Topic: Food chain and food web

Supplementary material for use in lessons in the group of natural sciences (nature, biology, chemistry, geography, physics), additional classes, science clubs. It can serve as a resource for expanding knowledge, preparing students for science competitions.

Target group

8th‑grade students of elementary school

Core curriculum

Grade VIII – biology
VII. Ecology and environmental protection. Pupil:
5) presents the trophic structure of the ecosystem, distinguishes producers, consumers (I and further rows) and destructors and presents their role in the circulation of matter and energy flow through the ecosystem;
6) analyzes food dependencies (food chains and trophic networks), constructs simple food chains (chains of joining) and analyzes the presented (in the form of a diagram) networks and food chains.

General aim of education

Students present nutritional dependencies between terrestrial organisms.

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• to distinguish self‑nutrition from parasitic;

• indicate producers and consumers in their environment;

• discuss the role of detritivores in nature;

• define the term „food chain”.

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;

• cards with names of various species of organisms that form the food web;

• pieces of string;

• scissors;

• cards in three colors with the names of different species of organisms forming food chains, consisting of three links: green cards - with the producer's generic names; brown cards - with species names of consumers‑herbivores; red cards - with species names of consumers‑predators. Strings should be attached to all sheets: green and red cards, one for brown sheets, two for each.

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.

Introduction

• The teacher explains the aim of the lesson and together with students determines the success criteria to be achieved.

Realization

• The teacher instructs the pupils to familiarize themselves with the content of the abstract and write in the notebook explanations of the terms: „producer”, „consumer” and „destruent”. Then it displays the selected definition, and the indicated students give the term to which the presented definition refers.

• Students explain the concept of the food chain and discuss the differences between the first‑order consumer, the second‑order consumer and the third‑order consumer.

• Students draw colorful cards with species names of organisms. Their task is to create from the sheets models of food chains consisting of three links: the producer (green cards), the consumer‑herbivores (brown cards) and the consumer‑predator (red cards). Each student checks what species names of organisms are on the pages of colleagues and after finding that specific organisms can enter into a system of food dependencies, together with colleagues, combine pages using strings attached to them. Next, the students describe in their notebooks the food chain models created in this way. The teacher monitors students' work, corrects possible mistakes.

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

• Students draw cards with names of different species of organisms forming the food network and receive a few pieces of string. They check what names are on the cards of colleagues and after finding that selected organisms can combine food dependencies, gently bind their palms with the palms of their colleagues using a string (leaving behind it the longest possible episode so that each student can connect with many people at once ). After completing the task, each student determines his / her role in the food chain model created by the whole class. Then the students explain the concept of the food web and write its definition in notebooks.

• Participants familiarize themselves with the content presented in the interactive illustration. Then the teacher discusses the issues with the students.

Summary

• At the end of the class, the teacher asks the students questions:

  • What did you find important and interesting in class?

  • What was easy and what was difficult?

  • How can you use the knowledge and skills you have gained today?

  Willing/selected students summarize the lesson.

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

Food chain and food web

Plants produce the substances they need to live themselves – we call them producers. We also say that they are self‑sufficient.

Animals are unable to produce food, so they must eat other organisms – they are heterotrophic. That is why they are called consumers. Most animals eat plants. Herbivores are called primary consumers, which means that they feed on producers. In turn predators or scavengers feed on other heterotrophic organisms – they are called secondary consumers. It is possible, however, that such a carnivore devours another predator. We call them tertiary consumers.
Note that producers and consumers dependent on them can be ordered in a chain where the previous organism is devoured by the next. This series is called a food chain. In the chain consisting of grass, grasshopper, lizard and stork, each organism is the next link in the chain. Grass is a producer, a herbivorous grasshopper is the primary consumer, an insectivorous lizard eating a grasshopper is a secondary consumer, and a stork eating a lizard is a tertiary consumer.

Often a herbivore eats various plant species, and can itself fall victim to various carnivores, which often also hunt each other. Connecting and crossing food chains form a food web. It is a complex system of dependencies between a huge number of organisms. Destroying even one link can affect the balance of the entire network. For example, if we were to eliminate all the flies and mosquitoes we disliked, then the swallows feeding on these insects would disappear as well as the frogs and small fish feeding on the larvae. Their deficiency would cause the deaths of storks and herons, and reducing the number of these birds would contribute to a sharp increase in the number of mice, shrews and voles. These are just some of the possible consequences of destroying the food web link; changes would probably be much more widespread.

An important element of the environment are organisms called detritivores. They include, for example, fungi and numerous bacteria that decompose the remains of plants, animals and their excrement. As a result of their activity organic matter is transformed into simple mineral compounds. They return to the environment and can be reused by plants. Detritivores we do not take into account in food networks, because they can feed on the remains of every organism. It is worth remembering that they can also provide food for different animals.

And where to put the parasites in the chain or food web? After all, they do not always kill their host! They are, however, consumers. If the parasite lives at the expense of a plant, it is a primary consumer, and if at the expense of the animal – it can be considered a secondary consumer.

• Plants that are self‑nutrition organisms are producers.

• All animals are heterotrophic, that is, they are consumers.

• The food chain is a representation of the nutritional dependence in which the organism being the next link in the chain feeds on the organism preceding it.