Plants, like all other living organisms have basic needs: a source of nutrition (food),

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1 LEARNING FROM LEAVES: FROM OBSERVATION TO INFERENCE Grades 4 6 I. Intrductin Plants, like all ther living rganisms have basic needs: a surce f nutritin (fd), water, space in which t live, air, and ptimal temperatures in rder t grw and reprduce. Fr mst plants, these needs are summarized as light, air, water, and nutrients (knwn by the acrnym LAWN). II. III. The purpse f this lessn is t teach students hw ne can examine a plant and learn abut hw it meets these needs. First, students examine leaves frm plants fund in three habitats: desert, trpical rain frest, and wetland. Then, they research thse habitats, share their discveries, and return t examining the leaves, nw armed with enugh infrmatin t make inferences abut the plants. Objective Students will emply the scientific prcesses f bservatin, cmparisn, and descriptin t make inferences abut the habitats in which particular plants have evlved. Standards Assessed Grades 3 5 Life Sciences Science Cntent Standards K 12 (2000), Califrnia State Bard f Educatin Plants have structures that serve different functins in grwth, survival and reprductin (3-3.a). Ecsystems can be characterized by their living and nnliving cmpnents (4-3.a). In any particular envirnment, sme kinds f plants and animals survive well, sme survive less well, and sme cannt survive at all (4-3.b). The Huntingtn Library, Art Cllectins, and Btanical Gardens 1

2 Observatin t Inference Grades 3 5 (cnt.) Investigatin and Experimentatin Science Cntent Standards K 12 (2000), Califrnia State Bard f Educatin Scientific prgress is made by asking meaningful questins and cnducting careful investigatins. As a basis fr understanding this cncept... students shuld develp their wn questins and perfrm investigatins (3-5, 4-6, 5-6). Students will differentiate bservatin frm inference (interpretatin) and knw scientists' explanatins cme partly frm what they bserve and partly frm hw they interpret their bservatins (4.6.a). Grades 6 8 Life Sciences Science Cntent Standards K 12 (2000), Califrnia State Bard f Educatin The number and types f rganisms an ecsystem can supprt depends n the resurces available and n abitic factrs, such as quantities f light and water, a range f temperatures, and sil cmpsitin (6 5.e). The Living Envirnment Benchmarks fr Science Literacy (1993), American Assciatin fr the Advancement f Science Animals and plants have a great variety f bdy plans and internal structures that cntribute t their being able t make r find fd and reprduce (5.A 6-8). In all envirnments freshwater, marine, frest, desert, grassland, muntain, and thers rganisms with similar needs may cmpete with ne anther fr recurses, including fd, space, water, air, and shelter. In any particular envirnment, the grwth and survival f rganisms depend n the physical cnditins (5.D 6-8). IV. Backgrund The subject f this lessn is the adaptatin f plants t their envirnments. Envirnment includes all the living (bitic) and nnliving (abitic) cnditins that surrund an rganism (its habitat). Abitic factrs include climate, sils, and events like lightening. Bitic factrs include surrunding rganisms and the actins f thse rganisms that affect the plants, like eating them. Plants' basic requirements fr living include bth bitic and abitic factrs, but this lessn fcuses n abitic factrs reflected thrugh leaf structure. Light: Thrugh phtsynthesis, plants cnvert energy frm the sun int energy fr their grwth and maintenance; green plants need the sun. Many plant structures ensure the expsure f leaves t light, as branches hld leaves up t the sun. Hwever, there is a limit as t the amunt f light a plant s phtsynthetic system can absrb withut being destryed. Plants sunburn when mved suddenly frm a lw light t high light situatin. In envirnments with lts f sunlight, plants prtect themselves frm verexpsure t the sun. 2 The Huntingtn Library, Art Cllectins, and Btanical Gardens

3 Observatin t Inference Air: The sugars prduced thrugh phtsynthesis are made f carbn mlecules frm the air. Withut access t carbn dixide, phtsynthesis wuld nt ccur. Carbn dixide is a naturally ccurring cmpnent f the Earth s atmsphere, and, frtunately fr aquatic plants, f mst water. In additin, plants require xygen fr respiratin, the breakdwn f sugars t release energy fr use in metablic prcesses. Water: Water is the stuff f life. The sugars prduced by phtsynthesis and many ther cmpunds will mix with this universal slvent. Water is the surce f pressure within individual plant cells that keep them inflated, rather than limp. (Think f what happens when plants begin t dry ut: they wilt.) Water mves cnstantly thrughut the plant and is cnstantly being lst as vapr escapes frm the leaves thrugh tiny penings called stmata. In trpical plants frm wet areas, lss f water may nt be a prblem. In plants that grw in water, it is usually n limitatin, but in the desert, develpment f adaptatins t cnserve water has been paramunt. Nutrients: Plants get their nutrients frm the sils in which they grw. The abitic mineral prtin f sils supplies anchrage and nutrients. Abitic water in the sil is the slvent in which nutrients enter plants thrugh their rts. A bitic surce f nutrients in sil is rganic matter, including plant and animal matter underging decmpsitin, and sil rganisms and their prducts. V. Materials Needed reference materials n wetland habitats, deserts, and trpical rain frests, which may include textbks, encyclpedias, nature bks, r web sites leaf r cutting f Eldea r anther aquatic species (frm an aquarium stre); make sure they dn t dry ut befre class leaf r cutting f Phildendrn r anther trpical frest species (frm plant stre); make sure they dn t dry ut befre class leaf r cutting f Crassula r anther species frm a dry envirnment (frm plant stre r the yard); make sure they dn t dry ut befre class magnifying lens data sheets (see belw) pencils r pens VI. Prcedure Guide students thrugh a discussin f the needs f living things. Discuss hw plants might meet thse needs in different envirnments. 1. Divide the class int three grups. 2. Hand ut data sheets and leaves f the three plant types, ne t each grup. The Huntingtn Library, Art Cllectins, and Btanical Gardens 3

4 Observatin t Inference 3. Ask the students t examine the leaves, bserving their structure and shape. Have them use a magnifying lens, if ne is available. Observatin: What d they ntice? Descriptin: Hw wuld they describe the leaves size, shape, clr, and texture? Cmparisn: Hw are the leaves similar and hw are they different? Have the students recrd their bservatins by drawing their three leaves, and making written ntes n the data sheet. Desert leaf: small, spherical, light gray, waxy Trpical rain frest leaf: large, flattened, dark green, waxy Aquatic leaf: small, flattened, dark green, delicate 4. Nw, mving away frm direct bservatin f the leaves t research, assign ne habitat t each grup: wetland, desert, and lwland trpical frest. Ask each grup t prepare a brief verbal presentatin abut the envirnmental cnditins f their habitat: climate (light, water, air), and sils (nutrients). Students shuld use reference materials t create their presentatins, but the reprts shuld be brief. 5. Next, return t bservatin f the leaves. Tear the leaves and bserve their internal structure. Can yu infer why the leaves have their structure? Desert plants generally have waxy cverings n their leaves t reduce water lss thrugh the leaf surface. These leaves may be almst spherical t reduce surface area, again t reduce water lss. These leaves are ften light green r gray, t limit the amunt f light that enters the leaf. Many desert plants als stre water in their leaves. Trpical rain frest plants live in lw light envirnments, under the canpy f taller trees. Their dark clr and large size gathers as much light as pssible. These leaves als have a waxy cating t repel water. Aquatic plants generally have very sft, delicate leaves as they d nt have t cntend with water shrtages. These leaves are usually very dark green since they gather light while under water. VII. Discussin Questins 1. What are the basic needs f a plant and hw d leaves help a plant meet thse needs? 2. Why are leaves generally green? 3. What d the sft, delicate leaves f aquatic plants suggest abut the habitat in which they live? Wuld yu expect t find them in pnds, slw rivers, r rushing creeks? 4. Hw d desert plants prtect themselves frm being eaten? 4 The Huntingtn Library, Art Cllectins, and Btanical Gardens

5 Observatin t Inference 5. Other than grwing larger and larger leaves, hw t trpical rain frest plants gather enugh light? 6. Did yur ideas abut the leaves change nce yu knew smething abut where they lived? The Huntingtn Library, Art Cllectins, and Btanical Gardens 5

6 Observatin t Inference Vcabulary Vcabulary abitic adaptatin bitic climate envirnment habitat nutrient phtsynthesis nnliving, as ppsed t bilgical r bitic a change in plants and animals ver many generatins in respnse t envirnmental cnditins the living factrs f an envirnment the temperature, humidity, precipitatin, light, wind, and ther weather nrmal in an area cnditins; all the cnditins arund a plant r an animal, such as, amunt f space in which t live, climate, ther plants and animals, etc. the natural envirnment in which a plant r animal lives a necessary ingredient fr a plant s grwth and survival, such as, nitrgen r ptassium the prcess in plants by which the sun s energy (light energy) is captured by chlrphyll and cnverted t chemical energy that is stred in sugars, by cmbining carbn dixide (CO 2 ) and water (H 2 O) t make sugars (C 6 ) and release xygen (O 2 ): 6CO 2 + 6H 2 O + light energy > C 6 + 6O 2 respiratin stma (pl. stmata) the prcess in living rganisms by which sugars (C 6 ) are cmbined with xygen (O 2 ) t frm carbn dixide (CO 2 ) and water (H 2 O), and t release energy fr the rganisms use in grwth, etc.: C O 2 > 6CO 2 + 6H 2 O + energy a very small pre in the surface f a leaf (xygen and carbn dixide frm the air enter thrugh the stmata; xygen, carbn dixide, and water vapr leave thrugh the stmata) 6 The Huntingtn Library, Art Cllectins, and Btanical Gardens

7 Learning frm Leaves: Frm Observatin t Inference Name: Date: Observatins Size Observatin t Inference Wrksheet Leaf 1 Leaf 2 Leaf 3 Clr Shape Texture Envirnmental Cnditins Desert Wetland Trpical Rain Frest Light Air Water Nutrients Envirnment Adaptatins t Envirnment: Light Air Water Nutrients Leaf 1 Leaf 2 Leaf 3 The Huntingtn Library, Art Cllectins, and Btanical Gardens 7