Biology 2020 HSC exam pack

Students should:

• read the question carefully to ensure that they do not miss important components of the question
• have a clear understanding of key words in the question and recognise the intent of the question and its requirements
• plan the response to assist in the logical sequencing of information
• integrate relevant scientific terms into their responses
• engage with any stimulus material provided and refer to it in their response
• show all working in calculations and include correct units
• present a logical and succinct response that addresses the question
• review their response to ensure that it addresses the question requirements.

Question 21

In better responses, students were able to:

• outline strategies that could help to prevent the spread of cholera by using the information in the stimulus material and linking how the strategies would prevent this spread
• use structured sentences that linked the strategy to the effect on bacteria, for example, ‘washing hands after handling food so that the bacteria is removed from hands’.

Areas for students to improve include:

• outlining strategies specific to cholera, not just general disease prevention strategies
• ensuring that strategies are linked to their purpose. Not just writing, boil the water, but rather, boil the water to kill the bacteria
• outlining strategies for prevention of disease not the treatment of disease. For example, ‘treating people with antibiotics won’t prevent the spread of cholera, however, vaccinating people and creating herd immunity will prevent the spread of cholera.’

Question 22

In better responses, students were able to:

• identify a pharmaceutical treatment and correctly link the benefit of the treatment to its effect on the disease, for example, ‘antibiotics used for treating bacterial infections linked to inhibiting bacterial growth’
• identify a limitation of a pharmaceutical and correctly link the limitation to its effect on the treatment of a disease, for example, ‘antibiotic resistant bacteria is common, reducing the effectiveness of antibiotics’.

Areas for students to improve include:

• linking the pharmaceutical treatment to the correct pathogen, for example, antibiotics do not treat viruses
• making specific reference to a pharmaceutical and disease such as ‘Antibiotics treat bacterial infections’, rather than a generic reference such as, ‘Pharmaceuticals treat pathogens’
• linking the benefit or limitation specifically to the treatment of the disease, rather than referring to side effects of the treatment
• not confusing antibiotics with antibodies leading to an outline of the immune response
• understanding how antibiotics are impacted by bacterial resistance, ‘bacteria develop a resistance to antibiotics, rendering them ineffective’ rather than ‘the body develops a resistance to the antibiotics’
• understanding the difference between the role of the immune system and the action of pharmaceuticals on infectious disease.

Question 23

In better responses, students were able to:

• identify a point mutation or substitution mutation (a)
• identify a chromosomal mutation as the other type of mutation, as indicated in the syllabus, and link it to an effect of this type of mutation, for example, the number of chromosomes changes (b).

Areas for students to improve include:

• identifying the type of mutation rather than describing the stimulus material, for example, ‘substitution mutation’ not ‘A was replaced with T’ (a)
• not listing mutations such as germ line, somatic mutations or identifying mutagens, for example, UV radiation (a)
• outlining another type of mutation other than base substitution mutation (b)
• understanding that chromosomal mutations affect part of or the whole chromosome, not specific gene sequences (b).

Question 24(a)

In better responses, students were able to:

• fully label the y axis
• accurately and clearly plot point.

Areas for students to improve include:

• using the full grid given with appropriate scale
• dividing the scale evenly and appropriately for the data given in the question.

Question 24(b)

In better responses, students were able to:

• draw an appropriate curve of best fit which reflects all data points
• extrapolate the data to determine the correct year dialysis should commence
• clearly mark the correct year dialysis was required on the graph as instructed in the question; ensuring all working is shown and is relevant to the graph, not the data provided in the table.

Areas for students to improve include:

• doing more than simply connecting the points and knowing how to identify and correctly draw either a line or curve of best fit
• not using the data in the table but recognising the need for extrapolation of the graph.

Question 24(c)

In better responses, students were able to:

• describe the purpose of removing wastes (urea) from the blood
• use key terminology to describe the processes involved in either haemodialysis or peritoneal dialysis including explaining the process of diffusion of materials via a concentration gradient through a semipermeable membrane
• relate these processes of renal dialysis to the correct function of the kidney.

Areas for students to improve include:

• using correct language, for example, diffusion rather than osmosis of urea, urea rather than ammonia, removal of wastes rather than ‘cleans blood’
• understanding of normal function of the kidney in order to be able to relate the loss of this function to the need for dialysis
• showing full understanding of the processes involved in dialysis compared to the actual setting up and social impact of dialysis (which is not relevant to this question).

Question 25(a)

In better responses, students were able to:

• justify their conclusion using relevant quantitative data from the table
• identify that the data was inconclusive and justify this conclusion using the standard deviation and the average given from the table.

Areas for students to improve include:

• analysing quantitative data from the table and using it to support their conclusion
• writing a clear conclusion using data from the table.

Question 25(b)

In better responses, students were able to:

• identify that increasing the number of species would decrease the effect of outliers in the data
• identify good experimental technique.

Areas for students to improve include:

• understanding the impact of changing or improving an experimental design on the aim or hypothesis of an investigation
• understanding that external fertilisation must take place in an aquatic environment and that aquatic animals can also undergo internal fertilisation
• understanding that some organisms that undergo external fertilisation still need to find a mate
• understanding that organisms either fertilise internally or externally but not both.

Question 25(c)

In better responses, students were able to:

• identify an advantage external fertilisation
• clearly link an advantage of external fertilisation with the effect that this has on the species.

Areas for students to improve include:

• their understanding the difference between external fertilisation and asexual reproduction
• understanding that an explanation involves linking a cause with an effect on the species
• identify features of external fertilisation that are advantageous to an organism not just features of external fertilisation.

Question 26

In better responses, students were able to:

• engage with the pedigree chart and explain why the yellow allele is recessive (a)
• explain that both parents are heterozygous for the yellow allele if autosomal inheritance is used resulting in the offspring shown in the pedigree (a)
• explain all possible outcomes of a cross between individuals I and II and how this information could be used to determine whether the inheritance of colour in fish is autosomal or sex-linked (b)
• use Punnet squares with the correct conventions to assist explanations of outcomes of the cross and the determination of autosomal or sex-linked inheritance of colour in fish (b).

Areas for students to improve include:

• using appropriate terminology (a)
• interpreting pedigree charts and relationships between individuals (a)
• using appropriate formats within the response to provide a clear explanation (b)
• increasing understanding of autosomal and sex-linked inheritance (b).

Question 27(a)

Areas for students to improve include:

• clearly identify two features of the methodology that contributed to the validity of the study.

Areas for students to improve include:

• engaging with the stimulus. All appropriate responses were contained within the stimulus text.
• avoiding vague speculation about what may have been controlled within the study but wasn’t stated.

Question 27(b)

In better responses, students were able to:

• argue how specific data trends and points and support and/or refute the hypothesis
• clearly identify the misrepresentation of the data (limited scale of Y-axis) and link this to minimal drop in mortality over the 11 years.

Areas for students to improve include:

• avoid simply describing the data and trends of graphs without linking back to the hypothesis
• ensure a discussion includes points for and/or against.

Question 28

In better responses, students were able to:

• identify that the paired homologous chromosomes in the first diagram of the model were incorrectly drawn (a)
• explain that in a pair of homologous chromosomes, one chromosome is paternal and one is maternal (a)
• explain that at this stage of meiosis where each of the chromosomes have duplicated to form two chromatids, the chromatids should be identical, that is, both chromatids should be either maternal or paternal (a)
• explain how processes in meiosis, such as crossing over, independent assortment, random alignment, random segregation, mutation lead to an increase in genetic variation (b).

Areas for students to improve include:

• outlining the differences between chromosomes and chromatids (a)
• describing the process of replication in the formation of maternal and/or paternal chromatids (a)
• differentiating between independent assortment, random alignment and random segregation (b).

Question 29

In better responses, students were able to:

• describe two mechanisms that can affect the gene pool
• describe how variations within the gene pool can affect populations
• explain how changes to the gene pool can lead to natural selection and drive evolution
• identify that evolution of a species occurs over a long period of time.

Areas for students to improve include:

• understanding that while fertilisation and meiosis brings about variation, they do not add or take away alleles from the gene pool
• describing the main features of the mechanisms that drive changes to the gene pool, including mutation, gene flow and genetic drift
• understanding that evolution does not just occur in a single generation.

Question 30

In better responses, students were able to:

• show a clear understanding of both infectious and non-infectious diseases not just examples of diseases
• outline the processes of at least two different genetic technologies including what happens at the genetic level
• link each genetic technology to the impact it has on the management of the disease
• structure their response clearly and succinctly.

Areas for students to improve include:

• avoiding the use of general statements grouping diseases and/or genetic technologies, be specific
• providing detail to show understanding of the processes at the genetic level and then linking these to the impact of managing the disease
• distinguishing what a genetic technology is from a biotechnology or a generic technology
• clearly outlining when a vaccine is a genetic technology.

Question 31

In better responses, students were able to:

• engage with the data shown in all three graphs (a)
• demonstrate a detailed understanding of all hormones, cells and organs responsible for the regulation of blood glucose levels (a)
• explain the trends in all of the graphs in relation to the negative feedback control of blood glucose
• outline two key differences between blood glucose control and the maintenance of temperature using clear conjunctions (b).

Areas for students to improve include:

• making reference to the data provided in the graphs (a)
• demonstrating a clear understanding of the role of the components involved in blood glucose control. For example, the roles of insulin, glucagon, glycogen, alpha and beta cells, the pancreas and the liver (a)
• clearly linking a difference in blood glucose regulation to an equivalent component in temperature maintenance. For example, an outline of the different control centres, body systems or messages involved (b).

Question 32(a)

In better responses, students were able to:

• determine the two main features out of the six provided in the stimulus to include in their answer
• concisely answer the question
• demonstrate an understanding of transmission in that they identify the bite from the dog, movement through the host and entering the salivary glands of the host as key elements.

Areas for students to improve include:

• understanding that the bite is essential for transmission as saliva alone cannot penetrate the skin
• disregarding or not being distracted by irrelevant parts of the stimulus.

Question 32(b)(i)

In better responses, students were able to:

• use the information from the stimulus diagram 1, namely the presence of short single stranded RNA to then distinguish from other cellular pathogens
• use structural features to distinguish, rather than functional features to address a classification question
• explain, showing cause and effect, why the presence of RNA, instead of DNA makes the virus non-cellular.

Areas for students to improve include:'

• ensuring specificity of responses, for example, 'single stranded RNA' instead of stating  'single stranded'
• understanding that the classification of pathogens is based on structures not processes
• showing a better comprehension of the distinguishing features between eukaryotic, prokaryotic and non-cellular pathogens.

Question 32(b)(ii)

In better responses, students were able to:

• identify that there is both polypeptide synthesis and RNA replication taking place within the cell
• explain in detail the role of RNA polymerase in polypeptide synthesis and RNA replication
• incorporate key aspects of both stimulus diagrams in their answer. This is shown when students outline that the newly produced proteins of L and P are actually more RNA polymerase which is needed to catalyse the RNA replication process
• provide information beyond the stimulus to demonstrate cause and effect for both processes.

Areas for students to improve include:

• relating the response to the stimulus diagram, as stated, instead of a long response on polypeptide synthesis
• incorporating deeper biological understanding into the explanation of the flowchart
• correctly using the terms transcription, translation and replication.

Question 32(c)

In better responses, students were able to:

• refer to the stimulus material, both the graph and, a and b
• not only explain what the graph meant but provide their own knowledge of vaccination (passive and active immunity)
• realise that they need to explain succinctly how antibodies work
• understand the importance of each graph and use this information to explain how PEP prevents the development of rabies.

Areas for students to improve include:

• use stimulus material AND relate their syllabus knowledge to respond to the question
• link the information provided to the explanation of vaccines, immunity and the role of antibodies
• recognise what area of the syllabus the stimulus material is asking them to address
• avoid just describing the graphs provided.