Instructor’s Copy



Download 1.27 Mb.
Page3/4
Date09.05.2021
Size1.27 Mb.
1   2   3   4

Cranial Capacity


D. Measure the diameter in centimeters of the circle in each skull. The diameter is the distance across the exact center of each circle.
E. Multiply the cranial diameters by 200 cm2. This gives the cranial capacity (brain volume) in cubic centimeters.
F. Record the cranial capacity for each skull in line 6 of Table 1.
NOTE: This method of measuring cranial capacity differs from the method used when an intact skull is available.


Part II: Jaw and Teeth Characteristics

Jaw Angle (Prognathism)


In front of each skull are two heavy lines, one running parallel to the slope of the upper jaw and one

running through the nose. These two lines are to be used for measuring how far the jaw protrudes



forward.
G. With a protractor, measure the outside angle formed by the two lines in each skull (the angle toward the right).

H. Place the protractor onto each skull as shown in Figure 2. Read the angle to using the outside scale on the protractor. The angle is read where the lower skull line crosses the protractor.
I. Record the angles in line 7 of Table 1. An angle of less than 90o means that the lower jaw sticks out in front of the nose. An angle of 90o means that the lower jaw does not stick out in front of the nose. Complete line 8 of Table 1.
Sagittal Crest

A bony ridge running across the top of a skull for muscle attachment is called a sagittal crest. This bony ridge is associated with heavy temporal muscles used to move the lower jaw.


J. Indicate in line 10 of Table 1 whether or not a brow ridge is present.
Number and Types of Teeth

Use the diagrams in Figure 3 for this part of the investigation.


K. Count and record the number of teeth for each lower jaw inline 11 of Table 1.


L. Count the number of each tooth type for each lower jaw. “M” on Figure 3 is for molar, “P” is for

premolar, “C” is for canine, and “I” is for incisor.


M. Record in lines 12 to 15 of Table 1 the tooth type totals.
N. Record in line 16 of Table 1 the size of canine teeth in each lower jaw.
O. A diastema is a space between teeth. One can see a space in the lower jaw of the gorilla between

the incisor and canine teeth. When the jaws were closed, the diastema allowed room for the large

incisor teeth of the upper jaw. Record in line 17 of Table 1 if a diastema is or is not present in

each lower jaw.


Lower Jaw Shape

The distance across the jaw backs compared to the distance across the jaw fronts can be used to determine jaw shapes of the three organisms in Figure 3.


P. Measure in centimeters the distance across each jaw from one dot to the other on the back molar

teeth.
Q. Measure the distance across each jaw using the dots on the front pre-molar teeth.


R. Record the distances for each jaw in lines 18 and 19 of Table 1. The distance across the back and

front of a lower jaw will help to determine if the jaw is U- or V-shaped.


S. If the distance across the back of the jaw is the same as the distance across the front of the jaw,

the jaw has a U shape. If the distance across the back is greater than the distance across the front,

the jaw has a V shape. Complete lines 20, 21 and 22 of Table 1.
Pelvis Shape

Examine Figure 4. It shows the pelvises of our three skeletons from a side view. A line has been drawn across each one to indicate top and bottom.



T. Record in line 23 of Table 1 if the top half of each pelvis is wide and short or narrow and long.


U. Record in line 24 of Table 1 if the bottom half of each pelvis is short or long.

Table 1: Comparison of Gorilla, Australopithecus and Modern Human Skulls




Skeleton Part

Gorilla

Australopithecus

Modern Human

1. Face area

42


25

16

2. Brain area

30


30

48

3. Is brain area smaller than face area?

Yes


No

No

4. Is brain area larger than face area?

No


Yes

Yes

5. Is brain area 3 times larger than face area?

No


No

Yes

6. Cranial capacity in cm3

700


760

1200

7. Jaw angle

37o


53o

90o

8. Does lower jaw stick out in front of nose?

Yes


Yes

No

9. Sagittal crest present

Yes


Yes

No

10. Brow ridge present

Yes


Yes

No

11. Number of teeth in lower jaw

16


16

16

12. Number of molars in lower jaw

6


6

6

13. Number of premolars in lower jaw

4


4

4

14. Number of canines in lower jaw

2


2

2

15. Number of incisors in lower jaw

4


4

4

16. Size of lower jaw canines

1.5


.4

.4

17. Diastema present

Yes


No

No

18. Distance across back of jaw

2.5


3.0

3.0

19. Distance across front of jaw

2.5


2.0

2.0

20. Is distance across front and back of jaw

the same?



Yes

No

No

21. Is lower jaw U-shaped?

Yes


No

No

22. Is lower jaw V-shaped?

No


Yes

Yes

23. Shape of top half of pelvis

Narrow & long

Wide and short

Wide and short

24. Shape of bottom half of pelvis

Long


Short

Short

Analysis
1. Using items 1-5 of your data in Table 1, describe the general change in face to brain area seen in

the three animals studied. In going from gorilla to Australopithecus to human, the brain area






Share with your friends:
1   2   3   4




The database is protected by copyright ©essaydocs.org 2020
send message

    Main page