HSC Biology Examination Paper Options

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Our Biology Staff has been exhausting at work placing collectively the options to the 2020 HSC Biology Examination. Learn the options under and see the way you went!

Part 1: A number of Selection

Query Reply Answer
1 B  Curling up is an motion that the animal has taken.
2 D  Sexual copy includes the fusion of gametes.
3 C  The egg is launched (ovulation), then fertilised by sperm. The growing blastocyst implants on the uterus wall and the outer layer finally turns into the placenta.
4 C  Plasmodium is the pathogen that causes the illness, the mosquito is the vector that transmits the plasmodium into the host.
5 B  Prokaryotes have round DNA, eukaryotes have linear DNA.
6 C  Different choices are too expensive or ineffective.
7 A  The variety of microbes counted might be depending on which meals is sampled. An untouched agar plate is used to examine for contamination.
8 C  Many non-infectious illnesses are genetic.
9 C  The intention is to decrease the incidence of pores and skin most cancers, so the incidence of pores and skin most cancers ought to be recorded.
10 A  The farmer is introducing a brand new allele into the inhabitants.
11 A  Mild will bend because it passes from air by the dense cornea.
12 B  Cloning is the simplest option to produce many people with the identical beneficial traits.
13 B Gene cloning is the replication of a gene.
14 D The heterozygous phenotype ends in some receptors, however not as many as a traditional cell. This represents an intermediate phenotype.
15 C  Drug C inhibits 70% of viral entry at this dose, with minimal toxicity.
16 B  Adenine at all times matches with thymine and guanine at all times matches with cyanine to kind a double helix. Thus, adenine and guanine will make up 50% of the bases.
17 B  Mutations that happen on non-coding DNA are usually not expressed as proteins and won’t have an effect on phenotype.
18 D  Primarily based on the pedigrees, D is the one person that shares DNA with each I and II.
19 A  A illustrates metaphase II of meiosis in a cell with 6 chromosomes. The cell begins with 6 chromosomes (3 homologous pairs) the daughter cells will find yourself with 3 solely.
20 A  Trait A is analogous in adoptive siblings that don’t share a lot genetics. Trait B may be very comparable in an identical twins with an identical genetics. Trait C has little similarity between shut relations or adoptive siblings.

Part 2: Quick response

Query 21

As Cholera might be unfold by contaminated water, boiling water earlier than ingesting it or utilizing it to clean meals will kill the micro organism and forestall them from infecting the physique. To forestall contamination of meals with the micro organism, arms ought to be washed completely with cleaning soap and water earlier than making ready meals or after going to the toilet. Guests and residents of cholera susceptible areas ought to be vaccinated as it will get rid of the illness within the physique earlier than sickness can happen, which additional prevents the unfold.


Query 22

The advantage of utilizing prescribed drugs corresponding to antibiotics and antivirals is that restoration from the illness happens quicker and reduces the possibility the illness will unfold to others.

A serious limitation of utilizing these medicine is that the pathogen (e.g. micro organism or virus) can turn out to be immune to the drug and it’ll now not work. The medicine act as a variety stress and any particular person micro organism or viruses which have mutations giving them resistance to the drug will survive and reproduce. This ends in a inhabitants that’s resistant and may unfold to different folks.


Query 23a

It is a level mutation, particularly a base substitution.


Query 23b

Chromosome mutations change the quantity or construction of chromosomes. For instance, an organism with trisomy has one further chromosome.


Query 24a

2020 Biology HSC Solutions 24a graph

Query 24b

See dotted line above.


Query 24c

The function of the kidney is to take away urea from the blood, preserve salt and water steadiness, take away toxins and regulate pH. That is achieved by energetic and passive transport. When the kidney stops functioning, haemodialysis can compensate. Blood is pumped out of the physique right into a dialyser which has a semipermeable membrane. Waste corresponding to urea and extra salt diffuses throughout the membrane into the dialysate answer which flows in the wrong way and is eliminated. Haemodialysis is a lifesaving remedy however depends on diffusion (passive transport) and so shouldn’t be as efficient as a kidney which may actively transport molecules in opposition to a focus gradient and reabsorb helpful substances.


Query 25a

The imply for each teams may be very comparable (43 and 40) which means that there isn’t any distinction between the 2 modes of fertilisation, however no conclusion might be produced from the info as there may be an excessive amount of variation (i.e. the usual deviation is simply too giant).


Query 25b

A bigger variety of species have to be included in every mode of fertilisation group as at the moment 6 species included for every group is an inadequate pattern dimension and the info shouldn’t be consultant. For instance, if invertebrate species corresponding to coral had been included within the exterior fertilisation group it might dramatically improve the common.


Query 25c

Most species that use exterior fertilisation exhibit much less parental care of the offspring, and they also produce many offspring however don’t make investments time, assets and power in them. With a excessive variety of offspring produced there’s a excessive probability that some will survive regardless.


Query 26a

Two dad and mom with the orange phenotype have had some offspring with yellow and a few with orange. Since two orange dad and mom have produced some yellow offspring, yellow should be recessive.


Query 26b

If the inheritance sample is autosomal recessive, then Particular person I could also be homozygous dominant (OO) or heterozygous dominant (Oo). Particular person II should be homozygous recessive (oo). On this case, a cross will end in all orange offspring or 50% orange and 50% yellow with no distinction between female and male offspring.

o Oo Oo
o Oo Oo


O o
o Oo oo
o Oo oo

If the inheritance sample is sex-linked then particular person I solely has one copy of the dominant allele as males solely carry one copy of the X chromosome. A cross between people I and II will end in all orange feminine offspring and all yellow male offspring. This may affirm that the inheritance sample is sex-linked.


Query 27a

Age, intercourse, schooling and socioeconomic standing had been taken under consideration and the research was performed over a very long time interval (11 years).


Query 27b

The information within the graphs does assist the speculation because the survival % was decrease at mid-range and high-range concentrations of arsenic publicity in comparison with low vary publicity over the 11-year research interval, in each women and men. At decrease concentrations of publicity <90 ug males had a decrease survival fee than females which signifies there could also be another issue inflicting mortality in males (e.g. larger danger of accident). The information additionally signifies that females are extra delicate to the arsenic within the vary 90-223 ug as they’d a lot decrease survival charges on this vary of publicity. Whereas the info does assist the speculation, different elements ought to be investigated to determine why females are extra delicate to mid-range publicity and why males have a decrease survival fee at low publicity. Survival % knowledge for a management group that was not uncovered to any arsenic would enhance the validity of the research.


Query 28a

Within the mannequin proven above, earlier than crossing over happens, every homologous chromosome consists of 1 paternal and one maternal chromatid. In actuality, throughout interphase, the DNA is replicated after which condenses in prophase to provide one chromosome composed of two an identical maternal chromatids and one chromosome composed of two an identical paternal chromatids.


Query 28b

The method of meiosis maintains genetic variation because it produces offspring which are genetically distinctive, i.e. they’ve a distinct mixture of alleles in contrast to one another or to their dad and mom. That is achieved by crossing over, the place segments of maternal and paternal chromosomes are swapped over creating new combos of alleles. Additionally it is enabled by random segregation the place the 4 chromatids for every chromosome pair are randomly allotted to the 4 daughter cells.


 Query 29

Mutation can have an effect on the gene pool of populations by introducing new alleles. Whereas mutations that happen in non-coding areas are unlikely to impact the organism, mutations that happen on a coding gene can produce a brand new allele of the gene which leads to a brand new phenotype. If this new phenotype is useful to the organism, they’re extra prone to survive and reproduce. Their descendants even have a better probability of surviving and thus the allele will turn out to be extra widespread within the inhabitants over time (evolution).

Genetic drift also can result in evolution. In small populations, allele frequency can change shortly as a result of random exterior elements corresponding to pure disasters. The occasion doesn’t act as a variety stress, however by probability might take away people with a particular allele. This allele is then misplaced from the inhabitants.


Query 30

Genetic applied sciences have had a major affect on the administration of each infectious and non-infectious illnesses. The potential to sequence DNA in itself has revolutionised administration of illness as applied sciences corresponding to sanger sequencing have allowed us to establish gene sequences that trigger non-infectious illness corresponding to phenylketonuria, which leads to early analysis and remedy. This expertise additionally permits us to sequence the genomes of viruses. Diagnostic instruments corresponding to real-time PCR can then be used to detect the presence of viral RNA/DNA in mucus samples (e.g. COVID-19).

Recombinant DNA expertise has enabled scientists to introduce overseas genes (from a distinct species) into micro organism, crops and animals. This has allowed for the creation of agricultural crops which are immune to infectious illness, as a result of an added gene. Introducing human genes into micro organism on this means causes them to provide human protein merchandise for medication, such because the hormone insulin which is used to deal with diabetes. A beta-carotene gene from corn has been launched right into a rice plant to provide transgenic golden rice. Consuming the rice will stop the vitamin A deficiency that causes blindness.

CRISPR-Cas9 is a not too long ago found information RNA-enzyme advanced that’s able to find a particular location on DNA and reducing it. This expertise makes it simpler to chop DNA to change off a gene (knock-out) or minimize can be utilized to insert a transgene. Switching off genes in mice permits us to review the operate of the gene in an animal that has comparable methods to people. That is utilized in medication to know how gene disfunction could cause illness. CRISPR-Cas9 has been tailored to provide gene drives which not solely modify a gene in a person, but additionally modify all copies of the gene of their future offspring. On this means, it could be potential to change mosquito populations, so that they finally turn out to be extinct or are usually not able to carrying the Malaria parasite. This has the potential to avoid wasting tens of millions of lives.


Query 31a

Blood glucose ranges should be maintained within the blood inside a sure degree to stop sickness. This homeostasis of blood glucose is maintained through a damaging suggestions loop. When blood glucose ranges improve (stimulus), that is detected by the pancreas (receptor/effector) which then releases insulin (response). Insulin is a hormone that causes the glucose molecules within the blood to be transformed into glycogen and saved within the cells of the physique, together with the liver. That is seen within the graph because the carbohydrate meal causes a spike in glucose ranges quickly after (Determine 1), with a corresponding spike in insulin (Determine 2). These then progressively cut back over time because the glucose within the blood is of course used up.

When blood glucose ranges are low (stimulus) the pancreas (receptor/effector) releases the hormone glucagon (response). This causes the saved glycogen to be damaged down into glucose, with the intention to carry the blood glucose degree again up. This may be seen within the figures as when the glucose ranges are low (0-1h Determine 1), the glucagon ranges are excessive (0-1h Determine 3).


Query 31b

Whereas upkeep of temperature and upkeep of glucose ranges are each achieved with a damaging suggestions loop, the upkeep of temperature includes the nervous system whereas glucose is maintained utilizing hormones solely. When physique temperature is simply too excessive or low it’s detected by receptor cells which then ship a sign through sensory neurons to the central nervous system (CNS). The CNS will course of the data and ship a sign through motor neurons to an effector (muscle or gland) that may enact a response (e.g. shivering when chilly, sweating when scorching).


Query 32a

The virus enters salivary glands and is discovered within the saliva. The saliva is now a route of exit out of the physique for the virus (6). The virus can then enter the tissue of the subsequent host by bites that are a mode of entry that bypasses the pores and skin barrier (1).


Query 32b

(i) The virus can’t be categorized as a mobile pathogen as it isn’t composed of a dwelling cell. Whereas the virus has some constructions present in cells (lipid bilayer, polymerase, RNA) there aren’t any organelles corresponding to ribosomes that are required for a cell to make the merchandise it must develop, survive and replicate. The virus, due to this fact, won’t be able to breed by itself, due to this fact it isn’t mobile and never thought of to be dwelling.

(ii) RNA polymerase is an enzyme that creates an RNA copy of a DNA or RNA sequence by attaching complementary RNA which then detaches from the unique DNA/RNA. Within the case of the viral RNA polymerase, it’s delivered into the cell together with the viral RNA. It then transcribes the viral RNA to kind viral mRNA. This mRNA accommodates viral genes which can then undergo translation by a ribosome within the cell. The ribosomes within the cell will produce viral proteins (L,P,M,G and N) which might be assembled to kind new viruses. The proteins L and P will assemble to kind extra RNA polymerase. The additional copies of RNA polymerase enable for quicker transcription of the Viral RNA, and in addition for a lot of copies of the complementary vRNA to be produced. These copies will turn out to be the RNA inside the new viruses which are assembled. Thus, the viral RNA polymerase has two roles, to transcribe the viral RNA for protein synthesis and in addition to make copies that kind the genome of the brand new viruses.


Query 32c

PEP prevents rabies from growing by making the most of the physique’s adaptive immune response. Usually when the physique is contaminated with a virus, the antigens on the floor of the virus are detected by the immune system and this triggers particular B-cells to start cloning. A few of the B cells turn out to be plasma cells and start producing antibodies. These antibodies have particular binding websites that match the antigen. The antibodies connect to the virus to stop virus entry into cells and appeal to macrophages. Killer T-cells detect contaminated physique cells and destroy them earlier than the illness can unfold.

Usually it might take round per week for the immune system to construct up a ample variety of particular immune cells. For rabies, this isn’t quick sufficient to stop the virus from infecting the nervous system and finally getting into the salivary glands (first graph half (c)). PEP solves this downside by introducing human antibodies (HRIGs) in opposition to the virus straight into the blood stream the place they are going to bind to the virus and assist the immune system eliminate it (artificially acquired, passive immunity). By the point the HRIG remedies are stopped, the vaccine included within the PEP has taken impact and the immune system has began producing its personal antibodies (artificially acquired, energetic immunity).

The vaccine will embody useless/weakened rabies virus or antigens extracted from the rabies virus. An instance of an antigen that could be used within the vaccine could be the G protein in Diagram 1 from half (b). After 7 days the physique begins to make its personal antibodies in opposition to the virus and this may be seen within the decrease graph for half (c), the physique maintains a excessive degree of antibodies till the virus is destroyed and now not discovered within the physique. With PEP the viral an infection by no means turns into full-blown rabies sickness.


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