Hoofed Animals Such as Cattle and Sheep Are Classified as Browsers

question 9

Essay

Hoofed animals such as cattle and sheep are classified as browsers (leaf eaters) and
grazers (grass eaters). Some biologists believe that the incisor arcade of the teeth,
diagrammed below, is shaped differently for browsers and grazers, affecting their
food selection. The "curvature" of an incisor arcade is a measure of its shape; large
values indicate a longer, thinner mouth and small values a shorter, wider mouth. The
back-to-back stem-and-leaf plot below compares the curvatures of incisor arcades for
different species of browsers and grazers. Curvature, Browsers vs. Grazers
Browser species $\quad$ Grazer species
N=18 $\quad$$\quad$$\quad$$\quad$ N=54

$\begin{array}{l}&|1 \mathrm{H}|& 9 \\&|2 \mathrm{~L}|& 1 \\&|2 \mathrm{H}|& 889\\413 &|\mathrm{~L } |& 22244\\99885&|3H|&55566667778999999\\410&|4L|& 022223\\99987&|4 H|&55556666677778889\\321 &| 5 L|& 03\\&|5 \mathrm{H}|& 9 \\&|6 \mathrm{~L}| &0 \\&|6 \mathrm{H}| &\\&|7 \mathrm{~L}| &\\0&|7 \mathrm{H}|&\end{array}$
(a) Briefly describe each distribution, noting any unusual features of the data.
(b) Some biologists believe browsers have thinner mouths because leafed plants
frequently have thorns and spines. They think that browsers have evolved thinner
mouths to get beyond the thorns and spines to the food part of the plant. Are the
data in the back-to-back stem-and-leaf plot consistent with this theory? Justify
your answer by appealing to specific aspect(s) of the plot.

---

Definitions:

Levator Palpebrae Superioris

A muscle in the orbit that elevates the upper eyelid.

Inferior Oblique

A muscle in the eye that participates in the outward and upward movement of the eyeball, one of six extraocular muscles that control eye movements.

Glaucoma

A disease of the eye characterized by increased intraocular pressure.

Ocular Discharge

A fluid that comes from the eye, often a sign of infection, irritation, or other eye conditions.