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March 29, 2024, 06:15:52 am

Author Topic: VCE Biology Question Thread  (Read 3570862 times)  Share 

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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #12960 on: September 19, 2020, 08:20:35 pm »
+4
Is the answer A

Coolgalbornin03Lo

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Re: VCE Biology Question Thread
« Reply #12961 on: September 19, 2020, 08:28:09 pm »
+4
Hi!! I got this mc question and I was wondering if this is assessable this year?
Two fossils had limb-like appendages and so scientists determined that they are analogous structures. As they are analogous structures, they must have shared similar
A. selection pressures
B. DNA sequences
C. RNA sequences
D. environments

I think it is because analogous and homologous are part of comparative anatomy which is still on the study design. And like chocolate pistachio said the answer is A :D
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homeworkisapotato

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Re: VCE Biology Question Thread
« Reply #12962 on: September 19, 2020, 08:54:32 pm »
0
Thank you so much guys! I misread the question and put B like an idiot smh. Thank you so much!
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #12963 on: September 19, 2020, 11:52:22 pm »
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For allele frequencies to remain constant in a population it is essential that
A mutations occur
B genetic drift occurs
C mating occurs at random in the population
D there is regular migration into

Would this be c

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Re: VCE Biology Question Thread
« Reply #12964 on: September 20, 2020, 12:05:02 am »
+6
For allele frequencies to remain constant in a population it is essential that
A mutations occur
B genetic drift occurs
C mating occurs at random in the population
D there is regular migration into

Would this be c

Yes, the answer should be C :)
Idk if you look at the Hardy-Weinberg Equilibrium in VCE, but it posits that allele frequencies will remain constant over generations if:
- no mutation occurs
- individuals mate randomly
- there is no gene flow
- there is an infinite population size
- there is no selection
We also know that mutations can introduce new alleles (thus altering allelic frequencies), genetic drift causes changes in allelic frequencies, and that migration can introduce new alleles (similar to a mutation in that this will alter allelic frequencies). Thus, the answer should be C: mating randomly helps ensure that allele frequencies remain constant :)
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Re: VCE Biology Question Thread
« Reply #12965 on: September 20, 2020, 09:37:07 am »
+3


Exactly! 
In the previous study design HWE was in but not anymore.

Beyond this: HWE tells us that allele frequency follows these rules where p and q are the only alleles at one locus:
1 = p + q
1 = (p+q)^2 = pp + 2pq + qq

With assortative mating (reproduction more likely between similar individuals) you get more homozygotes (pp and qq) and less heterozygotes (pq) than you'd expect and the opposite for dissortative mating.

Again you don't need to know this,  just there if you're interested :)

Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #12966 on: September 20, 2020, 06:29:33 pm »
0
Bats and birds are flying vertebrates -they share similar traits. Do these similarities reflect convergent evolution or common ancestry?

Is it convergent evolution

Owlbird83

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Re: VCE Biology Question Thread
« Reply #12967 on: September 20, 2020, 07:21:48 pm »
+4
Bats and birds are flying vertebrates -they share similar traits. Do these similarities reflect convergent evolution or common ancestry?

Is it convergent evolution
Yeah, you are right. They evolved wings that are very different independently.
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #12968 on: September 20, 2020, 07:32:22 pm »
0
thanks

i'm not sure how to answer this question
why do you think the hawk, although a descendent of the most recent common ancestor, is not included in the dinosaur group

 

Coolgalbornin03Lo

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Re: VCE Biology Question Thread
« Reply #12969 on: September 20, 2020, 08:04:33 pm »
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I’ve always understood B cells are for extra cellular pathogens and T cells are for intracellular pathogens is this incorrect?

In the solutions my teacher made for a question asking how b and T cells work together an explanation is B cells are for extracellular environment whereas T cells are for intracellular environment.

Also so Naive T cells exist? Or are they cytotoxic T cells? I always thought it was T cells which proliferate and differentiate into T memory cells and Cytotoxic T cells but now I’m not quite sure :(
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-Lilac-

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Re: VCE Biology Question Thread
« Reply #12970 on: September 20, 2020, 08:27:00 pm »
+3
I’ve always understood B cells are for extra cellular pathogens and T cells are for intracellular pathogens is this incorrect?

In the solutions my teacher made for a question asking how b and T cells work together an explanation is B cells are for extracellular environment whereas T cells are for intracellular environment.

CD8 T cells (cytotoxic T cells) can kill infected cells, so they do play an important role in the response against intracellular pathogens. However, B cells do as well as they can produce neutralizing antibodies that prevent the virus from being able to infect a cell. Think about vaccines, very few induce a T cell response but rather are aiming to produce neutralizing antibodies against the virus/bacteria.     

Helper T cells are also very important in intracellular and extracellular pathogen responses. There are subtypes of Th cells that direct intracellular or extracellular responses (don't worry about this but I am just showing you how they have roles in both types of infections). For example, helper T cells are important for activating B cells to produce antibodies in extracellular (and intracellular) infections.

So overall, I see helper T cells and B cells as being involved in both types of infections. However, cytotoxic T cells are not very useful in extracellular pathogen response. I would discuss this further with your teacher to maybe understand what they meant by B cells = extracellular and T cells = intracellular.

It could have been an oversimplification (or maybe VCE knowledge-wise it is ok?- someone here may be able to comment on that I am not very up to date with the study design).

EDIT: As SmartWorker has pointed out what your teacher says seems to be consistent with VCE knowledge. I may have gone into a bit too much detail, so sorry & just ignore if it confuses you!

Also so Naive T cells exist? Or are they cytotoxic T cells? I always thought it was T cells which proliferate and differentiate into T memory cells and Cytotoxic T cells but now I’m not quite sure :(

Naive T cells are T cells that have never seen their antigen before and live in the lymph nodes/secondary lymph tissue. They can be CD8 or CD4 cells. When they are presented their antigen they will proliferate into effector T cells (either CD8 or CD4) or memory cells and be allowed to travel to the site of infection.
« Last Edit: September 20, 2020, 09:30:08 pm by -Lilac- »
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #12971 on: September 20, 2020, 08:47:08 pm »
0


Initially studied as an agent of disease in plants, it is small enough to pass through a porcelain filter. Attempts to culture it in a nutrient-rich medium failed, and it could not be seen with a light microscope. It was also discovered that this agent of disease could only be cultured in living cells; the cells then produced copies of this agent.

You identified and classified this as an agent of disease- virus
Which of the following statements best support you answer
A the agent has organelles
B it is an agent of disease in plants
C the agent has nucleic acid
D the agent is not a cell it does not have cytoplasm
E the agent is small it cannot be seen with the light microscope
F the agent requires living host cells to reproduce

Which would be the correct answers  Why not b or c or e

SmartWorker

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Re: VCE Biology Question Thread
« Reply #12972 on: September 20, 2020, 09:10:30 pm »
+6

Initially studied as an agent of disease in plants, it is small enough to pass through a porcelain filter. Attempts to culture it in a nutrient-rich medium failed, and it could not be seen with a light microscope. It was also discovered that this agent of disease could only be cultured in living cells; the cells then produced copies of this agent.

You identified and classified this as an agent of disease- virus
Which of the following statements best support you answer
A the agent has organelles
B it is an agent of disease in plants
C the agent has nucleic acid
D the agent is not a cell it does not have cytoplasm
E the agent is small it cannot be seen with the light microscope
F the agent requires living host cells to reproduce

Which would be the correct answers  Why not b or c or e

It is asking you for the best answer not all correct answers.
So, .: D and F is correct.

A is wrong: viruses do not have organelles
B is wrong: but already mentioned in stem. For example if you have a bacteria, fungi and virus all 3 may be agents of disease in plants:  you cannot differentiate using this.
C is wrong: bacteria have nucleic acids, so doesn't narrow it down to viruses.
D: correct. Viruses need a cytoplasm to replicate---> .: there are obligate intracellular pathogens
E: Light microscopes are limited. hence other pathogens other than viruses cannot be see using Light microscope.
F is correct


-snip-

For VCE:
T cells ---> involved in destroying infected cells or 'presented' antigens i.e: when cells infected they present pathogenic antigens. (I think intracellular environment in the question relates to inside cells)
B cells --> involved directly with free-moving pathogens or 'raw' antigens (I think extracellular environment refers to outside cells)
« Last Edit: September 20, 2020, 09:19:22 pm by SmartWorker »
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Chocolatepistachio

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Re: VCE Biology Question Thread
« Reply #12973 on: September 20, 2020, 09:51:41 pm »
0
Thanks!

What does prokaryotes that live in a colonial form mean 


homeworkisapotato

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Re: VCE Biology Question Thread
« Reply #12974 on: September 21, 2020, 07:54:26 am »
+5
Thanks!

What does prokaryotes that live in a colonial form mean
They live in big groups together clustered in one spot. For example, on an agar plate you would see bacteria growing in fuzzy little circles, and those circles you would refer to as colonies.
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