Lesson plan (English)
Topic: Functions of a leaf
Target group
Students of the 5th grade of an elementary school.
Core curriculum
Cele kształcenia – wymagania ogólne
I. Znajomość różnorodności biologicznej oraz podstawowych zjawisk i procesów biologicznych. Uczeń:
1. opisuje, porządkuje i rozpoznaje organizmy;
II. Planowanie i przeprowadzanie obserwacji oraz doświadczeń; wnioskowanie w oparciu o ich wyniki. Uczeń:
1. określa problem badawczy, formułuje hipotezy, planuje i przeprowadza oraz dokumentuje obserwacje i proste doświadczenia biologiczne;
2. określa warunki doświadczenia, rozróżnia próbę kontrolną i badawczą;
3. analizuje wyniki i formułuje wnioski;
4. przeprowadza obserwacje mikroskopowe i makroskopowe preparatów świeżych i trwałych.
III. Posługiwanie się informacjami pochodzącymi z analizy materiałów źródłowych. Uczeń:
1. wykorzystuje różnorodne źródła i metody pozyskiwania informacji;
IV. Rozumowanie i zastosowanie nabytej wiedzy do rozwiązywania problemów biologicznych. Uczeń:
1. interpretuje informacje i wyjaśnia zależności przyczynowo-skutkowe między zjawiskami, formułuje wnioski;
Treści nauczania – wymagania szczegółowe
II. Różnorodność życia.
1. Klasyfikacja organizmów. Uczeń:
3) rozpoznaje organizmy z najbliższego otoczenia, posługując się prostym kluczem do ich oznaczania.
5. Różnorodność i jedność roślin:
1) tkanki roślinne – uczeń dokonuje obserwacji i rozpoznaje (pod mikroskopem, na schemacie, na zdjęciu lub na podstawie opisu) tkanki roślinne oraz wskazuje ich cechy adaptacyjne do pełnienia określonych funkcji (tkanka twórcza, okrywająca, miękiszowa, wzmacniająca, przewodząca);
5) rośliny okrytonasienne – uczeń:
b) dokonuje obserwacji rośliny okrytonasiennej (zdjęcia, ryciny, okazy żywe); rozpoznaje jej organy i określa ich funkcje (korzeń, łodyga, liść, kwiat),
c) opisuje modyfikacje korzeni, łodyg i liści jako adaptacje roślin okrytonasiennych do życia w określonych środowiskach,
The general aim of education
The students describe the processes that occur in a leaf: photosynthesis and transpiration.
Criteria of success
You will name at least three elements of the leaf structure that take part in photosynthesis and transpiration;
explain the role of transpiration;
describe what happens in chloroplasts;
present the path of oxygen, carbon dioxide, water and sugar in a plant.
Key competences
communication in foreign languages;
communication in the mother tongue;
mathematical competence and basic competences in science and technology;
learning to learn.
Methods / techniques
Outdistance strategy; staging.
Work in groups.
Teaching aids
abstract;
interactive or traditional board;
tablets/computers;
description of the staging.
Lesson plan overview (Process)
Before the lesson, the teacher explains the students that they will take part in a staging illustrating the processes taking place in a leaf. They have to prepare for this: draw a scene, i.e. a leaf pattern, mark themselves with texts (ribbons) and parts of a leaf, learn their roles to perform a show. The teacher gives them cards with a description of the staging and warns that the roles will be drawn. The students will be able to have the texts to be said on cards.
Description of the staging.
The students draw a few‑meter leaf with chalk on the school playground or in the corridor with a wide (so wide that the students can cross it both ways) petiole and equally wide, but narrowing, veins at the end. The veins and the petiole are divided into two parts with colours, for example, blue - wood, and red - phloem. The names of both tissues and the chlorenchyma are signed, as well as the petiole and the veins. Additionally, in several areas of the leaf there are marked the stomata and the chloroplasts.
The students are divided into three nine‑person teams and draw cards that mark their roles in photosynthesis and transpiration. Each of the three groups will play the staging one by one. The students in the groups wear ribbons with names. These are: Water and Carbon Dioxide, which after transformation will become Sugar and Oxygen, Light, Chloroplasts 1‑3, Transpiration, Stomata 1‑2.
The students in the groups read their roles and plan to play them together. Then they practice.
Water: Stands at the beginning of the petiole and then enters the leaf and says: „I am liquid, I was in the soil when the root absorbed me and some unknown force sucked me up the plant through the wood tubes into the leaf. Now I have to find a chloroplast.” It follows the petiole wood and the vein towards the Chloroplast.
The transpiration standing next to the leaf says: „I am not an unknown force. My name is Transpiration and I am responsible for absorbing the water into the plant and excreting it outside into the atmosphere. I suck water into the root from the soil, where there is a lot of it, transport it using wood tubes to the stomata and release water vapour into the air in which there is little water. Along the way, many molecules of water are taken away by thirsty cells and chloroplasts that carry out the photosynthesis.”
Carbon dioxide: It stands next to Stoma and says: „I am gas, a component in the air, I was floating around the plant. Suddenly, I fell into the stoma in the leaf. Now I have to go to the Chloroplast.” It is going to the Chloroplast.
The Chloroplast is three people holding hands in green paper capes. The fourth person, the Light, in a yellow outfit, holds a flashlight in hand.
Chloroplast 1 says: „I am part of chloroplast. I have a green dye, chlorophyll. When the sun shines, I can produce food for the plant.”
Chloroplast 2 says: „Water and Carbon Dioxide are approaching us! We will start producing food.”
Chloroplast 3, when Water and Carbon Dioxide enter the chloroplast, says: „We will use the chlorophyll and the light to produce food.”
The light says as follows, shining on Water and Carbon Dioxide: „The energy of light in the presence of the chlorophyll will combine water with carbon dioxide.”
Water and Carbon Dioxide approach themselves, and after the flash of light they change their ribbons to ribbons saying Sugar and Oxygen.
Sugar says: „I am food, I nourish cells, I am going to feed them now. Now, along the phloem, I will go to the root, where there is much sugar accumulated. I will feed the cells along the way, and if they are full, I will sit in the root in the food storage.”
Oxygen spins around the chloroplast and says: „I will check if there is more oxygen nearby. If not enough - I have to stay in the leaf and help it to breathe. If there is enough - I have to go to Stoma and run to the air.” It is going towards Stoma.
Stoma 1 says: „I am a skin cell. When it is humid, I step away from my sister to open the stoma and let out the water vapour and oxygen.”
Stoma 2 says: „I am the second cell that forms the stoma. When it is dry, I get closer to my sister and close the stoma to keep the water in the leaf.”
Stoma 1 says: „But when we close the stoma, no carbon dioxide can enter the leaf and oxygen cannot go out. Then, the photosynthesis takes place poorly, and the plant grows slowly.”
Introduction
The teacher presents the topic and the criteria of success.
The teacher divides the class into groups of nine people. If there are students with no assignments, they can be entrusted the functions of directors and joined to the groups. The teacher conducts a draw which will determine the roles of the students and the order of the groups' performances. The teacher helps the students to prepare the scene, costumes, answer questions about the course of the staging, gives instructions, if necessary.
Realization
The students agree on their tasks in the groups, and they practice with the help of the directors.
The next groups stage the performances.
Summary
The teacher asks the students from particular groups how they evaluate their performance.
The teacher asks the students to finish the sentences:
The staging helped me to understand that...
During the staging I felt...The teacher gives homework: To consolidate the information about the structure of a leaf, at home I will read the content of the abstract, do the exercises and the described experiment. I will present the conclusion to the class.
The following terms and recordings will be used during this lesson
Terms
aparat szparkowy – wytwór skórki pędu; składa się z dwóch komórek szparkowych, między którymi znajduje się szparka – otwór, przez który zachodzi parowanie wody i wymiana gazowa.
blaszka liściowa – główna część liścia, najczęściej szeroka i płaska, przystosowana do prowadzenia procesu fotosyntezy.
liść – organ wegetatywny roślin, w którym zachodzą procesy fotosyntezy, wymiany gazowej i transpiracji (parowania); liście mogą być pojedyncze lub złożone.
miękisz asymilacyjny – tkanka miękiszowa zawierająca w komórkach dużą liczbę chloroplastów; bierze udział w fotosyntezie; występuje głównie w liściach.
modyfikacje liści – przystosowania kształtu i tkankowej budowy liścia do pełnienia innych funkcji niż odżywianie; wyróżnia się m. in. przystosowania do rozmnażania, gromadzenia pokarmu i wody, obrony, chwytania organizmów, przetrwania w warunkach suszy.
siła ssąca liści – siła powstająca wskutek zachodzącej w liściach transpiracji; wymusza pobieranie wody z gleby i przewodzenie jej do liści.
transpiracja – proces wyparowywania wody przez liście, dzięki któremu w roślinie zapewniony jest stały przepływ wody od korzenia do liści; powoduje także obniżenie temperatury ciała rośliny.
Texts and recordings
Internal structure of the leaf
Both the external and the tissue structures of a leaf indicate that it is adapted for photosynthesis. Both surfaces of the leaf blade – upper and lower – are covered with a single‑layer, transparent epidermis, through which sun rays penetrate freely. Epidermis cells contain no chloroplasts. They are strictly adhering each other and are covered by a cuticle therefore they limit the evaporation of water and protect against penetration of pathogenic microorganisms.
The stomata usually occur in the lower epidermis and are made of two guard cells with a characteristic shape. Between them there is a stoma leading to the interior of a leaf. The intensity of gas exchange and transpiration, i.e. evaporation of water, depends on the degree of opening of the stomata. During water scarcity, the stomata go limp and close the stoma. Thus, the transpiration which could expose the plant to excessive water loss is limited. With the right amount of water, the cells regain their firmness, stretch and open the stoma. Then, transpiration and gas exchange are resumed.
The upper part of the leaf blade in most temperate climate plants is filled with long, cylindrical cells of the palisade parenchyma that closely adhere to each other. Their shape, arrangement in the leaf and the presence of a large number of chloroplasts make this tissue the main place where food is produced. Under the layer of the palisade parenchyma , in the lower part of the blade there is spongy parenchyma. Its cells are variously shaped, loosely arranged and have fewer chloroplasts than palisade parenchyma cells. The numerous and large intercellular spaces between them allow for the circulation of air and water vapour in the leaf. The largest air chambers occur above the stomata. The palisade parenchyma together with the spongy parenchyma form chlorenchyma.
The supply of a leaf with water and removal of photosynthesis products from it takes place through vascular bundles, being part of leaf nerves. Each bundle contains elements of wood and phloem. The wood supplies a leaf with water taken from the roots and delivered by the stem. The phloem discharges photosynthetic products from the chlorenchyma. The vascular bundles are often surrounded by a sheath built of support tissue stiffening the leaf blade.
Gas exchange connected with photosynthesis, respiration and transpiration processes is mainly carried out by stomata. Transpiration is responsible for the formation of the suction force of leaves, which causes the suction of water along with mineral salts from the soil through the root and forces it to be transported through the stem to other organs. What is more, transpiration protects the plant against overheating on hot days. This is because water must take heat from the environment in order to change into steam. Evaporation significantly lowers the temperature of leaves, just as sweat evaporation lowers the temperature of human skin. The intensity of transpiration depends on the size of the leaf surface, the number of stomata, ambient temperature, air humidity and light intensity.
Leaves serve the plant for the processes of photosynthesis, gas exchange and transpiration.
Transpiration allows the plant to absorb water from the soil.
The structure of the leaf indicates its very good adaptation to the functions it performs.