Certainly! Let's go through each part of the question in detail:
### 8.1 Name the two main types of methods used to determine the age of fossils.
The two main types of methods used to determine the age of fossils are:
1. Relative Dating: This method involves determining the age of a fossil in relation to other fossils or rock layers. It often involves techniques like stratigraphy and biostratigraphy.
2. Absolute Dating: This method provides a more precise age estimate by measuring the decay of radioactive elements within the fossils or the surrounding rocks. Techniques like radiocarbon dating (for relatively recent fossils) and uranium-lead dating (for older fossils) are commonly used.
### 8.2 Calculate the value of:
#### (a) [tex]\( X \)[/tex]
The value [tex]\( X \)[/tex] represents the number of years for 5 half-lives of carbon-14 decay. Considering the half-life of carbon-14 is 5730 years:
[tex]\[ X = 5 \times 5730 \][/tex]
[tex]\[ X = 28650 \][/tex]
Thus, [tex]\( X = 28650 \)[/tex] years.
#### (b) [tex]\( Z \)[/tex]
The value [tex]\( Z \)[/tex] represents the percentage of original carbon-14 remaining after 5 half-lives.
Each half-life reduces the amount of carbon-14 by half.
Starting with 100%:
After 1 half-life: [tex]\( \frac{100}{2} = 50\% \)[/tex]
After 2 half-lives: [tex]\( \frac{50}{2} = 25\% \)[/tex]
After 3 half-lives: [tex]\( \frac{25}{2} = 12.5\% \)[/tex]
After 4 half-lives: [tex]\( \frac{12.5}{2} = 6.25\% \)[/tex]
After 5 half-lives: [tex]\( \frac{6.25}{2} = 3.125\% \)[/tex]
Thus, [tex]\( Z = 3.125\% \)[/tex].
### 8.3 Explain why it would not be possible to date a fossil that existed 80 million years ago using the decay of carbon-14.
It is not possible to date a fossil that existed 80 million years ago using carbon-14 dating because the half-life of carbon-14 is 5730 years. After about 10 half-lives (approximately 57,300 years), the remaining amount of carbon-14 would be extremely minimal and difficult to measure accurately. Therefore, for fossils that are millions of years old, other dating methods like uranium-lead dating or potassium-argon dating, which have much longer half-lives, are used.
### 8.4 Give TWO reasons why there are gaps in the fossil records.
1. Inadequate Fossilization Conditions: Not all organisms have the same potential to fossilize. Soft-bodied organisms or those that decompose quickly are less likely to be preserved as fossils compared to hard-bodied organisms. Environmental factors play a crucial role in ensuring that remains are buried quickly and protected from scavengers and decay.
2. Geological Processes: Over millions of years, geological processes like erosion, tectonic activity, and sedimentation can destroy existing fossils or bury them so deeply that they have not yet been discovered. Additionally, some fossils may remain undiscovered due to their location in unexplored or inaccessible areas.
By following these steps, we have thoroughly addressed each part of the question with clear and logical explanations.
