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Cell Specialization Ch.37 The first cells were not specialized • Organisms were unicellular • The cell performed all cell functions This cell has to get energy, get rid of its waste, & reproduce all by itself! Multicellular organisms have specialized cells • Each cell has a specific job • Cells have special shapes and structures that relate to function This neuron is specialized to do one job– receive & send messages. Think of an analogy to compare and contrast unspecialized and specialized cells. How do you get from one cell to a multi-cellular animal? How do cells become specialized? What do you think happens? An organism starts off as one cell. That cell divides by mitosis during development. Fully developed Sea Urchin See… its already starting to look like something… Specialized cells develop from unspecialized STEM CELLS When a cell divides, the new cells don’t get the same stuff Each cell gets different chemicals & cells can affect their neighbors When a cell becomes specialized, some genes are turned on in that cell and others are turned off. If all of the cells expressed all of the genes in the DNA, the organism would grow up to be a blob. Not specialized Not specialized yet… Specialized! The “on” genes make their proteins which give the cell its special structures Questions? Your Turn - Write in Your Notebook: • How are unicellular organisms different from multi-cellular organisms? • How do cells in multi-cellular organisms become specialized? • What is the advantage of being multicellular? Cells are arranged to form multicellular organisms • Tissues – made of cells working together – Skin – Connective – Muscle • Organs – made of tissues working together – Heart – Lungs – Stomach • Organ systems – made of organs working together – Digestive system – Endocrine system – Circulatory system • Organism – made of organ systems working together – Human For now, tell me how you think this structure is related to its function: This is a crosssection of your intestines. What about this: This is the lining of your wind pipe (trachea) What about this? How does structure relate to function? These cells transport water through a plant (remember xylem?)