The frequent droughts of the African bush require that trees must be able to store water and reduce evaporation. The baobab stores water in its fat trunk (up to 26,000 gallons). To reduce evaporation, it keeps its surface area small by quickly scaling down branches. In our simulation this means the self-replicating or "active" line is small in comparison to the passive lines. What happens if you adjust that? How might evolution take advantage of that system?
What is the evolutionary advantage of fractals? They combine a maximum of surface area with a maximum of flow, so trees take in more light, lungs exchange more oxygen, kidneys filter more waste, neurons connect with more neurons. Plants in the desert need to conserve water, so they tend to have a lower fractal dimension (a cactus has less surface area per volume than a fern). And DNA itself is a recursive loop, so it may be that fractals naturally arise from mutation.
In 1510, Leonardo Da Vinci wrote: "All the branches of a tree at every stage of its height when put together are equal in thickness to the trunk." Thus, if a "mother" branch produces two "daughter" branches, the area of a cross-section of the mother is equal to the sum of the areas of the cross-sections of the daughters. This means that the ratio of the daughter-diameter to the mother-diameter will be about 0.707 -- can you show why? Can you find the ratio for mother branch length to daughter branch length?
In botany, the growing tip is called an "apical meristem." Press "edit" and you will see two red lines representing the apical meristems. Click off "snap to grid" and then change the size and angle of the red lines by dragging their endpoints.
Click the "Seed" drop-down menu under "Edit Mode" to select "Davinci Tree 3" or "Davinci Tree 4" for trees with higher branch numbers.