Atom. This level consists of the atoms of the chemical elements that make up living things. For example, an oxygen atom (O). The elements in living things are called biochemical elements. Molecule. Molecules are two or more atoms joined together by chemical bonds. For example, a water molecule (H2O). The molecules in living things are called biomolecules. Some are inorganic: water and mineral salts. Others are organic: lipids, carbohydrates, proteins and nucleic acids. Tissue. Tissue is made up of a group of cells of the same type. They work together to carr y out one or more functions. For example, muscle tissue, which is a group of muscle cells. 1 Your art exhibition could show the different levels of organisation of living matter. a) What is the first level? Why? b) How many levels would you have in total? 2 Get into groups. Choose one or two classmates to be the exhibition guide for each level. Prepare a report with all of this information. 3 Look for information about the functions that the main biochemical elements and biomolecules carry out in humans. Write a brief summary. 4 Put these elements in order from smallest to largest according to their level of organisation: stomach, person, carbon, skin, digestive system, protein, skeleton, red blood cell. 5 WORK WITH THE IMAGE. Look at the diagram at the bottom of the next page. a) Calculate the equivalence in metres of one micron (mm) and one nanometre (nm). b) Which levels of organisation are visible with an optical microscope? Which levels are visible to the naked eye? 6 Find out the differences between an optical microscope and an electron microscope. Why can't living things be observed with an electron microscope? 1. Levels of organisation O H H Human beings are highly organised organisms. We are made up of tiny, simple particles that combine to form more complex structures. Every degree of complexity in which living matter is organised is a level of organisation. Each level is structurally and functionally more complex than the previous level . Cell . This is the first living level , because it is made up of cells. For example, muscle cells. Like many living things, human beings are made of many cells. We are multicellular. CHALLENGE 18
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