IB Biology Exam Secrets
Topic 1: Cell biology
Welcome to day one!
Get Ready to Rock IB Bio Papers!
If you are looking for an outline that will guide you to perform really well in the Biology exam, this is the one
that you can rely on.
First, Let’s focus on Topic 1: Cell Biology.
This topic has one of the highest percentage (28%) of occurrence in the papers.
Below you can find the subtopics of Topic 1 and the percentage of how many times they appear on the
exams the last two years.
Every subtopic is important for the exam, but some are known to be seen more often than others.
Here you will find some guidance on the content that you should focus more on.
1.1 Introduction to cells: Very Common SubTopic
Focus more on these understandings, applications, and skills:
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According to the cell theory, living organisms are composed of cells
The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic
development and also makes stem cells suitable for therapeutic uses
Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate
fungal hyphae
Use of stem cells to treat Stargardt’s disease and one other named condition
Use of a light microscope to investigate the structure of cells and tissues, with drawing of cells
Calculation of the magnification of drawings and the actual size of structures and ultrastructures shown in
drawings or micrographs
Questions related to these are:
Different Cell theory exceptions
Stem cell use in Stargardt’s disease and diabetes
Stell cell advantages and disadvantages
1.2 Ultrastructure of cells: Very common subtopic
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Prokaryotes have a simple cell structure without compartmentalisation
Eukaryotes have a compartmentalised cell structure
Structure and function of organelles within exocrine gland cells of the pancreas and within palisade
mesophyll cells of the leaf
Drawing of the ultrastructure of prokaryotic cells based on electron micrographs
Drawing of the ultrastructure of eukaryotic cells based on electron micrographs
Interpretation of electron micrographs to identify organelles and deduce the function of specialised cell
Questions related to these are:
Differences between prokaryotic and eukaryotic cells, include organelles functions
Electrographs related to Prokaryotic, Eukaryotic, include Small intestine and pancreas cells
1.3 Membrane structure: Least common subtopic
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Cholesterol in mammalian membranes reduces membrane fluidity and permeability to some solutes
Membrane proteins are diverse in terms of structure, position in the membrane and function
Analysis of evidence from electron microscopy that leads to the proposal of the Davson-Danielli model
Analysis of the falsification of the Davson-Danielli model that lead to the Singer-Nicolson model
Questions related to these are:
Davidson and Danelli theory explanation
Cholesterol role in cell membrane fluidity.
Cell membrane and its composition
1.4 Membrane transport: Common Topic
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Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport
The fluidity of membranes allows materials to be taken into cells by endocytosis or released by exocytosis
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Estimation of osmolarity in tissues by bathing samples in hypotonic and hypertonic solutions
Questions related to these are:
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Differentiate the different types of transportation from inside and outside the cell.
Explain how materials are transported by vesicles inside and outside cell through endocytosis and
exocytosis.
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1.5 The origin of cells: Common Topic
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Cells can only be formed by division of pre-existing cells
The first cells must have arisen from non-living material
The origin of eukaryotic cells can be explained by the endosymbiotic theory
Evidence from Pasteur’s experiments that spontaneous generation of cells and organisms does not now
occur on Earth
Questions related to these are:
Explain the endosymbiotic theory.
Explain the Pasteur’s experiment.
1.6 Cell division: Common Topic
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Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and
cytoplasm
Cytokinesis occurs after mitosis and is different in plant and animal cells
Cyclins are involved in the control of the cell cycle
Identification of phases of mitosis in cells viewed with a microscope or in a micrograph
Questions related to these are:
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Cell cycle and its phases, description about each
Mitosis and its stages, describe them and identify them in micrographs
How the cell cycle is controlled from one stage to the other
Topic 2: Molecular Biology
Welcome to Day Two!
Today’s Focus will be on Topic 2: Molecular Biology.
This topic has 14% of occurrence in the papers 1 and 2.
Below you can find the subtopics of Topic 2 and the percentage of how many times they appear on the
exams from the last two years.
Every subtopic is important for the exam, but some are known to be seen more often than others.
Here you will find some guidance on the content that you should focus more on.
2.1 Molecules to metabolism: Least common subtopic
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Urea as an example of a compound that is produced by living organisms but can also be artificially
synthesized
Drawing molecular diagrams of glucose, ribose, a saturated fatty acid and a generalised amino acid
Identification of biochemicals such as sugars, lipids or amino acids from molecular diagrams
Questions related to these are:
Usually there is identification or drawing of the structures such as fatty acid, amino acid, starch;
Explain the process of Urea production.
2.2 Water: Least common subtopic
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Hydrogen bonds and bipolarity explain the cohesive, adhesive, thermal and solvent properties of water
Substances can be hydrophilic or hydrophobic
Comparison of the thermal properties of water with those of methane
Use of water as a coolant in sweat
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Modes of transport of glucose, amino acids, cholesterol, fats, oxygen and sodium chloride in blood in
relation to their solubility in water
Questions related to these are:
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Water properties and how it affects the environment, usually it comes as multiple choice or as a long
answer question.
2.3 Carbohydrates and lipids: Common Topic
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Fatty acids can be saturated, monounsaturated or polyunsaturated
Triglycerides are formed by condensation from three fatty acids and one glycerol
Structure and function of cellulose and starch in plants and glycogen in humans
Lipids are more suitable for long-term energy storage in humans than carbohydrates
Determination of body mass index by calculation or use of a nomogram
Questions related to these are:
Analyze nomogram
Compare energy of lipid against carbohydrates
Identify the difference between saturated and unsaturated
2.4 Proteins Least, common subtopic
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The amino acid sequence of polypeptides is coded for by genes
A protein may consist of a single polypeptide or more than one polypeptide linked together
The amino acid sequence determines the three-dimensional conformation of a protein
Denaturation of proteins by heat or by deviation of pH from the optimum
Questions related to these are:
Describe primary and tertiary structures for proteins
Identify when proteins are denatured by heat or pH
2.5 Enzymes, Least common subtopic
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Temperature, pH and substrate concentration affect the rate of activity of enzymes
Enzymes can be denatured
Design of experiments to test the effect of temperature, pH and substrate concentration on the activity of
enzymes
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Experimental investigation of a factor affecting enzyme activity
Questions related to these are:
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Enzymes role in different processes
How enzymes are denatured dependent on the environment.
Explain the factors that affect enzyme activity, temperature, pH and substrate concentration
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2.6 Structure of DNA and RNA, Least common subtopic
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DNA differs from RNA in the number of strands present, the base composition and the type of pentose
DNA is a double helix molecule made of two antiparallel strands of nucleotides linked by hydrogen bonding
between complementary base pairs
Drawing simple diagrams of the structure of single nucleotides of DNA and RNA, using circles, pentagons
and rectangles to represent phosphates, pentoses and bases
Questions related to these are:
Difference between DNA and RNA structure
Be able to draw nucleotides and DNA structure
2.7 DNA replication, transcription and translation: Very Common SubTopic
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The replication of DNA is semi-conservative and depends on complementary base pairing
Helicase unwinds the double helix and separates the two strands by breaking hydrogen bonds
DNA polymerase links nucleotides together to form a new strand, using the pre-existing strand as a
template
Transcription is the synthesis of mRNA copied from the DNA base sequences by RNA polymerase
Translation is the synthesis of polypeptides on ribosomes
The amino acid sequence of polypeptides is determined by mRNA according to the genetic code
Codons of three bases on mRNA correspond to one amino acid in a polypeptide
Translation depends on complementary base pairing between codons on mRNA and anticodons on tRNA
Use a table of the genetic code to deduce which codon(s) corresponds to which amino acid
Analysis of Meselson and Stahl’s results to obtain support for the theory of semi-conservative replication of
DNA
Use a table of mRNA codons and their corresponding amino acids to deduce the sequence of amino acids
coded by a short mRNA strand of known base sequence
Deducing the DNA base sequence for the mRNA strand
Questions related to these are:
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Transcription of mRNA and reading codons to amino acids
Explain DNA replication and translation, how ribosomes are important for it.
mRNA codes are given and students need to deduce the DNA base sequence
Explain the Meselson and Stahl’s results and how it support semi-conservative replication.
2.8 Cell respiration, Very Common SubTopic
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Cell respiration is the controlled release of energy from organic compounds to produce ATP
ATP from cell respiration is immediately available as a source of energy in the cell
Anaerobic cell respiration gives a small yield of ATP from glucose
Aerobic cell respiration requires oxygen and gives a large yield of ATP from glucose
Lactate production in humans when anaerobic respiration is used to maximise the power of muscle
contractions
Questions related to these are:
Identify Cell Respiration reactants and products
Explain different stages of cell respiration
Understand the difference between aerobic and anaerobic process
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Photosynthesis is the production of carbon compounds in cells using light energy
Visible light has a range of wavelengths with violet the shortest wavelength and red the longest
Chlorophyll absorbs red and blue light most effectively and reflects green light more than other colours
Oxygen is produced in photosynthesis from the photolysis of water
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Temperature, light intensity and carbon dioxide concentration are possible limiting factors on the rate of
photosynthesis
Drawing an absorption spectrum for chlorophyll and an action spectrum for photosynthesis
Separation of photosynthetic pigments by chromatography
Questions related to these are:
Be able to draw or identify the action and absorption spectrums
Explain the process of light dependent and dependent.
Identify and explain the factors that affect photosynthesis.
Topic 3: Genetics
Welcome to Day Three!
Today’s Focus will be on Topic 3: Genetics.
This topic has 18% of occurrence in the papers 1 and 2.
Below you can find the subtopics of Topic 3 and the percentage of how many times they appear on the
exams from the last two years.
Every subtopic is important for the exam, but some are known to be seen more often than others. Here you
will find some guidance on the content that you should focus more on.
3.1 Genes
Very Common SubTopic
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A gene occupies a specific position on a chromosome
The various specific forms of a gene are alleles
Alleles differ from each other by one or only a few bases
New alleles are formed by mutation
The genome is the whole of the genetic information of an organism
The causes of sickle cell anaemia, including a base substitution mutation, a change to the base sequence
of mRNA transcribed from it and a change to the sequence of a polypeptide in haemoglobin
Comparison of the number of genes in humans with other species
Questions related to these are:
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Know about the Universal genetic code, how ATCG is found in every species;
Identify Gene mutation, learn specific example: Sickle cell anemia.
Comparison of genes and bases, chromosomes of different species
3.2 Chromosomes
Common Topic
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Homologous chromosomes carry the same sequence of genes but not necessarily the same alleles of
those genes
Diploid nuclei have pairs of homologous chromosomes
Haploid nuclei have one chromosome of each pair
A karyogram shows the chromosomes of an organism in homologous pairs of decreasing length
Sex is determined by sex chromosomes and autosomes are chromosomes that do not determine sex
Cairns’ technique for measuring the length of DNA molecules by autoradiography
Use of karyograms to deduce sex and diagnose Down syndrome in humans
Questions related to these are:
Diploid versus haploid, know the difference between homologous chromosomes and sister chromatids.
Know the purpose of Cairn’s technique
Understand how to read the karyogram and find the sex of the baby.
3.3 Meiosis
Least common subtopic
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One diploid nucleus divides by meiosis to produce four haploid nuclei
Separation of pairs of homologous chromosomes in the first division of meiosis halves the chromosome
number
The early stages of meiosis involve pairing of homologous chromosomes and crossing over followed by
condensation
Orientation of pairs of homologous chromosomes prior to separation is random
Crossing over and random orientation promotes genetic variation
Fusion of gametes from different parents promotes genetic variation
Non-disjunction can cause Down syndrome and other chromosomal abnormalities
Drawing diagrams to show the stages of meiosis resulting in the formation of four haploid cells
Questions related to these are:
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Know the stages of Meiosis I and II. Be able to compare the two stages and compare it to mitosis
Understand the behavior of the chromosomes while they go through the meiosis stages.
Be able to explain how cross over and random orientation promotes genetic variation.
Usually IB place diagram of meiosis stages for students to Identify them.
3.4 Inheritance
Least common subtopic
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Dominant alleles mask the effect of recessive alleles but co-dominant alleles have joint effects
Many genetic diseases in humans are due to recessive alleles of autosomal genes, although some genetic
diseases are due to dominant or co-dominant alleles
Some genetic diseases are sex linked
The pattern of inheritance is different with sex-linked genes due to their location on sex chromosomes
Inheritance of ABO blood groups
Red-green colour blindness and haemophilia as examples of sex-linked inheritance
Inheritance of cystic fibrosis and Huntington’s disease
Construction of Punnett grids for predicting the outcomes of monohybrid genetic crosses
Analysis of pedigree charts to deduce the patterns of inheritance of genetic diseases
Questions related to these are:
Blood type crosses are common in paper 1, trying to identify the offspring.
Student should be able to analyze the Pedigree chart, be able to know the genotype of individuals in the
chart.
Know the difference between Dominant versus Recessive alleles, as well as codominance punnett square
problems.
3.5 Genetic modification and biotechnology
Very Common SubTopic
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PCR can be used to amplify small amounts of DNA
Gel electrophoresis is used to separate proteins or fragments of DNA according to size
DNA profiling involves comparison of DNA
Genetic modification is carried out by gene transfer between species
Use of DNA profiling in paternity and forensic investigations
Gene transfer to bacteria using plasmids makes use of restriction endonucleases and DNA ligase
Assessment of the potential risks and benefits associated with genetic modification of crops
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Production of cloned embryos produced by somatic cell nuclear transfer
Analysis of examples of DNA profiles
Questions related to these are:
Understand the Gel electrophoresis process, how the data is read in paternity and forensic investigation.
Somatic Nuclear transfer, how the process is conducted?
Explain the polymerase chain reactions.
Know the benefits and disadvantages of GMO.
Topic 4: Ecology
Welcome to Day Four!
Today’s Focus will be on Topic 4: Ecology.
This topic has 27% of occurrence in the papers 1 and 2. Below you can find the subtopics of Topic 4 and
the percentage of how many times they appear on the exams from the last two years.
4.1 Species, Communities and Ecosystems
Common Topic
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Species have either an autotrophic or heterotrophic method of nutrition (a few species have both methods)
Consumers are heterotrophs that feed on living organisms by ingestion
Detritivores are heterotrophs that obtain organic nutrients from detritus by internal digestion
Saprotrophs are heterotrophs that obtain organic nutrients from dead organisms by external digestion
Classifying species as autotrophs, consumers, detritivores or saprotrophs from a knowledge of their mode
of nutrition
Setting up sealed mesocosms to try to establish sustainability
Questions related to these are:
Know the difference between heterotrophs and autotrophs
Know the benefits and disadvantages of mesocosm
Know the role of decomposers
4.2 Energy Flow
Common Topic
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Most ecosystems rely on a supply of energy from sunlight
Chemical energy in carbon compounds flows through food chains by means of feeding
Energy released from carbon compounds by respiration is used in living organisms and converted to heat
Living organisms cannot convert heat to other forms of energy
Heat is lost from ecosystems
Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic
levels
Quantitative representations of energy flow using pyramids of energy
Questions related to these are:
Be able to create a feeding chain
Know the trophic levels of each animal in the chain
Know the consumers and produces in a food web
Be able to analyse an energy flow chart
Be able to deduce the energy transfer in a pyramid of energy
4.3 Carbon Cycling
Very Common SubTopic
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In aquatic ecosystems carbon is present as dissolved carbon dioxide and hydrogen carbonate ions
Carbon dioxide diffuses from the atmosphere or water into autotrophs
Carbon dioxide is produced by respiration and diffuses out of organisms into water or the atmosphere
Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in
waterlogged soils
Partially decomposed organic matter from past geological eras was converted into either coal or into oil and
gas that accumulates in porous rocks
Animals such as reef-building corals and mollusca have hard parts that are composed of calcium carbonate
and can become fossilised in limestone
Estimation of carbon fluxes due to processes in the carbon cycle
Analysis of data from air monitoring stations to explain annual fluctuations
Questions related to these are:
Explain the process of carbon fluxes and how it impacts coral reef or mollusca
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Analyze data related to carbon in the atmosphere
Outline the process of making peat.
4.4 Climate Change
Very Common SubTopic
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The impact of a gas depends on its ability to absorb long wave radiation as well as on its concentration in
the atmosphere
The warmed Earth emits longer wavelength radiation (heat)
Longer wave radiation is absorbed by greenhouse gases that retain the heat in the atmosphere
Global temperatures and climate patterns are influenced by concentrations of greenhouse gases
Threats to coral reefs from increasing concentrations of dissolved carbon dioxide
Correlations between global temperatures and carbon dioxide concentrations on Earth
Evaluating claims that human activities are not causing climate change
Questions related to these are:
Explain the Greenhouse gases and its effect on the atmosphere, climate change.
Differentiate the long wave from short wave.
Explain how carbon dioxide can affect coral reefs.
Topic 5: Evolution and biodiversity
5.1 Evidence for Evolution
Common Topic
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The fossil record provides evidence for evolution
Evolution of homologous structures by adaptive radiation explains similarities in structure when there are
differences in function
Populations of a species can gradually diverge into separate species by evolution
Continuous variation across the geographical range of related populations matches the concept of gradual
divergence
Development of melanistic insects in polluted areas
Comparison of the pentadactyl limb of mammals, birds, amphibians and reptiles with different methods of
locomotion
Questions related to these are:
Outline how fossil records provide evidence for evolution
Differentiate between adaptive and gradual divergence.
Identify all the possible causes of speciation.
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Explain the peppered moth evolution
Describe how homologous structure supports evolution.
5.2 Natural Selection
Very Common SubTopic
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Natural selection can only occur if there is variation among members of the same species
Mutation, meiosis and sexual reproduction cause variation between individuals in a species
Species tend to produce more offspring than the environment can support
Individuals that are better adapted tend to survive and produce more offspring while the less well adapted
tend to die or produce fewer offspring
Individuals that reproduce pass on characteristics to their offspring
Natural selection increases the frequency of characteristics that make individuals better adapted and
decreases the frequency of other characteristics leading to changes within the species
Evolution of antibiotic resistance in bacteria
Questions related to these are:
Explain how there is variation in the population and how it lead to overproduction.
Discuss the impact of natural selection on evolution
Explain how antibiotic resistance in bacteria lead to its own evolution.
5.3 Classification of Biodiversity
Very Common SubTopic
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All organisms are classified into three domains
Taxonomists classify species using a hierarchy of taxa
The principal taxa for classifying eukaryotes are kingdom, phylum, class, order, family, genus and species
In a natural classification, the genus and accompanying higher taxa consists of all the species that have
evolved from one common ancestral species
Recognition features of bryophyta, filicinophyta, coniferophyta and angiospermophyta
Recognition features of porifera, cnidaria, platyhelmintha, annelida, mollusca, arthropoda and chordata
Recognition features of birds, mammals, amphibians, reptiles and fish
Questions related to these are:
Know all the phylums, including their traits and examples. Usually IB give pictures and you must identify it
or name their traits.
Know the difference between the three domains
Be able to classify animal using the taxonomy classification.
5.4 Cladistics
Very Common SubTopic
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A clade is a group of organisms that have evolved from a common ancestor
Cladograms are tree diagrams that show the most probable sequence of divergence in clades
Evidence for which species are part of a clade can be obtained from the base sequence of a gene or the
corresponding amino acid sequence of a protein
Sequence differences accumulate gradually so there is a positive correlation between the number of
differences between two species and the time since they diverged from a common ancestor
Traits can be analogous or homologous
Analysis of cladograms to deduce evolutionary relationships
Questions related to these are:
Cladogram is given and student needs to identify species that are closely related.
Cladogram can be about DNA structure or animal trait.
Define analogous and homologous traits
Topic 6: Human Physiology
6.1 Digestion and absorption
Very Common Subtopic
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Villi increase the surface area of epithelium over which absorption is carried out
Villi absorb monomers formed by digestion as well as mineral ions and vitamins
Different methods of membrane transport are required to absorb different nutrients
Processes occurring in the small intestine that result in the digestion of starch and transport of the products
of digestion to the liver
Identification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a
micrograph
Questions related to these are:
Describe the villi and microvilli function and structure in the small intestine.
Be able to identify the structure of small intestine in a micrograph
Outline the way in which nutrients are absorbed in the body.
6.2 The Blood System
Common Subtopic
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Arteries convey blood at high pressure from the ventricles to the tissues of the body
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Arteries have muscle cells and elastic fibres in their walls
The muscle and elastic fibres assist in maintaining blood pressure between pump cycles
Capillaries have permeable walls that allow exchange of material between cells in the tissue and the blood
in the capillary
Veins collect blood at low pressure from the tissues of the body and return it to the atria of the heart
The heart beat is initiated by a group of specialised muscle cells in the right atrium called the sinoatrial
node
The sinoatrial node acts as a pacemaker
The sinoatrial node sends out an electrical signal that stimulates contraction as it is propagated through the
walls of the atria and then the walls of the ventricles
Identification of blood vessels as arteries, capillaries or veins from the structure of their walls
Recognition of the chambers and valves of the heart and the blood vessels connected to it in dissected
hearts or in diagrams of heart structure
Questions related to these are:
Identify and label the heart structure, as well as blood vessels
Outline the differences between arteries,veins and capillaries.
Describe the cardiac cycle.
Outline the role of pacemaker.
6.3 Defence against infectious disease
Very Common Subtopic
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Some strains of bacteria have evolved with genes that confer resistance to antibiotics and some strains of
bacteria have multiple resistance
Florey and Chain’s experiments to test penicillin on bacterial infections in mice
Questions related to these are:
Explain antibiotic resistance in bacteria strains
Describe Florey and Chain’s experiments, leading to discovery of penicillin.
Explain the antibody production.
6.4 Gas exchange
Least common subtopic
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Ventilation maintains concentration gradients of oxygen and carbon dioxide between air in alveoli and blood
flowing in adjacent capillaries
Air is carried to the lungs in the trachea and bronchi and then to the alveoli in bronchioles
Type I pneumocytes are extremely thin alveolar cells that are adapted to carry out gas exchange
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Type II pneumocytes secrete a solution containing surfactant that creates a moist surface inside the alveoli
to prevent the sides of the alveolus adhering to each other by reducing surface tension
Muscle contractions cause the pressure changes inside the thorax that force air in and out of the lungs to
ventilate them
Different muscles are required for inspiration and expiration because muscles only do work when they
contract
Monitoring of ventilation in humans at rest and after mild and vigorous exercise
Questions related to these are:
Explain the ventilation mechanism.
Outline the effect of exercise on ventilation.
Identify the role of Type I and II pneumocytes.
6.5 Neurons and synapses
Least common subtopic
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Neurons transmit electrical impulses
Neurons pump sodium and potassium ions across their membranes to generate a resting potential
An action potential consists of depolarization and repolarization of the neuron
Nerve impulses are action potentials propagated along the axons of neurons
Propagation of nerve impulses is the result of local currents that cause each successive part of the axon to
reach the threshold potential
Synapses are junctions between neurons and between neurons and receptor or effector cells
When presynaptic neurons are depolarized they release a neurotransmitter into the synapse
A nerve impulse is only initiated if the threshold potential is reached
Secretion and reabsorption of acetylcholine by neurons at synapses
Blocking of synaptic transmission at cholinergic synapses in insects by binding of neonicotinoid pesticides
to acetylcholine receptors
Questions related to these are:
Explain how nerve impulse passes along the neuron.
Explain the synapse transmission.
Describe how pesticide neonicotinoid kills insects.
6.6 Hormones, homeostasis and reproduction
Very Common Subtopic
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Thyroxin is secreted by the thyroid gland to regulate the metabolic rate and help control body temperature
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Leptin is secreted by cells in adipose tissue and act on the hypothalamus of the brain to inhibit appetite
Melatonin is secreted by the pineal gland to control circadian rhythms
A gene on the Y chromosome causes embryonic gonads to develop as testes and secrete testosterone
Testosterone causes pre-natal development of male genitalia and both sperm production and development
of male secondary sexual characteristics during puberty
Estrogen and progesterone cause pre-natal development of female reproductive organs and female
secondary sexual characteristics during puberty
The menstrual cycle is controlled by negative and positive feedback mechanisms involving ovarian and
pituitary hormones
Testing of leptin on patients with clinical obesity and reasons for the failure to control the disease
Causes of jet lag and use of melatonin to alleviate it
Annotate diagrams of the male and female reproductive system to show names of structures and their
functions
Questions related to these are:
Explain jet lab and how melatonin which is produced in the pineal gland influences it.
Explain leptin role on obesity.
Explain how temperature is regulated by the body.
Outline the menstrual cycle and its hormones roles on it.
Identify the male reproductive system
HL Topic 7: Nucleic Acid
7.1 DNA structure and replication (Common Topic)
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DNA structure suggested a mechanism for DNA replication
DNA replication is carried out by a complex system of enzymes
DNA polymerase can only add nucleotides to the 3’ end of a primer
DNA replication is continuous on the leading strand and discontinuous on the lagging strand
Nucleosomes help to supercoil the DNA
7.2 Transcription and gene expression (Very Common Topic)
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Transcription occurs in a 5’ to 3’ direction
Nucleosomes help to regulate transcription in eukaryotes
Eukaryotic cells modify mRNA after transcription
Splicing of mRNA increases the number of different proteins an organism can produce
7.3 Translation (Common Topic)
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The sequence and number of amino acids in a polypeptide is the primary structure
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The secondary structure is the formation of alpha helices and beta pleated sheets stabilised by hydrogen
bonding
The tertiary structure is the further folding of the polypeptide stabilised by interactions between R groups
The quaternary structure exists in proteins with more than one polypeptide chain
tRNA-activating enzymes illustrate enzyme-substrate specificity and the role of phosphorylation
Identification of polysomes in electron micrographs of prokaryotes and eukaryotes
HL Topic 8: Metabolism
8.1 Metabolism (Very Common Sub Topic)
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Enzymes lower the activation energy of the chemical reactions that they catalyse
Enzyme inhibitors can be competitive or non-competitive
Metabolic pathways can be controlled by end-product inhibition
Calculating and plotting rates of reaction from raw experimental results
Distinguishing different types of inhibition from graphs at specified substrate concentration
8.2 Cell Respiration
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Cell respiration involves the oxidation and reduction of electron carriers
Phosphorylation of molecules makes them less stable
In glycolysis, glucose is converted to pyruvate in the cytoplasm
Glycolysis gives a small net gain of ATP without the use of oxygen
In aerobic cell respiration pyruvate is decarboxylated and oxidised, and converted into acetyl compound
and attached to coenzyme A to form acetyl coenzyme A in the link reaction
In the Krebs cycle, the oxidation of acetyl groups is coupled to the reduction of hydrogen carriers, liberating
carbon dioxide
Energy released by oxidation reactions is carried to the cristae of the mitochondria by reduced NAD and
FAD
Transfer of electrons between carriers in the electron transport chain in the membrane of the cristae is
coupled to proton pumping
In chemiosmosis protons diffuse through ATP synthase to generate ATP
Oxygen is needed to bind with the free protons to maintain the hydrogen gradient, resulting in the formation
of water
Analysis of diagrams of the pathways of aerobic respiration to deduce where decarboxylation and oxidation
reactions occur
8.3 Photosynthesis (Very Common Sub Topic)
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Light-dependent reactions take place in the intermembrane space of the thylakoids
Light-independent reactions take place in the stroma
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Reduced NADP and ATP are produced in the light-dependent reactions
Absorption of light by photosystems generates excited electrons
Photolysis of water generates electrons for use in the light-dependent reactions
Transfer of excited electrons occurs between carriers in thylakoid membranes
Excited electrons from Photosystem II are used to contribute to generate a proton gradient
ATP synthase in thylakoids generates ATP using the proton gradient
Excited electrons from Photosystem I are used to reduce NADP
In the light-independent reactions a carboxylase catalyses the carboxylation of ribulose bisphosphate
Glycerate-3-phosphate is reduced to triose phosphate using reduced NADP and ATP
Triose phosphate is used to regenerate RuBP and produce carbohydrates
Ribulose bisphosphate is reformed using ATP
The structure of the chloroplast is adapted to its function in photosynthesis
Calvin’s experiment to elucidate the carboxylation of RuBP
Topic 9: Plant biology
9.1 Transport in the xylem of plants
Very Common Sub Topic
Focus more on these understandings, applications and skills:
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Transpiration is the inevitable consequence of gas exchange in the leaf
Plants transport water from the roots to the leaves to replace losses from transpiration
The cohesive property of water and the structure of the xylem vessels allow transport under tension
The adhesive property of water and evaporation generate tension forces in leaf cell walls
Active uptake of mineral ions in the roots causes absorption of water by osmosis
Adaptations of plants in deserts and in saline soils for water conservation
Design of an experiment to test hypotheses about the effect of temperature or humidity on transpiration rates
Questions related to these are:
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Describe the process of transpiration.
Outline the main factors that affect transpiration.
Identify adaptations of desert and saline plants.
9.2 Transport in the phloem of plants
Least common subtopic
Focus more on these understandings, applications and skills:
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Identification of xylem and phloem in microscope images of stem and root
Analysis of data from experiments measuring phloem transport rates using aphid stylets and radioactively-labelled
carbon dioxide
Questions related to these are:
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Be able to identify xylem and phloem in microscope image.
Analyse how aphid styles and radioactively- labelled carbon dioxide are used to determine phloem transport rate.
9.3 Growth in plants
Least common subtopic
Focus more on these understandings, applications and skills:
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Plant hormones control growth in the shoot apex
Plant shoots respond to the environment by tropisms
Auxin efflux pumps can set up concentration gradients of auxin in plant tissue
Auxin influences cell growth rates by changing the pattern of gene expression
Micropropagation of plants using tissues from the shoot apex, nutrient agar gels and growth hormones
Questions related to these are:
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Explain the role of auxin in cell growth.
Outline the process of micropropagation.
9.4 Reproduction in plants
Very Common SubTopic
Focus more on these understandings, applications and skills:
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Flowering involves a change in gene expression in the shoot apex
The switch to flowering is a response to the length of light and dark periods in many plants
Success in plant reproduction depends on pollination, fertilization and seed dispersal
Most flowering plants use mutualistic relationships with pollinators in sexual reproduction
Methods used to induce short-day plants to flower out of season
Design of experiments to test hypotheses about factors affecting germination
Questions related to these are:
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Outline seed dispersal
Explain the process of fertilization.
Describe the role of phytochrome in flowering.
Explain how different factors affect germination.
Topic 10: Genetics and gene pool
10.1 Meiosis
Very Common SubTopic
Focus more on these understandings, applications and skills:
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Homologous chromosomes separate in meiosis I
Sister chromatids separate in meiosis II
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Independent assortment of genes is due to the random orientation of pairs of homologous chromosomes in meiosis I
Chiasmata formation between non-sister chromatids can result in an exchange of alleles
Crossing over is the exchange of DNA material between non-sister homologous chromatids
Crossing over produces new combinations of alleles on the chromosomes of the haploid cells
Drawing diagrams to show chiasmata formed by crossing over
Questions related to these are:
Identify the location of chiasmata in a diagram
Solve crossover problems through chromosomes diagrams.
Outline the steps of meiosis.
10.2 Inheritance
Common SubTopic
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Variation can be discrete or continuous
The phenotypes of polygenic characteristics tend to show continuous variation
Completion and analysis of Punnett squares for dihybrid traits
Polygenic traits such as human height may also be influenced by environmental factors
Calculation of the predicted genotypic and phenotypic ratio of offspring of dihybrid crosses involving unlinked
autosomal genes
Questions related to these are:
Solve dihybrid cross using punnett squares, solve for genotype and phenotype
Identify examples of polygenic trait.
10.3 Gene pools and speciation
Very Common SubTopic
Focus more on these understandings, applications and skills:
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Reproductive isolation of populations can be temporal, behavioral or geographic
Speciation due to the divergence of isolated populations can be gradual
Speciation can occur abruptly
Identifying examples of directional, stabilizing and disruptive selection
Comparison of allele frequencies of geographically isolated populations
Questions related to these are:
How are genes expressed and how they impact the biodiversity.
Explain how new species evolve.
Differentiate between directional, stabilizing and disruptive selection.
Differentiate between temporal, behavioral or geographic
Topic 11: Animal Physiology
11.1 Antibody production and vaccination
Very Common SubTopic
Focus more on these understandings, applications and skills:
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Every organism has unique molecules on the surface of its cells
Pathogens can be species-specific although others can cross species barriers
B lymphocytes are activated by T lymphocytes in mammals
Activated B cells multiply to form clones of plasma cells and memory cells
Plasma cells secrete antibodies
Antibodies aid the destruction of pathogens
White blood cells release histamine in response to allergens
Histamine causes allergic symptoms
Immunity depends on the persistence of memory cells
Fusion of a tumor cell with an antibody-producing cell creates a hybridoma cell
Monoclonal antibodies are produced by hybridoma cells
Antigens on the surface of red blood cells stimulate antibody production in a person with a different blood
group
Questions related to these are:
Explain how bacteria resist antibiotics.
Explain how antibody are produced after immune response.
Outline the steps of an allergy reaction.
Explain the production of monoclonal antibodies.
11.2 Movement
Common SubTopic
Focus more on these understandings, applications and skills:
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Muscle fibers contain many myofibrils
Each myofibril is made up of contractile sarcomeres
The contraction of the skeletal muscle is achieved by the sliding of actin and myosin filaments
ATP hydrolysis and cross bridge formation are necessary for the filaments to slide
Calcium ions and the proteins tropomyosin and troponin control muscle contractions
Antagonistic pairs of muscles in an insect leg
Drawing labeled diagrams of the structure of a sarcomere
Analysis of electron micrographs to find the state of contraction of muscle fibers
Questions related to these are:
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Describe the structure of a sarcomere.
Explain the sliding filament theory.
11.3 The kidney and osmoregulation
Very Common SubTopic
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The composition of blood in the renal artery is different from that in the renal vein
The ultrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration
The proximal convoluted tubule selectively reabsorbs useful substances by active transport
The loop of Henle maintains hypertonic conditions in the medulla
ADH controls reabsorption of water in the collecting duct
Blood cells, glucose, proteins and drugs are detected in urinary tests
Drawing and labeling a diagram of the human kidney
Annotation of diagrams of the nephron
Questions related to these are:
Identify and describe the role of each part of the nephron.
Explain the process of ultrafiltration in the glomerulus.
Outline how ADH affects reabsorption of water.
Compare and contrast the blood before and after entering the kidney.
11.4 Sexual reproduction
Very Common SubTopic
Focus more on these understandings, applications and skills:
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Spermatogenesis and oogenesis both involve mitosis, cell growth, two divisions of meiosis and
differentiation
Processes in spermatogenesis and oogenesis result in different numbers of gametes with different amounts
of cytoplasm
Fertilization in animals can be internal or external
Fertilization involves mechanisms that prevent polyspermy
Implantation of the blastocyst in the endometrium is essential for the continuation of pregnancy
hCG stimulates the ovary to secrete progesterone during early pregnancy
The placenta facilitates the exchange of materials between the mother and fetus
Estrogen and progesterone are secreted by the placenta once it has formed
Annotation of diagrams of seminiferous tubule and ovary to show the stages of gametogenesis
Questions related to these are:
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Outline acrosome reaction.
Outline how fertilization occurs in the oviduct.
What is the role of the blastocyst in pregnancy?
Identify seminiferous tubule in electron micrograph and know its role.
Explain how hormones influence menstrual cycle.
Outline the difference between spermatogenesis and oogenesis.
OPTION C: Ecology
Species and Communities
Limiting Factors:
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A factor that is the least available to suit an organisms needs
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Every organism has a range of tolerance for each factor
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Outside of its tolerances organisms cant survive (eg. Tropical plants living in Arctic)
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Factors include: temperature, soil pH, water availability, etc.
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Some animals need certain conditions to reproduce
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sites
Animal distributions can be effected by a variety of factors such as temp, food supply, breeding
Using Transects:
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Transects are a way to insure no bias in sampling of data
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Line Transect: tape is laid on the ground between two poles. Sampling is only taken of organisms
that touch the line or distance from line of samples can be recorded.
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land
Belt transects: sampling is taken between two lines separated by a set distance. Forming a belt of
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Point Transect: used to study bird populations. Researchers stand at random points and make
observations within a specified distance
Ecological models:
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Ecological models can be used to predict results
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In the optimum range there is the greatest abundance
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In zones of stress where there is too little or too much of a factor populations decrease
Niche :
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Each organism has an ecological niche
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This includes its spatial habitat, its interactions with other organisms, and how it obtains food
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For an organism to survive it needs to be in a niche that has all the right factors
Competitive Exclusion Principal:
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If two species have identical niches they cannot survive indefinitely together
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One species will over run the other, they wont both reduce equally
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Or two species will narrow there niches to avoid competition
Fundamental and realized Niches:
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Fundamental Niche: potential mode of existence given adaptations of species. Based on broadest
ranges of habitats and roles.
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Realized Niche: actual mode of existence which is a result of its adaptations and competition with
other species.
Interspecific interactions:
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There are five common interactions between species in a ecosystem
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Herbivory: Primary consumers feed on producers (cows eat grass)
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Predation: consumer eating another consumer (T-rex eats human)
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Parasitisim: When a predatory organism (called parasite) feeds off but doesn’t kill prey (called
host). (Tape worms)
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Mutualism: Two species live in close association where both benefit. (Bacteria in cows gut to help
digest grass)
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Commensalism: One organism benefits and the other is neither harmed or helped. Plants called
epiphytes live on other plants. (moss)
Zooxanthellae in ecosystems:
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Photosynthetic alga that live in coral
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Coral provides protection
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Zooxanthellae provide glucose and amino acids
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Responsible for coral colors
Local examples of interspecific interactions:
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Parasitism: Dodder, non-photosynthetic vine, invades other plant tissue and obtains nutrients from them
• Commensalism: Hawkish is immune to the effects of stinging fire corals and gains protection from them
with out harming them.
Keystone Species:
• Robert Paine first used the term to study the sea star Pisaster
• Keystone species: a species that has a disproportional effect on surrounding ecological community
• When star fish removed: other species competed for resources, three months later Barnacle Balanus
glandula became dominant, nine months later it was replaced by the barnacle Mitella and the mussel
Mytilus, Mytilus eventually became dominant which was the previous prey of the sea star, some species
left area, species diversity decreased