HSC Biology Marathon 2015 (4 Viewers)

[Fiction]

The theory of evolution is supported by Paleontology, which is the study of fossils. A fossil record shows the sequence of the earliest of life to today's present organisms, this supports the theory of evolution and suggests that there is evidence of change in organisms. An example is horses:

- Early horses were small animals, with four toes and a small check span.
- Modern horses are large horses, with one toe and a large check span.

The fossil record of horses shows that horses evolved from being small, having more than one toe and a small check span to horses that are large, have one toe and a large check span.


I don't know the answer to why evolution is not supported by paleontological evidence, I haven't come across such a question before.

Oh I made up that question haha
I was thinking along the lines of the differences between gradualism and the punctuated equilibrium model.

 

[BlueGas]

Oh I made up that question haha
I was thinking along the lines of the differences between gradualism and the punctuated equilibrium model.

Yeah maybe Gradualism may not support the theory of evolution. Darwin proposed that populations change slowly and gradually (gradualism) over time. However, this doesn't support the theory of evolution because the environment doesn't continually change, and this is proved by the fossil record of organisms such as the dinosaurs, they were present in large numbers, then as the environment changed, most dinosaurs became extinct.

 

[DepressedPenguino]

Why do freshwater fish actively absorb salts if they gain a lot of water by osmosis? Wouldn't salt absorption attract even more water, causing it to burst?

Feshwater fish's gills are impermeable to water

 

[DepressedPenguino]

Do T cells or T helper cells become memory T cells? I am not sure

 

[astab]

Do T cells or T helper cells become memory T cells? I am not sure

T-cells - more specifically, cytotoxic (killer) T-cells become memory T-cells after they've triggered specific immune responses against an antigen. Helper T-cells act more efficiently in the event of subsequent exposures to the same antigen.

 

[astab]

Feshwater fish's gills are impermeable to water

I thought that freshwater fish gain water by osmosis? Since their surrounding environments are highly diluted, water rushes into the fish to create an isotonic balance of solutes in and outside the fish. But why does it absorb salts if it wants to get rid of water?

 

[DepressedPenguino]

T-cells - more specifically, cytotoxic (killer) T-cells become memory T-cells after they've triggered specific immune responses against an antigen. Helper T-cells act more efficiently in the event of subsequent exposures to the same antigen.

lol i didnt know cytotoxic T cells can become memory T cells. hmm pretty interesting

 

[BlueGas]

Question: In humans, brown eyes (B) are dominant over blue eyes (b). A man marries a blue eyed woman, they have two children, a brown eyed boy and a blue eyed girl. What are the genotypes of the parents and children?

 

[Fiction]

Question: In humans, brown eyes (B) are dominant over blue eyes (b). A man marries a blue eyed woman, they have two children, a brown eyed boy and a blue eyed girl. What are the genotypes of the parents and children?

Brown eyed boy: B b
Blue eyed girl: b b
Man: B b
Woman: b b

 

[BlueGas]

Question: Is the trait in the following pedigree dominant or recessive? Explain why. (2 marks)

 

[astab]

Indeterminate.
To be honest it's difficult to explain it but you figure it out by assuming that the trait is recessive and then assigning the recessive alleles to each affected member. You then use "trial and error" to see if it's correct. Assuming it's recessive, then the mum is (XtXt) and the dad is (XTY), then the possible combinations for their offspring are (using phenotypes) are 2 carrier females: 2 affected males, but their sons aren't affected. If you assume it's dominant and trial and error the different combinations, you'll also get the same result.

Hope this helps

 

[BlueGas]

Indeterminate.
To be honest it's difficult to explain it but you figure it out by assuming that the trait is recessive and then assigning the recessive alleles to each affected member. You then use "trial and error" to see if it's correct. Assuming it's recessive, then the mum is (XtXt) and the dad is (XTY), then the possible combinations for their offspring are (using phenotypes) are 2 carrier females: 2 affected males, but their sons aren't affected. If you assume it's dominant and trial and error the different combinations, you'll also get the same result.

Hope this helps

A more simplified answer would be that the trait is recessive because it does not appear in all generations, if it did it would have been dominant. This is a really easy way for figuring out questions like these.

 

[astab]

Is that what your answers say? I'm not entirely convinced that it's recessive.

 

[BlueGas]

Is that what your answers say? I'm not entirely convinced that it's recessive.

Well it's not a question taken out of the book, I just looked up a pedigree that had a recessive trait and I found the above pedigree. Well I say it's recessive because like what I said it does not appear in all generations.

 

[Chris_S]

Isn't it recessive as girl has it but parents don't have it?

 

[useless stick]

A pulse oximeter is an instrument that can be used to measure the oxygen saturation levels in the blood. It can be clipped onto a finger and, by passing a beam of infrared light through the finger, the amount of infrared light absorbed can be used to measure the saturation level of harmoglobin and thus the oxygen saturation level. The oxygen saturation level is delivered as a percentage.

You could also use a arterial blood gas analysis which is essentially a invasive technology that involves taking a same of the patients blood and then analysing the pH of the blood through a blood gas analyser to determine the carbon dioxide levels. This technology if the physician suspects that the patient has lung disease, kidney disease, metabolic disease or injuries that affect breathing.

If you want a more modern technology a unisense micro optode and oxygen microsensor could work.
Unisense micro-optode utilises optical fibres that quenchers the luminescence caused by the collision of oxygen molecules. For more
information consult the website.
http://www.unisense.com/MicroOptode

A oxygen microsensor is a Clark type sensor that measures oxygen by having it diffuse through a semipermeable membrane and reacting with silver chloride to produce electricity. For more info use the link below.
http://www.unisense.com/O2/

To be honest I wouldn't recommend the above two as they are mainly used for research relating to blood, medicine and whatnot , as well as the fact that there is not a great deal of information on them.

 

[useless stick]

I'd have to say that it is recessive as there has been a huge gap where the trait has not been present, it is definitely not dominant as it has only appeared three times and the chances of it being sex linked is relatively low as only 1/7 of the males born have the trait and they have a 50% chance of getting it.

 

[useless stick]

The main one I learnt, personally wasn't haemogloblin but perflurochemicals

Artificial blood can be advantageous over real blood as there is a shortage of real blood, a need for real blood to be cross-matched as certain blood types reject blood from other blood types due to the antigen contained within red blood cells, a need for there to be an absence of infectious agents and lastly as artificial blood often have a longer shelf life than real blood (e.g Perflurochemicals last for 12 months compare to real blood which has a shelf-life of around 3 months).

An example of artificial blood is Perflurochemicals. It is completely sterile and disease-free as it does not contain any biological materials, it has a longer shelf life than real blood of approximately 8 more months, it can be stored at room temperature hence making it suitable to be transported conveniently in emergency vehicles such as ambulances, furthermore perflurochemicals can be used universally with all blood types, is cheaper to produce compared to using real blood, is able to dissolve 5 times more oxygen than real blood. An example of Perflurochemicals is Oxycyte TM which is currently under trial.

Disadvantages associated with perflurochemicals include that it's around 70x smaller than real blood, hence allowing it to pass through places where real blood would not normally be able to travel in, it's need to be mixed with lipids to form an emulsion that can be mixed with blood and how it can only be used to replace the function of Red blood cells, essentially, as perflurochemicals are not able to act as disease-fighting instruments, such as white blood cells are, nor are they able to act as clotting agents, like platelets.

Therefore, although real blood is disadvantageous over artificial blood in it's cost-efficiency, artificial blood with current technology, is not able to fully replace all functions of real blood, and because of it's size, may affect metabolic processes in the body.

An advantage is that artificial blood reduces blood born diseases such as AIDS and hepatitis, in addition it is also non specific and can be used for anyone rather than people with weird blood types e.g a person with O- can only get blood from another person with O- blood.

A disadvantage is that artificial blood is currently expensive to produce and it has some side effects such as increased chance of heart attacks.

 

[BlueGas]

Interesting question: Name ONE technology that could be used to establish evolutionary relationships and explain how the data revealed by this technology can be used to establish evolutionary relationships. (3 marks)

 

[Fiction]

Is that what your answers say? I'm not entirely convinced that it's recessive.

Agreed with what blue gas said. If it doesn't appear in all generations, then it must be recessive as recessive alleles are masked by the dominant allele. Why don't you think that it's recessive?