Biology

2006 Bio153S Lab 6 Assignment

Name:

Student Number:

Section and TA:

The cranium:

1) What modifications do you see in the bird skull that suggest adaptations to

the "avian lifestyle"? (2 marks)

The modifications that are seen in the bird skull that suggest adaptations to the "avian lifestyle" would be that the bones of the skull have fused together to make the cranium very lightweight. Since the cranium is very lightweight, it has less mass, making it easier for the birds to fly. Another modification that is seen in the bird skull is that there is no presence of teeth, which benefits the birds because it decreases their mass and maximizes its flight ease. The bird skull also has many airy canals which make the cranium even more lightweight and gives the bird less mass to carry which results in more flight ease. Another adaptation to the "avian lifestyle" would be the size of the orbits in the bird's skull. The birds' bone mass is reduced since the birds have orbits.

2) Why are the turbinate bones "honeycombed?" (2 marks)

The turbinate bones are "honeycombed" because it is designed to maximize the surface area of the mucous-secreting membrane as well as absorbing the energy of trauma by collapsing to protect the brain and the eyes.

3) The "Mystery Skull":

a) Do you think this animal is a carnivore, an herbivore, or an omnivore? What evidence did you use to draw this conclusion? (4 marks)

This animal is a omnivore. This conclusion is drawn on the basis of the fact that the skull is a mixture of herbivorous and carnivorous traits. For example, the premolars and molars of the skull were large and flat, which means that those teeth were used for grinding. The skull's canine teeth were very sharp however. These teeth must have been used for piercing its prey.

b) Can you guess its identity? (1 bonus mark)

The "mystery skull" is a bear.

The appendicular skeleton:

4) What is the ratio between the input and output lever arms in the cat and in

the rat? (1 mark each)

a) cat:

b) rat:

5) If the cat and the rat were the same size, which would have a stronger

forelimb? Which would have a faster forelimb? Are there any other factors that

might affect strength and speed other than lever arm ratios? Discuss. (4 marks)

If the cat and the rat were the same size, the rat would have a stronger forelimb since it's input lever