4.6.1.1 animals and pollen and ovule cells in flowering plants. This mixing of genetic information leads to variation in the offspring. Gametes are produced by meiosis. Asexual reproduction involves only one parent and no fusion of gametes. There is no mixing of genetic information. This leads to genetically identical offspring (clones). Only mitosis is involved. Describe cuttings as clones of plants. (See 4.6.2.5 Cloning) do hermaphrodites lead a solitary existence? Watch BBC video clips of fertilisation in humans and pollination of flowers (see resources). Observe exhibition showing asexual reproduction in different organisms. Give examples of sexual and asexual reproduction in different organisms. View the BBC guide to sexual and asexual reproduction (see resources). carrot top growing on damp blotting paper potato sprouting spider plant producing runners bulb amoeba yeast. 4.6.1.2 Meiosis. Cells in reproductive Explain the term gametes and describe their genetic material. 1 Consider fusion of sex cells at fertilisation and explain why gametes have only one set of Use bio-viewers, video clips or images to show Mitosis and meiosis: Knowledge and understanding of the
organs divide by meiosis to form gametes. When a cell divides to form gametes: copies of the genetic information are made and the cell divides twice to form four gametes, each with a single set of chromosomes. All gametes are genetically different from each other. Gametes join at fertilisation to restore the normal number of chromosomes. The new cell divides by mitosis, and as the embryo develops cells differentiate. Explain why sexual reproduction results in variety. Draw diagrams to explain how gametes are formed in meiosis. Explain the number of chromosomes in the gametes during meiosis and fertilisation. Describe how an embryo is formed. Compare mitosis and meiosis (links with 4.1.2.1 and 4.1.2.2). chromosomes – use models or diagrams. Make models to show what happens during fertilisation (‘Play-Doh’ is ideal) – this could be extended to a stop frame animation if ICT is available. Watch BBC video clip and access information on mitosis and meiosis (see resources). Produce a poster to compare mitosis and meiosis. chromosomes and meiosis. stages in meiosis are not required.
4.6.1.3 4.6.1.3 Advantages and disadvantages of sexual and asexual reproduction. Advantages of sexual: produces variation survival advantage if the environment changes used in selective breeding to produce organisms with desired characteristics. Advantages of asexual reproduction: only one parent needed time and energy efficient as do Describe advantages and disadvantages of sexual and asexual reproduction. Describe some organisms that can reproduce by both methods: malarial parasites reproduce asexually in the human host, and sexually in the mosquito many fungi reproduce asexually by spores, but asexually to produce variation many plants reproduce sexually to produce seeds and asexually by runners, eg strawberry plants, or bulb division, eg daffodils. 0.5 –1 Brainstorm advantages and disadvantages of sexual and asexual reproduction and report outcomes in a table or mind map. Research organisms that can reproduce both sexually and asexually and produce an illustrated report. Identify links to other areas of the specification, eg selective breeding, variation, evolution, bacteria, cloning.
chromosomes are the same (XX); in males the chromosomes are different (XY). Use a Punnett square and a genetic cross diagram to illustrate the inheritance of sex; evaluate the chance of producing a male or female. 4.6.1.4 DNA. DNA is a polymer made up of two strands forming a double helix. DNA is found in chromosomes. A gene is a small section of DNA. Each gene codes for a sequence of amino acids to form a particular protein. The genome is all the genetic material of an organism. The human genome has been studied and will be Describe the structure of chromosomes, DNA and genes. Explain that a gene is a small section of DNA that codes for a particular sequence of amino acids to make a specific protein. Describe what the genome is. Explain how knowledge of the human genome will help medicine in the future, eg identifying genes linked to cancers, understanding and treating inherited disorders. It will also help trace human migration patterns. Explain the ethical issues related to DNA sequencing. 1 Recap key ideas by asking students to reorder by size: cell, nucleus, DNA, chromosome, gene, nucleotide. Debate: research and discuss ‘DNA profiling’ for health. Research roles of Franklin, Watson and Crick in the discovery of the structure of DNA. Demo or practical to extract DNA. Appreciate the and limitations of science and consider any ethical issues. Extract DNA from fruits such as onions or kiwi fruit. Observe the long strands which are the polymer. Ethical issues:
important for medicine in the future. 4.6.1.5 DNA structure. DNA is made up of four different nucleotides. Each nucleotide consists of a sugar, a phosphate group and one of four different bases attached to the sugar. The bases are A, C, G and T. The bases on the two strands always join together in the same pairs: C with G and T with A. Describe the structure of DNA using diagrams and models. Explain how the bases on the two strands link together. 0.5 Describe DNA using a model, eg using sweets or shaped and coloured cards (see resources). Draw a diagram to represent DNA structure. Draw diagram to show base pairing. ABPI resource includes animation to sequence bases, the pharmaceutical industry and ethical issues of DNA profiling. Model DNA structure. Model base pairing. sweets or shaped and coloured cards. Model: different shaped and coloured cards to represent A, T, C and G to fit together. 4.6.1.5 4.6.1.5 HT: protein synthesis. The bases on the two strands HT: explain how the bases on the two strands link together. 0.5 Draw diagram to show base pairing. ABPI resource includes animation to sequence bases. base pairing. Model: different shaped and coloured cards to represent A,
these areas of DNA may affect how genes are expressed. 4.6.1.6 4.6.1.7 4.6.1.6 4.6.1.7 Genetic inheritance and inherited disorders. Some characteristics are controlled by a single gene. Each gene may have different forms called alleles. The genes present, or genotype, operate at a molecular level to develop characteristics that are expressed as a phenotype. A dominant allele is expressed if Give examples of characteristics controlled by a single gene and describe their alleles. Give examples of characteristics controlled by multiple genes. Define and use the terms: gametes, genotype, phenotype, dominant recessive, homozygous and heterozygous. Complete a Punnett square to show the outcomes of genetic crosses. Interpret the results of a genetic cross diagram and use direct proportion and simple 2 Discuss variation in families and why offspring have some characteristics of their mother and some of their father and often strongly resemble their grandparents. Complete Punnett squares. BBC activity Inheritance showing genetic crosses (see resources). Show images of polydactyly. Interpret family trees to determine chance of inheriting disorders. Watch a video to explain what cystic fibrosis is, how it is inherited and to illustrate the Complete Punnett squares and genetic crosses. Interpret the results and describe the offspring.
4.6.1.6 4.6.1.7 only present on one chromosome. A recessive allele is only expressed if present on both chromosomes. If the two alleles present are the same the person is homozygous for that trait, but if the alleles are different they are heterozygous. Most characteristics are a result of multiple genes interacting. Some disorders are inherited, eg polydactyly and cystic fibrosis. A Punnett square can be constructed to predict the ratios to express the outcomes. Describe the genotypes and phenotypes of the offspring. Describe the inherited disorders polydactyly and cystic fibrosis. Use genetic diagrams to explain inheritance and carriers. Make informed judgements about the economic, social and ethical issues concerning embryo screening. Discuss the use of genetic modification to genetic disorders (links with 4.6.1.4). HT: construct Punnet squares and genetic crosses. severity of the disorder (see resources). Evaluate genetic modification to treat cystic fibrosis. Produce notes and complete genetic diagrams to explain how polydactyly and cystic fibrosis are inherited. Interpret genetic diagrams relating to these disorders. Role play – choices for parents of a cystic fibrosis sufferer who would like another child. To involve experts explaining cystic fibrosis and the screening procedure; the child with the disorder; parents to discuss what they would do if the foetus had the disorder. Or Watch a video of the process and describe issues to be considered re embryo screening. Video clip: Video clip:
outcome of a monohybrid cross. 4.6.3.3 4.6.3.3 The understanding of genetics In the mid-19th century Gregor Mendel carried out breeding experiments using plants. He proposed the idea of separately inherited factors that we now call genes. In the late 19th century behaviour of chromosomes during cell division was observed. In the early 20th century it was observed that chromosomes and Mendel’s factors behaved in similar Describe some of the experiments carried out by Mendel using pea plants. Explain why Mendel proposed the idea of separately inherited factors and why the importance of this discovery was not recognised until after his death. Predict and explain the outcome of crosses using genetic diagrams based on Mendel’s experiments and using unfamiliar information. Describe a timeline showing the main developments in the understanding of inheritance. 1 Watch a video clip of Mendel’s experiments (see resources). Draw and label genetic diagrams to explain Mendel’s experiments. Interpret genetic diagrams of Mendel’s experiments. Research the main developments in the understanding of inheritance and draw a timeline. Use a model to explain genetic inheritance in pea plants and using unfamiliar information. Video clip:
ways, leading to the idea that the factors (genes) were located on chromosomes. In the mid-20th century the structure of DNA was determined and the mechanism of gene function worked out. 4.6.2.4 Genetic engineering. Genetic engineering involves modifying the genome of an organism to introduce a desired characteristic. Genes can be cut from the chromosome of a human or other Define the term genetic engineering. Describe the process of genetic engineering and its advantages. HT: describe in detail the process of genetic engineering. Evaluate the use of genetic engineering in medicine, eg in gene therapy and production of hormones and some vaccines. 1–2 Brainstorm what the terms genetic engineering, genetic modification and gene therapy mean. List examples of genetic engineering. Produce a leaflet for a doctor’s surgery to explain how human insulin is produced by bacteria and discuss the advantages of this over porcine insulin Use a model to describe genetic engineering techniques. Evaluate the use of genetic engineering in agriculture and medicine. Information on genetically modified food can be found at
4.6.2.4 organism and transferred into the cells of other organisms. HT: enzymes are used to cut the gene from a chromosome; gene is inserted into a vector, eg bacterial plasmid or virus; vector is used to insert gene into cell; cell then makes a new protein to produce the desired characteristic. Examples of genetic engineering. Concerns about GM crops, eg effect on populations of wild flowers and insects, and uncertainty about Interpret information about genetic engineering techniques. Make informed judgements about the economic, social and ethical issues concerning genetic engineering and GM crops. Explain advantages and disadvantages of genetic engineering. Interpret information about genetic engineering techniques. Research advantages and disadvantages of GM crops. What characteristics may be modified? Produce a web page or a table of benefits versus concerns for homework. Produce short, headline paragraphs to represent the views of organic farmers, organisers, GM Research scientists and students. Research the use of genetic engineering in medicine.
safety of eating them. 4.6.2.5 Cloning. Cloning techniques include: taking cuttings tissue culture embryo transplants adult cell cloning. Define the term clone. Describe plant cloning techniques to include: taking plant cuttings tissue culture. Explain the importance of cloning to plant growers. Interpret information about plant cloning techniques. Explain advantages and disadvantages of plant cloning techniques. 1 Discuss plant cloning techniques and why they are used. Take cuttings of different plants. Produce cauliflower clones – follow guidance from Science and Plants for Schools (SAPS). Observe growth in later lesson. Evaluate the use of cuttings and tissue culture to clone plants. Take cuttings and compare with the parent plants. Produce cauliflower clones using aseptic technique. Evaluate the method and results. Cuttings: scalpels or scissors plants, eg geraniums and spider plants pots compost or rooting compound. 4.6.2.5 Cloning Cloning techniques include: taking cuttings tissue culture embryo transplants cell cloning. Explain why identical twins are clones. Describe animal cloning techniques to include: embryo transplants adult cell cloning. Present arguments for and against human cloning. 1 Discuss how identical twins are formed and lead on to embryo transplants. Students produce models to explain the method of embryo transplants. Students evaluate strengths and weaknesses of their own and other models. Produce and evaluate a model to describe embryo transplants. Use a model to describe adult cell cloning. Twins and Dolly the sheep: Adult cell cloning video clip: Ethics of cloning video clip:
Spec ref. Summary of the specification content Learning outcomes What most candidates should be able to do Suggested timing (hours) Opportunities to develop scientific communication skills Opportunities to apply practical and enquiry skills Self/peer assessment Opportunities and resources Reference to past questions that indicate success 4.6.2.1 Variation. Differences in the characteristics of individuals may be due to: genes they have inherited environmental causes a combination of genetic and environmental causes. Classify characteristics as being due to genetic, environmental or a combination of these causes. Give examples of continuous and discontinuous variation. Decide the best way to present information about variation in tables and charts. 1–2 Discuss why organisms of the same species show variation. Use the terms: genetic and environmental variation, continuous and discontinuous variation. Class survey of characteristics – collate results in a table and produce a display of the results in appropriate format. Discuss how continuous data should be displayed. Include in the table whether each characteristic is due to genetic or environmental causes, or both. Measure variation in plants, eg leaf length in areas of sun/shade. you want to know if you had a genetic predisposition to illness that could be linked to environment? Eg, high cholesterol levels in family. Class survey and presentation of results. Measure variation in a plant species growing in different areas of school grounds.
Discuss the benefits of knowing how genes can be linked to diseases. 4.6.2.3 4.6.2.3 Selective breeding. Selective breeding (artificial selection) is the process by which humans breed plants and animals for useful characteristics. The steps involved in selective breeding. Selective breeding of food plants has produced disease or weather resistant crops, more attractive or better flavoured fruits and crops that are easier to harvest. Selective breeding of animals has produced cows that produce more Explain why humans selectively breed plants and animals. Describe selective breeding as a type of sexual reproduction. Describe the process of selective breeding and give examples. Explain the benefits and risks of selective breeding in plants and animals. 1 Images of different dogs. Students ‘breed’ and name a new dog from selecting any 2 – draw a picture of their new breed. Draw a flow diagram to explain the steps involved in selective breeding. Give examples of characteristics that are selectively bred in plants and animals. Discuss the advantages and risks of selective breeding in plants and animals. Debate: should people be allowed to breed dogs? Produce a to describe selective breeding. Consider the social, economic and ethical implications of selective breeding. Video clips:
milk, animals that produce more, better flavoured or leaner meat. Selective breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects. Some breeds of dogs suffer from inbred defects. 4.6.2.2 Evolution. Darwin’s theory of evolution by natural selection states that all species evolved from simple life forms that first developed more than three billion years ago. The main stages of natural selection. Describe Darwin’s theory of evolution by natural selection. Describe the main stages of natural selection as: individual organisms within a particular species may show a wide range of phenotype variation because of differences in their genes individuals with characteristics most suited to the environment are 2 Look at exhibition to show the wide variety of organisms that live, or have lived, on Earth. Discuss how they were all formed. BBC activity about Evolution. Watch BBC video clip illustrating survival of the fittest (see resources). Watch video clip about ancestor of horses from BBC Walking with Beasts. Use a model to explain natural selection. clip Horse ancestor: Darwin and evidence for evolution; extinction:
4.6.2.2 Mutations are changes in the DNA code. They may lead to more evolution, although mutations that result in a new phenotype are rare. Organisms of the same species can interbreed to produce fertile offspring. more likely to survive to breed successfully the genes that have enabled these individuals to survive are then passed on to the next generation. Define the term mutation. Explain why mutation may lead to more rapid change in a species. Define the term species. Identify organisms that are of different species. Interpret evolutionary trees. Draw a flow diagram to explain natural selection. Natural selection role play activities. Peppered moth game; explain in terms of natural selection. Look at pictures of Darwin’s finches and match up with the Galapagos Island they lived on based on food available there. Discuss how you could show that a donkey and a horse are different species. Interpret evolutionary Describe how to gather evidence for an evolutionary tree to describe relationships between organisms. Include the time scales involved in evolution. 4.6.3.2 Speciation. The work of Alfred Russel Wallace on natural selection, the theory of speciation and warning colouration in animals. Describe the work of Wallace. Explain how new species arise using the terms: isolation genetic variation natural selection speciation. 1 Research the work of Alfred Russel Wallace (see resources). Produce a flow diagram or to illustrate how new species Discuss organisms that are only found in or are endemic to eg Australia, Madagascar and Use a to explain speciation. The Socotra Archipelago – regarded as modern day Galapagos:
New species arise as a result of isolation, genetic variation, natural selection and speciation. ask why this is. Support with projected images or video clips. 4.6.3.1 Theory of evolution. Charles Darwin published his theory of evolution by natural selection in 1859. It raised much controversy. The theory of evolution by natural selection was only gradually accepted. There were other scientists who tried to explain evolution, eg Alfred Russell Wallace and Lamarck. State when Darwin published his theory and explain why it was only gradually accepted. Describe the work of Alfred Russel Wallace on natural selection. Describe the work of Lamarck. Identify differences between Darwin’s theory of evolution and conflicting theories. Suggest reasons for the different theories. Explain the inherited and acquired characteristics. 1 + Explain why Darwin did not publish his theory straight away and why it was only gradually accepted. Look at cartoons of Darwin drawn after he published his work and discuss the strength of opposition to his ideas. Interpret evidence relating to evolutionary theory. Sort pictures of organisms into an evolutionary timeline. Research and produce report on evolutionary theories, eg Darwin, Wallace and Lamarck. ‘Who said what’ cards representing key ideas/evidence from each theory as revision activity. Model an evolutionary timeline.
Compare the different theories and suggest reasons for these differences – turn into a ‘Question Time’ style role play. 4.6.3.4 4.6.3.5 4.6.3.7 4.6.3.4 4.6.3.5 4.6.3.7 Evidence for evolution – Fossils and Resistant bacteria. The theory of evolution by natural selection is now widely accepted. The evidence to support Darwin’s theory. Fossils. Fossils are the ‘remains’ of organisms from many years ago, which are found in rocks. Scientists cannot be certain about how life began on Describe the evidence for the theory of evolution by natural selection. Define the term ‘fossil’. Describe how fossils may be formed: from parts of organisms that have not decayed because one or more of the conditions needed for decay are absent when of the organism are replaced by other materials as they decay as preserved traces of organisms, eg footprints, burrows and rootlet traces. 1 Discuss the evidence we have to support Darwin’s theory and present in a suitable format. Observe fossils or pictures of fossils. Model how a fossil can be formed. Discuss how fossils provide evidence for evolution. Draw fossils. Model how a fossil can be formed. Fossils and pictures of fossils. Fossil formation: shells leaves and other artefacts sand plaster of Paris.