For Natural Science Guru labs

OBJECTIVES: Upon completion of the lab, the student will be able to:

describe how horses have changed over large periods of time

MATERIALS: pencil, computer/internet access, Lab 08 Report.

BACKGROUND READING:

Members of the early Eocene genus **Hyracotherium (at the bottom of the figure below) are the oldest known animals of the horse family, Equidae.

In rocks of the late Eocene and the succeeding epochs of the Cenozoic period, fossil remains of the horse family are abundant. Paleontologists have classified the animals represented by these fossils into 20 genera. By combining many kinds of structural evidence, they have arrived at some agreement about the relationships among 17 of these genera, as shown in figure below.

In this investigation, you will study only one of the characteristics that paleontologists have used. You will use the size of the horse’s jaw. In horse the grinding (aka cheek) teeth are in the back of the mouth, separated from the front teeth by a toothless space. On each side of each jaw the grinding teeth consist of three premolars, and three molars. Studying the distance spanned by these teeth will give us an indication of the size of the jaw. We can use the size of the jaw as an indication of the size of the horse.

The span of the cheek teeth has been measured in many horse fossils. Averages of the data are presented in table below. When plotted on a graph, these data suggest certain relationships.

PROCEDURE:

After reviewing the table, plot the data on the graph found on your lab report. For each species of horse in the data table there is a number associated with it you will use this number to identify each data point. DO NOT connect the data points until instructed to.

**Label the X axis with the span of the cheek teeth and the Y axis with the epoch (time of existence).

Once you have the points plotted, answer the questions found on your lab report. The lab report will direct you in connecting the points.

See Lab 08 Rubric for grading information.

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