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Organisms Can Be Single-Celled or Multicellular

Organisms Can Be Single-Celled or Multicellular . Parkland 2012-2013. Multi-cellular organisms can: live in a wide variety of environments grow very large obtain their energy from a wide variety of foods have complex bodies specialize functions and work in harmony with other cells .

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Organisms Can Be Single-Celled or Multicellular

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  1. Organisms Can Be Single-Celled or Multicellular Parkland 2012-2013

  2. Multi-cellular organisms can: • live in a wide variety of environments • grow very large • obtain their energy from a wide variety of foods • have complex bodies • specialize functions and work in harmony with other cells Unicellular VS Multi-cellular

  3. Amoebas are common unicellular organisms that live in water. • They move around using foot-like projections called pseudopods (false feet). • They extend a pseudopod and the cytoplasm fills it. • The also use their pseudopods to capture food by surrounding it between two pseudopods and absorbing it. Common Unicellular Organisms –Amoeba

  4. Paramecium move swiftly through the fresh water where they live. • They are covered in hair-like structures called cilia, which move back and forth like little oars, moving it through the water. • Cilia also help gather food, by channeling the food to an oral groove, which is also lined with cilia, sweeping the food into the cytoplasm forming a food vacuole. Paramecium

  5. How Substances Move Into and Out of Cells Parkland 2012-2013

  6. The Cell Membrane • A cell membrane allows some substances to enter or leave the cell, while stopping other substances. • It is a selectively permeable membrane. • (A permeable membrane allows all materials through, while an impermeable membrane does not allow anything through)

  7. Activity 14

  8. High and Low Concentration • Ask a group of students to stand close together in one corner of the classroom and have the remaining students spread throughout the room. Have students identify which part of the room has the highest concentration of students. (The corner with the group of students has the highest concentration.) Show students the following diagram and have them decide which portion of the oval has a higher concentration of squares. • (Part A has the higher concentration.)

  9. High and Low Concentration Part A Part B

  10. Diffusion • The structure of the cell membrane controls what moves in or out of a cell. Particles - moving in all directions, bumping into each other, eventually spreading out evenly throughout the cell (diffusion). • Diffusion plays a part in moving substances into and out of a cell. • Concentration determines the direction that a substance takes through the cell membrane. • Particles move from higher concentration areas to lower concentration areas (equal concentration allows the movement of particles in and out equally – whereas, a higher concentration of particles on the inside of the cell will move to an area of lower concentration on the outside (so movement will only occur from inside to outside) • Until there is a balance.

  11. Osmosis • The diffusion of water through a selectively permeable membrane is called Osmosis. • Water helps to dissolve many of the substances involved in cell processes. When water is lost (moves out of the cell) it leaves behind a high concentration of the dissolved substances . • when water moves back into the cell, the substances become more diluted and can be used by the cell for it’s life functions.

  12. The Effect of Osmosis on Cells

  13. Your Task …This mark will be your design process mark. • Independent Practice: • Students will: • 1. Design an experiment proving membranes can be selectively permeable. • 2. Explain the process of diffusion. • 3. Describe how osmosis occurs. • 4. Compare and contrast diffusion and osmosis. • The procedure must be carefully organized in clear step by step procedures as well as written up. • You are responsible for all the supplies you will need. Be sure to practice your experiment at home before presenting it to the class. • Students perform their experiment and complete a written lab report.

  14. Two focus on a diffusion experiment and two focus on an osmosis experiment :

  15. Two focus on a diffusion experiment and two focus on an osmosis experiment :

  16. Big Ideas: • 1. Molecules move into and out of cells along a concentration gradient • 2. Cells have semi-permeable boundaries • 3. Molecules are constantly in motion • 4. The concentration of cells change with their changing environment • Essential Questions: • 1. Why do cells transport molecules in and out of their membranes? • 2. How do cells adapt to their environments? • What students will need to know and be able to do • (knowledge and skills): • 1. Design an experiment proving membranes can be selectively permeable. • 2. Explain the process of diffusion. • 3. Describe how osmosis occurs. • 4. Compare and contrast diffusion and osmosis. • 5. Identify a concentration gradient and its relationship to transport.

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