Unit3L.3: Bacteria Viruses Fungi Science skills: Classification Observing Predicting Comparing 37
3.8.1 Life Science Bacteria Why should I keep myself clean? Germs! Germs! Germs! Germs can be too tiny to see, but they can make you ill. These germs are also called microbes. These UsingleU UcellU organisms can be seen only with a UmicroscopeU. The microscope 38
Activity: Materials Microscope, slides of microbes Process Skills Observing Steps: 1- Take a microscope. 2- Place a slide on the stage of the microscope. 3- Adjust the lens. 4- Observe the slide. 5- Draw what you see. or microbes are tiny living things that live everywhere, in air, soil, rock, water and also inside our body 39
Microbes are a group of living thing that include bacteria, viruses and fungi. They are special groups of UlivingU things. Therefore, they have Ulife processesu. Time to think Why are microbes living things? (Hint: List the life processes). Bacteria Microbes belonging to the bacteria group and are made up of only one cell. Under the microscope, bacteria look like balls, rods or spirals. Ball shaped bacteria Rod shaped bacteria Spiral shaped bacteria 40
3.8.1 Life Science Viruses Viruses are the smallest microbes, much smaller than bacteria. Viruses can be rod shaped, sphere shaped or multisided. Rod shaped virus Sphere shaped virus Multisided virus 41
3.8.1 Life Science Fungi Fungi can be found in air, soil, plants and in water. Millions of different types of fungi exist on Earth. The most common ones are mushrooms, yeast, mould and mildew. Mushroom Yeast Mould Mildew Some micro-organisms are harmful. They cause illness in humans. Examples : Common cold, chicken pox, tooth decay, food poisoning. 42
Activity: Materials Pieces of fruit, vegetable or bread Some water Process Skills Experimenting Observing Steps: 1- Put the pieces of food in the bag. 2- Put a little water in the bag. 3- Close the bag. 4- Keep for 3 days in a warm place. 5- Observe the pieces of fruit, vegetable or bread on the fourth day. 6- Take a piece of the mouldy food and observe under the microscope. BE CAREFUL use plastic gloves! 7- Draw and colour what you observe. 43
Some micro-organisms are helpful. They help in making bread, cheese, yogurt and vinegar. They also help in making antibiotics (medicine). Other micro-organisms help to rot (decay) dead Other micro-organisms help to rot (decay) dead plants and animals, making the soil rich which is good for the growth of plants. Decayed plants Compost heap! Makes excellent soil! 44
Activity: Bread making Materials Yeast (a fungus) - 2 Tbsp warm water - 2 cups Bread flour - 5 cups total, Sugar - 2 Tbsp. Salt - 2 tsp. Oil - 2 Tbsp. 3 loaf pans Steps: Oven pre-heated to 375 Process Skills Experimenting Observing 1-Start by mixing the hot water and the flour. Then, add 2 Tbsp. sugar, 2 Tbsp. oil, 2 Tbsp. yeast and 2 tsp. salt. 2-Knead the dough for 8 or 9 minutes 3-Let the dough rise in a warm place for about 45 minutes to an hour. 4-Preheat your oven to 375 F and put the loaves in. Bake them for about 25 minutes Question: What does the yeast do and how does it do this? 45
Key terms Microorganisms Microscope Bacteria Viruses Fungi Key ideas are tiny living things which are grouped as bacteria, viruses and fungi A Microscope is an instrument used in order to see microbes. Key Questions Q1- Who am I? A- I make your bread soft and tasty B- I am the smallest microbe Q2- Which of these are true and which are false? A- feed and grow. B- reproduce. C- All micro-organisms are harmful. D- are only found in the washroom. 46