General Exam Thoughts

[jasonml]

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yeah, i'll bet 3.8 would still get full marks.

[bheck7]

Originally Posted by jasonml

yeah, i'll bet 3.8 would still get full marks.

yeah it would, because it IS 3.8 GA

[ConquerDiscover]

Originally Posted by jasonml

3.6Ba, and can be proved with carbon 12/13 ratios

Yeah same i wrote about the carbon 12/13 ratio! Although, i said 3.8 Billion years ago.

[devilru]

I guessed 3.8 bill as well, wrote down 4.2 at the start then changed it. I knew it was carbon 12/13 ratios though.

[Aaron.Judd]

I tossed up between writing 3.8 and 3.5 billion years. 3.8 billion years is the age of the Australian contientn hence I reasoned it was 3.5 billion years (somewhere like Greenland life was discored of this age). So I went with 3.5 billion. They might be pretty specific though, i.e. if I was markign it I woudl allo 100 million years either side. I.e. if it is 3.6, I'd accept 3.5 - 3.7 and not 3.8 (especailly as that is the age of the Australian continent).

I too wrote about carbon 12:carbon 13 isotopic evidence.

[Quacker87]

But, it didn't specify that they were referring solely to the Australian stromatolite fossils. Plus, one of the syllabus points is; outline stable isotope evidence for the first presence of life in 3.8 x 109 year-old rocks and on Hsc Online, it states that using stable isotopes, evidence for life dating to 3800 million years has been found in rocks from Greenland, Australia and South Africa. So... I still think they would give marks for both 3.5 ba and 3.8 ba

[stolenhotelpen]

Originally Posted by jasonml

3.6Ba, and can be proved with carbon 12/13 ratios

yeah same, i think a range is acceptable. i said 3.5bya

[stolenhotelpen]

i totally forgot if it was carbon12/13..because i thought that can be only used for the past 50-60000years...??

but at least i only answered ONE of the options bahahaha

[henry08]

Originally Posted by stolenhotelpen

i totally forgot if it was carbon12/13..because i thought that can be only used for the past 50-60000years...??

but at least i only answered ONE of the options bahahaha

That is radioactive dating (absolute dating) using carbon, and carbon dating is only accurate to about 60,000 years.

[Forever Young]

I accidently wrote 1.8 instead of 3.8 and I realised it on my way home from the exam.

I talked about c 12 and c 13 in the second part, but I said that it shows that life was around 1.8 billion years ago, so I'm assuming that it's possible that I wont get any marks for the second part either?

[henry08]

If you wrote about carbon 12:carbon 13 isotopes, and got the date wrong you will defiantly get marks for part b and only los 1 mark for part a.