IB Biology: Sortable Syllabus
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TopicLevelCodeCommand termAssessment StatementObj. NotesTOKTOK ConnectionAimsConnection to the aims
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1.1Core1.1.1StateState that error bars are a graphical representation of the variability of data.1Error bars can be used to show either the range of the data or the standard deviation.
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1.1Core1.1.2CalculateCalculate the mean and standard deviation of a set of values.2Students should specify the standard deviation (s), not the population standard deviation. Students will not be expected to know the formulas for calculating these statistics. They will be expected to use the standard deviation function of a graphic display or scientific calculator.Aim7Aim 7: Students could also be taught how to calculate standard deviation using a spreadsheet computer program.
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1.1Core1.1.3StateState that the term standard deviation is used to summarize the spread of values around the mean, and that 68% of the values fall within one standard deviation of the mean.1For normally distributed data, about 68% of all values lie within ±1 standard deviation (s or σ) of the mean. This rises to about 95% for ±2 standard deviations.
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1.1Core1.1.4ExplainExplain how the standard deviation is useful for comparing the means and the spread of data between two or more samples.3A small standard deviation indicates that the data is clustered closely around the mean value. Conversely, a large standard deviation indicates a wider spread around the mean.
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1.1Core1.1.5DeduceDeduce the significance of the difference between two sets of data using calculated values for t and the appropriate tables.3For the t-test to be applied, the data must have a normal distribution and a sample size of at least 10. The t-test can be used to compare two sets of data and measure the amount of overlap. Students will not be expected to calculate values of t. Only a two-tailed, unpaired t-test is expected.TOKTOK: The scientific community defines an objective standard by which claims about data can be made.Aim7Aim 7: While students are not expected to calculate a value for the t-test, students could be shown how to calculate such values using a spreadsheet program or the graphic display calculator.
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1.1Core1.1.6ExplainExplain that the existence of a correlation does not establish that there is a causal relationship between two variables.3Aim7Aim 7: While calculations of such values are not expected, students who want to use r and r2 values in their practical work could be shown how to determine such values using a spreadsheet program.
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2.1Core2.1.1OutlineOutline the cell theory.2Include the following.Living organisms are composed of cells. Cells come from pre-existing cells. Cells are the smallest units of life.
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2.1Core2.1.2DiscussDiscuss the evidence for the cell theory.3TOK: The nature of scientific theories could be introduced here: the accumulation of evidence that allows a hypothesis to become a theory; whether a theory should be abandoned when there is evidence that it does not offer a full explanation; and what evidence is needed for a theory to be adopted or rejected.
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2.1Core2.1.3StateState that unicellular organisms carry out all the functions of life.1Include metabolism, response, homeostasis, growth, reproduction and nutrition.
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2.1Core2.1.4CompareCompare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI unit.3Appreciation of relative size is required, such as molecules (1 nm), thickness of membranes (10 nm), viruses (100 nm), bacteria (1 µm), organelles (up to 10 µm), and most cells (up to 100 µm). The three-dimensional nature/shape of cells should be emphasized. TOKTOK: All the biological entities in the above list are beyond our ability to perceive directly. They must be observed through the use of technology such as the light microscope and the electron microscope. Is there any distinction to be drawn between knowledge claims dependent upon observations made directly with the senses and knowledge claims dependent upon observations assisted by technology?
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2.1Core2.1.5CalculateCalculate the linear magnification of drawings and the actual size of specimens in images of known magnification.2Magnification could be stated (for example, ×250) or indicated by means of a scale bar, for example. Aim7Aim 7: The size of objects in digital images of microscope fields could be analysed using graticule baselines and image-processing software.
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2.1Core2.1.6ExplainExplain the importance of the surface area to volume ratio as a factor limiting cell size.3Mention the concept that the rate of heat production/waste production/resource consumption of a cell is a function of its volume, whereas the rate of exchange of materials and energy (heat) is a function of its surface area. Simple mathematical models involving cubes and the changes in the ratio that occur as the sides increase by one unit could be compared. Aim7Aim 7: Data logging could be carried out to measure changes in conductivity in distilled water as salt diffuses out of salt–agar cubes of different dimensions.
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2.1Core2.1.7StateState that multicellular organisms show emergent properties.1Emergent properties arise from the interaction of component parts: the whole is greater than the sum of its parts.TOKTOK: The concept of emergent properties has many implications in biology, and this is an opportunity to introduce them. Life itself can be viewed as an emergent property, and the nature of life could be discussed in the light of this, including differences between living and non-living things and problems about defining death in medical decisions.
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2.1Core2.1.8ExplainExplain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but not others.3
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2.1Core2.1.9StateState that stem cells retain the capacity to divide and have the ability to differentiate along different pathways.1
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2.1Core2.1.10OutlineOutline one therapeutic use of stem cells.2This is an area of rapid development. In 2005, stem cells were used to restore the insulation tissue of neurons in laboratory rats, resulting in subsequent improvements in their mobility. Any example of the therapeutic use of stem cells in humans or other animals can be chosen. TOKTOK: This is an opportunity to discuss balancing the huge opportunities of therapeutic cloning against the considerable risks—for example, stem cells developing into tumours. Another issue is how the scientific community conveys information about its work to the wider community in such a way that informed decisions about research can be made.Aim8Aim 8: There are ethical issues involved in stem cell research, whether humans or other animals are used. Use of embryonic stem cells involves the death of early-stage embryos, but if therapeutic cloning is successfully developed the suffering of patients with a wide variety of conditions could be reduced. Int: Stem cell research has depended on the work of teams of scientists in many countries, who share results and so speed up the rate of progress. However, ethical concerns about the procedures have led to restrictions on research in some countries. National governments are influenced by local, cultural and religious traditions, which vary greatly, and these, therefore, have an impact on the work of scientists.
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2.2Core2.2.1DrawDraw and label a diagram of the ultrastructure of Escherichia coli (E. coli) as an example of a prokaryote.1The diagram should show the cell wall, plasma membrane, cytoplasm, pili, flagella, ribosomes and nucleoid (region containing naked DNA).
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2.2Core2.2.2AnnotateAnnotate the diagram from 2.2.1 with the functions of each named structure.2
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2.2Core2.2.3IdentifyIdentify structures from 2.2.1 in electron micrographs of E. coli.2
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2.2Core2.2.4StateState that prokaryotic cells divide by binary fission.1
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2.3Core2.3.1DrawDraw and label a diagram of the ultrastructure of a liver cell as an example of an animal cell.1The diagram should show free ribosomes, rough endoplasmic reticulum (rER), lysosome, Golgi apparatus, mitochondrion and nucleus. The term Golgi apparatus will be used in place of Golgi body, Golgi complex or dictyosome.
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2.3Core2.3.2AnnotateAnnotate the diagram from 2.3.1 with the functions of each named structure.2
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2.3Core2.3.3IndentifyIdentify structures from 2.3.1 in electron micrographs of liver cells.2
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2.3Core2.3.4CompareCompare prokaryotic and eukaryotic cells.3Differences should include: naked DNA versus DNA associated with proteins, DNA in cytoplasm versus DNA enclosed in a nuclear envelope, no mitochondria versus mitochondria, 70S versus 80S ribosomes, eukaryotic cells have internal membranes that compartmentalize their functions.
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2.3Core2.3.5StateState three differences between plant and animal cells.1
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2.3Core2.3.6OutlineOutline two roles of extracellular components.2The plant cell wall maintains cell shape, prevents excessive water uptake, and holds the whole plant up against the force of gravity. Animal cells secrete glycoproteins that form the extracellular matrix. This functions in support, adhesion and movement.
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2.4Core2.4.1DrawDraw and label a diagram to show the structure of membranes.1The diagram should show the phospholipid bilayer, cholesterol, glycoproteins, and integral and peripheral proteins. Use the term plasma membrane, not cell surface membrane, for the membrane surrounding the cytoplasm. Integral proteins are embedded in the phospholipid of the membrane, whereas peripheral proteins are attached to its surface. Variations in composition related to the type of membrane are not required.
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2.4Core2.4.2ExplainExplain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes.3
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2.4Core2.4.3ListList the functions of membrane proteins.1Include the following: hormone binding sites, immobilized enzymes, cell adhesion, cell-to-cell communication, channels for passive transport, and pumps for active transport.
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2.4Core2.4.4DefineDefine diffusion and osmosis.1Diffusion is the passive movement of particles from a region of high concentration to a region of low concentration. Osmosis is the passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.Aim7Aim 7: Data logging to measure the changes in membrane permeability using colorimeter probes can be used.
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2.4Core2.4.5ExplainExplain passive transport across membranes by simple diffusion and facilitated diffusion.3
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2.4Core2.4.6ExplainExplain the role of protein pumps and ATP in active transport across membranes.3
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2.4Core2.4.7ExplainExplain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus and plasma membrane.3
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2.4Core2.4.8DescribeDescribe how the fluidity of the membrane allows it to change shape, break and re-form during endocytosis and exocytosis.2
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2.5Core2.5.1OutlineOutline the stages in the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis.2
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2.5Core2.5.2StateState that tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue.1
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2.5Core2.5.3StateState that interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts.1
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2.5Core2.5.4DescribeDescribe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telophase).2Include supercoiling of chromosomes, attachment of spindle microtubules to centromeres, splitting of centromeres, movement of sister chromosomes to opposite poles, and breakage and re-formation of nuclear membranes. Textbooks vary in the use of the terms chromosome and chromatid. In this course, the two DNA molecules formed by DNA replication are considered to be sister chromatids until the splitting of the centromere at the start of anaphase; after this, they are individual chromosomes. The term kinetochore is not expected. Aim7Aim 7: Students could determine mitotic index and fraction of cells in each phase of mitosis. Individual groups could paste data into a database. Pie charts could be constructed with a graphing computer program. If a graphing computer program is used in DCP for internal assessment, it should be according to the IA and ICT clarifications.
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2.5Core2.5.5ExplainExplain how mitosis produces two genetically identical nuclei.3
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2.5Core2.5.6StateState that growth, embryonic development, tissue repair and asexual reproduction involve mitosis.1
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3.1Core3.1.1StateState that the most frequently occurring chemical elements in living things are carbon, hydrogen, oxygen and nitrogen.1
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3.1Core3.1.2StateState that a variety of other elements are needed by living organisms, including sulfur, calcium, phosphorus, iron and sodium.1
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3.1Core3.1.3StateState one role for each of the elements mentioned in 3.1.2.1Refer to the roles in plants, animals and prokaryotes.
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3.1Core3.1.6ExplainExplain the relationship between the properties of water and its uses in living organisms as a coolant, medium for metabolic reactions and transport medium.3Limit the properties to those outlined in 3.1.5.TOKTOK: Claims about the “memory of water” have been categorized as pseudoscientific. By what criteria can a claim be judged to be pseudoscientific?Aim7Aim 7: Data logging could be carried out to compare the thermal properties of water with those of other liquids.
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3.2Core3.2.1DistinguishDistinguish between organic and inorganic compounds.2Compounds containing carbon that are found in living organisms (except hydrogencarbonates, carbonates and oxides of carbon) are regarded as organic.
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3.2Core3.2.2IndentifyIdentify amino acids, glucose, ribose and fatty acids from diagrams showing their structure.2Specific names of amino acids and fatty acids are not expected.
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3.2Core3.2.3ListList three examples each of monosaccharides, disaccharides and polysaccharides.1The examples used should be: glucose, galactose and fructose; maltose, lactose and sucrose; starch, glycogen and cellulose.
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3.2Core3.2.4StateState one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants.1
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3.2Core3.2.5OutlineOutline the role of condensation and hydrolysis in the relationships between monosaccharides, disaccharides and polysaccharides; between fatty acids, glycerol and triglycerides; and between amino acids and polypeptides.2This can be dealt with using equations with words or chemical formulas.
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3.2Core3.2.6StateState three functions of lipids.1Include energy storage and thermal insulation.
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3.2Core3.2.7CompareCompare the use of carbohydrates and lipids in energy storage.3
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3.3Core3.3.1OutlineOutline DNA nucleotide structure in terms of sugar (deoxyribose), base and phosphate.2Chemical formulas and the purine/pyrimidine subdivision are not required. Simple shapes can be used to represent the component parts. Only the relative positions are required.
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3.3Core3.3.2StateState the names of the four bases in DNA.1
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3.3Core3.3.3OutlineOutline how DNA nucleotides are linked together by covalent bonds into a single strand.2Only the relative positions are required.
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3.3Core3.3.4ExplainExplain how a DNA double helix is formed using complementary base pairing and hydrogen bonds.3
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3.3Core3.3.5DrawDraw and label a simple diagram of the molecular structure of DNA.1An extension of the diagram in 3.3.3 is sufficient to show the complementary base pairs of A–T and G–C, held together by hydrogen bonds and the sugar–phosphate backbones. The number of hydrogen bonds between pairs and details of purine/pyrimidines are not required.TOKTOK: The story of the elucidation of the structure of DNA illustrates that cooperation and collaboration among scientists exists alongside competition between research groups. To what extent was Watson and Crick’s “discovery” of the three-dimensional structure of DNA dependent on the use of data generated by Rosalind Franklin, which was shared without her knowledge or consent?
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3.4Core3.4.1ExplainExplain DNA replication in terms of unwinding the double helix and separation of the strands by helicase, followed by formation of the new complementary strands by DNA polymerase.3It is not necessary to mention that there is more than one DNA polymerase.
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3.4Core3.4.2ExplainExplain the significance of complementary base pairing in the conservation of the base sequence of DNA.3
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3.4Core3.4.3StateState that DNA replication is semi-conservative.1
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3.5Core3.5.1CompareCompare the structure of RNA and DNA.3Limit this to the names of sugars, bases and the number of strands.
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3.5Core3.5.2OutlineOutline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase.2
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3.5Core3.5.3DescribeDescribe the genetic code in terms of codons composed of triplets of bases.2
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3.5Core3.5.4ExplainExplain the process of translation, leading to polypeptide formation.3Include the roles of messenger RNA (mRNA), transfer RNA (tRNA), codons, anticodons, ribosomes and amino acids.
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3.5Core3.5.5DiscussDiscuss the relationship between one gene and one polypeptide.3Originally, it was assumed that one gene would invariably code for one polypeptide, but many exceptions have been discovered.TOKTOK: The way in which theories are modified as related evidence accumulates could be discussed, and whether contrary evidence should cause a theory to be discarded immediately if there are exceptions to it. Where a theory is suddenly and totally abandoned, to be replaced by a different theory, this is known as a paradigm shift.
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3.6Core3.6.1DefineDefine enzyme and active site.1
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3.6Core3.6.2ExplainExplain enzyme–substrate specificity.3The lock-and-key model can be used as a basis for the explanation. Refer to the three-dimensional structure. The induced-fit model is not expected at SL.
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3.6Core3.6.3ExplainExplain the effects of temperature, pH and substrate concentration on enzyme activity.3Aim7-8Aim 7: Enzyme activity could be measured using data loggers such as pressure sensors, pH sensors or colorimeters. Aim 8: The effects of environmental acid rain could be discussed.
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3.6Core3.6.4DefineDefine denaturation.1Denaturation is a structural change in a protein that results in the loss (usually permanent) of its biological properties. Refer only to heat and pH as agents.
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3.6Core3.6.5ExplainExplain the use of lactase in the production of lactose-free milk.3TOKInt/TOK: Development of some techniques benefits particular human populations and not others because of the natural variation in human characteristics. Lactose intolerance is found in a high proportion of the human population (for example, in Asia) but more rarely among those of European origin. Sometimes a transfer of biotechnology is needed when techniques are developed in one part of the world that are more applicable in another.
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3.7Core3.7.1DefineDefine cell respiration.1Cell respiration is the controlled release of energy from organic compounds in cells to form ATP.
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3.7Core3.7.2StateState that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP.1
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3.7Core3.7.3ExplainExplain that, during anaerobic cell respiration, pyruvate can be converted in the cytoplasm into lactate, or ethanol and carbon dioxide, with no further yield of ATP.3Mention that ethanol and carbon dioxide are produced in yeast, whereas lactate is produced in humans.Aim7Aim 7: Data logging using gas sensors, oxygen, carbon dioxide or pH probes could be used.
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3.7Core3.7.4ExplainExplain that, during aerobic cell respiration, pyruvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP.3
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3.8Core3.8.1StateState that photosynthesis involves the conversion of light energy into chemical energy.1
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3.8Core3.8.2StateState that light from the Sun is composed of a range of wavelengths (colours).1Reference to actual wavelengths or frequencies is not expected.
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3.8Core3.8.3StateState that chlorophyll is the main photosynthetic pigment.1
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3.8Core3.8.4OutlineOutline the differences in absorption of red, blue and green light by chlorophyll.2Students should appreciate that pigments absorb certain colours of light. The remaining colours of light are reflected. It is not necessary to mention wavelengths or the structure responsible for the absorption.Aim7Aim 7: Data logging using colorimeters or light sensors could be used.
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3.8Core3.8.5StateState that light energy is used to produce ATP, and to split water molecules (photolysis) to form oxygen and hydrogen.1
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3.8Core3.8.6StateState that ATP and hydrogen (derived from the photolysis of water) are used to fix carbon dioxide to make organic molecules.1
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3.8Core3.8.7ExplainExplain that the rate of photosynthesis can be measured directly by the production of oxygen or the uptake of carbon dioxide, or indirectly by an increase in biomass.3The recall of details of specific experiments to indicate that photosynthesis has occurred or to measure the rate of photosynthesis is not expected.
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3.8Core3.8.8OutlineOutline the effects of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis.2The shape of the graphs is required. The concept of limiting factors is not expected.Aim7Aim 7: Data logging using gas sensors, oxygen, carbon dioxide or pH probes could be used.
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4.1Core4.1.1StateState that eukaryote chromosomes are made of DNA and proteins.1The names of the proteins (histones) are not required, nor is the structural relationship between DNA and the proteins.
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4.1Core4.1.2DefineDefine gene, allele and genome.1Gene: a heritable factor that controls a specific characteristic. (The differences between structural genes, regulator genes and genes coding for tRNA and rRNA are not expected at SL). Allele: one specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene. Genome: the whole of the genetic information of an organism.
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4.1Core4.1.3DefineDefine gene mutation.1The terms point mutation or frameshift mutation will not be used.
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4.1Core4.1.4ExplainExplain the consequence of a base substitution mutation in relation to the processes of transcription and translation, using the example of sickle-cell anemia.3GAG has mutated to GTG causing glutamic acid to be replaced by valine, and hence sickle-cell anemia.TOKThere are also ethical issues relating to screening of fetuses and abortion of those found to have a genetic disease. TOK: Where a correlation is found, a causal link may or may not be present. The frequency of the sickle-cell allele is correlated with the prevalence of malaria in many parts of the world. In this case, there is a clear causal link. Other cases where there is no causal link could be described as a contrast. There has clearly been natural selection in favour of the sickle-cell allele in malarial areas, despite it causing severe anemia in the homozygous condition. Natural selection has led to particular frequencies of the sickle-cell and the normal hemoglobin alleles, to balance the twin risks of anemia and malaria.Aim8Aim 8: There is a variety of social issues associated with sickle-cell anemia, including the suffering due to anemia, personal feelings if one has either inherited or passed on the sickle-cell allele, questions relating to the desirability of genetic screening for the sickle-cell allele before having children, and the genetic counselling of carriers of the allele.
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4.2Core4.2.1StateState that meiosis is a reduction division of a diploid nucleus to form haploid nuclei.1
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4.2Core4.2.2DefineDefine homologous chromosomes.1
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4.2Core4.2.3OutlineOutline the process of meiosis, including pairing of homologous chromosomes and crossing over, followed by two divisions, which results in four haploid cells.2Limit crossing over to the exchange of genetic material between non-sister chromatids during prophase I. Names of the stages are required.
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4.2Core4.2.4ExplainExplain that non-disjunction can lead to changes in chromosome number, illustrated by reference to Down syndrome (trisomy 21).3The characteristics of Down syndrome are not required.
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4.2Core4.2.5StateState that, in karyotyping, chromosomes are arranged in pairs according to their size and structure.1
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4.2Core4.2.6StateState that karyotyping is performed using cells collected by chorionic villus sampling or amniocentesis, for pre-natal diagnosis of chromosome abnormalities.1TOKTOK: Various questions relating to karyotyping could be raised, including balancing the risks of side-effects (for example, miscarriage) against the possibility of identifying and aborting a fetus with an abnormality. There are questions about decision-making: who should make the decision about whether to perform karyotyping and allow a subsequent abortion—parents or health-care professionals or both groups? There are also questions about whether or not national governments should interfere with personal freedoms, and whether or not they should be able to ban procedures within the country and possibly also ban citizens travelling to foreign countries where the procedures are permitted.Aim8Aim 8: There are ethical and social issues associated with karyotyping of unborn fetuses because this procedure allows parents to abort fetuses with a chromosome abnormality. There is also evidence that, in some parts of the world, abortion on the basis of gender is carried out.
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4.2Core4.2.7AnalyseAnalyse a human karyotype to determine gender and whether non-disjunction has occurred.3Karyotyping can be done by using enlarged photographs of chromosomes.Aim7Aim 7: Online simulations of karyotyping activities are available.
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4.3Core4.3.1DefineDefine genotype, phenotype, dominant allele, recessive allele, codominant alleles, locus, homozygous, heterozygous, carrier and test cross.1Genotype: the alleles of an organism. Phenotype: the characteristics of an organism. Dominant allele: an allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state. Recessive allele: an allele that only has an effect on the phenotype when present in the homozygous state. Codominant alleles: pairs of alleles that both affect the phenotype when present in a heterozygote. (The terms incomplete and partial dominance are no longer used.) Locus: the particular position on homologous chromosomes of a gene. Homozygous: having two identical alleles of a gene. Carrier: an individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele. Test cross: testing a suspected heterozygote by crossing it with a known homozygous recessive. (The term backcross is no longer used.)
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4.3Core4.3.2DetermineDetermine the genotypes and phenotypes of the offspring of a monohybrid cross using a Punnett grid.3The grid should be labelled to include parental genotypes, gametes, and both offspring genotype and phenotype.Aim7Aim 7: Genetics simulation software is available.
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4.3Core4.3.3StateState that some genes have more than two alleles (multiple alleles).1
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4.3Core4.3.4DescribeDescribe ABO blood groups as an example of codominance and multiple alleles.2
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4.3Core4.3.5ExplainExplain how the sex chromosomes control gender by referring to the inheritance of X and Y chromosomes in humans.3
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4.3Core4.3.6StateState that some genes are present on the X chromosome and absent from the shorter Y chromosome in humans.1