Microorganisms in the Environment PDF

# Microorganisms in the environment ## What is a microorganism? - A microorganism is a living organism that is so small that you can only see it clearly by using a microscope. - Like all living organisms, microorganisms are made of cells. - Many microorganisms are made of only one cell: they are s...

# Microorganisms in the environment ## What is a microorganism? - A microorganism is a living organism that is so small that you can only see it clearly by using a microscope. - Like all living organisms, microorganisms are made of cells. - Many microorganisms are made of only one cell: they are single-celled. - There are several different kinds of microorganism. They include bacteria, microscopic fungi, protozoa and algae. ## Bacteria - Bacteria are everywhere. - Bacteria is a plural word. The singular word, for just one of them, is bacterium. - Each bacterium is made of a single cell. - Cells of bacteria are much smaller than animal cells or plant cells. - You could fit 1000 of the bacteria in the photograph, lined up end to end, between two of the millimetre marks on your ruler. - Most bacteria are harmless but there are a few kinds that can make you ill. ## Fungi - Fungi (singular: *fungus*) are not always microorganisms. - Many fungi, including mushrooms and toadstools, are large and easy to see. - Mushrooms and toadstools are only part of the fungus's body, though, and they only grow at certain times of year. - Most of the time, the fungus is just a tangle of very thin threads. - The threads often grow under the ground, or inside a dead log. - The threads are so thin that they are difficult to see without a microscope. - There are also some kinds of fungi that do not produce mushrooms or toadstools. - They are made of single cells, not threads, so they are definitely microorganisms. - The powdery substance that you sometimes see on the surface of grapes is made up of millions of cells of yeast, which is a microscopic fungus. #### Questions 1. Viruses are even smaller than bacteria. Suggest why they are not usually said to be microorganisms. 2. We can see yeast on the surface of fruit. Why is yeast classed as a microorganism? ## Growing microorganisms - A single microorganism is too small to see without a microscope, but when left to grow, a single cell of a bacterium or fungi divides repeatedly to make a collection of many. - This collection of cells is called a colony. - The colonies are big enough for you to see without a microscope. - This can be done safely in the laboratory. - Scientists let microorganisms grow in a Petri dish containing a special kind of jelly, called agar jelly. - The dish and the jelly have to be sterile. - This means that any living organisms on them have been killed. ## Think like a scientist **Growing microorganisms from the air** - Microorganisms are so small that they can float around in the air. - You cannot see them, but they are there. - In this experiment, you will use agar jelly to grow some bacteria and fungi from the air. **You will need:** - a sterile Petri dish containing sterile agar jelly, - some sticky tape, - a pen that can write on plastic, - safety glasses. ## Microorganisms in the environment - The study of organisms in their environment is called *ecology*. - All the different organisms that live together affect one another in some way, for example, one species of animal may eat another animal. - A plant may provide shelter for an animal. - Microorganisms have important roles to play in the environment. - In the rest of this Unit, we will look at how microorganisms affect other organisms in their environment, including their importance in food chains and food webs. - In this topic, you will look at how food chains and food webs describe how energy, in the form of food, is transferred between animals and plants. - In the next topic, you will look at how microorganisms fit into food chains and food webs. ## Food chains - Arun has chicken and rice for lunch. - It gives him a lot of energy. - The food you eat gives you energy. - How did the energy get into the food? - The energy in food begins in the Sun. - Energy from the Sun reaches the Earth in sunlight. - Plants use energy from sunlight to make their own food. - Some of the energy from the sunlight goes into the food that the plant stores in its roots, stems, fruits, and leaves. - When an animal - such as Arun - eats part of the plant, it eats the food the plant made. - This is how the animal gets energy. - This is called energy transfer - You can show how the energy passes from the Sun into the rice, and then into Arun’s body, by drawing a food chain. - The arrows in the food chain show how energy is passed from the Sun to the rice plant, and then is transferred to Arun. ## Decomposers and decay - The food chains and food webs that you looked at in the previous topic did not include microorganisms. - But microorganisms are everywhere. - They live in the air, in the soil, in water, on our skin, and inside our bodies. - The apple in the picture has microorganisms growing on its surface. - Each spot on the apple is made up of millions of cells of microscopic fungi. - This kind of fungus is sometimes called mould. - The apple is mouldy. - The microorganisms have changed the apple. - They have made it decay. - Organisms that make things decay are called decomposers. - Many different kinds of microorganisms - including some kinds of bacteria and microscopic fungi - are decomposers. - Apples come from plants, which are living organisms. - Any substance that has been made by a living organism is called organic matter. - So, apples are organic matter. - Some microorganisms can break down organic matter when they feed on it. - This is what has caused the apple to decay. - The microscopic fungi have broken down the crisp, fresh apple and made it become brown and soft. - They have made the apple rot. ### Activity 7.3.1 **What can microorganisms decay?** Here are three questions. First, think quietly about the answers to the questions on your own. When your teacher tells you to, turn to your partner and discuss your ideas. Be ready to share your answers with the rest of the class. **Questions** 1. Which of these things are made of organic matter? - bread - water - leather - rock - wood - fruit 2. Think of two more things that are made of organic matter, and two more things that are not made of organic matter. 3. Which of the things in your answers to Questions 1 and 2 can be broken down by microorganisms? ## Roles of decomposers - No-one would want to eat a rotten apple. - The microorganisms that make an apple decay have spoiled the food. - But most of the time, decay by microorganisms is useful. - Microorganisms break down dead bodies and animal waste. - They decompose this material. - Almost all decomposers are microorganisms. - Fungi and bacteria are the most important decomposers - If the dead bodies and waste are not broken down by decomposers, they would just build up. - There would be heaps of dead plants, dead animals, and animal dung everywhere. - But there is an even more important reason why decomposers are useful. - The dead bodies and waste contain substances that living organisms can use to supply them with energy, or to help them to grow. - These substances are called nutrients. - When microorganisms decay organic matter, they return the nutrients to the soil. - Plants can then use the nutrients to help them to grow. - This is really helpful for the plants. - This also helps animals, because there are more plants to eat. ## Decomposers in food webs - Decomposers feed on almost every organism after it dies. - They also feed on waste from animals. - This is how decay microorganisms get their energy. - Energy from the dead organisms and their waste is transferred to the decomposers. - You can show this by adding decomposers to food chains or food webs. - You do not usually do this because you have to draw an arrow from every organism in the food chain or food web to the decomposers. - This makes it look very complicated. - The diagram shows a simple food web with decomposers added to it. #### Questions 1. Write a food chain of your own. Add decomposers to your food chain. 2. Look at the food web above. Are decomposers producers or consumers? Explain your answer. ### Activity 7.4.2 **Are all decomposers microorganisms?** - In this activity, you will think about how fungi fit into food chains. - Look at the photograph. - The toadstools in the photograph are not microorganisms. - You can see them easily, without a microscope. - In the photograph, the part of the fungus that you cannot see is inside the log, breaking it down.