CHAPTER 10 – HUMAN HEALTH


Micro-organisms Micro-organisms are very small living things. The three types of micro-organisms are: • bacteria


• viruses • fungi


Some micro-organisms can cause disease. Any micro-organism that causes disease is called a pathogen or, more commonly, a germ.


Bacteria


Bacteria are the most common organisms on Earth. All bacteria are made of only one cell and can reproduce asexually very quickly. Bacteria need food, water and a suitable temperature and pH to survive and reproduce. The perfect conditions for some bacteria are provided by the human body.


Disease in humans caused by bacteria include: • food poisoning • cholera


? TEST TUBE


12. Some bacteria are beneficial to human health. Research an example of ‘good bacteria’. • What is it called? • Where is it found? • What role does it play in human health?


• How can we promote its growth?


: Fig. 10.13 Bacteria cause food poisoning


The bacteria that live in our large intestine make vitamins B and K and stop other, more harmful bacteria that may cause disease from growing there.


Viruses


A virus is a small amount of genetic material, e.g. DNA, surrounded by protein. Diseases caused by viruses include: • Ebola • COVID-19 • AIDS • the common cold • influenza • cold sores • measles • mumps • chickenpox


• tuberculosis • tetanus


• pneumonia • tooth and gum decay


: Fig. 10.14 The virus causing COVID-19


A virus can only reproduce by entering the cells of another organism. Any organism that relies on another organism to live and does harm to that organism is called a parasite.


? TEST TUBE


13. Why might some scientists not consider viruses to be living things? (Hint: consider the characteristics of life.)


Elements of Science 101


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