The Really Useful Science Book

A Framework of Knowledge for Primary Teachers

Steve Farrow, Amy Strachan

• Publisher: Routledge
• Year: 2017
• ISBN:
  9781317276005
• Edition: 4
• Topic: Didattica
• Subtopic: Didattica generale

Offering support to both trainee and practising teachers, the fourth edition of The Really Useful Science Book is the perfect tool for those who wish to extend their subject knowledge, enhance their teaching and create lessons which link directly to the National Curriculum. The easy-to-follow framework provides comprehensive science knowledge for Key Stages 1 and 2 and is fully updated with new material to inspire stimulating and engaging science lessons.

The book is divided into three sections: Biology, Chemistry and Physics. Each section integrates key scientific ideas and facts with innovative teaching methods and activity suggestions, and user-friendly language and illustrations help to explain key scientific concepts. With links to global learning, discussion of common misconceptions, and ideas for cross-curricular opportunities, each chapter connects knowledge to practice and informs creative and inspiring teaching.

The Really Useful Science Book is an invaluable reference resource for all classroom teachers who wish to develop the confidence to teach enquiry-based practical science with relevance to pupils and their global community.

KEY IDEA 2.1

The characteristics of living things

All living things have a number of characteristics in common.

CONCEPTS TO SUPPORT KEY STAGE 1

How do we know that things are alive? Young children have been known to describe a car as being alive because it can move, or a calculator, because numbers appear when you switch it on and press the buttons. A group of 5-year-olds once explained that big boulders grew from little ones – a perfectly understandable 5-year-old conclusion, as they had seen plants grow from seeds, and they knew that small, young people grew into bigger, older people!

It takes time and experience with a variety of living and non-living material to begin to develop the notion of ‘alive’ and the understanding that all living things have a number of characteristics in common. It may be helpful to remember that, although some ‘inanimate’ objects may exhibit some of these characteristics, only living things exhibit them all.

The characteristics of living things

Living things, including humans, have the ability to: feed, respire, excrete, grow, respond to stimuli, move and reproduce.

It is worth remembering, however, that these characteristics provide us only with an operational definition – they tell us what living things can do, not what they are. In some cases, this can be a source of real confusion for primary pupils. Living things are not doing all of these things simultaneously. Many of these characteristics are not directly observable – pupils cannot see a tree ‘feeding’ itself for example; not all living organisms move, nor do all of them reproduce. A mule, for instance, though very much alive, is an infertile hybrid resulting from the mating of a horse and a donkey.

To add to the confusion, some organisms, at some stages of their life cycles, show no signs of life at all. Plant seeds are good examples of organisms in such a state, which is known as suspended animation. What has happened is that the seed has dried out – typically, seeds contain less than 10 per cent water, compared with 80–90 per cent in the parent plant. This desiccation slows down the rate at which chemical reactions take place in the seed, allowing it to survive periods of relatively hostile conditions – drought, for example, or the onset of winter.

So, the answer to the question ‘Is a seed alive?’ is ‘We do not know’ – at least, not until we have restored normal growing conditions to see if the seed germinates.

An example of suspended animation from the animal kingdom would be the desiccated egg cysts of brine shrimps (sold commercially as ‘sea monkeys’). These cysts appear to be completely inert and can withstand years of desiccation, only to ‘come to life’ when rehydrated in the correct saline conditions. Perhaps the most crucial idea relating to living organisms is that they are all capable of self-maintenance and can respond, within limits, to changes in their environment. Such responses limit the effect of change on an organism and help it to maintain an internal environment at or near optimum. The mechanisms by which such responses occur will be explained in Key Idea 2.2: Life processes.

CONCEPT CONFUSION

Children may find it challenging to recognize some living things owing to their lack of movement – for example trees, coral and lichen. It may also be difficult to distinguish between things that were once alive and things that were never alive. One strategy is to ask children where something came from. For example, wood was once part of a tree, and so we can say it was once living, whereas a rock or stone was part of the Earth’s crust, and so we can say it was never living. Fossils add another layer of complexity, as they are mineral ‘casts’ of something that was once alive.

CONCEPTS TO SUPPORT KEY STAGE 2

The characteristics of living things (feeding, excretion, respiration, growth, response to stimuli, movement and reproduction), outlined above, are all processes that occur as a result of the specialization of cells in the plants and animals concerned.

It is possible to visualize the processes on a ‘micro-to-macro’ scale (Figure 2.1):

•life processes at the most fundamental level involve the synthesis, breakdown and recombination of inorganic and organic molecules;

•these molecules are broken down, reassembled and incorporated into the individual units of life – the cells;

•cells of a similar kind, having similar functions, are grouped together as tissues;

•tissues are grouped together in organs; and

•organs that contribute to major bodily functions are grouped in organ systems.

Cells and tissues

All living organisms are made up of cells. Cells are the microscopic ‘packets’ of living matter that make up the complete organism. In some cases, the organism itself consists of a single cell (see Key Idea 2.4: The variety of life), but all higher plants and animals are composed of millions (or even billions) of cells, many of which are specialized to perform specific functions. But, no matter how simple or complex the organism is, the cells of which it is made have a number of characteristics in common with all other cells:

•they will have arisen from pre-existing cells (by some form of cell division);

•they will be the reaction sites for all the metabolic processes that take place in the organism.

In addition, almost all cells (red blood cells are an exception):

•contain a nucleus that is composed mainly of the chemicals (nucleic acids) that control the functioning of the cell.

These nucleic acids (the most famous of which is deoxyribonucleic acid – DNA) carry the ‘blueprint’ or ‘toolbox’ for the functioning of each cell and enable the assembly of the various organic chemicals that allow the cell to function.

Figure 2.1Processes on a micro-to-macro scale

Figure 2.2Plant and animal cells

Figure 2.2 is a diagram of generalized plant and animal cells. Differences in cellular structure are listed in Key Idea 2.2: Differences between plants and animals.

Many types of cell are specialized to perform specific functions and are grouped together in tissues. In some tissues, the constituent cells are able to transmit impulses (nerve cells), or are able to slide across one another (muscle cells). Some are able to engulf bacteria (white blood cells), or are sensitive to light (retinal cells).

Organs and organ systems

The organs and organ systems can be grouped according to their functions, and one convenient grouping for mammals is as follows:

System name	Functions	Mammalian organs
Nutrition system, cardiovasc...