Why Living Things Need Transport Systems
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Why Living Things Need Transport Systems
Understanding biological transport in multicellular organisms Year 9 Science - New Zealand Curriculum 60-minute lesson
Think About This...
Why do humans have a heart and blood vessels instead of just relying on oxygen moving around freely? How do you think substances move in a single-celled organism compared to a human?
What is Diffusion?
Movement of particles from high concentration to low concentration Happens naturally - no energy required Works well over SHORT distances Examples: oxygen entering cells, carbon dioxide leaving cells
Surface Area to Volume Ratio Investigation
Using clay or cubes, create shapes of different sizes Calculate surface area and volume for each Find the SA:V ratio Discuss: How might these changes affect diffusion?
Surface Area to Volume Relationship
Why Multicellular Organisms Need Specialised Transport Systems
Diffusion alone is TOO SLOW for large organisms Distance from surface to center is too great Cells in the middle would die waiting for oxygen Transport systems deliver substances quickly throughout the body
Diffusion vs Transport Systems
{"left":"Single-celled organisms: Diffusion works well\nShort distances\nSimple structure\nNo energy cost","right":"Multicellular organisms: Need transport systems\nLong distances\nComplex structure\nRequires energy but much faster"}
Key Takeaway
"As organisms become larger and more complex, they cannot rely on diffusion alone. Specialised transport systems evolved to efficiently move substances throughout the body."