Topic: Judgment over the tapeworm

Target group

6th‑grade student of elementary school.

Core curriculum

7. Diversity and unity of the animal world:

3) Flatworms. Student:

a) presents the environment and lifestyle of flatworms,

b) observes representatives of flatworms (photos, films, graphs, etc.) and presents the common features of this group of animals,

c) shows the connection between the morphological structure of tapeworms and their parasitic lifestyle,

d) presents the routes of parasitic flatworms invasion and discusses ways of preventing diseases caused by selected parasites (armed tapeworm and unarmed tapeworm),

e) explains the meaning of flatworms in nature and for humans.

Lesson objectives

Students describe the routes of invasion of tapeworms, their vital functions and significance.

The criteria for success

• you will recognise the pork tapeworm and beef tapeworm in a photograph, and you will list their vital functions;

• you will list three methods of protection against tapeworm infection.

Key competences

• communication in the mother tongue;

• communication in foreign languages;

• mathematical competence and basic competences in science and technology; 

• digital competence;

• learning to learn;

• social and civic competences.

Methods/forms of work

Exposition, alternative observation, working with text.

Individual activity and activity in pairs.

Teaching aids

• abstract;

• interactive whiteboard or traditional blackboard;

• tablets/computers;

• sheets of paper with human digestive system to be coloured;

• crayons.

Lesson plan overview

Introduction

The teacher informs students that during the lesson they will learn about the body structure and development cycle of tapeworms. The teacher specifies the subject and the objective of the lesson as well as the criteria for success.

Realization

1. The teacher presents and discusses the interactive illustration „Armed tapeworm”. He then divides the students into groups and recommends that each of them carry out an in‑depth analysis of one of the points presented in the diagram, based on available sources of information (e.g. internet, atlas or encyclopedia). Students present the results of work in groups. Each team ends their presentation with the wording of the conclusions

2. Students make notes about the possibility of being infected with a tapeworm and its adaptations to parasitism.

3. The teacher gives the students sheets of paper with the human digestive system diagram and crayons. Students indicate the location of the tapeworm in the human digestive system, colour the sections and label them (small intestine, large intestine, rectum).

4. The teacher discusses the methods of protection against tapeworm infection.

5. Students do interactive exercise no. 1.

Summary

1. The teacher asks the students to list the vital functions of a tapeworm. The teacher asks in what situation a human can become its intermediate host.

2. The teacher asks the students how they evaluate the skills acquired during the lesson, what helped them learn during the classes and what hindered.

Homework

Carry out tasks number 5.1.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Flatworms, tapeworms, parasitic worms

Research shows that 80% of people in Poland are hosts of at least one parasitic worm. Every seventh Pole has a human roundworm, and every twelfth – tapeworm. Undesirable tenants usually settle with the owners of dogs and cats.

Flatworms have elongated, wormlike body with a head barely distinguished from the body. They are bilaterally symmetrical and strongly flattened dorsoventrally. Among the flatworms, there may be species that are free‑living, such as a planarian, which is a predator that lives in fresh waters. The vast majority of flatworms representatives are internal parasites of animals, including humans. A parasite is an organism that uses the body of another organism, the so‑called host, as a living environment and a source of nutrition – it feeds on the food the host has digested. Being inside the host's body, it poisons the host with its excretory products. When parasites occur in large quantities, they can cause devastation and even death of the host. An example of internal parasites are tapeworms.

We currently know over 3 thousand species of tapeworms. All without exception live at the expense of other organisms in their interiors (at least periodically). They are perfectly adapted to the parasitic mode of life. At the front of the tapeworm body, on the scolex, there are clasping organs: bothridium (suckers) or hooks, or both. With them, the tapeworm anchors in the host's intestine. Just behind the scolex is a short section called neck. Its task is to produce proglottids, the essential elements of building the body of a flatworm. The further from the neck, the older the proglottids are. Mature proglottids are filled with eggs. Thanks to the dorsoventral flattening of the body, even a ten‑meter tapeworm can be housed in the host's intestine.

The tapeworms do not have a digestive system or a mouth. They do not need them because they are immersed in the nutrition filling the intestine and absorb nutrients with the entire surface of their body. They do not have respiratory organs, because they live in an oxygen‑poor environment, and their life energy comes mainly from anaerobic respiration. They are protected against the effects of digestive fluids by a thick cuticle.

Flatworms are most commonly hermaphrodites – animals of both sexes that produce both ovum and sperm. They usually undergo complex development in which the larval forms occur. A few hosts are needed for the development. Larvae live inside intermediate hosts, and adults in the body definitive host.

In the case of a pork tapeworm and a beef tapeworm, the definitive host is a human. The intermediate hosts for a pork tapeworm is – a pig, and for a beef tapeworm – a cow. Fertilization of tapeworm eggs occurs in the mature proglottids of the tapeworm that lives inside the human body. After detaching themselves from the rest of the tapeworm’s body, these proglottids escape to the external environment with the faeces of the definitive host. The intermediate host is infected by ingesting contaminated water or grass. Inside the host's body, a larva hatches from the egg, and goes from the intestine to the blood vessels, then flows in them to the muscles, where it settles, transforming into a cysticercus. It is a bubble with a diameter of a few millimeters, filled with the liquid in which the tapeworm’s scolex is located. A human gets infected by eating raw or undercooked meat containing cysticercus. In the human intestine, the cysticercus’ vesicular walls are digested, and the tapeworm’s scolex attaches itself to the intestinal wall and transforms into an adult tapeworm, adding further proglottids. Soon they are able to produce new eggs.

• Flatworms are worms with elongated, flattened dorsoventrally, segmented or non‑segmented body. These include internal animal parasites (tapeworms) and free‑living species.

• Flatworms undergo a complex development with a change of host. Larvae live inside the body of an intermediate host, and adult forms of parasites live in the definitive host.

• Adaptations of internal parasites to their mode of life consist, among others, in a very high fertility, reduction of sensory organs, immunity to digestive fluids, the ability to respirate anaerobically.