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Gas Exchange & Circulation

Gas Exchange & Circulation. Chapter 4. Gas Exchange in Animals. Why is gas exchange important?. Respiration:. C 6 H 12 O 6 + O 2  Energy + CO 2 + H 2 O. Photosynthesis:. Energy + CO 2 + H 2 O  C 6 H 12 O 6 + O 2. How can an organism get O 2 into its body?. Diffusion.

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Gas Exchange & Circulation

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  1. Gas Exchange & Circulation Chapter 4 Gas Exchange in Animals

  2. Why is gas exchange important? Respiration: C6H12O6 + O2 Energy + CO2 + H2O Photosynthesis: Energy + CO2 + H2O  C6H12O6 + O2

  3. How can an organism get O2 into its body? Diffusion.

  4. How can an organism get O2 into its body? • For very small organisms, diffusion is fast enough to supply O2. • O2 use is correlated with body mass (or volume), but diffusion rate depends on surface area... • and larger organisms have lower surface area/volume ratios.

  5. surface area/volume ratio

  6. How do animals get O2? How do animals get O2? • Diffusion alone is enough for animals up to about 1 mm thick... • depending on rate of O2 use. • Larger, faster animals need tricks to speed up diffusion.

  7. O2 diffuses from high concentration to low concentration.

  8. Speeding up diffusion • Gases diffuse from higher to lower concentration. • Concentraion must be lower in organism than in environment. • Will organism get enough O2? Depends on rate of O2 use and diffusion. • Large, active animals have tricks to speed up diffusion.

  9. Big aquatic animals usually have gills to provide surface area for gas exchange.

  10. Fish usually need more oxygen than invertebrates; they have more gill area than most invertebrates.

  11. Faster fish have bigger gills. index of relative gill surface area Mackerel: 2551 Toadfish: 137

  12. Speeding up diffusion Increase gill surface area; have thin gill epithelium. Pump water across gills. Pump blood through gills.

  13. Operculum in Fish 1-way flow of water across gills

  14. How fish speed up diffusion: ventilation • Fish use energy to pump water across gills (ventilation). • At low speed, opercular pumping is used. • Counter current of blood flow over gills

  15. Fish gill structure

  16. Countercurrent exchange of O2 in gills

  17. Countercurrent exchange of O2 in fish gills • Water & blood flow opposite directions. • This maximizes the concentration gradient & speeds up diffusion. • Equilibrium is never reached.

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