Below is the graph of a quadratic function, showing where the function is increasing and decreasing. If we draw in the tangents to the curve, you will notice that if the gradient of the tangent is ...

Mollusc Community Patterns and Species Response Curves along a Mineral Richness Gradient: A Case Study in Fens, Journal of Biogeography, Vol. 33, No. 1 (Jan., 2006), pp. 98-107 ...