Revision summary help for the 9-1 OCR 21st Century Science GCSE BIOLOGY B Exam Papers - learning objectives B1-B3
OCR Level 1/2 GCSE (Grade 9-1) in Biology B (Twenty First Century Science) (J257) Paper 1 - OCR 21st Century GCSE Grade 9-1 Biology B revision summaries for Chapter B1, Chapter B2 and Chapter B3
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These are my NEW revision summaries for Y10 starting in September 2016, first exams from May-June 2018 onwards. ALL my unofficial GCSE (Grade 9-1) revision help is based on the NEW 2016 official OCR 9-1 GCSE Twenty First Century Science B biology/science specifications. Make sure you know whether you are doing separate science OCR 9-1 GCSE Twenty First Century BIOLOGY B OR OCR 9-1 GCSE Twenty First Century Combined Science B biology.
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Be aware that both Paper 1 and Paper 2 assess content from ALL 6 chapters !!!
Paper 1 is called "Breadth in Biology" and Paper 2 is called "Depth in biology"
(HT only) means higher tier only (NOT FT foundation tier) and (GCSE biology only) means the separate science, NOT for Combined Science biology
Syllabus-specification CONTENT INDEX of revision summary notes
Be aware that both Paper 1 and Paper 2 assess content from ALL 6 chapters !!!
Paper 1 is called "Breadth in Biology" and Paper 2 is called "Depth in biology"
OCR GCSE (9–1) BIOLOGY B Twenty First Century Science B
SUMMARY Chapter B1: You and your genes
SUMMARY Chapter B2: Keeping healthy
SUMMARY Chapter B3: Living together – food and ecosystems
SUMMARY Chapter B4: Using food and controlling growth
SUMMARY Chapter B5: The human body – staying alive
SUMMARY Chapter B6: Life on Earth – past, present and future (separate page)
SUMMARY Chapter B7: Ideas about Science (separate page)
Biology Key Ideas for OCR Twenty First Century Science GCSE 9-1 Biology B
Biology is the science of living organisms (including animals, plants, fungi and microorganisms) and their interactions with each other and the environment. The study of biology involves collecting and interpreting information about the natural world to identify patterns and relate possible cause and effect. Biological information is used to help humans improve their own lives and strive to create a sustainable world for future generations.
You should understand how, through the ideas of biology, the complex and diverse phenomena of the natural world can be described in terms of a small number of key ideas which are of universal application, and which can be illustrated in the separate topics set out below. These ideas include:
Chapter B1: (For OCR GCSE (9–1) Twenty First Century Science BIOLOGY B exam papers)
Chapter B1 You and your genes
Introduction to Chapter B1
The inheritance of genetic information from
each generation to the next is a fundamental idea in science; it can help us
answer questions about why we look the way we do, and build a foundation for
later exploration of ideas about genetic diseases, cell division and growth, and
From your Key Stages 1 to 3 science studies about genes and inheritance you should ...
Chapter Topic B1.1 What is the genome and what does it do?
All organisms contain genetic material. Genetic material contains instructions that control how cells and organisms develop and function. Most of an organism’s characteristics depend on these instructions and are modified by interaction with the environment.
Genetic material in plant and animal cells is located in the nucleus, one of the main sub-cellular structures. In organisms whose cells do not have a nucleus (e.g. bacteria) the genetic material is located in the cytoplasm.
All the genetic material of a cell is the organism’s genome. In most organisms the genome is packaged into chromosomes. Chromosomes are long molecules of DNA. Genes are sections of this DNA.
In the cells of plants and animals, chromosomes occur in pairs. The two chromosomes in a pair each carry the same genes. The two versions of each gene in the pair are called alleles, and can be the same or different. A different version of a gene is a genetic variant. The genotype of an organism is the combination of alleles it has for each gene; the phenotype is the characteristic that results from this combination and interaction with the environment. Genes tell a cell how to make proteins by joining together amino acids in a particular order.
1. (a) Be able to explain how the nucleus and genetic material of eukaryotic cells (plants and animals) and the genetic material, including plasmids, of prokaryotic cells are related to cell functions
1. (b) Be able to describe how to use a light microscope to observe a variety of plant and animal cells - Practical work: use a microscope to look at a variety of plant and animal cells, extract DNA from plant tissue.
2. Be able to describe the genome as the entire genetic material of an organism.
3. Be able to describe DNA as a polymer made up of nucleotides, forming two strands in a double helix.
4. Be able to describe simply how the genome and its interaction with the environment influence the development of the phenotype of an organism, including the idea that most characteristics depend on instructions in the genome and are modified by interaction of the organism with its environment. You are not expected to describe epigenetic effects.
5. Be able to explain the terms chromosome, gene, allele, variant, genotype and phenotype.
6. Be able to explain the importance of amino acids in the synthesis of proteins, including the genome as instructions for the polymerisation of amino acids to make proteins.
(GCSE Biology only) DNA is a polymer in which the monomers are nucleotides. Each nucleotide includes one of four different bases (adenine, thymine, cytosine or guanine).
(GCSE Biology HT only) The order of bases in a genome is the genetic code. The genetic code is modelled using letters (A, T, C, G) to represent the bases. The order (sequence) of bases in a gene is the code for protein synthesis. Each set of three nucleotides is the code for an amino acid. The properties of the protein that is made depend on which amino acids are present and their order.
7. (GCSE Biology only) Be able to describe DNA as a polymer made from four different nucleotides, each nucleotide consisting of a common sugar and phosphate group with one of four different bases attached to the sugar - use of letters to model the genetic code.
8. (GCSE Biology HT only) Be able to explain simply how the sequence of bases in DNA codes for the proteins made in protein synthesis, including the idea that each set of three nucleotides is the code for an amino acid.
9. (GCSE Biology HT only) Be able to recall a simple description of protein synthesis, in which:
(GCSE Biology HT only) Know that the order of bases in DNA can be changed if one or more nucleotides is deleted, inserted or substituted for a different nucleotide; these are mutations, and create genetic variants.
10. (GCSE Biology HT only) Be able to recall that all genetic variants arise from mutations.
(GCSE Biology HT only) If the sequence of bases in a gene is changed by mutation, a protein made from it may function differently or not at all, though in some cases, the mutation won’t have any effect. Some sections of DNA do not code for a protein, but they control whether particular genes are expressed, and therefore whether particular proteins are made. Thus, mutations in these sections can also affect phenotype by altering gene expression.
11. (GCSE Biology HT only) Be able to describe how genetic variants in coding DNA may influence phenotype by altering the activity of a protein.
12. (GCSE Biology HT only) Be able to describe how genetic variants in non-coding DNA may influence phenotype by altering how genes are expressed.
Chapter Topic B1.2 How is genetic information inherited?
During sexual reproduction, each offspring inherits two alleles of each gene; one allele from each gamete. The two alleles can be two copies of the same genetic variant (homozygous) or different variants (heterozygous). A variant can be dominant or recessive, and the combination of alleles determines what effect the gene has. Genetic diagrams such as family trees and Punnett squares can be used to model and predict outcomes of the inheritance of characteristics that are determined by a single gene. However, most characteristics depend on the instructions in multiple genes and other parts of the genome. Principles of inheritance of (single gene) characteristics were demonstrated in ideas developed by Gregor Mendel, using pea plants. Mendel’s work illustrates how scientists develop explanations that account for data they have collected.
(HT only) Our understanding of genetics has developed greatly since Mendel did his work; we now know that most characteristics depend upon interactions between genetic variants in multiple parts of the genome. Today, scientists sequence whole genomes to investigate how genetic variants influence an organism’s characteristics.
1. Be able to explain the terms gamete, homozygous, heterozygous, dominant and recessive.
2. Be able to explain single gene inheritance, including dominant and recessive alleles and use of genetic diagrams
3. Be able to predict the results of single gene crosses.
4. Be able to use direct proportions and simple ratios in genetic crosses.
5. Be able to use the concept of probability in predicting the outcome of genetic crosses.
6. Be able to recall that most phenotypic features are the result of multiple genes rather than single gene inheritance.
7. Be able to describe the development of our understanding of genetics including the work of Mendel ...
Know that a human individual’s sex is determined by the inheritance of genes located on sex chromosomes; specifically, genes on the Y chromosome trigger the development of testes.
8. Be able to describe sex determination in humans.
Chapter Topic B1.3 How can and should gene technology be used?
Comparing the genomes of individuals with and without a disease can help to identify alleles associated with the disease. Once we have identified such alleles we can test for them in adults, children, fetuses and embryos, to investigate their risk of developing certain diseases and of passing the alleles to their offspring (including the identification of ‘carriers’ of recessive alleles). Genetic testing can also help doctors to prescribe the correct drugs to a patient (‘personalised medicine’), by testing for alleles that affect how drugs will work in their body.
Another application of gene technology is genetic engineering, in which the genome is modified to change an organism’s characteristics. Genes from one organism can be added to another because all organisms use the same genetic code. Genetic engineering has been used to introduce characteristics useful to humans into organisms such as bacteria and plants.
Gene technology could help us provide for the needs of society, by improving healthcare and producing enough food for the growing population. But with genetic testing we must also consider how the results will be used and by whom, and the risks of false positives/negatives and miscarriage (when sampling amniotic fluid). With genetic engineering there are concerns about the spread of inserted genes to other organisms, the need for longterm studies to check for adverse reactions, and moral concerns about modifying genomes and the application of the technology to modify humans
1. Be able to discuss the potential importance for medicine of our increasing understanding of the human genome, including the discovery of alleles associated with diseases and the genetic testing of individuals to inform family planning and healthcare.
2. Be able to describe genetic engineering as a process which involves modifying the genome of an organism to introduce desirable characteristics.
3. (HT only) Be able to describe the main steps in the process of genetic engineering including:
4. Be able to explain some of the possible benefits and risks, including practical and ethical considerations, of using gene technology in modern agriculture and medicine
Chapter Topic B2: (For OCR GCSE (9–1) Twenty First Century Science BIOLOGY B exam papers)
Chapter B2 Keeping healthy
Introduction to Chapter B2
Issues of risk, ethics and social responsibility related to disease prevention and treatment in humans and plants are often in the news. Understanding the science of health and disease enables us to consider the issues critically, and to explore possible answers.
From your Key Stages 1 to 3 science studies about on health and disease you should ..
Chapter Topic B2.1 What are the causes of disease?
The health of most organisms will be compromised by disease during their lifetime. Physical and mental health can be compromised by disease caused by infection by a pathogen, an organism’s genes, environment or lifestyle, or trauma. Disease damages host cells and impairs functions, causing symptoms. However, an unhealthy organism may not always show symptoms of disease, particularly during the ‘incubation period’ after infection with a pathogen.
Some diseases are communicable: they are caused by infection with pathogenic bacteria, viruses, protists and fungi, and can be spread from organism to organism in bodily fluids, on surfaces, and in food and water. Other diseases are non-communicable: they are not caused by infection but are associated with genetic, environmental and lifestyle factors.
Some common diseases illustrate different types of pathogen and common routes of spread and infection, including:
1. Be able to describe the relationship between health and disease
2. Be able to describe different types of diseases (including communicable and non-communicable diseases)
3. Be able to explain how communicable diseases (caused by viruses, bacteria, protists and fungi) are spread in animals and plants
4. Be able to describe common human infections including influenza (viral), Salmonella (bacterial), Athlete’s foot (fungal) and malaria (protist) and sexually transmitted infections in humans including HIV/AIDS (viral)
5. Be able to describe plant diseases including tobacco mosaic virus (viral), ash dieback (fungal) and crown gall disease (bacterial)
Chapter Topic B2.2 How do organisms protect themselves against pathogens?
Humans have physical, chemical and bacterial defences that make it difficult for pathogens to enter the blood. These include the skin and mucus, stomach acid, saliva, tears, and bacteria in the gut. Platelets help to seal wounds to reduce the chance of pathogens entering the blood. These defences are always present, and are not produced in response to a specific pathogen. Plants have physical defences against pathogens, including the leaf cuticle and cell wall.
The immune system of the human body works to protect us against disease caused by pathogens. White blood cells destroy pathogens. White blood cells have receptors that recognise antigens on pathogens, to distinguish between non-self and self. Different types of white blood cell are adapted to either ingest and digest pathogens, or produce antibodies to disable them or tag them for attack by other white blood cells. An antibody is specific for (only recognises) a particular antigen. Once the body has made antibodies against a pathogen, memory cells stay in the body to make antibodies quickly upon re-infection (immunity).
1. Be able to describe non-specific defence systems of the human body against pathogens, including examples of physical, chemical and microbial defences
2. Be able to explain how platelets are adapted to their function in the blood.
3. (GCSE Biology only) Be able to describe physical plant defences, including leaf cuticle and cell wall.
4./3. Be able to explain the role of the immune system of the human body in defence against disease
5./4. Be able to explain how white blood cells are adapted to their functions in the blood, including what they do and how it helps protect against disease.
Plants do not have circulating immune cells or produce antibodies, but they have a simple immune system that protects them against pathogens. For example, plants can make antimicrobial substances in response to pathogens. The ability of plants to protect themselves against pathogens is important in human food security.
6. (GCSE Biology only) Be able to describe chemical plant defence responses, including antimicrobial substances.
Chapter Topic B2.3 How can we prevent the spread of infections?
Reducing and preventing the spread of communicable diseases in animals and plants helps prevent loss of life, destruction of habitats and loss of food sources. For plants, strategies include regulating the movement of plant material, sourcing healthy plants and seeds, destroying infected plants, polyculture, crop rotation and chemical and biological control. For animals, including humans, strategies include vaccination (to establish immunity), contraception, hygiene, sanitation, sterilising wounds, restricting travel, and destruction of infected animals.
The likely effectiveness, benefits, risks and cost of each strategy must be considered, and an individual’s right to decide balanced with what is best for society.
1. Be able to explain how the spread of communicable diseases may be reduced or prevented in animals and plants, to include a minimum of one common human infection, one plant disease and sexually transmitted infections in humans including HIV/AIDS.
2. Be able to explain the use of vaccines in the prevention of disease, including the use of safe forms of pathogens and the need to vaccinate a large proportion of the population
Chapter Topic B2.4 How can we identify the cause of an infection? (Separate science GCSE Biology Only)
In order to decide upon a course of treatment for a communicable disease, it is important to identify the disease and the pathogen causing it. There are standard ways to do this, including observing symptoms and taking samples of tissue or body fluid for cell counting, culture, microscopy, staining, testing with antimicrobials, and genome analysis. In addition, isolation and reinfection can be used to identify plant pathogens. Correct identification relies on use of aseptic techniques to avoid contamination of samples.
1. (a) Be able to describe ways in which diseases, including plant diseases, can be detected and identified, in the lab and in the field
1. (b) Be able to describe how to use a light microscope to observe microorganisms.
2. Be able to describe and explain the aseptic techniques used in culturing organisms.
3. Be able to calculate cross-sectional areas of bacterial cultures and of clear zones around antibiotic discs on agar jelly using πr2
4. (HT only) Be able to describe how monoclonal antibodies are produced including the following steps:
5. (HT only) Be able to describe some of the ways in which monoclonal antibodies can be used in diagnostic tests
Chapter Topic B2.5 How can lifestyle, genes and the environment affect health?
Whether or not a person develops a non-communicable disease depends on many factors, including the genetic variants they inherited, their environment and aspects of their lifestyle. The interaction of genetic and lifestyle factors can increase or decrease the risk.
1. (a) Be able to describe how the interaction of genetic and lifestyle factors can increase or decrease the risk of developing non-communicable human diseases, including cardiovascular diseases, many forms of cancer, some lung and liver diseases and diseases influenced by nutrition, including type 2 diabetes.
1. (b) Be able to describe how to practically investigate the effect of exercise on pulse rate and recovery rate
2. Be able to use given data to explain the incidence of non-communicable diseases at local, national and global levels with reference to lifestyle factors, including exercise, diet, alcohol and smoking
3. In the context of data related to the causes, spread, effects and treatment of disease be able to:
4. Be able to describe interactions between different types of disease.
Chapter Topic B2.6 How can we treat disease?
Humans have developed medicines that can control or eliminate the cause of some diseases and/or reduce the length or severity of symptoms. Antibiotics are becoming less effective due to the appearance of antibiotic resistant bacteria. For non-communicable diseases such as cardiovascular diseases, strategies that lower the risk of developing the disease have benefits compared to treatments administered later. Many factors need to be considered when prescribing treatments, including the likely effectiveness, risk of adverse reactions and the costs and benefits to the patient and others.
1. Be able to explain the use of medicines, including antibiotics, in the treatment of disease - risk and decision making in the context of medicines and treatment.
2. Be able to calculate cross-sectional areas of bacterial cultures and of clear zones around antibiotic discs on agar jelly using πr2.
3. Be able to evaluate some different treatments for lowering the risk of cardiovascular disease and treating it, including lifestyle changes, medicines and surgery.
Studying the genomes and proteins of pathogens and host cells can suggest targets for new medicines. Large libraries of substances are screened for their ability to affect a target. It is unlikely that a perfect medicine will be found during screening, but substances are selected for modification and further tests.
All new medicines have to be tested before they are made widely available. Preclinical testing, for safety and effectiveness, uses cultured human cells and animals. Clinical testing uses healthy human volunteers to test for safety, and humans with the disease to test for safety and effectiveness. ‘Open-label’, ‘blind’ and ‘double-blind’ trials can be used. There are ethical questions around using placebos in tests on people with a disease
4. Be able to describe the process of discovery and development of potential new medicines including preclinical and clinical testing - ethics in the context of using placebos in clinical testing of new medicines.
(GCSE Biology HT only) Some traditional treatments (e.g. radiotherapy and chemotherapy for cancer) cause adverse reactions. New technologies are enabling us to develop treatments that are more effective and have a lower risk of adverse reactions. For example, the specificity of monoclonal antibodies can be used to target cancer cells without damaging normal host cells.
5. (GCSE Biology HT only) Be able to describe how monoclonal antibodies can be used to treat cancer including:
Chapter B3: (For OCR GCSE (9–1) Twenty First Century Science BIOLOGY B exam papers)
Chapter B3 Living together – food and ecosystems
Introduction to Chapter B3
All living organisms depend on the ability of photosynthetic organisms to synthesise glucose from carbon dioxide and water in the presence of light, and on feeding relationships to transfer biomass through communities. From your Key Stage 3 Science, learners will be familiar with the reactants and products of photosynthesis, and the need for light in the process.
In Topics B3.1 and B3.2 you study in the context of photosynthesis, fundamental concepts in biology, including enzyme action and the movement of substances by diffusion, osmosis and active transport.
You will expand your knowledge of the interdependencies between organisms within ecosystems in Topic B3.3, through understanding of food webs, competition for resources, and the cycling of substances.
In Topic B3.4 you study the effects that environmental changes and human activities can have on interacting populations within ecosystems.
From your Key Stages 1 to 3 science studies about food and ecosystems you should ...
Chapter Topic B3.1 What happens during photosynthesis?
Producers make glucose using photosynthesis. Some of the glucose is used as the fuel for cellular respiration, some is converted into starch and then stored, and the rest is used to make lipids, proteins and other carbohydrates for growth. Photosynthesis involves many chemical reactions, but can be summarised in two main stages. The first stage requires light and chlorophyll (located in chloroplasts in plant cells) to split water molecules into hydrogen and oxygen. The hydrogen is transferred to the second stage, but the oxygen is released into the atmosphere as a waste product. The second stage combines carbon dioxide with hydrogen to make glucose.
1. (a) Be able to describe the process of photosynthesis, including the inputs and outputs of the two mains stages and the requirement of light in the first stage, and describe photosynthesis as an endothermic process
1b. (b) Be able to describe practical investigations into the requirements and products of photosynthesis.
2. Be able to explain how chloroplasts in plant cells are related to photosynthesis.
3. (a) Be able to explain the mechanism of enzyme action including the active site, enzyme specificity and factors affecting the rate of enzyme- catalysed reactions, including substrate concentration, temperature and pH.
3b. (b) Be able to describe practical investigations into the effect of substrate concentration, temperature and pH on the rate of enzyme controlled reactions.
Appreciate that understanding of how factors affect enzyme activity helps to explain the effects of temperature and carbon dioxide concentration on the rate of photosynthesis. The effect of light intensity is explained by the need for light to bring about reactions in photosynthesis.
(HT only) Light intensity is inversely proportional to the square of the distance from the light source (the inverse square law); this helps us explain why the rate of photosynthesis changes in the way that it does with distance from a point light source.
4. (a) Be able to explain the effect of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis.
4. (b) Be able to describe practical investigations into the effect of environmental factors on the rate of photosynthesis.
5. (HT only) Be able to use the inverse square law to explain changes in the rate of photosynthesis with distance from a light source.
6. (HT only) Be able to explain the interaction of temperature, light intensity and carbon dioxide concentration in limiting the rate of photosynthesis, and use graphs depicting the effects.
7. In the context of the rate of photosynthesis be able to:
Chapter Topic B3.2 How do producers get the substances they need?
The ways in which photosynthetic organisms take in carbon dioxide and water for photosynthesis, and release the waste product oxygen, illustrate the principles of diffusion and osmosis. Generally, molecules move from a region of their higher concentration to a region of their lower concentration; the difference in concentration drives a change towards equal concentration. Carbon dioxide and oxygen molecules move by diffusion, through cell membranes in single-cellular (prokaryotic) producers, and through stomata and cell membranes in plants. Water molecules move by osmosis through cell membranes; projections from root cells (‘root hairs’) of plants increase the surface area for osmosis.
The way in which photosynthetic organisms take in nitrogen (to make proteins) illustrates the process of active transport. Producers get nitrogen from nitrate ions (NO3–). Molecules of water and gases can diffuse through partially-permeable cell membranes but nitrate ions cannot; producers use energy from molecules of ATP to transport nitrate ions through the cell membrane by active transport.
1. Be able to describe some of the substances transported into and out of photosynthetic organisms in terms of the requirements of those organisms, including oxygen, carbon dioxide, water and mineral ions.
2. (a) Be able to explain how substances are transported into and out of cells through diffusion, osmosis and active transport.
2. (b) Be able to describe practical investigations into the processes of diffusion and osmosis. You are not expected to explain osmosis in terms of water potential
3. Be able to explain how the partially-permeable cell membranes of plant cells and prokaryotic cells are related to diffusion, osmosis and active transport
4. Be able to explain how water and mineral ions are taken up by plants, relating the structure of the root hair cells to their function
5. (a) Be able to explain how the structure of the xylem and phloem are adapted to their functions in the plant.
5. (b) Be able to describe how to use a light microscope to observe the structure of the xylem and phloem.
Sugars are moved through phloem from photosynthetic to non-photosynthetic tissues by translocation. Sugars are loaded into phloem by active transport, then water moves into the concentrated solution by osmosis and pushes the substances along the tube. The rate of water uptake by a plant can be affected by environmental factors. Light intensity and temperature affect the rate of photosynthesis (and therefore the demand for water), while air movement and temperature affect the rate of water loss from aerial parts of the plant.
6. (a) Be able to describe the processes of transpiration and translocation, including the structure and function of the stomata.
6. (b) Be able to describe how to use a light microscope to observe the structure of stomata.
6. (c) Be able to describe how to use a simple potometer.
7. (a) Be able to explain the effect of a variety of environmental factors on the rate of water uptake by a plant, to include light intensity, air movement, and temperature
7. (b) Be able to describe practical investigations into the effect of environmental factors on the rate of water uptake by a plant.
8. In the context of water uptake by plants be able to:
Chapter Topic B3.3 How are organisms in an ecosystem interdependent?
Producers take in carbon and nitrogen compounds from their environment and use them (along with oxygen, hydrogen and other elements) to make small organic molecules including sugars, fatty acids, glycerol and amino acids. These small molecules are used to make larger organic molecules, such as long-chain carbohydrates, lipids and proteins. The larger molecules are used to build new structures (e.g. membranes, organelles). Consumers can only get their supply of carbon and nitrogen compounds by eating producers (or other consumers that ate producers) and digesting the biomass. This releases the small molecules so they can be absorbed and then used to build biomass in the consumer. The transfer of biomass between organisms is one way in which the populations in a community are interdependent, and can be modelled using a food web (IaS3). The amount of biomass present at each trophic level is not shown by a food web, but can be modelled using a pyramid of biomass (IaS3). The size of each population in a community is limited by predation and competition for food and other resources including space, water, light, shelter, mates, pollinators and seed dispersers.
1. (a) Be able to explain the importance of sugars, fatty acids and glycerol, and amino acids in the synthesis and breakdown of carbohydrates, lipids and proteins.
1. (b) Be able to describe the use of qualitative tests for biological molecules.
2. Be able to describe photosynthetic organisms as the main producers of food and therefore biomass for life on Earth.
3. Be able to describe some of the substances transported into organisms in terms of the requirements of those organisms, including dissolved food molecules.
4. Be able to describe different levels of organisation in an ecosystem from individual organisms to the whole ecosystem.
5. Be able to explain the importance of interdependence and competition in a community.
6. (GCSE Biology only) Be able to describe the differences between the trophic levels of organisms within an ecosystem.
7. (GCSE Biology only) Be able to describe pyramids of biomass and explain, with examples, how biomass is lost between the different trophic levels.
8. (GCSE Biology only) Be able to calculate the efficiency of biomass transfers between trophic levels and explain how this affects
Substances essential to life, including water and carbon, cycle through the biotic and abiotic components of ecosystems so that they can be used and reused by organisms. Water cycles through precipitation, food chains, transpiration, excretion, runoff, flow through streams/rivers/oceans, and evaporation. Carbon cycles through photosynthesis, food chains, cellular respiration, decomposition and combustion. Decomposition is catalysed by enzymes released by microorganisms.
(GCSE Biology only) Rate of decomposition is affected by environmental factors: temperature affects enzymes and the rate of reactions; microorganisms need water to survive and many need oxygen for aerobic respiration. Landfill sites are often oxygen deficient, leading to an increase in anaerobic decomposition which produces methane – a gas with a much greater greenhouse effect than the carbon dioxide produced by aerobic decomposition.
9./6. Be able to recall that many different substances cycle through the abiotic and biotic components of an ecosystem, including carbon and water.
10./7. Be able to explain the importance of the carbon cycle and the water cycle to living organisms.
11./8. Be able to explain the role of microorganisms in the cycling of substances through an ecosystem.
12./9. Be able to calculate the percentage of mass, in the context of the use and cycling of substances in ecosystems.
13. (GCSE Biology only) Be able to explain the effect of factors such as temperature and water content on rate of decomposition in aerobic and anaerobic environments
14. (GCSE Biology only) Be able to calculate rate changes in the decay of biological material.
Chapter Topic B3.4 How are populations affected by conditions in an ecosystem?
The distribution and abundance of organisms in an ecosystem depends on abiotic and biotic factors. The size of one or more populations in a community may be affected if the environmental conditions change, or if a new chemical, competitor, predator or pathogen is introduced. A chemical can bioaccumulate in a food chain to toxic concentration, and some can cause eutrophication. A change in the size of a population will affect other populations in the same community.
The distribution and abundance of organisms, and changing conditions, within an ecosystem can be investigated using techniques including: identification keys; transects and quadrats; capture, mark, release and recapture; sampling living indicators; and using instruments to measure abiotic factors such as temperature, light intensity, soil moisture and pH.
1. Be able to explain how some abiotic and biotic factors affect communities, including environmental conditions, toxic chemicals, availability of food and other resources, and the presence of predators and pathogens.
2. Be able to describe how to carry out a field investigation into the distribution and abundance of organisms in an ecosystem and explain how to determine their numbers in a given area
3. In the context of data related to organisms within a population:
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Enter specific science words or science course e.g. topic, module, exam board syllabus or paper (AQA, Edexcel, OCR 21st Century/Gateway Science), formula, concept, equation, 'phrase', name of anything in biology, physics or chemistry, your latest homework question! anything of scientific interest!