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Life processes and unicellular organisms

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Notes de leçon

Life Processes (MRS GREN)

  • All living organisms perform seven life processes, remembered by the acronym MRS GREN.
  • Movement: All living things move; plants grow towards light, animals move to find food or escape danger.
  • Respiration: A chemical reaction that releases energy stored in glucose.
  • Sensitivity: Living things sense changes in their environment and respond (e.g., humans feel heat, plants grow towards light).
  • Growth: Organisms increase in size; unicellular organisms grow by increasing cell size, multicellular by producing more cells.
  • Reproduction: The process of producing offspring.
  • Excretion: The removal of waste products from the body.
  • Nutrition: Plants photosynthesise; animals eat plants or other animals.

Unicellular Organisms

  • Unicellular organisms are living organisms made of just one cell.
  • Despite their small size, they perform all seven life processes.
  • Examples include bacteria, euglena, amoebas, and yeast (a fungus).

Bacteria

  • Bacteria are some of the most common and diverse unicellular organisms.
  • They do not have a nucleus; genetic material is located in the nucleoid and plasmids.
  • Some bacteria have a long tail called a flagellum for movement.
  • Bacteria have a cell wall, cell membrane, and ribosomes.

Euglena

  • Euglena is a unicellular organism found in water.
  • It has a flagellum to help it swim.
  • It contains chloroplasts for photosynthesis.
  • It also has an eyespot for light sensitivity (not mentioned in source, but typical; source only mentions flagellum and chloroplasts).

Other Unicellular Organisms

  • Amoebas are unicellular organisms that move and feed using pseudopods.
  • Yeast is a unicellular fungus used in baking and brewing.

Structure of a bacterium, a unicellular prokaryote.

Bacterial cellCell wallCircular DNAPlasmidRibosomesFlagellum

Euglena, a unicellular organism with a flagellum and chloroplasts.

EuglenaFlagellumChloroplastNucleusArt: sciencefigures.org

Diapos

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Questions d'entraînement

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  1. 1.How many life processes do all living organisms perform?

    Easy
    • ASeven
    • BFive
    • CSix
    • DEight
  2. 2.What does the acronym MRS GREN help us remember?

    Easy
    • AThe life processes of living organisms
    • BThe parts of a bacterium
    • CThe organelles of a euglena
    • DThe types of unicellular organisms
  3. 3.Which of the following is NOT a life process?

    Easy
    • APhotosynthesis
    • BRespiration
    • CExcretion
    • DSensitivity
  4. 4.Which statement about unicellular organisms is correct?

    Easy
    • AThey are made of one cell and perform all life processes.
    • BThey are made of many cells and perform only some life processes.
    • CThey are made of one cell and perform only some life processes.
    • DThey are made of many cells and perform all life processes.
  5. 5.Which of the following is an example of a unicellular organism?

    Easy
    • ABacterium
    • BHuman
    • COak tree
    • DMushroom
  6. 6.Bacteria do not have a nucleus. Where is their genetic material located?

    Easy
    • AIn the nucleoid and plasmids
    • BIn the nucleus
    • CIn the cytoplasm
    • DIn the cell wall
  7. 7.What is the function of the flagellum in some bacteria?

    Easy
    • AMovement
    • BRespiration
    • CReproduction
    • DNutrition
  8. 8.Which process is defined as 'a chemical reaction that releases energy stored in glucose'?

    Easy
    • ARespiration
    • BPhotosynthesis
    • CExcretion
    • DNutrition

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