Temat: Glony

Autor: Elżbieta Szedzianis

Adresat

Uczeń klasy V szkoły podstawowej.

Podstawa programowa

4. Protisty – organizmy o różnorodnej budowie komórkowej. Uczeń:

1) wykazuje różnorodność budowy protistów (jednokomórkowe, wielokomórkowe) na wybranych przykładach,

2) przedstawia wybrane czynności życiowe protistów (oddychanie, odżywianie, rozmnażanie).

Cel lekcji

Uczniowie charakteryzują glony.

Kryteria sukcesu

• podasz trzy cechy wspólne dla glonów,

• odróżnisz glony od innych organizmów,

• na podstawie obserwacji wskażesz trzy cechy przystosowujące glony do życia w wodzie.

Kompetencje kluczowe

• porozumiewanie się w językach obcych;

• porozumiewanie się w języku ojczystym;

• umiejętność uczenia się.

Metody/formy pracy

Pogadanka, metoda laboratoryjna, praca z tekstem i filmem.

Praca indywidualna, praca grupach.

Środki dydaktyczne

• abstrakt;

• tablica interaktywna lub tradycyjna;

• tablety/komputery;

• namoczone w wodzie okazy morszczynu;

• kuwety.

Fazy lekcji

Wstępna

1. Nauczyciel wyjaśnia, na czym będzie polegała lekcja i jakie kryteria sukcesu powinni osiągnąć uczniowie.

Realizacyjna

1. Nauczyciel wyświetla na ekranie zdjęcia lub ilustracje różnych przedstawicieli glonów, np. listownicę, skrętnicę, chlorellę, euglenę, morszczyn, gronorosty, krasnorosty. Wyjaśnia, że glony oprócz chlorofilu mają inne barwniki potrzebne do fotosyntezy. Prosi uczniów, żeby wskazali wspólne cechy tych organizmów.

2. Uczniowie na podstawie własnych wypowiedzi (ew. korygowanych przez nauczyciela) zapisują w zeszytach trzy wspólne cechy glonów.

3. Nauczyciel prosi uczniów, żeby rozwiązali zadanie interaktywne 1.

4. Nauczyciel prosi uczniów, żeby, biorąc pod uwagę sposób odżywiania glonów, określili ich znaczenie w przyrodzie.

5. Nauczyciel prosi uczniów, żeby przeanalizowali Ilustrację „Rozmieszczenie glonów w morzu” (abstrakt) i wyjaśnili, w jaki sposób barwa glonów zależy od środowiska życia.

6. Nauczyciel dzieli klasę na grupy czteroosobowe, rozdaje każdej namoczone w wodzie morszczyny. Wyjaśnia, że będą obserwować glony i wskazywać przystosowania do życia w wodzie. Prosi, żeby opisali kształt ciała morszczynu i wyjaśnili, jaki ma on związek ze środowiskiem wodnym.  Uczniowie zapisują spostrzeżenia w tabeli.

Podsumowująca

1. Nauczyciel wyświetla na ekranie wybrane wizerunki glonów i innych organizmów i prosi uczniów, żeby określili, czy są one glonami, oraz uzasadnili swoją odpowiedź.

2. Wyświetla kryteria sukcesu ucznia i prosi, by każdy ocenił swoje osiągnięcia.

W tej lekcji zostaną użyte m.in. następujące pojęcia oraz nagrania

Pojęcia

Teksty i nagrania

Algae

Algae are a group of unrelated organisms whose common feature is the inhabitation of waters. Algae belong to three kingdoms. Cyanobacteria belongs to bacteria, diatoms and brown algae – to protists, green algae and red algae – to the plant kingdom.

Multicellular algae do not have specialized tissues or organs. Their body is called a thallus. It can reach even several dozen meters in length. Algae usually float in the water or live attached to the bottom in places where the light reaches in the amount which is sufficient for the algae present there.

Algae are autotrophic. In their cells there are chloroplasts containing chlorophyll and other dyes that facilitate the conduct of photosynthesis, as well as give them a characteristic color. The names of algae groups come from the dominant color of the cells: the green algae are green, the red algae are red, and the brown algae are yellow and brown. Products of photosynthesis run by algae are stored in cells as spare substances. The cell wall is made of cellulose.

Brown algae inhabit cool sea waters of the northern hemisphere. They have multi‑cellular thallus bodies, usually in the shape of elastic bands. In addition to chlorophyll, their cells also contain brown dyes.

The representative of this group is Fucus vesiculosus, which occurs, among others, in the Baltic Sea. A strong leathery pleated thallus resembles a terrestrial plant. It attaches to the ground with a disc‑shaped holdfast. Leaves‑like elements grow from stem‑like parts. They contain air‑filled bubbles that carry algae in the water. This facilitates the harvest of light, and in the event of breaking off – the movement of parts of the thallus and the settling in subsequent places.

Already in early spring, roadside ditches get covered with a green, dense, floating coat. These are clusters of filamentous algae – green algae. Most of them live in freshwater, but many species inhabit the sea. Only a few can be found on land. Aquatic green algae float on the surface as plankton or live attached to the bottom of the reservoir. Land species occur in humid places.

Green algae take different shapes. They may be in the form of long threads or spheres. The thallus of multicellular green algae is long and tapered or flat and branched, resembling organs of terrestrial plants.

Green algae reproduce sexually and asexually. Single‑celled algae,  Pleurococcus and chlorella reproduce by cell division. The thallus of multicellular algae, such as sea lettuce, is torn apart by movements of water or animals into fragments that give rise to new plants. Most green algae produce spores. During reproduction, algae produce gametes and release into water, where they are combined. After fertilization, a zygote is created, from which a new organism develops.

Red algae live mainly in the seas. Attached to underwater boulders in quiet places, safe from violent waves, they create a wonderful underwater landscape. Their delicate, lace‑like thalli wave and surrender to water movements. Red algae as autotrophic organisms contain chlorophyll, which is masked by red or blue dyes supporting the photosynthesis process. It gives them a characteristic red or purple color. Most species of red algae live at considerable depths, so additional dyes allow them to absorb the part of the light that has not been stopped by the water layer.

Green algae, red algae and brown algae inhabit seas in a specific order forced by the amount of light reaching the given depth. For light, water is a type of filter that stops part of it depending on the depth. The deeper, the less light reaches the plants. Green algae which grow shallowly use (like terrestrial plants) blue and red light. Algae living deeper support photosynthesis with additional dyes. Brown algae equipped with a yellow‑brown dye capture light of green and blue color. The green and blue light reaching the deepest is used by red algae. The depth to which the light penetrates depends on the transparency of the water, which is why algae grow in different depths in different reservoirs.

Algae are the largest oxygen producer on Earth. They are small, freely floating on the surface of water and they produce plant plankton (phytoplankton), the basic food of fish and other aquatic animals. Algae seated at the bottom of the reservoirs form vast, underwater meadows that are a refuge, a place of feeding and breeding of animals. Some species of red algae participate in building coral reefs. Dead algae falling down to the bottom are decomposed, and the mineral compounds contained in them fertilize water, enabling the development of subsequent generations of autotrophic organisms.

Man uses algae in various areas of life. In medicine, they are components of drugs recommended in diseases of the digestive system. Those that contain a lot of iodine are used in the treatment of thyroid diseases. In cosmetics industry, algae are used to make creams and face masks that moisturize the skin and improve its elasticity. Certain species of algae are used to obtain agar‑agar, a gelling substance used for the production of sweets, medicines, and as a base for the media on which bacteria are grown. In Japan and China, some species of algae are treated as a component of meals, and others used for fertilizing the soil.

It happens, however, that algae become cumbersome. Plankton green algae, growing excessively on the surface of water reservoirs, can create water efflorescence limiting the access of light to plants living in their deeper layers. This prevents the efficient course of photosynthesis in the water reservoir, causes a significant reduction in the amount of oxygen and contributes, among others, to mortality of fish.

• Multi‑cell algae do not produce tissues and do not have roots, stems and leaves.

• The bodies of brown, green and red algae take different shapes: from filamentous to ribbony, looking like leaves of terrestrial plants.

• Single‑cell, colonial and multi‑cell organisms are found among green algae.

• Red algae are mainly sea algae living at great depths.

• Different colours of algae are caused by the presence of additional dyes that support the process of photosynthesis, which takes place in water at various depths.

• Algae are the largest oxygen producer on the Earth.