HSC Biology Examination Options

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Our Biology group has been exhausting at work placing collectively the options for the 2021 HSC Biology Examination Paper. Learn on to see the way you fared!


2021 HSC Biology Examination Options

Understand that these solutions weren’t written underneath examination situations and could also be longer than required.


Part I: A number of Alternative

Query Reply Answer
1 C Because the iodised salt efficiently handled the situation, the affected person more than likely has a deficiency of iodine.
2 D Frog spawning entails a feminine laying eggs and a male fertilising them with sperm.
3 B Pollen is manually transferred from the anther of 1 plant to the stigma of one other.
4 B Prescription drugs are an instance of a therapy that can be utilized for non-infectious illness, the others are examples of prevention for infectious illnesses.
5 C This meal will enhance blood glucose ranges. Insulin ranges rise to set off the storage of glucose to carry blood glucose ranges again down.
6 A A single chromosome can comprise hundreds of genes, so a big deleted section of a chromosome will have an effect on many genes.
7 C In DNA replication A pairs with T and C pairs with G.
8 D A conclusion should relate to the analysis drawback. Whereas A could also be true it’s a assertion for the dialogue, not a conclusion of a examine.
9 D It’s the position of ribosomes to type polypeptide chains as a part of protein synthesis.
10 A A is dominant and a single copy will produce a standard phenotype. a1 and a2 produce cystic fibrosis, however a1 has the very best frequency so a1/a1 is the more than likely genotype of a cystic fibrosis affected person.
11 B The transgenic crops have more than likely pollinated their close by family.
12 C HCG is launched as soon as the embryo has implanted. Fertilisation can not happen till round 2 weeks after the tip of the menstrual cycle when ovulation happens.
13 A When there may be increased availability of water the stomata can open extra and launch extra water via transpiration. When there may be much less water accessible the stomata will partially shut to scale back water loss.
14 A CJD will be attributable to a mutation or by publicity to an infectious agent.
15 B Bonds have shaped between adjoining thymine bases on a single strand of DNA. This is called a thymine dimer.
16 C Because the UV dose is elevated the variety of bacterial colonies lower. There isn’t any management plate.
17 B Sister chromatids separate in anaphase of mitosis.
18 D This sample is per a sex-linked recessive dysfunction if the feminine is a service (heterozygous).
19 C The graph signifies that the 2 alleles can produce three completely different phenotypes – quick, medium and sluggish alcohol metaboliser.
20 B The enzyme exercise has decreased which has resulted in a build-up of acetaldehyde in mice with the ALDH2 allele.

Would you like the arrogance to reply like this underneath stress?

Part II: Prolonged Response

Query 21

(a) Label the cell wall and nucleoid (non-membrane certain DNA).

(b) Field 1: Micro organism are grown in pure tradition. Field 2: Pig 2 develops the identical signs as pig 1.

(c) The advantage of Farm 1 treating with antibiotics is that the pigs recuperate shortly, and the illness won’t unfold to different pigs. The limitation of this technique is the probability that the micro organism will develop antibiotic resistance and the antibiotics will ultimately not work on this illness.
The advantage of the technique utilized by farm 2 is that it eliminates potential vectors/reservoirs of the illness from the farm so they can not unfold it. A limitation of this technique is it does nothing to assist the pigs which can be already sick and spreading the illness. Ideally these two methods could be used on the similar time.

Query 22

Let B = black, b = white. If white is recessive then the white rabbit has the genotype bb and if the black rabbit has a mom with white fur then it have to be heterozygous (Bb).

B b
b Bb bb
b Bb bb

The offspring can be 50% heterozygous black (Bb) and 50% homozygous white (bb), thus a ratio of black to white of 1:1.

The offspring can be 50% heterozygous black (Bb) and 50% homozygous white (bb), thus a ratio of black to white of 1:1.


Query 23

Take a look at quantity two reveals that ovulation isn’t occurring. With the intention to be legitimate the check should have a management line, so assessments one and two are the one ones which can be legitimate. Take a look at primary has a management line and a check line, so it reveals a optimistic consequence for LH and ovulation. Take a look at two has a management line to verify it’s working, however there isn’t any second check line. Due to this fact check 2 is a unfavorable consequence for LH and ovulation isn’t occurring.


Query 24

(a) This trait is more likely to be the results of a somatic mutation because it has not been inherited or handed on. The male with the trait has not inherited the trait from his mother and father as it’s not potential for 2 homozygous recessive (unaffected) mother and father to have offspring with a dominant trait. If the affected male was homozygous dominant, they might move the trait to all of their offspring and in the event that they have been heterozygous dominant then round half of their offspring would have the trait. Nevertheless, the pedigree signifies that not one of the offspring have the trait.

(b) Somatic cells are physique cells and germ cells change into intercourse cells. Mutation B will solely have an effect on twin 1 because it occurred after the twins had shaped. This mutation can be discovered within the germ cells and somatic cells of dual one. Consequently, Twin 1 could move this mutation on to future offspring. Mutation C will solely have an effect on twin 2 because it occurred after the twins had shaped. This mutation will solely have an effect on some somatic cells because it occurred after germ cells and somatic cells had shaped. Twin 2 won’t move this mutation on to its offspring.


Query 25


2021 HSC Biology Exam Solutions Question 25 graph


(b) The best ear is functioning throughout the regular listening to vary, whereas the left ear is considerably impaired. There isn’t any profound listening to loss, however a listening to support or different gadget could also be required.

(b) The best ear is functioning throughout the regular listening to vary, whereas the left ear is considerably impaired. There isn’t any profound listening to loss, however a listening to support or different gadget could also be required.

(c) A blockage of the outer ear signifies that sound can not enter the ear canal so a daily listening to support could be inappropriate. A bone-anchored listening to support (BAHA) can bypass the blockage (and the center ear) by receiving sound exterior the top and transmitting it to a tool that transmits vibrations into the cranium. The vibrations conduct via bone into the (absolutely useful) cochlea the place they’re transformed into electrochemical indicators that are despatched to the mind.


Query 26

The truth that the offspring have completely different patterns from their mother and father means that these novel coat patterns are initially a results of random mutation. Because the zebra inhabitants is changing into more and more remoted and small, they’re extra susceptible to genetic drift: in small populations, allele frequency is extra more likely to change because of random components, some traits could also be seen extra typically and others could also be misplaced. For instance, in a small inhabitants with low genetic variety, excessive ranges of inbreeding may end up in extra people being homozygous for uncommon recessive traits and so these traits seem extra regularly. There isn’t any proof supplied to counsel that these phenotypes are attributable to a rise of mutagens within the surroundings.


Query 27

Little one 3 could have sickle cell anaemia. Little one 1 is homozygous and the 2 allele copies are the identical size so they seem on high of one another to type the decrease band within the DNA profile. Little one 2 is heterozygous and has two completely different bands to symbolize the 2 alleles. Since little one 1 is unaffected it have to be the higher band that represents the allele that causes sickle cell anaemia. Little one 3 has two copies (overlapping) of the highest allele and can be affected by the illness. If little one 2 is heterozygous and unaffected then the situation have to be recessive.


Query 28

(a) mRNA has an essential position in protein synthesis inside human cells. Throughout transcription, RNA polymerase unwinds the gene (DNA) and makes a replica by including complementary RNA bases to the template strand. This gene copy is called messenger RNA (mRNA) and it detaches from the DNA, leaving the nucleus to discover a ribosome within the cytoplasm. The ribosome interprets the codons on the RNA right into a string of amino acids (polypeptide) that may ultimately change into a protein.

(b) mRNA vaccines are an instance of artificially acquired lively immunity, lively immunity is when the physique produces its personal antibodies to defend itself towards a pathogen. The mRNA comprises the directions for producing the spike protein of the virus and is launched into the physique via an injection. The mRNA enters the cells of the physique and the codons are translated right into a string of amino acids (polypeptide) by a ribosome. The polypeptide is folded and the tip product is similar spike protein that’s discovered on the virus.

The spike protein is introduced on the floor of the cell or launched into the physique. The spike protein is recognised as overseas by the immune system (e.g. by a T-helper cell) and antibodies are produced towards the spike protein. Reminiscence cells that recognise the spike protein are additionally produced and they’re going to launch a stronger secondary immune response if the precise virus is encountered sooner or later. Thus, somebody who’s vaccinated with the mRNA vaccine could have lively immunity to the virus as they will produce their very own antibodies towards it.


Query 29

The koalas are exhibiting behavioural variations to be able to keep a secure physique temperature. The Koalas change place relying on the temperature of the air. In response to the graph, Koalas have been solely noticed to curve up right into a ball when it was gentle. This posture would lower the floor space of its physique that’s uncovered to the chilly air to be able to retain warmth. When the temperature is gentle a koala is extra more likely to be present in a relaxed posture in comparison with when the temperature is scorching. When it’s scorching the Koalas usually tend to be noticed to be stretched out to extend the floor space of its physique that’s uncovered to the air in order that warmth will be misplaced. When it’s scorching it’s extra seemingly that Koalas can be noticed to ‘hug’ the tree, that is seemingly defined by the truth that the tree is cooler than the air and this enables warmth to switch from the physique of the koala to the tree.


Query 30

There’s an apparent distinction within the variety of circumstances of measles within the vaccinated and unvaccinated teams. The bar graph reveals that the unvaccinated group had seasonal outbreaks of measles with a number of hundred circumstances. The month of March in 1984 and 1985 had over 100 circumstances for instance, whereas the vaccinated group by no means had greater than round 10 circumstances in a month. The desk reveals that the unvaccinated group additionally had the next variety of deaths from measles (40) in comparison with the vaccinated group (2). The information helps the concept that the measles vaccine protects the inhabitants from measles.

Whereas the information within the desk means that the vaccine towards measles was additionally defending towards different illnesses that trigger Diarrhoea and dysentery or Oedema (because the variety of deaths was decrease within the vaccinated youngsters), that is extra more likely to be as a result of these youngsters are additionally vaccinated towards different illnesses or produce other life-style components akin to hygiene which can be defending them.  Pathogens that trigger illness have particular proteins or carbohydrates on their floor that the immune system makes use of to acknowledge the pathogen as a overseas invader. These molecules set off an immune response (antibody manufacturing) and so are known as antigens (antibody turbines). A vaccine comprises the antigen/s from a selected illness. When the vaccine introduces the antigen into the physique, the physique will launch a major immune response that ends in the manufacturing of reminiscence cells. These reminiscence cells will launch a stronger secondary immune response when the stay pathogen is encountered because the antigen on the floor of the pathogen can be encountered. Nevertheless, solely the particular antigen can be recognised by the reminiscence cells. Different illnesses could have completely different antigens that these reminiscence cells won’t acknowledge.


Query 31

Each pill therapies had round twice the symptom rating of the no pill therapies. Nevertheless, the examine reveals that there was little or no distinction in signs when taking the statin tablets and taking the placebo tablets, which means that the signs have been psychological. This means that a number of the signs sufferers report in response to the statins are the truth is imagined. It’s potential that some sufferers could possibly be satisfied to remain on the statins or be persuaded that the advantages of the drug outweigh the uncomfortable side effects. It seems from the desk that about 0.9% of sufferers have been probably having signs from the statin remedy and these circumstances ought to be investigated additional. It is also investigated to see what underlying situation could also be inflicting signs when no tablets are being taken. By way of pattern measurement, 60 sufferers is an inexpensive quantity, though the examine could possibly be repeated to enhance reliability. Asking sufferers to fee their signs is subjective as completely different people would possibly give the identical signs a special ranking. A rating that information the variety of days with the presence or absence of signs is likely to be an alternate. The therapy of ‘no tablets’ acted as a management however together with a separate management group of folks that didn’t have the identical historical past could be helpful for comparability. Total, that is an efficient examine with essential findings.


Query 32

Usually a unfavorable suggestions loop exists the place follicle stimulation hormone (FH) and luteinising hormone (LH) are launched by the mind and obtained by the testes. Sertoli cells within the testes reply by growing sperm manufacturing and producing inhibin, whereas Leydig cells reply by growing testosterone manufacturing. The ensuing manufacturing of testosterone and inhibin stop additional FSH and LH launch till sperm or testosterone ranges change into low (and create a stimulus). If a male athlete repeatedly takes anabolic steroids (testosterone) it will end in an inhibition sign to be despatched to the hypothalamus and the anterior pituitary. It will stop the discharge of FSH and LH which can stop sperm manufacturing within the testes. Over time, the athlete could discover that they change into infertile, and the dimensions of the testes could lower.


Query 33

(a) This course of is gene amplification utilizing recombinant plasmids in micro organism. (1) First the goal gene is recognized and lower out utilizing a restriction enzyme. Then the identical restriction enzyme is used to chop a bacterial plasmid. (2) The goal gene is inserted into the plasmid and annealed utilizing DNA polymerase. (3) The plasmid is inserted again into the bacterium which is allowed to breed by binary fission. On this approach, the goal gene is copied after which (4) the gene copies are lower out of the plasmids.

(b) One potential advantage of utilizing transgenic salmon in aquaculture is that they attain market measurement quicker than commonplace salmon. Transgenic salmon first attain market measurement simply earlier than they attain two years of age, whereas commonplace salmon don’t attain market measurement till they’re nearly 2.5 years outdated. By the point commonplace salmon attain market measurement at round 3.25kg, transgenic salmon are already shut to five kg. This might enhance the yield for the farmer.

(c) Transgenic species have had a gene from a special species (transgene) inserted into their genome via the method of genetic engineering. This type of biotechnology is used to present the goal species a selected protein and attribute that they didn’t have earlier than. Within the case of the transgenic salmon, the transgene is dominant and can produce the transgenic traits in any particular person carrying even a single copy of the gene.

Whereas including a brand new gene to a inhabitants initially will increase genetic variety of that inhabitants, there are issues about how transgenic species can impression biodiversity if they’re allowed to flee into the wild. As they’ve a development hormone and antifreeze protein the transgenic salmon have a powerful genetic benefit over wild fish. If the fish may escape into the wild populations, they might develop quicker and bigger, which implies they may doubtlessly outcompete the wild salmon and even different fish species that compete with them for meals. This might even remove wild salmon or different species which would cut back species variety and have unknown impacts on the meals internet. They might additionally interbreed with wild salmon, which might have the same final result by passing on the dominant transgenes to different fish. These captive animals may additionally introduce new illnesses into wild populations.

Within the manufacturing of those transgenic fish, a wide range of strategies have been employed to stop the fish from escaping and to stop them breeding in the event that they do escape. To start out with, utilizing Inland tanks reduces the danger that fish will escape into waterways and ultimately escape into the wild to breed with one another or interbreed with wild fish. The breeding females are stored in quarantine, which implies they’re utterly remoted with no likelihood of escaping.

Producing infertile triploid fish (XXX) signifies that even when they do escape, these fish can not interbreed with one another or with wild salmon. The sister chromatids are prevented from separating in meiosis II by stress shock therapy and so the egg cells are diploid. When they’re fertilised by a haploid (transgenic) sperm, the ensuing offspring can be triploid. Having three intercourse chromosomes prevents the event of intercourse organs within the fish. Any particular person fish that escapes into the wild will stay out its regular life span however won’t ever reproduce. These methods ought to be efficient at stopping any impacts on biodiversity by these transgenic fish.



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