Lesson plan (English)
Topic: External structure of a leaf
Author: Elżbieta Szedzianis
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 structure and function of leaves and their adaptation to fulfilling life functions and to the environment.
Criteria of success
You will observe the leaves and describe their external structure;
give 5 adaptations of leaves to perform vital life functions;
identify 3 plants based on leaves.
Key competences
communication in foreign languages;
mathematical competence and basic competences in science and technology;
learning to learn.
Methods / techniques
Conversation, direct and substitute observation, workshop observation, didactic game.
Individual work, work in groups.
Teaching aids
abstract;
interactive or traditional board;
tablets/computers;
pot plant showing shoot phototropism;
leaves of trees and shrubs signed with their specimen name;
modified leaves of, e.g. onion, aloes, insectivorous sundew, African violet.
Lesson plan overview (Process)
A few weeks before the lesson, the teacher places a pot plant on the window sill so that it bends to the light.
Introduction
1. The teacher shows the students the plant growing on the window sill with leaves facing the light. The teacher reverses it so that the students see the leaf mosaic. The teacher asks the students what environmental factor influenced such a reaction of the plant and what the result of this observation is.
2. The teacher explains that the aim of the lesson will be to observe the leaves and indicate their adaptation to fulfil their life functions.
3. The teacher gives the students the criteria of success.
Realization
4. The teacher divides the class into groups and gives them approximately 15 dried or fresh leaves of various plants. Among the leaves there are also needles. Each leaf has a label with the name. The teacher asks the pupils to group the leaves based on their external structure. Then, the teacher gives them a few pieces of paper with the sentence: „A criterion of division, that is a feature that the leaves of this group have, and the leaves of other groups do not. This feature is: ... „. The teacher asks the students to complete the sentence on the piece of paper.
5. When discussing the division of leaves, the students should use Illustration 1: „External structure of a leaf” and use the terms written on it when making the description.
6. The teacher asks the students to name as many features of the structure of leaves as possible and their position on the stem (in the previously shown pot plant and in the plants presented in the abstract. Illustration 7: „Position of leaves on a stem”) allowing to capture as much light as possible. The students write their observations in the table. The table has 3 columns:
a. environmental factor (which is given, for example, light, carbon dioxide, drought, low temperature, etc.);
b. external structure and arrangement of leaves;
c. How does this structure help?
The students continue to fill in the table in the work sheet, conducting direct observations, for example, leaves of onions, aloes, insectivorous sundew, leaf cuttings, e.g. African violet.
Summary
10. The teacher divides the students into teams of 5‑6 people. The teacher gives the names of 10 plants the leaves of which were observed by students at the beginning of the realization phase. The students place these leaves in front of them. Each student from the group secretly chooses one of the leaves. They play a game of 5 questions (based on a game of 20 questions). They ask such questions with the help of which they can determine the name of a given plant. When asking the questions, they must use the biological terminology they already know.
11. The students solve interactive task No. 1.
Homework for keen students.
The teacher explains that on the next lesson the students will prepare and role‑play a situation. The teacher asks them to prepare for the lesson and gives the students a description of the lesson.
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 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. przystosowanie 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 tkanek rośliny.
Texts and recordings
External structure of the leaf
Plants have a huge variety of leaves. They differ from each other with many characteristics, such as shape, size, and arrangement on the stem. A single leaf consists of:
leaf blade, which is usually thin, flat and has a large surface, which allows for the best use of light by the plant and conducting gas exchange (taking and expelling oxygen and carbon dioxide); in the blade there are the so‑called leaf nerves made of conductive and support tissue – they are a scaffolding for other leaf tissues and transport water and photosynthesis products;
leaf petiole, which connects the blade with the stem and keeps the leaf in the right position towards the light and absorbs wind gusts and drops of rain; some leaves do not have a petiole - they grow directly from the stem and are then called sesile leaves.
Leaves of individual groups of plants are characterized by a specific system of nerves, which can be used to classify plants. Some leaves have one main nerve from which smaller side nerves branch out – this arrangement is called pinnate nervature. In other plants, there are nerves of an equal thickness, arranged side by side. This is parallel nervature. However, the system in which the main nerves radiate from the base of the leaf is called palmate nervature.
Due to the structure of leaf blades, simple leaves and compound leaves are distinguished. Simple leaves have one blade and can take various shapes, e.g. ovate, heart‑shaped, kidney‑shaped, round, oval, and palmate. In the case of compound leaves, on one petiole there are several smaller leaves which can have a palmate shape, like a chestnut, or a pinnate shape – like a rowanberry.
The way leaves are planted on the stem results from the adaptation of plants to collecting light, protection against excessive solar radiation, violent rain or wind. This arrangement is called a leaf mosaic.
In addition to basic functions, leaves of various plants also perform other tasks to which they are adapted thanks to the modifications of their structure. These adaptations allow plants to survive in different environments, even with such extreme conditions as there are in deserts or Arctic regions. Leaves can have the following functions: storage, climbing, defensive, trap, and even participate in asexual reproduction.
Among modified leaves we distinguish:
storage leaves specialized in the storage of food substances or water; occur in plants forming bulbs such as: garlic, narcissus, tulip, hyacinth; internal leaves of onions are characterized by high thickness and fleshiness and well‑formed storage parenchyma, whereas external ones form protective husks; storage leaves that store water occur in plants that have adapted to living in conditions of draught and are equipped with water‑bearing tissues – such plants live mostly in deserts, although they are also found in all climate zones, for example, aloe vera, agave and stonecrop growing in Poland;
leaf tendrils found in climbing plants; these are touch sensitive organs and therefore wrap around supports; this way they enable a plant to climb to the light. They are formed as modifications of entire leaves or parts thereof; they are found, for example, in peas;
trap leaves present in all carnivorous plants and adapted to capture small animals, usually insects; traps formed from leaves have a variety of shapes and they look like jugs, flaps, pouches; the interior of the traps can be covered with mucus that holds insects or filled with liquid in which these insects melt; special glandular cells secrete enzymes that digest insect bodies – this way plants supplement minerals which are little in the soil, primarily nitrogen compounds; trap leaves are produced by sundew, Venus Flytraps, Nepenthes;
leaf thorns formed as a result of reducing the leaf area to reduce water loss; they grow directly from shoots; they do not carry out photosynthesis, so they do not have chlorophyll; they are rigid and sharp, thus protecting plants against being eaten by animals; leaf thorns are found, for example, in cacti.
The external structure of leaves is diverse however some elements are the same: leaf petiole, leaf blade with nervature, leaf base.
Leaves serve the plant for the processes of photosynthesis, gas exchange and transpiration.
The structure of the leaf indicates its very good adaptation to the functions it performs.