OCR Level 1/2 GCSE (Grade 9-1) in Biology B (Twenty First Century Science) (J257) and OCR Level 1/2 GCSE (Grade 9-1) in Combined Science B Biology (Twenty First Century Science) (J260)

OCR 21st Century GCSE Grade 9-1 Biology B/Combined Science Chapters 1,2,3

Syllabus-specification CONTENT INDEX of revision summary notes

INDEX for all links

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 Twenty First Science (Grade 9-1) GCSE biology/combined science specifications

Make sure you know whether you are doing separate OCR Twenty First Century Science GCSE Grade 9-1 BIOLOGY OR OCR Twenty First Century Science GCSE Grade 9-1 Combined Science biology, BOTH are covered on this page and one other! (OCR Twenty First Century Science course students do NOT need to know sections on this page - all such sections are indicated e.g. GCSE BIOLOGY ONLY)

 The Google [SEARCH] box at the bottom of the page should also prove useful

Be aware that both Paper 1 and Paper 2 assess content from ALL 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


OCR GCSE (9–1) BIOLOGY B Twenty First Century Science COMBINED SCIENCE B biology

SUMMARY Chapter B1: You and your genes (this page, also Combined Science Biology Chapter B1

Revision summary Chapter B1.1 What is the genome and what does it do?

Revision summary Chapter B1.2 How is genetic information inherited?

Revision summary Chapter B1.3 How can and should gene technology be used?

SUMMARY Chapter B2: Keeping healthy (this page, also Combined Science Biology Chapter B2)

Revision summary Chapter B2.1 What are the causes of disease?

Revision summary Chapter B2.2 How do organisms protect themselves against pathogens?

Revision summary Chapter B2.3 How can we prevent the spread of infections?

Revision summary Chapter B2.4 How can we identify the cause of an infection? (Separate science GCSE Biology Only)

Revision summary Chapter B2.5 How can lifestyle, genes and the environment affect my health? (Combined Science B2.4)

Revision summary Chapter B2.6 How can we treat disease? (Combined Science B2.5)

SUMMARY Chapter B3: Living together – food and ecosystems (this page, also Combined Science Biology Chapter B3)

Revision summary Chapter B3.1 What happens during photosynthesis?

Revision summary Chapter B3.2 How do producers get the substances they need?

Revision summary Chapter B3.3 How are organisms in an ecosystem interdependent?

Revision summary Chapter B3.4 How are populations affected by conditions in an ecosystem?

SUMMARY Chapter B4: Using food and controlling growth (separate page, also Combined Science Biology Chapter B4)

Chapter B4.1 What happens during cellular respiration?

Chapter B4.2 How do we know about mitochondria and other cell structures?

Chapter B4.3 How do organisms grow and develop?

Chapter B4.4 How is plant growth controlled? (Separate GCSE Biology Only)

Chapter B4.5 Should we use stem cells to treat damage and disease? (Combined Science B4.4)

SUMMARY Chapter B5: The human body – staying alive  (separate page, also Combined Science Biology Chapter B5)

Chapter B5.1 How do substances get into, out of and around our bodies?

Chapter B5.2 How does the nervous system help us respond to changes?

Chapter B5.3 How do hormones control responses in the human body?

Chapter B5.4 Why do we need to maintain a constant internal environment?

Chapter B5.5 What role do hormones play in human reproduction?

Chapter B5.6 What can happen when organs and control systems stop working?

SUMMARY Chapter B6: Life on Earth – past, present and future (separate page, also Com'd Science Biology Chapter B6)

Chapter B6.1 How was the theory of evolution developed?

Chapter B6.2 How do sexual and asexual reproduction affect evolution?  (Separate GCSE Biology Only)

Chapter B6.3 How does our understanding of biology help us classify the diversity of organisms on Earth? (Combined Science B6.2)

Chapter B6.4 How is biodiversity threatened and how can we protect it? (Combined Science B6.3)

SUMMARY Chapter B7: Ideas about Science (separate page, Combined Science Chapter BCP7)

IaS1 What needs to be considered when investigating a phenomenon scientifically?

IaS2 What conclusions can we make from data?

IaS3 How are scientific explanations developed?

IaS4 How do science and technology impact society?


Biology Key Ideas for OCR Twenty First  Century Science GCSE 9-1 Biology B and OCR Twenty First Century Science GCSE 9-1 Combined Science - 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:

life processes depend on molecules whose structure is related to their function

the fundamental units of living organisms are cells, which may be part of highly adapted structures including tissues, organs and organ systems, enabling living processes to be performed effectively

living organisms may form populations of single species, communities of many species and ecosystems, interacting with each other, with the environment and with humans in many different ways

living organisms are interdependent and show adaptations to their environment

life on Earth is dependent on photosynthesis in which green plants and algae trap light from the Sun to fix carbon dioxide and combine it with hydrogen from water to make organic compounds and oxygen

organic compounds are used as fuels in cellular respiration to allow the other chemical reactions necessary for life

the chemicals in ecosystems are continually cycling through the natural world

the characteristics of a living organism are influenced by its genome and its interaction with the environment

evolution occurs by a process of natural selection and accounts both for biodiversity and how organisms are all related to varying degrees.


OCR GCSE (9–1) BIOLOGY B Twenty First Century Science COMBINED SCIENCE B biology

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 evolution.
 

In Topic B1.1 you study the basic concepts of the genome and how it affects an organism’s characteristics, through ideas about DNA and genes as the units of genetic information, the link between genes and proteins, and how the interaction between genes and the environment affects how an individual looks develops and functions.

In Topic B1.2 you study inheritance by considering the effects of dominant and recessive alleles, the inheritance of characteristics, the principles of inheritance of single-gene characteristics and how sex is determined. Understanding of the genome and emerging gene technologies are at the cutting edge of science, and they promise powerful applications to benefit present and future generations. But they also present ethical issues for individuals and society.

In Topic B1.3 you study some of the ideas people use to make decisions about applications of gene technology including genetic testing and genetic engineering.


From your Key Stages 1 to 3 science studies about genes and inheritance you should ...

know that living things produce offspring of the same kind, but normally offspring vary and are not identical to their parents

know that heredity is the process by which genetic information is transmitted from one generation to the next

know that genetic information is stored in the nucleus

understand a simple model of chromosomes, genes and DNA

know about the part played by Watson, Crick, Wilkins and Franklin in the development of the DNA model

know about sexual reproduction in animals, including the role of gametes and the process of fertilisation

know about sexual and asexual reproduction in plants, including flower structures and the processes of pollination and fertilisation


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.

The rest of B1.1 is for separate science Twenty First Century Science GCSE Biology only, NOT Combined Science

(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:

a copy of a gene is made from messenger RNA (mRNA)

the mRNA travels to a ribosome in the cytoplasm

the ribosome joins amino acids together in an order determined by the mRNA

You are not expected to recall details of transcription and translation.

(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.

Practical work - microscopy of pollen tubes on agar (nuclei visible under high power). Using genetic diagrams (e.g. family trees and Punnett squares) to model and predict outcomes of single gene inheritance. Distinguish data from explanatory ideas in an account of Mendel’s work, and explain how Mendel’s explanations accounted for the data he collected.

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.

You are not expected to describe epistasis and its effects

7. Be able to describe the development of our understanding of genetics including the work of Mendel ...

... and (GCSE biology HT only) the modern-day use of genome sequencing.

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.

Appreciate the involvement of genetic and other risk factors in the development of diseases such as cardiovascular disease, cancer and type 2 diabetes.

How can we treat disease?

Appreciate that genetic testing and genetic engineering as applications of science that have made a positive difference to people’s lives but also be able to discuss risks, benefits, ethical issues and regulation associated with gene technology.

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:

isolating and replicating the required gene(s)

putting the gene(s) into a vector (e.g. a plasmid)

using the vector to insert the gene(s) into cells

selecting modified cells

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


OCR GCSE (9–1) BIOLOGY B Twenty First Century Science COMBINED SCIENCE B biology

Chapter Topic 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.

In Topic B2.1 you will study how different pathogens are spread and cause disease, with reference to some common communicable diseases of humans and plants

In Topic B2.2 you will study how the immune system in humans protects against infection.

In Topic B2.3 you look at ways in which individuals and society can reduce the spread of diseases, linked to issues of risk and decision making, for example with regard to vaccination and contraception.

In Topic B2.4 you study the way that lifestyle and genetic factors increase (or decrease) the risk of developing noncommunicable diseases is explored, with reference to ideas about correlation and cause.

In Topic B2.5 you study issues related to the development and testing of new treatments.


From your Key Stages 1 to 3 science studies about on health and disease you should ..

appreciate that good hygiene helps humans keep healthy

be able to identify and name the main parts of the human circulatory system, and describe the functions of the heart, blood vessels and blood

appreciate the importance of bacteria in the human digestive system

know that animals, including humans, need the right types and amount of nutrition, and that a healthy human diet includes carbohydrates, lipids (fats and oils), proteins, vitamins, minerals, dietary fibre and water

recall some of the consequences of imbalances in the diet, including obesity, starvation and deficiency diseases

recognise the impact of diet, exercise, drugs and lifestyle on the way their bodies function

recall some of the effects of recreational drugs (including substance misuse) on behaviour, health and life processes.
 


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:

In humans: influenza (viral), Salmonella food poisoning (bacterial), Athlete’s foot (fungal), malaria (protist) and HIV (viral STI).

In plants: tobacco mosaic virus (viral), ash dieback (fungal) and crown gall disease (bacterial).

1. Be able to describe the relationship between health and disease

Practical work: modelling the spread of infection using liquids (where one is ‘infected’ with an invisible chemical that can be detected experimentally) and culture and microscopy of swabs from different surfaces.

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.

Practical work: investigating microbial growth on different foods and surfaces in different conditions.

Discussion of risk and decision making in the context of disease prevention.

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.

Practical work: Investigating the effect of antibiotic discs on growth of microorganisms on agar plates and practicing aseptic techniques.

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

(HT only) Monoclonal antibodies can be produced in the laboratory, using cultured clones of a white blood cell to produce antibodies against a particular antigen. All the antibodies produced by the clones recognise the same antigen.

(HT only) New technologies using monoclonal antibodies are providing diagnostic tests (e.g. for diseases) with greater sensitivity and specificity. These tests give faster and more accurate results, which enables decisions (e.g. about treatment) to be made more quickly and based on more accurate information.

4. (HT only) Be able to describe how monoclonal antibodies are produced including the following steps:

antigen injected into an animal

antibody-producing cells taken from animal

cells producing the correct antibody selected then cultured

Appreciate the use of monoclonal antibodies as a technological application of science that could make a significant differences to people’s lives.

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? (GCSE Combined Science B2.4)

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

what causes cancer (B4.3) and diseases caused by genes (B1.3)

Practical work:

Investigating the amounts of fat and sugar in foods/drinks

measuring blood pressure, recovery rate

Discussion of the correlation, cause and risk in the context of non-communicable diseases

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:

(a) translate information between graphical and numerical forms

(b) construct and interpret frequency tables and diagrams, bar charts and histograms

(c) understand the principles of sampling as applied to scientific data

(d) use a scatter diagram to identify a correlation

Different types of disease can interact, such as when having a disease increases or decreases the risk of developing or contracting another.

4. Be able to describe interactions between different types of disease.


Chapter Topic B2.6 How can we treat disease?  (Combined Science B2.5)

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:

produce monoclonal antibodies specific to a cancer cell antigen

inject the antibodies into the blood

the antibodies bind to cancer cells, tagging them for attack by white blood cells

the antibodies can also be attached to a radioactive or toxic substance to deliver it to cancer cells

Appreciate the use of monoclonal antibodies as a technological application of science that could make a difference to people’s lives.


OCR GCSE (9–1) BIOLOGY B Twenty First Century Science COMBINED SCIENCE B biology

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 ...

understand the similarities and differences between plant and animal cells

know that some organisms make their own food using photosynthesis

know that photosynthesis in plant cells occurs in the chloroplasts

know the reactants in, and products of, photosynthesis, and be able to write a word summary

know that photosynthesis requires light

be familiar with the adaptations of leaves for photosynthesis, and the role of stomata in gas exchange

know that water and minerals enter a plant through the roots

know that molecules of a solute move through solvent, and through cell membranes, by diffusion

know that animals obtain their food from plants (and other animals that ate plants)

understand the difference between carnivores, herbivores and omnivores, and between producers and consumers

know that individuals of the same type living in the same place make up a population, and that all the interacting populations in an ecosystem make up the community

understand the use of food chains and food webs as models of the feeding relationships within a community

appreciate the interdependence of organisms in a community, including food webs, the breakdown and cycling of materials, and animals as pollinators

know that changes in an ecosystem can affect the survival of individuals and populations.


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.

Practical work: on a whole plant, wrap one leaf in foil, and enclose another leaf in a conical flask with a small amount of KOH (to remove CO2); after 24 h, test leaves for starch.

 Photosynthesis, importance explained, limiting factors affecting rate

2. Be able to explain how chloroplasts in plant cells are related to photosynthesis.

The reactions in photosynthesis and many other biological processes are catalysed by enzymes. The lock and key model can be used to explain enzyme action. It can also be used to make predictions about the effect on the rate of enzyme-catalysed reactions when the substrate concentration, temperature and pH are changed.

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.

Practical work: Investigating the effects of substrate concentration, temperature and pH on enzyme activity - lock and key model to explain and make predictions about enzyme activity.

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.

Practical work: Investigating the rate of photosynthesis by collecting gas or counting bubbles from pondweed - using a datalogger to measure oxygen concentration, pH, temperature and light intensity over 24 h for pondweed.

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:

(a) understand and use simple compound measures such as the rate of a reaction

(b) translate information between graphical and numerical form

(c) plot and draw appropriate graphs selecting appropriate scales for axes

(d) extract and interpret information from graphs, charts and tables


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.

Practical work:

investigating diffusion using drops of ink in water and in agar in Petri dishes on graph paper

investigating diffusion across a partially permeable membrane using starch suspension in dialysis tubing in a beaker of water; compare adding iodine solution inside versus outside the tubing

investigating the effect of solute concentration on osmosis using potato cylinders in sugar solution

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

Plants do not have blood to transport substances around the organism; they have transport vessels formed from xylem and phloem. Water and ions (e.g. nitrate) in aqueous solution are moved through xylem from the roots and up the stem/trunk by transpiration, to replace water that evaporates from open stomata.

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.

Practical work:

using eosin stain to observe xylem in broad bean plant stem under hand lens and microscope

observing stomata (paint two thin layers of nail varnish onto a leaf, put clear tape over then peel off, stick to microscope slide)

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.

You are not expected to describe transpiration in terms of tension or pressure, and are not expected to describe translocation in terms of water potential or hydrostatic pressure

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:

a) use simple compound measures such as rate

(b) carry out rate calculations

(c) plot, draw and interpret appropriate graphs

(d) calculate percentage gain and loss of mass 


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.

Practical work:

Investigate the break down of starch into sugars using amylase and test strips

use a food web as a model to explain interdependence in a community, identify limitations of the model, and use it to make predictions about the effects that a change in the ecosystem could have on the interacting populations

using pyramids of biomass as models of biomass transfer in a food chain

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.

Practical work - culturing microorganisms on starch agar, stain with iodine solution; clear areas beyond cultures show digestion by extracellular amylase

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.

Practical work:

investigating the distribution and abundance of organisms in an ecosystem

Understand that bioaccumulation and eutrophication as unintended impacts of human activity on the environment.

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:

(a) calculate arithmetic means

(b) use fractions and percentages

(c) plot and draw appropriate graphs selecting appropriate scales for the axes

(d) extract and interpret information from charts, graphs and tables


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