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The Cell Theory In this presentation you will: explore the cell theory Next > Introduction All living things are made up of cells. They are the building blocks of life. Without living cells, an organism is not alive. Next > Introduction Some organisms, like bacteria and yeast, are made up of only one cell. Unicellular These are called unicellular organisms. Others, like most plants and animals (including humans) are made up of many cells. These are called multicellular organisms. Multicellular Multicellular Next > Discovery of the Cell In the mid-17th century an English scientist named Robert Hooke used a microscope to look at a section of cork. He noticed that cork was made up of microscopic box-like units. He called them cells. Next > Discovery of the Cell Hooke was the first person to observe and define the cell. After Hooke’s initial discovery, more scientists became involved in understanding cells. Next > Discovery of the Cell Modern microscopes look quite different from the one Hooke used. Eyepiece They work in the same way, but can use: either one or two eyepieces Objective lens either one or two objective lenses Next > Discovery of the Cell A microscope that uses one eyepiece and one objective lens is called a monocular microscope. One that uses two eyepieces and one objective lens is binocular. Monocular Binocular Stereoscope The stereoscope uses two eye pieces and two objective lenses. This makes the specimen appear in 3D to the user. Next > Cell Theory The investigation of the cell led to these accepted facts about cells: cells are the basic unit of life all living organisms are made up of at least one cell all cells come from other cells This is known as the Cell Theory. Next > What Cells Do All living organisms must be able to carry out the seven life processes to survive. These processes are: movement respiration sensitivity growth reproduction excretion nutrition Next > Life Processes To be ‘alive’ an organism must be able to carry out all these life processes. Cells can carry out these processes independently. They are the smallest living thing that can. They are alive. Next > Life Processes There are many different types of cells with many different jobs to do. However, every cell carries out all of the life processes. Next > Life Processes Cells carry out the same functions, and have the same needs, as a whole organism. In fact, the function and survival of an organism depends on the ability of individual cells to carry out these processes. oxygen, water and glucose in carbon dioxide and water out Next > Life Processes For example, you need food and water because your cells need food and water. You grow because your cells grow and divide. oxygen, water and glucose in carbon dioxide and water out Next > Movement Organisms need to be able to move to find food, shelter and avoid danger. Animals can walk, swim or fly… …plants can turn to face the light or close their leaves. Next > Movement Cells, and parts of cells, also move. For example, chemicals and molecules move to other parts of the cell that need them. If you were to examine a live cell using a microscope, you would see things moving about inside. Next > Respiration Living things need to take in oxygen and food to make energy. carbon dioxide oxygen The process that releases energy from these things is called respiration. Next > Respiration Cells carry out respiration. It is called cellular respiration. They use oxygen and glucose to produce energy in the form of a molecule called ATP. oxygen + glucose → carbon dioxide + water + energy (ATP) ATP is used by the cell to carry out the activities necessary for life. Next > Sensitivity Organisms need to be sensitive to their environment. They need to respond to danger, or to a change in light or temperature. Cells also need this ability to sense their environment. Next > Sensitivity For example, when a plant is placed in bright light, the cells on the darker side of the stem get longer. bright side of stem shaded side of stem light The cells on the lighter side stay the same. longer cells This causes the whole stem to bend towards the light. Next > Reproduction Cells are able to grow and reproduce. Each cell originated from a previous living cell. Mitosis Once mature, a cell can divide in half to produce two new identical cells. This process is called mitosis. All cells eventually die. Next > Reproduction The ability of cells to grow and reproduce in this way, allows organisms to grow and repair themselves. Next > Nutrition Cells need nutrients like oxygen, water and glucose (sugar). These nutrients are used to provide it with energy to live and grow. oxygen, water and glucose in Next > Nutrition All cells have a skin, called a cell membrane. This separates and protects the cell from its surroundings. The cell membrane regulates the movement of water, nutrients and waste products into and out of the cell. oxygen, water and glucose in cell membrane Next > Excretion Organisms must excrete (get rid of) waste products to stay healthy. This is the same for cells. oxygen, water and glucose in carbon dioxide and water out If waste materials are not excreted from a cell, they will poison the cell and possibly kill it. Next > Excretion During cellular respiration, carbon dioxide and excess water are produced as waste products. These must pass out of the cell through the cell membrane. waste carbon dioxide andproducts water out Next > Question 1 All cells of an organism must carry out each life process so that the organism can survive. Is this statement true or false? Answer True or False. Next > Question 1 All cells of an organism must carry out each life process so that the organism can survive. Is this statement true or false? Answer True or False. True Next > Question 2 According to the cell theory, cells carry out similar functions in order to sustain life. Which of the following can cells do? A) Use nutrients to make energy B) Get rid of waste materials C) Grow and reproduce D) All of the above Next > Question 2 According to the cell theory, cells carry out similar functions in order to sustain life. Which of the following can cells do? A) Use nutrients to make energy B) Get rid of waste materials C) Grow and reproduce D) All of the above Next > Question 3 Which of the following statements is NOT accepted in the Cell Theory? A) All living organisms are made up of many cells B) Cells are the basic unit of life C) Organisms and cells carry out similar functions in order to sustain life. D) All cells come from other cells Next > Question 3 Which of the following statements is NOT accepted in the Cell Theory? A) All living organisms are made up of many cells B) Cells are the basic unit of life C) Organisms and cells carry out similar functions in order to sustain life. D) All cells come from other cells Next > Summary In this presentation you have seen: the Cell Theory End >