In many parts of the world, killer whales prey on fishes or marine mammals, but not both. Worldwide, killer whales have been observed preying on more than 140 species of animals, including many species of bony fish, sharks and rays, and 50 different species of marine mammals.
A coordinate system is a two-dimensional number line, for example, two perpendicular number lines or axes. This is a typical coordinate system: The horizontal axis is called the x-axis and the vertical axis is called the y-axis. The center of the coordinate system (where the lines intersect) is called the origin. The axes intersect when both x and y are zero. The coordinates of the origin are (0, 0). An ordered pair contains the coordinates of one point in the coordinate system. A point is named by its ordered pair of the form of (x, y).
To find out the coordinates of a point in the coordinate system you do the opposite. Begin at the point and follow a vertical line either up or down to the x-axis. There is your x-coordinate. And then do the same but following a horizontal line to find the y-coordinate. A relation is a set of ordered pairs. The first coordinate (usually the x-coordinate) is called the domain and the second (usually the y-coordinate) is called the range. If you remember from earlier chapters the domain contains values that correspond to the independent variable whereas the range contains values corresponding to the dependent variable.