help with exam qsts.

[lacoste]

Question 4.
Radioisotopes are used for dating fossils because they decay at a given rate. This rate of decay varies depending on the particular radioisotope used. If the half-life for carbon-14 is 5500 years and the amount of carbon-14 measured in a fossil is 1/16 of its original value then the age of the fossil is
A. 5500 years.
B. 11000 years.
C. 16500 years.
D. 22000 years.



Question 14.
Characteristics that could be used to distinguish a human skeleton and skull from the skeletons and skulls of a chimpanzee and gorilla include the
A. presence of incisor and molar teeth.
B. the reduced size of the jawbones and eyebrow ridge.
C. position of the braincase in the skull and the pelvic girdle in the spinal column.
D. location of the eye sockets in the skull and presence of jawbones.

[bturville]

Question 4.
Radioisotopes are used for dating fossils because they decay at a given rate. This rate of decay varies depending on the particular radioisotope used. If the half-life for carbon-14 is 5500 years and the amount of carbon-14 measured in a fossil is 1/16 of its original value then the age of the fossil is
A. 5500 years.
B. 11000 years.
C. 16500 years.
D. 22000 years.

If a half life is 1/2 the original value, then 1/16 is 4 half lives. So 4 x 5500 years = 22000 years.

Question 14.
Characteristics that could be used to distinguish a human skeleton and skull from the skeletons and skulls of a chimpanzee and gorilla include the
A. presence of incisor and molar teeth.
B. the reduced size of the jawbones and eyebrow ridge.
C. position of the braincase in the skull and the pelvic girdle in the spinal column.
D. location of the eye sockets in the skull and presence of jawbones.

you need to know all the differences between modern humans and prehistoric human skulls, eg. brow ridges, brain cavity size, position of foramen magnum and so on. make sure you know them.

[Faraz]

okay remember every half life is 5500 years

for the carbon to go from full to half it takes 1 half life

so 5500

for the carbon to go from half to 3/4 takes another half life

so 11000

for the carbon to go from 3/4 to 7/8 (Iam horrible at maths) it will take another half life

so 16500

and so on its really hard to explain but how it is everytime you want half the remaining it will take 1 half life (sounds better in my head)