Puppy Growth Characteristics

I wrote earlier that puppies grow logarithmically (or exponentially, which is the flip side) for a period during early development. Plot the weight of the puppy on the ordinate, and time, the independent variable, on the abscissa (see the chart on the upper right of this page). If the ordinate values are plotted as the logarithm of the value, you will observe a straight line for those periods of growth that are exponential. Then, the slope of that straight line, when divided into ln 2 yields doubling time.

Here is such a plot for Kayla. I use her as an example because her time vs weight curve shows no lag or stationary phase. The red points are her actual weights, and I computed a linear regression (black line is the best fit) to estimate the slope. The slope of this line, m, is termed μ, the specific growth rate (y=mx+b, standard first order curve). In this case, μ = 0.088. So doubling time is td = ln 2/0.088 = 0.693/0.088 = 7.8 days. Kayla's weight doubles every 7.8 days.