Subject content

Unit 1 - HBIO1 The body and its diseases

Introduction

Introduction

The human body is composed of many different cell types. To maintain a healthy body, humans need to eat a balanced diet containing a variety of different molecules. Human food is composed of cells of other living organisms. Humans also need to exchange gases with their surroundings. Nutrients and dissolved gases are transported around the body in the blood.

Disease may result from infection by microorganisms, or from changes in the structure of organs or cells. Some diseases are linked with lifestyle.

It is anticipated that this unit will allow opportunity for the development of the skills of application and analysis as well as for the acquisition of the investigatory skills associated with Investigative and practical skills detailed in Unit 3.

3.1.1 - We are what we eat - the biochemical basis of life is similar for all living organisms.

We are what we eat - the biochemical basis of life is similar for all living organisms.

A balanced diet

The basis of a balanced diet.

Candidates should understand the roles of fibre, water, carbohydrates, fats, proteins, vitamins and mineral salts in a balanced diet.

Candidates should be able to explain why current dietary advice is that a healthy diet should be

  • high in fruit and vegetables
  • low in salt and fat.

Glycaemic Index (GI) and Glycaemic Load (GL)

Type 2 diabetes and obesity are conditions that have been linked to the increased consumption of processed foods.


The role of gut bacteria. The production of vitamin K by gut bacteria.


Isotonic sports drinks.


When provided with appropriate information, candidates should be able to evaluate

  • the evidence for, and make balanced judgements about, links between diet and diseases or conditions
  • the nutritional value of processed food.

When provided with appropriate information, candidates should be able to evaluate the nutritional value of processed food.

What is food and what happens to it?

Food consists largely of parts of other organisms. These organisms are made from the same types of molecules as are humans.

Many large biological molecules are polymers, made by joining smaller molecules together in condensation reactions. Large food molecules have to be hydrolysed to smaller molecules or monomers to be absorbed in the gut.

Knowledge of large biological molecules limited to carbohydrates, lipids and proteins(The molecular structures of these molecules are not required).

Monosaccharides may link together to form disaccharides or polysaccharides.

Glucose molecules may link together to form maltose, starch, glycogen and cellulose.

Proteins are made of amino acids. The overall shape of a protein molecule (its tertiary structure) is held together by hydrogen and ionic bonds, as well as disulphide bridges.

Fats are made of glycerol and fatty acids.

Digestive enzymes allow hydrolysis reactions to take place rapidly under the physiological conditions found in the gut.

Chromatography and calculation of Rf values is a technique by which the components of a mixture can be identified.

3.1.2 - Enzymes – fast, specific catalysts

Enzymes – fast, specific catalysts

Enzymes

The protein nature of enzymes.

Enzymes are catalysts that lower activation energy through the formation of enzyme-substrate complexes.

The lock-and-key and induced fit models of enzyme action.

Description and explanation of the effects on rate of reaction of

  • temperature
  • pH
  • substrate concentration

When provided with appropriate information, candidates should be able to use their knowledge of enzyme action to explain differences in the ability to digest different foods.

The reasons why humans can digest starch but not cellulose.

The causes and symptoms of lactose intolerance.

Enzymes - heroes
and villains

 

Because of their high sensitivity and specificity, enzymes may be used as analytical reagents. The use of glucose oxidase and peroxidase in testing for glucose.

Many enzymes are important in medicine. Trypsin in the development of lung disease and treatment with alpha-1-antitrypsin. Enzyme replacement therapy, pancreatic enzyme replacement therapy (PERT) for people with cystic fibrosis.

Disease can result in changes in the concentration and distribution of enzymes in the body. Pancreatitis may result in an increased concentration of digestive enzymes in the blood or a decrease in the concentration of these enzymes in the gut.

3.1.3 - Cystic fibrosis – just one small change in a protein

Cystic fibrosis – just one small change in a protein

Cystic fibrosis

The structure of the lungs in sufficient detail to understand that gas exchange is impaired in people with cystic fibrosis.

Efficient gas exchange requires a large surface area, a short diffusion pathway and a large concentration gradient, maintained by ventilation.

Candidates should be able to use their knowledge to explain how thick mucus in cystic fibrosis blocks the airways, reducing the efficiency of gas exchange.

The fluid-mosaic model of membrane structure.

Active transport.

Diffusion.

The process of osmosis explained in terms of water potential.

CFTR is a plasma-membrane protein that actively transports chloride ions out of a cell. In cystic fibrosis, the tertiary structure of this protein is altered, so chloride ions are not transported out of the cell.

Faulty chloride ion transport affects the water potential of mucus in the respiratory tract, resulting in thicker mucus.

Candidates should be able to explain why people with CF are prone to lung infections.

The role of ribosomes, endoplasmic reticulum, the Golgi body, and vesicles in producing CFTR protein and mucus. (Details of protein synthesis are not required)

Candidates should be aware that human cells are eukaryotic.

The role of mitochondria in supplying ATP for active transport. (No details of the respiratory pathway are required).

The effects of thick mucus in the gut of a person with CF, and the need to take enzyme capsules before meals.

3.1.4 Microorganisms use us for food, shelter and their reproduction

Microorganisms use us for food, shelter and their reproduction

Bacterial diseases

Bacteria may cause infectious diseases.

The structure of a prokaryotic cell, and the functions of its organelles, restricted to cell wall, plasma membrane, genetic material, plasmid, capsule, ribosome and flagellum.

Microorganisms can cause disease by damaging the cells of the host and by producing toxins.

The cause, symptoms and control of

  • Salmonella food poisoning
  • Tuberculosis

Antibiotics can be used to treat bacterial disease by interfering with bacterial metabolism, limited to prevention of cell wall synthesis and protein production.

When provided with appropriate information, candidates should be able to evaluate the evidence for the links between use of antibiotics and the development of MRSA and other antibiotic resistant bacteria. (Candidates are not required to understand how resistance to antibiotics arises.)

Viruses

Viruses cause disease.

The structure of the human immunodeficiency virus (HIV) and its replication.

Candidates should be able to explain

  • the development of the symptoms of AIDS
  • how HIV is spread, and how it may be controlled
  • why antibiotics are ineffective agains viruses.

3.1.5 - How the body fights infectious disease

How the body fights infectious disease

Our reaction to
something foreign

Antigen and antibody.

Phagocytosis and the subsequent destruction of ingested pathogens.

The role of T-cells and B-cells in the response to antigens.

The role of plasma cells and memory cells in producing the primary and secondary response.

The functions of cell types other than those specified and the classes of immunoglobulins are not required.

Immunity and vaccines

Antibodies may be acquired naturally through the placenta and via lactation, as well as artificially. This is passive immunity.

Vaccines containing attenuated or dead microorganisms, or isolated antigens, may be used as the basis for vaccines. Vaccination leads to active immunity.

When provided with suitable data, candidates should be able to evaluate evidence relating to the risks and benefits of mass vaccination programmes.

Magic bullets

The use of monoclonal antibodies to target specific substances and cells. Targeting medication to specific cell types by attaching a therapeutic drug to an antibody.

Monoclonal antibodies can be used in medical diagnosis. Testing for hCG in pregnancy test kits.

Details of the production of monoclonal antibodies will not be required.

3.1.6 - Some diseases are closely linked to life-style

Some diseases are closely linked to life-style

The heart

The gross structure of the heart in relation to its function. Pressure and volume changes and associated valve movements during the cardiac cycle.

Myogenic stimulation of the heart and transmission of a subsequent wave of electrical activity. Roles of sinoatrial node (SAN), atrioventricular node (AVN), bundle of His and Purkyne fibres.

The use of artificial pacemakers to regulate heart activity.

Cardiovascular disease

The structure of arteries and veins in sufficient detail to understand atheroma formation.

Atheroma and increased risk of angina, aneurysm and thrombosis.

Deep vein thrombosis (DVT) may occur as a result of prolonged inactivity, ageing and long-haul flights. Ways of reducing the incidence of DVT.

Myocardial infarction and its effects on heart muscle.

Treatment of coronary heart disease. Angioplasty, coronary by-pass surgery and betablockers. 

Coronary heart disease - personal decisions and consequences

When provided with appropriate information, candidates should be able to evaluate evidence for, and make balanced judgements about, the links between lifestyle and cardiovascular disease

Oedema

Over large distances, efficient supply of materials is provided by mass transport in the blood.

Individual cells in tissues and organs

  • obtain nutrients and oxygen from the blood
  • dispose of metabolic waste to the blood

The structure of capillaries and their importance in metabolic exchange.

The formation of tissue fluid and its return to the circulatory system. (Details of the lymphatic system are not required.)

Oedema results from a build-up of tissue fluid.

Requirements

Requirements

Biological Principles Investigative and practical skills

After studying the contents of this unit,candidates
should understand

  • that the biochemical basis of all life is the same
  • the structure of cells and the functions of their parts
  • that the body consists of cells, tissues, organs and systems
  • that disease-causing organisms use us for their growth and reproduction
  • that other diseases and conditions are a result of life-style decisions.

The examiners may draw on an understanding of these principles in Units 2 and 3. This understanding may also be required in the A2 units where it may
contribute to the assessment of synoptic skills.

Candidates will be expected to have carried
out practical investigations in the following areas

  • Investigations involving effects of temperature and pH on enzymes
  • Candidates should be able to test for disappearance of substrate or formation of product. The use of Benedict's reagent or iodine in potassium iodide solution.
  • Investigations involving sterile technique and bacterial growth on agar plates
  • Investigations involving water potential and osmosis
  • Chromatography. The calculation of Rf values.

Unit 2 - HBIO2 Humans – their origins and adaptations

Introduction

Introduction

The variety of life, both past and present, is extensive. Genetic information is copied and transmitted from generation to generation. Errors in transmission of this information may lead to new forms of organisms.

All living organisms interact with each other and their environment. Species exist as one or more populations. There is variation in the phenotypes in a population due to genetic and environmental factors. Mutation is the ultimate source of genetic variation. Natural selection acts on phenotypes in a population, leading to differential survival. The best adapted individuals have a higher probability of surviving to reproduce and pass on their alleles to the next generation. This process leads to evolution, changes in the gene pool of a population. Over time, natural selection and evolution lead to a population becoming adapted to its environment.

According to the theory of evolution, a population can evolve to the point where it becomes reproductively isolated from other populations. This is how a new species comes into existence. This process is also thought to have led to the enormous diversity of living organisms.

It is anticipated that this unit will allow for further development of the skills of application and analysis as well as for the acquisition of additional investigatory skills associated with Investigative and practical skills detailed in Unit 3.

3.2.1 - The information of life

The information of life

Nucleic acids - the
keys to life

The structure of DNA in terms of

  • the components of its nucleotides
  • the sugar phosphate backbone
  • base paring
  • hydrogen bonding

DNA as genetic material
The stucture of RNA in terms of

  • single polynucleotide strand
  • ribose replacing deoxyribose
  • uracil replacing thymine.

Details of mRNA and tRNA are not required.
Differences between DNA and RNA.

The structure of nucleic acids should be covered in sufficient detail to provide an understanding

  • of the roles of nucleic acids in determining the sequence of amino acids in proteins
  • that RNA is a copied section of DNA used in protein synthesis.

Details of protein synthesis are not required.

Candidates should be able to analyse and interpret experimental evidence that DNA is the genetic material. 

Candidates will not be expected to link scientists' names with particular investigations or to be familiar with the details of techniques.

Genes are sections of DNA which contain coded information that determines the nature and development of organisms.

A gene can exist in different forms called alleles which are positioned in the same relative position (locus) on homologous chromosomes.

Enzymes are proteins whose synthesis is controlled by DNA. They control metabolic pathways and thus influence the phenotype of an organism.

Candidates should be able to explain

  • how the structures of DNA and RNA are related to their functions 
  • the relationship between genes, proteins and enzymes
Semi-conservative replication of DNA

The semi-conservative mechanism of DNA replication. The role of DNA polymerase in DNA replication.

The relationship between DNA replication and the events of the cell cycle.

Candidates should be able to analyse and interpret experimental evidence for semi-conservative replication of DNA.

3.2.2 - Cell division - growth, repair, reproduction and cancer

Cell division - growth, repair, reproduction and cancer

Growth and repair

Mitosis increases cell number in growth and tissue repair.

During the cell cycle DNA is replicated. In mitosis the cell divides to produce two new cells, each containing an exact copy of the DNA of the parent cell.

Because we grow from a single fertilised cell (zygote) by mitosis all the cells in the body contain the same alleles.

Candidates should be able to

  • explain the behaviour of chromosomes and chromatids during the stages of mitosis
  • recognise and name each stage of mitosis from diagrams and photographs.

Mitosis is involved in asexual reproduction in some organisms.

Cancer - mitosis out of control

The main characteristics of tumours and tumour cells.

The distinction between benign and malignant tumours.

Consideration should be given to the following aspects

  • cell division is controlled by genes
  • chemical carcinogens and radiation may damage DNA and cause mutations in the genes controlling growth
  • tumour cells fail to respond to normal growth regulating processes 
  • they undergo metastasis and invade other organs
  • the role of tumour suppressor genes in preventing tumour growth.

When supplied with appropriate data candidates should be able to evaluate evidence for genetic and environmental factors increasing the incidence of cancer, including skin, lung and colon cancer.

Candidates should be able to interpret data showing the occurrence of cancers and links with possible causal factors, both genetic and environmental.

Candidates should be able to discuss the moral and ethical issues associated with the legality of cigarette smoking and treatment of diseases linked to smoking.

Sex and cell division - Meiosis

During meiosis in humans, cells containing pairs of homologous chromosomes divide to produce gametes containing one chromosome from each homologous pair.

In meiosis the number of chromosomes is reduced from the diploid number (2n) to the haploid number (n).

When gametes fuse at fertilisation to form a zygote the diploid number is restored. This enables a constant chromosome number to be maintained from generation to generation.

(Details of the stages of meiosis are not required.)

Sometimes there are errors in the process of meiosis leading to inherited conditions. Non-disjunction leads to Down's syndrome.

3.2.3 - Where we fit in the world and how we came to be here

Where we fit in the world and how we came to be here

What's in a name?

Classification is a means of organising the variety of life based on relationships
between organisms and is built around the concept of species.

Taxonomic hierarchy - kingdom, phylum, class, order, family, genus, species, as
illustrated by the classification of Homo sapiens.

Definition of a species as a group of similar organisms able to reproduce to give
fertile offspring.

Originally classification systems were based on observable features but more recent approaches draw on a wider range of evidence to clarify phylogenetic relationships
between organisms.

Biochemical, anatomical, embryological, immunological and behavioural evidence is
used in classification

Theories of Lamarck and Darwin

Evaluation of the theories of Lamarck and Darwin.

Selection and evolution.

Species exist as one or more populations.

Natural selection

  • individuals within a population may show a wide range of variation
  • predation, disease and competition result in differential survival and reproduction
  • those organisms with a selective advantage are more likely to survive, reproduce and pass on their alleles to the next generation.

Candidates should be able to interpret data and use unfamiliar information to explain how natural selection may produce change within a population.

Specification

Candidates should be able to explain how natural selection and isolation may result in changes in the allele and phenotype frequency and lead to reproductive isolation and the formation of a new species.

Candidates should be able to explain how evolutionary change over a long period of time has resulted in a great diversity of forms among living organisms.

The fossil record provides evidence for the process of evolution.

Fossil evidence can be dated by stratigraphy, potassium-argon and carbon dating.

Candidates should be able to analyse, interpret and evaluate evidence for the theory of evolution.

Once there were other humans

Study of hominids - Australopithecus, Homo erectus, Homo habilis, Homo neanderthalensis and Homo sapiens.

  • The hominid chronology
  • The major physical characteristics of early hominids limited to evidence for upright posture and cranial capacity
  • Evidence of diet
  • Different interpretations of limited evidence as exemplified by Ramapithecus

Cultural evolution accompanied physical change.

  • Development of early stone tools and the control of fire
  • Interpretation of archaeological evidence and possible uses of artefacts.

The principal characteristics of the hunter-gatherer way of life limited to the size
and structure of groups, range about a home base, division of labour and group
cooperation.

3.2.4 - Adaptations to a way of life

Adaptations to a way of life

Humans have
evolved adaptations
that increase
survival

Humans have adaptations to their environment and way of life. These adaptations increase the probability of

  • survival in their environment
  • successful reproduction
  • successful reproduction by their offspring

When supplied with suitable information candidates should be able to evaluate adaptations of humans to their environment and the contributions of these adaptations to increased survival.

Adaptations of the form

The advantages of anatomical adaptations of humans

  • bipedalism
  • opposable thumb
  • skin colour
  • surface area to volume ratio in humans from different climates.

When supplied with suitable information candidates should be able to evaluate how anatomical adaptations contribute to survival.

Adaptations to
vigorous exercise

The advantages of physiological adaptations in humans. Increases in breathing and heart rates and changes in the energy sources used by muscles associated with the demands of vigorous exercise.

Control of ventilation. The role of the

  • medulla in the brain and the stretch receptors in the lungs in the maintenance of breathing
  • medulla in the brain and the receptors in the lungs, aortic bodies and carotid bodies in the response of the breathing system to increased muscular  activity.

Control of heart rate.

The role of the medulla, pressure receptors and chemoreceptors in the walls of the aorta and carotid sinuses in the response of the heart to increased muscular activity

Cardiac output as the product of heart rate and stroke volume.

Changes in cardiac output with exercise.

Changes in energy sources used by muscles during exercise

  • glucose, glycogen and triglycerides as sources of energy for muscle contraction 
  • ATP as the immediate energy source
  • comparison of aerobic and anaerobic respiration as sources of ATP for muscle contraction, in terms of amounts of energy released and products
  • muscle fatigue in terms of increase in blood lactate and decrease in blood pH
  • the fate of lactate.

Biochemical details of pathways are not required.

The role of haemoglobin in the carriage of oxygen (Oxyhaemoglobin dissociation curve not required)

Peoples who live at high altitude have adaptations in terms of red blood cells and haemoglobin.

When supplied with suitable information candidates should be able to evaluate how physiological adaptations contribute to survival.

Adaptations of
behaviour

The advantages of behavioural and sociological adaptations of humans

  • communication using facial expressions
  • development of language during childhood
  • extended childhood.

When supplied with suitable information candidates should be able to evaluate how behavioural adaptations contribute to survival. 

Our parasites are
adapted to us
and our domestic
animals

Parasites have evolved adaptations to their environment and way of life.

The principal adaptations of parasites.

Some parasites are associated with our domestic animals; the adaptations of Toxocara that allow it to survive as a parasite in humans.

Parasites should be studied in sufficient detail to illustrate how they

  • are able to survive in the hostile environment within the host
  • have reduced locomotory and other structures
  • have modified reproduction and life cycle associated with infecting a new host.

When supplied with suitable information candidates should be able to evaluate the adaptations of a parasite to its human host.

3.2.5 - We have changed and are changing our environment

We have changed and are changing our environment

The development
of settled
communities

Evidence for early farming

The landscape and ecosystems in the UK are the result of human activities.
Deforestation to produce arable and grazing land, creation of the New Forest,
draining wetlands

When provided with appropriate information, candidates should be able to
evaluate the influence human activities have had on the landscape.

Making other
species work for us

The cultivation of crops and the domestication of animals have led to surplus food and the establishment of larger settlements.

Selective breeding illustrated with reference to cereals, dogs and cattle.

When provided with appropriate information, candidates should be able to
evaluate the impact of human activities on biodiversity and the environment

Requirements

Requirements

Biological principles Investigative and pratical skills

After completion of this unit, candidates should
understand
that

  • there is an enormous variety of life
  • characteristics are passed on from one generation
    to the next
  • errors in this process can lead to disease
  • organisms are changing with time
  • we group organisms according to characteristics
    for our own purpose
  • we have our place in the world, and have an
    enormous impact upon it.

Candidates will be expected to have carried
out practical investigations in the following areas

  • Microscopic observations of the stages of mitosis
  • Changes in ventilation of the lungs during exercise
  • Changes in heart rate during exercise.

Unit 3 - Investigative and practical skills in AS Human Biology

Introduction

Introduction

This unit will address the following aspects of the AS subject criteria. The ability to

  • demonstrate and describe ethical, safe and skilful practical techniques, selecting appropriate qualitative and quantitative methods
  • make, record and communicate reliable and valid observations and measurements with appropriate precision and accuracy.
  • analyse, interpret, explain and evaluate the methodology, results and impact of their own and others' experimental and investigatory activities in a variety of ways.

    Candidates will be assessed on their understanding of practical work in this Unit and in Units 1 and 2. Guidance on Internal Assessment can be found in Section 3.8 of the specification.

    Opportunities to carry out practical work are provided in the context of material contained in Units 1 and 2.

3.3.1 - Investigating biological problems involves changing a specific factor, the independent

Investigating biological problems involves changing a specific factor, the independent variable, and measuring the changes in the dependent variable that result.

Candidates should be able to

Practical work carried out in the context of Units 1 and 2 should enable candidates to gain experience of

  • use knowledge and understanding from the
    AS specification to pose scientific questions
    and define scientific problems
  • identify the independent variable and
    describe an appropriate method
    of varying it in such detail
    that a student starting an
    AS course could carry out the
    suggested procedure without
    further assistance
  • identify other variables that might
    be expected to exert a
    significant influence on the results,
    use knowledge from relevant parts
    of the AS specification to explain why,
    and describe how these would be
    kept constant
  • where necessary, describe how and explain why appropriate control experiments should be established
  • identify the dependent variable and describe how they would collect a full range of useful quantitative data, measured to an appropriate level of accuracy and precision
  • distinguish between accuracy and reliability and describe precautions needed to obtain valid, accurate and reliable data. 
  • the use of water baths to change or control temperature
  • the use of buffers to change or control pH
  • producing an appropriate dilution series when provided with stock solutions of reagents.

3.3.2 - Implementing involves the ability to work methodically and safely, demonstrating

Implementing involves the ability to work methodically and safely, demonstrating competence in the required manipulative skills and efficiency in managing time. Raw data should be methodically collected and recorded during the course of the investigation.

Candidates should be able to Practical work carried out in the context
of Units 1 and 2 should be enable
candidates to gain experience of
  • show full regard for safety and the
    ethical issues involved with
    the well-being of living organisms
    and the environment
  • carry out an investigation in a
    methodical and organised way
    demonstrating competence in
    the required manipulative skills
    and efficiency in managing
    time
  • take all measurements to
    an appropriate level of
    accuracy and precision
  • collect and present raw data
    in a suitable table conforming
    to the conventions specified
    in the Institute of Biology
    publication, Biological Nomenclature,
    Recommendations on Terms
    , Units and Symbols

    3rd edition (2000) concerning
    organisation and presentation
    of units.
  • using an optical microscope,
    preparing temporary mounts,
    staining and estimating size
  • collection of reliable quantitative
    data where
    • gas is evolved
    • colour change takes place
    • there are changes in mass of length

3.3.3 - Raw data may require processing. Processed data should be used to plot graphs which

Raw data may require processing. Processed data should be used to plot graphs which illustrate patterns and trends from which appropriate conclusions may be drawn. Scientific knowledge from the AS specification should be used to explain these conclusions.

Candidates should be able to Practical work carried out in the context of Units 1 and 2 should enable candidates to gain experience of
  • process data by carrying out appropriate
    calculations
  • select relevant data to present an
    effective summary of the
    results of an investigation and
    plot this as an appropriate
    graph conforming to the
    conventions specified in the
    Institute of Biology publication,
    Biological Nomenclature, 
    Recommendations on Terms,
    Units and Symbols, 3rd edition
    (2000)
    concerning organisation and
    presentation of units
  • describe, concisely but fully, the trends
    and patterns in data collected,
    relating these to specific values,
    quantities and units
  • recognise correlations and causal
    relationships
  • draw valid conclusions, relating explanations
    to specific aspects of the data
    collected and by applying
    biological knowledge and
    understanding from the AS
    specification.
  • using a standard scientific calculator to calculate mean and standard deviation, rate and percentage change
  • plotting data as line graphs, bar charts and histograms
  • plotting data as scatter diagrams and using these to identify correlation.

3.3.4 - Limitations are inherent in the material and apparatus used, and procedures

Limitations are inherent in the material and apparatus used, and procedures adopted. These limitations should be identified and methods of overcoming them suggested.

Candidates should be able to
  • identify the limitations of the material, apparatus
    and techniques used
  • discuss the effects of these limitations on the
    reliability and precision of the data and on the
    conclusions that may be drawn, resolving
    conflicting evidence
  • suggest realistic ways in which the effect of these
    limitations may be reduced.

Unit 4 - HBIO4 Bodies and cells in and out of control

Introduction

Introduction

Human bodies consist of complex organ systems carrying out different functions. The working of these different systems must be coordinated to ensure the efficient working of the body as a whole. This involves both nervous and hormonal coordination. Both systems involve receptors to detect stimuli, coordinators, and effectors that bring about a response.

At the cellular level, there is a hierarchy of control involving DNA, mRNA and catalysis by enzymes. At all levels, control involves feedback as a means of regulating cellular activity to meet the needs of the cell at a given time. The expression of genes is not as simple as once thought with epigenetic regulation of transcription assuming an increasingly important role. However, the patterns of inheritance of genes still follow Mendelian principles.

It is anticipated that, due to the thematic approach of the specification and the synoptic elements of Unit 5, this unit will be taught before Unit 5. This unit will allow opportunity for the development of the skills of application and analysis as well as for the acquisition of the investigatory skills associated with Investigative and practical skills detailed in Unit 6.

3.4.1 IVF – babies for those who cannot conceive naturally

IVF – babies for those who cannot conceive naturally

Reproduction and
contraception
Candidates should be familiar with the male and female
reproductive systems in sufficient detail to understand
 
  • the structure of the seminiferous tubules and ovaries
  • the roles of mitosis and meiosis in spermatogenesis and
    oogenesis emphasising differences between spermatogenesis
    and oogenesis
  • copulation and fertilisation - capacitation, acrosome reaction, formation
    of second polar body, fusion of nuclei and formation of a fertilisation membrane
  • formation of the blastocyst and its implantation
  • development of the placenta - its structure and role in transfer of materials
    between embryo and mother.

Birth and lactation.

The hormonal control of reproduction in females, the roles of

  • FSH, LH, oestrogen and progesterone in the menstrual cycle
  • hCG and progesterone in maintaining a pregnancy
  • progesterone and oxytocin concentrations in initiating labour
  • positive feedback controlling the secretion of oxytocin
  • oxytocin and prolactin in milk production.

The use of hormones in contraception.

Condoms, IUD, cap and 'morning after' pill as examples of other birth-control mechanisms.

IVFCandidates should be able to discuss the ethical and moral issues relating to the
use of different forms of contraception.
 

When provided with appropriate information, candidates should be able to evaluate evidence about the benefits and risks associated with the use of differnet forms of contraception.

Causes of infertility

  • low sperm count
  • blocked oviducts.

Use of IVF to treat women with blocked oviducts

  • using FSH to stimulate multiple ovulation
  • removal of the ococytes from the oviducts
  • fertilisation
  • culture to the 8 – 16 cell stage
  • re-implantation of some of the embryos.

Candidates should onsider the ethical and moral issues relating to the use of IVF

  • the fate of embryos that are not implanted
  • their possible use in scientific experiments
  • the extent to which IVF should be available.

3.4.2 - Growing up, growing old and passing on your genes

Growing up, growing old and passing on your genes

Patterns of human
growth

Whole body, reproductive organs and brain from infancy to adulthood.

Puberty and the development of the secondary sex characteristics in males and
females.

The effects and
diseases of ageing

Decline in physiological functions

  • basal metabolic rate (BMR)
  • cardiac output
  • nerve conduction velocity
  • female reproductive capacity as a result of changes in concentrations of pituitary and ovarian hormones.

Diseases associated with old age - Alzheimer's disease and cancer.

Candidates should be able to discuss the issues facing society in terms of
the increasing number of elderly people in the population and treating conditions
associated with old age.

Genetic Counselling
and Mendelian
inheritance

Candidates should be aware that many conditions needing treatment, or with the potential to need treatment, are inherited.

The terms gene, allele, genotype, phenotype, dominant, recessive, homozygous and heterozygous.

Cystic fibrosis as an example of monohybrid inheritance.

Sickle cell anaemia as an example of codominant alleles.

ABO blood groups as an example of inheritance involving multiple alleles.

Rhesus blood groups.

The potential dangers inherent in a rhesus negative mother giving birth to rhesus
positive babies.

Candidates should be able to give reasons why experimental results may only approximate to Mendelian ratios. They should be able to apply the chi-squared test
to establish the significance of any differences from predicted ratios.

Genetic counselling.

The use of information from family history and genetic screening to advise parents, the screening of embryos.

Candidates should consider the ethical and moral issues relating to genetic counselling.

Sex-linked
conditions and their
inheritance

The roles of the X and Y chromosomes in determining gender.

Sex-linked inheritance. Duchenne Muscular Dystrophy.

The reasons why these conditions are rare in women.

Variation in the next generation

Features showing discontinuous variation are categoric. ABO blood groups.

Features showing continuous variation often involve polygenic inheritance. They
often produce a normal distribution, which can be described in terms of mean and
standard deviation.

Concepts of mode and median .

When provided with appropriate information, candidates should be able to evaluate evidence about possible genetic predisposition to develop a disease or disorder.

 

Where variation comes from

Gene mutation produces new alleles; point mutations only, deletion and substitution.

In meiosis, crossing over, independent assortment and random fertilisation lead to new combinations of alleles.

Interaction of genes and the environment produce the phenotype. Twin studies show the effects of genes and environment.

Epigenetic imprinting may be affected by the environment.

This may lead to variation in the phenotype. Prader-Willi syndrome. This involves heritable changes in gene function or cell phenotype without changes in the genotype.

When supplied with appropriate data, candidates should be able to evaluate evidence for the relative influences of genetic and environmental factors on phenotype.

3.4.3 - The management structure of cells

The management structure of cells

DNA and protein
synthesis

The genetic code as a triplet, universal, non-overlapping and degenerate code.

Protein synthesis - the transcription of DNA, processing of mRNA, the roles of
mRNA, tRNA and ribosomes in translation.

The protein formed could be an enzyme, a receptor, or a structural protein.

Regulation of transcription of specific genes.

  • The steroid hormone, testosterone, which forms a complex with its receptor that initiates transcription, as a example of a substance that binds to receptor molecules inside the cytoplasm.
  • Increased methylation of the DNA or decreased acetylation of associated histones represses transcription.

Gene mutation can lead to formation of a non-functional protein. The CFTR protein in cystic fibrosis.

DNA and cancer

Benign and malignant tumours.

The role of the following in the development of tumours  

  • tumour suppressor genes and oncogenes
  • abnormal methylation of tumour suppressor genes and oncogenes
  • increased oestrogen concentrations in the development of some breast cancers.

When provided with appropriate information, candidates should be able to evaluate evidence showing correlations between environmental factors and various forms of cancer.

Candidates should be able to explain that a correlation does not prove a causal link. Further experimental investigation is needed to establish any causal link

 

 

Enzymes control the rate of reactions in cells

Enzymes coded for by DNA control cellular reactions.

The end-products of a series of reactions can influence the reaction by inhibiting the enzyme, or repressing transcription of a gene.

3.4.4 - New genes for old

New genes for old

Recombinant DNA

The production of recombinant DNA.

  • The use of DNA probes.
  • Isolating the gene by
    • creating the gene in a 'gene machine' or
    • creating the gene from mRNA or
    • using restriction enzymes to cut the gene from DNA.
  • The production of sticky ends.

The polymerase chain reaction produces larger quantities of DNA.

The transfer of recombinant DNA. The use of

  • plasmids as vectors
  • ligases
  • genetic markers to detect genetically modified organisms.

The role of gene libraries.

Candidates should consider whether or not selective breeding is ethically different
from the use of modern gene technologies.

Genetically
modified organisms

Selective breeding programmes have been used to create new strains and species
of crop plants.

The use of gene technology in producing GM organisms. Herbicide-resistant crop
plants and cattle with high milk yields.

Candidates should consider the ethical and moral issues relating to the production of GM organisms

  • ownership of genes
  • ownership of the modified organisms
  • financial benefits.

Sanctity of the species.

Genome projects,
what they tell us
and what they
don't.

The human genome has been sequenced.

Candidates should be aware that

  • the DNA nucleotide sequences have been determined
  • this does not translate into a list of genes coding for proteins
  • there is non-coding DNA
  • there are regulatory genes.

Determining the genome of simpler organisms allows the proteome of the organism to be determined.

This may allow vaccines to be produced against pathogens.

The work of the Sanger Institute in producing a vaccine against Plasmodium.

3.4.5 - Drugs can affect how we perceive the world around us

Drugs can affect how we perceive the world around us

Perception and
drugs

The functioning of the nervous system to appreciate the processes between
sensation, the detection of stimuli, and perception due to processing and
interpretation by the brain.

Candidates should be able to use their knowledge of the functioning of the
nervous system to explain how drugs can influence the functioning of the brain and
so affect mood and perception of reality

  • LSD and cocaine affecting the actions of monoamine neurotransmitters
  • marijuana binding to THC receptors
  • nicotine binding to nicotinic receptors in the brain and sympathetic ganglia.
Neurones and nerve impulses

The structure of myelinated sensory and motor neurones.

The role of the neurone membrane in

  • maintaining a resting potential
  • the initiation of an action potential and its all-or-nothing nature
  • the passage of an action potential along non-myelinated and myelinated axons resulting in nerve impulses.

The nature and importance of the refractory period in producing discrete nerve impulses.

The relationship between intensity of stimulation, size of generator potential and frequency of action potentials.

Synapses -
where neurones
communicate

The structure of a synapse as revealed by an electron microscope.

The sequence of events involved in the action of a cholinergic synapse and a neuromuscular junction.

The effect of drugs on synaptic transmission.

When provided with information, candidates should be able to predict and explain the effects of specific drugs on a synapse.

Detecting light - the eye

The structure of a human eye and its transmissive and refractive properties in focusing an image on the retina.

 

 

 

 

 

 

 

Perceiving - the brain

The role of rod cells and cone cells in effecting monochromatic and trichromatic vision.

The absorption of light by rhodopsin causes a chemical change leading to the creation of a generator potential.

Details of hyperpolarisation are not required.

The connections between sensory cells and the neurones of the optic nerve which allow sensitivity and acuity of vision.

Nerve pathways from eye to brain (optic nerve, optic chiasma, lateral geniculate nucleus, visual cortex) used to illustrate lateralisation and localisation of function in the brain.

Visual perception by the brain. A brief outline of 'top down' and 'bottom up' theories of visual perception.

When provided with information, candidates should be able to predict and explain the effects of specific drugs on perception.

3.4.6 - Fight or flight - muscles, hormones and nerves working together

3.4.6 Fight or flight - muscles, hormones and nerves working together

Flight or flight - anger and
fear
The nervous and hormonal systems work together to produce coordinated responses to stimuli which we perceive as threatening or frightening.

The roles of the hypothalamus, sympathetic nervous system and adrenal gland in bringing about the fight or flight response.

A comparison of nervous and hormonal coordination. Candidates should appreciate why hormonal control (particularly steroid hormone control) takes longer than nervous control.
The role
of the nervous system
Stimuli perceived by the brain can lead to hormonal changes that produce physiological responses. The role of the hypothalamus in mediating such responses.

The general role of the sympathetic and parasympathetic components of the autonomic nervous system and their antagonistic effects.

The hypothalamus 

receives input from the cerebral cortex
sends nerve impulses via the sympathetic nervous system
to effectors which may be muscles or glands (as exemplified by the adrenal glands).
The role of the hormonal system Information is transferred by hormones released by endocrine glands and affecting the physiological activities of target cells.

The physiological actions of adrenaline
Muslce contraction Candidates should be able to describe movement and maintenance of posture in terms of antagonistic muscle action.

Gross and microscopic structure of skeletal muscle. The ultrastructure of a myofibril.

The sliding-filament theory of muscle contraction.

The roles of actin, myosin, tropomyosin, calcium ions and ATP in myofibril contraction.

Muscles as effectors. The structure, location and general properties of slow and fast skeletal muscle fibres.

3.4.7 Hypothermia and diabetes - when controls fail to work

3.4.7 Hypothermia and diabetes - when controls fail to work 

 

HomeostasisPhysiological control systems operate in humans to maintain the internal environment within restricted limits. This is homeostasis.

The principle of negative feedback and its role in restoring systems to their original levels.
HypothermiaA condition in which body temperature falls below 35°C.

Normal thermoregulatory mechanisms fail.

The processes involved in thermoregulation in a mammal. The role of thermoreceptors in the skin and the hypothalamus.

The role of positive feedback as temperature continues to fall.
Diabetes - a disease of our timesThe regulation of blood glucose.

The factors which influence blood glucose concentration.

Role of hormones in activating enzymes involved in the interconversion of glucose and glycogen.

Details of biochemical pathways and individual enzymes are not required.

The roles of insulin and glucagon in controlling blood glucose.

Type 1 and Type 2 diabetes.

Control by insulin, changes of diet and lifestyle.

Candidates should be aware
of the health implications of undiagnosed or untreated diabetes.

When provided with appropriate information, candidates should be able to evaluate evidence showing correlations between life-style and the incidence of diabetes.

Biological principles

Requirements

 

Biological principlesInvestigative and practical skills

After studying the contents of this unit, candidates should understand that

  • there is a hierarchy of control at the cellular level, ultimately controlled by the genes 
  • genes are passed on during reproduction 
  • meiosis produces sex cells, which are the link between the generations 
  • implantation and the early stages of development are controlled by hormones
  • the human life span has definite stages 
  • patterns of inheritance of many features can be predicted using Mendelian principles
  • nervous and hormonal systems integrate the information detected by receptors and control our responses 
  • negative feedback systems control homeostatic mechanisms in the body.

Candidates will be expected to have carried out practical investigations in the following areas

  • Measurements relating to patterns of growth 
  • Microscopic observations of meiosis and comparisons with mitosis 
  • Mendelian inheritance in suitable organisms 
  • Perception of stimuli.

Unit 5 - HBI05 The air we breathe, the water we drink, the food we eat

Introduction

Introduction 

Human populations do not live in isolation. They are part of communities and ecosystems and depend upon other organisms for their survival. Human activities are changing the biotic and abiotic components of ecosystems. These changes are affecting our climate, and health. They are also changing the selection pressures on populations of other organisms we share ecosystems with. There are conflicts of interest between human demands and conservation of ecosystems. 

It is anticipated that, due to the thematic approach of the specification and the synoptic elements of this unit, it should be taught after Unit 4. This unit will allow for further development of the skills of application and analysis as well as for the acquisition of additional investigatory skills associated with Investigative and practical skills detailed in Unit 6.

Human impacts on evolution

Human impacts on evolution

 

EvolutionEvolution involves a change in the allele frequency in a population.

Individuals in a population of a species show variation. Phenotypic variation is due to genetic factors, differences in environmental factors or a combination of both.

Competition results in differential survival and reproduction.

Selection acts on populations.

Organisms with a selective advantage are more likely to survive, reproduce and pass on their genes to the next generation.

Selection may result in changes in the allele and phenotype frequency in a population.
Reproductive isolation of populations and the formation of new species.

Allopatric and sympatric speciation.

 Human activities have altered and are altering the environment of many organisms. This changes the selection acting on populations. This may affect the evolution of populations and species.

People change communities

People change communities

 

Ecosystems and the stability of populationsHumans have introduced species of plants and animals into this country. This has affected the stability of populations of native species, the communities they are part of and the ecosystems they live in.

An ecosystem comprises living organisms and the physical and chemical factors which make up their environment.

A population is all the organisms of one species in a habitat.

Populations of different species form communities.

These communities are found in a particular habitat and are based on dynamic feeding relationships.

Within a habitat a species occupies a niche governed by adaptation to food availability and/or prevailing abiotic conditions.

An ecosystem supports a certain size of population of any one species. This population size may vary as a result of

the effect of abiotic factors
interactions between organisms
inter- and intra-specific competition
predation.

Humans have introduced species of plants and animals into this country. This has affected the stability of populations of native species, the communities they are part of and the ecosystems they live in.

When provided with appropriate information, candidates should be able to evaluate evidence and make balanced judgements between meeting human demands and the need to conserve the environment.
Winners and losersDomesticated and introduced plants and animals affect natural ecosystems through competition with native species - the effects of domestic cats, grey squirrels and Japanese knotweed.

The growth of the urban environment has increased the habitat and niches for foxes, rats, pigeons and other species of wildlife.

When provided with appropriate information, candidates should be able to evaluate the cost implications of controlling introduced species.
GM organismsEnvironmental Impact Assessment.

The impact on communities and ecosystems of the large-scale introduction of genetically modified organisms, as exemplified by soya and maize.

When provided with appropriate information, candidates should be able to evaluate evidence and make balanced judgements between the need to meet the demands for certain crops and the need to conserve the environment.

Human' health can be affected when they change their environment

Humans' health can be affected when they change their environment 

 

Diet, crops and food allergiesThere have been changes in our diet. Vegetable oils are one of the plant products for which there has been a large increase in demand.

These changes have been linked to increases in a range of allergies

nut allergy
hay fever.

When provided with appropriate information, candidates should be able to evaluate evidence and make balanced judgements about meeting demands for certain crops and the impact on human health and well-being.
AllergiesAllergic responses produce illness.

Allergens are antigens that produce an abnormal immune response.

Hypersensitivity.
Detail limited to

Hay fever, food allergies, allergic asthma and hives as examples of allergic reactions involving histamine production
The allergen leads to production of IgE antibody by B cells
IgE binds to mast cells, which produce histamine when exposed to the allergen
Histamine leads to symptoms of allergy
Anaphylaxis is a sudden, acute reaction to an allergen. It can involve oedema in the airways leading to the lungs, or a large and sudden fall in blood pressure.

Skin tests for allergies, use of antihistamine to treat allergies and adrenaline to treat anaphylaxis.
Air pollution and respiratory illnessesWhen provided with appropriate information, candidates should be able to evaluate evidence and make balanced judgements about the claims of links between air pollution and respiratory illnesses, including asthma and bronchitis.
Water pollution and illnessesPollution of water by human activities can lead to illness.

Beaches and coliform standards. Coliform bacteria and faecal streptococci, as indicators of pollution by human sewage. Blue Flag beaches meet a water quality test.

Cryptosporidium is a single-celled parasite. It causes cryptosporidiosis. A resistant form, the oocyst, is in the faeces of infected animals and humans. The oocyst can infect a new host.

Pollution of water can occur from slurries from infected farm animals. Sewage discharged into rivers used for drinking water abstraction can carry oocysts released by infected humans.

When provided with appropriate information, candidates should be able to evaluate the cost implications of controlling water pollution.

Human activities can damage ecosystems and create new ones

Human activities can damage ecosystems and create new ones 

 

SuccessionEcosystems are dynamic systems, usually moving from colonisation to climax communities in a process known as succession.

Communities change with time, because of the interaction between species and their environment. At each stage certain species change the environment so that it becomes more suitable for other species.
Local wildlifeHuman activities often produce bare areas of land and water.

Wasteland is unmanaged land with vegetation in the early stages of succession.

Wasteland includes corridor habitat, such as cuttings and embankments associated with railway tracks and roadsides.

Brown-field sites are sites which have previously been developed for human use. These sites can be reclaimed to provide habitats for flora and fauna, as exemplified by species in decline because of urbanisation and intensive agriculture.

Ecosystems range in size from the very small to the very large.

Increasing area by a factor of ten approximately doubles the number of species present.

Larger sites are important in enhancing biodiversity in the urban environment.

Corridor habitats are important because they are common in the built environment and allow for the movement of plants and animals between habitats.

Candidates should be able to describe one example of the habitats on wasteland or a brown-field site.

Candidates should be able to describe

techniques used to measure the biotic factors in an ecosystem
and the abiotic factors in an ecosystem.
Waste disposal should be environmentally sustainableBest Practical Environmental Option (BPEO) as applied to waste management.

The BPEO is the option which provides the most benefit or least damage to the environment as a whole, at an acceptable cost in both the long and short term.

The waste hierarchy

waste should be prevented or reduced at source
waste materials should be re-used
waste materials should be recycled and used as a raw material
waste that cannot be re-used should be used as a substitute for non-renewable energy sources
only waste which cannot be treated in any of the above ways should go to landfill.

Microorganisms decompose organic remains. Anaerobic bacteria produce methane in landfill sites, which can be collected and used as fuel.

Polluter Pays Principle. The polluter pays for the direct and indirect environmental consequences of their actions.

When provided with appropriate information, candidates should be able to evaluate all the cost implications of pollution.

Plants can reduce the impact of the use of fossil fuels on climate change

Plants can reduce the impact of the use of fossil fuels on climate change 

 

Carbon footprintThe carbon footprint is a measure of the impact that human activities have on the amount of greenhouse gases produced, measured in terms of kilograms of carbon dioxide produced per year.

Candidates should be able to describe
  • how their primary contributions are calculated 
  • how their secondary contributions are calculated 
  • how household contributions can be reduced 
  • how carbon emissions can be off-set.
Our climate is changingThe burning of fossil fuels produces greenhouse gases. The climate of the United Kingdom is getting warmer. This affects the distribution of plants and animals.

Candidates should be able to describe the effects of climate warming on
  • the natural range of species 
  • breeding seasons 
  • the availability of food for some species at key times. 

When provided with appropriate information, candidates should be able to evaluate evidence of links between climate warming and changes in populations of species in the UK.
Plants remove carbon dioxide from the atmospherePhotosynthesis is the major route by which energy enters an ecosystem. Energy is transferred through the trophic levels in food chains and food webs and is dissipated.

Quantitative consideration of the efficiency of energy transfer between trophic levels.

In photosynthesis
  • energy is transferred to produce ATP and reduced NADP in the light-dependent stage 
  • ATP and reduced NADP are utilised during the light-independent stage, to incorporate carbon dioxide into sugars.

ATP synthesis is associated with the electron transfer chains in the membranes of chloroplasts.

(Details of electron transport and biochemical pathways are not required.)

Tree planting is used to off-set carbon dioxide emissions. Carbon is sequestered in the biomass of trees.
Biofuels reduce the use of fossil fuelsThese are renewable energy sources

  • biomass from fast-growing plants, used as fuel for burning 
  • vegetable oils used as diesel substitute 
  • ethanol from the fermentation of plant material, used as a petrol substitute or additive. 

To produce significant reductions in the use of fossil fuels, the plants used have to be grown on a very large scale. This will have impacts on the environment. It will also affect the availability of food for human consumption.

When provided with appropriate information, candidates should be able to evaluate the environmental and social impacts of the use of biofuels.

When provided with appropriate information, candidates should be able to evaluate the impact of the use of biofuels on national and global carbon dioxide emissions.
Respiration adds carbon dioxide to the atmosphereATP provides the immediate source of energy for biological processes.

All cells and organisms respire.

In respiration

  • glycolysis takes place in the cytoplasm 
  • and is anaerobic 
  • the remaining steps take place in the mitochondria 
  • ATP synthesis is associated with the electron transfer chain in the membranes of mitochondria 
  • oxygen is the final electron acceptor 
  • carbon dioxide is a waste product of aerobic respiration.

People and their microorganisms

People and their microorganisms 

 

The human ecosystem Ecosystems range in size from the very large to the very small.

The human body supports populations of bacteria and fungi.

These microorganisms
  • carry out extracellular digestion of biological molecules 
  • absorb the products of digestion 
  • use these for their own metabolism. 

This can recycle chemical elements from human cells.
The ecology of the skin Human skin supports a community of many microorganisms

  • Staphylococci 
  • Micrococci 
  • Corynebacterium
  • Fungi, such as yeast 

Spots and blemishes.

A number of skin conditions are caused by bacteria.

Acne vulgaris is caused by Propionibacterium acnes growing in and near sebaceous glands in the skin.

The use of antiseptics and antibiotics to control the populations of these bacteria.

When provided with appropriate information, candidates should be able to evaluate evidence and make balanced judgements between the claims of makers of different 'spot creams' and antibacterial soaps.

Candidates should be able to analyse and interpret experimental evidence from microbial growth investigations.
The ecology of the gut The human gut supports populations of bacterial species which form a bacterial community.

Human actions can change this community and adversely affect the functioning of the gut.

When provided with appropriate information, candidates should be able to evaluate evidence and make balanced judgements about 'probiotic' foods.
Antibacterial resistance Humans have introduced large amounts of antibacterial agents into the environment of bacteria.

Evolution of resistance to antibacterial agents.

MRSA.

When provided with appropriate information, candidates should be able to evaluate evidence relating to the impact of the widespread use of antibacterial agents.

Requirements

Requirements 

 

Biological principlesInvestiagtive and practical skills
After studying the contents of this unit, candidates should understand that human populations

  • are part of communities that live in ecosystems 
  • are part of complex food webs 
  • affect and are affected by changes in populations of other species 
  • rely on the energy that moves through communities 
  • affect and are affected by the abiotic components of the ecosystems they live in 
  • affect their own health and well-being through their environmental impact.
Opportunities to carry out practical work should be provided in the context of this unit

  • Assessment of the biodiversity of a site, in terms of species and numbers of individuals 
  • Factors affecting the rate of photosynthesis 
  • Factors affecting rate of respiration 
  • The effects of antibacterial agents on the growth of bacterial culture.

Unit 6 - Investigative and practical skills in A2 Human Biology

Introduction

Introduction

This unit will address the following aspects of the A2 subject criteria. The ability to

demonstrate and describe ethical, safe and skilful practical techniques, selecting appropriate qualitative and quantitative methods 

make, record and communicate reliable and valid observations and measurements with appropriate precision and accuracy 

analyse, interpret, explain and evaluate the methodology, results and impact of their own and others' experimental and investigatory activities in a variety of ways. 

Candidates will be assessed on their understanding of investigative and practical skills in this unit and in Units 4 and 5. Guidance on Internal Assessment can be found in Section 3.8. Opportunities to carry out practical work are provided in the context of material contained in Units 4 and 5

Investigating biological problems involves changing a specific factor, the independent variable, and measuring the changes in the dependent variable that result

Investigating biological problems involves changing a specific factor, the independent variable, and measuring the changes in the dependent variable that result.

 

Candidates should be able to Practical work carried out in the context of Units 4 and 5 should enable candidates to gain experience of
  • use knowledge and understanding from the A level specification to pose scientific questions and define scientific problems 
  • identify the independent variable and describe an appropriate method of varying it in such detail that a student starting an A2 course could carry out the suggested procedure without further assistance 
  • identify other variables that might be expected to exert a significant influence on the results, use knowledge from relevant parts of the A level specification to explain why, and describe how they would be kept constant or monitored 
  • where necessary, describe how and explain why appropriate control experiments should be established 
  • identify the dependent variable and describe how they would collect a full range of useful quantitative data that could be analysed statistically, measured to an appropriate level of accuracy and precision 
  • distinguish between accuracy and reliability and describe precautions needed to obtain valid, accurate and reliable data.
  • random sampling 
  • the use of a three-way tap in collecting gas samples 
  • establishing anaerobic conditions

Inplementing involves the ability to work methodically and safely, demonstrating competence in the required manipulative skills and efficiency in managing time. Raw data should be methodically collected and recorded during the course of the investigation

Implementing involves the ability to work methodically and safely, demonstrating competence in the required manipulative skills and efficiency in managing time. Raw data should be methodically collected and recorded during the course of the investigation.

 

Candidates should be able to Practical work carried out in the context of Units 4 and 5 should enable candidates to gain experience of
  • show full regard for safety and the ethical issues involved with the well-being of living organisms and the environment 
  • carry out an investigation in a methodical and organised way demonstrating competence in the required manipulative skills and efficiency in managing time 
  • take all measurements to an appropriate level of accuracy and precision 
  • present raw data in a suitable table conforming to the conventions specified in the Institute of Biology publication, Biological Nomenclature, Recommendations on Terms, Units and Symbols, 3rd edition (2000) concerning organisation and presentation of units.
  • collection of reliable quantitative ecological data involving a specific abiotic factor, frequency, population density and percentage cover.

Data should be analysed by means of an appropriate statistical test. This allows calculation of the probability of an event being due to chance. Appropriate conclusions should be drawn and scientific knowledge from the A Level specification should be used to explain these conclusions.

Data should be analysed by means of an appropriate statistical test. This allows calculation of the probability of an event being due to chance. Appropriate conclusions should be drawn and scientific knowledge from the A Level specification should be used to explain these conclusions.

Statistics 

Candidates should be aware that there are 

  • tests of difference: is this group different from that group? 
  • tests of relationship: is one variable associated with another? 

Tests of difference typified by t-test for normally distributed data where data are not normally distributed (or this is not known). 

Tests of relationship typified by the correlation coefficient (r) and Spearman's rank-order correlation.

 

Candidates should be able to Practical work carried out in the context of Units 4 and 5 should enable candidates to gain experience of
  • select and justify the choice of an appropriate statistical test from the following

    standard error and 95% confidence limits
    correlation coefficient (r)
    Spearman rank correlation
    χ2
    t-test 
  • construct an appropriate null hypothesis 
  • calculate the test statistic given a standard scientific calculator 
  • interpret the calculated test statistic in terms of the appropriate critical value at the 5% significance level, making reference to chance, probability and acceptance or rejection of the null hypothesis 
  • draw valid conclusions, relating explanations to specific aspects of the data collected and by applying biological knowledge and understanding from the A Level specification.
  • selecting, using and interpreting an appropriate statistical test from the following

    standard error and 95% confidence limits
    correlation coefficient (r)
    χ2
    t-test

Candidates will not be expected to remember the formulae for these tests. 

Candidates will be expected to 

  • apply the appropriate test 
  • interpret the results of such tests.

Limitations are inherent in the material and apparatus used and procedures adopted. These limitations should be identified, evaluated and methods of overcoming them suggested.

Limitations are inherent in the material and apparatus used and procedures adopted. These limitations should be identified, evaluated and methods of overcoming them suggested.

Candidates should be able to 

  • identify the limitations inherent in the apparatus and techniques used 
  • discuss and assess the relative effects of these limitations on the reliability and precision of the data and on the conclusions that may be drawn, resolving conflicting evidence 
  • suggest realistic ways in which the effect of these limitations may be reduced 
  • suggest further investigations which would provide additional evidence for the conclusions drawn.
  • How science works

    How science works

    How Science Works 

    How Science Works is an underpinning set of concepts and is the means whereby students come to understand how scientists investigate scientific phenomena in their attempts to explain the world about us. Moreover, How Science Works recognises the contribution scientists have made to their own disciplines and to the wider world. 

    Further, it recognises that scientists may be influenced by their own beliefs and that these can affect the way in which they approach their work. Also, it acknowledges that scientists can and must contribute to debates about the uses to which their work is put and how their work influences decision making in society. 

    In general terms, it can be used to promote students' skills in solving scientific problems by developing an understanding of:

    • the concepts, principles and theories that form the subject content
    • the procedures associated with the valid testing of ideas and, in particular, the collection, interpretation and validation of evidence
    • the role of the scientific community in validating evidence and also in resolving conflicting evidence.

    As students become proficient in these aspects of How Science Works, they can also engage with the place and contribution of science in the wider world. In particular, students will begin to recognise:

    • the contribution that scientists can make to decision-making and the formulation of policy
    • the need for regulation of scientific enquiry and how this can be achieved
    • how scientists can contribute legitimately in debates about those claims which are made in the name of science.

    An understanding of How Science Works is a requirement for this specification and is set out in the following bullet points which are taken directly from the GCE AS and A Level subject criteria for science subjects. Each bullet point is expanded in the context of Human Biology. The specification references given illustrate where the example is relevant and could be incorporated.

    Use theories, models and ideas to develop and modify scientific explanations

    Use theories, models and ideas to develop and modify scientific explanations

     

    A Scientists use theories and models to attempt to explain observations. These theories or models can form the basis for scientific experimental work.

    Scientific progress is made when validated evidence is found that supports a new theory or model.

    Examples in this specification include

    • at AS, Unit 2 (3.2.3), Darwin and the theory of evolution 
    • at A2, Unit 4 (3.4.3), Management of cells and epigenetics.

    Use knowledge and understanding to pose scientific questions, define scientific problems, present scientific arguments and scientific ideas

     

    B Scientists use their knowledge and understanding when observing objects and events, in defining a scientific problem and when questioning their own explanations or those of other scientists.

    Scientific progress is made when scientists contribute to the development of new ideas, materials and theories.

    Examples in this specification include

    • at AS, Unit 1 (3.1.4), HIV and its control 
    • at A2, Unit 4 (3.4.1), Contraception.

    Use appropriate methodology, including ICT, to answer scientific questions and solve scientific problems

     

    C Observations ultimately lead to explanations in the form of hypotheses. In turn, these hypotheses lead to predictions that can be tested experimentally. Observations are one of the key links between the 'real world' and the abstract ideas of science.

    Once an experimental method has been validated, it becomes a protocol that is used by other scientists.

    ICT can be used to speed up, collect, record and analyse experimental data.

    Examples in this specification include

    • at AS, Unit 2 (3.2.2), Cancer and environmental causes 
    • at A2, Unit 4 (3.4.4), PCR.

    Carry out experimental and investigative activities, including appropriate risk management, in a range of contexts

     

    D Scientists perform a range of experimental skills that include manual and data skills (tabulation, graphical skills etc).

    Scientists should select and use equipment that is appropriate when making accurate measurements and should record these measurements methodically.

    Scientists carry out experimental work in such a way as to minimise the risk to themselves, to others, and to other organisms and the materials used.

    Examples in this specification include

    • at AS, Unit 2 (3.2.4), Adaptations of physiology 
    • at A2, Unit 5 (3.5.6), Ecology of the skin.

     Analyse and interpret data to provide evidence, recognising correlations and causal relationships

     

    E Scientists look for patterns and trends in data as a first step in providing explanations of phenomena. The degree of uncertainty in any data will affect whether alternative explanations can be given for the data.

    Anomalous data are those measurements that fall outside the normal, or expected, range of measured values. Decisions on how to treat anomolous data should be made only after examination of the event.

    In searching for causal links between factors, scientists propose predictive theoretical models that can be tested experimentally. When experimental data confirm predictions from these theoretical models, scientists become confident that a causal relationship exists.

    Examples in this specification include

    • at AS, Unit 2 (3.2.3), Once there were other humans 
    • at A2 Unit 5 (3.5.5), Climate change.

    Evaluate methodology, evidence and data, and resolve conflicting evidence

    F The validity of new evidence, and the robustness of conclusions that stem from it, is constantly questioned by scientists.

    Experimental methods must be designed adequately to test predictions.

    Solutions to scientific problems are often developed when different research teams produce conflicting evidence. Such evidence is a stimulus for further scientific investigation, which involves refinements of experimental technique or development of new hypotheses.

     Examples in this specification include

    • at AS, Unit 1 (3.1.5), Vaccines 
    • at A2, Unit 4 (3.4.4), Genetically modified organisms.

    Appreciate the tentative nature of scientific knowledge

     

    G Scientific explanations are those that are based on experimental evidence, which is supported by the scientific community.

    Scientific knowledge changes when new evidence provides a better explanation of scientific observations.

    Examples in this specification include

    • at AS, Unit 2 (3.2.3), Theories of Lamark and Darwin 
    • at A2, Unit 5 (3.5.3), Air pollution and respiratory illness.

    Communicate information and ideas in appropriate ways using appropriate terminology

     

    H By sharing the findings of their research, scientists provide the scientific community with opportunities to replicate and further test their work, thus either confirming new explanations or refuting them.

    Scientific terminology avoids confusion amongst the scientific community, enabling better understanding and testing of scientific explanations.

    Examples in this specification include

    • at AS, Unit 2 (3.2.3), What's in a name? 
    • at A2, Unit 5 (3.5.2), Ecosystems and terminology.

    Consider applications and implications of science and appreciate their associated benefits and risks

     

    I Scientific advances have greatly improved the quality of life for the majority of people. Developments in technology, medicine and materials continue to further these improvements at an increasing rate.

    Scientists can predict and report on some of the beneficial applications of their experimental findings.

    Scientists evaluate, and report on, the risks associated with the techniques they develop and the applications of their findings.

    Examples in this specification include

    • at AS, Unit 1 (3.1.6), Treatment of cardiovascular disease 
    • at A2, Unit 5 (3.5.5), Biofuels.

    Consider ethical issues in the treatment of humans, other organisms and the environment

     

    J Scientific research is funded by society, either through public funding or through private companies that obtain their income from commercial activities. Scientists have a duty to consider ethical issues associated with their findings.

    Individual scientists have ethical codes that are often based on humanistic, moral and religious beliefs.

    Scientists are self-regulating and contribute to decision-making about what investigations and methodologies should be permitted.

    Examples in this specification include

    • at AS, Unit 2 (3.2.2), Cancer and environmental links 
    • at A2, Unit 5 (3.5.4), Local wild life.

    Appreciate the role of the scientific community in validating new knowledge and ensuring integrity

     

    K The findings of scientists are subject to peer review before being accepted for publication in a reputable scientific journal.

    The interests of the organisations that fund scientific research can influence the direction of research. In some cases the validity of those claims may also be influenced.

    Examples in this specification include

    • at AS, Unit 1 (3.1.1), Balanced diet and processed foods 
    • at A2, Unit 4 (3.4.4), Genetically modified organisms.

    Appreciate the ways in which society uses science to inform decision-making

     

    L Scientific findings and technologies enable advances to be made that have potential benefit for humans.

    In practice, the scientific evidence available to decision-makers may be incomplete.

    Decision-makers are influenced in many ways, including by their prior beliefs, their vested interests, special interest groups, public opinion and the media, as well as by expert scientific evidence

    Examples in this specification include

    • at AS, Unit 1 (3.1.6), Life style and disease 
    • at A2, Unit 4 (3.4.1), IVF.

    Guidance on Internal Assessment

    Introduction

    Guidance on Internal Assessment

    Introduction 

    The GCE Sciences share a common approach to internal assessment. This is based on the belief that assessment should encourage practical work in science, and that practical work should encompass a broad range of activities. This section must be read in conjunction with information in the Teaching and learning resources web pages. 

    Investigative and Practical Skills are assessed in Unit 3 and Unit 6, worth, respectively, 20% of the AS Award (and 10% of the A Level Award) and 10% of the full A Level Award. 

    There are two routes for the assessment of Investigative and Practical Skills 

    Either

    Route T: Practical Skills Assessment (PSA) + Investigative Skills Assignment (ISA) – Teacher-marked 

    Or 

    Route X: Practical Skills Verification (PSV) + Externally Marked Practical Assessment (EMPA) – AQA-marked. 

    Both routes to assessment are available at AS and A2. 

    Centres can not make entries for the same candidate for both assessment routes [T and X] in the same examination series. 

    The assessments produced for each of Unit 3 and Unit 6 are common to AQA AS/A Level Biology (2410) and AQA AS/ALevel Human Biology (2405). As a result, centres entering candidates for both Biology and Human Biology in the same session for both unit 3s and/or both units 6s must enter these candidates for route T for one subject and route X for the other subject. These candidates can not enter the same route for both qualifications.

    3.8.1 Centre Assessed Route T (PSA/ISA)

    Each centre assessed unit comprises 

    • Practical Skills Assessment (PSA) 
    • Investigative Skills Assignment (ISA). 

    The PSA consists of the centre's assessment of the candidate's ability at the end of the course to demonstrate practical skills; thus, candidates should be encouraged to carry out practical and investigative work throughout the course. This work should cover the skills and knowledge of How Science Works (Section 3.7) and in Sections 3.3 and 3.6. 

    The ISA has three stages where candidates 

    • undertake practical work and collect data 
    • process the data 
    • complete a written ISA test. 

    There are two windows of assessment for the ISA:

    • one for the practical work (Stages 1 and 2)
    • one for the written test (Stage 3).

    Each stage of the ISA must be carried out

    All students at a centre must complete the written test in a single uninterrupted session on the same day.

    The ISA is set externally by AQA, but internally marked, with marking guidelines provided by AQA. 

    In a given academic year two ISAs at each of AS and A2 will be provided. 

    Practical Skills Assessment (PSA) 

    Candidates following this route must undertake the practical activities outlined in Sections 3.3 for AS or 3.6 for A2 in order to allow candidates suitable opportunities to demonstrate safe and skilful practical techniques and to make reliable and valid observations. 

    Candidates are assessed throughout the course on practical skills, using a scale from 0 to 6. The mark submitted for practical skills should be judged by the teacher. Teachers may wish to use this section for formative assessment and should keep an ongoing record of each candidate's performance but the mark submitted should represent the candidate's practical abilities at the end of the course. 

    The nature of the assessment 

    Since the skills in this section involve implementation, they must be assessed while the candidate is carrying out practical work. Practical activities are not intended to be undertaken as formal tests and teachers can provide the level of guidance that would normally be given during teaching. In order to provide appropriate opportunities to demonstrate the necessary skills, the instructions provided must not be too prescriptive but should allow candidates to make decisions for themselves, particularly concerning the organisation and conduct of practical work, and the manner in which equipment is used.

    The assessment criteria 

    In the context of material specified in the relevant AS or A2 specification, candidates will be assessed in the following skills 

    • following instructions 
    • selecting and using equipment 
    • organisation and safety 

    Descriptors for these three skills areas are provided for 0, 1 and 2 marks. 

    Candidates should be awarded marks which reflect their level of performance at the end of the course.

    AQA may wish to ask for further supporting evidence from centres in relation to the marks awarded for the PSA. Centres should therefore keep records of their candidates' performances in their practical activities throughout the course. (For example, a laboratory diary, log or tick sheet.)

    The assessment criteria

    The Assessment Criteria 

     

    Following instructionsSelecting and using equipmentOrganisation and safety
    0 marks
    Able to follow instructions involving standard procedures only when guidance is given.
    0 marks
    Able to select appropriate laboratory equipment only when guidance is given.

    Able to make measurements with assistance.
    0 marks
    Works in a disorganised manner.

    Works safely only with constant supervision.
    1 mark
    Able to follow instructions involving standard procedures but unable to follow instructions involving complex procedures without further guidance.
    1 mark
    Able to select appropriate laboratory equipment.

    Able to make accurate measurements but requires guidance on making repeat measurements.
    1 mark
    Works in an organised manner.

    Works with due regard to safety, but needs occasional guidance or reminders.
    2 marks
    Able to follow instructions involving both standard and complex procedures without guidance.
    2 marks
    Able to select appropriate laboratory equipment. Able to make accurate measurements and to recognise when it is appropriate to repeat measurements.

    2 marks
    Works in an organised manner.

    Works with due regard to safety, showing competence in risk management.

    Further guidance for the awarding of marks for the PSA will be provided in the Teaching and learning resources web pages.

    Use of ICT during the PSA

    Candidates are encouraged to use ICT where appropriate in the course of developing practical skills, for example in collecting and analysing data.

    Investigative Skills Asignment

    Investigative Skills Assignment (ISA)

    The Investigative Skills Assignment carries 44 marks and has three stages. 

    Stage 1: Collection of data 

    Candidates carry out practical work following an AQA task sheet. Centres may use the task sheet as described or may make minor suitable modifications to materials or equipment, following AQA guidelines. Details of any amendments made to the task sheet must be agreed in writing with the AQA Assessment Adviser. The task may be conducted in a normal timetabled lesson but must be under controlled conditions and during the window of assessment for practical work. 

    For AS, candidates collect raw data and represent it in a table of their own design or make observations that are recorded on the Candidate Result Sheet. The candidates' work must be handed to the teacher at the end of the session. The teacher assesses the candidates' work following AQA marking guidelines. 

    For A2, candidates collect raw data on the Candidate Result Sheet. The candidates' work must be handed to the teacher at the end of each session. The raw data is not assessed by the teacher. 

    There is no specified time limit for this stage. 

    Stage 2: Processing of data 

    The teacher returns the candidates' data from Stage 1 (on the Candidate Result Sheet). 

    For AS, the teacher instructs the candidates to process the data (e.g. calculate means or rates of reaction) and plot an appropriate graph. The teacher must not instruct the candidates on the presentation of the data or on the choice of graph or chart. 

    For A2, the teacher instructs the candidates to process the data and carry out a suitable statistical test. The teacher must not instruct the candidates on the choice, implementation and interpretation of the statistical test. 

    For both AS and A2, stage 2 may be done in normal lesson time and must be done in a single session under controlled conditions and during the window of assessment for practical work. Both the raw and the processed data must be handed to the teacher at the end of the session. The teacher assesses the candidates' work to AQA marking guidelines. 

    Stage 1 and Stage 2 may be done in the same session. There is no specified time limit for Stage 2.

    Stage 3: The ISA written test 

    The ISA test should be taken after completion of Stage 2, under controlled conditions and during the window of assessment for the written test. All candidates at a centre must complete the written test in a single uninterrupted session on the same day. Each candidate is provided with an ISA test and their completed material from Stages 1 and 2. The teacher uses the AQA marking guidelines to assess the ISA test. 

    The ISA test is in two Sections. 

    Section A 

    This consists of a number of questions relating to the candidate's own data. 

    Section B 

    At the start of this section, candidates are supplied with additional data on a related topic. A number of questions relating to analysis and evaluation of the data then follow. 

    The number of marks allocated to each section may vary slightly with each ISA test. 

    Use of ICT during the ISA 

    ICT may be used during the ISA but teachers should note any restrictions in the ISA marking guidelines or Teachers' Notes. Use of the internet is not permitted. 

    Candidates absent for the practical work 

    A candidate absent for the practical work should be given an opportunity to carry out the practical work before they sit the ISA test. This may be with another group or at a different time. In exceptional cases when such arrangements are not possible, the teacher can supply a candidate with class data. In this case the candidate cannot be awarded marks for Stage 1, but may be awarded marks for Stage 2.

    Material from AQA 

    For each ISA, AQA will provide: 

    • Teachers' Notes 
    • Task sheet 
    • ISA test 
    • Marking guidelines. 

    This material must be kept under secure conditions within the centre. The centre must ensure the security of the material. Further details regarding this material will be provided. 

    Security of assignments 

    All materials including marked ISAs should be treated like examination papers and kept under secure conditions until the publication of results.

    General Information Route T 

    Administration 

    In any year a candidate may attempt either or both of the two ISAs. AQA will stipulate windows of assessment during which the ISAs (task and test) must be completed. 

    For each candidate, the teacher should submit a total mark to AQA comprising: 

    • the PSA mark 
    • the better ISA mark (if two have been attempted). 

    The ISA component of this mark must come from one ISA only, i.e. the marks awarded for individual stages of different ISAs cannot be combined. 

    Candidates may make only one attempt at a particular ISA. Redrafting is not permitted at any stage during the ISA. 

    The mark must be submitted by the due date in the academic year for which the ISA was published. 

    Only Internally Assessed Units from the Human Biology specification can contribute towards an AS or A Level Award in Human Biology. Biology unit entry codes can not be used towards a Human Biology qualification. 

    Work to be submitted 

    For each candidate in the sample the following materials must be submitted to the moderator by the deadline issued by AQA. 

    • the candidate's data from Stage 1 and 2 (on the Candidate Result Sheet
    • the ISA written test, which includes the Candidate Record Form, showing the marks for the ISA and the PSA. 

    In addition each centre must provide

    • Centre Declaration Sheet
    • Details of any agreed amendments to the task sheet with information supporting the changes from the AQA Assessment Adviser. 

    Working in groups 

    For the PSA, candidates may work in groups provided that any skills being assessed are the work of individual candidates. For the ISA further guidance about working in groups will be provided in the Teachers' Notes. 

    Other information 

    Section 6 outlines further guidance on the supervision and authentication of internally assessed units.

    Section 6 also provides information in relation to the internal standardisation of marking for these units. Please note that the marking of both the PSA and the ISA must be internally standardised as stated in Section 6.4. 

    Further support 

    AQA supports the units in a number of ways. 

    • AQA holds annual standardising meetings on a regional basis for all internally assessed components. Section 6 of this specification provides further details about these meetings 
    • Teaching and learning resources which include Instructions for Administration of the ISA
    • Assessment Advisers are appointed by AQA to provide advice on internally assessed units. Every centre is allocated an Assessment Adviser. 

    The Assessment Advisers can provide guidance on 

    – issues relating to the carrying out of tasks for assessment 

    – application of marking guidelines. 

    Any amendments to the ISA task sheet must be discussed with the Assessment Adviser and confirmation of the amendments made must be submitted to the AQA moderator.

    3.8.2 Externally Marked Route X (PSV/ EMPA) 

    The practical and investigative skills will be assessed through 

    • Practical Skills Verification (PSV) and 
    • Externally Marked Practical Assignment (EMPA). 

    The PSV requires teachers to verify their candidates' ability to demonstrate safe and skilful practical techniques and make valid and reliable observations. 

    The EMPA has three stages where candidates 

    • undertake a themed task and collect data 
    • process the data 
    • complete a written EMPA test 

    There are two windows of assessment for the EMPA:

    • one for the practical work - Task 1 and Task 2 (Stages 1 and 2)
    • one for the written test (Stage 3)

    Each stage of the EMPA must be carried out

    All candidates at a centre must complete the written test in a single uninterrupted session on the same day.

    The EMPA is set and marked by AQA. Only one EMPA at each of AS and A2 will be provided in a given academic year.

    Practical Skills Verification 

    Candidates following this route must undertake the practical activities outlined in sections 3.3 for AS and 3.6 for A2 in order to allow candidates suitable opportunities to demonstrate safe and skilful practical techniques and to make reliable and valid observations. The teacher will confirm, on the front cover of the written test, for each candidate that this requirement has been met. Failure to complete the tick box will lead to a mark of zero being awarded to the candidate for the whole of this unit. 

    In the context of material specified in the relevant AS or A2 specification, candidates will be required to demonstrate the following skills 

    • following instructions 
    • selecting and using equipment 
    • organisation and safety. 

    Practical activities must provide candidates with opportunities to develop the knowledge and skills of How Science Works outlined in section 3.3 and 3.6. Teachers can provide the level of guidance that would normally be given during practical activities. However, in order to provide appropriate opportunities to demonstrate the necessary skills, instructions provided must not be too prescriptive but should allow candidates to make decisions for themselves, particularly concerning the organisation and conduct of practical work, and the manner in which equipment is used. 

    Further guidance for conducting practical activities for the PSV will be provided in the Teaching and learning resources web pages.

    ICT 

    Candidates may use ICT where appropriate in the course of developing practical skills, for example in collecting and analysing data. 

    Externally Marked Practical Assignment (EMPA)

    The Externally Marked Practical Assignment carries 50 marks and has three stages. 

    Stage 1: Themed task and collection of data 

    Candidates carry out practical work following AQA task sheets. The tasks may be conducted in a normal timetabled lesson and at a time convenient to the centre but must be under controlled conditions and during the window of assessment for practical work.

    For AS, candidates collect raw data and represent it in a table of their own design on Task Sheet 1. The candidates' work must be handed to the teacher at the end of each session. 

    For A2, candidates collect raw data on Task Sheet 1. The candidates' work must be handed to the teacher at the end of each session. 

    Centres may use the task sheets, as described, or may make minor suitable modifications to materials or equipment following AQA guidelines. Any modifications made to the task sheet must be agreed with the Assessment Adviser and details must be provided to the AQA examiner. The task may be conducted in a normal timetabled session. 

    There is no specified time limit for this stage. 

    Stage 2: Processing of data 

    For AS, the teacher instructs the candidates to process the data (e.g. calculate means or rates of reaction) and plot an appropriate graph. The teacher must not instruct the candidates on the presentation of the data or on the choice of graph or chart. 

    For A2, the teacher instructs the candidates to process the data and carry out a suitable statistical test. The teacher must not instruct the candidates on the choice, implementation and interpretation of the statistical test. 

    For both AS and A2, stage 2 may be done in normal lesson time and must be done in a single session under controlled conditions and in the window of assessment for practical work. Both the raw and the processed data must be handed to the teacher at the end of the session. 

    Stage 1 and Stage 2 may be done in the same session. There is no specified time limit for Stage 2. 

    Stage 3: The EMPA written test 

    The EMPA written test should be taken after completion of Stage 2 and under controlled conditions. Each candidate is provided with an EMPA written test and the candidate's completed Task Sheet indicated on the front cover of the EMPA Written Test. 

    The EMPA test is in two Sections. 

    Section A 

    This consists of a number of questions relating to the candidate's own data. 

    Section B 

    At the start of this section, candidates are supplied with additional data on a related topic. A number of questions relating to analysis and evaluation of the data then follow. 

    The number of marks allocated to each section may vary with each EMPA test. 

    Use of ICT during the EMPA 

    ICT may be used during the EMPA Stages 1 and 2 but teachers should note any restrictions in the Teachers' Notes. Use of the internet is not permitted. 

    Candidates absent for the practical work

     A candidate absent for the practical work (Stage 1) should be given an opportunity to carry out the practical work before they sit the EMPA test. This may be with another group or at a different time. In exceptional cases, when this is not possible, the teacher can supply a candidate with class data. This must be noted on the front cover of the written test. In this case the candidate cannot be awarded marks for Stage 1, collection of data, but can still be awarded marks for Stage 2, processing of data. 

    Material from AQA 

    For each EMPA, AQA will provide: 

    • Teachers' Notes 
    • Task Sheets 1 and 2 
    • EMPA test. 

    When received, this material must be kept under secure conditions. The centre must ensure the security of the material. Further details regarding this material will be provided. 

    Security of assignments 

    Completed EMPAs should be treated like examination papers and kept under secure conditions until sent to the AQA examiner. All other EMPA materials should be kept under secure conditions until publication of results. 

    General Information

    Route X 

    Administration 

    Only one EMPA will be available in any year at AS and at A2. AQA will stipulate a window of assessment during which the EMPA (themed task and written test) must be completed.

    Candidates may make only one attempt at a particular EMPA and redrafting is not permitted at any stage during the EMPA. 

    Only Internally Assessed Units from the Human Biology specification can contribute towards an AS or A Level Award in Human Biology. Biology unit entry codes can not be used towards a Human Biology qualification.

    Work to be submitted 

    The material to be submitted to the AQA examiner for each candidate consists of 

    • the completed Task Sheet 1 and Task Sheet 2 
    • the EMPA written test which includes the Candidate Record Form, including the PSV verification that safe and skilful practical techniques have been demonstrated and reliable and valid observations made. 

    In addition each centre must provide 

    • Centre Declaration Shee
    • Details of any agreed amendments to the task sheet must be notified to the AQA examiner with information supporting the changes from the Assessment Adviser. 

    Working in groups 

    For the PSV, candidates may work in groups provided that any skills being verified are the work of individual candidates. For the EMPA further guidance will be provided but the opportunity for group work will not be a common feature. 

    Other information 

    Section 6 of this specification outlines further guidance on the supervision and authentication of Internally assessed units. 

    Further support 

    AQA supports centres in a number of ways. 

    • Teaching and learning resources which include Instructions for Administration of the EMPA
    • Assessment Advisers appointed by AQA to provide advice on internally assessed units. Every centre is allocated an Assessment Adviser. 

    The Assessment Advisers can provide guidance on issues relating to the carrying out of tasks for assessment. Contact details for your Assessment Adviser can be obtained by emailing your centre name and number to alevelscience@aqa.org.uk 

    Any amendments to the EMPA task sheet must be discussed with the AQA Assessment Adviser and confirmation of the amendments must be submitted to the AQA examiner.

    Mathematical Requirements

    Mathematical Requirements

    Mathematical Requirements

    In order to be able to develop their skills, knowledge and understanding in science, candidates need to have been taught, and to have acquired competence in, the areas of mathematics set out below. Material relevant to the second part of the A Level (A2) only is given in bold type. 

    Candidates should be able to

     

    Arithmetic and computation
    • recognise and use expressions in decimal and standard form 
    • use ratios, fractions and percentages 
    • make estimates of the results of calculations (without using a calculator) 
    • use calculators to find and use mean, standard deviations and , ,
    • understand the meaning of the symbols =, <, >.
    Handling data
    • use an appropriate number of significant figures 
    • find arithmetic means 
    • construct and interpret frequency tables, bar charts and histograms 
    • understand the principles of sampling as applied to biological data 
    • distinguish between chance and probability and understand the importance of chance and probability when interpreting data
    • understand the terms mean, median and mode and standard deviation 
    • use a scatter diagram to identify positive and negative correlation between two variables 
    • select and use a simple statistical test (see Teaching and learning resources for further guidance) 
    • candidates are not required to recall statistical formulae but will be provided with appropriate data sheet when necessary. 
    Algebra
    • change the subject of an equation 
    • substitute numerical values into algebraic equations using appropriate units for physical quantities 
    • understand the use of logarithms in relation to quantities that range over several orders of magnitude.
    Graphs
    • translate information between graphical and numerical forms 
    • plot two variables from experimental or other data using appropriate Institute of Biology conventions 
    • calculate rate of change from a graph showing a linear relationship 
    • draw and use the slope of a tangent to a curve as a measure of rate of change.
    Geometry and trigonometry
    • visualise three dimensional forms from two dimensional representations of three dimensional objects 
    • calculate circumferences and areas of circles, surface areas and volumes of rectangular blocks and cylinders when provided with appropriate formulae.