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5. 2011 HSC Notes from the Marking Centre — Biology

2011 HSC Notes from the Marking Centre – Biology

Contents

• Introduction
• Section I – Core
• Section II – Options

Introduction

This document has been produced for the teachers and candidates of the Stage 6 course in Biology. It contains comments on candidate responses to the 2011 Higher School Certificate examination, indicating the quality of the responses and highlighting their relative strengths and weaknesses.

This document should be read along with the relevant syllabus, the 2011 Higher School Certificate examination, the marking guidelines and other support documents developed by the Board of Studies to assist in the teaching and learning of Biology.

General comments

Teachers and candidates should be aware that examiners may ask questions that address the syllabus outcomes in a manner that requires candidates to respond by integrating their knowledge, understanding and skills developed through studying the course and including the prescribed focus areas. It is important to understand that the Preliminary course is assumed knowledge for the HSC course.

Candidates need to be aware that the marks allocated to the question and the answer space (where this is provided on the examination paper) are guides to the length of the required response. A longer response will not in itself lead to higher marks. Writing in excess of the space allocated may reduce the time available for answering other questions.

Candidates need to be familiar with the Board’s Glossary of Key Words Glossary of Key Words, which contains some terms commonly used in examination questions. However, candidates should also be aware that not all questions will start with or contain one of the key words from the glossary. Questions such as ‘how?’, ‘why?’ or ‘to what extent?’ may be asked or verbs may be used that are not included in the glossary, such as ‘design’, ‘translate’ or ‘list’.

Teachers and candidates are reminded that the mandatory skills content in Module 9.1 is examinable in both the core and option questions and that all objectives and outcomes, including the Prescribed Focus Areas, are integral to the Stage 6 Biology Course.

Candidates are required to attempt only one question in Section II and are strongly advised to answer the option they have studied in class.

Section I – Core

Part B

Specific comments

Question 21

1. In better responses, candidates correctly named two methods used in the treatment of drinking water that would reduce the risk of infection.
2. In better responses, candidates related the methods outlined to the reduced risk of infection. In weaker responses, candidates provided a description of the methods only.

Question 22

1. In better responses, candidates correctly identified the aim of the experiment as showing the effect of pH on enzyme activity.  
2. In better responses, candidates provided characteristics of two changes to the experiment that would improve the validity. In many of the weaker responses, candidates did not differentiate between validity and reliability.
3. In better responses, candidates correctly predicted the nature of the solutions based on the pH values.

Question 23

In better responses, candidates thoroughly described the quality of collaboration and communication between at least three correctly named scientists, and clearly related the effect of this collaboration and communication on their progress in determining the structure of DNA. In weaker responses, candidates made general statements about collaboration and communication between scientists. Often the scientists identified were not involved in determining the structure of DNA.

Question 24

1. In better responses, candidates identified a viral disease controlled by the use of a vaccine. In weaker responses, candidates identified viral diseases not controlled by the use of a vaccine or a disease caused by a pathogen other than a virus.
2. 1. In better responses, candidates outlined how a feature of the viral vaccine – prepared as shown in the flowchart – initiated a named immune response. In weaker responses, candidates failed to name an immune response or made a general statement about the body’s response to a vaccine.
   2. In better responses, candidates explained one correct procedure from the flowchart that would ensure the safety of the prepared vaccine. Weaker responses often only identified a correct procedure in the flowchart.

Question 25

1. In the majority of responses, candidates correctly identified the two processes in the nephron.
2. In better responses, candidates identified the process of active transport in the nephron.
3. In better responses, candidates clearly outlined the effect of aldosterone on the reabsorption of salt and water. Candidates who wrote weaker responses were unable to link the movement of salt with reabsorption of water. Many responses confused aldosterone with ADH and its effect on water reabsorption.

Question 26

1. In better responses, candidates identified similarities and differences using either generalised statements or specific examples from the information contained in both graphs. Weaker responses referred to the presentation of the graph rather than the information contained in the graphs.
2. In better responses, candidates provided reasons in favour of the two nominated data types to evaluate the effectiveness of the global polio vaccination program. Many responses gave two new data types without providing a recommendation. Data types were often confused with the presentation of data, eg line graphs.

Question 27

In better responses, candidates clearly outlined four features relevant to an epidemiological study. Candidates outlined features such as large sample size, data collection, analysis and a cause and effect relationship related to the non-infectious disease in the aged care homes.In weaker responses, candidates included an extensive list of data to be collected rather than addressing the main features of an epidemiological study.

Question 28

1. In better responses, candidates recognised that the activation of a gene in the stem cell produces new skin cells to repair the broken skin.
   
   

   Most candidates recognised that stem cells would repair the broken skin, but did not relate this to the switching on of a gene.

2. In better responses, candidates correctly interpreted the stimulus material and explained two improvements of the new artificial blood made from skin stem cells. These candidates clearly linked one improvement in the performance of the new artificial blood compared to existing forms of artificial blood.
In weaker responses candidates focused on the advantages of the existing forms of artificial blood or related the improvements to donated blood, rather than the new artificial blood made from skin stem cells.

Question 29

In better responses, candidates provided the correct dependent and independent variables and control. They also identified the safety precautions and risks related to their safe work practices.

Question 30

1. In better responses, candidates identified both technology X as a temperature probe and technology Y as a data logger. Some candidates referred to technology Y as a USB link or USB probe. These were acceptable answers.
2. In better responses, candidates presented an argument related to the experimental design to justify the conclusion as being invalid.
   
   In weaker responses, candidates did not present a clear argument and/or related their answer to the data from the graph.

Question 31

In better responses, candidates linked the answer to their relevant knowledge of the advances in antibiotic development.

In weaker responses, candidates included information from a range of non-relevant biological advancements.

Section II – Options

Question 32 – Communication

1. 1. In better responses, candidates correctly identified structure A as an axon and structure B as a dendrite.
   2. In better responses, candidates recognised the role of the dendrite.
2. In better responses, candidates drew an appropriate graph and related the stimulus, membrane potential and threshold to the formation (or not) of the action potential.
   
   In most of the weaker responses, candidates did not indicate the stimulus on their graph.
3. 1. In better responses, candidates named at least two functions of the cornea.
   2. In the better responses, candidates identified the problem associated with myopia and described how LASIK could correct the defect.
      
      In weaker responses, candidates did not relate myopia and LASIK and/or include a re-wording of the stimulus material.
4. In better responses, candidates included correct mammalian frequency ranges and presented appropriate reasons for the differences.
5. In the better responses, candidates described the anatomy and function of the human ear and the role of the brain, as well as an understanding of how cochlea implant technology works.
   
   In weaker responses, candidates presented a simple description of the anatomy of the ear.

Question 33 – Biotechnology

1. 1. In better responses, candidates correctly identified structure A as a primer and structure B as a polymerase.
   2. In better responses, candidates recognised the process as polymerase chain reaction (PCR).
      
      In the weaker responses, candidates incorrectly identified this process as protein synthesis or DNA replication.
2. In better responses, candidates drew an appropriate diagram that correctly identified the sites of both transcription and translation, and accounted for the different products.
3. 1. In better responses, candidates distinguished between qualitative and quantitative data, and identified appropriate examples from the presented text.
   2. In better responses, candidates defined biotechnology and presented an argument related to the outcome of the ants’ activity.
4. In better responses, candidates defined recombinant DNA technology, stated its purpose and clearly related this to the risks and benefits to society.
   
   In weaker responses, candidates provided risks and/or benefits to society only.
5. In the better responses, candidates clearly related the use of a range of technologies to the production of enzymes.

Question 34 – Genetics: the code broken?

1. 1. In better responses, candidates correctly identified Mutation 1 as a base substitution and Mutation 2 as a deletion.
   2. In better responses, candidates identified that there would be no change to the polypeptide. Candidates are reminded that it is important to understand the difference between a base, amino acid and polypeptide.
2. In better responses, candidates used correctly constructed Punnett squares for both ABO blood groups and Rhesus factors to identify the offspring with different genotypes and phenotypes to the parents.
   
   In weaker responses, candidates tried to combine the ABO and Rhesus factors into one Punnett square or included only two of the three ABO blood groups.
3. 1. In better responses, candidates provided correct features of both selective breeding and cloning.
   2. In better responses, candidates provided an argument related to the scientist’s claim referring to both selective breeding and cloning.
4. In better responses, candidates identified the methods used in both traditional inheritance studies and the Human Genome Project and provided a comparison in the locating of harmful genes.
   
   In weaker responses, candidates provided a description of traditional inheritance studies and/or the Human Genome Project only.
5. In better responses, candidates clearly identified the application of a range of technologies to the relationships between the two species.
   
   In weaker responses, candidates were limited to a discussion of one or two technologies and/or did not indicate how they could be applied to identifying the relationship between the two species.

Question 35 – The human story

1. 1. In better responses, candidates correctly identified the oldest rock layers as C and F and the youngest rock layer as A.
   2. In better responses, candidates identified the relative dating technique as stratigraphy.
2. In better responses, candidates provided well-constructed cladograms containing hominids of the same genus which provided two clear alternate evolutionary pathways.
   
   In weaker responses, candidates provided only one evolutionary relationship and/or included hominids from different genuses.
3. 1. In better responses, candidates identified two pieces of appropriate data from the source.
   2. In better responses, candidates provided an argument for the validity of Homo floresiensis as a separate species related to relevant pieces of information from the source material.
4. 1. In better responses, candidates correctly discussed mechanisms of evolution restricted to early and modern members of the species Homo sapiens.
      
      In weaker responses, candidates incorrectly included other members of the genus Homo.
   2. In better responses, candidates related the greater genetic diversity of human populations in Africa to both the increased time for evolution and relatively recent migrations to other continents.
5. In the better responses, candidates clearly identified the application of a range of technologies to testing the hypothesis.
   
   In weaker responses, candidates were limited to a discussion of one or two technologies and/or did not indicate how they could be applied to the hypothesis.

Question 36 – Biochemistry

1. 1. In better responses, candidates correctly identified the pathway as the Calvin Cycle.
   2. In better responses, candidates correctly identified molecule A as carbon dioxide and molecule B as glyceraldehyde phosphate.
2. In better responses, candidates drew an appropriate diagram that correctly identified the sites of light absorption and provided characteristics and features of the photosystems.
3. In better responses, candidates correctly related the use of the isotopes to their respective half-lives.
4. In the better responses, candidates correctly identified the ideas proposed by earlier scientists and related these discoveries to Mayer’s conclusion on photosynthesis.
5. In the better responses, candidates clearly identified the application of a range of technologies to perform the isolation and characterisation of chlorophyll E.