2009 Biology Unit 3 Exam Suggested Solutions

[simpak]

I said in a greenhouse because then the conditions could be controlled properly for both groups but I suppose if you monitored it properly a field would be sweet?

[Katura]

hey im totally new here but just wondering -
that question - i said that wasps will eat the caterpillars when they land on the tomato plant
can i still get that mark?

[shinny]

Select 50 tomato plants of similar size, yield and species. 25 of the plants will make Group A, 25 for Group B. Expose Group A to caterpillars, and Group B to none. Place Group A and Group B 50m apart outdoors, and place a wasp nest/colony between the two setups. Observe the behaviour of the wasps over 1 week.

If the wasps migrate to the caterpillar exposed Group A, then the hypothesis is supported that jasmonic acid will attract the wasps.

I thought I nailed that haha despite a weird setup
+ I said outdoors in a field because it sounds like jasmonic acid goes into the atmosphere, and you can't have the plants too close together then??

This applies to Greggler as well since it was nearly an identical set up, the major problem is you don't only have one changing variable. You're trying to measure the impacts of jasmonic acid, but you've added jasmonic acid AND caterpillars. Well in laymans terms, even if they do go to A, how do you know they didn't go to A just due to being lured by the presence of caterpillar munchies there? From Greggler's set up, all you had to do was add one extra step; remove the caterpillars from the first group before exposing them to the wasps =T Anyone find fault with the experiment now?

hey im totally new here but just wondering -
that question - i said that wasps will eat the caterpillars when they land on the tomato plant
can i still get that mark?

Probably, since it was a 1 mark question.

[Greggler]

jasmonic acid  was only released as a result of the caterpillars - so arent you stilll really only adding one thing?

[shinny]

Look at it this way, if you were covered in giant ferocious man-eating caterpillars which caused you to bleed all over, and then mozzies came along and bit the crap through you, would you attribute that to your blood, or the presence of the caterpillars? On the other hand, assuming that the blood has no signalling capabilities whatsoever towards wasps, if some even more oversized frenzied wasps come along and ate the caterpillars, then it was the presence of the caterpillars that caused the wasps to come, and not the blood. As I hope you can see from my incredibly crap metaphor which I now realise doesn't actually have any real purpose, basically what I tried to say is that it could go either way at the moment as we're not sure whether the jasmonic acid actually has any signalling capabilities or not towards wasps, and I think you're looking at your own experiment with the bias that it does, which isn't necessarily the case. If it doesn't and the wasps come anyway, then clearly that's just because of the presence of the caterpillars, but your experiment isn't able to make this distinction.

EDIT: On re-reading your post, your main misconception is that you're basically saying that if A caused B, and A or B caused C, then B causes C, and this will prove the hypothesis. This might seem quite logical as if it was B that causes C in the second statement, then all's good. Then if it was A that causes C, well A causes B anyway, and apparently, all's still good. However they're asking specifically if the odour attracted the wasps, and so the second situation I've stated isn't a proof of the hypothesis they're asking you to prove as that by no means shows that B causes C (only that A causes C), or in other words, that the odour attracts the wasps.

[rhjc.1991]

OMG, I can do about 1/10 of the paper just on my Chem knowledge! Shows how much AOS2 uses up Bio knowledge.

[Greggler]

mmm im really confused now, hope i still end up with a few marks

[shinny]

mmm im really confused now, hope i still end up with a few marks

You definitely will if you complied with the rest of the experimental design concepts such as having many repeats, keeping other factors all the same etcetc.

[physics]

i am scared for AOS 2

[qshyrn]

it says on the vcaa site that biology gets marked by a single marker, but many many people have said they have two people marking your exam then add it out of 150 or something? 
im confused..
"For Mathematics, Accounting, Biology, Chemistry and Physics, examination papers are marked by a single marker. This is because in these examinations experience shows there is little or no difference in the marks given by pairs of markers marking the same paper."  -http://www.vcaa.vic.edu.au/vce/exams/gat/relates.html

(whoops i think i should have posted this under "The exam section")

[nerd]

This year all of the subjects you mentioned are being marked twice. See this VCAA memo: http://www.vcaa.vic.edu.au/correspondence/memorandums/2009/46.html

[qshyrn]

o ook thx

[TrueLight]

that's what jasmonic acid does in reality...

[qshyrn]

i never had caterpillars or leaves involved in my experiment , the jasmanoic acid and its different derivatives are releaesd (in a specific area)on seperate trials in an enclosed space
100 wasps are in that inclosed space
trials are repeated many times
the variables in each of the trials are same with the other trials except which chemical released
if they fly to the area which jasmanoic acid has been released then the hypothesis is supported


i think i worded my experiment real badly in the exam.
may have lost marks.
BTW: the above is basically what i wrote in the exam, but should i have said there will also be a control trial, where 100 wasps are there w/out the chemical released?? (immediately after the exam i thought i should have put this in)- would i lose marks for not putting this in?

[shinny]

andrewloppol, I think the fact that you mentioned 50 metres MIGHT cover your bases for separating the two variables for the reasons you've stated. As for alternatives, well yeh, what I said was to do Greggler's experiment, but then remove the caterpillars after the jasmonic acid has been secreted.