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October 18, 2019, 01:10:54 pm

Author Topic: VCE Biology Question Thread  (Read 1380974 times)  Share 

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Tyler_

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Re: VCE Biology Question Thread
« Reply #10650 on: September 16, 2018, 09:47:46 pm »
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Hey guys would someone be able to help me with this question? The correct answer is B btw:

The disease cystic fibrosis is caused by a gene mutation that produces an incorrectly formed protein channel, the CFTR (cystic fibrosis transmembrane conductance regulator). When this channel is not formed correctly, chloride ions will not be able to exit the cell. The accumulation of chloride ions causes the movement of water via osmosis.

Based on this information, which of the following are likely consequences of cystic fibrosis?

A. Large amounts of watery diarrhoea as chloride ions in the intestinal tract attract water.
B. Thick sticky mucus outside cells as water remains in the cell rather than move out via osmosis
C. Selective sodium channels provide an alternative passage of chloride ions.
D. Water will be actively transported into the cell following the accumulation of chloride ions.

I chose A as my answer because I thought that there would be a buildup of chloride ions inside the cell, meaning water would move into the cell via osmosis as the environment outside the cell would be hypotonic to the cell? Can someone explain why B is the correct answer instead? :P

That's a tricky one! A and B both sound very nice. Going by the wording, option A refers to "watery diarrhea" while the question asked for the best answer based on the "information alone". For this reason, maybe they say that B is the correct choice as it is talking about a symptom that is a direct result of the inability of water to diffuse out of the cell. After all, the best answer is the most correct and accurate based on the instructions. What a trap!!  :o

If anyone has a better idea, let us know! It's an interesting question.
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #10651 on: September 17, 2018, 09:42:29 am »
+4
“• the human fossil record as an example of a classification scheme that is open to interpretations that are contested, refined or replaced when new evidence challenges them or when a new model has greater explanatory power, including whether Homo sapiens and Homo neanderthalensis interbred and the placement of the Denisovans into the Homo evolutionary tree.”

I understand the “out of Africa” hypothesis and how it is suspected that Homos all originated from Africa and slowly migrated to other places and diverged from there. I also know a little bit about Homo sapiens and Neanderthals interbreeding, as a portion of humans in this present day have Neanderthals DNA in them. And Denisovans was placed into the Homo  evolutionary tree, due to the fact that they interbred with Homo sapiens and Neanderthals.

What I typed up just then, sums up about all I know for this study design dot point. Can anyone expand on this to the level of what I need to know?

This is what I had in my notes:
Spoiler
The fossil record of hominins is very poor because:
-Fossilisation is an extremely rare event.
-Hominins don’t/didn’t live in places conducive to fossilisation.
   A lot of our fossils have come from underwater, or areas that were underwater when the fossils formed.
-Hominins have behaviours that make fossilisation unlikely.
   Burying our dead often prevents fossilisation from occurring.
-Hominins have not been around very long.

The fossils we do have are incomplete because they are either:
-A complete fossil of an incomplete specimen
   Part of the body was missing before fossilisation)
-An incomplete fossil of a complete specimen
   Part of the fossil was removed/destroyed after being fossilised.
Homo denisovans were around during the same time as Homo neanderthalensis and Homo sapiens. They may have evolved from Homo erectus.
It is believed that Neanderthals and humans may have interbred after humans migrated out of Africa due to the presence of Neanderthal DNA in non-African human DNA. It is also possible the H. denisovans interbred with one or both species. If we followed the typical definition of a species, this would make them all the same species. However, it is known that our current model is unable to explain some relationships (for example, how do you define a species of asexual organisms?)

Theories on the origin of modern humans
1. Out-of-Africa Hypothesis
This theory states that all humans (Homo sapiens) evolved from a discrete African population within the last 200,000 years and then migrated in relatively recent times throughout Africa, Europe, and Asia, displacing the more primitive H. erectus and H. ergaster populations. Also referred to as the replacement theory.
Mitochondrial DNA evidence – A comparison of mitochondrial DNA of native people around the world allows us to use a molecular clock to calculate the rate of mutation in mitochondrial DNA and therefore figure out where each group of native people came from and when. This traces it back to Africa 200,000 years ago. This theory is the one that is generally accepted.

2. Parallel evolution hypothesis
This theory states that the Homo sapiens line is older than 200,000 years, the theory is that Homo sapiens originated independently in different parts of the world from Homo erectus populations that had migrated from Africa around one million years ago, it was presumed that although there was some geographic isolation of populations there was some contact and hybridisation, and hence mixing of gene pools.
So basically the only other information I had was about how fossils are formed and why the fossil record isn't perfect.
« Last Edit: September 17, 2018, 09:48:07 am by PhoenixxFire »
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vox nihili

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Re: VCE Biology Question Thread
« Reply #10652 on: September 17, 2018, 10:48:50 am »
+3
That's a tricky one! A and B both sound very nice. Going by the wording, option A refers to "watery diarrhea" while the question asked for the best answer based on the "information alone". For this reason, maybe they say that B is the correct choice as it is talking about a symptom that is a direct result of the inability of water to diffuse out of the cell. After all, the best answer is the most correct and accurate based on the instructions. What a trap!!  :o

If anyone has a better idea, let us know! It's an interesting question.

The clincher is in the stem "chloride ions can't exit the cell". If chloride can't exit, it is retained in the cell. If it is retained in the cell, then more water in the cell and less in the external environment. Watery diarrhoea only happens if there is more water outside.

To make really watery diarrhoea you need to enhance the activity of CFTR, not eliminate it. This option was probably a nod to cholera, which does just that :)
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randomnobody69420

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Re: VCE Biology Question Thread
« Reply #10653 on: September 17, 2018, 05:55:40 pm »
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How do you use reading time effectively? I try to answer multiple choice questions in my head because it helps me finish faster but I don’t know if this is a good strategy or not

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Re: VCE Biology Question Thread
« Reply #10654 on: September 17, 2018, 05:58:41 pm »
+3
How do you use reading time effectively? I try to answer multiple choice questions in my head because it helps me finish faster but I don’t know if this is a good strategy or not
You can do that, I found that it's possible to do maybe the first 10 -15  MCQs in reading time.  However, I chose to read through the SAQs more thoroughly because that is where most of your marks will come, they are the harder questions and the standard deviation between scores will be greater for SAQ than MCQ.

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Re: VCE Biology Question Thread
« Reply #10655 on: September 17, 2018, 05:59:34 pm »
+4
I read through the short answer in the reading time and then start from the multi choice once writing time starts.

I think this helped because I could start to think about the short answer questions before I got to them - that way I didn’t turn a page, see a hard question and start panicking. It also gave me an idea about what was coming up which helped with timing.

Try a few different strategies during practice exams and figure out what works for you.
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PopcornTime

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Re: VCE Biology Question Thread
« Reply #10656 on: September 17, 2018, 10:50:59 pm »
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Cell membrane questions
- positive about most of the answers apart from last 2

Why is it that the smaller the molecule, the faster the rate of diffusion?
- small molecules travel through the phospholipid bilayer faster than larger molecules

Why is it that diffusion over shorter distances occurs at a faster rate than diffusion over longer distances?
- shorter distance means less energy expenditure
- thus, particle can move at a faster rate at lower energy expense compared to a larger molecule

Why is it that diffusion is faster through a larger surface area compared to a shorter surface area?
- not sure about this one

Any feedback would be good.

Why is it that the greater the difference in concentration gradient, the faster the rate of diffusion?
- not sure about this one




Owlbird83

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Re: VCE Biology Question Thread
« Reply #10657 on: September 18, 2018, 06:56:19 am »
+4


Why is it that diffusion is faster through a larger surface area compared to a shorter surface area?
- not sure about this one

The more surface area means there are more places for diffusion to be happening, so it is faster.
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Bri MT

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Re: VCE Biology Question Thread
« Reply #10658 on: September 18, 2018, 08:48:01 am »
+3

Why is it that the greater the difference in concentration gradient, the faster the rate of diffusion?
- not sure about this one

lets say I have 80 molecules on the left and 0 on the right with a semi-permeable membrane in between. The left is going to be super crowded compared to the right, and the molecules will keep bouncing away from each other. On the right, there is going to be heaps of room, and less for the molecules to bounce off from. This means that the molecules will go to the right much faster than they go to the left.

If I had 50 molecules on the left and 30 on the right, we'd still have them going to the right faster than they go to the left, but not by as much.

You can also think about it as "steepness" the higher the gradient, the more steep, the faster (net) change occurs
Hope this helps.
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PopcornTime

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Re: VCE Biology Question Thread
« Reply #10659 on: September 18, 2018, 01:28:53 pm »
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lets say I have 80 molecules on the left and 0 on the right with a semi-permeable membrane in between. The left is going to be super crowded compared to the right, and the molecules will keep bouncing away from each other. On the right, there is going to be heaps of room, and less for the molecules to bounce off from. This means that the molecules will go to the right much faster than they go to the left.

If I had 50 molecules on the left and 30 on the right, we'd still have them going to the right faster than they go to the left, but not by as much.

You can also think about it as "steepness" the higher the gradient, the more steep, the faster (net) change occurs
Hope this helps.

So, in the exam, I could say:
- higher number of particles in more concentrated area
- leading to a faster rate of diffusion due to increased collisions (movement) between particles

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Re: VCE Biology Question Thread
« Reply #10660 on: September 18, 2018, 01:32:04 pm »
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Why is it important for proteome to be diverse?
- proteins are involved in different cellular reactions
- greater diversity of proteins in cells means different reactions can occur to sustain and maintain life

Any feedback would be good.

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Re: VCE Biology Question Thread
« Reply #10661 on: September 18, 2018, 02:04:36 pm »
+2
So, in the exam, I could say:
- higher number of particles in more concentrated area
- leading to a faster rate of diffusion due to increased collisions (movement) between particles

The important thing is the difference between the two sides of the membrane, so that would need to be referred to in your response


Why is it important for proteome to be diverse?
- proteins are involved in different cellular reactions
- greater diversity of proteins in cells means different reactions can occur to sustain and maintain life

Any feedback would be good.

I feel like the term "specialisation"/"specificity" should come up for this
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galaxy21

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Re: VCE Biology Question Thread
« Reply #10662 on: September 18, 2018, 06:14:38 pm »
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Hi

Is someone able to tell me what the members of the following:
Hominoidea (hominoids)
Hominidae (hominid)
Homininae
Hominini

Also, is it Homininae or Hominini that is referred to as hominin, and what is the other referred to as?

And when asked for a timeline for biological evolution, should this be the changes seen as species evolve (e.g. species X evolves x trait at year x), or the time at which the change occurred? As for cultural evolution, what should I be focusing on as key changes?

Thanks! :D
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Re: VCE Biology Question Thread
« Reply #10663 on: September 18, 2018, 09:21:09 pm »
+5
Hi

Is someone able to tell me what the members of the following:
Hominoidea (hominoids)
Hominidae (hominid)
Homininae
Hominini

Also, is it Homininae or Hominini that is referred to as hominin, and what is the other referred to as?

And when asked for a timeline for biological evolution, should this be the changes seen as species evolve (e.g. species X evolves x trait at year x), or the time at which the change occurred? As for cultural evolution, what should I be focusing on as key changes?

Thanks! :D

The Homonoids are members of superfamily hominoidea, composed of apes which are mainly distinguished from other primates by their lack of a tail, tendancies towards erectness, 5 cusped dentition and a relatively large brain.

The Homonids are members of family hominidae, composed of the great apes and typically have a more complex social behaviour. This includes orangutans in addion to those of the hominines.

The subfamily Homininae (the hominines) a characterized by ground dwelling and a larger cerebral cortex. These include gorillas, chimps and ourselves.

The tribe hominini (the hominins) are primarily defined by bipedalism and the morphological characteristics that support such (more central foramen magnum, large heel bone, 'S'-shaped spine. There is no consensus on whether the subtribe panini (chimps) belongs in this tribe or in its own. I think for the purpose of our course we consider it not included. If not, perhaps someone can correct me otherwise.

I think with reguards to biological evolution, you want to be talking about the evolution of different life forms (ie. first simple single celled life, first eukaryotic life forms, first plants...)

Personally I don't think you should worry too much about cultural evolution. I think you should know what it is and understand a couple of examples, thats all.

Hopefully this helped!
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Re: VCE Biology Question Thread
« Reply #10664 on: September 18, 2018, 10:27:03 pm »
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What exam score should I be aiming for if I want to get 40+?