2 multivitamin pills,

crushed◗ Plastic wrap◗ Rubber bands◗ A light source that can

stay on for six weeksor longer

◗ Tape and markers forlabeling columns

◗ Flashlight with redcellophane on lightedend (can be attachedwith rubber band)

◗ Optional: PipetteAC

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TEACHING TIP

◗ Activity 1 may require more materials over the growing period, depend-ing on the procedures the students devise. For example, regular wateringof the plants is expected to be part of each group’s procedures.

◗ You can have the experiment proceed for longer or shorter periodsof time. Six weeks is sufficient time, under most conditions, to seeclear plant growth and probable variations with the biomassproduced. Longer growth time may make the differences betweengroups more noticeable, and may therefore be desirable. Edibleplants may also have a suggested optimal growing period beforeharvest.

TEACHING TIP

◗ Both activities take several weeks to complete. Ideally, you should beginActivity 2 after Activity 1 is completed and its results analyzed, so thatthe idea that living organisms do not necessarily require sunlight is notintroduced until after discussion of the results of Activity 1. If you arepressed for time, you can do the experiments at the same time, or startActivity 2 a week or two after Activity 1. However, in this case theprocess of coming up with sunlight as a necessity of life and then findingout that it does not apply in all situations may not be as clear.

Procedures1. Tell students they are going to experiment with their hypotheses

of what living things need to survive. Have them come up withpossible tests to examine their hypotheses. You can guide thestudents toward the idea of exploring optimal conditions forgrowing plants with the help of any plants you may have in theclassroom or by pointing out plants outside the classroom. Em-phasize that it is ideal to be able to control and monitor the experi-ment, so doing it in the classroom is the best solution.

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CHALLENGER CENTER’S JOURNEY THROUGH THE UNIVERSE 17A

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2. Once the idea of growing plants in a controlled situation is intro-duced, explain that the students will be given a container, soil,and a package of seeds. The goal is to grow as much plant matteras possible with as few resources as possible over a six-weekperiod.

3. Divide students into groups of three or four students.

4. Have students follow instructions in Student Worksheet 1 to plantheir experiment.

5. Give ingredients to students and have them set up the experi-ment, as they described in Student Worksheet 1. Make sure thecontainers are placed somewhere they can be monitored over thesix-week period but not disturbed.

6. Have students keep track of their nurturing of the plants duringthe six-week growth period, as described in Student Worksheet 1.

7. Have students complete Student Worksheet 2 at the end of thegrowth period to analyze their results.

TEACHING TIP

◗ In case it is difficult for students to take care of the plants on a dailybasis, you may want to offer them alternative solutions – watering plantsbefore or after school, or offering to water the plants yourself according tostudents’ written instructions.

TEACHING TIP

◗ You can have students monitor many different aspects of the experiment,such as soil moisture, temperature, pH, etc.


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Reflection & Discussion◗ Write down results from different groups and compare them.

Discuss which growing conditions produced the best results andwhy.

◗ Discuss with students the properties of the basic equation of photo-synthesis. Point out that the source of one of the main ingredients –carbon dioxide – is air. This means that if you have a 100-year-oldtree in your schoolyard, it has drawn much of the resources to buildits bulk from thin air!

◗ Have students re-evaluate their original hypotheses of what livingorganisms need to survive. Discuss whether the students want tochange their hypotheses and why. As a result of the experiment,students are expected to be able to identify nutrients, liquid water,and sunlight as the necessary ingredients for plant growth and, byextension, for life in general.

Transfer of Knowledge◗ Discuss how the varying growing conditions relate to agriculture.

Are there specific steps farmers can take in environments wherethere is not much sunlight because of cloud cover, or the amount ofsunlight varies greatly during the year? How can the amount ofwater and nutrients that plants receive be regulated? Are thereways to cope with extended periods of drought? What effect mightother environmental factors such as wind, erosion, and stormshave? Have the students design a plan to produce the most pota-toes (or another crop suitable for your area) in a given area for theleast cost. If feasible, have the students follow their plan.


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ASSESSMENT

4 Points◗ Experiment notes are clear.◗ All observations are complete.◗ Reasoning behind answers is sound.◗ Answers to questions exhibit clear understanding of the concepts.

3 Points◗ Experiment notes are clear.◗ All observations are complete.◗ Answers to questions address the concepts.

2 Points◗ Experiment notes are understandable.◗ Observations are few, but acceptable.◗ Answers to questions are difficult to understand.

1 Point◗ Experiment notes are incomplete.◗ Observations are not complete.◗ Only some questions are answered.

0 Points◗ No experiment notes.◗ No observations or they are not complete.◗ Questions are not answered or the answers are unreadable.

Placing the Activity Within the LessonDiscuss whether the results from the experiment are applicableelsewhere on Earth. Discuss photosynthesis and its role as the firstlink in most food chains on Earth.


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ACTIVITY 2: Observing Bacterial Growth

Preparation & Management◗ Make sure that you have all of the ingredients for the experi-

ments. You may have to secure a suitable location for placing oneset of containers under constant light and another set in darknessfor the duration of the experiment (six weeks).

◗ Provide, or have students bring to class, water from a nearbypond, swamp or ocean; about three liters (a little less than agallon) per group.

◗ Obtain mud from a local lake, river, bay or estuary. Make surethere is enough mud to fill the graduated cylinders to a depth of8-15 cm. If the mud is not completely black, let it sit for a few daysin a jar to blacken.

Procedures1. Tell students that they are going to experiment further with their

hypotheses of what living things need to survive. Have the classexamine their lists after Activity 1. They should arrive at nutri-ents, water, and sunlight listed as necessary ingredients for life,possibly with other details or additions. Can the students think ofinstances where some of these ingredients might not be available,but where life can still exist? You can lead students to think ofbacteria growing in darkness (such as moldy bread in a cupboardor human intestinal bacteria) or deep ocean floors. The goal is tocome up with a realization that sunlight might not always beavailable. Is there anything else that could replace sunlight? Havestudents hypothesize. Have them come up with possible tests toexamine their hypotheses. You can guide the students toward theidea of growing something both in sunlight and in darkness tocompare results. Students should be able to realize that plants areprobably not the ideal test subject. Explain that you have a pre-pared test available.

2. Divide the class into pairs or small groups. Each pair of studentswill set up two identical columns. One will be kept in the darkand the other will be placed under a light source.

3. Have students follow instructions in Student Worksheet 3 toprepare their experiment.


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4. Give ingredients to students and have them setup the experiment,as described in Student Worksheet 3. Make sure the containers areplaced somewhere where they can be monitored over the six-week period, but not disturbed.

5. Have students keep track of their experiments during the six-week period, as described in Student Worksheet 3.

TEACHING TIP

◗ In addition to basic naked-eye examination of the experiment, havestudents perform more detailed analysis of the progress of the experi-ment. At the end of the third week, have students take samples formicroscopic wet mount observations from (1) surface layers of water, (2)surface layers of the mud, (3) colored layer from the mud. Make sure thestudents do not disturb the column; they can use a pipette to gather thesamples. Using a high-power magnification microscope to study the wetmounts, the students can look for cell shapes that would indicate thepresence of different types of organisms.

TEACHING TIP

◗ A variation of the experiment is to add a third cylinder, and keep itscontents mixed (oxygenated) throughout the experiment by occasionalagitation. This would demonstrate, for example, what happens if thesediments which are present in the column are disturbed by animals.

Reflection & Discussion◗ Ask students to describe their observations of the experiment. The

basic result should be that a succession of organisms were grow-ing in both columns. In the column left in the light, studentsshould see green-colored algae the first week. Then, over a periodof six weeks, at least five different species of bacteria may grow insuccession in both columns.


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◗ Ask students to hypothesize how the columns in the darknessexhibited bacterial growth. Explain that instead of sunlight, thethird necessary ingredient for life is a source of energy. For photo-synthesis, the source of energy is sunlight, but the bacteria in thecolumn placed in darkness used chemosynthesis to extract energyfrom their environment.

◗ Explain to the students that they have observed the process ofsuccession in action: as life forms thrive in an environment, theirwaste products create changes in the environment that make itsuitable for other life forms to thrive. Describe the general idea ofsuccession behind the experiment: how the first group of bacteriacreated the environment suitable for the other species.

◗ Have students complete Student Worksheet 4 to further analyzetheir results.

◗ Explain that the experiment the students just concluded is similarto what happens in deep sea vents. Describe hydrothermal ventsand why they are an important subject of study. (See ScienceOverview for more information)

TEACHING TIP

◗ It is difficult to know exactly what bacteria are actually growing in thestudents’ experiments. Possibilities include Clostridium, which is ananaerobic heterotroph and, if present in the column, would use the strawor filter paper as a carbon source to produce food. Another bacterium,Desulfovibrio, uses the waste of the anaerobic heterotroph as its source ofcarbon and the CaSO4 as an energy source. This bacterium produces thehydrogen sulfide required by the rest of the ecosystem. Three otherbacteria Beggiatoa (white or yellow), Chlorobium (green), andChromatium (purple and violet) use hydrogen sulfide as part or all oftheir energy source. This process requires oxygen so you will find thesebacteria near the surface of the sediments. After the original purple andgreen patches form, black spots will begin to appear. These black patchesare deposits of H2S (hydrogen sulfide, which has a distinct odor) that arecreated by the sulfur-oxidizing aerobic cyanobacteria. Chemosyntheticbacteria need the H2S for energy, and grow soon after these black spotsdo. The bacteria that use light as their major energy source with somehydrogen sulfide are heterotrophic and the bacterium that uses hydrogensulfide as its entire energy source (e.g., Beggiatoa) is chemotrophic.


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Transfer of KnowledgeYou may have students complete one or a combination of the following:

◗ Discuss with students the prevalence of microbes on Earth: mostof the biomass is in microbes, and scientists have suggested thatthe amount of biomass underground, in the so-called deep hotbiosphere, is larger than the biomass on the surface.

◗ Explore ecological succession in a variety of situations, from aforest recovering from a devastating fire, to emergence of newislands from undersea volcanoes.

◗ Examine the importance of hydrothermal vents in advancing ourunderstanding of the possible abodes of life on Earth and else-where.

◗ Research extremophiles and the exotic habitats they occupy.

◗ The experiment the students perform is a version of aWinogradsky column, named after a Russian microbiologistSergei N. Winogradsky (1856-1953). Winogradsky studied howbacteria interact with their environment and discovered thebacteria Beggiatoa, one of the bacteria found in deep-sea hydro-thermal vent ecosystems. Have students research early studies ofbacteria and the concept of succession.

◗ Use data available on the Internet or in books to examine how lifehas adapted to changing environments on Earth. Students, orgroups of students, may report on topics such as:

◗ Evolution as a way of adapting to different environments.

◗ The diversity of life existing in different environments onEarth.

◗ Life in strange environments on Earth (hydrothermal vents,glacier lakes, etc.).

◗ The current understanding of global environmental changeand how living beings may adapt to it.

◗ The possibility of life exisiting elsewhere in the Solar Systemand in the Universe.


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ASSESSMENT

4 Points◗ Experiment notes are clear.◗ All observations are complete.◗ Reasoning behind answers is sound.◗ Answers to questions exhibit clear understanding of the concepts.

3 Points◗ Experiment notes are clear.◗ All observations are complete.◗ Answers to questions address the concepts.

2 Points◗ Experiment notes are understandable.◗ Observations are few, but acceptable.◗ Answers to questions are difficult to understand.

1 Point◗ Experiment notes are incomplete.◗ Observations are not complete.◗ Only some questions are answered.

0 Points◗ No experiment notes.◗ No observations or they are not complete.◗ Questions are not answered or the answers are unreadable.


Placing the Activity Within the Lesson◗ Discuss photosynthesis and chemosynthesis and their roles

as the first link in all food chains on Earth.

◗ Discuss how the pyramid of biomass describes how muchliving matter can be supported in an ecosystem.

◗ Discuss how the pyramid of biomass is connected to thepyramid of energy.

◗ Have students complete Student Worksheet 5 to discuss theflow of resources in the ecosystem.

◗ Discuss the flow of energy through the ecosystem.

◗ Discuss how the necessities of life flow through the foodchains and circulate between the living organisms and theirenvironment.

◗ Discuss how biological activities affect the environment andultimately the components of the Earth system.

◗ Discuss the science of astrobiology and how the results fromstudying life and its properties on Earth are used to findsigns of life elsewhere in the Universe.

Lesson ClosureAs a result of the experiments, the students are expected tounderstand that the only resources necessary for life are asource of energy, liquid water, and nutrients. Resources in anecosystem – energy and chemical compounds – pass throughthe ecosystem and cycle between the biological and inorganiccomponents of the environment. The presence of life on Earthhas a significant impact on the other components of the Earthsystem – atmosphere, hydrosphere, and geosphere. Interactionbetween the components is essential for maintaining a healthybiosphere. Living organisms have adapted in a variety ofenvironments during the course of the evolution of life onEarth, and many life forms thrive in conditions that are extremeby human standards. Studying extremophiles provides clues tothe question of the possibility of life elsewhere in the Universe.


Supplemental ResourcesAmerican Museum of Natural History Black Smoker Expedition Web site

http://www.amnh.org/nationalcenter/expeditions/blacksmokers/home.html

NASA Ames: Astrobiology at NASAhttp://astrobiology.arc.nasa.gov/

NASA Astrobiology Institutehttp://nai.arc.nasa.gov/

NASA Astrobiology Magazinehttp://www.astrobio.net/

Science@NASA article “Life as We Didn’t Know It”http://science.nasa.gov/headlines/y2001/ast13apr_1.htm

Science@NASA article “Life on the Edge”http://science.nasa.gov/newhome/headlines/msad13jan99_1.htm

AcknowledgmentsActivity 2 has been adapted from the NASA TOPEX/Poseidon activity “Growing Chemosyn-thetic Bacteria.”


STUDENT WORKSHEET 1 - OPTIMAL CONDITIONS FOR PLANT GROWTH

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Date:

Students in the group:

Your group will explore optimal conditions for growing plants from seeds with a minimalamount of resources.

Given the ingredients – soil, seeds and a container – write a plan describing how you willnurture the plants to get maximum growth with minimum resources. Write your detailed planin the space below.

Prepare the experiment and weigh all ingredients:

1. Weigh the empty container.2. Pour dirt or soil into the container and weigh the container again.3. Put seeds into the container, weigh again.4. If you cover the seeds with more soil, weigh the container again.

The weight differences at each step will give you the weight of each ingredient put into thecontainer at each step.

Write the weight of the ingredients in the space below.

Container:Soil:Seeds:

Write down the type of seeds used:


STUDENT WORKSHEET1 - OPTIMAL CONDITIONS FOR PLANT GROWTH

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You have to monitor all ingredients you add into the experiment during the growth period. Forexample, if you add water at any point, write down how much water you add, by weight. Setaside a time at least once a week to observe changes in the container: growth of the plant, soilmoisture, temperature, etc. Keep a journal of your observations and any additions to the ex-periment (see format below). Also, weigh your container each week to monitor how its weightmay change during the experiment.

Plantgrowth

Plant height(cm)

Mass ofadded

ingredients(such aswater)

Weight ofcontainer

Otherobservations

Week 1

Week 2

Week 3

Week 4

Week 5

Week 6


STUDENT WORKSHEET1 - OPTIMAL CONDITIONS FOR PLANT GROWTH

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At the end of the experiment, weigh the components of the container carefully. Remove theplants carefully, making sure no plant matter remains in the pot and as little soil as possible istrapped in the roots of the plant. You can weigh the mass of the dirt using the same method asin the beginning of the experiment: weigh the container with dirt in it, pour out the dirt, thenweigh the empty container. Write your results in the space below.

Container:Soil:Additional ingredients:

(introduced during the experiment)Plant matter:

(note that some soil will be trapped into the roots of the plant matter; try to shake as muchsoil from the roots before measuring the plant’s weight)

Biomass is a description of the total weight of living material in a specific area. The weight ofplant matter in your container is therefore the amount of biomass produced in your experi-ment.

Questions:1. Compare your results with those of other groups. What was the optimal conditions forgrowing the plants? Were they what you expected? Why or why not?

2. Based on the results, what are the necessary ingredients for plant growth?

3. Do the results apply in other situations on Earth?


STUDENT WORKSHEET 2 - PHOTOSYNTHESIS

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Answer the following questions:

1. The plants in your experiment used photosynthesis to convert the energy of sunlight into aform they can use for a variety of biological activities. The energy is stored in the form ofsugars (carbohydrates), which can later be converted into energy useable by cells. In photosyn-thesis, (glucose) sugar is produced from water (H2O) and carbon dioxide (CO2) with the help ofsunlight and oxgen (O2) is the waste product. This process can be written as:

water + carbon dioxide + sunlight ➔ glucose + oxygen

Write the stoichiometric equation for the production of glucose sugar (C6H12O6).

2. Soil is not involved in the equation of photosynthesis above. What is the role of soil in plantgrowth?

3. The Earth system consists of biosphere (living beings and the area near or on the surface ofEarth they inhabit), hydrosphere (oceans and other systems containing water), atmosphere, andgeosphere (solid Earth). Identify where the different ingredients for photosynthesis come from.Explain how the process affects the environment in which it takes place.

Name: Date:


STUDENT WORKSHEET 3 - OBSERVING BACTERIAL GROWTH

Name: Date:

Your group will monitor growth of bacteria in two containers, one placed in light, one in dark-ness.

Prepare the experiment:1. Add about four grams of CaSO4 (Plaster of Paris) to enough mud to fill one graduated

cylinder to a depth of about 8.0 cm (3.2 inches). Then dump it into a jar or beaker and mix itthoroughly with the stirring rod.

2. Place a straw or filter paper in the jar with the mud and mix gently. (It may help to addsome pond or seawater here to ease stirring.)

3. Transfer the mixture back to the cylinder. Make sure that all of the ingredients in the mixtureare poured into the cylinder. Add pond or seawater so that the mud is covered with at least8 centimeters (3.2 in) of water.

4. Add to the cylinder 0.2 grams of baking soda and one crushed vitamin pill. Stir again tomake sure all the air bubbles are gone.

5. Set the cylinder aside for 30 minutes to settle.

6. After 30 minutes, if more than two centimeters (0.8 in) of water have pooled at the top, pouroff all but one centimeter (0.4 in). If there is less than one centimeter (0.4 cm), add morepond water.

7. Repeat steps (1) through (6) for the other graduated cylinder.

8. Label the cylinders with your names.

9. Place one graduated cylinder in a darkened area where it will not be disturbed for at leastsix weeks. Place the second cylinder under the light source. (You may wish to store both set-ups in the same area with one cylinder in (or under) a box. This will help to keep both insimilar conditions.)

1. Write down your expectations of what will happen in each cylinder.

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For at least six weeks, examine the columns weekly and look for signs of bacterial growth.Record smell, color, number of layers of mud, or any other observations. Keep a journal of yourfindings. You may wish to make a drawing of the container at each week. You can calculate thevolume of the different layers and sediments and see how they change during the course of theexperiment. You may use a safety light (flashlight covered with red cellophane) to examine thecolumns being grown in the dark.

Figure: Description of the bacterial growth experiment.page 2 of 3



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Questions:2. Are the results what you expected? Why or why not?

3. What kind of connections do you see between this experiment and the plant growth experi-ment?

4. Did the contents in the container change during the six-week period? Why do you thinkthis was the case?


STUDENT WORKSHEET 4 - CHEMOSYNTHESIS

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Answer the following questions:

1. Some of the bacteria in your experiment used a process called chemosynthesis to producesugar. Chemosynthesis is an alternative to photosynthesis, and is useful in environments wherethere is little or no sunlight. An example of an environment like this is hydrothermal vents(basically, underwater geysers) at the bottom of the oceans. Micro-organisms living thereextract energy from hydrogen sulfide (H2S) and other minerals billowing out from the oceanfloor. The same basic equation for the production of sugars applies as for photosynthesis, but inthis case, the by-product (waste) of the process is sulfates (forms of sulfur) instead of oxygen,and the equation can be written as:

CO2 + 4H2S+ O2 ➔ CH2O + 4S + 3H2O

The energy for this particular process comes from the hydrogen sulfide. Other sources ofenergy are also possible, but this is one of the most common chemosynthetic reactions. Writethe stoichiometric equation for the production of glucose sugar (C6H12O6).

2. What purpose did the different ingredients (muddy water, CaSO4, straw or filter paper,baking soda, multivitamin pills) added to the cylinder in the bacterial growth experiment have?

3. The Earth system consists of biosphere (living beings and the area near or on the surface ofEarth they inhabit), hydrosphere (oceans and other systems containing water), atmosphere, andgeosphere (solid Earth). Identify where the different ingredients for chemosynthesis come from.Explain how the process affects the environment in which it takes place, as well as the otherspheres.

Name: Date:


STUDENT WORKSHEET 5 - RESOURCES IN AN ECOSYSTEM

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Living organisms, their physical environment, and the various relationships between them canbe described in terms of an ecosystem (e.g., a forest). Food chains describe the relationshipsbetween living organisms in a habitat and the foods that they eat. Complex networks of foodchains are called a food web. The roles of the living organisms in the ecosystem can be de-scribed as◗ Primary producers - Take inorganic substances and energy from the environment and make

them available for biological activity (e.g., plants).

◗ Primary consumers - Take their energy and nutrients from eating primary producers (e.g.,herbivores).

◗ Secondary consumers – Eat primary consumers (e.g., carnivores).

◗ Decomposers - Break down dead organisms into simple nutrients that are then returned tothe environment.

1. Describe an ecosystem of your choice, sample food chains in it, and the roles of differentorganisms in the food chains (Do not use the example in the sample figure in this worksheet.)

2. Can some organisms serve many different roles? Why or why not?

Name: Date:



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Resources in an ecosystem – nutrients and energy – flow through the food chains, andcycle between the environment and living organisms. One way to monitor these resourcesis through a pyramid of energy and pyramid of biomass, which describe the amount ofenergy or biomass in each component for the ecosystem. In the pyramids, the base is madeof primary producers, the second layer of primary consumers, the third layer of secondaryconsumers, and layers above it consist of tertiary or higher consumers (that eat secondaryor higher consumers). Decomposers are not depicted in the pyramid, since they get theirenergy and nutrients from all levels when organisms in them die.

3. Convert the sample food chain from Question 1 to a pyramid of biomass. Estimate (orresearch the internet) for typical masses of different organisms in your sample ecosystem,as well as how much energy or mass is lost between different layers. Make sure to markwhether the numbers are your estimate (and the basis for your estimate) or write down thereference from which the numbers came. Draw your pyramid in the space below.



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4. Why do you think the flow of evergy through an ecosystem has a pyramid shape?

5. What does the pyramid of biomass tell you about the amount of living organisms atdifferent levels?

6. There are situations where th epyramid of biomass is not as clearly shaped like a pyramidas usual. For example, in the oceans the biomasses primary producers and primart consumerscan be the same. What does this tell you about the two components compared with land, wherethe biomass of plants is usually greater than the biomass of herbivores?

7. Describe the flow of energy and chemical compounds through the ecosystem you describedin Question 1 of this worksheet.


Teacher Answer Key

Student Worksheet 11. Answers will vary according to the students’ results and

expectations.2. Nutrients (soil), water, sunlight.3. Results should be applicable to the growth of all green

plants. They are also applicable to other living organisms,though the need for sunlight is somewhat debatable fororganisms that eat other living beings.

Student Worksheet 21. 6H2O + 6CO2 + energy ➔ C6H12O6 + 6O2

2. It provides the chemical compounds necessary for buildingthe plants, including the ingredients for making chlorophyllto capture sunlight. Soil also provides support for theplant’s roots and retains a water supply.

3. Water: in the classroom, the water probably comes from thewell or from another water reservoir. These are replenishedby rain, sometimes by rivers (above or underground).Ultimately, the water is involved in the large-scale hydro-sphere.Carbon dioxide: comes from the air. Involves the atmo-sphere.Sunlight: comes from the Sun. Does not originate on Earthbut passes through the atmosphere on its way to the sur-face.Glucose: essential in the biosphere. Will be broken downand ingredients returned to the soil when the organism diesOxygen: released to the atmosphere.The process has a substantial effect on the environment bytaking resources from it and releasing wastes or by-prod-ucts into it.

Student Worksheet 31. Answers will vary according to the students’ expectations.2. Answers will vary according to the students’ expectations.3. In both cases, biological activity is observed. The second

activity indicates that living organisms can grow in dark-ness as well as in light.


4. Different living organisms appeared at different times.Some students may have also observed (correctly) that theyseemed to change the environment as a result of theirpresence. This means that the first organisms changed theenvironment, favorably, for the later-appearing organisms.(Students may also suggest that later-appearing organismsjust may have taken longer to appear; there is no way todisprove this based on the visual observations alone andmay even be true for some organisms.) All the organismswere present in the muddy water at the beginning of theexperiment, the later-appearing ones were just not active atan observable level until the environment became favor-able.

Student Worksheet 41. 6CO2 + 24H2S+ 6O2 ➔ C6H12O6 + 24S + 18H2O2. Muddy water contained the different bacteria that grew in

the cylinder, as well as provided the environment (soil andwater) in which the bacteria grew. Straw or filter paperserved as the source of carbon to produce sugars. TheCaSO4 served as the source of energy (instead of hydrogensulfide) in the experiment. Vitamins, nitrogen from bakingsoda, as well as sulfur from CaSO4 are required nutrientsneeded for the bacteria’s life processes.

3. Carbon dioxide and oxygen: comes from the minerals in thevent water or from the ground. Geosphere and hydro-sphere.Hydrogen sulfide: comes from the minerals in the ventwater. Geosphere and hydrosphere. Provides the energy forthe process.Glucose: essential in the biosphere. Will be broken downand ingredients returned to the soil when the organism dies.Water: released to the environment.The process has a substantial effect on the environment bytaking resources from it and releasing wastes or by-prod-ucts into it.


Student Worksheet 51. Answers will vary. An example of a food chain in an eco-

system is provided in the Science Overview.2. Most organisms have only one role – plants are primary

producers, herbivores primary consumers, and carnivoressecondary consumers. However, omnivore can serve aseither primary or secondary consumers.

3. Answers will vary according to the answers to Question 1.However, make sure that students identify their source ofestimates for masses of different components in the ecosys-tem, and if the students use their own estimates, the esti-mates are reasonable and follow the pyramid shape.

4. Some of the energy is lost at each stage, so that less of itpasses to the next component in the ecosystem.

5. A certain number of primary producers are required tosupport a certain number of primary consumers, which inturn determines how many secondary consumers can besupported. Only some of the organisms in a given layer ofthe pyramid get eaten by the organisms in the layer aboveit.

6. Conditions in the oceans are favorable for fast growth ofsmall plants which are able to support a greater number ofherbivores than land plants can.

7. Answers will vary according to the students’ answers toQuestion 1. In all cases, energy and chemical compoundsare taken from the environment by the primary consumersthrough photo- or chemosynthesis. The energy is stored insugars so that it can be used later. Primary consumers gettheir energy and nutrients by eating the primary consumersand releasing the energy contained in the sugars. Secondaryconsumers do the same by eating primary consumers, anddecomposers get their energy and nutrients by processingthe dead bodies of the other components in the ecosystem.At each stage, some of the energy is lost to the environmentas heat. At each stage, chemical compounds are also re-turned to the environment as by-products of biologicalactivity; the compounds may be different from those origi-nally taken from the environment.

Challenger Center Programs

The internationally acclaimed Challenger Learning Center Network currently consists of state-of-the-art, innovative educational simulators located at 49 sites across 29 states, Canada, and the United Kingdom. Staffed by master teachers, the core of each Center is a two-room simulator consisting of a space station, complete with communications, medical, life, and computer science equipment, and a mission control room patterned after NASA’s Johnson Space Center. See www.challenger.org for information.

A joint initiative of Challenger Center for Space Science Education, the Smithsonian Institution, and NASA, Voyage — A Journey through our Solar System is a space science exhibition project that includes permanent placement of a scale model solar system on the National Mall in Washington, DC, and at locations all over the world. See www.voyageonline.org for information.

Space DaySM launches new Design Challenges created by Challenger Center each school year. The inquiry-based challenges are designed to inspire students in grades 4-8 to create innovative solutions that could aid future exploration of our solar system. See www.spaceday.org for information.

Challenger Center’s Journey through the Universe program provides under-served communities with diverse national resources, including K-12 curriculum materials, teacher workshops, classroom visits by scientists from all over the country, and Family Science Nights. See www.challenger.org/journey for information.

The MESSENGER spacecraft (MErcury Surface, Space ENvironment, GEochemistry and Ranging) is to be launched in 2004 and go into Mercurian orbit in 2009. Challenger Center is one of the partner organizations charged with MESSENGER education and public outreach activities. See www.messenger.jhuapl.edu for information.

Through the Challenger Center Speakers Bureau, Voyages Across the Universe, staff members speak to student audiences of 30-1,000, conduct workshops for 100-300 educators, give keynote and featured presentations at conferences, as well as conduct Family Science Nights at the National Air and Space Museum, and other facilities across the nation, for audiences of 300-1,000 parents, students, and teachers. See www.challenger.org/speakers for information.

For information about other Challenger Center programs, or to purchase our classroom resources, visit www.challenger.org/store.

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