33 Identify the levels of organisation in this short text: Iron forms part of the haemoglobin that is found in red blood cells. Haemoglobin is necessary for transporting oxygen from the lungs to the tissues, such as muscle and cartilage tissue. 34 B I O L O G Y A N D H I S T O R Y. The first person to discover the cell was Robert Hooke. In the year 1665, he published the results of his findings on plant tissues. There was hardly any progress on the study of cells in the 18th century. It wasn't until the 19th century that cells were studied in greater detail and their internal structures were observed. a) Research the main discoveries regarding cells. Make a timeline with the information you have found. Indicate the person and the date of discovery of the organelles and structures. b) Why do you think so much time passed between the moment Robert Hooke first discovered the cell and the understanding of cell structure and the different organelles? 35 From a morphological point of view, what is the difference between the cell membrane and the nuclear membrane? 36 If we use a microscope to compare the muscle cells of an athlete with those of a sedentary person, we can see that the athlete's cells have a higher number of mitochondria. Explain why. 37 Draw a diagram of the cell in the photo and label all the parts that you know. 38 Why do you think there are so many shapes of cells? Look for different examples and photos of human cells. Match each shape with the function its cell carries out. 39 What does it mean when we say a cell is specialised? Why does a cell lose its independence as an organism once it has specialised? 1 c h e c k yo u r p r o g r e s s 40 B I O L O G Y A N D E T H I C S . Embryonic stem cells are found in embryos that are at least four or five days old. Tissues and organs develop from these cells. Today, embryonic stem cells are used to treat certain diseases. One of the ways we can obtain these cells is from embryos in the early phases of development. Some people who have had assisted reproduction treatment and have not used the embryos donate them. a) Do you think it is ethical to use human embryos to cure diseases? b) If you were to go through assisted reproduction treatments in the future, would you donate embryos to science? 31
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