Topic: Characteristics of protists

Author: Elżbieta Szedzianis

Target group

Students of the 5th grade of an elementary school.

Core curriculum

4 . Protists - organisms with a variety of cellular structures. Student:

1 ) shows the diversity of protist structure (single‑cell, multicellular) on selected examples;

2 ) presents selected life activities of the protists (breathing, nutrition, reproduction);

3 ) assumes protista breeding and microscopic observation of protists.

The general aim of education

The students characterize protists.

Criteria of success

● You will name five elements that make up the characteristics of organisms;

● you will characterize protists.

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; Kugellager (ball bearing), work with text.

Individual work, work in pairs.

Teaching aids

● abstract;

● interactive or traditional board;

● tablets/computers;

● work cards;

● cards with questions about the content of the abstract.

Lesson plan overview (Process)

Before the lesson, the students will watch the animation entitled „Structure and life activities of a paramecium”. In particular, they have to pay attention to the life environment of a paramecium, its structure and life activities.

Introduction

1. The teacher gives the topic, the goals of the lesson in a language understandable for the student, and the criteria of success.

2. The teacher reminds the homework and asks the students the following questions: Where does the paramecium occur? How does it eat? What is its meaning in the environment?

3. The teacher explains the aim of the lesson and the success criteria to be achieved by the students.

Realization

1. The teacher explains that the students will learn to characterize organisms on this lesson. The teacher provides the structure of the characteristics of organisms:

a. The life environment of an organism or a group of organisms.

b. Systematic affiliation.

c. External structure.

d. Life activities.

e. Representatives of this group and their brief descriptions.

f. The meaning of the characterized organisms in nature.

The teacher displays the elements of the characteristics on the screen or displays them on a poster. The teacher informs that protists will be the characterized group of organisms. The teacher distributes work cards containing the organism characterization plan to every student.

2. The teacher explains how the students will learn about protists:

a. in the first stage of work, the students will draw cards with questions that are to be answered by finding the information in the abstract.

Examples of questions:

1. What organisms are called protists?

2. How is a protist cell built on the example of a paramecium?

3. What do the terms plant protists and animal protists mean?

4. What environment do protists live in?

5. How does a euglena eat?

6. How does a paramecium eat?

7. How do a euglena and a paramecium breathe?

8. What is the role of a pulsating vacuole?

9. How do a paramecium and a euglena reproduce?

10. How do protists move?

11. What is the role of protists in water reservoirs?

12. What diseases do protists trigger?

b. Then, the students will learn to answer a drawn question in a way so that they can share this knowledge with other students. Using the Kugellager method, the students will share their knowledge with others, and after completing the Kugellager round they will characterize the protists on the work cards provided to them earlier.

The Kugellager is a method of work based on mutual learning. An even number of participants is required. The students are divided into two groups (6‑8 people). Each student has a different amount of knowledge to share with a friend. The students arrange themselves in two concentric circles. They stand in pairs opposite each other and give each other information. The student who listens, writes the obtained information in the work card at the appropriate protist characteristic element. In a 28‑student class there will be two ball bearings, each with 7+7 people.

3. The students work with text (including graphics and multimedia) and prepare to share knowledge.

4. They form a bearing (two circles), provide information to friends, write down new one. They relocate by 1 and exchange information with another person.

5. After the round, they return to their desks and finish or supplement the characteristics of the protists.

Summary

1. The teacher asks the students about the information contained in their characteristics.

2. The teacher asks the indicated students to read the content of the next points of the characteristic. The teacher provides feedback on texts being read.

3. The teacher asks the students to use traffic lights to assess how well they have mastered their ability to characterize organisms.

Homework for keen students.

Do interactive exercises 1 and 2 or 3.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Protists

Protists is the name of organisms that are neither bacteria nor fungi, nor plants or animals. So what are they and what distinguishes them? Protists are an artificially created group of weakly related organisms. There is evidence that protists lived on Earth 600 million years ago. Some probably gave rise to animals and fungi.

The classification of protists causes biologists a lot of trouble. It is difficult to determine their characteristics, because they are very diverse and weakly related organisms. Most of them are microscopic single‑celled organisms, like Paramecium or diatoms, some of them, form clusters known as colonies. Among the protists there are also multicellular organisms, the length of which exceeds several dozen metres, such as a Laminaria.

Most of the protists live in water. Many of them are autotrophic algae inhabiting the oceans, ponds and lakes. These algae can also be found on land, but only where there is a lot of moisture. Their cells resemble plant cells, which is why they are called plant protists.

Heterotrophic protists – protozoa live in coastal waters, in moist soil or on fallen leaves. Some are predators hunting for microscopic prey, others prey on the bottom of tanks in dead debris forming silt. Still others parasite in organisms larger than themselves. The life style and body structure of protozoa caused that nowadays they are called animal protists.

A unique protist is a single‑celled euglena that changes its diet depending on food availability and lighting conditions. It can be autotrophic or heterotrophic.

Paramecium is an agile protozoan that lives in puddles and shallow ponds. Its body consists of just one cell that fulfills all life activities that can be observed in multicellular organisms. Paramecium moves with the help of wavy cilia, densely covering the cell membrane. It feeds on plant debris and bacteria, which it absorbs by means of a cell membrane cavity. At the bottom of the cavity, the food particles are surrounded by a cell membrane that forms vesicles called vacuoles. Food vacuoles first digest food found in them, and then, in a specific place of the body, connect to the cell membrane, remove undigested debris outside the cell. Paramecium breathes, collecting oxygen with the entire surface of its body. In its cytoplasm mitochondria are present, in which energy is released from nutrients. To regulate the amount of water and excretion of unnecessary and toxic substances, it is used by pulsating vacuoles, which relax and contract, expelling the fluid outside the body. Paramecium has two cell nuclei. The macronucleus controls life processes and the micronucleus participates in reproduction. Paramecium reproduces mainly by cell division.

Euglena is an amazing single‑celled organism with a dual lifestyle. It is found in ponds, puddles and lakes. Thanks to the fact that it has chloroplasts, it can be autotrophic. Most often, however, it is a predator hunting for bacteria or a saprobiont that feeds on plant debris. It digests the collected food in the same way as Paramecium, in vacuoles that are formed in the hollow of the body. Thanks to the photoreceptor, it reacts to light, and when it lacks food, it moves to illuminated places with a long flagella. The flexible cell coat allows it to change the shape while overcoming obstacles. Unnecessary metabolic products and excess water are released from the cell via pulsating vacuola vacuums. It reproduces through the longitudinal division of the cell.

Single‑cell diatoms can occur individually or form colonies. Their cells look like carved boxes. The rigid cell wall, containing a lot of silica, forms a shell composed of a lid and a bottom. The appearance of the cell wall is a characteristic feature of the species. Diatoms are autotrophic, they live in fresh and salt waters. They float in water or settle at the bottom of water reservoirs, covering the stones with golden‑brown tarnum.

Protozoa have the ability to actively move. Some of them move with the help of long flagella (euglena), others use thousands of short and thickly distributed cilia (Paramecium) for movement. Still others crawl to form cytoplasmic protrusions of undefined shape. These include amoebas, for example. They are freshwater protozoa taking different shapes. They move with the use of pseudopodia, which also serve to gain food. They feed on smaller microorganisms, e.g. bacteria.

Single‑celled plant and animal protists are a component of plankton that floats on the surface of the water. Plankton, along with algae inhabiting water reservoirs, provides food for fish and other animals living in this environment. Autotrophic protists enrich water with oxygen, producing it during photosynthesis.

Heterotrophic protists together with bacteria and fungi break down the remains of plants and animals and contribute to the circulation of matter on Earth. Some species of protists inhabit the gut of termites and herbivorous animals. They help them digest food containing hard to decompose cellulose.

Among the parasitic single‑cell protists there are species that cause human diseases. Ameba causes a dangerous disease called dysentery. Trichomonas vaginalis is the cause of sexually transmitted disease - trichomoniasis. Toxoplasma causes toxoplasmosis - a disease particularly dangerous to the developing fetus. One can get infected from cats and other domestic animals. Malaria transmitted by mosquitoes of the Anopheles maculipennis causes malaria, a disease often occurring among people living in the tropic zone. Trypanosoma brucei transmitted by the tse‑tse fly is the cause of African coma.

• Protists are a diverse group of nuclear organisms with single‑cell, colony or multicellular structure.

• Autotrophic protista are named algae.

• The cells of heterotrophic protists show similarity to the cells of animals.

• Euglena is a unique protist which, depending on the access to light and food resources, can be an autotrophic or heterotrophic organism.

• Protists play an important role in nature as producers, saprobionts and parasites.

• Single‑cell protists played an important role in the processes of building the earth's crust.