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Why…

Why…. …do bacteria not have a circulatory system?. Why…. …are polar bears really big?. Why…. …does a Robin have a higher rate of respiration than a Golden E agle?. Why…. …do elephants have lungs?. Small mammals or birds. Why….

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Why…

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  1. Why… …do bacteria not have a circulatory system?

  2. Why… …are polar bears really big?

  3. Why… …does a Robin have a higher rate of respiration than a Golden Eagle?

  4. Why… …do elephants have lungs?

  5. Small mammals or birds Why… …is the oxygen dissociation curve of a mouse shifted to the right? Human % sat Hb pO2

  6. Surface area to Volume Ratio • calculate the SA:Vol for a simple cube and identify how this changes with the size of the cube. Grade D. • describe how SA:Vol affects movement of substances and heat loss. Grade C • relate the anatomy of different organisms to their SA:Vol. Grade B

  7. Surface Area to Volume Ratio SA:Vol for short. -How does the SA: Vol change with the size of an organism? 3 2 1 54:27 54/27 = 2 24:8 24/8 = 3 6:1 6/1 = 6

  8. “the bigger the organism, the smaller the SA:Vol” 3 2 1 54:27 54/27 = 2 24:8 24/8 = 3 6:1 6/1 = 6

  9. The affect of SA:Vol on the transport of substances. • Cut out 2 cubes of gelatine (lengths of equal sizes). • Calculate their SA:Vol. • Half fill a petri dish with hydrochloric acid (goggles on!) • Place the cubes in the acid. • Time how long it takes for each cube to turn completely red.

  10. Practical analysis. • Which cube took up the acid the quickest? • Relate this to the SA:Vol of the cubes. How does the rate of diffusion change with the SA:Vol. • Use the above rule to answer the following questions… • Explain why bacteria do not need a circulatory system. • Explain why Elephants have lungs.

  11. The affect of SA:Vol on the transport of substances. • Substances will diffuse more quickly into organisms with abigger SA:Vol. • Bacteria are small-they have a large SA:Vol. Substances will diffuse very quickly into the centre of them through the plasma membrane. There is no need for a mass transport system such as the blood. • Elephants are very large-they have a small SA:Vol. Substances would take a long time to diffuse into the centre of the an elephant. They therefore need a mass transport system (blood and lungs)

  12. The affect of SA:Vol on Heat loss. Which organism is going to loose heat more quickly and why? (note: these both live in china!) or Mouse. It has a large surface area-more area to lose heat from and a smaller body-heat will travel to the surface more quickly.

  13. The affect of SA:Vol on heat loss • Organims with a bigger SA:Vol (smaller organisms) will lose heat more quickly. • Smaller organisms therefore tend to have a higher metabolic rate (faster rate of respiration) as this generates heat. • Their haemoglobin is adapted for this-the oxygen oxygen dissociation curve is shifted to the right- haemoglobin has a decreased affinity for O2so it is unloaded more easily at the muscles.

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