Secondary Science 11 to 16

A Practical Guide

Gren Ireson, Mark Crowley, Ruth Richards, John Twidle

• Publisher: SAGE Publications Ltd
• Year: 2010
• ISBN:
  9781446244944
• Edition: 1
• Topic: Education
• Subtopic: Teaching Science & Technology

Are you looking for teaching ideas to make your science lessons come alive?

Full of suggestions for exciting practical work to engage children, this book addresses and explains the science behind the experiments, and emphasises the need to engage the learner through minds-on activities. It shows you where to make links to the national curricula in England, Scotland, Wales and Northern Ireland, and it covers the three sciences: chemistry, biology and physics. The detailed subject knowledge helps you grasp key concepts, and there are lots of useful diagrams to illustrate important points.

Experiments include:

- extracting DNA from a kiwi fruit

- capturing rainbows

- the chromatography of sweets

- removing iron from cornflakes

- a plate tectonic jigsaw

These practical activities will provide you with ways to ensure your students respond enthusiastically to science, and the book will also help you develop your subject knowledge and ensure you meet your Qualified Teacher Status (QTS) standards. Perfect reading for Secondary Science PGCE students, as well as those on the Graduate Teacher Programme (GTP), this book is also ideal for non-specialists who are looking for support as they get to grips with the sciences.

Gren Ireson is Professor of Science Education at Nottingham Trent University. Mark Crowley is a Teaching Research Fellow in the Centre for Effective Learning in Science, Nottingham Trent University. Ruth Richards is Subject Strand Leader for the PGCE and Subject Knowledge Enhancement (SKE) courses in Science at Nottingham Trent University, and an examiner for A-level Geology. John Twidle is Subject Leader for the PGCE and MSc Science programmes at Loughborough University.

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Section 1

Beginnings and development of living things

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This section has a biological focus which should help to develop your understanding of a number of biological processes. In this section, of two chapters, you will be introduced to the science of:

• cells – the building blocks of living organisms;
• reproduction – the continuation of life; and
• genetics – the variation and inheritance of characteristics.

This links to, and will help you deliver, the various national curricula for England, Ireland, Scotland and Wales as set out below.

By working through this section it is expected that you will be able to describe and explain:

• the various functions of animal and plant cells;
• the process of reproduction;
• the process of genetic inheritance; and
• the passing on of characteristics.

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1	Looking at life
	Ruth Richards

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This chapter covers:

• the characteristics of life
• cell structure
• practical techniques for making slides
• levels of organization
• diffusion and osmosis.

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Test your own knowledge

Before reading the material in this chapter test your current knowledge with the following questions:

1. How do we know something is alive?
2. What is a cell? What are the main components of an animal and a plant cell? Which components are shared by both plant and animal cells?
3. What is the function of each cell component?
4. How do substances get in and out of cells? Are there any rules for this?
5. What is the definition of a cell, an organelle, a tissue and an organism?

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What is life?

Everything that is considered to be alive carries out the seven characteristics of life. These are known by the mnemonic MRS GREN (Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion and Nutrition). The following information can be used to construct a card sort for students to recap this topic from Key Stage 3:

• Movement: Organisms may move all or parts of their bodies towards or away from influences that are important to them. For example, a plant may move its leaves towards the sun.
• Respiration: The release of energy stored in food, such as glucose, to provide power for the cell to function. The energy currency of the cell is adenosine tri-phosphate, or ATP for short. Respiration takes place in the mitochondria of every cell.
• Sensitivity: Awareness of the organisms’ surroundings. This may be complex, such as the passage of nerve impulses, or simpler, such as the growth of plant roots down into the soil.
• Growth: An increase in size, such as the division of one cell into two identical cells (mitosis).
• Reproduction: The formation of more individuals from one parent (asexually) or two parents (sexually).
• Excretion: Getting rid of the products of the chemical reactions that have taken place in the organism (metabolism). Metabolism occurs at a cellular level, and so excretion includes getting rid of water and carbon dioxide. (Not getting rid of solid waste!)
• Nutrition: Using a food source to release energy for cell function. This is either autotrophic, when plants make their own food by photosynthesis and then metabolise it, or heterotrophic, when ready-made food is taken into an organism.

The cell

What is a cell? A cell is a single unit that can function on its own and can divide to form other cells of the same type. It is a package that contains all the ‘bits’ needed to be alive. These component parts of cells are called organelles. The cell itself is the basic unit of life, and all multicellular organisms are derived originally from one cell. It should be noted that animal cells are generally smaller than plant cells and lack some of the cell contents of plant cells.

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How science works

The cell was first discovered by Robert Hooke in 1665. He used a basic microscope to look at thin slices of cork (from a cork tree) and he saw boxes that reminded him of monks’ rooms or cells. Hence the name – ‘cell’.

A good way to get students to compare animal and plant cells is by using a Venn diagram. This helps assess prior learning and gives you the basis to discuss any misconceptions that the students may have.

Provide the students with a list of the cell components and ask them to categorize these as being present in animals only, plants only or in both animal and plant cells (a shared field in the centre). Students could be asked to extend this by underlining the components that cannot be seen by using an ordinary light microscope, such as the ones they may use in class.

The completed example is shown in Figure 1.1. The words underlined are those components that cannot be seen through a standard light microscope as used in schools.

Figure 1.1 Venn diagram comparing plant and animal cells

The cell: card sort

The list of cell components, their description and function can be organized as a card sort. This can be seen in the card sort exercise shown in Figure 1.2, which can be easily differentiated by the removal of the more complex components. Simply cut these out in advance of the lesson.

Figure 1.2 Card sort activity: the cell

Common misconceptions include students using the terms ‘cell wall’ and ‘cell membrane’ interchangeably and thinking that mitochondria can be seen with a light microscope. It should be noted that the cell membrane and tonoplast are difficult to see in many plant cells. The position of these can be highlighted during a practical by using the purple epidermis layers between the fleshy leaves in red onions. The position of the cytoplasm can be located because the cell contents are suspended within it.

Levels of organization: card sort

Cells can be added together to make increasingly complex organisms and parts of organisms. This can be seen in the card sort exercise in Figure 1.3.

Figure 1.3 Card sort activity: levels of organization

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Practical activity

Looking at animal cells

You can look at your own cells, but this requires you to take a sample of your own cheek cells (epithelial cells). The students quite like this as they are looking at their own cells – a rare opportunity.

Health and safety

You must check the health and safety regulations where you teach as rules vary from school to school and from county to county. Your senior technician or health and safety officer will be able to say if any practical is banned in your school. Alternatives are usually available if this is the case.

If you can go ahead and do this practical, you must make sure you use a clean scraper or cotton bud and dispose of it in accordance with the regulations in your school. Ideally the scrapers should have been dry sterilized before use and be disposed of in disinfectant afterwards.

Be careful not to focus direct sunlight through the microscope because this can damage your eyes.

Method

The method is as follows (see also Figure 1.4). Take a clean scraper and rub it on the inside of your cheek. Around ten scrapes are enough to get a decent sample, but be careful to collect cheek cells and not saliva. Rub the scrapings on to a clean glass slide and put the scraper in disinfectant. Add a couple of drops of methylene blue, being carefu...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Contents
• About the authors
• Acknowledgements
• Introduction
• Section 1 Beginnings and development of living things
• Section 2 Chemical and material properties
• Section 3 Light and motion
• Section 4 The Earth and its place in the universe
• Index