10.4 4.2.5 fossils  (Page 4/4)

3.The modern coelacanth-finding throws doubt on an assumption palaeontologists use when reasoning about what the fossil record says about extinctions.

• What is the assumption the modern coelacanth-finding throws doubt on?
• How does the modern coelacanth-finding throw doubt on this assumption?

4.Look at these premises:

• A cadborosaurus was found in the stomach of a whale in 1993 .
• A pterodactyl was killed at Culment, France, in 1856 .
• Blood vessels, red blood cells, osteocytes and proteins have been found in unfossilized dinosaur bones .
• Undamaged DNA pieces have been found in insects fossilised in amber (a sticky plant resin).
• Unfossilised bones, blood vessels, blood cells and DNA break down quickly .
• The extinction of the dinosaurs is assumed at more than 60 million years ago.

Give a conclusion which follows from these premises

5.A rock is found to have a K:Ar ratio of 1:10. Its age is calculated as 4,37 x109 years.

1. K (potassium) is the parent element. Ar (argon) is the _________________ element.
2. What data is used to do this calculation?
3. What conclusion/inference is made from this data?
4. Name two assumptions used when making this conclusion from this data:
5. Give a counterargument, showing how this same data could fit with a young age.

Activity: Fossils: Suggested Answers

1.Name / give the term for:

1. Turning to stone Petrifaction
2. A fossil in which the surroundings became stone, leaving a cavity where the body had been Mould
3. The time period and era, according to the geological column, when dinosaurs first appeared Triassic period; Mesozoic era
4. The time period and era, according to the geological column, when dinosaurs became extinct Cretaceous period; Mesozoic era
5. A person who studies fossils Palaeontologist
6. A person who studies rocks Geologist
7. Layers of deposited material Sediments / Strata
8. No members of that organism exist anymore Extinct
9. The time era, according to the geological column, when mankind evolved Cenozoic

2.For each of the following sentences, say whether the information is: (Circle i / ii / iii)

1. Accepted by definition if people have defined this to be so, or
2. Known by observation if people have observed this to be so, or
3. Deduced if people have come to this knowledge by reasoning.

1. During petrifaction, minerals enter, harden, and turn a body to stone.[ i / ii / iii]Observed and Defined
2. The Triassic Period is more recent than the Permian Period. [ i / ii / iii]
3. Defined
4. The oldest fossils are 650 million years old. [ i / ii / iii]Deduced
5. A film fossil is a carbon mark left on rock e.g. by leaves. [ i / ii / iii]Defined
6. The deepest rocks with reptile fossils are classed as Carboniforous. [ i / ii / iii]Defined
7. Reptiles first evolved 350 million years ago, at the start of the Carboniforous period. [ i / ii / iii]Deduced
8. Only 2/3 of all types of organisms which have ever lived have left any fossils.
   1. [ i / ii / iii]Deduced

3.The modern coelacanth-finding throws doubt on an assumption palaeontologists use when reasoning about what the fossil record says about extinctions.

1. What is the assumption the modern coelacanth-finding throws doubt on? An extinction event can be recognised by fossils of that type not being found in higher (i.e. younger) rock.
2. How does the modern coelacanth-finding throw doubt on this assumption? Although no coelacanth fossils are found in rock younger than that assumed to be 100 million years old, coelacanths are not extinct: they are alive today(extant).

4.Look at these premises:

• A cadborosaurus was found in the stomach of a whale in 1993.
• A pterodactyl was killed at Culment, France, in 1856.
• Blood vessels, red blood cells, osteocytes and proteins have been found in unfossilized dinosaur bones.
• Undamaged DNA pieces have been found in insects fossilised in amber (a sticky plant resin).
• Unfossilised bones, blood vessels, blood cells and DNA are known to break down quickly.
• The extinction of the dinosaurs is assumed at more than 60 million years ago.

5.A rock is found to have a K:Ar ratio of 1:10. Its age is calculated as 4,37 x109 years.
a) K (potassium) is the parent element. Ar (argon) is the daughter element.
b) What data is used to do this calculation? The K:Ar ratio .
c) What conclusion/inference is made from this data? The rock is 4,37 x109 years old .
d) Name two assumptions used when making this conclusion from this data:
All the Ar in the rock came from radioactive decay of the K. This radioactive decay happened at the same rate as it had in the past.
e) Give a counterargument, showing how this same data could fit with a young age.
The rock might have started with a lot of Ar in it. The conditions in the past might have caused K to decay into Ar at a higher rate than today. Further,Argon is known to move easily through rocks, so the Ar might not all have come from radioactivity.