Ks4 microbes

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  • 1. KS4 Biology Microbes1 of 39 Boardworks Ltd 2004
  • 2. Contents Microbes What are microbes? Bacteria and viruses Microbes and disease How do microbes reproduce? Summary quiz2 of 39 Boardworks Ltd 2004
  • 3. What causes disease? Why do people become ill? People who lead very unhealthy lifestyles sometimes become ill but it is also clear that people can become ill despite leading a healthy lifestyle. Why? Therefore, rather than something being wrong with that person, perhaps something else changes the normal state of the body and causes disease. These were eventually discovered to be MICROBES3 of 39 Boardworks Ltd 2004
  • 4. Microbes As the name suggests, they are microscopic organisms. They can only be seen using a microscope.4 of 39 Boardworks Ltd 2004
  • 5. Microbes The two kinds of microbe that we will be dealing with are: BACTERIA VIRUSES Now it is important at this point to remember what it means to be living organism. A living organism must be able to demonstrate that it can perform the seven life processes.5 of 39 Boardworks Ltd 2004
  • 6. The seven signs of life6 of 39 Boardworks Ltd 2004
  • 7. Microbes The reason for looking back to these 7 characteristics is because although bacteria can perform all of these life processes, viruses cannot reproduce on their own. Does this mean that viruses are non-living? This question is still hotly debated!7 of 39 Boardworks Ltd 2004
  • 8. Microbes Bacteria have a traditional cell structure, as with animals and plants. Viruses do not. Let us firstly consider what these microbes look like and how they compare to the structure of cells that we are familiar with. We will firstly deal with the general structure of a bacterium (singular of bacteria). Bacteria are amongst the smallest known to mankind.8 of 39 Boardworks Ltd 2004
  • 9. Contents Microbes What are microbes? Bacteria and viruses Microbes and disease How do microbes reproduce? Summary quiz9 of 39 Boardworks Ltd 2004
  • 10. A single bacterium Bacteria can be different shapes but this diagram can represent them. cell wall cytoplasm cell membrane loose genetic material present in animal cells absent from animal cells10 of 39 Boardworks Ltd 2004
  • 11. Bacterium So, the bacterium shares some structural characteristics with an animal cell but shows important differences. The most obvious differences are: the absence of a distinct nucleus the presence of a cell wall The other major difference is the size of the cell. To get an idea of how small these cells are, remember that the human body consists of approximately 100 million animal cells. Bacteria cells are 10-1000 times smaller than animal cells.11 of 39 Boardworks Ltd 2004
  • 12. Bacterium If we wanted to measure a single bacterium, its length would range from: 1 1 mm to mm 1000 20 If a full stop is 1mm wide how many bacteria could you line up along it? Between 1000 and 20 bacteria would fit on a full stop!12 of 39 Boardworks Ltd 2004
  • 13. Virus Now lets consider the structure of the virus. protein injection coat tube loose genetic material tail plate Absent in animal cells13 of 39 Boardworks Ltd 2004
  • 14. Viruses - how small? Viruses are very different to bacteria because they do not have a cellular structure and are much smaller. Bacteria are 100 times smaller than a human cell. Viruses are 1000 times smaller than a bacteria. So how small are viruses compared to a human cell? 100 000 times smaller!14 of 39 Boardworks Ltd 2004
  • 15. Viruses and tennis balls! Heres another way to think about the size of viruses... If a common cold virus was the size of a tennis ball, how big would a nose be? A. the size of a supermarket B. the size of Birmingham C. the size of Wales15 of 39 Boardworks Ltd 2004
  • 16. Viruses living or not? If viruses are such tiny microbes, how do they cause so much havoc? Viruses need to hijack a host cell, like a human body cell, in which to live and make more viruses. Viruses cannot function if they are outside of a host cell. Some scientists say that viruses are not alive because of how they reproduce. Would you say a virus was living or not?16 of 39 Boardworks Ltd 2004
  • 17. Bacterium label the parts17 of 39 Boardworks Ltd 2004
  • 18. Virus label the parts18 of 39 Boardworks Ltd 2004
  • 19. Virus and bacterium properties19 of 39 Boardworks Ltd 2004
  • 20. Contents Microbes What are microbes? Bacteria and viruses Microbes and disease How do microbes reproduce? Summary quiz20 of 39 Boardworks Ltd 2004
  • 21. Viruses and bacteria