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6. 2009 HSC Notes from the Marking Centre – Biology

2009 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 2009 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 2009 Higher School Certificate examination, the marking guidelines and other support documents which have been developed by the Board of Studies to assist in the teaching and learning of Biology.

Teachers and students are advised that, in December 2008, the Board of Studies approved changes to the examination specifications and assessment requirements for a number of courses. These changes will be implemented for the 2010 HSC cohort. Information on a course-by-course basis is available on the Board’s website.

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 mark allocated to the question and the answer space (where this is provided on the examination paper), are a guide to the length of the required response. A longer response will not in itself lead to higher marks. Writing far beyond the indicated space may reduce the time available for answering other questions.

Candidates need to be familiar with the Board’s 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 which are not included in the glossary, such as ‘design’, ‘translate’ or ‘list’.

Teachers and candidates are reminded that 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.

In Section II, the Option question is divided into a number of parts. Candidates should clearly label each part of the question when writing in their answer booklets. In part (e) of the 2009 Option questions, the best responses presented ideas coherently and included the correct use of scientific principles and ideas. Many candidates wrote an assortment of information that was not relevant to the question. Some responses showed evidence of rote learning of an anticipated answer based on a single source. These responses did not address the syllabus content and/or outcomes being assessed and hence did not score full marks. Candidates are required to attempt only one question in Section II, and they are strongly advised to answer the option they have studied in class.

Section I – Core

Part B

Specific comments

Question 16

In the better responses, candidates demonstrated a good understanding of the distinguishing characteristics of the pathogen types. Weaker responses only named examples of diseases.

Question 17

1. Better responses constructed pedigrees which included a suitable key indicating male and female and those affected by the condition.
2. In the better responses, candidates provided a reason for the use of diagrams in analysing data.
3. Better responses provided a clear judgement about the validity of the statement provided. In the weaker responses, the assessment was incorrect or presented no supporting information.

Question 18

In the better responses, candidates related the explained cleanliness measures to the impacts on pathogens and prevention of the spread of the disease. Weaker responses identified cleanliness practices only.

Question 19

In the better responses, candidates drew a correct diagram and identified regions and processes. Weaker responses demonstrated limited understanding of kidney function, or included diagrams of a nephron.

Question 20

1. Better responses clearly demonstrated an understanding of scientific method as applied to a first-hand investigation involving selection of specimens, identification of pathogens and recording of information.
2. In the better responses, candidates identified both a risk and precaution related to the investigation.

Question 21

1. Better responses demonstrated good understanding of dependent and independent variables and presented a clear graph of the data.
2. In the better responses, candidates correctly inferred the relationship between the growth of wheat and temperature from the graph they had drawn.

Question 22

Better responses provided a correctly drawn table and correctly identified three types of T-lymphocytes and their roles. Weaker responses did not identify T-lymphocyte roles or did not present the information in a table.

Question 23

1. The better responses explained how the widespread use of the technology has had a impact on genetic changes in the population.
2. Better responses related the use of reproductive technology to evolutionary changes.

Question 24

1. Better responses correctly identified dependent and independent variables in an experimental investigation.
2. Better responses correctly named the nervous system as being responsible for monitoring and responding to external temperature changes.
3. In the better responses, candidates demonstrated a clear understanding of the steps in a negative feedback mechanism and represented this as a correctly labelled model, outlining responses to both increased and decreased temperature. Weaker explanations outlined responses to only one of the temperature changes or discussed aspects of body temperature regulation in general terms.

Question 25

1. Better responses correctly named two defence adaptations.
2. In the better responses, candidates identified that antibiotics were used to treat a bacterial infection.

Question 26

Better responses correctly described the processes of both enantiostasis and homeostasis and related the processes to the maintenance of metabolic functions. In the weaker responses, candidates only gave examples of enantiostasis and/or homeostasis.

Question 27

In the better responses, candidates demonstrated a clear understanding of how both genetics and the environment can affect the phenotype, and included appropriate examples in each case.

Section II – Options

Question 28 – Communication

1. In better responses, candidates drew an accurate diagram of the eye, correctly labelling three refractive sites. Weaker responses demonstrated limited understanding of refraction, commonly including structures such as the retina, conjunctiva and the pupil as refractive sites.
2. 1. In many of the better responses, candidates outlined one of the technologies related to the treatment of cataracts.
   2. In the better responses, candidates clearly identified the implications for society of the technology identified in part (i). Weaker responses included only simple statements, such as ‘people can now see’ or ‘less people are blind’, rather than implications for society.
3. In the better responses, candidates demonstrated a clear understanding of the all-or-nothing nature of the action potential. These responses also described the relationship between stimulus intensity, threshold and an action potential. Weaker responses only interpreted the graph, identifying which stimuli generated an action potential.
4. 1. Better responses clearly identified the role of accommodation in focusing clearly on objects at different distances.
   2. Better responses described models which emphasised the relative position of the lens and retina and clearly related this model to the functions of various structures in the eye involved in accommodation. Weaker responses addressed the use of lenses in the correction of vision.
5. In better responses, candidates demonstrated a thorough understanding of both the hearing mechanism and the technology to overcome hearing difficulty clearly linking them. Weaker responses did not describe specific hearing difficulties, instead using general terms such as partially or profoundly deaf instead.

Question 29 – Biotechnology

1. 1. Better responses mentioned restriction enzyme or gave a specific example.
   2. In better responses, candidates made a clear link between ligases joining foreign and host DNA. Weaker responses confused ligases with restriction enzymes and outlined how they cut DNA into pieces.
2. 2. In better responses, candidates provided relevant features and characteristics of a named scientific discovery that has led to expansion of fermentation since the 18th century. Weaker responses did not distinguish between the 18th century and ancient times and/or confused bacteria with yeast.
3. 1. Better responses clearly stated two types of RNA. Some weaker responses identified or confused A,T, G and C with types of RNA and tRNA but then named them incorrectly.
   2. Better responses included identification of the relevant RNA at each location with an appropriate description. These descriptions provided detail of the process of protein synthesis. Weaker responses confused protein synthesis with DNA replication.
4. 1. Better responses clearly and logically describe a first-hand investigation that they had performed to extract DNA.
   2. Better responses clearly identified features of the extracted DNA.
5. Better responses explained two applications of modern biotechnology. They demonstrated a thorough knowledge and understanding of the processes and products of the applications.

Question 30 – Genetics: the code broken?

1. 1. The better responses correctly identified the three alleles required. Weaker responses provided genotypes or blood group names.
2. 1. Weaker responses incorrectly referred to gene cloning.
   2. Most candidates correctly described a benefit of cloning but a significant number of responses did not describe their example from part (i).
3. Better responses demonstrated a thorough knowledge of the correct biological terminology associated with protein synthesis and described in a logical sequence the processes occurring at each location. Weaker responses used incorrect biological terms: for example, they confused translocation with translation, or stated that thymine changes into uracil.
4. Some weaker responses described linkage maps, Punnett squares and sex linkage, without describing a model. Some were contradictory, stating that genes close together on a chromosome were linked, whilst those further apart were not linked.
5. Weaker responses did not provide specific information about the mutation and/or the method of gene therapy for their nominated disease.

Question 31 – The human story

1. Better responses correctly identified the classification levels and provided a feature that was unique to that level. Weaker responses did not understand the classification levels and/or provided features that were common to mammals.
2. 1. Better responses named a specific method for relative or absolute dating.
   2. Better responses outlined two or more problems associated with relying on the fossil record to interpret the past, providing a clear outline of the problem. Weaker responses identified a problem or outlined concerns that scientists were not able to identify what the fossilised organisms ate or the way they behaved.
3. Better responses provided features of more than one piece of evidence to support both the ‘Out of Africa’ and the ‘Multiregional’ theories. Some weaker responses provided evidence for the ‘Multiregional’ theory. Weaker responses described the diagram rather than providing supporting evidence, or named a piece of evidence for one of the theories.
4. 1. Weaker responses named ‘mammals’ and ‘primates’ as their examples of species, or else mixed up the genus names of Homo and Australopithecus.
   2. Better responses clearly outlined the differences and similarities between the species named in part (i). These responses were often presented in a table. Weaker responses incorrectly compared their species to Homo sapiens, or outlined similarities OR differences. Some weaker responses provided a list of features that could be compared.
5. Better responses described appropriate biological evidence and how it is used to provide information about human evolution. Weaker responses correctly provided characteristics of the evidence but did not provide information on how it has been used to improve our understanding of human evolution. Some weaker responses described evidence related to fossils or cultural evolution.

Question 32 – Biochemistry

1. Better responses identified that the level of greenhouses gases like carbon dioxide could be reduced through photosynthesis in plants to produce oxygen and glucose. Weaker responses named photosynthesis as the process, or carbon dioxide as a greenhouse gas, or oxygen as a product of photosynthesis, but did not link them.
2. 1. Better responses correctly named a scientist, such as Joseph Priestly, Jan Ingenhousz or Stephen Hales who made a significant contribution to the discovery that plants produce oxygen.
   2. Better responses clearly provided features of the experiments completed by the scientist named in (i) to demonstrate that plants were able to produce oxygen. Weaker responses recalled other experiments not related to the scientist or experiments unrelated to demonstrating that plants produce oxygen.
3. 1. Better responses identified the location of DNA in the chloroplasts as location 2 and named it as the stroma. Weaker responses identified the location as 2 but did not name this site correctly. Some weaker responses identified the location of DNA as the nucleus.
   2. Better responses identified location 3 as the stroma lamellae and location 5 as the grana thylakoids. These responses provided features and characteristics of the chemical reactions occurring in the Light Reaction and identified that the PSII reaction centre is located mainly in the grana and the PSI enzymes producing ATP are found almost exclusively in the stroma. Weaker responses identified that this was the site of photosynthesis.
4. Better responses provided features and characteristics of at least two laboratory techniques such as homogenisation, chromatography (paper chromatography, column chromatography) spectrophotometry and autoradiography to isolate and identify the nature and location of plant pigments. Weaker responses simply described the use of light microscopes to determine the location and nature of plant pigments.
5. Better responses related aspects of earlier research, which proposed the mechanisms of photosynthesis and then linked research with isotopes, which occurred later in history to confirm their hypothesis. Specific reference was made to the work of Kamen and Ruben with ¹⁸O and ¹⁴C and the work of Calvin in defining the chemical processes of the Dark Reaction using ¹⁴C. Weaker responses provided general comments on how the use of isotopes could identify specific locations of chemicals in the plant, but did not name any of the scientists responsible for the work or the isotopes used, and did not link the use of recent work to earlier discoveries.

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