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December 16, 2019, 06:21:06 pm

Author Topic: HSC Biology Question Thread  (Read 141352 times)  Share 

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InnererSchweinehund

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Re: HSC Biology Question Thread
« Reply #1320 on: May 17, 2019, 09:52:28 pm »
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Hi  :)!

I was wondering if someone could explain what the control is in Pasteur's experiment??
Is it the flask with the straight neck or the sterilized broth??

At the moment I have this as my response and not sure if it is correct:
Is a control used in this experiment? If so, identify it and explain why it was used.
The control in this experiment is the broth. A constant amount of broth is used, and boiled for the same amount of time. Since the aim of this experiment is to test whether nutrient broth could spontaneously generate microbial life, the broth was boiled to sterilize, so it it contained no living microbes. By having a sterile broth in both flasks it was impossible for germs to spontaneously generate, hence, it could be determined that organisms carried in the air were able to enter the straight neck flask and contaminate broth and cause it to decay.

Thanks in advance!!

InnererSchweinehund

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Re: HSC Biology Question Thread
« Reply #1321 on: May 18, 2019, 08:11:49 am »
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At the moment I have this as my response and not sure if it is correct:
Is a control used in this experiment? If so, identify it and explain why it was used.
The control in this experiment is the broth. A constant amount of broth is used, and boiled for the same amount of time. Since the aim of this experiment is to test whether nutrient broth could spontaneously generate microbial life, the broth was boiled to sterilize, so it it contained no living microbes. By having a sterile broth in both flasks it was impossible for germs to spontaneously generate, hence, it could be determined that organisms carried in the air were able to enter the straight neck flask and contaminate broth and cause it to decay.


Or is this better / more accurate?

The control in Pasteurís experiment is the straight necked flask, which allowed particles from the air to fall into the flask and contaminate it. Pasteur believed that organisms that contaminated the broth and caused it to decay must be carried in the air and not be spontaneously generated. Therefore, by having a straight necked flask, he was able to observe the different between the two flasks - one that was exposed to microbes, and one that wasnít. If the theory of spontaneous generation was correct, the broth in both flasks would be cloudy and decaying, even if they werenít directly exposed to the air (like the Swan necked flask).

stella_atarnotes

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Re: HSC Biology Question Thread
« Reply #1322 on: May 19, 2019, 02:14:07 pm »
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Hi  :)!

I was wondering if someone could explain what the control is in Pasteur's experiment??
Is it the flask with the straight neck or the sterilized broth??

At the moment I have this as my response and not sure if it is correct:
Is a control used in this experiment? If so, identify it and explain why it was used.
The control in this experiment is the broth. A constant amount of broth is used, and boiled for the same amount of time. Since the aim of this experiment is to test whether nutrient broth could spontaneously generate microbial life, the broth was boiled to sterilize, so it it contained no living microbes. By having a sterile broth in both flasks it was impossible for germs to spontaneously generate, hence, it could be determined that organisms carried in the air were able to enter the straight neck flask and contaminate broth and cause it to decay.

Thanks in advance!!

Hi! You're correct in the aim- that Pasteur was trying to test the theory of spontaneous generation where living organisms arose from a non-living source. However, you might be a little confused between control and controlled variable. The controlled variable is something you keep constant throughout your experiment to ensure that and results you obtained are in fact due to you changing the independent variable. In this case, a constant amount of broth was used for both flasks and they were both boiled to eliminate any pre-existing microorganisms. Pasteur then used identical swan-necked flasks (another controlled variable) and snapped the neck off one flask so that it became a straight neck. The straight neck flask allowed for organisms from the air to enter the broth and thus micro-organisms grew in the broth. It would be more accurate for you to identify the positive and negative controls in this experiment; the positive control is the flask which you expect growth and the negative control is the flask where you wouldn't expect growth. So your negative control would be the swan necked flask and your positive control would be the straight neck flask.

Hope that helps!

InnererSchweinehund

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Re: HSC Biology Question Thread
« Reply #1323 on: May 19, 2019, 04:28:06 pm »
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Kombmail

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Re: HSC Biology Question Thread
« Reply #1324 on: June 10, 2019, 05:29:50 pm »
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Yall Pls help me with this bit!!!! I really need help with what to write?!

Q. 4. Apply your understanding of evolution by natural selection to explain how plants and animals have developed such complex and successful defences against pathogens.
-KgkG-

InnererSchweinehund

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Re: HSC Biology Question Thread
« Reply #1325 on: June 12, 2019, 01:28:44 pm »
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Q. 4. Apply your understanding of evolution by natural selection to explain how plants and animals have developed such complex and successful defences against pathogens.

Hi!

Basically what this question is asking you is: How have plants and animals have evolved over time (due to natural selection) to be able to successfully defend themselves against pathogens?

The most basic answer to this question would be that due to natural selection, plants and animals that didn't have certain adaptations against pathogens would have died. This allowed plants and animals with the adaptations to reproduce and produce offspring with the adaptation.

An example of this is the behavioural adaptation of mammals and birds grooming themselves to remove parasites (ticks, fleas, lice).
     This prevents a parasitic relationship that can be potentially harmful to the animal.
Another behavioural and structural adaptation of animals in fly infested areas are large ears (eg. elephants). Whilst this adaptation allows them to
     release heat easier, as the blood vessels in the ears are closer to the surface, it also provides them with an effective mechanism to swat away flies,
     hence preventing flies landing on and biting them. They can also hold branches with their trunks to swat flies.

An example of a plant adaptation is the production of essential oils, which act as toxins against bacteria and fungus.
A structural plant adaptation are thick, waxy cuticles, or thorns or spines to prevent against predators.   

Plants and animals that were unable to do this, wouldn't have been able to survive.

Here are two good articles with further, more in depth explanations:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3189355/
https://courses.lumenlearning.com/boundless-biology/chapter/plant-defense-mechanisms/

As it is an explain question, it is probably good form to make a judgement to say how successful each of these adaptations are.
(If it was an evaluate question you must include a judgement!!)

Hope this provides you with a few ideas to get you started!!

 :D

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Re: HSC Biology Question Thread
« Reply #1326 on: July 03, 2019, 12:04:07 pm »
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Hi everyone  :)
Im stuck with this dodgy question here (Question 4b and d) and am in urgent need of help.
If anyone could send help it would be very much appreciated. Thank you in advance.  ;D ;D ;D

For 4a i got 3.2 x 10^-11g and 4c i got 28.8pi (90.47787cm^3)

sofe2003

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Re: HSC Biology Question Thread
« Reply #1327 on: July 03, 2019, 03:35:41 pm »
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just for reference everyone the question is " calculate how many haemoglobin molecules are in one red blood cell" plz help this is urgent this assignment is due tomoz

sofichu

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Re: HSC Biology Question Thread
« Reply #1328 on: July 09, 2019, 12:34:39 am »
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hey guys! i was wondering if someone could explain what the difference is between a nucleosome and a chromatosome (in the process of chromosome formation)
thanks!!
HSC 2019 ó Advanced English, Extension 1 English, Extension 1 Maths, Extension 2 Maths, Chemistry, Biology, Modern History

Kombmail

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Re: HSC Biology Question Thread
« Reply #1329 on: July 09, 2019, 10:56:32 am »
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Hi  :)!

I was wondering if someone could explain what the control is in Pasteur's experiment??
Is it the flask with the straight neck or the sterilized broth??

At the moment I have this as my response and not sure if it is correct:
Is a control used in this experiment? If so, identify it and explain why it was used.
The control in this experiment is the broth. A constant amount of broth is used, and boiled for the same amount of time. Since the aim of this experiment is to test whether nutrient broth could spontaneously generate microbial life, the broth was boiled to sterilize, so it it contained no living microbes. By having a sterile broth in both flasks it was impossible for germs to spontaneously generate, hence, it could be determined that organisms carried in the air were able to enter the straight neck flask and contaminate broth and cause it to decay.

Thanks in advance!!

Both broths were under the same experimental conditions however flask one had a straight neck tube. The straight neck tube was conducted to make sure the contaminants arenít forming from the external environment.
-KgkG-

Coolmate

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Re: HSC Biology Question Thread
« Reply #1330 on: July 10, 2019, 07:08:53 pm »
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Hey Everyone,

I am in Year 11 and am going to do my Biology prelim exams soon. I was wondering whether anyone has any good tips and what the most important things I should study that I can use for the exam, to achieve a high mark?

Also, does anyone have any past prelim papers for biology?... (The new syllabus is making it hard to find them).

Thanks in advance,
Coolmate ;)
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ushna

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Re: HSC Biology Question Thread
« Reply #1331 on: July 14, 2019, 09:25:45 pm »
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Hey. For pedigrees, how do we know if a trait is dominate or recessive or whether it is X-linked dominant or X-linked recessive?

Kombmail

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Re: HSC Biology Question Thread
« Reply #1332 on: July 17, 2019, 07:57:08 pm »
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Hey. For pedigrees, how do we know if a trait is dominate or recessive or whether it is X-linked dominant or X-linked recessive?
If itís dominant, it would be represented by a capital letter, if recessive a lower case. Iím not too sure about the other two.
-KgkG-

laura_

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Re: HSC Biology Question Thread
« Reply #1333 on: July 18, 2019, 07:28:50 pm »
+2
Hey. For pedigrees, how do we know if a trait is dominate or recessive or whether it is X-linked dominant or X-linked recessive?

On a pedigree, there are clues you can look for when identifying if a trait is X-linked or autosomal and dominant or recessive. It is mainly a common sense thing but you can ask yourself questions to work through it.

X-Linked or Autosomal
Does this trait occur equally in men and women?
(If carriers are shown, are there carriers of both sexes?)

If the trait occurs equally in both genders, then it is most likely autosomal.

Dominant or Recessive
Does every affected child have an affected parent? (Then it is most likely dominant.)
Does the trait disappear from a family line and reappear (skip a generation)? (Then it is recessive.)
Are there carriers? (Recessive.)

In Summary:
X-Linked Dominant: Occurs more often in women, no carriers, cannot skip generations, every child has affected parents.
X-Linked Recessive: Occurs more in men, female carriers (but no male carriers), can skip generations.
Autosomal Dominant: Equal in both genders, no carriers, cannot skip generations, every child has affected parents.
Autosomal Recessive: Equal in both genders, carriers (but these may not be shown directly), can skip generations.

If itís dominant, it would be represented by a capital letter, if recessive a lower case. Iím not too sure about the other two.

This is true if they give you the genotype.

eg. Dominant allele (B) and recessive allele (b). Then genotypes could be (BB, Bb or bb)

If it is X-linked, the alleles and genotypes would look like this:  XR or Xr. Then genotypes could be ( XR XR,  XRXr or XrXr in females. In males they could be XRY or XrY.

Note: Remember men would only get one copy of the X chromosome.
« Last Edit: July 18, 2019, 07:32:24 pm by laura_ »
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Coolmate

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Re: HSC Biology Question Thread
« Reply #1334 on: July 25, 2019, 07:08:28 pm »
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Hi Coolmate!

This response is quite a while after you first posted your question, but I hope it can still help you.

Firstly, get on top of your notes + key concepts ASAP!! Biology is quite content heavy so if you can grasp the concepts and practice them from the very start until the very end, you will find it very useful. Make sure you ask your teacher to go over any concepts you don't understand, and pay attention to any feedback they give you on assignments/exams.

I found the ATAR Notes biology course notes super helpful, and if you can, try and attend some ATAR Notes biology lectures because they recap the previous topics, and prepare you for what's coming up - this definitely gives you an advantage over all your peers who haven't attended!! You should also look at the previous lecture slides and use them to your advantage when making study notes!!

Finally, find out what study techniques work for you. It's better to do this while you are in year 11, so you can set yourself up well for year 12.

Best of luck and have fun!! 
 :)

Hi InnererSchweinehund thanks so much for your response this will definetly help me in my biology studies! 😀👍
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