Topic: Causes and significance of genetic variation

Target group

8th‑grade students of elementary school

Core curriculum

General requirements

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

2. explains biological phenomena and processes occurring in selected organisms and in the environment.

Specific requirements

VIII. Threats to biodiversity. Pupil:

1. presents the essence of biodiversity.

General aim of education

The student will learn the main causes of genetic variability of organisms

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• explain what it causes and significance of genetic variation.

Methods/techniques

• expository

  • talk.

• activating

  • discussion.

• exposing

  • exposition.

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

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

Realization

• The teacher asks students to read the abstract themselves, paying particular attention to the illustrations.

• The teacher introduces the concept of genetic variability and explains that it is herited variability. Explains to students that the causes of genetic variability are: independent propagation of chromosomes to gametes; genetic recombination; random joining of gametes; mutations in the germ cells.

• The teacher introduces students to the case of a peppered moth, presenting an interactive illustration about this moth. The instructor explains that a typically colored specimen of this species has bright wings in a pattern that makes it look like birch bark or light lichen in a tree. In an environment heavily polluted by industry, where trees are usually darker (extinction of lichens, soot deposition on trunks), dark‑colored individuals turn out to be better adapted. Due to genetic variation within this species, the species can survive the changing environmental characteristics, although the least‑favored individuals die (standing out against the background of tree trunks and thus visible to the birds feeding on them).

• The leader encourages to give other examples of organisms among which there is genetic variability that allows to adapt to various environmental conditions (eg people who, due to different skin color, adapt to conditions of different insolation, wild animals whose species or populations living in circumpolar regions are characterized by bright fur, etc.).

• Students perform exercises and commands. The teacher checks and supplements the answers, providing students with the necessary information. Provides feedback..

Summary

• The teacher briefly presents the most important issues discussed in class. He answers the additional questions of the proteges and explains all their doubts. Students complete notes.

• 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.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Causes and significance of genetic variation

Children are similar to their parents. Siblings also have many common features. In addition to the similarities, each member of the family has individual characteristics that do not appear among his relatives. When all human populations are observed, it can be seen that within some of them people are more similar to each other than in others. For example, the ethnic Swedes are very homogeneous. A population much more diverse than the Swedish population is, for example, the population of the United States of America, which was formed by the Native Americans and emigrants from all continents. This diversity of traits within the population and, more broadly, the species – is called genetic variability. Therefore, we will say that the variability in the population of Swedes is smaller than in the population of Americans.

There are several reasons why even closely related organisms show genetic variation, that is, they differ from each other by some features. These are:

• independent spread of chromosomes to gametes; take into account only three pairs of chromosomes; during the meiotic division, there are 4 gametes, but there are 8 possible combinations of allocation of only 3 chromosomes; in the case of people who have 23 pairs of chromosomes, theoretically every man and every woman can produce more than 8 million types of gametes;

• genetic recombination, taking place during the meiotic division; it is based on the fact that homologous chromosomes separeiting into the gametes, which within the pairs exchanged genetic material among themselves, so they differ from the chromosomes of the previous generation; such a process of exchanging genetic material occurs with each meiotic division;

• random combination of gametes is an extra factor of genetic variability, causing that a couple of parents can have offspring with different genotypes;

• mutations occurring in the sex cells.

Features subject to genetic variation are inherited. Due to variability, the individuals forming the species differ from each other. Because individuals have different characteristics, the chance that some of these individuals will survive the changing environmental conditions is greater than if all individuals were the same. Individuals better adapted to the new conditions give their offspring traits that allowed them to survive. Therefore, despite the death of individual individuals, the species still exists.

• The source of genetic variability is the process of gamete formation, random merging with each other and mutations.