VCE Biology Question Thread

[tiredandstressed]

Hi
In the study design there is a table about requirements on the poster/practical report and it says 'limitations in data' and 'limitations in method'. What is the difference, what does 'in data' mean?
Thanks

Limitations in method: what there something in the method/ equipment that was faulty/inadequate
Limitations in data: are there any limitations in the results directly (e.g. replicates, outliers)
Mostly interrelated, and don't need to be distinguished you can integrate them in your discussion of limitations.

[ErnieTheBirdi]

How would I answer a natural selection question? I know I have to mention variation, inheritance, and all that but how do I know when it is a natural selection question that I have to answer it specifically like that? Also if it is an artificial selection question would I answer the same way using VESIG?
V: Variation
E: Environmental pressures
S: Selection Pressures
I: Inheritance
G: Gradual Change

[Bri MT]

How would I answer a natural selection question? I know I have to mention variation, inheritance, and all that but how do I know when it is a natural selection question that I have to answer it specifically like that? Also if it is an artificial selection question would I answer the same way using VESIG?
V: Variation
E: Environmental pressures
S: Selection Pressures
I: Inheritance
G: Gradual Change

Hey, do you understand why/how VESIG works? i.e. does the overall process make sense to you?

Yes, you can approach artifical selection questions in the same way as natural selection question - exact same concept just a different type of selective agent than you're used to

[ErnieTheBirdi]

Hey, do you understand why/how VESIG works? i.e. does the overall process make sense to you?

Yes, you can approach artifical selection questions in the same way as natural selection question - exact same concept just a different type of selective agent than you're used to

Yes I do understand it and like the overall process, it's how to really structure the answer that confuses me

[makram]

What are ways to improve the accuracy, precision, reliability and validity of an experiment?

[Chocolatepistachio]

Reliability can be improved by doing multiple trials to get a more accurate result. For validity ensuring controlled variables are kept constant and for precision using accurate equipment

[homeworkisapotato]

What are ways to improve the accuracy, precision, reliability and validity of an experiment?

Adding onto Chocolatepistachio:
Accuracy (how similar your results are to the expected/correct results) and precision (how similar the results are with each other) are linked with reliability (whether the experiment can be reproduced and repeated to get the same/similar results), and  these contribute to validity (whether the experiment actually tests what it claims to be testing).

To fix accuracy, you want to do these:
- calibrate and maintain instruments
- repeat the experiment
- use equipment with less uncertainty (like if you're measuring 5mL, you want to use a measuring cylinder with 0.5mL intervals rather than a beaker with 10mL intervals)

To fix precision you can take some from accuracy:
- calibrate and maintain instruments
- if using live organisms such as mice make sure they're all the same age/species/health in each sample to minimise random errors. What I mean is that if you have 15 adult aged mice in a vaccination experiment and 5 old mice and then the old mice die after taking the vaccine, your results aren't really that precise and that may prevent the vaccine from being trialled on humans (because a 66% success rate is not good) but in reality your vaccine IS successful, it's just that 5 mice are old. I suppose these come under controlled variables.
- have a large sample size to minimise effect of outliers
- use equipment with less uncertainty (like if you're measuring 5mL, you want to use a measuring cylinder with 0.5mL intervals rather than a beaker with 10mL intervals)

To ensure validity have controlled variables, control groups (either with a positive or a negative control), specific measurements for everything, and ensure to test only one independent variable.

Controlled variables to include in your experiment
- environmental conditions: temp, access to light, light intensity, light wavelengths (light is usually only relevant for enzymes and photosynthesis experiments)
- species of whatever
- number of everything
- duration of experiment
- if using live organisms then have the same diet for them given at the same time of the day (very important for cellular respiration)
- also with live organisms, whatever you're doing to them, do it at the same time. Vaccination, measuring glucose concentration, or whatever, do it at the same time every day/whenever you're doing it.

Anyone feel free to correct me as I may be wrong 

[wingdings2791]

Guys, is increasing the sample a size acceptable for questions asking for limitations in experimental design? In one of these questions, the sample size was one, but the marking scheme doesn't list increasing the sample size as an accepted answer.

[homeworkisapotato]

Is it possible for you to send a pic of the question?

[Chocolatepistachio]

For this question would this be a sufficient answer
Describe ultrafiltration in the nephron

Ultrafiltration occurs when high blood pressure in the glomerulus forces water/ ions/small molecules into bowman’s capsule. Large molecules such as red blood cells and proteins cannot pass through the glomerulus. The fluid in the bowmans capsule is referred to as the filtrate. The filtrate enters the proximal convoluted tubule where glucose and amino acids are reabsorbed.

[Sine]

For this question would this be a sufficient answer
Describe ultrafiltration in the nephron

Ultrafiltration occurs when high blood pressure in the glomerulus forces water/ ions/small molecules into bowman’s capsule. Large molecules such as red blood cells and proteins cannot pass through the glomerulus. The fluid in the bowmans capsule is referred to as the filtrate. The filtrate enters the proximal convoluted tubule where glucose and amino acids are reabsorbed.

You could possibly switch "high BP" for "hydrostatic pressure" which is the main driving force. The actual filtrate is also sometimes called the glomerular filtrate or ultrafiltrate.

Also if you are going to talk about reabsorption you might want to mention secretion of some molecules. Although, for this specific question you shouldn't have to talk about reabsorption/secretion.

[Chocolatepistachio]

For this question would this answer be fine
Briefly explain how homologous chromosomes are randomly assorted into the two daughter cells resulting from meiosis 1.

Homologous chromosomes containing maternal and paternal genetic information are sorted into gametes independent of other pairs of chromosomes. This is due to crossing over.

[Owlbird83]

For this question would this answer be fine
Briefly explain how homologous chromosomes are randomly assorted into the two daughter cells resulting from meiosis 1.

Homologous chromosomes containing maternal and paternal genetic information are sorted into gametes independent of other pairs of chromosomes. This is due to crossing over.

I think this is good, however the part about crossing over doesn't fit here and isn't really right. Independent assortment is not due to crossing over (crossing over is when the homologous pairs exchange genetic material, and is a different thing from independent assortment).
If it asked about how genetic info/alleles are randomly separated into each gamete you could mention crossing over I think, but not here, because it's talking about the whole chromosomes.
Good job on the first sentence though!

[tiredandstressed]

For this question would this answer be fine
Briefly explain how homologous chromosomes are randomly assorted into the two daughter cells resulting from meiosis 1.

Homologous chromosomes containing maternal and paternal genetic information are sorted into gametes independent of other pairs of chromosomes. This is due to crossing over.

*add*
Independent assortment is the separation of non-matching chromosomes during meiosis. Thus, it is the formation of random combination of chromosomes in meiosis and genes of different pairs of homologous chromosomes by the passage according to the laws of probability of one of each diploid pair of homologous chromosomes into each gamete independently of the other pair.  The variation in sexually reproducing species increases with the increasing number of chromosomes. even without the impact of crossing over.

[Chocolatepistachio]

For this question would this answer be fine
Describe the directions in which oxygenated and deoxygenated blood flows through the circulatory system.

Blood enters the heart through the inferior and superior vena cava. Deoxygenated blood enters the superior vena cava and passes through the right atrium. It then flows through the tricuspid valve until it is full and then the right ventricle pumps the blood through the pulmonary arteries to the lungs. The left atrium receives oxygenated blood from the lungs via the pulmonary veins. Blood passes through the bicuspid valve to the left ventricle and is pumped to the rest of the body.