HSC Biology Question Thread

[inescelic]

In enantiostasis, the organisms don't change their metabolic functions, they change their internal environment. So in the case of the starfish the starfish will make its body more or less saline to match the external environment. This is different to homeostasis because in homeostasis the internal environment is kept constant, so in humans for example, the salt levels in our bodies stay more or less the same regardless of our environment.
These processes are not considered as achieving homeostasis because the internal environment does change, where as in homeostasis it does not. Throughout this process the metabolic functions remain the same but the internal environment does not.

What I meant abuout osmosis impacting homeostasis:
In terms of estuarine environments osmosis can cause water to enter or leave an aquatic organism if there were no processes to regulate this. As you know, fresh water fish produce heaps of dilute urine to maintain their water levels, as water moves into the fish because it is more concentrated than the external environment, and salt water fish produce small amounts of concentrated urine to prevent water going out because the external environment is more saline than the fish. However, organisms in estuaries, where the water is brackish and can fluctuate in salt levels, can't change their function to deal with the salinity, so they change the internal environment to match the situation so that they can continue to operate

Ok so when it is difficult for the organism to maintain homeostasis in a fluctuating environment, enantiostasis is used to maintain metabolic functions by which the organism changes with the environment? So that is where osmoconformers come in as they vary along with the environment. But how do osmoregulators vary along with the environment since they are keeping salt in a narrow range?

[inescelic]

Is there a marking criteria? I do have acsess to a bunch of sample answers for these questions which I can mark against (and so far your answers are looking pretty good) but if there's a marking scheme that would make the assignment of a mark more accurate

Yep here you go

[inescelic]

Can someone please mark this?

I was a little unsure as to whether I took a valid approach to this question Also I'm not sure if competition for resources would be an acceptable point.
Much appreciated

Biology has allowed us to validate theories of evolution, supporting the significance of isolation and environmental pressures in the gradual change of species over time. Our increased use of biogeography and palaeontology practice has ultimately affirmed Darwin’s theory of evolution.

Darwin described evolution as the gradual change of species over many generations. Many species have evolved due to the separation of land forms as shown through biogeography. 85 million years ago, New Zealand separated from New Zealand. As New Zealand drifted east and subsided, its land was mostly under sea water. As individuals in a species on New Zealand may have become isolated, from other individuals of the same species on Australia, they have become subject to different environmental pressures on each island. This means that individuals on New Zealand who were more favourable to marine environments, as New Zealand was then mostly under water, such as those who had a streamline body or or fins were able to survive and reproduce. These traits were then passed to offspring, and over many generations, a new species was eventually formed. This is validated by palaeontology, as the source says “most fossils were marine at this time”.

Furthermore, the source also shows that new land was created by volcanoes 22 million years ago. This acted as an environmental pressure on species, and those individual with traits more favourable for a volcano environment also survived, passing these traits to their offspring. Over many generations, Darwin’s theory states new species would be formed, and is validated by palaeontology as “many unique species of birds appeared in the fossil record”, affirming the evolution of species. Thus, palaeontology techniques, such as using carbon dating have been very important in validating the evolution of New Zealand.

Also, 700 years ago, the island became completely devoid of mammals. Considering that there were many birds earlier, that “occupied niches that were usually occupied by mammals”, this suggests that the birds competed for resources with the mammals, ultimately being successful. Thus, this information supports how competition for resources can affect the path of evolution.

Therefore, biological practices such as biogeography and palaeontology have been important in validating ideas about the role of isolation, environmental pressures and competition for resources in evolution.

Question and marking criteria are attached

[angelahchan]

Hi,
does anyone know what "hybridisation within a species" mean? At first I thought it was something to do with transgenic organisms, but is it more about cross breeding within a species (e.g. different dog breeds)

[Natasha.97]

Hi,
does anyone know what "hybridisation within a species" mean? At first I thought it was something to do with transgenic organisms, but is it more about cross breeding within a species (e.g. different dog breeds)

Hi!

- Hybridisation is defined as the cross - breeding of two genetically non-identical individuals within the same species
       Example (as you've mentioned): Labradoodle (Labrador/Poodle)
- Transgenic organisms have had genes from other organisms artificially inserted into them
       Example: Salmon (bGH - Bovine Growth Hormone inserted, which results in larger + faster growing fish) and Potatoes (Lectin inserted: interferes with insect digestion to protect against insects, which helps to maintain and increase food production)

Hope this helps

[Potatohater]

Ok so when it is difficult for the organism to maintain homeostasis in a fluctuating environment, enantiostasis is used to maintain metabolic functions by which the organism changes with the environment? So that is where osmoconformers come in as they vary along with the environment. But how do osmoregulators vary along with the environment since they are keeping salt in a narrow range?

Ok from my understanding osmoregulators either have functions to keep salt in a narrow range or the avoid the changes eg. Some crabs bury themselves in the mud when the tides change to avoid salinity changes.

[pikachu975]

Hi,
does anyone know what "hybridisation within a species" mean? At first I thought it was something to do with transgenic organisms, but is it more about cross breeding within a species (e.g. different dog breeds)

Hybridisation is interbreeding organisms of the same species.

Labradoodle (Labrador x Poodle):
- Doesn't shed much (Poodle)
- Doesn't have much body odour (Poodle)
- Doesn't need to be washed much (Poodle)
- Easy to train as guide dogs (Labrador)
- Friendly (Labrador)

So they're mainly good for asthma sufferers, and can also be used in jobs as they're easy to train.

If it says INBREEDING like CSSA it means dogs of the same organism, e.g. labrador x labrador. Easily confused with INTERbreeding.

[Arvacado]

Hiii!! When they ask 'outline how different antibiotics work' do you talk about the drug antibiotic and the antibiotic activated by B-cells?

[Potatohater]

Hiii!! When they ask 'outline how different antibiotics work' do you talk about the drug antibiotic and the antibiotic activated by B-cells?

Antibiotics kill bacteria
Antibodies are produced by B plasma cells
They are totally different things. So when they ask about antibiotics you talk about the drugs
When they ask about antibodies  you talk about the 3rd line of defence

[pikachu975]

Hiii!! When they ask 'outline how different antibiotics work' do you talk about the drug antibiotic and the antibiotic activated by B-cells?

I would speak about narrow and broad-range antibiotics and how narrow range only kill specific bacteria while broad-range kill numerous and are administered for a general bacterial illness.

I doubt this would be asked in HSC though.

[Aaron12038488]

just wondering in general for hsc science subjects if flashcards help in memorising and consolidating yr knowledge thx. Might try it out.

[pikachu975]

just wondering in general for hsc science subjects if flashcards help in memorising and consolidating yr knowledge thx. Might try it out.

Different for everyone but yes it can be useful

[Potatohater]

Could someone please mark these?
Both are from the 2009 HSC

Question 27 (8 marks)
Most offspring resemble their parents in a number of characteristics, but there are often some characteristics in the offspring that are unexpected.
Explain, using examples, how genetics and the environment can affect the phenotype of individuals.

Q28 Communication
 e) Explain how an understanding of hearing mechanisms has been used to develop 7 technologies to overcome hearing difficulties.(7 marks)

Ok so I'm just getting sound to marking your responses based off criteria and sample answers.
DISCLAIMER: I am by no means a marking expert since I am also doing th HSC this year, and when I mark myself I tend to mark myself a mark or two harsher than what I actually think because of this, and I guess that pushes me a little
Ok so for 27, I think I would give it a 7. All the info was there, I just felt like its coherence could be improved slightly, but this isn't a major deal, since as previously stated, I try and mark harsher just in case.
For 28 e, I'm giving that a 7 too since it followed a very logical procedure and demonstrated a thourough understanding of how these technologies work to overcome hearing difficulties.
Good job!

Can someone please mark this?
I was a little unsure as to whether I took a valid approach to this question Also I'm not sure if competition for resources would be an acceptable point.
Much appreciated
Question and marking criteria are attached

For this question I think I'll have to give you a 5. Unfortunatley the top band requires you to talk about theories where as you only discussed Darwins theory of gradual evolution. To access the 6/7 marks you would have to also talk about punctuated equilibrium. This is where the birds come in, since many fossils appeared all at once. I feel you could also make more explicit links between the biological evidence and the theories, but maybe that's just me. Other than that I think you have a sound understanding and explained in a clear manner.

[inescelic]

Ok so I'm just getting sound to marking your responses based off criteria and sample answers.
DISCLAIMER: I am by no means a marking expert since I am also doing th HSC this year, and when I mark myself I tend to mark myself a mark or two harsher than what I actually think because of this, and I guess that pushes me a little
Ok so for 27, I think I would give it a 7. All the info was there, I just felt like its coherence could be improved slightly, but this isn't a major deal, since as previously stated, I try and mark harsher just in case.
For 28 e, I'm giving that a 7 too since it followed a very logical procedure and demonstrated a thourough understanding of how these technologies work to overcome hearing difficulties.
Good job!

For this question I think I'll have to give you a 5. Unfortunatley the top band requires you to talk about theories where as you only discussed Darwins theory of gradual evolution. To access the 6/7 marks you would have to also talk about punctuated equilibrium. This is where the birds come in, since many fossils appeared all at once. I feel you could also make more explicit links between the biological evidence and the theories, but maybe that's just me. Other than that I think you have a sound understanding and explained in a clear manner.

No that's good, thank you! I definitely understand what you meant with the different theories of evolution, makes sense Also competition for resources and its role in evolution can be a bit confusing, but do you think what I have said about it in the above response makes sense?
Bio seriously stress me out because I feel like I never know if what I'm writing is going to match the marking criteria. Some questions in bio are open to many different interpretations and that makes it so stressful:( Any tips?

[Thebarman]

How much detail do we need to know about the human larynx and its structures?
Do we need to know in detail the glottis?