Topic: Competition and parasitism

Author: Leokadia Stalewicz

Target group

8th‑grade students of elementary school

Core curriculum

General requirements

I. Knowledge of biological diversity and basic biological phenomena and processes. Pupil:

3. presents and explains the relationship between the organism and the environment.

Specific requirements

VII. Ecology and environmental protection. Pupil:

3. analyzes antagonistic interactions: intra‑species and interspecies competition, parasitism, predation and herbivorousness.

General aim of education

You will learn what antagonistic relations and parasitism are

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• explain what interspecies competition consists of and give examples of it;

• distinguish intra‑species competition from interspecies;

• discuss examples of what parasitism is;

• describe the adaptation of organisms to parasitism;

• explain the influence of parasitism on the number of host populations.

Methods/techniques

• activating

  • discussion;

  • brainstorming.

• expository

  • talk.

• 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.

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

• Then he writes the subject of the lesson on the blackboard or interactive whiteboard. Students write it in notebooks..

• The teacher reminds the participants of the classes what subject area the lesson will concern.

• The teacher asks students to exchange all the parasites known to them. He asks about the ratio of the parasite to the host.

Realization

• The leader designates people who will discuss the following issues: inter‑species competition; intra‑species competition.

• After completing the students' statements, the teacher complements them by presenting and commenting on the materials „Inter‑species competition” and „Intra‑species competition” and resources from the „Competition” chapter in the abstract. The teacher also explains that competition belongs to antagonistic relationships.

• Working with the brainstorming method, students exchange species with which pigeons living in the city compete and resources being the subject of this competition.

• The teacher appoints people who will discuss the following topics: external parasites; internal parasites; adaptation to parasitism.

• After completing the students' statements, the teacher initiates a discussion about the impact of parasites on the number of host populations and the health of individuals affected by parasites.

Summary

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

• The teacher chooses one student by random method and asks him or her to explain in own words the meaning of a given word or concept learned during 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.

• Describe in the notebook the adaptation of the mosquito to parasitism.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Competition and parasitism

When two different species with similar life requirements live close to each other, they tend to compete for access to resources. Inter‑species competition is unfavourable to the organisms involved. It always ends in elimination of the weaker competitor: it either changes its place of residence, the manner of using the environment, or dies. For this reason, it's considered to be an antagonistic relationship. The effects of inter‑species competition might be the following: reducing the number of specimens in one species, its migration to less competitive areas, or a change in its needs.

Inter‑species competition takes place, for example, between hollow‑nesting species. An example of such species is black woodpecker. Due to the fact that a pair of woodpeckers usually prepares several hollows and uses only one of them for breeding, other bird species, such as owls, jackdaws and rollers, also find shelter in the tree trunks. These birds compete for hollows with each other, but also with bats, martens and even wasps.

Beech trees are strong competitors in the forest. Their roots emit substances into the soil, which make it impossible for other plants to germinate. For this reason, there is not much understory and ground cover vegetation in the beech forest. A similar mechanism is observed in the case of some fungi. The Penicillium fungi produces an antibiotic that prevents the development of bacterial colonies in their vicinity. This way, they protect their food supply.

In fields and in garden plant beds there is competition for space, light, water and mineral salts between the cultivated and wild plants, known as weeds. In neglected crops, weeds that grow intensively and produce huge quantities of seeds quickly overgrow and drown out their competitors.

Competition is the most intense among the specimens of the same species. Intra‑species competition is usually associated with animals. They get into fierce fights to gain access to females and having offspring. In the herds, the so‑called pecking order is established - the most important individuals in the herd satisfy their hunger first, and for the weaker ones there might not be enough food left. The competitors that have lost may leave their herd (living area) and look for better conditions elsewhere. If they fail there too, they die and leave no offspring that would also have the genes ensuring defeat rather than victory.

It is easiest to see the intra‑species competition in the forest, where same age spruce seedlings have been planted densely and at equal distances from each other. They are planted close together to limit the appearance of self‑crops from other trees and shrubs in between. It can be expected that around 500‑800 individuals, out of a total of around 4 000 individuals planted per hectare, will live to harvest. In production forests, plantings are protected against herbivores and pests, so the loss of trees will mainly be the result of intra‑species competition.

One of the antagonistic relationships between species is parasitism. A parasite lives permanently or temporarily at the expense of the victim, called a host. The victim of a parasite is its place of life and his source of food, so most parasites do not seek to kill the host. The death of a victim would be detrimental for the parasite. A parasite without food source either dies or needs to search for a new host. The effectiveness of parasitic lifestyle is proven by the fact that parasites are found in all groups of organisms.

External parasites of animals usually feed on blood, epidermis or feathers. They may be attached (permanently or temporarily) to the body of the host (e.g. a tick, a leech) or move freely (like lice and fleas). They are in constant contact with the outside world and can find a new host after the death of the current one. The parasites which feed on individuals of numerous and highly concentrated populations have the best living conditions. Some human parasites transmit diseases: anopheles - malaria, ticks - borreliosis or tick‑borne meningitis.

Internal parasites of animals may be present in different parts of the body. They are often found in the digestive system (e.g. pinworms, armed and unarmed tapeworm, human roundworm), where they feed mainly on the digestive content. However, some of them may live in internal organs - e.g. liver (liver fluke), duodenum, lungs, brain, skeletal muscles. Some internal parasites feed on blood or epithelium.

Internal parasites are much more host‑dependent than external parasites. The host suffers damage not only through loss of nutrient content or disruption of tissue continuity, but also through poisoning with harmful metabolic products of the parasite. Usually, when the host dies, his parasites die with him.

Many parasites feed on plants or inside them, e.g. pathogenic bacteria, soil nematodes, fungi and insects, stem rust, polypore, beetle larvae (grubs) and white cabbage butterfly larvae as well as larvae and adult aphids. There are also plants that are parasites themselves.

Parasites, like other organisms, have special adaptations necessary to lead their lifestyles and to gain food. In the case of animals that are external parasites, these may be specially converted organs for cutting or pricking the skin and drinking blood. In addition, some parasites, such as leeches, have chemicals that disable blot clotting in their saliva as well as anaesthetics that prevent the host from noticing the unwelcome guest immediately. Other parasites, such as head lice, have hooked legs that allow them to stay on the surface of the host's body even during very rapid movements. They have a solid body structure, thanks to which they are able to survive even scratching with claws or rubbing against bark of trees.

Internal parasites are provided with stable and safe living conditions. Their bodies are usually soft and elongated. They have no legs, but some have prehensile organs (e.g. hooks on the head of an armed tapeworm) to attach to the intestinal wall. In this way, the intestinal movements do not move the parasites towards the rectum, from where they can be removed along with the faeces.

• Inter‑species competition takes place between species that inhabit the same environment and have similar life needs.

• Inter‑species competition may result in the reduction of the number of specimens in one species, its migration to less competitive areas or a change in its needs.

• Parasites developed many specialized adaptations to their lifestyle and to their manner of obtaining food;

• Parasites cause and transmit many diseases and thus affect the number of specimens in the host population.