NOS statements and links to the topics in the biology syllabus
What role will NOS play in the final examinations?
In paper 1 there will be at least one question that addresses NOS. In papers 2 and 3, aspects of NOS will be assessed within the context of a particular subject specific topic. Below in blue are the NOS statements that may be addressed. Below each one are examples of where it is referenced in the syllabus providing specific applications and examples of each. They are also references as part of each topic. A word document is available to download at the bottom of this page.
NOS 1.4. This is an exciting and challenging adventure involving much creativity and imagination as well as exacting and detailed thinking and application. Scientists also have to be ready for unplanned, surprising, accidental discoveries. The history of science shows this is a very common occurrence.
1.6 Cell division Serendipity and scientific discoveries—the discovery of cyclins was accidental. (1.4)
D.2 Digestion Serendipity and scientific discoveries—the role of gastric acid in digestion was established by William Beaumont while observing the process of digestion in an open wound caused by gunshot. (1.4)
1.5. Many scientific discoveries have involved flashes of intuition and many have come from speculation or
simple curiosity about particular phenomena.
11.3 HL The kidney and osmoregulation Curiosity about particular phenomena—investigations were carried out to determine how desert animals prevent water loss in their wastes. (1.5)
NOS 1.8. The importance of evidence is a fundamental common understanding. Evidence can be obtained by observation or experiment. It can be gathered by human senses, primarily sight, but much modern science is carried out using instrumentation and sensors that can gather information remotely and automatically in areas that are too small, or too far away, or otherwise beyond human sense perception. Improved instrumentation and new technology have often been the drivers for new discoveries. Observations followed by analysis and deduction led to the Big Bang theory of the origin of the universe and to the theory of evolution by natural selection. In these cases, no controlled experiments were possible. Disciplines such as geology and astronomy rely strongly on collecting data in the field, but all disciplines use observation to collect evidence to some extent. Experimentation in a controlled environment, generally in laboratories, is the other way of obtaining evidence in the form of data, and there are many conventions and understandings as to how this is to be achieved.
1.2 Ultrastructure of cells Developments in scientific research follow improvements in apparatus—the invention of electron microscopes led to greater understanding of cell structure. (1.8)
2.7 DNA replication, transcription and translation Obtaining evidence for scientific theories—Meselson and Stahl obtained evidence for the semi-conservative replication of DNA. (1.8)
3.1 Genes Developments in scientific research follow improvements in technology—gene sequencers are used for the sequencing of genes. (1.8)
3.2 Chromosomes Developments in research follow improvements in techniques—autoradiography was used to establish the length of DNA molecules in chromosomes. (1.8)
3.3 Meiosis Making careful observations—meiosis was discovered by microscope examination of dividing germ-line cells. (1.8)
6.4 Gas exchange Obtain evidence for theories—epidemiological studies have contributed to our understanding of the causes of lung cancer. (1.8)
6.6 Hormones, homeostasis and reproduction Developments in scientific research follow improvements in apparatus—William Harvey was hampered in his observational research into reproduction by lack of equipment. The microscope was invented 17 years after his death. (1.8)
7.1 HL DNA structure and replication Making careful observations—Rosalind Franklin’s X-ray diffraction provided crucial evidence that DNA is a double helix. (1.8)
8.3 HL Photosynthesis Developments in scientific research follow improvements in apparatus—sources of 14C and autoradiography enabled Calvin to elucidate the pathways of carbon fixation. (1.8)
9.2 HL Transport in the phloem of plants Developments in scientific research follow improvements in apparatus—experimental methods for measuring phloem transport rates using aphid stylets and radioactively-labelled carbon dioxide were only possible when radioisotopes became available. (1.8)
9.3 HL Growth in plants Developments in scientific research follow improvements in analysis and deduction—improvements in analytical techniques allowing the detection of trace amounts of substances has led to advances in the understanding of plant hormones and their effect on gene expression. (1.8)
10.1 HL Meiosis Making careful observations—careful observation and record keeping turned up anomalous data that Mendel’s law of independent assortment could not account for Thomas Hunt Morgan developed the notion of linked genes to account for the anomalies. (1.8)
11.2 HL Movement Developments in scientific research follow improvements in apparatus—fluorescent calcium ions have been used to study the cyclic interactions in muscle contraction. (1.8)
D.4 The heart Developments in scientific research followed improvements in apparatus or instrumentation—the invention of the stethoscope led to improved knowledge of the
workings of the heart. (1.8)
NOS 1.9. This evidence is used to develop theories, generalize from data to form laws and propose hypotheses. These theories and hypotheses are used to make predictions that can be tested. In this way theories can be supported or opposed and can be modified or replaced by new theories.
1.3 Membrane structure Falsification of theories with one theory being superseded by another—evidence falsified the Davson-Danielli model. (1.9)
1.5 The origin of cells Testing the general principles that underlie the natural world—the principle that cells only come from pre-existing cells needs to be verified. (1.9)
2.1 Molecules to metabolism Falsification of theories—the artificial synthesis of urea helped to falsify vitalism. (1.9)
5.4 Cladistics Falsification of theories with one theory being superseded by another—plant families have been reclassified as a result of evidence from cladistics. (1.9)
6.2 The blood system Theories are regarded as uncertain—William Harvey overturned theories developed by the ancient Greek philosopher Galen on movement of blood in the body. (1.9)
D.1 Human nutrition Falsification of theories with one theory being superseded by another—scurvy was thought to be specific to humans, because attempts to induce the symptoms in laboratory rats and mice were entirely unsuccessful. (1.9)
NOS 1.10. Models, some simple, some very complex, based on theoretical understanding, are developed to
explain processes that may not be observable. Computer-based mathematical models are used to
make testable predictions, which can be especially useful when experimentation is not possible.
Models tested against experiments or data from observations may prove inadequate, in which case
they may be modified or replaced by new models.
2.6 Structure of DNA and RNA Using models as representation of the real world—Crick and Watson used model making to discover the structure of DNA. (1.10)
6.1 Digestion and absorption Use models as representations of the real world—dialysis tubing can be used to model absorption in the intestine. (1.10)
9.1 HL Transport in the xylem of plants Use models as representations of the real world—mechanisms involved in water transport in the xylem can be investigated using apparatus and materials that show similarities in structure to plant tissues. (1.10)
NOS 1.11. The outcomes of experiments, the insights provided by modelling and observations of the natural world may be used as further evidence for a claim.
1.3 Membrane structure Using models as representations of the real world—there are alternative models of membrane structure. (1.11)
NOS 2.1. Theories, laws and hypotheses are concepts used by scientists. Though these concepts are connected,
there is no progression from one to the other. These words have a special meaning in science and it is
important to distinguish these from their everyday use.
5.2 Natural selection Use theories to explain natural phenomena—the theory of evolution by natural selection can explain the development of antibiotic resistance in bacteria. (2.1)
NOS 2.2. Theories are themselves integrated, comprehensive models of how the universe, or parts of it, work.
A theory can incorporate facts and laws and tested hypotheses. Predictions can be made from the
theories and these can be tested in experiments or by careful observations. Examples are the germ
theory of disease or atomic theory.
2.2 Water Use theories to explain natural phenomena—the theory that hydrogen bonds form between water molecules explains the properties of water. (2.2)
4.2 Energy flow Use theories to explain natural phenomena—the concept of energy flow explains the limited length of food chains. (2.2)
NOS 2.3. Theories generally accommodate the assumptions and premises of other theories, creating
a consistent understanding across a range of phenomena and disciplines. Occasionally, however,
a new theory will radically change how essential concepts are understood or framed, impacting
other theories and causing what is sometimes called a “paradigm shift” in science. One of the most
famous paradigm shifts in science occurred when our idea of time changed from an absolute frame of
reference to an observer-dependent frame of reference within Einstein’s theory of relativity. Darwin’s
theory of evolution by natural selection also changed our understanding of life on Earth.
8.2 Cell respiration HL Paradigm shift—the chemiosmotic theory led to a paradigm shift in the field of bioenergetics. (2.3)
9.4 HL Reproduction in plants Paradigm shift—more than 85% of the world’s 250,000 species of flowering plant depend on pollinators for reproduction. This knowledge has led to protecting entire ecosystems rather than individual species. (2.3)
NOS 3.1. Data is the lifeblood of scientists and may be qualitative or quantitative. It can be obtained purely from
observations or from specifically designed experiments, remotely using electronic sensors or by direct
measurement. The best data for making accurate and precise descriptions and predictions is often
quantitative and amenable to mathematical analysis. Scientists analyse data and look for patterns,
trends and discrepancies, attempting to discover relationships and establish causal links. This is not
always possible, so identifying and classifying observations and artefacts (eg types of galaxies or
fossils) is still an important aspect of scientific work.
1.1 Introduction to cells Looking for trends and discrepancies—although most organisms conform to cell theory, there are exceptions. (3.1)
1.4 Membrane transport Experimental design—accurate quantitative measurement in osmosis experiments are essential. (3.1)
2.4 Proteins Looking for patterns, trends and discrepancies—most but not all organisms assemble proteins from the same amino acids. (3.1)
2.9 Photosynthesis Experimental design—controlling relevant variables in photosynthesis experiments is essential. (3.1)
4.1 Species, communities and ecosystems Looking for patterns, trends and discrepancies—plants and algae are mostly autotrophic but some are not. (3.1)
4.3 Carbon cycling Making accurate, quantitative measurements—it is important to obtain reliable data on the concentration of carbon dioxide and methane in the atmosphere. (3.1)
5.1 Evidence for evolution Looking for patterns, trends and discrepancies—there are common features in the bone structure of vertebrate limbs despite their varied use. (3.1)
7.2 Transcription and gene expression Looking for patterns, trends and discrepancies—there is mounting evidence that the environment can trigger heritable changes in epigenetic factors. (3.1)
10.2 HL Inheritance Looking for patterns, trends and discrepancies—Mendel used observations of the natural world to find and explain patterns and trends. Since then, scientists have looked for discrepancies and asked questions based on further observations to show exceptions to the rules. For example, Morgan discovered non-Mendelian ratios in his experiments with Drosophila. (3.1)
10.3 HL Gene pools and speciation Looking for patterns, trends and discrepancies—patterns of chromosome number in some genera can be explained by speciation due to polyploidy. (3.1)
NOS 3.2. Taking repeated measurements and large numbers of readings can improve reliability in data
collection. Data can be presented in a variety of formats such as linear and logarithmic graphs that can
be analysed for, say, direct or inverse proportion or for power relationships.
2.5 Enzymes Experimental design—accurate, quantitative measurements in enzyme experiments require replicates to ensure reliability. (3.2)
3.4 Inheritance Making quantitative measurements with replicates to ensure reliability. Mendel’s genetic crosses with pea plants generated numerical data. (3.2)
NOS 3.7. In recent decades, the growth in computing power, sensor technology and networks has allowed
scientists to collect large amounts of data. Streams of data are downloaded continuously from many
sources such as remote sensing satellites and space probes and large amounts of data are generated
in gene sequencing machines. Experiments in CERN’s Large Hadron Collider regularly produce 23
petabytes of data per second, which is equivalent to 13.3 years of high definition TV content per
second.
7.3 Translation Developments in scientific research follow improvements in computing—the use of computers has enabled scientists to make advances in bioinformatics applications such as locating genes within genomes and identifying conserved sequences. (3.7)
NOS 3.8. Research involves analysing large amounts of this data, stored in databases, looking for patterns
and unique events. This has to be done using software which is generally written by the scientists
involved. The data and the software may not be published with the scientific results but would be
made generally available to other researchers.
8.1 Metabolism Developments in scientific research follow improvements in computing—developments in bioinformatics, such as the interrogation of databases, have facilitated research into metabolic pathways. (3.8)
4.3. As well as collaborating on the exchange of results, scientists work on a daily basis in collaborative
groups on a small and large scale within and between disciplines, laboratories, organizations and
countries, facilitated even more by virtual communication. Examples of large-scale collaboration
include:
–– The Manhattan project, the aim of which was to build and test an atomic bomb. It eventually
employed more than 130,000 people and resulted in the creation of multiple production and
research sites that operated in secret, culminating in the dropping of two atomic bombs on
Hiroshima and Nagasaki.
–– The Human Genome Project (HGP), which was an international scientific research project set up
to map the human genome. The $3-billion project beginning in 1990 produced a draft of the
genome in 2000. The sequence of the DNA is stored in databases available to anyone on the
internet.
–– The IPCC (Intergovernmental Panel on Climate Change), organized under the auspices of
The United Nations, is officially composed of about 2,500 scientists. They produce reports
summarizing the work of many more scientists from all around the world.
–– CERN, the European Organization for Nuclear Research, an international organization set up
in 1954, is the world’s largest particle physics laboratory. The laboratory, situated in Geneva,
employs about 2,400 people and shares results with 10,000 scientists and engineers covering
over 100 nationalities from 600 or more universities and research facilities.
All the above examples are controversial to some degree and have aroused emotions among scientists
and the public.
5.3 Classification of biodiversity Cooperation and collaboration between groups of scientists—scientists use the binomial system to identify a species rather than the many different local names. (4.3)
6.5 Neurons and synapses Cooperation and collaboration between groups of scientists—biologists are contributing to research into memory and learning. (4.3)
D.5 Hormones and metabolism Cooperation and collaboration between groups of scientists—the International Council for the Control of Iodine Deficiency Disorders includes a number of scientists who work to eliminate the harm done by iodine deficiency. (4.3)
NOS 4.5. Scientists often work in areas, or produce findings, that have significant ethical and political implications. These areas include cloning, genetic engineering of food and organisms, stem cell and reproductive technologies, nuclear power, weapons development (nuclear, chemical and biological), transplantation of tissue and organs and in areas that involve testing on animals (see IB animal experimentation policy). There are also questions involving intellectual property rights and the free exchange of information that may impact significantly on a society. Science is undertaken in universities, commercial companies, government organizations, defence agencies and international organizations. Questions of patents and intellectual property rights arise when work is done in a protected environment.
1.1 Introduction to cells Ethical implications of research—research involving stem cells is growing in importance and raises ethical issues. (4.5)
2.8 Cell respiration Assessing the ethics of scientific research—the use of invertebrates in respirometer experiments has ethical implications. (4.5)
11.1 HL Antibody production and vaccination Consider ethical implications of research—Jenner tested his vaccine for smallpox on a child. (4.5)
NOS 4.8. Science has been used to solve many problems and improve man’s lot, but it has also been used in
morally questionable ways and in ways that inadvertently caused problems. Advances in sanitation,
clean water supplies and hygiene led to significant decreases in death rates but without compensating
decreases in birth rates this led to huge population increases with all the problems of resources,
energy and food supplies that entails. Ethical discussions, risk-benefit analyses, risk assessment and
the precautionary principle are all parts of the scientific way of addressing the common good.
3.5 Genetic modification and biotechnology Assessing risks associated with scientific research—scientists attempt to assess the risks associated with genetically modified crops or livestock. (4.8)
6.3 Defence against infectious disease Risks associated with scientific research—Florey and Chain’s tests on the safety of penicillin would not be compliant with current protocol on testing. (4.8)
11.4 HL Sexual reproduction Assessing risks and benefits associated with scientific research—the risks to human male fertility were not adequately assessed before steroids related to progesterone and estrogen were released into the environment as a result of the use of the female contraceptive pill. (4.8)
NOS 5.1. An understanding of the nature of science is vital when society needs to make decisions involving
scientific findings and issues. How does the public judge? It may not be possible to make judgments
based on the public’s direct understanding of a science, but important questions can be asked about
whether scientific processes were followed and scientists have a role in answering such questions.
D.6 Transport of respiratory gases Scientists have a role in informing the public—scientific research has led to a change in public perception of smoking. (5.1)
NOS 5.2. As experts in their particular fields, scientists are well placed to explain to the public their issues and
findings. Outside their specializations, they may be no more qualified than ordinary citizens to advise
others on scientific issues, although their understanding of the processes of science can help them to
make personal decisions and to educate the public as to whether claims are scientifically credible.
2.3 Carbohydrates and lipids Evaluating claims—health claims made about lipids in diets need to be assessed. (5.2)
4.4 Climate change Assessing claims—assessment of the claims that human activities are producing climate change. (5.2)
D.3 Functions of the liver Educating the public on scientific claims—scientific studies have shown that high-density lipoprotein could be considered “good” cholesterol. (5.2)