OCR Level 1/2 GCSE (9–1) in Biology B (Twenty First Century Science) (J257)

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

OCR 21st Century GCSE BIOLOGY B Chapters 4, 5 and 6

'Old' OCR 21st Century GCSE sciences for Y11 finishing 2016-2017

INDEX for all links

Everything below is based on the NEW 2016 official syllabus-specifications for Y10 2016 onwards

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


Syllabus-specification CONTENT INDEX

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

(HT only) means higher tier only (NOT FT) and (GCSE biology only) means the separate science, NOT for Combined Science biology


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

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

Chapter B1.2 How is genetic information inherited?

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

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

Chapter B2.1 What are the causes of disease?

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

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

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

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

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

SUMMARY Chapter B3: Living together – food and ecosystems (separate page, also Com'd Science Biology Chapter B3)

Chapter B3.1 What happens during photosynthesis?

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

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

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

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

Revision summary Chapter B4.1 What happens during cellular respiration?

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

Revision summary Chapter B4.3 How do organisms grow and develop?

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

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

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

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

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

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

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

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

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

SUMMARY Chapter B6: Life on Earth – past, present and future (this page, also Combined Science Biology Chapter B6)

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

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

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

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

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

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

IaS2 What conclusions can we make from data?

IaS3 How are scientific explanations developed?

IaS4 How do science and technology impact society?


Chapter B4: Using food and controlling growth


Chapter B4.1 What happens during cellular respiration?

Consumers gain biomass from other organisms when they eat them. Some of this biomass is converted into molecules of glucose, the fuel for cellular respiration. Cellular respiration involves many chemical reactions and makes molecules of ATP. It occurs in the cytoplasm and mitochondria of animal and plant cells, and in the cytoplasm of microorganisms. ATP is required for processes that are essential for life, including breakdown and synthesis of molecules, active transport and muscle contraction. Aerobic respiration breaks down glucose and combines the breakdown products with oxygen, making water and carbon dioxide (a waste product). In conditions of low or no oxygen (such as in human cells during vigorous exercise, plant root cells in waterlogged soil and bacteria in puncture wounds) anaerobic respiration occurs. There is a partial breakdown of glucose, producing fewer molecules of ATP. In animal cells and some bacteria, this produces lactic acid (a waste product). In plants and some microorganisms, including yeast, it produces ethanol and carbon dioxide.

1. Be able to compare the processes of aerobic and anaerobic respiration, including conditions under which they occur, the inputs and outputs, and comparative yields of ATP.

Practical work: • Investigating the amount of energy released from different foods, by burning them under a boiling tube of water where:

energy (kJ) = mass of water (kg) x change in temperature (deg C) x 4.2 kJ/kg/deg C)

investigating respiration in microorganisms by collecting CO2 given off; which substrate works best?

2. Be able to explain why cellular respiration occurs continuously in all living cells.

3. Be able to explain how mitochondria in eukaryotic cells (plants and animals) are related to cellular respiration.

4. Be able to describe cellular respiration as an exothermic process.

5. (a) Be able to describe practical investigations into the effect of different substrates on the rate of respiration in yeast.

5. (b) Be able to carry out rate calculations for chemical reactions in the context of cellular respiration.


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

Scientific progress often relies on technological developments which enable new observations to be made. The invention of the electron microscope enabled us to observe cell organelles such as mitochondria and chloroplasts at much higher magnification than had previously been possible with light microscopes, and thus to develop explanations about how their structures relate to their roles in cellular processes.

1. Be able to explain how electron microscopy has increased our understanding of sub-cellular structures.

Understand that explanations about the roles of cell organelles were developed from observations that could only be made using electron microscopy.

2. In the context of cells and sub-cellular structures be able to:

(a) demonstrate an understanding of number, size and scale and the quantitative relationship between units

(b) use estimations and explain when they should be used

(c) (HT only) calculate with numbers written in standard form

Introduction to plant and animal cell structure and function


Chapter B4.3 How do organisms grow and develop?

Growth of multicellular organisms involves an increase in the number of body cells. All new cells are created from existing cells when they divide. New body cells are created as part of the cell cycle. During interphase the cell grows larger, the numbers of organelles increase, and each chromosome is copied; then during mitosis the chromosome copies separate, the nucleus divides, and the cell divides to produce two new cells that are genetically identical to one another. Cancer is a non-communicable disease in humans caused by changes in a person’s DNA. The changes cause a cell to divide many times by mitosis, which can create a tumour.

1. (a) Be able to describe the role of the cell cycle in growth, including interphase and mitosis b) Be able to describe how to use a light microscope to observe stages of mitosis. You are not expected to recall intermediate phases.

Practical work - investigating mitosis using a microscope to look at stained cells from onion root tip

2. Be able to describe cancer as the result of changes in cells that lead to uncontrolled growth and division.

Gametes are produced by meiosis, a different type of cell division. After interphase (during which the chromosome number has doubled), two meiotic divisions occur. Gametes contain half the number of chromosomes found in body cells (one chromosome from each pair). At fertilisation, maternal and paternal chromosomes pair up, so the zygote has the normal chromosome number.

3. Be able to explain the role of meiotic cell division in halving the chromosome number to form gametes, including the stages of interphase and two meiotic divisions. You are not expected to recall intermediate phases.

Consideration of factors that increase the risk of developing cancer.

A zygote divides by mitosis to form an embryo. All of the cells in an embryo are initially identical and unspecialised; these are embryonic stem cells, and can become specialised to form any type of cell (differentiation) by switching genes off and on. Most cells in a human embryo become specialised after the eight cell stage. However, some (adult stem cells) remain unspecialised and can become specialised later to become many, but not all, types of cells.

In plants, only cells in meristems undergo mitosis, producing unspecialised cells that can develop into any kind of plant cell.

4. Be able to describe the function of stem cells in embryonic and adult animals and meristems in plants

5. Be able to explain the importance of cell differentiation, in which cells become specialised by switching genes off and on to form tissues with particular functions.


Chapter B4.4 How is plant growth controlled?  (Separate science GCSE Biology Only, NOT Combined Science))

Plants are able to respond to their environment in different ways, e.g. phototropism in shoots and gravitropism in roots. These responses are controlled and coordinated by a group of plant hormones called auxins, and increase a plant’s chances of survival.

(HT only) Plants can also respond to environmental factors using other hormones. Gibberellins are involved in breaking seed dormancy (germination) in response to water, and bolting (production of flowers in an attempt to reproduce before death) in response to cold or lack of water. Ethene is involved in the ripening of fruit and dropping of leaves. Humans can exploit these responses and others such as triggering rooting in cuttings, by using plant hormones to trigger responses that are advantageous to us.

1. (a) Be able to explain how plant hormones are important in the control and coordination of plant growth and development, with reference to the role of auxins in phototropisms and gravitropisms.

1. (b) Be able to describe practical investigations into the role of auxin in phototropism.

Practical work: Investigating phototropism and the role of auxins in seedlings, using directional light sources and foil caps and rings.

2. (HT only) Be able to describe some of the variety of effects of plant hormones, relating to gibberellins and ethene.

3. (HT only) Be able to describe some of the different ways in which people use plant hormones to control plant growth.


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

Stem cells offer the potential to treat patients by replacing damaged tissues or cells. But the benefits must be weighed against risks and ethical concerns about the use and destruction of human embryos to collect embryonic stem cells. For these reasons, use of stem cells in research and medicine is subject to government regulation in many countries.

1. Be able to discuss potential benefits, risks and ethical issues associated with the use of stem cells in medicine.

stem cell therapy for neuron damage

stem cell therapy as an application of science that could change lives

risks, benefits and ethical issues associated with use of stem cells in medicine


Chapter B5: The human body – staying alive


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

Oxygen, water and molecules from food are essential for chemical reactions in cells in the human body, including cellular respiration and synthesis of biomass. Carbon dioxide and urea are waste products that need to be removed from cells before they reach toxic levels. Moving these substances into, around and out of the body depends upon interactions between the circulatory, gaseous exchange, digestive and excretory systems.

Oxygen and carbon dioxide diffuse between blood in capillaries and air in alveoli. Water and dissolved food molecules are absorbed from the digestive system into blood in capillaries. Waste products including carbon dioxide and urea diffuse out of cells into the blood. Urea is filtered out of the blood by the kidneys into urine. Partially-permeable cell membranes regulate the movement of these substances; gases move across the membranes by diffusion, water by osmosis and some other substances by active transport.

The heart, blood vessels, red blood cells and plasma are adapted to transport substances around the body.

1. Be able to describe some of the substances transported into and out of the human body in terms of the requirements of cells, including oxygen, carbon dioxide, water, dissolved food molecules and urea.

Practical work: dissecting a lamb's heart to observe atria, ventricles and valves

investigating the valves in an arm vein (tourniquet around bicep; when veins become prominent, gently try to push blood in each direction)

2. Be able to explain how the partially-permeable cell membranes of animal cells are related to diffusion, osmosis and active transport.

3. Be able to describe the human circulatory system, including its relationships with the gaseous exchange system, the digestive system and the excretory system.

4. Be able to explain how the structure of the heart is adapted to its function, including cardiac muscle, chambers and valves.

5. Be able to explain how the structures of arteries, veins and capillaries are adapted to their functions, including differences in the vessel walls and the presence of valves.

6. Be able to explain how red blood cells and plasma are adapted to their functions in the blood.

To sustain all the living cells inside humans and other multi-cellular organisms, exchange surfaces increase the surface area:volume ratio, and the circulatory system moves substances around the body to decrease the distance they have to diffuse to and from cells.

7. Be able to explain the need for exchange surfaces and a transport system in multicellular organisms in terms of surface area : volume ratio

Practical work: Investigating the effect of surface area : volume ratio on diffusion of dye into agar cubes.

8. Be able to calculate surface area : volume ratios.


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

In order to survive, organisms need to detect and respond to changes in their external and internal environments. The highly adapted structures of the nervous system facilitate fast, short-lasting responses to stimuli.

In a stimulated neuron, an electrical impulse passes along the axon. Most axons have a fatty sheath to increase impulse transmission speed. An impulse is transmitted from one neuron to another across a synapse by the release of transmitter substances, which diffuse across the gap and bind to receptors on the next neuron, stimulating it.

1. Be able to explain how the components of the nervous system work together to enable it to function, including sensory receptors, sensory neurons, the CNS, motor neurons and effectors.

2. Be able to explain how the structures of nerve cells and synapses relate to their functions. You are not expected to explain nerve impulse transmission in terms of membrane potentials.

Reflexes provide rapid, involuntary responses without involving a processing centre, and are essential to the survival of many organisms. In some circumstances the brain can modify a reflex response via a neuron to the motor neuron of the reflex arc (e.g. to stop us dropping a hot object).

3. (a) Be able to explain how the structure of a reflex arc, including the relay neuron, is related to its function.

3. (b) Be able to describe practical investigations into reflex actions

Research into the structure and function of the brain has huge potential impact for the ageing population. We know the brain is made of billions of neurons. We also know that different areas of the brain are important in different functions.

(GCSE HT Biology only) However, our ability to investigate and develop explanations about brain function remains limited.

(GCSE HT Biology only) Most areas of the brain are concerned with many functions, but some functions can be mapped to particular areas using functional magnetic resonance imaging (fMRI), studies of patients with brain damage, and electrical stimulation. There are ethical issues associated with studying brain damaged patients, including informed consent.

4. (GCSE Biology only) Be able to describe the structure and function of the brain and roles of the cerebral cortex (intelligence, memory, language and consciousness), cerebellum (conscious movement) and brain stem (regulation of heart and breathing rate)

 fMRI as a technological development that enabled observations that led to new scientific explanations.

5. (GCSE HT Biology only) Be able to explain some of the difficulties of investigating brain function.

ethical issues around studying brain damaged patients


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

The endocrine system of humans and other animals uses hormones, secreted by glands and transported by the blood, to enable the body to respond to external and internal stimuli. Hormones bind to receptors on effectors, stimulating a response. The endocrine system provides slower, longer-lasting responses than the nervous system.

(HT only) The production of hormones is regulated by negative feedback.

1. Be able to describe the principles of hormonal coordination and control by the human endocrine system

2. (HT only) Be able to explain the roles of thyroxine and adrenaline in the body, including thyroxine as an example of a negative feedback system.


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

Cells, enzymes and life processes function only in certain conditions, and optimally when conditions are within a narrow range. The maintenance of a constant internal environment is homeostasis, and depends on receptors, nerves, hormones and (often antagonistic) effectors to counteract changes.

(GCSE Biology only) The skin and muscles (including muscles in artery walls and hair follicles) work to control internal body temperature.

(GCSE Biology HT only) Maintenance of an ideal internal temperature depends on temperature receptors in the skin and hypothalamus, processing in the hypothalamus, responses such as sweating, hair erection, shivering, vasoconstriction and vasodilation, and negative feedback.

(GCSE Biology only) The kidneys filter water and urea from the blood into kidney tubules then reabsorb as much water as required, to maintain the water balance of the body. This helps to ensure the blood plasma is at the correct concentration to prevent the shrinking or bursting of cells due to osmosis.

((GCSE Biology HT only) Maintenance of an ideal water balance depends on receptors and processing in the hypothalamus, response by the pituitary gland (increased/decreased ADH production), and negative feedback.

1. Be able to explain the importance of maintaining a constant internal environment in response to internal and external change.

 the effects of temperature on enzyme activity

Practical work: Comparing skin temperature and core body temperature under different conditions

Modelling the control of temperature by trying to keep a beaker of water at 40°C using just a Bunsen burner (single effector) compared to a Bunsen burner and ice (antagonistic effectors).

2. (a) (GCSE Biology only) Be able to describe the function of the skin in the control of body temperature, including changes to sweating, hair erection and blood flow.

2. (b) (GCSE Biology only) Be able to describe practical investigations into temperature control of the body.

3. (GCSE Biology HT only) Be able to explain the response of the body to different temperature challenges, including receptors, processing, responses and negative feedback.

4. (GCSE Biology only) Be able to explain the effect on cells of osmotic changes in body fluids. You are not expected to discuss water potential.

5. (GCSE Biology only) Be able to describe the function of the kidneys in maintaining the water balance of the body, including filtering water and urea from the blood into kidney tubules then reabsorbing as much water as required.

6. (GCSE Biology HT only) Be able to describe the effect of ADH on the permeability of the kidney tubules.

7. (GCSE Biology HT only) Be able to explain the response of the body to different osmotic challenges, including receptors, processing, response, and negative feedback.

8./2. In the context of maintaining a constant internal environment be able to:

(a) extract and interpret data from graphs, charts and tables

(b) translate information between numerical and graphical forms


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

Hormones play a vital role in enabling sexual reproduction in humans: they regulate the menstrual cycle, including ovulation, in adult females. Without this process, sexual reproduction would not be possible.

(HT only) A number of hormones interact to control the menstrual cycle:

FSH causes the ovaries to develop a follicle containing an egg, and produce oestrogen

oestrogen causes the uterus wall to thicken

LH causes the follicle to release the egg (ovulation)

the remains of the follicle secrete progesterone

progesterone prepares the lining of the uterus for implantation of a fertilised egg

oestrogen and progesterone stop the production of LH and FSH

as progesterone levels fall, the thickened uterus wall breaks down and is discharged (menstruation).

1. Be able to describe the role of hormones in human reproduction, including the control of the menstrual cycle.

2. (HT only) Be able to explain the interactions of FSH, LH, oestrogen and progesterone in the control of the menstrual cycle.

The menstrual cycle can be controlled artificially by the administration of hormones, often as an oral pill. The hormones prevent ovulation, so can be used as a contraceptive, but they do not decrease the risk of sexual transmission of communicable diseases.

3. Be able to explain the use of hormones in contraception and evaluate hormonal and non-hormonal methods of contraception.

sexually transmitted disease

risk in the context of sex and contraception

(HT only) Hormones can also be used to artificially manipulate the menstrual cycle as a treatment in certain cases of female infertility in which follicle development and ovulation do not occur successfully. The use of hormones to treat infertility is an example of an application of science that has made a significant positive difference to people’s lives.

4. (HT only) Be able to explain the use of hormones in modern reproductive technologies to treat infertility Ideas.

 infertility treatment as an application of science that makes a positive difference to lives (IaS4)


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

Blood sugar level is controlled by insulin and (HT only) glucagon acting antagonistically.

Type 1 diabetes arises when the pancreas stops making insulin; blood sugar can be regulated using insulin injections. Type 2 diabetes develops when the body no longer responds to its own insulin or does not make enough insulin; blood sugar can be regulated using diet (high in complex carbohydrates), exercise and insulin injections.

1. Be able to explain how insulin controls the blood sugar level in the body.

2. (HT only) Be able to explain how glucagon and insulin work together to control the blood sugar level in the body.

3. Be able to compare type 1 and type 2 diabetes and explain how they can be treated.

The rest of B5.6 is for separate science GCSE Biology only, NOT combined science.

(GCSE Biology only) The human eye is an important sense organ. Tissues in the eye are adapted to enable it to function. Damage or degradation of tissues and cells in the eye can impair sight. Ray diagrams can be used to model some of these problems and how they can be overcome.

4. (GCSE Biology only) (a) Be able to explain how the main structures of the eye are related to their functions, including the cornea, iris, lens, ciliary muscle and retina and to include the use of ray diagrams.

4.  (GCSE Biology only) (b) Be able to describe practical investigations into the response of the pupil in different light conditions.

 lenses and ray diagrams

Practical work:

investigating the diameter of the pupil in different light conditions

investigating the focusing of light using lenses

5. (GCSE Biology only) Be able to describe common defects of the eye, including short-sightedness, long-sightedness and cataracts, and explain how these problems may be overcome, including using ray diagrams to illustrate the effect of lenses

(GCSE Biology HT only) Damage to neurons can lead to debilitating illness. Neurons, once differentiated, do not undergo mitosis, so cannot divide to replace lost neurons; this means damage to the nervous system can be difficult or impossible to treat. Research into the use of stem cells to replace damaged cells of the nervous system offers the potential to improve the lives of people with nervous system injury and disease, but the ethics of stem cells use must also be considered.

6. (GCSE Biology HT only) Be able to explain some of the limitations in treating damage and disease in the brain and other parts of the nervous system.

Is it right to use stem cells in medicine?

(HT only) Stem cell therapy as an application of science that could change lives


Chapter B6: Life on Earth – past, present and future


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

The modern theory of evolution by natural selection combines ideas about genes, variation, advantage and competition to explain how the inherited characteristics of a population can change over a number of generations. It includes the ideas that: Mutations in DNA create genetic variants, which may be inherited. Most genetic variants do not affect phenotype, but those that do may increase an organism’s ability to survive in its environments and compete for resources (i.e. confer an advantage). Individuals with an advantage are more likely to reproduce; thus, by natural selection, the proportion of individuals possessing beneficial genetic variants increases in subsequent generations. A new species can arise if the organisms in a population evolve to be so different from their ancestors that they could no longer mate with them to produce fertile offspring. Speciation is more likely to occur when two populations of an organism are isolated.

1. Be able to state that there is usually extensive genetic variation within a population of a species.

2. Be able to recall that genetic variants arise from mutations, and that most have no effect on the phenotype, some influence phenotype and a very few determine phenotype.

3. Be able to explain how evolution occurs through natural selection of variants that give rise to phenotypes better suited to their environment.

4. Be able to explain the importance of competition in a community, with regard to natural selection.

5. Be able to describe evolution as a change in the inherited characteristics of a population over a number of generations through a process of natural selection which may result in the formation of new species Charles Darwin noticed that the selective breeding of plants and animals had produced new varieties with many beneficial characteristics, quite different to their wild ancestors. Most of what we eat, and our ability to feed the growing human population depends on selectively bred plants and animals. Darwin wondered whether a similar process of selection in nature could have created new species.

Charles Darwin noticed that the selective breeding of plants and animals had produced new varieties with many beneficial characteristics, quite different to their wild ancestors. Most of what we eat, and our ability to feed the growing human population depends on selectively bred plants and animals. Darwin wondered whether a similar process of selection in nature could have created new species.

6. Be able to explain the impact of the selective breeding of food plants and domesticated animals.

The theory of evolution by natural selection was developed to explain observations made by Darwin, Wallace and other scientists, including:

the production of new varieties of plants and animals by selective breeding

fossils with similarities and differences to living species

the different characteristics shown by isolated populations of the same species living in different ecosystems.

The development of the theory is an example of how scientists develop explanations. Darwin: made observations of the natural world; suggested natural selection to explain differences between fossils and living organisms, and between isolated populations; used ideas from Wallace and other scientists to improve his explanation; and shared his explanation with the scientific community.

7. Be able to describe how fossils provide evidence for evolution.

the theory of evolution by natural selection as an example of how scientific explanations are developed

8. (GCSE Biology only) Be able to describe the work of Darwin and Wallace in the development of the theory of evolution by natural selection.

The theory of evolution by natural selection illustrates how scientists continue to test a proposed explanation by making new observations and collecting new evidence, and how if the explanation is able to explain these it can become widely accepted by the scientific community. For example, the spread of antibiotic resistance in bacteria can be explained by mutation, advantage and natural selection.

9./8. Be able to describe modern examples of evidence for evolution including antibiotic resistance in bacteria.

The theory of evolution by natural selection as a scientific explanation modified in light of new observations and ideas.

Most scientists accept the modern theory of evolution because it is the best explanation for many of our observations of the natural world. However, some people do not accept it either because they are unaware of (or do not understand) the evidence, or because it does not fit with their beliefs.

10. (GCSE Biology only) Be able to explain the impact of these ideas on modern biology and society.

reasons why different people do or do not accept an explanation


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

The evolution of a population or species is affected by whether the individual organisms reproduce sexually or asexually. Sexual reproduction occurs at a slower rate than asexual reproduction, but provides genetic variation in the offspring.

1. Be able to explain some of the advantages and disadvantages of asexual and sexual reproduction in a range of organisms


Chapter B6.3 How does our understanding of biology help us classify the diversity of organisms on Earth?

GCSE Combined Science Chapter B6.2

The enormous diversity of organisms on Earth can be classified into groups on the basis of observed similarities and differences in their physical characteristics and, more recently, their DNA. We are more likely to classify species into the same group if there are lots of similarities in their genomes (i.e. if they have many genes, and genetic variants, in common). Genome analysis can also suggest whether different groups have a common ancestor, and how recently speciation occurred.

1. Be able to describe the impact of developments in biology on classification systems, including the use of DNA analysis to classify organisms


Chapter B6.4 How is biodiversity threatened and how can we protect it?

GCSE Combined Science Chapter B6.3

The biodiversity of the Earth, or of a particular area, is the combination of the diversity of living organisms, the diversity of genes these organisms have, and the diversity of ecosystems. The biodiversity of many areas is being reduced by activities related to increasing human population size, industrialisation and globalisation. Such interactions can result in ecosystems being damaged or destroyed, populations dying out, and species becoming extinct when conditions change more quickly than they can adapt. Humans can interact with ecosystems positively by using ecosystem resources in a sustainable way (at the same rate as they can be replaced), and by protecting and conserving biodiversity. All organisms, including humans, depend on other organisms and the environment for their survival. Protecting and conserving biodiversity will help ensure we can continue to provide the human population with food, materials and medicines. Biodiversity can be protected at different levels, including protection of individual species, protection of ecosystems, and control of activities that contribute to global climate change. Decisions about protecting and conserving biodiversity are affected by ecological, economic, moral and political issues.

1. Be able to describe both positive and negative human interactions within ecosystems and explain their impact on biodiversity.

greenhouse gases and global warming

the impacts of science on biodiversity, including negative impacts and potential solutions

decision making in the context of the protection and conservation of biodiversity

Practical work: Measuring living and non-living indicators to assess the effect of pollution on organisms

2. (GCSE Biology HT only) Be able to evaluate evidence for the impact of environmental changes on the distribution of organisms, with reference to water and atmospheric gases

3. (GCSE Biology only)  Be able to describe some of the biological factors affecting levels of food security including increasing human population, changing diets in wealthier populations, new pests and pathogens, environmental change, sustainability and cost of agricultural inputs.

4./2. Be able to explain some of the benefits and challenges of maintaining local and global biodiversity.

5./3. Be able to extract and interpret information related to biodiversity from charts, graphs and tables.

6. (GCSE Biology only) Be able to describe and explain some possible biotechnological and agricultural solutions, including genetic modification, to the demands of the growing human population


Chapter B7: Ideas about Science (GCSE Combined Science BCP7)


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

The aim of science is to develop good explanations for natural phenomena. There is no single ‘scientific method’ that leads to good explanations, but scientists do have characteristic ways of working. In particular, scientific explanations are based on a cycle of collecting and analysing data. Usually, developing an explanation begins with proposing a hypothesis. A hypothesis is a tentative explanation for an observed phenomenon (“this happens because…”). The hypothesis is used to make a prediction about how, in a particular experimental context, a change in a factor will affect the outcome. A prediction can be presented in a variety of ways, for example in words or as a sketch graph. In order to test a prediction, and the hypothesis upon which it is based, it is necessary to plan an experimental strategy that enables data to be collected in a safe, accurate and repeatable way.

1. in given contexts use scientific theories and tentative explanations to develop and justify hypotheses and predictions

2. suggest appropriate apparatus, materials and techniques, justifying the choice with reference to the precision, accuracy and validity of the data that will be collected

3. recognise the importance of scientific quantities and understand how they are determined

4. identify factors that need to be controlled, and the ways in which they could be controlled

5. suggest an appropriate sample size and/or range of values to be measured and justify the suggestion

6. plan experiments or devise procedures by constructing clear and logically sequenced strategies to: - make observations - produce or characterise a substance - test hypotheses - collect and check data - explore phenomena

7. identify hazards associated with the data collection and suggest ways of minimizing the risk

8. use appropriate scientific vocabulary, terminology and definitions to communicate the rationale for an investigation and the methods used using diagrammatic, graphical, numerical and symbolic forms


Chapter IaS2 What conclusions can we make from data?

The cycle of collecting, presenting and analysing data usually involves translating data from one form to another, mathematical processing, graphical display and analysis; only then can we begin to draw conclusions. A set of repeat measurements can be processed to calculate a range within which the true value probably lies and to give a best estimate of the value (mean). Displaying data graphically can help to show trends or patterns, and to assess the spread of repeated measurements. Mathematical comparisons between results and statistical methods can help with further analysis.

1. present observations and other data using appropriate formats

2. when processing data use SI units where appropriate (e.g. kg, g, mg; km, m, mm; kJ, J) and IUPAC chemical nomenclature unless inappropriate

3. when processing data use prefixes (e.g. tera, giga, mega, kilo, centi, milli, micro and nano) and powers of ten for orders of magnitude

4. be able to translate data from one form to another

5. when processing data interconvert units

6. when processing data use an appropriate number of significant figures

7. when displaying data graphically select an appropriate graphical form, use appropriate axes and scales, plot data points correctly, draw an appropriate line of best fit, and indicate uncertainty (e.g. range bars)

8. when analysing data identify patterns/trends, use statistics (range and mean) and obtain values from a line on a graph (including gradient, interpolation and extrapolation)

Data obtained must be evaluated critically before we can make conclusions based on the results. There could be many reasons why the quality (accuracy, precision, repeatability and reproducibility) of the data could be questioned, and a number of ways in which they could be improved. Data can never be relied on completely because observations may be incorrect and all measurements are subject to uncertainty (arising from the limitations of the measuring equipment and the person using it). A result that appears to be an outlier should be treated as data, unless there is a reason to reject it (e.g. measurement or recording error)

9. in a given context evaluate data in terms of accuracy, precision, repeatability and reproducibility, identify potential sources of random and systematic error, and discuss the decision to discard or retain an outlier

10. evaluate an experimental strategy, suggest improvements and explain why they would increase the quality (accuracy, precision, repeatability and reproducibility) of the data collected, and suggest further investigations.

Agreement between the collected data and the original prediction increases confidence in the tentative explanation (hypothesis) upon which the prediction is based, but does not prove that the explanation is correct. Disagreement between the data and the prediction indicates that one or other is wrong, and decreases our confidence in the explanation.

11. in a given context interpret observations and other data (presented in diagrammatic, graphical, symbolic or numerical form) to make inferences and to draw reasoned conclusions, using appropriate scientific vocabulary and terminology to communicate the scientific rationale for findings and conclusions

12. explain the extent to which data increase or decrease confidence in a prediction or hypothesis


Chapter IaS3 How are scientific explanations developed?

Scientists often look for patterns in data as a means of identifying correlations that can suggest cause-effect links – for which an explanation might then be sought. The first step is to identify a correlation between a factor and an outcome. The factor may then be the cause, or one of the causes, of the outcome. In many situations, a factor may not always lead to the outcome, but increases the chance (or the risk) of it happening. In order to claim that the factor causes the outcome we need to identify a process or mechanism that might account for the observed correlation.

1. use ideas about correlation and cause to: - identify a correlation in data presented as text, in a table, or as a graph - distinguish between a correlation and a cause-effect link - suggest factors that might increase the chance of a particular outcome in a given situation, but do not invariably lead to it - explain why individual cases do not provide convincing evidence for or against a correlation - identify the presence (or absence) of a plausible mechanism as reasonable grounds for accepting (or rejecting) a claim that a factor is a cause of an outcome.

Risk factors for noncommunicable disease (B2.5)

Scientific explanations and theories do not ‘emerge’ automatically from data, and are separate from the data. Proposing an explanation involves creative thinking. Collecting sufficient data from which to develop an explanation often relies on technological developments that enable new observations to be made. As more evidence becomes available, a hypothesis may be modified and may eventually become an accepted explanation or theory. A scientific theory is a general explanation that applies to a large number of situations or examples (perhaps to all possible ones), which has been tested and used successfully, and is widely accepted by scientists. A scientific explanation of a specific event or phenomenon is often based on applying a scientific theory to the situation in question.

2. describe and explain examples of scientific methods and theories that have developed over time and how theories have been modified when new evidence became available.

Mendel’s work on inheritance (B1.2, HT only) The theory of natural selection (B6.1) Explanations that relied on technological development: Roles of cell organelles (B4.2) Brain function (B5.3

Findings reported by an individual scientist or group are carefully checked by the scientific community before being accepted as scientific knowledge. Scientists are usually sceptical about claims based on results that cannot be reproduced by anyone else, and about unexpected findings until they have been repeated (by themselves) or reproduced (by someone else). Two (or more) scientists may legitimately draw different conclusions about the same data. A scientist’s personal background, experience or interests may influence his/her judgments. An accepted scientific explanation is rarely abandoned just because new data disagree with it. It usually survives until a better explanation is available.

3. describe in broad outline the ‘peer review’ process, in which new scientific claims are evaluated by other scientists.

Models are used in science to help explain ideas and to test explanations. A model identifies features of a system and rules by which the features interact. It can be used to predict possible outcomes. Representational models use physical analogies or spatial representations to help visualise scientific explanations and mechanisms. Descriptive models are used to explain phenomena. Mathematical models use patterns in data of past events, along with known scientific relationships, to predict behaviour; often the calculations are complex and can be done more quickly by computer. Models can be used to investigate phenomena quickly and without ethical and practical limitations, but their usefulness is limited by how accurately the model represents the real world.

4. use a variety of models (including representational, spatial, descriptive, computational and mathematical models) to: - solve problems - make predictions - develop scientific explanations and understanding - identify limitations of models

Letters (ATCG) - the genetic code (B1.1) Punnett squares for single-gene inheritance (B1.2) Lock and key for enzyme action (B3.1) Food webs and (HT only) pyramids of biomass (B3.3)

Ray diagrams for focussing of light in the eye (B5.6)


Chapter IaS4 How do science and technology impact society?

Science and technology provide people with many things that they value, and which enhance their quality of life. However some applications of science can have unintended and undesirable impacts on the quality of life or the environment. Scientists can devise ways of reducing these impacts and of using natural resources in a sustainable way (at the same rate as they can be replaced). Everything we do carries a certain risk of accident or harm. New technologies and processes can introduce new risks. The size of a risk can be assessed by estimating its chance of occurring in a large sample, over a given period of time.
To make a decision about a course of action, we need to take account of both the risks and benefits to the different individuals or groups involved. People are generally more willing to accept the risk associated with something they choose to do than something that is imposed, and to accept risks that have short-lived effects rather than long-lasting ones. People’s perception of the size of a particular risk may be different from the statistically estimated risk. People tend to over-estimate the risk of unfamiliar things (like flying as compared with cycling), and of things whose effect is invisible or long-term (like ionising radiation). Some forms of scientific research, and some applications of scientific knowledge, have ethical implications. In discussions of ethical issues, a common argument is that the right decision is one which leads to the best outcome for the greatest number of people. Scientists must communicate their work to a range of audiences, including the public, other scientists, and politicians, in ways that can be understood. This enables decision-making based on information about risks, benefits, costs and ethical issues.

1. describe and explain everyday examples and technological applications of science that have made significant positive differences to people’s lives

2. identify examples of risks that have arisen from a new scientific or technological advance

3. for a given situation: - identify risks and benefits to the different individuals and groups involved - discuss a course of action, taking account of who benefits and who takes the risks - suggest reasons for people’s willingness to accept the risk - distinguish between perceived and calculated risk.

4. suggest reasons why different decisions on the same issue might be appropriate in view of differences in personal, social, economic or environmental context, and be able to make decisions based on the evaluation of evidence and arguments.

5. distinguish questions that could in principle be answered using a scientific approach, from those that could not; where an ethical issue is involved clearly state what the issue is and summarise the different views that may be held.

6. explain why scientists should communicate their work to a range of audiences.

Positive applications of science: Genetic engineering (B1.3) Monoclonal antibodies (B2.3, B2.6) Infertility treatment (B5.5) Stem cell therapy (B4.7, B5.6 HT only) Environmental conservation and sustainability (B6.4) Unintended impacts: Biodiversity loss (B6.4) Considering risks, benefits and ethical issues: Gene technology (B1.3) Disease prevention (B2.4) Risk factors for noncommunicable diseases (B2.5)


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