Topic: What helps fish swim?

Target group

4th‑grade students of elementary school

Core curriculum

General aim of education

Pupils describe the adaptation of fish to life in water.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• compare the resistance put up by air and water;

• explain the importance of the streamlined shape of fish;

• explain the importance of the bladder.

Methods/techniques

• expository

  • talk.

• activating

  • discussion.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers;

• items needed to carry out the „Experiment 1”: two identical coins (e.g., fifty‑eighty), a tall glass container;

• carp bladder;

• items needed to carry out the „Experiment 2”: a small screwed glass jar or a glass screwed bottle and a large, large container (eg a tall vase, an aquarium, a bucket, etc.).

Lesson plan overview

Before classes

• Students get acquainted with the content of the abstract. They prepare to work on the lesson in such a way to be able to summarize the material read in their own words and solve the tasks themselves.

• Students perform Task 1.

Introduction

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

Realization

• The teacher asks pupils to read the fragment titled „Characteristics of fish” and wrote on the board the features of the fish's body structure, which result from their adaptation to life in water.

• The students perform Experiment 1, write in notebooks observations and conclusions.

• The teacher together with the students discuss the home‑made experience illustrating the relationship between shape and resistance. He or she asks students to read a research question, hypothesis and then observations and conclusions. If the students had difficulty with their correct formulation, the teacher again discusses the experiment and together with the students analyze it..

• The teacher demonstrates the carp's bladder, the pupils determine its properties.

• Students perform in the „Experiment 2” pairs and explain the role of the swim bladder.

Summary

• The teacher asks students to carry out the recommended interactive exercise themselves.

Homework

• Listen to the abstract recording at home. Pay attention to pronunciation, accent and intonation. Learn to pronounce the words learned during the lesson.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

What helps fish swim?

Fish are vertebrates which have adapted to living in water. They swim in the water with the help of fins and appropriate body movements. The driving body of fish is their tail, which ends in a caudal fin. In turn, the remaining fins are used to maintain the correct direction of movement and a suitable position. Fishes' skin is covered in scales and numerous mucus‑producing glands, which reduce friction when moving in water. Many species of fish have a swim bladder inside their bodies. This is a membraneous sack filled with gas. Because of this, the fish is able to swim at any depth.

Fish spend their whole lives in water and move around in it without any problems. Does it come easily to all organisms? Those of us who have been to the sea or a lake know that running is different in wet sand, different in knee‑deep water, and in turn, running in waist‑deep water is almost impossible. Now we can do some experiments to demonstrate the differences between air and water resistance.

When swimming, fish must overcome water resistance. However, the same laws affect all mediums, for example air. It is worth noting that both birds and planes, which reach considerable speeds during flight, have a streamlined body shape (or hull) and a long forward‑facing beak. Moving in water is similar, however water puts up more resistance than air. This is why elongated, spindle‑shaped objects move more easily in water. This means a narrow, elongated front, which widens in the middle, and narrows towards the back. Think about what shape most fish are, as well as the shape of kayaks, boats, yachts, ships or submarines. To confirm this, carry out the following experiment.

Not all fish have a streamlined body shape, which is why they can't swim fast. For example, it is hard to call seahorses good swimmers. However, the shape of their bodies camouflages them perfectly when they hide among underwater plants. The ability to swim fast is therefore not needed.

„A body immersed in water experiences an apparent loss in weight that is equal to the weight of the fluid displaced by it”. For this reason, fish immersed in water, when compared to land animals, are „lighter” by the weight of the displaced water. This is why the biggest and heaviest animals known to us can live in the seas and oceans. Fish, just like people or ships, are heavier than water, but don't sink in it. They can also swim on its surface or dive deeply.

The deeper a fish dives, the greater the pressure it experiences from the weight of the water surrounding it. To be able to balance out this pressure and swim at different depths, fish are equipped with a swim bladder. It is in the form of a chamber, which, when required, fills itself with gas. Then, the fish swims up, closer to the surface. We can understand this better by carrying out an experiment.

• Water puts up greater resistance to moving objects than air.

• Objects with a streamlined shape move faster in air and in water.

• The swim bladder makes it possible for fish to balance out water pressure, which makes it easier for them to move in water.