1. WHY COULD INSECTS THIS LARGE NEVER EXIST? YouTube Tarantula Trailer

2. Exoskeleton too weak When shed exoskeleton when molting, collapse under weight Limits on nest size Respiratory capacity

3. Clicker Question warmup As the radius of a cell increases, the surface area to volume ratio of the cell a)Increases b)Decreases c)Stays the same d)Insufficient data to answer this question

4. A Review: Surface Area/Volume and Maximum Cell Size Volume of a sphere = 4/3πr 3 Surface area of a sphere = 4πr 2 Surface to volume ratio = 3/r nutrients wastes

5. Respiratory System of Insects Exoskeleton with waxy cuticle prohibits simple diffusion through epidermis No blood vessels, so no lungs Tube system that carries O 2 from surface to cells and takes up CO 2 Tracheal tube system

6. Tracheal volume data Length of BeetlesTracheal volume (as % of body volume) 17mm1.9% 18mm2.1% 27mm3.3% 47mm5.7% 60mm7.4% 62mm7.6% 80mm9.9% 129mm 15.8% Graph the data and determine the relationship between tracheal volume and beetle body length.

7. What is the mathematical formula describing the relationship between these two variables? A) x 2 + y 2 = 0 B) y = mx + b C) y = log x D) y = 1/x What does this information tell us about insect size and tracheal system size? Let’s do some math!

8. SMALL INSECT Oxygen depleted if tube diameter stays the same Large Insect Tracheole volume larger to accommodate needs SUMMARY OF THE PROBLEM LARGE INSECT

9. Based on your data, what is the theoretical maximum length of a beetle? The largest living beetle today actually is 170 mm. What do you think limits the body volume that an insect can devote to the tracheal system?

10. One step further… During the Carboniferous (350 mya) there were insects much larger than any found on Earth today. Develop a hypothesis from this observation. How would you test your hypothesis?