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| Frage | Antworten |
| Outline cell theory | 1. All living things are composed of cells 2. The cell is the smallest unit of life 3. Cells only arise from pre-existing cells |
| State that unicellular organisms carry out all the functions of life | Movement Reproduction Sensitivity Growth Respiration Excretion Nutrition |
| Relative sizes | Molecule = 1nm Cell membrane = 10 nm Virus = 100 nm Bacteria = 1 um Organelles = 10 um Eukaryotic cells = 100 um |
| Formula for magnification | Size of image (with ruler) / Actual size of object (according to scale) |
| Formula for actual size | Size of image (with ruler) / Magnification |
| Importance of surface area to volume ratio | -The rate of metabolism of a cell is a function of its volume - The rate or material exchange in and out of the cell is the function of its surface area - As the cell grows, volume increases faster than surface area (decreased ratio) |
| State that multicellular organisms show emergent properties | - Cells may group together to form tissues - Organs are then formed from the functional grouping of multiple tissues - Organs that interact may form organ systems capable of carrying out specific body functions - Organ systems carry out the life functions required by an organism |
| Explain that cells in multicellular organisms differentiate to carry out specialised functions by using some of their genes but not others | 1. - All cells of an individual organism share an identical genome - The activation of different instructions (genes) will cause it to differentiate 2. -Differentiation is the process during development whereby newly formed cells become more specialised - Differentiated cells will have different regions of DNA packaged as heterochromatin and euchromatin |
| State that stem cells retain the capacity to divide and have the ability to differentiate along different pathways | Unspecialised cells 1. Self Renewal 2. Potency |
| Outline one therapeutic use of stem cells | EDIT |
| Draw E. colli as a prokaryote cell | |
| Annotate the diagram | 1. Cell Wall - protects cell from outside environment. prevents cell from bursting if internal pressure rises 2. Plasma Membrane - Controls the substances moving in and out of the cell, through active or passive transport 3. Cytoplasm - Contains many enzymes used to catalyze chemical reactions of metabolism. Contains ribosomes and the nucleoid 4. Pili - Help bacteria adhere for the exchange of genetic material 5. Flagella - Helps bacteria move around by the use of a motor protein 6. Ribosomes - Contributes to protein synthesis by translating mRNA 7. Nucleoid - Region containing naked DNA which stores hereditary material |
| Identify structure in electron micrographs of E.Coli | |
| State that prokaryotic cells divide by binary fission | Process of binary fission - The circular DNA is copied in response to a replication signal - The two DNA loops attach the membrane - The membrane elongates and pinches off forming two separate cells |
| Draw a Liver cell as a Eukaryote cell | |
| Annotate the diagram | Ribosomes - Contributes to protein synthesis by translating mRNA Rough Endoplasmic Reticulum - Synthesises proteins to be excreted from the cell Lysosome - Contains many digestive enzymes to hydrolyse macromolecules into monomers Golgi Apparatus - Mitochondrion - Responsible for aerobic respiration. Converts chemical energy into ATP using oxygen Nucleus - Contains chromosomes and hereditary material. |
| Identify electron micrograph of liver cell | |
| Compare and Contrast Prokaryotic and Eukaryotic cells | |
| State 3 differences between plant and animal cells | |
| Outline two roles of extracellular components | 1. The plant cell wall gives the cell strength and prevents it from bursting under high pressure - made up of cellulose arranged in groups called microfibrils. 2. The animal cell contains glycoproteins in their extracellular matrix which are involved in support, movement and adhesion of the cell. |
| Draw diagram of the structure of membranes | |
| Explain how the hydrophobic and hydrophilic properties of phospholipids help to maintain the structure of cell membranes | Hydrophilic heads will face the water while the hydrophobic tails will be in the center as they face away from the water. The phospholipid bilayer makes the membrane stable but also allows flexibility. The phospholipid in the membrane are in a fluid state which allows the cell to change it's shape easily. |
| List the functions of membrane proteins | 1. Hormone binding sites 2. Electron carriers 3. Pumps for active transport 4. Channels for passive transport 5. Enzymes |
| Define Diffusion | The passive movement of particles from a region of high concentration to a region of low concentration |
| Define Osmosis | The passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration |
| Explain passive transport across membranes by simple and facilitated diffusion | Simple diffusion involves the diffusion of molecules through the phospholipid bilayer while facilitated diffusion involves the use of channel proteins embedded in the membrane. The cell membrane is hydrophobic inside so hydrophobic (lipid soluble) molecules will pass through by simple diffusion whereas hydrophilic molecules and charged particles will use facilitated diffusion. |
| Explain the role of protein pumps and ATP active transport across membranes | Active transport involves the movement of substances through the membrane using energy from ATP. The advantage of active transport is that substances can be moved against the concentration gradient, meaning from a region of low concentration to a region of high concentration. This is possible because the cell membrane has protein pumps embedded it which are used in active transport to move substances across by using ATP. Each protein pump only transports certain substances so the cell can control what comes in and what goes out. |
| Explain how vesicles are used to transport materials within a cell between the rough endoplasmic reticulum, Golgi apparatus and plasma membrane. | - After proteins have been synthesized by ribosomes they are transported to the rough endoplasmic reticulum where they can be modified. -Vesicles carrying the protein then bud off the rough endoplasmic reticulum and are transported to the Golgi apparatus to be further modified. - After this the vesicles carrying the protein bud off the Golgi apparatus and carry the protein to the plasma membrane. Here the vesicles fuse with the membrane expelling their content (the modified proteins) outside the cell. - The membrane then goes back to its original state. This is a process called exocytosis. - Endocytosis is a similar process which involves the pulling of the plasma membrane inwards so that the pinching off of a vesicle from the plasma membrane occurs and then this vesicle can carry its content anywhere in the cell. |
| Describe how the fluidity of the membrane allows it to change shape, break and re-form during endocytosis and exocytosis. | The phospholipids in the membrane are in a fluid state allowing the membrane to change shape and also allows vesicles to fuse with it. - substances can enter the cell via endocytosis and exit the cell by exocytosis - The membrane then returns to its original state - exocytosis the vesicles fuse with the membrane expelling their content outside the cell - The membrane then goes back to its original state - Endocytosis is a similar process which involves the pulling of the plasma membrane inwards so that a vesicle is pinched off it and then this vesicle can carry its content anywhere in the cell. |
| Outline the stages of the cell cycle including Interphase (G1, S, G2), mitosis and cytokinesis | Interphase : G1- cell grows larger and matures S - genome is replicated G2 - prepares for division Mitosis: - The periods of nuclear division Cytokinesis: - The period of cytoplasmic division |
| State that tumours (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue | Tumors are formed when cell division goes wrong and is no longer controlled. This can happen in any organ or tissue. |
| State 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 | Interphase is an active period in the life of a cell during which many metabolic reactions occur such as protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplast. |
| Describe the events that occur in the four stages of mitosis | Prophase - the spindle microtubules grow and extend from each pole to the equator. - chromosomes super coil and become short and bulky and the nuclear envelope breaks down. Metaphase - the chromatids move to the equator and the spindle microtubules from each pole attach to each centromere on opposite sides Anaphase - the spindle microtubules pull the sister chromatids apart splitting the centromeres. This splits the sister chromatids into chromosomes. Each identical chromosome is pulled to opposite poles Telophase - he spindle microtubules break down and the chromosomes uncoil and so are no longer individually visible - the nuclear membrane reforms - The cell then divides by cytokinesis to form two daughter cells with identical genetic nuclei |
| Diagram of mitosis | |
| Explain how mitosis produces two genetically identical nuclei | - During interphase (the S phase) the DNA was replicated to produce two copies of genetic material -These two identical DNA molecules are identified as sister chromatids and are held together by a single centromere -During the events of mitosis, the sister chromatids are separated and drawn to opposite poles of the cell -When the cell divides (cytokinesis), the two resulting nuclei will each contain one of each chromatid pair and thus be genetically identical |
| State that growth, embryonic development, tissue repair and asexual reproduction involve mitosis | Growth: Multicellular organisms increase their size by increasing their number of cells through mitosis Asexual reproduction: Certain eukaryotic organisms may reproduce asexually by mitosis (e.g. vegetative reproduction) Tissue Repair: Damaged tissue can recover by replacing dead or damaged cells Embryonic development: A fertilised egg (zygote) will undergo mitosis and differentiation in order to develop into an embryo |
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| State the most frequently occurring chemical elements in living organisms | -Carbon -Hydrogen -Oxygen -Nitrogen |
| State the variety of elements that are needed by any living organism | -Sulphur -Calcium -Phosphorus -Iron -Sodium |
| State one role of each of the elements mentioned | Sulphur (S): Found in certain amino acids (cysteine and methionine), allowing proteins to form disulphide bonds Calcium (Ca): Found in bones and teeth, also involved in neurotransmitter release in synapses Phosphorus (P): Component of nucleic acids and cell membranes Iron (Fe): Found in haemoglobin (animals), allowing for oxygen transport Sodium (Na): Involved in the generation of nerve impulses in neurons |
| Structure and bonding of water molecules | |
| Outline the thermal, cohesive and solvent properties of water | 1. Thermal properties - water as a high specific heat capacity - water has a high heat of vaporisation - water has a high heat of fusion 2. Cohesive properties - water molecules are strongly cohesive - water molecules tend to stick to charged or polar molecules 3. Solvent properties - water dissolves many organic and inorganic substances that contain electronegative atoms 4. Other properties - water is transparent allowing light to pass through (important for photosynthesis |
| Explain the relationship between the properties of water and its use in living organisms as a coolant, medium for metabolic reactions and transport medium | -Water can evaporate at temperatures below the boiling point. Hydrogen bonds need to break for this to occur. -The evaporation of water cools body surfaces (sweat) and plant leaves (transpiration) by using the energy from liquid water to break the hydrogen bonds. --The solvent properties of water mean that many different substances can dissolve in it because of its polarity. This allows substances to be carried in the blood and sap of plants as they dissolve in water. It also makes water a good medium for metabolic reactions. |
| Distinguish between organic and inorganic compounds | Organic compounds - compound that are found in living organisms and contain carbon. Inorganic compounds - compounds found in living organisms that do not contain carbon.- EXCEPTION- carbon dioxide, carbonates |
| Identify glucose and ribose | |
| List 3 examples of monosaccharides, disaccharides, polysaccharides | Monosaccharides - Glucose, galactose, fructose Disaccharides - Lactose, maltose, sucrose Polysaccharides - Cellulose, glycogen, starch |
| State one function of glucose, lactose and glycogen in animals, and of fructose, sucrose and cellulose in plants | 1. Animals Glucose: A source of energy which can be broken down to form ATP via cellular respiration Lactose: A sugar found in the milk of mammals, providing energy for suckling infants Glycogen: Used by animals for short term energy storage (between meals) in the liver 2. Plants Fructose: Found in honey and onions, it is very sweet and a good source of energy Sucrose: Used primarily as a transportable energy form (e.g. sugar beets and sugar cane) Cellulose: Used by plant cells as a strengthening component of the cell wall |
| Outline the role of condensation and hydrolysis in the relationship between monosaccharides, disaccharides and polysaccharides | |
| Identify fatty acids from diagrams showing their structure | |
| State 3 functions of lipids | 1. Lipids can be used for energy storage in the form of fat in humans and oil plants 2. Lipids can be used as heat insulation as fat under the skin reduces heat loss 3. Lipids allow buoyancy as they are less dense than water |
| Compare the use of carbohydrates and lipids in energy storage | |
| Outline DNA nucleotide structure in terms of sugar (deoxyribose), base and phosphate | |
| State the names of the four bases in DNA | 1. Adenine 2. Thymine 3. Guanine 4. Cytosine |
| Explain how a DNA double helix is formed using complementary base pairing and hydrogen bonds | Two polynucleotide chains of DNA are held together by hydrogen bonds between complementary base pairs. Thymine + Adenine, Cytosine + Guanine |
| Draw an label a simple diagram of the molecular structure of DNA | |
| Explain DNA replication in terms of unwinding of the double helix and separation of the strands by helicase, followed by the formation of the new complementary strands by DNA polymerase | Helicase Unwinds the DNA and separates the two polynucleotide strands by breaking the hydrogen bonds between complementary base pairs The two separated polynucleotide strands act as templates for the synthesis of new polynucleotide strands DNA Polymerase Synthesises new strands from the two parental template strands Free deoxynucleoside triphosphates (nucleotides with three phosphate groups) are aligned opposite their complementary base partner and are covalently bonded together by DNA polymerase to form a complementary nucleotide chain The energy for this reaction comes from the cleavage of the two extra phosphate groups |
| Explain the significance of complementary base pairing in the conservation of the base sequence of DNA | This is because adenine always pairs up with thymine and guanine always pairs up with cytosine. As DNA replication is semi-conservative (one old strand an d one new strand make up the new DNA molecules), this complementary base pairing allows the two DNA molecules to be identical to each other as they have the same base sequence. The new strands formed are complementary to their template strands but also identical to the other template. Therefore, complementary base pairing has a big role in the conservation of the base sequence of DNA. |
| State that DNA is semi-conservative | DNA replication is semi-conservative |
| Compare the structure of RNA and DNA | |
| Outline DNA transcription in terms of the formation of an RNA strand complementary to the DNA strand by RNA polymerase | - DNA transcription is the formation of an RNA strand which complementary to the DNA strand. 1. First stage, is the uncoiling of the DNA double helix 2. Second stage, free RNA nucleotides start to form RNA by using one of DNA strands as template - base thymine is replaced by uracil 3. The RNA strand then elongates and then separates from the DNA template. The DNA strands then reform a double helix. The strand of RNA formed is called messenger RNA. |
| Describe the genetic code in terms of codons composed of triplets of bases | A triplet of bases (3 bases) forms a codon. Each codon codes for a particular amino acid. Amino acids in turn link to form proteins. Therefore DNA and RNA regulate protein synthesis. The genetic code is the codons within DNA and RNA, composed of triplets of bases which eventually lead to protein synthesis. |
| Explain the process of translation, leading to polypeptide formation | -Ribosomes bind to mRNA in the cell's cytoplasm and move along the mRNA molecule in a 5' - 3' direction until it reaches a start codon (AUG) -Anticodons on tRNA molecules align opposite appropriate codons according to complementary base pairing (e.g. UAC will align with AUG) -Each tRNA molecule carries a specific amino acid (according to the genetic code) -Ribosomes catalyse the formation of peptide bonds between adjacent amino acids (via a condensation reaction) -The ribosome moves along the mRNA molecule synthesising a polypeptide chain until it reaches a stop codon, at this point translation stops and the polypeptide chain is released |
| Discuss the relationship between one gene and one polypeptide. | A polypeptide is formed by amino acids liking together through peptide bonds. There are 20 different amino acids so a wide range of polypeptides are possible. Genes store the information required for making polypeptides. The information is stored in a coded form by the use of triplets of bases which form codons. The sequence of bases in a gene codes for the sequence of amino acids in a polypeptide. The information in the genes is decoded during transcription and translation leading to protein synthesis. |
| Define enzyme and active site | Enzyme - Globular proteins which act as catalysts of chemical reactions Active site - the site on the surface of an enzyme which binds to the substrate molecule |
| Explain enzyme substrate specificity | Active site and substrate complement each other in terms of both shape and chemical properties (e.g. opposite charges) Binding to the active site brings the substrate into close physical proximity, creating an enzyme-substrate complex The enzyme catalyses the conversion of the substrate into a product (or products), creating an enzyme-product complex As the enzyme is not consumed in the reaction, it can continue to work once the product dissociates (hence only low concentrations are needed) Enzyme-Substrate Specificity Lock and Key Model Enzymes and substrates share specificity (a given enzyme will only interact with a small number of specific substrates that complement the active site) This explanation of enzyme-substrate interaction is described as the 'lock and key' model (a lock only opens in response to a specific key) |
| Explain the effects of temperature, pH and substrate concentration on enzyme activity | Temperature - Low temperatures result in insufficient thermal energy for the activation of a given enzyme-catalysed reaction to be achieved. - Increasing the temperature will increase the speed and motion of both enzyme and substrate, resulting in higher enzyme activity. - At an optimal temperature (may differ for different enzymes), the rate of enzyme activity will be at its peak - Higher temperatures will cause enzyme stability to decrease, as the thermal energy disrupts the hydrogen bonds holding the enzyme together pH - Changing the pH will alter the charge of the enzyme, which in turn will protein solubility and may change the shape of the molecule -Changing the shape or charge of the active site will diminish its ability to bind to the substrate, abrogating enzyme function -Enzymes have an optimum pH (may differ between enzymes) and moving outside of this range will always result in a diminished rate of reaction Substrate concentration - Increasing substrate concentration will increase the activity of a particular enzyme |
| Factors affecting enzyme activity | |
| Define denaturation | Changing the structure of an enzyme so it can no longer carry out its function |
| Explain the use of lactase in the production of lactose-free milk | Lactose is the sugar found in milk that can be broken down by the enzyme lactase into glucose and galactose. Lactose intolerant people lack this enzyme and cannot break down lactose. Lactose-free milk can be made in two ways: 1. Adding the lactase enzyme to the milk so that the milk contains the enzyme. 2. Immobilising the enzyme on a surface or in beads of porous material. The milk is then allowed to flow past the beads or surface with immobilised lactase, preventing lactase in the milk. |
| Define cell respiration | Cell respiration is the controlled release of energy from organic compounds in cels to form ATP |
| State that, in cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP | In cell respiration, glucose in the cytoplasm is broken down by glycolysis into pyruvate, with a small yield of ATP |
| Explain 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 | The conversion of pyruvate occurs in the cytoplasm of the cell and the products are: Lactate (3C) in animal cells Ethanol (2C) and carbon dioxide (CO2) in plants, fungi (e.g. yeast) and bacteria The conversion of pyruvate into ethanol and CO2 is also known as fermentation |
| Anaerobic respiration | |
| Explain that, during aerobic cell respiration, pyuvate can be broken down in the mitochondrion into carbon dioxide and water with a large yield of ATP | Aerobic respiration occurs in the presence of oxygen and takes place in the mitochondrion Pyruvate is broken down into carbon dioxide and water and a large amount of ATP is formed (34 - 36 molecules) Although this process begins with glycolysis (to break down glucose into pyruvate), glycolysis does not require oxygen and is an anaerobic process |
| Anaerobic vs. aerobic respiration | |
| State that photosynthesis involves the conversion of light energy into chemical energy | Photosynthesis is a two step process: 1. The light dependent reactions convert the light energy into chemical energy (ATP) 2. The light independent reactions use the chemical energy to synthesise organic compounds (e.g. glucose) The organic molecules produced in photosynthesis can be used in cellular respiration to provide the energy needed by the organism |
| State that light from the Sun is composed of a range of wavelengths | The light from the sun is composed of a range of wavelengths |
| State that chlorophyll is the main photosynthetic pigment | Chlorophyll is the main photosynthetic pigment |
| Outline the differences in absorption of red, blue and green light by chlorophyll | Absorbs red and blue more than green. Chlorophyll can not absorb green light and so instead reflects it making leaves look green. |
| State that light energy is used to produce ATP and to split water molecules to form oxygen and hydrogen | Light energy is used to produce ATP and to split water molecules (photolysis) to form oxygen and hydrogen |
| State that ATP and hydrogen (derived from the photolysis of water) are used to fix carbon molecules to make organic molecules | ATP and hydrogen derived from photolysis of water are used to fix carbon dioxide to make organic molecules |
| Explain 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 | Measuring CO2 Uptake CO2 uptake can be measured by placing a plant in an enclosed space with water Carbon dioxide interacts with the water molecules, producing bicarbonate and hydrogen ions, which increases the acidity of the resulting solution The change in pH can therefore provide a measure of CO2 uptake by a plant (increased CO2 uptake = more alkaline pH) Measuring O2 Production O2 production can be measured by submerging a plant in an enclosed space with water attached to a sealed gas syringe Any oxygen gas produced will bubble out of solution and can be measured by a change in water level (via the position of the meniscus) Measuring Biomass (Indirect) Glucose production can be indirectly measured by a change in a plant's biomass (weight) This requires the plant to be completely dehydrated prior to weighing to ensure the change in biomass reflects a change in organic matter and not water content An alternative method for measuring glucose production is to determine the change in starch levels in a plant (glucose is stored as starch) |
| Outline the effect of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis | Temperature- Photosynthesis is controlled by enzymes, which are sensitive to temperature As temperature increases, the rate of photosynthesis will increase as reagents have greater kinetic energy and are more likely to react Above a certain temperature, the rate of photosynthesis will decrease as essential enzymes begin to denature Light intensity- As light intensity increases, the rate of photosynthesis will increase up until a certain point, when photosynthesis is proceeding at its maximum rate Further increases to light intensity will have no effect on photosynthesis (the rate will plateau), as chlorophyll are saturated by light Different wavelengths of light will have different effects on the rate of photosynthesis (e.g. green light will not be used) Carbon dioxide concentration - As the concentration of carbon dioxide increases, the rate of photosynthesis will increase up until a certain point, when photosynthesis is proceeding at its maximum rate |
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| State that eukaryotic chromosomes are made of DNA and protein | Eukaryotic chromosomes are made of DNA and protein |
| Define gene | A heritable factor that controls a specific characteristic, consisting of a length of DNA occupying a particular position on a chromosome (locus) |
| Define allele | One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same locus as other alleles of the gene |
| Define genome | The whole of the genetic information of an organism |
| Define gene mutation | A change in the nucleotide sequence of a section of DNA coding for a particular feature |
| Explain the consequence of a base substitution mutation in relation to the process of transcription and translation using the example of sickle cell anaemia | A base substitution mutation is the change of a single base in a sequence of DNA, resulting in a change to a single mRNA codon during transcription In the case of sickle cell anaemia, the 6th codon for the beta chain of haemoglobin is changed from GAG to GTG (on the non-coding strand) This causes a change in the mRNA codon (GAG to GUG), resulting in a single amino acid change of glutamic acid to valine (Glu to Val) • DNA: GAG to GTG (non-coding strand) • mRNA: GAG to GUG • Amino Acid: Glu to Val The amino acid change alters the structure of haemoglobin, causing it to form fibrous, insoluble strands This causes the red blood cell to adopt a sickle shape Consequences of Sickle Cell Anaemia The insoluble haemoglobin cannot effectively carry oxygen, causing individual to feel constantly tired The sickle cells may accumulate in the capillaries and form clots, blocking blood supply to vital organs and causing a myriad of health problems Also causes anaemia (low RBC count) |
| State that meiosis is a reduction division of a diploid nucleus to form haploid nuclei | Meiosis is a reduction division of a diploid nucleus to form haploid nuclei |
| Define homologous chromosomes | homologous chromosomes are chromosomes that share: The same structural features The same genes at the same loci positions |
| Outline the process of meiosis, including pairing of homologous chromosomes and crossing over, followed by two divisions, which results in four haploid cells | |
| Explain that non-disjunction can lead to a change in chromosome number, illustrated by reference to Down syndrome (trisomy 21) | Non-disjunction refers to the chromosomes failing to separate correctly, resulting in gametes with one extra, or one missing, chromosome (aneuploidy) The failure of the chromosomes to separate may either occur via: Failure of homologues to separate during Anaphase I (resulting in four affected daughter cells) Failure of sister chromatids to separate during Anaphase II (resulting in two affected daughter cells) Individuals with Down syndrome have three copies of chromosome 21 (trisomy 21) One of the parental gametes had two copies of chromosome 21 as a result of non-disjunction The other parental gamete was normal and had a single copy of chromosome 21 When the two gametes fused during fertilisation, the resulting zygote had three copies of chromosome 21, leading to Down syndrome |
| State that, in karyotyping, chromosomes are arranged in pairs according to their structure | Karyotyping is arranging the chromosomes in pairs according to their size and structure |
| State that karyotyping is performed using cells collected by chorionic villus sampling or amniocentesis, for pre-natal diagnosis of chromosome abnormalities | Karyotyping is performed using cells collected by chorionic villus sampling (CVS) or amniocentesis, for prenatal diagnosis of chromosome abnormalities |
| Analyse a human karyotype to determine gender and whether non-disjunction has occurred | Healthy = 2 chromosomes per number Not Healthy = 3 chromosomes per number |
| Define Genotype | The allele combination of an organism |
| Define Phenotype | The characteristics of an organism (determined by a combination of genotype and environmental factors) |
| Define dominant allele | An allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state |
| Define Recessive allele | An allele that only has an effect on the phenotype when present in the homozygous state |
| Define codominant alleles | Pairs of alleles that both affect the phenotype when present in a heterozygote |
| Define locus | The particular position on homologous chromosomes of a gene |
| Define homozogous | Having two identical alleles of a gene |
| Define heterozogous | Having two different alleles of a gene |
| Define Carrier | An individual that has one copy of a recessive allele that causes a genetic disease in individuals that are homozygous for this allele |
| Define Test Cross | Testing a suspected heterozygote by crossing it with a known homozygous recessive |
| Determine the genotypes and phenotypes of the offspring of a monohybrid cross using a Punnett grid | |
| State that some genes have more than two alleles (multiple alleles) | Some genes have more than two alleles. This is called multiple alleles. |
| Describe ABO blood groups as an example of codominance and multiple alleles | |
| Explain how sex chromosomes control gender by referring to the inheritance of X and Y chromosomes in humans | The 23rd pair of chromosomes are heterosomes (or sex chromosomes) and determine gender Females are XX - they possess two X chromosomes Males are XY - they posses one X chromosome and a much shorter Y chromosome The Y chromosome contains the genes for developing male sex characteristic - hence the father is always responsible for determining gender If the male sperm contains the X chromosome the growing embryo will develop into a girl If the male sperm contains a Y chromosome the growing embryo will develop into a boy In all cases the female egg will contain an X chromosome (as the mother is XX) Because the X and Y chromosomes are of a different size, they cannot undergo crossing over / recombination during meiosis This ensures that the gene responsible for gender always remains on the Y chromosome, meaning that there is always ~ 50% chance of a boy or girl |
| State that some genes are present on the X chromosome and absent from the shorter Y chromosome | Some genes are present on the X chromosome and absent from the shorter Y chromosome |
| Define sex linkage | Sex linkage refers to when a gene controlling a characteristic is found on a sex chromosome (and so we associate the trait with a predominant gender) Sex-linked conditions are usually X-linked, as very few genes exist on the shorter Y chromosome |
| Describe the inheritance of colour blindness and haemophilia as examples of sex linkage | |
| State that a human female can be homozygous or heterozygous with respect to sex-linked genes | A human female can be homozygous or heterozygous with respect to sex-linked genes. |
| Explain that female carriers are heterozygous for X-linked recessive alleles | An individual with a recessive allele for a disease condition that is masked by a normal dominant allele is said to be a carrier Carriers are heterozygous and can potentially pass the trait on to the next generation, but do not suffer from the defective condition themselves Females can be carriers for X-linked recessive conditions because they have two X chromosomes - males (XY) cannot be carriers Because a male only inherits an X chromosome from his mother, his chances of inheriting the disease condition from a carrier mother is greater |
| Predict the genotypic and phenotypic ratios of offspring of monohybrid crosses involving any of the above patterns of inheritance | |
| Deduce the genotype and phenotype of individuals in pedigree charts | Squares represent males Circles represent females Shaded symbols represent affected individuals Unshaded symbols represent unaffected individuals. If most of the males in the pedigree are affected the disorder is X-linked. If it is a 50/50 ratio between men and women the disorder is autosomal. If the disorder is dominant, one of the parents must have the disorder. If the disorder is recessive than neither of the parents has to have the disorder as they can be heterozygous. |
| Outline the use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA. | PCR is a way of producing large quantites of a specific target sequence of DNA It is useful when only a small amount of DNA is avaliable for testing E.g. crime scene samples of blood, semen, tissue, hair, etc. PCR occurs in a thermal cycler and involves a repeat procedure of 3 steps: 1. Denaturation: DNA sample is heated to separate it into two strands 2. Annealing: DNA primers attach to opposite ends of the target sequence 3. Elongation: A heat-tolerant DNA polymerase (Taq) copies the strands |
| State that, in gel electrophoresis, fragments of DNA can move in an electric field and are separated according to their size | In gel electrophoresis, fragments of DNA move in an electrical field and are separated according to their size. |
| State that gel electrophoresis of DNA is used in DNA profiling | Gel electrophoresis of DNA is used in DNA profiling. |
| Describe the application of DNA profiling to determine paternity and also in forensic investigation | A DNA sample is collected (blood, saliva, semen, etc.) and amplified using PCR Satellite DNA (non-coding) is cut with specific restriction enzymes to generate fragments Individuals will have unique fragment lengths due to the variable length of their short tandem repeats (STR) The fragments are separated with gel electrophoresis (smaller fragments move quicker through the gel) The DNA profile can then be analysed according to need Two applications of DNA profiling are: Paternity testing (comparing DNA of offspring against potential fathers) Forensic investigations (identifying suspects or victims based on crime-scene DNA) |
| Analyse DNA profiles to draw conclusions about paternity or forensic investigations | |
| Outline three outcomes of the sequencing of the complete human genome | Mapping: We now know the number, location and basic sequence of human genes Screening: This has allowed for the production of specific gene probes to detect sufferers and carriers of genetic disease conditions Medicine: With the discovery of new proteins and their functions, we can develop improved treatments (pharmacogenetics and rational drug design) Ancestry: It will give us improved insight into the origins, evolution and historical migratory patterns of humans |
| State that, when genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal | When genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal. |
| Outline a basic technique used for gene transfer involving plasmids, a host cell (bacterium, yeast or other cell), restriction enzymes (endonucleases) and DNA ligase | 1. DNA Extraction A plasmid is removed from a bacterial cell (plasmids are small, circular DNA molecules that can exist and replicate autonomously) A gene of interest is removed from an organism's genome using a restriction endonuclease which cut at specific sequences of DNA The gene of interest and plasmid are both amplified using PCR technology 2. Digestion and Ligation The plasmid is cut with the same restriction enzyme that was used to excise the gene of interest Cutting with certain restriction enzymes may generate short sequence overhangs ("sticky ends") that allow the the two DNA constructs to fit together The gene of interest and plasmid are spliced together by DNA ligase creating a recombinant plasmid 3. Transfection and Expression The recombinant plasmid is inserted into the desired host cells (this is called transfection for eukaryotic cells and transformation for prokaryotic cells) The transgenic cells hopefully produce the desired trait encoded by the gene of interest The product need to subsequently be isolated from the host and purified |
| State two examples of current uses of genetically modified crops or animals | The transfer of a gene for factor IX which is a blood clotting factor, from humans to sheep so that this factor is produced in the sheep’s milk. The transfer of a gene that gives resistance to the herbicide glyphosate from bacterium to crops so that the crop plants can be sprayed with the herbicide and not be affected by it. |
| Discuss the potential benefits and potential harmful effects of one example of genetic modification | |
| Define clone | A clone is a group of genetically identical organisms or a group of cells derived from a single parent cell |
| Outline a technique for cloning using differentiated animal cells | Somatic Cell Nuclear Transfer (SCNT) is a method of reproductive cloning using differentiated animal cells A female animal (e.g. sheep) is treated with hormones (such as FSH) to stimulate the development of eggs The nucleus from an egg cell is removed (enucleated), thereby removing the genetic information from the cell The egg cell is fused with the nucleus from a somatic (body) cell of another sheep, making the egg cell diploid An electric shock is delivered to stimulate the egg to divide, and once this process has begun the egg is implanted into the uterus of a surrogate The developing embryo will have the same genetic material as the sheep that contributed the diploid nucleus, and thus be a clone |
| Discuss the ethical issues of therapeutic cloning in humans. | |
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| Define species | A group of organisms that can interbreed and produce fertile, viable offspring |
| Define Habitat | The environment in which a species normally lives or the location of a living organism |
| Define Population | A group of organisms of the same species who live in the same area at the same time |
| Define Community | A group of populations living and interacting with each other in an area |
| Define Ecosystem | A community and its abiotic environment |
| Define Ecology | The study of relationships between living organisms and between organisms and their environment |
| Distinguish between autotroph and heterotroph | Autotroph: An organism that synthesises its organic molecules from simple inorgance substances (e.g. CO2 and nitrates) - autotrophs are producers Heterotroph: An organism that obtains organic molecules from other organisms - heterotrophs are consumers |
| Distinguish between consumers, detritivores and saprotrophs | Consumer: An organism that ingests other organic matter that is living or recently killed Detritivore: An organism that ingests non-living organic matter Saprotroph: An organism that lives on or in non-living organic matter, secreting digestive enzymes into it and absorbing the products of digestion |
| Decribe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms) | |
| Describe what is meant by a food web | A food web is a diagram that shows all the feeding relationships in a community with arrows which show the direction of the energy flow. |
| Define Trophic Level | Trophic level: the trophic level of an organism is its position in the food chain. Producers, primary consumers, secondary consumers and tertiary consumers are examples of trophic levels. |
| Deduce the trophic levels of organisms in a food web and food chain | Plants or any other photosynthetic organisms are the producers. Primary consumers are the species that eat the producers. Secondary consumers are the species that eat the primary consumers and tertiary consumers in turn eat the secondary consumers. |
| Construct a food web containing up to 10 organisms, using appropriate information | |
| State that light is the initial energy source for almost all communities | Light is the initial energy source for almost all communities. |
| Explain the energy flow in a food chain | |
| tate that energy transformations are never 100% efficient | Energy transformations are never 100% efficient. |
| Explain the reason for the shape of pyramids of energy | A pyramid of energy is a graphical representation of the amount of energy of each tropic level in a food chain They are expressed in units of energy per area per time (e.g. kJ m2 year -1) Pyramids of energy will never appear inverted as some of the energy stored in one source is always lost when transferred to the next source This is an application of the second law of thermodynamics Each level of the pyramid of energy should be approximately one tenth the size of the level preceding it, as energy transformations are ~10% efficient |
| Explain that energy enters and leaves ecosystems, but nutrients must be recycled | 1. Energy is not recycled. Constantly being supplied to the ecosystem through light energy. 2. Energy is lost from the ecosystem in the form of heat through cell respiration. 3. Nutrients must be recycled as there is only a limited supply of them. 4. They are absorbed by the environment, used by organisms and then returned to the environment. |
| State that saprotrophic bacteria and fungi (decomposers) recycle nutrients | Saprotrophic bacteria and fungi (decomposers) recycle nutrients. |
| Draw and label a diagram of the carbon cycle to show the processes involved. | |
| Analyse the changes in concentration of atmospheric carbon dioxide using historical records | Atmospheric carbon dioxide concentrations have been measured at the Mauna Loa atmospheric observatory in Hawaii from 1958 and has since been measured at a number of different locations globally The data shows that there is an annual cycle in CO2 concentrations which may be attributable to seasonal factors, but when data from the two hemispheres is incorporated, it suggests that atmospheric CO2 levels have risen steadily in the past 30 years Carbon dioxide concentration changes over a long period of time have been determined by a variety of sources, including analysing the gases trapped in ice (and thus providing a historical snapshot of atmospheric concentrations) Data taken from the Vostok ice core in Antarctica shows that fluctuating cycles of CO2 concentrations over thousands of years appear to correlate with global warm ages and ice ages It is compelling to note that CO2 levels appear to be currently higher than at any time in the last 400,000 years |
| Explain the relationship between the rises in concentrations of atmospheric carbon dioxide, methane and oxides of nitrogen and the enhanced greenhouse effect | 1.The incoming radiation from the sun is short wave ultraviolet and visible radiation. 2.Some of this radiation is absorbed by the earths atmosphere. 3.Some of the radiation is reflected back into space by the earths surface. 4.The radiation which is reflected back into space is infrared radiation and has a longer wavelength. 5.The greenhouse gases in the atmosphere absorbe some of this infrared radiation and re-reflect it back towards the earth. 6.This causes the green house effect and results in an increase in average mean temperatures on earth. 7.A rise in greenhouse gases results in an increase of the green house effect which can be disastrous for the planet. |
| Outline the precautionary principle | The precautionary principle holds that, if the effects of a human-induced change would be very large, perhaps catastrophic, those responsible for the change must prove that it will not do harm before proceeding. This is the reverse of the normal situation, where those who are concerned about the change would have to prove that it will do harm in order to prevent such changes going ahead. |
| Evaluate the precautionary principle as a justification for strong action in response to the threats posed by the enhanced greenhouse effect. | |
| Outline the consequences of a global temperature rise on arctic ecosystems | |
| Outline how population size is affected by natality, immigration, mortality and emigration | Natality: Increases to population size through reproduction (i.e. births) Immigration: Increases to population size from external populations Mortality: Decreases to population size as a result of death (e.g. predation, senescence) Emigration: Decreases to population size as a result of loss to external populations |
| Draw and label a graph showing a sigmoid (S-shaped) population growth curve. | |
| Explain reasons for the exponential growth phase, the plateau phase and the transitional phase between these two phases | |
| List three factors that set limits to population increase. | 1. Shortage of resources (e.g. food) 2. Increase in predators 3. Increase in diseases and parasites |
| Define Evolution | Evolution is the cumulative change in the heritable characteristics of a population |
| Outline the evidence for evolution provided by the fossil record, selective breeding of domesticated animals and homologous structures | - Fossil evidence may be either: The totality of fossils (both discovered and undiscovered) is known as the fossil record The fossil record reveals that, over time, changes have occurred in features of organisms living on the planet (evolution) Moreover, different kinds of organisms do not occur randomly but are found in rocks of particular ages in a consistent order (law of fossil succession) This suggests that changes to an ancestral species was likely responsible for the appearance of subsequent species (speciation via evolution) Furthermore, the occurrence of transitional fossils demonstrate the intermediary forms that occurred over the evolutionary pathway taken within a single genus -Selective breeding of domesticated animals is an example of artificial selection, which occurs when man directly intervenes in the breeding of animals to produce desired traits in offspring As a result of many generations of selective breeding, domesticated breeds can show significant variation compared to the wild counterparts, demonstrating evolutionary changes in a much shorter time |
| Continuation of ANSWER | - Comparative anatomy of groups of animals or plants shows certain structural features are basically similar, implying a common ancestry Homologous structures are those that are similar in shape in different types of organisms despite being used in different ways An example is the pentadactyl limb structure in vertebrates, whereby many animals show a common bone composition, despite the limb being used for different forms of locomotion (e.g. whale fin for swimming, bat wing for flying, human hand for manipulating tools, horse hoof for galloping, etc.) This illustrates adaptive radiation (divergent evolution) as a similar basic plan has been adapted to suit various environmental niches The more similar the homologous structures between two species are, the more closely related they are likely to be |
| State that populations tend to produce more offspring than the environment can support | Populations tend to produce more offspring than the environment can support. |
| Explain that the consequence of the potential overproduction of offspring is a struggle for survival | If the mortality rate remains lower than the natality rate then a population will keep growing. As more offspring are produced, there will be less resources available to other members of the population. If there is an over production of offspring this will result in a struggle for survival within the species as the resources become scarce and individuals in the population will start to compete for these. This results in an increase in mortality rate as the weaker individuals in the population will lose out on these vital resources that are essential for their survival. |
| State that members of a species show variation | Members of a species show variation |
| Explain how reproduction promotes variation within a species | There are two stages in sexual reproduction that promote variation in a species. The first one is during meiosis during which a large variety of genetically different gametes are produced by each individual. The second stage is fertilisation. Here, alleles from two different individuals are brought together to form one new individual. |
| Explain how natural selection leads to evolution | The theory of natural selection was postulated by Charles Darwin (and also independently by Alfred Wallace) who described it as 'survival of the fittest' There is genetic variation within a population (which can be inherited) There is competition for survival (populations tend to produce more offspring than the environment can support) Environmental selective pressures lead to differential reproduction Organisms with beneficial adaptations will be more suited to their environment and more likely to survive to reproduce and pass on their genes Over generations there will be a change in allele frequency within a population (evolution) |
| Explain two examples of evolution in response to environmental change; one must be antibiotic resistance in bacteria. | |
| Outline the binomial system of nomenclature | Species are a group of organisms with similar characteristics which can interbreed and produce fertile offspring whereas a genus is a group of similar species. Species need an international name and so biologists name them using the binomial system of nomenclature. Each species is given two names. The first is the genus name and is given an upper case first letter. The second is the species name and is given a lower case first letter. If the name is printed, italics are used. If on the other hand the name is hand-written, it is underlined. |
| List the seven levels in the hierarchy of taxa - kingdom, phylum, class, order, family, genus and species - using an example from two different kingdoms for each level | |
| Distinguish between the following phyla of plants, using simple external recognition features: bryophyta, filicinophyta, coniferophyta and angiospermophyta | |
| Distinguish between the following phyla of animals, using simple external recognition features: porifera, cnidaria, platyhemlnthes, annelida, mollusca and arthropoda | |
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| Explain why digestion of large food molecules is essential | 1. As food was synthesised by other organisms, it contains materials not suitable for human tissue - these need to be separated and removed 2. Large molecules need to be broken down into smaller molecules that can be readily absorbed across membranes and into cells 3. Small molecules can be reassembled into new products (e.g. amino acids can be reassembled to make new proteins) |
| Explain the need for enzymes in digestion | 1. Enzymes break down large food molecules into smaller ones. 2. Speed up the process of digestion by lowering the activation energy for the reaction. 3. Work at body temperature. |
| State the source, substrate, product and optimal pH conditions for one amylase, one protease and one lipase | |
| Draw and label a diagram of the human digestive system | |
| Outline the function of the stomach, small intestine and large intestine | |
| Distinguish between absorption and assimilation | Absorption: The movement of a fluid or dissolved substances across a membrane Assimilation: The conversion of nutrients into fluid or solid parts of an organism |
| Explain how the structure of the villus is related to its role in absorption and transport of products of digesti | |
| Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves and the route of blood through the heart | |
| State that coronary arteries supply heart muscle with oxygen and nutrients | Coronary arteries supply heart muscles with oxygen and nutrients |
| Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves. | |
| Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline) | |
| Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline) | |
| Explain the relationship between the structure and function of arteries, capillaries and veins | |
| State that blood is composed of plasma, erythrocytes, leukocytes (phagocytes and lymphocytes) and platelets | Blood is composed of plasma, erythrocytes, leukocytes (phagocytes and lymphocytes) and platelets |
| State that the following are transported by blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat | Nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat are all transported by the blood. |
| Define pathogen | A pathogen is a disease-causing micro-organism, virus or prion |
| Explain why antibiotics are effective against bacteria but not against viruses | Antibiotics block specific metabolic pathways in bacteria. Bacteria are very different to human cells so human cells are not affected. Viruses require host cell to carry metabolic processes for them and so antibiotics cannot be used to treat viruses. Harming the virus would harm the human cells. |
| Outline the role of skin and mucous membranes in defence against pathogens | Skin Protects external structures (outer body areas) A dry, thick and tough region made of predominantly dead surface cells Contains biochemical defence agents (sebaceous glands secrete chemicals which inhibit the growth of some bacteria) The skin also releases acidic secretions to lower pH and prevent bacteria from growing Mucous membranes Protect internal structures (externally accessable cavities and tubes, such as trachea, vagina and urethra) A thin region containing living surface cells that release fluids to wash away pathogens (mucus, tears, saliva, etc.) Contains biochemical defence agents (secretions contain lysozyme, which can destroy cell walls and cause cell lysis) Mucous membranes may be ciliated to aid in the removal of pathogens (along with physical actions such as coughing or sneezing) |
| Outline how phagocytic leucocytes ingest pathogens in the blood and in body tissue | Phagocytes are found in the blood and ingest pathogens. They do so by recognising pathogens and engulfing them by endocytosis. Enzymes within the phagocytes called lysosomes then digest the pathogens. Phagocytes can ingest pathogens in the blood but also within body tissue as they can pass through the pores of capillaries and into these tissues. |
| Distinguish between antigens and antibodies | Antigen: A substance that the body recognises as foreign and that can evoke an immune response Antibody: A protein produced by certain white blood cells (B lymphocytes, plasma cells) in response to an antigen |
| Explain antibody production | |
| Outline the effect of HIV on the immune system | The human immunodeficiency virus (HIV) is a retrovirus that infects helper T lymphcytes (TH cells) Reverse transciptase allows viral DNA to be produced from its RNA code, which is integrated into the host cells genome After a number of years of inactivity (during which infected TH cells have continually reproduced), the virus becomes active and begins to spread, destroying the TH cells in the process (known as the lysogenic cycle) This results in lower immunity as antibody production is compromised - the individual is now susceptible to opportunistic infections |
| Discuss the cause, transmission and social implications of AIDS | |
| Distinguish between ventilation, gas exchange and cell respiration | Ventilation: The exchange of air between the lungs and the atmosphere; it is achieved by the physical act of breathing Gas exchange: The exchange of oxygen and carbon dioxide in the alveoli and the bloodstream; it occurs passively via diffusion Cell Respiration: The release of ATP from organic molecules; it is greatly enhanced by the presence of oxygen (aerobic respiration) |
| Explain the need for a ventilation system | |
| Describe the features of alveoli that adapt them to gas exchange | |
| Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli. | |
| Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles. | |
| State that the nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that carry rapid electrical impulses | The nervous system consists of the central nervous system (CNS) and peripheral nerves, and is composed of cells called neurons that carry rapid electrical impulses |
| Draw and label a diagram of the structure of the motor neuron | |
| State that nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons | Nerve impulses are conducted from receptors to the CNS by sensory neurons, within the CNS by relay neurons, and from the CNS to effectors by motor neurons. |
| Define resting potential and action potential (depolarisation and repolarisation) | Resting Potential: The charge difference across the membrane when a neuron is not firing (-70 mV), as maintained by the sodium-potassium pump Action Potential: The charge difference across the membrane when a neuron is firing (about 30 mV) Depolarisation: The change from a negative resting potential to a positive action potential (caused by opening of sodium channels) Repolarisation: The change from a positive action potential back to a negative resting potential (caused by opening of potassium channels) |
| Explain how a nerve impulse passes along a non-myelinated neuron | |
| Explain the principles of synaptic transmission | |
| State that the endocrine system consists of glands that release hormones that are transported in the blood | The endocrine system consists of glands that release hormones that are transported in the blood. |
| State that homeostasis involves maintaining the internal environment between limits, including blood pH, carbon dioxide concentration, blood glucose concentration, body temperature and water balance | Homeostasis involves maintaining the internal environment between limits, including blood pH, carbon dioxide concentration, blood glucose concentration, body temperature and water balance |
| Explain that homeostasis involves monitoring levels of variables and correcting changes in levels by negative feedback mechanisms | Most homeostatic control mechanisms operate through a negative feedback loop When specialised receptors detect a change in an internal condition, the response generated will be the opposite of the change that occurred When levels have returned to equilibrium, the effector ceases to generate a response If levels go too far in the opposite direction, antagonistic pathways will be activated to restore the internal balance |
| Explain the control of body temperature, including the transfer of heat in blood, and the roles of the hypothalamus, sweat glands, skin arterioles and shivering. | |
| Explain the control of blood glucose concentration, including the roles of glucagon, insulin and α and β cells in the pancreatic islets. | |
| Distinguish between type I and type II diabetes | |
| Draw and label diagrams of the adult male and female reproductive systems | |
| Outline the role of hormones in the menstrual cycle, including FSH (follicle stimulating hormone), LH (luteinising hormone), estrogen and progesterone | |
| Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormone levels and ovulation, menstruation and the thickening of the endometrium | |
| List three roles of testosterone in males | 1. Pre-natal development of male genitalia 2. Development of secondary sex characteristics 3. Maintenance of sex drive (libido) |
| Outline the process of in vitro fertilization (IVF) | |
| Discuss the ethical issues associated with IVF |
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