Figure is a digraph representing a food web in a small ecosystem. A directed edge from a to b indicates that a has b as a source of food. Construct the adjacency matrix A for this digraph and use it to answer the following questions.

a. Which species has the most direct sources of food? How does A show this?
b. Which species is a direct source of food for the most other species? How dose A show this?
c. If a eats b and b eats c, we say that a has c as an indirect source of food. How can we use A to determine which species has the most indirect food sources? Which species has the most direct and indirect food sources combined?
d. Suppose that pollutants kill the plants in this food web, and we want to determine the effect this change will have on the ecosystem. Construct a new adjacency matrix A* from A by deleting the row and column corresponding to plants. Repeat parts (a) to (c) and determine which species are the most and least affected by the change.
e. What will the long term effect of the pollution be? What matrix calculations will show this?

Rodent Bear Plant Fox Insect Fish Bird