Fossils and Stuff

Question 1

Explain how the amount of potassium-40 can provide information about the age of the sample.

Answer 1

Potassium-40 is a radioactive isotope, it will decay into calcium-40 and argon-40. By measuring the amount of potassium-40 and argon-40 in a rock sample it is possible to calculate the age of the rock. As the rock ages, the proportion of potassium-40 decreases and the proportion of argon-40 increases.

Question 2

What types of samples are able to be dated using potassium–argon dating?

Answer 2

Rocks, of volcanic origin that are at least 100 000 – 200 000 years old.

Question 3

What types of samples are able to be dated using carbon-14 dating?

Answer 3

Organic samples that are less than 70 000 years old.

Question 4

Explain why the principle of superposition cannot be considered without taking other factors into account.

Answer 4

The principle of superposition assumes the layers of sedimentary rock are not disturbed through Earth crust distortions or through human activities of burial or mining.

Question 5

Describe index fossils and explain their relevance to relative dating.

Answer 5

Index fossils are distinctive fossils that were widely distributed and present on Earth for a limited period of time. They are used in correlation of rock strata and improve the reliability of relative dating of strata. If an index fossil is found in two strata layers, it can be confirmed that these strata layers are of the same age, even if they were located thousands of kilometres away from each other.

Question 6

Suggest what happens when potassium-40 decays to form calcium-40 and argon-40.

Answer 6

When Potassium-40 undergoes beta-decay, one neutron is converted to a proton, changing the atom to Ca-40. This occurs about 89% of the time. Around 11% of the time, K-40 undergoes electron capture which converts a proton to a neutron, changing the atom to Ar-40.

Question 7

Explain why carbon-14 dating can only be used to determine the age of samples that were once living.

Answer 7

Carbon-14 is formed in the upper atmosphere and enters the food chain through the process of photosynthesis converting the C-14 in the carbon dioxide molecule into a glucose molecule. The glucose is then consumed, and the C-14 isotope is assimilated into the body tissues of the organism. Once the organism dies the C-14 decays into nitrogen and the ratio of C-14 to C-12 can be measured.

Question 8

Potassium-40 half life

Answer 8

1250 billion years

Question 9

Carbon-14 half life

Answer 9

5730 years

Question 10

Polymerase chain reaction

Answer 10

• Enables small quantities of DNA to be replicated → produce testable amount.
• Steps are repeated 2-3 times in thermocycling.
• Takes ~2-3 hours to produce a billion DNA copies.
  Uses a heat-stable DNA polymerase like Taq polymerase, which is derived from the heat-loving bacterium Thermus aquaticus.

Question 11

PCR step temperatures

Answer 11

Denaturation - 94-96 degrees (temp breaks hydrogen bonds.)
Annealing - 50-60 degrees (primers bind, serve starting point of DNA replication.)
Extension - 70 degrees (DNA polymerase joins new, complementary nucleotides to sections with primer.)

Question 12

Restriction enzyme

Answer 12

• Added to DNA sample
• Cuts strand into different lengths dependent on the sample’s base sequence.
• Lengths of pieces can be analysed and compared with other DNA samples.
• Used before gel electrophoresis

Question 13

Gel Electrophoresis

Answer 13

Technique that is able to separate DNA strands based on their lengths.
- DNA ladder contains DNA fragments of a known length.
- Results from unknown sample can be compared to the ladder to determine the length of the DNA strands in the sample.

Question 14

DNA Sequencing

Answer 14

Determination of the precise order of nucleotides in a DNA sample.

Question 15

Ethics DNA

Answer 15

• Autonomy: respect for the right to be self-determining and to choose whether or not to be tested, and if tested, to know and share the information.
• Confidentiality: genetic information use is treated sensitively, and only accessed by those authorised.
• Equity: right to fair and equal treatment regardless of genetic information.
• Privacy: right to be ‘left alone’ to make decisions regarding genetic testing and resulting information, independent of others.

Question 16

bioinformatics

Answer 16

The digital storage, retrieval, organisation and analysis of biological data. Has drastically increased size, accuracy and scope of data sets.

Question 17

DNA hybridisation

Answer 17

process where DNA is compared.
- This means that the greater the similarities = the greater the attraction = the greater temperature needed to separate for DNA melting.
- Can be used with fossil dates to give an approximate separation date from ancestors.

Question 18

Would comparative DNA or comparative proteins provide more accurate data about their relationship? Justify your answer.

Answer 18

Comparative DNA. Comparative DNA will show mutations in nitrogen base sequence that do not affect the amino acid determined by that codon

Question 19

Isotope

Answer 19

atoms of the same element but with different neutron numbers.

Question 20

Endogenous Retroviruses

Answer 20

• Non-coding sequences of bases in DNA - junk DNA.
• The more junk sequences in common, the more closely related the species = common ancestor?
• Endogenous retroviruses are viral sequences that have become part of an organism’s genome.

Question 21

Mitochondrial DNA

Answer 21

• Has 37 genes, all essential.
• 24 contain code for making transfer RNA molecules.
• 13 contain instructions on making enzymes necessary for cellular respiration reactions.
  Easier to find and extract than DNA in nucleus.

Question 22

Mitochondrial DNA importance

Answer 22

Mitochondrial DNA only comes from egg.
Higher mutation rate than nuclear DNA:
- Amount of mutation is roughly proportional to amount of time that has passed.
- The more identical, the closer the ancestory.
- Can trace the migration routes of ancient peoples.
- Important in mapping relationships between species.

Question 23

Proteins

Answer 23

• Proteins are made from the arrangements of amino acids in specific orders.
• Differences in amino acid orders are due to differences in DNA sequence.
• Human haemoglobin sequence has 146 amino acid sequences.

Question 24

Ubiquitous proteins

Answer 24

proteins that appear in all organisms (i.e. Cytochrome C, haemoglobin).

Question 25

Fossil conditions

Answer 25

• Wet, acidic soil - minerals in bone dissolve, no fossilisation.
• No oxygen in soil (ie. peat) - complete preservation of soft tissues and bone.
• Alkaline soil is best:
  
  • Bone mineral doesn’t dissolve, and new minerals (lime or iron oxide) gets deposited in the bone’s pores, and replaces organic matter and petrifies the organism.
• If an organism dies on land, the remains are more likely to be destroyed by scavengers or erosion than to be buried by sediment.
• A place of low energy (lake/swamp) is best as remains are less likely to be destroyed by mechanical processes.
• The finer the sediment the better → enables soft tissues to be preserved.

Question 26

Accelerator mass spectrometry radiocarbon dating:

Answer 26

• A technique used to give radiocarbon dates for very small samples of material.
• Breaks sample up into its atoms so that the number of atoms of each isotope of carbon can be counted.

Question 27

What are Phylogenetic Trees good for

Answer 27

• Representing relationships.
• Organising knowledge of genetic diversity.
• Structural classifications.
• Simplifying relationships.

Question 28

Mitochondrial DNA uses

Answer 28

Mutations occur more readily in mtDNA (than in nuclear DNA)
Similarities in MtDNA between traditional owner and hair sample can be
used to identify relatedness
Number of mutations in mDNA of traditional owner and hair sample assessed
The less the diversity in their mtDNA
The more closely related they are