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- 1. IGCSE BIOLOGY SECTION 1 LESSON 3
- 2. Content Section 1 The nature and variety of living organisms a) Characteristics of living organisms b) Variety of living organisms
- 3. Content Lesson 3 b) Variety of living organisms b) Variety of living organisms Bacteria: These are microscopic single-celled organisms; they have a cell wall, cell membrane, cytoplasm and plasmids; they lack a nucleus but contain a circular chromosome of DNA; some bacteria can carry out photosynthesis but most feed off other living or dead organisms Examples include Lactobacillus bulgaricus, a rod-shaped bacterium used in the production of yoghurt from milk, and Pneumococcus, a spherical bacterium that acts as the pathogen causing pneumonia Protoctists: These are microscopic single-celled organisms. Some, like Amoeba, that live in pond water, have features like an animal cell, while others, like Chlorella, have chloroplasts and are more like plants. A pathogenic example is Plasmodium, responsible for causing malaria Viruses: These are small particles, smaller than bacteria; they are parasitic and can reproduce only inside living cells; they infect every type of living organism. They have a wide variety of shapes and sizes; they have no cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA Examples include the tobacco mosaic virus that causes discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts, the influenza virus that causes ‘flu’ and the HIV virus that causes AIDS 1.3 recall the term ‘pathogen’ and know that pathogens may be fungi, bacteria, protoctists or viruses.
- 4. Classification Kingdom Monera (Prokaryotes) Bacteria and Blue-green algae Protoctista Amoeba, Paramecium Fungi Moulds, Mushrooms, Yeast Plants Algae, ferns and mosses, conifers and flowering plants Animals Jellyfish, worms, arthropods, molluscs, echinoderms, fish, amphibia, reptiles, birds and mammals.
- 5. Classification Kingdom Monera (Prokaryotes) Bacteria and Blue-green algae Protoctista Amoeba, Paramecium Fungi Moulds, Mushrooms, Yeast Plants Algae, ferns and mosses, conifers and flowering plants Animals Jellyfish, worms, arthropods, molluscs, echinoderms, fish, amphibia, reptiles, birds and mammals.
- 6. Bacteria: These are microscopic single-celled organisms; they have a cell wall, cell membrane, cytoplasm and plasmids; they lack a nucleus but contain a circular chromosome of DNA; some bacteria can carry out photosynthesis but most feed off other living or dead organisms Examples include Lactobacillus bulgaricus, a rod- shaped bacterium used in the production of yoghurt from milk, and Pneumococcus 肺炎球菌, a spherical bacterium that acts as the pathogen causing pneumonia 肺炎
- 8. Examples of bacteria Lactobacillus – rod shaped bacterium used in the production of yoghurt from milk.
- 9. Examples of bacteria Lactobacillus – rod shaped bacterium used in the production of yoghurt from milk. Pneumococcus – spherical bacterium. A pathogen causing pneumonia
- 10. Examples of bacteria Lactobacillus – rod shaped bacterium used in the production of yoghurt from milk. Pneumococcus – spherical bacterium. A pathogen causing pneumonia Pathogen – a microorganism that causes disease in its host. The host may be an animal, a plant or even another microorganism.
- 11. Structure of bacteria Singular = bacterium
- 12. Structure of bacteria Very small organisms, rarely more than 0.01mm in length, so can only be seen with more powerful microscopes.
- 13. Structure of bacteria Very small organisms, rarely more than 0.01mm in length, so can only be seen with more powerful microscopes. Cell wall - Not made of cellulose but of a complex mixture of proteins, sugars and lipids.
- 14. Structure of bacteria Very small organisms, rarely more than 0.01mm in length, so can only be seen with more powerful microscopes. Cell wall - Not made of cellulose but of a complex mixture of proteins, sugars and lipids. Some may have a slime capsule outside the cell wall – protects the bacterium
- 15. Structure of bacteria Very small organisms, rarely more than 0.01mm in length, so can only be seen with more powerful microscopes. Cell wall - Not made of cellulose but of a complex mixture of proteins, sugars and lipids. Some may have a slime capsule outside the cell wall – protects the bacterium No nuclear membrane (prokaryotes), but instead have a single chromosome, a strand of DNA
- 16. Structure of bacteria Very small organisms, rarely more than 0.01mm in length, so can only be seen with more powerful microscopes. Cell wall - Not made of cellulose but of a complex mixture of proteins, sugars and lipids. Some may have a slime capsule outside the cell wall – protects the bacterium No nuclear membrane (prokaryotes), but instead have a single chromosome, a strand of DNA Cytoplasm Glycogen granules
- 17. Structure of bacteria Very small organisms, rarely more than 0.01mm in length, so can only be seen with more powerful microscopes. Cell wall - Not made of cellulose but of a complex mixture of proteins, sugars and lipids. Some may have a slime capsule outside the cell wall – protects the bacterium No nuclear membrane (prokaryotes), but instead have a single chromosome, a strand of DNA Cytoplasm Glycogen granules Bacteria may also have flagella 鞭毛
- 18. Structure of bacteria Very small organisms, rarely more than 0.01mm in length, so can only be seen with more powerful microscopes. Cell wall - Not made of cellulose but of a complex mixture of proteins, sugars and lipids. Some may have a slime capsule outside the cell wall – protects the bacterium No nuclear membrane (prokaryotes), but instead have a single chromosome, a strand of DNA Cytoplasm Glycogen granules Bacteria may also have flagella Plasmid – a small circular piece of DNA. Often carry genes which give the bacterium resistance to antibiotics
- 20. Physiology of bacteria Streptococcus Nutrition – a few species of bacteria are able to photosynthesise and make their own food. The majority live on their food – they release enzymes which digest the food and then they absorb the liquid products back into the cell. 它们释放消化食 物的酶，然后将液体产物吸收 回细胞中 extracellular digestion = 细胞外消化
- 21. Physiology of bacteria Streptococcus Reproduction – bacteria reproduce asexually by a process called binary fission 二分裂. One cell divides into two, then two into four, and so on. This can happen every twenty minutes. If this were to occur, then after 12 hours there would be 34,359,738,368 bacteria formed from a single cell!
- 22. Useful and harmful bacteria
- 23. Useful and harmful bacteria Making cheese Making yoghurt Antibiotics Sewage treatment Oil spill clean up Mining metals Fuels Decay Genetic engineering Fixing nitrogen
- 24. Useful and harmful bacteria Sore throat Boils Pneumonia Anthrax Typhoid fever Scarlet fever Syphilis Cholera Food poisoning Whooping cough
- 25. Classification Kingdom Monera (Prokaryotes) Bacteria and Blue-green algae Protoctista Amoeba, Paramecium Fungi Moulds, Mushrooms, Yeast Plants Algae, ferns and mosses, conifers and flowering plants Animals Jellyfish, worms, arthropods, molluscs, echinoderms, fish, amphibia, reptiles, birds and mammals.
- 26. Protoctists: These are microscopic single- celled organisms. Some, like Amoeba, that live in pond water, have features like an animal cell, while others, like Chlorella, have chloroplasts and are more like plants. A pathogenic example is Plasmodium, responsible for causing malaria 疟疾
- 29. Examples of Protoctists Amoeba Chlorella
- 30. Examples of Protoctists Amoeba 阿米巴 Chlorella 小球藻 Plasmodium 疟原虫
- 31. Examples of Protoctists Amoeba Amoeba fact file: Microscopic, one-celled organism. Live in fresh water (puddles, ponds)
- 32. Examples of Protoctists Amoeba Amoeba fact file: Microscopic, one-celled organism. Live in fresh water (puddles, ponds) Typical animal cell, porous cell membrane, cytoplasm, nucleus.
- 33. Examples of Protoctists Amoeba Amoeba fact file: Microscopic, one-celled organism. Live in fresh water (puddles, ponds) Typical animal cell, porous cell membrane, cytoplasm, nucleus. Feed on algae, bacteria, plant cells, protozoa. Cytoplasm surrounds food particles to form a food vacuole where digestion takes place.
- 34. Examples of Protoctists Amoeba Amoeba fact file: Microscopic, one-celled organism. Live in fresh water (puddles, ponds) Typical animal cell, porous cell membrane, cytoplasm, nucleus. Feed on algae, bacteria, plant cells, protozoa. Cytoplasm surrounds food particles to form a food vacuole where digestion takes place. Pseudopodia = “false feet”. Amoebas move by changing the shape of their body, forming pseudopods.
- 35. Examples of Protoctists Chlorella Chlorella fact file: Single-celled green algae. Spherical in shape.
- 36. Examples of Protoctists Chlorella Chlorella fact file: Single-celled green algae. Spherical in shape. Contains chlorophyll which enables it to photosynthesise.
- 37. Examples of Protoctists Plasmodium Plasmodium fact file: A single-celled Protozoan that causes the disease known as malaria. Spread from person to person by the female mosquito as they suck blood.
- 38. Examples of Protoctists Plasmodium Plasmodium fact file: A single-celled Protozoan that causes the disease known as malaria. Spread from person to person by the female mosquito as they suck blood. Plasmodium invades the red blood cells of the host and feeds on the cytoplasm.
- 39. Examples of Protoctists Plasmodium Plasmodium fact file: A single-celled Protozoan that causes the disease known as malaria. Spread from person to person by the female mosquito as they suck blood. Plasmodium invades the red blood cells of the host and feeds on the cytoplasm. Nearly 3 million people each year die from malaria.
- 40. Viruses: These are small particles, smaller than bacteria; they are parasitic 寄生 and can reproduce only inside living cells; they infect every type of living organism. They have a wide variety of shapes and sizes; they have no cellular structure but have a protein coat and contain one type of nucleic acid, either DNA or RNA. Examples include the tobacco mosaic virus 烟草花叶病毒 that causes discolouring of the leaves of tobacco plants by preventing the formation of chloroplasts, the influenza virus 流感病毒 that causes ‘flu’ and the HIV virus that causes AIDS
- 41. Examples of viruses Tobacco Mosaic Virus (virology.wisc.edu)
- 42. Examples of viruses Tobacco Mosaic Virus (virology.wisc.edu) InfluenzaVirus (medimoon.com)
- 43. Examples of viruses Tobacco Mosaic Virus (virology.wisc.edu) InfluenzaVirus (medimoon.com) HIV Virus (123rf.com)
- 44. Examples of viruses Tobacco Mosaic Virus (virology.wisc.edu) InfluenzaVirus (medimoon.com) HIV Virus (123rf.com) TMV was the first virus to be discovered in 1930. Causes mottling and discoloration of tobacco leaves. Rod-like appearance, surrounded by a resistant protein coat
- 45. Examples of viruses Tobacco Mosaic Virus (virology.wisc.edu) InfluenzaVirus (medimoon.com) HIV Virus (123rf.com) Highly contagious, infects the respiratory tract. It affects all ages, but children tend to get it more than adults Spread by droplets that are coughed or sneezed.
- 46. Examples of viruses Tobacco Mosaic Virus (virology.wisc.edu) InfluenzaVirus (medimoon.com) HIV Virus (123rf.com) A slowly-replicating retrovirus that causes acquired immunodeficiency syndrome (AIDS) 获得性免 疫缺陷综合征, which causes the immune system to fail. Infection through body fluids.
- 47. Examples of viruses Tobacco Mosaic Virus (virology.wisc.edu) InfluenzaVirus (medimoon.com) HIV Virus (123rf.com) A slowly-replicating retrovirus that causes acquired immunodeficiency syndrome (AIDS), which causes the immune system to fail. Infection through body fluids. Retrovirus - a virus that replicates in a host cell
- 50. Structure of viruses Much smaller than a bacterium, can only be seen with electron microscopes
- 51. Structure of viruses Much smaller than a bacterium, can only be seen with electron microscopes All viruses have a central core of RNA or DNA surrounded by a protein coat.
- 52. Structure of viruses Much smaller than a bacterium, can only be seen with electron microscopes All viruses have a central core of RNA or DNA surrounded by a protein coat. No nucleus, cytoplasm, cell organelles or cell membrane
- 53. Structure of viruses Much smaller than a bacterium, can only be seen with electron microscopes All viruses have a central core of RNA or DNA surrounded by a protein coat. No nucleus, cytoplasm, cell organelles or cell membrane So, are they really cells at all?
- 54. Structure of viruses Much smaller than a bacterium, can only be seen with electron microscopes All viruses have a central core of RNA or DNA surrounded by a protein coat. No nucleus, cytoplasm, cell organelles or cell membrane So, are they really cells at all? MRS GREN
- 55. Structure of viruses Much smaller than a bacterium, can only be seen with electron microscopes All viruses have a central core of RNA or DNA surrounded by a protein coat. No nucleus, cytoplasm, cell organelles or cell membrane So, are they really cells at all? MRS GREN Viruses do reproduce, but only inside the cells of living organisms, using materials obtained from the host cell.
- 56. Structure of viruses Much smaller than a bacterium, can only be seen with electron microscopes All viruses have a central core of RNA or DNA surrounded by a protein coat. No nucleus, cytoplasm, cell organelles or cell membrane So, are they really cells at all? MRS GREN Viruses do reproduce, but only inside the cells of living organisms, using materials obtained from the host cell. The protein coat is called a capsid 衣壳, and is made up of regularly packed protein units called capsomeres.
- 58. Multiplication of viruses Viruses are able to survive outside the host cell, but they must penetrate into a host in order to reproduce.
- 59. Multiplication of viruses 1. The virus sticks to the cell membrane of a suitable host cell.
- 60. Multiplication of viruses 1. The virus sticks to the cell membrane of a suitable host cell. 2. An ‘injection’ tube ‘injects’ the DNA or RNA into the host cell.
- 61. Multiplication of viruses 1. The virus sticks to the cell membrane of a suitable host cell. 2. An ‘injection’ tube ‘injects’ the DNA or RNA into the host cell.
- 62. Multiplication of viruses 3. The viral DNA uses the cell’s contents to make new strands and capsomeres
- 63. Multiplication of viruses 3. The viral DNA uses the cell’s contents to make new strands and capsomeres 4. The DNA and capsomeres make new virus particles which escape from the cell
- 64. Diseases caused by viruses Common cold Poliomyelitis Measles Mumps Chickenpox Herpes Rubella Influenza AIDS
- 65. Pathogen – a microorganism that causes disease in its host. The host may be an animal, a plant or even another microorganism.
- 66. Pathogen – a microorganism that causes disease in its host. The host may be an animal, a plant or even another microorganism. Bacterium Pneumococcus – causes pneumonia
- 67. Pathogen – a microorganism that causes disease in its host. The host may be an animal, a plant or even another microorganism. Bacterium Pneumococcus – causes pneumonia Virus InfluenzaVirus (medimoon.com)
- 68. Pathogen – a microorganism that causes disease in its host. The host may be an animal, a plant or even another microorganism. Bacterium Pneumococcus – causes pneumonia Virus InfluenzaVirus (medimoon.com) Protoctist Plasmodium – causes malaria
- 69. Pathogen – a microorganism that causes disease in its host. The host may be an animal, a plant or even another microorganism. Bacterium Pneumococcus – causes pneumonia Virus InfluenzaVirus (medimoon.com) Protoctist Plasmodium – causes malaria Fungus Fusarium – fungal pathogen that infects wheat crops (bbsrc.ac.uk)
- 70. End of Section 1 Lesson 3 In this lesson we have covered: • Outline of the monera kingdom • Outline of the protoctist kingdom • Outline of viruses • Examples of pathogens