HSC Biology Question Thread

[Mounica]

Hey Guys,
Does anyone know what part of the Communication syllabus this question is referring to:
"Compare mechanisms in the human body for detection and perception of a range
of frequencies in visual and auditory communication"

[Potatohater]

Hey Guys,
Does anyone know what part of the Communication syllabus this question is referring to:
"Compare mechanisms in the human body for detection and perception of a range
of frequencies in visual and auditory communication"

It might be one of those tricky questions that ask you to refer to multiple dot points such as
- identify the limited range of wavelengths of the electro magnetic spectrum detected by humans etc.
- explain why sound is useful and versatile form of communication
- 2ndary sources to outline frequencies detected by humans
Basically this question wants you to have a good knowledge of lots of dot points and link them together

[julia_warren13]

Even if the question does not specifically ask, is it possible to use a table when answering a 'compare' or 'contrast' question? (And still get the full marks!!) Thanks

[Potatohater]

Even if the question does not specifically ask, is it possible to use a table when answering a 'compare' or 'contrast' question? (And still get the full marks!!) Thanks

For sure! I do it all the time internally and I'm certain this counts externally too - I reckon it's the best method

[julia_warren13]

For sure! I do it all the time internally and I'm certain this counts externally too - I reckon it's the best method

Okay thank you! I also used tables for my trial but just wasn't sure if external markers would accept it

[inescelic]

sounds pretty good but can't give a mark without a guideline

thanks unfortunately i don't have it as it came from my friend's trial but at least it sounds pretty good haha

[inescelic]

Hi could someone please help with this question? I don't really understand how to distinguish homeostasis and enantiostasis, and in which cases one is used over the other. The sample answer didn't really help me either

HSC 2009
Q26: Describe how processes such as enantiostasis and homeostasis are used to maintain metabolic functions when salt concentration varies in plants living in estuarine environments.

Sample answer:
Homeostasis involves maintaining a constant internal environment to maintain metabolic functions. This is difficult if there are large variations in salt concentration. In organisms that use enantiostasis, other physical or chemical conditions are varied to compensate for the variations in salt concentration so the metabolic functions are maintained.

[Potatohater]

Hi could someone please help with this question? I don't really understand how to distinguish homeostasis and enantiostasis, and in which cases one is used over the other. The sample answer didn't really help me either

HSC 2009
Q26: Describe how processes such as enantiostasis and homeostasis are used to maintain metabolic functions when salt concentration varies in plants living in estuarine environments.

Sample answer:
Homeostasis involves maintaining a constant internal environment to maintain metabolic functions. This is difficult if there are large variations in salt concentration. In organisms that use enantiostasis, other physical or chemical conditions are varied to compensate for the variations in salt concentration so the metabolic functions are maintained.

Homeostasis: maintainance of a constant internal environment
Enantiostasis: maintainance of functionality in a changing environment
Enantiostasis is how organisms that live in saline conditions deal with the fluctuations in their environment. They can do this by being either:
Osmoconformers: able to maintain metabolic function with a changing internal environment - eg. A starfish matches it's body fluids to the external environment so it doesn't gain or lose too much water via osmosis
Osmoregulators: keep internal salt levels within a narrow range - eg. Mangroves have leaves where they store salt and drop off, and pnumetaphores which try and stop as much salt coming in as possible, this tries to minimise salt in the organism
So basically the sample answer is trying to say that in saline environments (such as estuaries where the salt levels are constantly fluctuating) it is incredibly hard to maintain homeostasis due to osmosis. Therefore these organisms change their behaviours and/or internal environment so they can continue to function.
If you still don't understand let me know and I'll attempt to clarify 
 

[inescelic]

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.

Environment and genotype both affect the phenotype of individuals. Genotype refers to the combination of alleles one inherits from their parents for a certain characteristic. According to Mendel's law of segregation, alleles are separated in meiosis, forming gametes with half of the genetic information of a diploid cell. However, this number is restored in fertilisation, as for each characteristic or gene, a zygote will receive one allele form each parent. Whether the alleles are dominant or recessive determines the phenotype of the offspring. For example, in Mendel's experiment with pea plants, if offspring inherited one dominant allele for tall height and a recessive allele for short height, they would present a tall phenotype.
However, genotype does not always confirm the phenotype of an individual. Environment also has an impact on phenotype, and can change how the characteristic is presented. For example, if seedlings are placed in a covered box, their environment is changed as they do not have sunlight available. Although a seedling may have the genotype to be tall and green, the lack of sunlight limits photosynthesis, thus the plant is not able to grow tall and be green in appearance.
Therefore, though genes are inherited from parents to offspring, the presented phenotype can also change due to environmental factors.

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

Understanding hearing mechanisms has led us to develop technologies such as hearing aids and the cochlear implant.
Sound waves are first channeled into the ear by the pinna. Then, as sound hits the tympanic membrane, sound waves are converted to mechanical energy. Then, the ear ossicles serve to transmit and and amplify this energy to the cochlea through the oval window. The mechanical energy travels through the fluid in the cochlea, stimulating hair cells in the Organ of Corti, which release chemicals as they are stimulated and bent, ultimately releasing an electrochemical signal which is sent as a nerve impulse to the brain through the auditory nerve.
Our understanding of the outer and middle ear, including the role of the tympanic membrane and ear ossicles has led us to develop the hearing aid, which amplifies sound if these areas are broken or not working properly. The microphone firstly picks up sounds, which is then amplified and this amplified sound is then channeled into the ear by an earpiece. As a result, the person is able to hear sounds at a louder volume.
Also, our understanding of the cochlea and its role has lead to the development of the cochlear implant if someone has inner ear damage to the cochlea or hair cells. Hair cells, in the Organ of Corti are important as they stimulate an electrochemical signal, initiating a nerve impulse. If any part of the cochlea is not working, the cochlear implant is used to stimulate the auditory nerve so the brain can receive the message. It works by a sound processor firstly capturing sound through a microphone. Then, the sound processor converts the sound information into digital information. This digital information is sent over a transmitter antenna to the internal implant receiver through radio waves. The digital receiver then converts the digital sound information into electronic signals and sends them to an electrode array. The electrode array in the cochlea then delivers direct stimulation to the auditory nerve fibres, where a signal is sent to the brain to be interpreted.
Therefore, through our understanding of hearing mechanisms and their role, we have developed technologies to assist people with hearing failures.

[inescelic]

Homeostasis: maintainance of a constant internal environment
Enantiostasis: maintainance of functionality in a changing environment
Enantiostasis is how organisms that live in saline conditions deal with the fluctuations in their environment. They can do this by being either:
Osmoconformers: able to maintain metabolic function with a changing internal environment - eg. A starfish matches it's body fluids to the external environment so it doesn't gain or lose too much water via osmosis
Osmoregulators: keep internal salt levels within a narrow range - eg. Mangroves have leaves where they store salt and drop off, and pnumetaphores which try and stop as much salt coming in as possible, this tries to minimise salt in the organism
So basically the sample answer is trying to say that in saline environments (such as estuaries where the salt levels are constantly fluctuating) it is incredibly hard to maintain homeostasis due to osmosis. Therefore these organisms change their behaviours and/or internal environment so they can continue to function.
If you still don't understand let me know and I'll attempt to clarify 
 

Thank you! It kind of makes sense So because it is too hard for organisms to maintain homeostasis in fluctuating environments they must change their metabolic functions? But what I don't understand is how these behaviours are not also considered processes to achieve homeostasis(e.g. how is it different to homeostatic salt regulation of aldosterone)? Also, how does osmosis interfere with homeostasis?

[Potatohater]

Thank you! It kind of makes sense So because it is too hard for organisms to maintain homeostasis in fluctuating environments they must change their metabolic functions? But what I don't understand is how these behaviours are not also considered processes to achieve homeostasis(e.g. how is it different to homeostatic salt regulation of aldosterone)? Also, how does osmosis interfere with homeostasis?

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

[Potatohater]

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

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

[pikachu975]

Sorry what exactly is the clonal selection theory and clonal expansion? Don't think I've ever come across these terms before. My knowledge of Burnet is also kinda iffy - didn't he identify MCH I or II molecules as being present on cells that identified them as being part of ones own body, and so did not trigger the immune response?

Clonal expansion is when B and T cells divide rapidly so that they can specialise after. The theory in detail explains how lymphocytes (B and T cells) interact in the immune response.

Hey Guys,
Does anyone know what part of the Communication syllabus this question is referring to:
"Compare mechanisms in the human body for detection and perception of a range
of frequencies in visual and auditory communication"

Basically talk about the process of sight and hearing as well as listing the ranges of each:

Sight: 700-400 nm
Sound: 2000-20000 Hz with most sensitivity at 2000-4000 Hz due to speech

[pikachu975]

Homeostasis: maintainance of a constant internal environment
Enantiostasis: maintainance of functionality in a changing environment
Enantiostasis is how organisms that live in saline conditions deal with the fluctuations in their environment. They can do this by being either:
Osmoconformers: able to maintain metabolic function with a changing internal environment - eg. A starfish matches it's body fluids to the external environment so it doesn't gain or lose too much water via osmosis
Osmoregulators: keep internal salt levels within a narrow range - eg. Mangroves have leaves where they store salt and drop off, and pnumetaphores which try and stop as much salt coming in as possible, this tries to minimise salt in the organism
So basically the sample answer is trying to say that in saline environments (such as estuaries where the salt levels are constantly fluctuating) it is incredibly hard to maintain homeostasis due to osmosis. Therefore these organisms change their behaviours and/or internal environment so they can continue to function.
If you still don't understand let me know and I'll attempt to clarify 
 

How is homeostasis used to maintain metabolic function though? As asked in the question. I was having trouble with this one as well

[inescelic]

How is homeostasis used to maintain metabolic function though? As asked in the question. I was having trouble with this one as well

From what I now understand, I think homeostasis is used to create a stable internal environment FOR metabolic function (think of how if pH or temp are out of optimum range, metabolism doesn't function effectively). Whereas when it is difficult for the organism to do this in a fluctuating environment, enantiostasis is used to maintain metabolic functions by which the organism changes with the environment. (Blue crabs change the pH of their blood in brackish water to increase the ability to bind with oxygen)