HSC Biology Question Thread

[Potatohater]

Hey, I'm not sure how to answer this question as I'm a bit confused as to which dot point it refers to and which examples to use:
Relate specialised features of the eyes of TWO named animals to their environment (2 marks)

[pikachu975]

Hey, I'm not sure how to answer this question as I'm a bit confused as to which dot point it refers to and which examples to use:
Relate specialised features of the eyes of TWO named animals to their environment (2 marks)

Humans have rods and cones in the retina which allow for colour perception and sight in general to navigate around, communicate, and for depth perception.

Flies have a compound eye with thousands of ommatidia which provide dots of shade and colour to indicate predators or prey with a change in colour/shade.

[angelahchan]

Hi, does anyone know how much info we have to know about Macfarlane Burnet? I've honestly learnt nothing about him in bio class, but I've come across the occasional question about him...

[Potatohater]

Humans have rods and cones in the retina which allow for colour perception and sight in general to navigate around, communicate, and for depth perception.

Flies have a compound eye with thousands of ommatidia which provide dots of shade and colour to indicate predators or prey with a change in colour/shade.

Ahh ok, I got it mixed up with a different dot point and wrote about honey bees and ratlle snakes but I see now

[Potatohater]

Hi, does anyone know how much info we have to know about Macfarlane Burnet? I've honestly learnt nothing about him in bio class, but I've come across the occasional question about him...

I dont think we need to know much, just who he is and what scientiffic knowledge he contributed to. It rarely comes up though.

[stephjones]

Hi, does anyone know how much info we have to know about Macfarlane Burnet? I've honestly learnt nothing about him in bio class, but I've come across the occasional question about him...

So the fact that we have to know about him (but don't really cover him that much) is because he's mentioned in the overarching DP 5 in Search for Better Health:

MacFarlane Burnet’s work in the middle of the twentieth century contributed to a better understanding of the immune response and the effectiveness of immunisation programs

So he came up with this theory that an organism's immune system can distinguish between its own cells and foreign cells (which triggers the immune response) which basically allowed for the the development of more effective immunisation programs.

In 2012 for an 8 marker the HSC asked for his contribution into the understanding of the nature of the prevention of infectious diseases, and the sample answers BOSTES released just included this:

Specific studies and development of techniques to understand viruses also led MacFarlane Burnet to begin our understanding of the immune system. Burnet concluded that a human immune system contained unactivated B cells that could be activated and produce an immune response following their exposure to a microbe. This led to the development of the understanding of mechanisms underlying previous vaccination technologies and led to the exploration of further vaccination technologies such as sub unit vaccines.

which tbh is all I'm going to remember

[itssona]

heey guys, in the dotpoint for analysing methods for purifying drinking water, do we need to give the disadvantages of methods of water purification??

[pikachu975]

heey guys, in the dotpoint for analysing methods for purifying drinking water, do we need to give the disadvantages of methods of water purification??

Nah I don't think so, the questions always relate to "Describe two methods of cleaning water..."

[DalvinT]

Hey!
How does Aldosterone help with water retention?
Wouldn't an increase in solvent concentration make it worse, especially when dehydrated?
Yet, when we are dehydrated, Aldosterone is still secreted...

[angelahchan]

Hey!
How does Aldosterone help with water retention?
Wouldn't an increase in solvent concentration make it worse, especially when dehydrated?
Yet, when we are dehydrated, Aldosterone is still secreted...

Aldosterone increases sodium reabsorption but decreases potassium reabsorption. Increased sodium (main solute of blood) = higher concentration of sodium in blood compared to water, meaning the concentration of water in blood decreases (relative to sodium, so this decrease in water conc. doesn't meant the actual water levels have decreased). So, more water from distal tubule and collecting duct is reabsorbed via osmosis as water moves from high concentration to low, compensating for the decrease in water concentration (thus increased water retention).

[liya1234]

Aldosterone increases sodium reabsorption but decreases potassium reabsorption. Increased sodium (main solute of blood) = higher concentration of sodium in blood compared to water, meaning the concentration of water in blood decreases (relative to sodium, so this decrease in water conc. doesn't meant the actual water levels have decreased). So, more water from distal tubule and collecting duct is reabsorbed via osmosis as water moves from high concentration to low, compensating for the decrease in water concentration (thus increased water retention).

This makes a lot of sense but why isn't ADH just released instead because doesn't it increase reabsorption of water? These two always confuse me a lot idk

[angelahchan]

This makes a lot of sense but why isn't ADH just released instead because doesn't it increase reabsorption of water? These two always confuse me a lot idk

Yeah, ADH also increases reabsorption of water- but directly by making the distal and collecting tubule more permeable to water. I think ADH is used when there's already high sodium levels in blood but also low water levels, so use of aldosterone would make sodium levels too high.  (I'm not entirely sure though, just my guess as to a reason why)

[GabbyJesus]

This makes a lot of sense but why isn't ADH just released instead because doesn't it increase reabsorption of water? These two always confuse me a lot idk

I learnt it a different way, when sodium ions are reabsrobed as a result of aldosterone, water follows via omosis and therefore is also reabsorbed. This leads to increase in blood volume and blood pressure.

[DalvinT]

Aldosterone increases sodium reabsorption but decreases potassium reabsorption. Increased sodium (main solute of blood) = higher concentration of sodium in blood compared to water, meaning the concentration of water in blood decreases (relative to sodium, so this decrease in water conc. doesn't meant the actual water levels have decreased). So, more water from distal tubule and collecting duct is reabsorbed via osmosis as water moves from high concentration to low, compensating for the decrease in water concentration (thus increased water retention).

Ahhh! I see Thank you so muchhhh

[sidzeman]

Hey guys dotpoint from SFBH what are the distinguish features of every pathogen - e.g. prion's are the only pathogen with no genetic information at all.
Also, what are bigger fungi or macroparasites?