VCE Biology Question Thread

[Owlbird83]

I don’t understand what blunt or sticky ends are......could someone please explain?

When restriction enzymes cut DNA they either cut straight through, or they cut in slightly different places on either strand of DNA leading to unpaired bases. Much easier to explain with a diagram:


Hope that's clear. Sticky ends are much more useful because if you want to join DNA you can cut both DNA strands that you want to join with the same restriction enzyme (so they are cut at the same sequence and will have complementary bases exposed), and therefore are more likely to join together because the exposed bases form hydrogen bonds. In comparison, blunt ends will just sit there because all the bases are already bonded and there aren't exposed bases.

[Chocolatepistachio]

In a symbiotic relationship are species in direct contact with each other or are they just in close contact because I thought it was just close contact not directly
But in a question it said symbiosis refers to the ecological relationship between different species that live in direct contact with each other

[1729]

In a symbiotic relationship are species in direct contact with each other or are they just in close contact because I thought it was just close contact not directly
But in a question it said symbiosis refers to the ecological relationship between different species that live in direct contact with each other

Symbiotic relationships refer into the context of how species directly interact with one another; symbiotic relationships are just the dynamic that 2 organisms have with each other. The three types of symbiotic relationships are mutualism (+/+), commensalism (+/0), and parasitism (+/-). There are direct contacts like a parasite clinging unto a dog to feed off its nutrients (parasitism) and is an example of direct contact. So symbiotic relationships are about direct contact if im understanding your question correctly. Indirect contact can result in harm in another species (ie herbivores eating leaves and nutrients off a tree and species who live in trees suffer as a result of it) but im fairly certain that's not a "relationship" as they do not directly contact with each other. Please correct me if I'm wrong. And if you need any further clarification don't hesitate to ask! 

I should probably add. Indirect effects in ecology can be like Species 3 starts to eat more of one food source, which decreases the Species 1 and Species 2 as they were also dependent on that food source and can lead to competition over food. I'm pretty sure for Species 3 they would grow in population as they now have another food source that they can eat;; but this is just a off-the-top-of-my-head exampl; if anyone can tell me what they think that would be great,

But anyway stuff like this where it's not direct contact is not a relationship; only species 1 and 2 could have a competition relationship and I'm not too sure if that's classified as a symbiotic relationship; but it would have to be researched more

Again, please correct me if I am wrong.

Anyways, in the end it doesn't really matter as long as you understand what each interaction consists of +/-/0 wise.

[Bri MT]

In a symbiotic relationship are species in direct contact with each other or are they just in close contact because I thought it was just close contact not directly
But in a question it said symbiosis refers to the ecological relationship between different species that live in direct contact with each other

Symbiotic relationships refer into the context of how species directly interact with one another; symbiotic relationships are just the dynamic that 2 organisms have with each other. The three types of symbiotic relationships are mutualism (+/+), commensalism (+/0), and parasitism (+/-). There are direct contacts like a parasite clinging unto a dog to feed off its nutrients (parasitism) and is an example of direct contact. So symbiotic relationships are about direct contact if im understanding your question correctly. Indirect contact can result in harm in another species (ie herbivores eating leaves and nutrients off a tree and species who live in trees suffer as a result of it) but im fairly certain that's not a "relationship" as they do not directly contact with each other. Please correct me if I'm wrong. And if you need any further clarification don't hesitate to ask! 

There are  multiple different definitions of symbiosis that go around but direct contact should be considered a subset of close contact (i.e. direct contact is a type of close contact).

There are also more types of symbiosis than the "big three" but you won't be expected to know them.

[Chocolatepistachio]

would this be a good diagram showing cytokinesis in a plant cell and an animal cell

[Owlbird83]

would this be a good diagram showing cytokinesis in a plant cell and an animal cell

It would probably be marked correct (?), but some suggestions:
-if you are going to add the extra details like spindle fibres you should label them, but I don't think it's necessary to include them because it specifies 'simple'.
-The cell plate looks like a circle? Try and be neater to show it's a cell wall
-the animal cell should end up with 2 equally sized cells
-animal cell should only have 1 line around it (not 2)
-plant cell should have 2 lines around it (1 reckon one would also be accepted, but 3 is too many)

I would probably keep my diagram a bit more simple:

Spoiler

Edit: My labelling lines should be touching the things I've labelled, (you have done your labelling lines well)

[Chocolatepistachio]

Thanks. also for this fill in the blank question

Some viruses have ——- which can often change by mutation

Is it spikes

[GodNifty]

Thanks. also for this fill in the blank question

Some viruses have ——- which can often change by mutation

Is it spikes

Is it ribonucleic acid? Since I believe it mutates more frequently than DNA.

What are spikes? I have not heard of this before.

[-Lilac-]

Some viruses have ——- which can often change by mutation

Is it spikes

This question could technically have a number of answers. RNA or DNA being one of them and thus also any viral proteins (spike proteins).

I’m not 100% so maybe someone else can make it clearer (I’m leaning towards RNA).

Is it ribonucleic acid? Since I believe it mutates more frequently than DNA.

What are spikes? I have not heard of this before.

Spike proteins typically refer to viral proteins/glycoproteins that stick out from the viral envelope and therefore are ‘seen’ by the host immune system. They are also often critical in the attachment and entry of viruses.  As a result they are often talked about in the context of potential vaccine targets.

RNA viruses also tend to have higher mutation rates due to the RNA pol they use.

[Chocolatepistachio]

In ruminants (a relationship between cows and fungi) what is the advantage for the cow and what is the advantage for the fungus

[1729]

In ruminants (a relationship between cows and fungi) what is the advantage for the cow and what is the advantage for the fungus

If I’m understanding that question you are asking. The cows would receive the benefit of breaking down the cellulose they eat and the microbes would be receiving food. The fungus would break down the cellulose for the cow, allowing both the cow and the microbe to get the nutrients.

[Bri MT]

In ruminants (a relationship between cows and fungi) what is the advantage for the cow and what is the advantage for the fungus

A ruminant is a particular type of mammal (e.g. cows, sheep) & I have not seen that term used to describe a symbiotic relationship before

[1729]

A ruminant is a particular type of mammal (e.g. cows, sheep) & I have not seen that term used to describe a symbiotic relationship before

I'm pretty sure the term ruminant in the question is used to desrcibe the animal itself, not the relationship. However, I don't know if Chocolatepistachio worded the question exactly how it was given to him. In the original question it asked.

In ruminants (a relationship between cows and fungi) what is the advantage for the cow and what is the advantage for the fungus

The wording did seem a bit like ruminant described the relationship, so if thats how it was worded then the question is wrong. But if it is worded like how Bri MT suggested.

A ruminant is a particular type of mammal (e.g. cows, sheep) & I have not seen that term used to describe a symbiotic relationship before

Then the question is talking about the animal. Either way, a ruminant is a type of animal and not a type of relationship, though I believe all ruminants make use of this relationship.

[SmartWorker]

For this MC why can't it be B as well, answer is D (I get why but why does B not work?)

The number of cancer cells within the tissue is rapidly increasing. This increase in the number of cancer cells can be explained by
A. increased caspase function within each of the cancer cells.
B. decreased rate of apoptosis in the surrounding normal cells.
C. reduction in size of the nuclei of cancer cells compared to those of normal cells.
D. impaired signalling from death receptors located on the membrane of the cancer cells.

[Owlbird83]

For this MC why can't it be B as well, answer is D (I get why but why does B not work?)

The number of cancer cells within the tissue is rapidly increasing. This increase in the number of cancer cells can be explained by
A. increased caspase function within each of the cancer cells.
B. decreased rate of apoptosis in the surrounding normal cells.
C. reduction in size of the nuclei of cancer cells compared to those of normal cells.
D. impaired signalling from death receptors located on the membrane of the cancer cells.

The question is asking why no. of cancer cells is increasing, B doesn't really have anything to do with the growth of the cancer cells. It describes something happening to normal cells, so a bit unrelated to what the question is asking.