Question

1. Difference between concave and convex survivorship curve.
2. Difference between Malthusian and logistic strategy.

Answer 1

1..Concave is synonymous with concave down, while convex is (nearly) synonymous with concave up. A straight line is convex, but not strictly convex.

A function f is said to be convex if a line segment connecting two arbitrary points on the curve is "above" the curve. Which is to say, that for every point (x, y) in said line segment, y is at least as large as f(x). It is strictly convex if every such point (other than the endpoints of the segment) has y>f(x). It is concave if -f is strictly convex.  

For twice differentiable functions, we can say it is convex on any interval the second derivative is non-negative