Cambridge Primary Science Learners Book 2021 PDF

1.4 Diseases Living things that cause disease Diseases stop our bodies from working properly. There are different kinds of living things that cause disease. They infect other living things and grow and reproduce on or in the body of the living thing that they infect. Any living thing that lives on...

1.4 Diseases Living things that cause disease Diseases stop our bodies from working properly. There are different kinds of living things that cause disease. They infect other living things and grow and reproduce on or in the body of the living thing that they infect. Any living thing that lives on or in the body of another living thing is called a parasite. The living thing that a parasite infects is called the host. Bacteria are very small living things that we can only see using a microscope. Bacteria cause diseases such as cholera and pneumonia. Not all bacteria are harmful. Viruses are even smaller than bacteria. All viruses are harmful and cause diseases in humans, animals and plants. Some viruses even infect bacteria! Humans get flu, chicken pox and measles from viruses. The yeast that we use to make bread rise is a fungus. Mushrooms that we eat are also fungi. But some fungi are parasites that cause diseases. Ringworm in humans and animals, athlete’s foot in humans and rusts in plants are caused by fungi. There are other kinds of parasites that also cause infectious diseases. Malaria and dysentery are two diseases caused by these parasites. Questions 1 a What is a parasite? b Why are viruses and some bacteria and fungi parasites? 2 Make a table of the different kinds of living things that cause diseases and name two examples of a disease that each one causes. 25