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A Science teacher by trade, I've also been known to be found teaching Maths and PE! However, strange as it may seem, my real love is designing resources that can be used by other teachers to maximise the experience of the students. I am constantly thinking of new ways to engage a student with a topic and try to implement that in the design of the lessons.

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A Science teacher by trade, I've also been known to be found teaching Maths and PE! However, strange as it may seem, my real love is designing resources that can be used by other teachers to maximise the experience of the students. I am constantly thinking of new ways to engage a student with a topic and try to implement that in the design of the lessons.
Triglycerides, saturated & unsaturated lipids (Edexcel Int. A-level Biology)
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Triglycerides, saturated & unsaturated lipids (Edexcel Int. A-level Biology)

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This fully-resourced lesson describes how a triglyceride is synthesised and describes the differences between saturated and unsaturated lipids. The engaging PowerPoint and accompanying resources have been designed to cover specification points 1.5 (i) & (ii) as detailed in the Edexcel International A-level Biology specification and links are also made to related future topics such as the use of lipids as a substrate for respiration and the importance of the myelin sheath for the conduction of an electrical impulse. The lesson begins with a focus on the basic structure and roles of lipids, including the elements that are found in this biological molecule and some of the places in living organisms where they are found. Moving forwards, the students are challenged to recall the structure of the carbohydrates from earlier in topic 1 so that the structure of a triglyceride can be introduced. Students will learn that this macromolecule is formed from one glycerol molecule and three fatty acids and have to use their understanding of condensation reactions to draw the final structure. Time is taken to look at the difference in structure and properties of saturated and unsaturated fatty acids and students will be able to identify one from the other when presented with a molecular formula. The final part of the lesson explores how the various properties of lipids mean that these molecules have numerous roles in organisms including that of an energy store and source and as an insulator of heat and electricity.
Topic 3: Cell structure, Reproduction & Development (Edexcel International A-level Biology)
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Topic 3: Cell structure, Reproduction & Development (Edexcel International A-level Biology)

12 Resources
The locus and linkage, meiosis, differential gene expression and protein transport within cells lessons have been uploaded for free and by downloading these, you will be able to observe the detail of planning that has gone into all of the lessons that are included in this bundle. This intricate planning ensures that the students are engaged and motivated whilst the detailed content of topic 3 (Cell structure, Reproduction and Development) of the Edexcel International A-level Biology specification is covered. The 12 lesson PowerPoints and accompanying resources contain a wide range of activities which cover the following topic 3 specification points: All living organisms are made of cells Cells of multicellular organisms are organised into tissues, organs and organ systems The ultrastructure of eukaryotic cells The function of the organelles in eukaryotic animal cells The role of the RER and Golgi apparatus in protein transport within cells The ultrastructure of prokaryotic cells Magnification and resolution in light and electron microscopes The gene locus is the location of a gene on a chromosome The linkage of genes on a chromosome The role of meiosis in ensuring genetic variation Understand how the mammalian gametes are specialised for their functions The role of mitosis and the cell cycle in growth and asexual reproduction The meaning of the terms stem cell, pluripotent, totipotent, morula and blastocyst The decisions that have to be made about the use of stem cells in medical therapies Cells become specialised through differential gene expression One gene can give rise to more than one protein through post-transcriptional changes to mRNA Phenotype is the interaction between genotype and the environment Some phenotypes are affected by multiple alleles or by polygenic inheritance Due to the detail included in all of these lessons, it is estimated that it will take in excess of 6 weeks of allocated A-level teaching time to complete the teaching of the bundle
Polygenic inheritance (Edexcel Int. A-level Biology)
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Polygenic inheritance (Edexcel Int. A-level Biology)

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This fully-resourced lesson describes how polygenic inheritance gives rise to phenotypes that show continuous variation. The engaging PowerPoint and accompanying resources have been primarily designed to cover points 3.20 (i) & 3.21 of the Edexcel International A-level Biology specification but also includes activities to challenge the students on previous concepts in topics 3 and 2. The students begin the lesson by having to identify phenotype and species from their respective definitions so that a discussion can be encouraged where they will recognise that phenotypic variation within a species is due to both genetic and environmental factors. The main part of the the lesson focuses on these genetic factors, and describes how mutation and the events of meiosis contribute to this variation. A range of activities, which include exam-style questions and quick quiz rounds, are used to challenge the students on their knowledge and understanding of substitution mutations, deletions, insertions, the genetic code, crossing over and independent assortment. Moving forwards, the concept of multiple alleles is introduced and students will learn how the presence of more than 2 alleles at a locus increases the number of phenotypic variants. Another quick quiz round is used to introduce polygenic inheritance and the link is made between this inheritance of genes at a number of loci as an example of continuous variation. The final part of the lesson describes a few examples where environmental factors affect phenotype, such as chlorosis in plants. As this is the final lesson in topic 3, the numerous activities can be used for revision purposes and to demonstrate the links between different biological topics.
Post-transcriptional changes to mRNA (Edexcel Int. A-level Biology)
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Post-transcriptional changes to mRNA (Edexcel Int. A-level Biology)

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This fully-resourced lesson describes how post-transcriptional changes to mRNA enable 1 gene to give rise to multiple proteins. The detailed PowerPoint and accompanying resources have been designed to cover point 3.19 of the Edexcel International A-level Biology specification. The lesson begins with a knowledge recall as the students have to recognise the definition of a gene as a sequence of bases on a DNA molecule that codes for a sequence of amino acids in a polypeptide chain. This description was introduced in topic 2 and the aim of the start of the lesson is to introduce the fact that despite this definition, most of the nuclear DNA in eukaryotes doesn’t actually code for proteins. A quick quiz competition is then used to introduce exons as the coding regions within a gene before students are challenged to predict the name of the non-coding regions and then to suggest a function for these introns. Moving forwards, pre-mRNA as a primary transcript is introduced and students will learn that this isn’t the mature strand that moves off to the ribosome for translation. Instead, a process called splicing takes place where the introns are removed and the remaining exons are joined together. Another quick quiz round leads to an answer of 20000 and students will learn that this is the number of protein-coding genes in the human genome. Importantly, the students are then told that the number of proteins that are synthesised is much higher than this value and a class discussion period encourages them to come up with biological suggestions for this discrepancy between the two numbers. The lesson concludes with a series of understanding and application questions where students will learn that alternative splicing enables a gene to produce more than a single protein and that this natural phenomenon greatly increases biodiversity.
Differential gene expression (Edexcel Int. A-level Biology)
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Differential gene expression (Edexcel Int. A-level Biology)

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This fully-resourced lesson describes how cells become specialised through differential gene expression. The PowerPoint and accompanying resources have been designed to cover the details of point 3.19 of the Edexcel International A-level Biology specification. This is one of the more difficult concepts in this A-level course and therefore key points are reiterated throughout this lesson to increase the likelihood of student understanding and to support them when trying to make links to actual biological examples in living organisms. There is a clear connection to transcription and translation as covered in topic 2, so the lesson begins by reminding students that in addition to the structural gene in a transcription unit, there is the promotor region where RNA polymerase binds. Students are introduced to the idea of transcription factors and will understand how these molecules can activate or repress transcription by enabling or preventing the binding of the enzyme. At this point, students are challenged on their current understanding with a series of questions about DELLA proteins so they can see how these molecules prevent the binding of RNA polymerase. The final section of the lesson looks at one further example with oestrogen and the ER receptor and explains how the binding of this chemical results in the release of the inhibitor and the production of active mRNA.
The role of mitosis & the cell cycle (Edexcel Int. A-level Biology)
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The role of mitosis & the cell cycle (Edexcel Int. A-level Biology)

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This fully-resourced lesson describes the role of mitosis and the cell cycle in producing genetically identical daughter cells. The detailed PowerPoint and accompanying resources have been designed to cover point 3.14 of the Edexcel International A-level Biology specification and explains the importance of these cells for growth and asexual reproduction. In an earlier lesson covering meiosis (3.10), students were introduced to the different phases and structures involved in the cycle so this lesson builds on that by providing greater detail of the key events in each phase. Beginning with a focus on interphase, the importance of DNA replication is explained so that students can initially recognise that there are pairs of identical sister chromatids and then can understand how they are separated later in the cycle. A quiz competition has been written into the lesson and this runs throughout, challenging the students to identify the quantity of DNA in the cell (in terms of n) at different points of the cycle. The main part of the lesson focuses on prophase, metaphase, anaphase and telophase and describes how the chromosomes behave in these stages. Students will understand how the cytoplasmic division that occurs in cytokinesis results in the production of genetically identical daughter cells. This leads into a series of understanding and application questions where students have to identify the various roles of mitosis in living organisms as well as tackling a Maths in a Biology context question. The lesson concludes with a final round of MITOSIS SNAP where they only shout out this word when a match is seen between the name of a phase, an event and a picture.
Meiosis ensures genetic variation (Edexcel Int. A-level Biology)
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Meiosis ensures genetic variation (Edexcel Int. A-level Biology)

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This detailed lesson describes how the crossing over of alleles and the independent assortment in meiosis contribute to genetic variation. The PowerPoint and accompanying resource have been designed to cover specification point 3.10 of the Edexcel International A-level Biology specification and includes describes how the fertilisation of the haploid gametes that were formed by meiosis increases variation further. In order to understand how the events of meiosis like crossing over and random assortment and independent segregation can lead to variation, students need to be clear in their understanding that DNA replication in interphase results in homologous chromosomes as pairs of sister chromatids. Therefore the beginning of the lesson focuses on the chromosomes in the parent cell and this first part of the cycle and students will be introduced to non-sister chromatids and the fact that they may contain different alleles which is important for the exchange that occurs during crossing over. Time is taken to go through this event in prophase I in a step by step guide so that the students can recognise that the result can be new combinations of alleles that were not present in the parent cell. Moving forwards, the lesson explores how the independent segregation of chromosomes and chromatids during anaphase I and II results in genetically different gametes. The final part of the lesson looks at the use of a mathematical expression to calculate the possible combinations of alleles in gametes as well as in a zygote following the random fertilisation of haploid gametes. Understanding and prior knowledge checks are interspersed throughout the lesson as well as a series of exam questions which challenge the students to apply their knowledge to potentially unfamiliar situations.
Gene locus and linkage (Edexcel Int. A-level Biology)
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Gene locus and linkage (Edexcel Int. A-level Biology)

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This clear and concise lesson describes the meaning of a gene locus and explains how the inheritance of two or more genes that have loci on the same chromosome demonstrates linkage. The engaging PowerPoint and associated resource have been designed to cover points 3.9 (i) and (ii) of the Edexcel International A-level Biology specification and makes clear links to the upcoming topic of meiosis when describing the effect of crossing over on this linkage This is a topic which can cause confusion for students so time was taken in the design to split the concept into small chunks. There is a clear focus on how the number of original phenotypes and recombinants can be used to determine linkage and suggest how the loci of the two genes compare. Important links to other topics such as crossing over in meiosis are made to enable students to understand how the random formation of the chiasma determines whether new phenotypes will be seen in the offspring or not. Linkage is an important cause of variation and the difference between observed and expected results and this is emphasised on a number of occasions. The main task of the lesson acts as an understanding check where students are challenged to analyse a set of results involving the inheritance of the ABO blood group gene and the nail-patella syndrome gene to determine whether they have loci on the same chromosome and if so, how close their loci would appear to be.
Magnification & resolution (Edexcel Int. A-level Biology)
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Magnification & resolution (Edexcel Int. A-level Biology)

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This fully-resourced lesson describes how magnification and resolution can be achieved using light and electron microscopy. The engaging PowerPoint and accompanying resources have been designed to cover the content of points 3.7 (i) & (ii) of the Edexcel International A-level Biology specification and also considers how specimens are stained. To promote engagement and focus throughout this lesson, the PowerPoint contains a quiz competition with 7 rounds. The quiz rounds found in this lesson will introduce the objective lens powers, the names of the parts of a light microscope and emphasise some of the other key terms such as resolution. The final round checks on their understanding of the different numbers that were mentioned in the lesson, namely the differing maximum magnifications and resolutions. Time is taken to explain the meaning of both of these microscopic terms so that students can recognise their importance when considering the organelles that were met earlier in topic 3. By the end of the lesson, the students will be able to explain how a light microscope uses light to form an image and will understand how electrons transmitted through a specimen or across the surface will form an image with a TEM or a SEM respectively.
Ultrastructure of prokaryotic cells (Edexcel Int. A-level Biology)
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Ultrastructure of prokaryotic cells (Edexcel Int. A-level Biology)

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This fully-resourced lesson describes the ultrastructure of a prokaryotic cell and the function of the structures found in these cells. The engaging PowerPoint and accompanying resources have been designed to cover specification point 3.5 (i) & (ii) as detailed in the Edexcel International A-level Biology specification and also compares these cells against the eukaryotic cells that were met in the previous lesson. A clear understanding of terminology is important for A-level Biology so this lesson begins with a challenge, where the students have to recognise a prefix that they believe translates as before or in front of . This leads into the discovery of the meaning of prokaryote as before nucleus and this acts to remind students that these types of cell lack this cell structure. Links to the previous lessons on the eukaryotic cells are made throughout the lesson and at this particular point, the students are asked to work out why the DNA would be described as naked and to state where it will be found in the cell. Moving forwards, the students will discover that these cells also lack membrane bound organelles and a quick quiz competition challenges them to identify the specific structure that is absent from just a single word. In addition to the naked DNA, students will learn that there are also ribosomes in the cytoplasm and will discover that these are smaller than those found in the cytoplasm of an eukaryotic cell (but the same size as those in chloroplasts and mitochondria). The remainder of the lesson focuses on the composition of the cell wall, the additional features of prokaryotic cells such as plasmids and there is also the introduction of binary fission as the mechanism by which these organisms reproduce
Eukaryotic cells (Edexcel Int. A-level Biology)
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Eukaryotic cells (Edexcel Int. A-level Biology)

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This fully-resourced lesson describes the ultrastructure of eukaryotic cells and the functions of each of the organelles in these cells. The engaging and detailed PowerPoint and accompanying resources have been designed to cover points 3.1, 3.2 & 3.3 of the Edexcel International A-level Biology specification and therefore this lesson also describes how all living organisms are made of cells and that these cells are organised into tissues, organs and organ system in multicellular organisms. As cells are the building blocks of living organisms, it makes sense that they would be heavily involved in all of the 8 topics in the Edexcel course and intricate planning has ensured that links to previously covered topics as well as upcoming ones are made throughout the lesson. The cell theory is introduced at the start of the lesson and the first 2 principles are explained. Students will see how epithelial cells are grouped together to form different types of epithelium in the respiratory tract and their prior knowledge of gas exchange at the alveoli from topic 2 is tested with a series of questions. The rest of the lesson uses a wide range of activities, that include exam-style questions, class discussion points and quick quiz competitions, to maintain motivation and engagement whilst describing the relationship between the structure and function of the following organelles: nucleus nucleolus centrioles ribosomes rough endoplasmic reticulum Golgi apparatus lysosomes smooth endoplasmic reticulum mitochondria cell surface membrane All of the worksheets have been differentiated to support students of differing abilities whilst maintaining challenge Due to the detail that is included in this lesson, it is estimated that it will take in excess of 3 hours of allocated A-level teaching time to go through all of the tasks
Glycogen, amylose and amylopectin (Edexcel Int. A-level Biology)
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Glycogen, amylose and amylopectin (Edexcel Int. A-level Biology)

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This detailed and fully-resourced lesson describes the relationship between the structure and function of glycogen and amylose and amylopectin as components of starch. The engaging PowerPoint and accompanying resources have been designed to cover the fourth part of points 1.2 & 1.4 of the Edexcel International A-level Biology specification and links are continuously made to the previous lessons in this topic where the monosaccharides and disaccharides were introduced. The lesson begins with the CARBOHYDRATE WALL where students have to use their prior knowledge to collect the 9 carbohydrates on show into 3 groups. This results in glycogen, starch and cellulose being grouped together as polysaccharides and the structure and roles of the first two are covered over the course of the lesson. Cellulose is covered in a lesson in topic 4. Students will learn how key structural features like the 1 - 4 and 1 - 6 glycosidic bonds and the hydrogen bonds dictate whether the polysaccharide chain is branched or unbranched and also allows for spiralling. Following the description of the structure of glycogen, students are challenged to design an exam question in the form of a comparison table so that it can be completed as the lesson progresses and they learn more about starch. This includes a split in the starch section of the table so that the differing structures and properties of amylose and amylopectin can be considered. The importance of the compact structure for storage is discussed as well as the branched chains of amylopectin acting as quick source of energy when it is needed. The lesson concludes with a question and answer section that guides the students when answering a question about the importance of the lower solubility of the polysaccharides when compared to the monosaccharides.
Disaccharides (Edexcel Int. A-level Biology)
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Disaccharides (Edexcel Int. A-level Biology)

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This lesson describes how monosaccharides are joined together during condensation reactions to form maltose, sucrose and lactose. The PowerPoint and accompanying resource have been designed to cover the third part of point 1.2 & 1.4 of the Edexcel International A-level Biology specification but also make links to the previous lesson on monosaccharides when considering the different components of these three disaccharides. The first section of the lesson focuses on a prefix and a suffix so that the students can recognise that the names of the common disaccharides end in -ose. In line with this, a quick quiz round is used to introduce maltose, sucrose and lactose before students are challenged on their prior knowledge as they have to describe how condensation reactions and the formation of glycosidic bonds were involved in the synthesis of each one. The main task of the lesson again challenges the students to recall details of a previous lesson as they have to identify the monomers of each disaccharide when presented with the displayed formula. Time is taken to show how their knowledge of these simple sugars will be important in later topics such as digestion, translocation in the phloem and the Lac Operon in the control of gene expression. The lesson finishes with two exam-style questions where students have to demonstrate and apply their newly acquired knowledge and the mark schemes are included within the lesson PowerPoint so students can assess their understanding and address any misconceptions if they have arisen.
Structure of monosaccharides (Edexcel Int. A-level Biology)
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Structure of monosaccharides (Edexcel Int. A-level Biology)

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This fully-resourced lesson describes the relationship between the structure of monosaccharides and their roles in living organisms. The engaging PowerPoint and accompanying resources have been designed to cover the second part of points 1.2 & 1.4 of the Edexcel International A-level Biology specification and describes alpha-glucose, galactose, fructose, deoxyribose and ribose. The lesson begins by reminding students that monosaccharides are the simplest sugars and that these monomers provide energy. Using the molecular formula of glucose as a guide, students will be given the general formula for the monosaccharides and will learn that deoxyribose is an exception to the rule that the number of carbon and oxygen atoms are equal. Moving forwards, students have to study the displayed formula of glucose for two minutes without being able to note anything down before they are challenged to recreate what they saw in a test of their observational skills. At this point of the lesson, the idea of numbering the carbons is introduced so that the different glycosidic bonds can be understood in an upcoming lesson as well as the recognition of the different isomers of glucose. The difference between alpha and beta-glucose is provided but students do not need to consider the beta form until topic 4. The remainder of the lesson focuses on the roles of the monosaccharides and the final task involves a series of application questions where the students are challenged to suggest why ribose could be considered important for active transport and muscle contraction
The difference between monosaccharides, disaccharides & polysaccharides
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The difference between monosaccharides, disaccharides & polysaccharides

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This lesson describes the differences between monosaccharides, disaccharides and polysaccharides, including glycogen and starch. The PowerPoint and accompanying resource have been designed to cover point 1.2 (i) of the Edexcel International A-level Biology specification and the main aim of the lesson is to prepare the students for the upcoming lessons on the individual carbohydrate groups. The lesson begins with a made-up round of the quiz show POINTLESS, where students have to try to identify four answers to do with carbohydrates. In doing so, they will learn or recall that these molecules are made from carbon, hydrogen and oxygen, that they are a source of energy which can sometimes be rightly or wrongly associated with obesity and that the names of the three main groups is derived from the Greek word sakkharon. A number of quick quiz rounds have been written into the lesson to introduce key terms in a fun and memorable way and the first round allows the students to meet some of common monosaccharides. Moving forwards, students will learn that a disaccharide is formed when two of these monomers are joined together and they are then challenged on their knowledge of condensation reactions which were originally encountered during the lesson on water. Students will understand how multiple reactions and multiple glycosidic bonds will result in the formation of a polysaccharide and glycogen and starch are introduced as well as amylose and amylopectin as components of this latter polymer.
Edexcel Int. A-level Biology Topic 2: Membranes, Proteins, DNA and Gene expression
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Edexcel Int. A-level Biology Topic 2: Membranes, Proteins, DNA and Gene expression

20 Resources
Hours and hours of planning have gone into each and every lesson that’s included in this bundle to ensure that the students are engaged and motivated whilst the detailed content of topic 2 of the Edexcel International A-level Biology specification is covered. Membranes, proteins, DNA and gene expression represent some of the most important structures, molecules and processes involved in this subject and a deep understanding of their role in living organisms is important for a student’s success. The 20 lesson PowerPoints and accompanying resources contain a wide range of activities which cover the following topic 2 specification points: Know the properties of gas exchange surfaces in living organisms Understand how the rate of diffusion can be calculated using Fick’s Law of Diffusion Understand how the structure of the mammalian lung is adapted for rapid gas exchange The structure and properties of cell membranes The movement of free water molecules by osmosis The movement across membranes by passive and active transport The role of channel and carrier proteins in membrane transport The basic structure of an amino acid The formation of polypeptides and proteins The structure of proteins The mechanism of action and specificity of enzymes Enzymes are biological catalysts Intracellular and extracellular enzymes The basic structure of mononucleotides The structure of DNA and RNA The process of DNA replication The nature of the genetic code A gene as a sequence of bases on DNA that codes for a sequence of amino acids The process of transcription and translation Errors in DNA replication give rise to mutations Mutations give rise to disorders but many mutations have no observable effect The meaning of key genetic terms Understanding the pattern of monohybrid inheritance Sex linkage on the X chromosome Understand how the expression of a gene mutation in people with cystic fibrosis impairs the functioning of the gaseous exchange, digestive and reproductive systems The uses and implications of genetic screening and prenatal testing Due to the detail included in all of these lessons, it is estimated that it will take in excess of 2 months of allocated A-level teaching time to complete the teaching of the bundle If you would like to sample the quality of these lessons, then download the rapid gas exchange, osmosis, DNA & RNA, genetic code, genetic terms and cystic fibrosis lessons as these have been uploaded for free.
Passive transport (Edexcel Int. A-level Biology)
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Passive transport (Edexcel Int. A-level Biology)

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This lesson describes how molecules move across cell membranes by passive transport, as exemplified by simple and facilitated diffusion. The PowerPoint and accompanying resource have been designed to cover the first part of specification point 2.5 of the Edexcel International A-level Biology specification and the factors that increase the rate of diffusion are covered along with the limitations imposed by the phospholipid bilayer and the role of channel and carrier proteins The structure and properties of cell membranes were described in the lesson covering 2.2, so this lesson has been written to include continual references to the content of that lesson. This enables links to be made between the movement across a cell membrane with the concentration gradient, the parts of the membrane that are involved and any features that may increase the rate at which the molecules move. A quick quiz competition challenges students to recall Fick’s law of diffusion and a series of questions and tasks are used to demonstrate how a large surface area, a short diffusion distance and the maintenance of a steep concentration gradient will increase the rate of simple diffusion. Another quick quiz round is then used to introduce temperature and size of molecule as two further factors that can affect simple diffusion. The remainder of the lesson focuses on facilitated diffusion and describes how transmembrane proteins are needed to move small, polar or large molecules from a high concentration to a lower concentration across a partially permeable membrane
Rapid gas exchange (Edexcel Int. A-level Biology)
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Rapid gas exchange (Edexcel Int. A-level Biology)

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This lesson describes how the structure of the mammalian lung is adapted for rapid gaseous exchange. The engaging PowerPoint has been designed to cover point 2.1 (iii) of the Edexcel International A-level Biology specification and focuses on the essential features of the alveolar epithelium as well as the mechanism of ventilation to maintain a steep concentration gradient for the simple diffusion of oxygen and carbon dioxide. Gas exchange at the alveoli is a topic that was covered at GCSE and considered during the previous lessons in topic 2.1 so this lesson has been written to challenge the recall of that knowledge and to build on it. The main focus of the first half of the lesson is the type of epithelium found lining the alveoli and students will discover that a single layer of flattened cells known as simple, squamous epithelium acts to reduce the diffusion distance. The following features of the alveolar epithelium are also covered: Surface area Moist lining Production of surfactant The maintenance of a steep concentration gradient is the role of the respiratory system and the next part of the lesson focuses on the diaphragm and intercostal muscles. As the mechanism of inhalation is a cascade of events, the details of this process are covered in a step by step format using bullet points. At each step, time is taken to discuss the key details which includes an introduction to Boyle’s law that reveals the inverse relationship between volume and pressure. It is crucial that students are able to describe how the actions of the diaphragm, external intercostal muscles and ribcage result in an increased volume of the thoracic cavity and a subsequent decrease in the pressure, which is below the pressure outside of the body. At this point, their recall of the structures of the mammalian gas exchange system is tested, to ensure that they can describe the pathway the air takes on moving into the lungs.
Sex-linkage (Edexcel Int. A-level Biology)
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Sex-linkage (Edexcel Int. A-level Biology)

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This fully-resourced lesson describes the inheritance of genes with loci on the X chromosomes and considers biological examples. The detailed PowerPoint and accompanying resources have been designed to cover point 2.15 (ii) of the Edexcel International A-level specification and focuses on the inheritance of red-green colour blindness and haemophilia in humans Key genetic terminology is used throughout and the lesson begins with a check on their ability to identify the definition of homologous chromosomes. Students will recall that the sex chromosomes are not fully homologous and that the smaller Y chromosome lacks some of the genes that are found on the X. This leads into one of the numerous discussion points, where students are encouraged to consider whether females or males are more likely to suffer from sex-linked diseases. In terms of humans, the lesson focuses on haemophilia and red-green colour blindness and a step-by-step guide is used to demonstrate how these specific genetic diagrams should be constructed and how the phenotypes should then be interpreted. The final task of the lesson challenge the students to apply their knowledge to an exam question about chickens and how the rate of feather production in chicks can be used to determine gender. All of the tasks are differentiated so that students of differing abilities can access the work and all exam questions have fully-explained, visual mark schemes to allow them to assess their progress and address any misconceptions
Patterns of inheritance (Edexcel Int A-level Biology)
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Patterns of inheritance (Edexcel Int A-level Biology)

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This fully-resourced lesson uses step by step guides to walk students through the interpretation of genetic pedigree diagrams for monohybrid inheritance. The PowerPoint and accompanying resources have been designed to cover point 2.15 (ii) of the Edexcel International A-level Biology specification and includes the inheritance when there are more than two alleles at a gene locus as well as those that demonstrate codominance. In order to minimise the likelihood of errors and misconceptions, the guides that are included within the lesson will support the students with the following: Writing parent genotypes Working out the different gametes that are made following meiosis Interpreting Punnett crosses to work out phenotypic ratios Students can often find pedigree trees the most difficult to interpret and to explain so exemplar answers are used and the worksheets are differentiated so students can seek assistance if necessary.