LO 6 Biological World strand LO 6, 10 Nature of Science strand
15.1 What is health? . . . . . . . 156 15.2 Micro-organisms . . . . . . 156 15.3 The immune system . . . . . 159 15.4 Factors affecting human health 160
Why it matters
It has been said that ‘our health is our wealth’. In order to stay healthy we need to understand what makes us healthy, how to avoid illness and how to avoid making unhealthy choices.
15.1 What is health?
Health can be defined as being ‘free of illness or injury’. The World Health Organisation (WHO) defines health as ‘a state of complete physical, mental and social wellbeing and not merely the absence of disease or infirmity’. Do you think WHO’s definition includes more aspects of human health than the basic definition? What are those aspects?
Activity 1. Consider three things you did this week that were good for your health. 2. Consider three things you did this week that were not good for your health.
15.2 Micro-organisms
Micro-organisms Tiny living things that can only be seen using a microscope.
Many diseases and illnesses are caused by tiny microscopic living things called micro-organisms. Bacteria, fungi and viruses are examples of micro-organisms.
Bacteria Bacteria are micro-organisms. They are simple living cells. They can reproduce very quickly. When viewed under a microscope some bacteria look like the image in Fig. 1. In order to see bacteria in a laboratory they are grown on a nutrient gel and can be seen by the naked eye (Fig. 2).
