OCR Gateway GCSE (9-1) Biology Teacher Pack sample pages by Collins

Chapter 1: Cell level systems

Cell level systems: Introduction

Chapter 1: Cell level systems

• Test a leaf for the presence of starch • Investigate the effect of amylase on starch

When and how to use these pages

• Practical: Investigate the effect of pH on the rate of reaction of amylase enzyme

This chapter builds on the idea that the cell is the building block of life. Plant, animal and bacteria cells are studied using microscopy and important cell level processes of photosynthesis and respiration are explored. This chapter links to all chapters in which the structure and functions of different systems are considered. There are links to Chapter 5, Genes, inheritance and selection, and several spreads in Chapter 2 Scaling up, particularly to 2.5 Cell division and 2.8 Cell development.

• Practical: Use qualitative reagents to test for a range of carbohydrates, lipids and proteins • Practical: Investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed

Lesson title

Overarching objectives

Overview of the chapter In this chapter, students will learn about the structure of plant, animal, prokaryotic and eukaryotic organisms, and the functions of major structures. They will compare the level of detail revealed by light and electron microscopes, calculating magnifications. Students will investigate the structure of DNA and how the DNA base code is used to synthesise proteins. They will then learn about the role of enzymes in digestion and investigate the effect of pH on enzyme activity. Students will consider the differences between aerobic and anaerobic respiration, and learn about the uses of anaerobic respiration in baking and brewing. Students will learn about the process of photosynthesis, including the many uses of glucose in the plant. They will also test a leaf for the presence of starch and investigate how to change the rate of photosynthesis.

1 The light microscope

How to observe animal and plant cells using the light microscope and its limitations.

2 Looking at cells

Describe the structure of eukaryotic cells and functions of subcellular components.

3 Practical: Using a light How to look at everyday material and cells using a light microscope. microscope to observe and Understand the difference between low and high power;; draw and record animal and plant cells describe images at high and low magnification. 4 Primitive cells

This chapter offers a number of opportunities for the students to use mathematics to carry out magnification calculations, plan and carry out investigations into the use of anaerobic respiration in baking, plan and carry out investigations into factors affecting photosynthesis.

Describe the differences between prokaryotic and eukaryotic cells, and how they might have evolved over time.

5 Looking at cells in more detail

Compare the light microscope with the electron microscope, explaining how the development of the electron microscope has increased our understanding of cells.

Obstacles to learning

6 Maths skills: Size and number

Making estimates, ratio and proportion, standard and decimal form.

Students may need extra guidance with the following terms and concepts:

7 The structure of DNA

Describe the structure of DNA in terms of DNA bases, double helix structure and having complementary strands.

8 Proteins

Describe how proteins are synthesise according to the DNA template of a gene.

9 Explaining enzymes

Describe what enzymes are and how they work.

• Cells and related topics use abstract concepts and are hard to visualise. The use of cell models may help

some students to make connections between different types of cells. Students often believe that cells are inactive, two-dimensional structures and the use of videos and electron micrographs will enable them to see this is not the case.

• Students may believe that bacterial cells are the same as animal cells. • Understanding exactly how proteins are synthesised using the DNA code can become extremely complex.

10 Practical: Investigating the effect of pH on the rate of reaction of amylase enzyme

Investigate the effect of pH on the rate of reaction of amylase enzyme.

11 Cells at work

Explain the process of aerobic respiration.

12 Living without oxygen

Describe the process of anaerobic respiration and compare it to aerobic respiration.

13 Enzymes at work

Investigating the digestive enzymes.

• Students need to appreciate that the process of photosynthesis only produces sugars. All the other

14 Practical: Use qualitative reagents to test for a range of carbohydrates, lipids and proteins

Use qualitative reagents to test for a range of carbohydrates, lipids and proteins

• Many students, even at A level, think that plants respire at night and then switch to photosynthesis during the

15 Looking at photosynthesis

Explain how plants use the products of photosynthesis.

16 Explaining photosynthesis

Describe the process of photosynthesis.

Practicals in this chapter

17 Practical: rate of photosynthesis

Investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pond weed.

In this unit students will do the following practical work:

18 Increasing photosynthesis

Identify factors that affect the rate of photosynthesis and explain the interaction of factors in limiting the rate of photosynthesis.

19 Maths skills: Extracting and interpreting information

To extract and interpret information from tables, charts and graphs.

This topic should be avoided with students that will definitely only be entered for the foundation tier.

• Most students will understand that enzymes speed up reactions but few will understand why. Opportunities to interpret enzyme-controlled reactions will help with this understanding.

• Respiration is often confused with breathing (ventilation), and needs to be linked to the mitochondria within cells so its role within each cell can be emphasised.

substances that a plant needs are made from this sugar and plants often need additional minerals to supply other elements. day. The continual nature of respiration needs to be emphasised.

• Practical: Prepare plant and animal slides and observe them using a light microscope • Modelling DNA structure • Investigate the amount of energy in food OCR GCSE Biology: Teacher Pack

OCR GCSE Biology: Teacher Pack

Chapter 2: Scaling up

Lesson 8: Key concept: Cell development Lesson overview

They should discuss animal and plant cloning in pairs and compare the use of meristems in plant cloning with animal cloning, on the worksheet. [O3] Explain

• Ask students to explain how different cells, or organisms, divide and what form they become in the end. They

OCR specification reference

should answer this on the worksheet. [O1, O2, O3]

OCR B2.1b; OCR B2.1c; OCR B2.1d; OCR B2.1e; OCR B2.1f

Consolidate and apply

Learning objectives • Give examples of where mitosis is necessary to produce identical daughter cells. • Understand the need for reduction division, meiosis. • Describe the use and potential of cloned cells in biological research.

• Ask students to write a short article to explain what is meant by cloning and describe some potential uses of

this. Students should also highlight the ethical considerations of using stems cells. They should include ideas about mitosis in their article [O1, O2, O3]

Extend

Learning outcomes

Ask students who are able to progress further to:

• Make links between cell structure, cell division and stem cells. [O1] • Describe the process of mitosis. [O2] • Compare the use of meristems in cloning with animal cell cloning. [O3]

• find out more about other types of cell division, for example, budding. They could compare and contrast

Skills development

• Ask students to write the definitions of all the words on their word wall.

• WS 1.1b Use models to solve problems, make predictions and to develop scientific explanations and

• They should make up at least five short paragraphs connecting words from each section of the word wall

mitosis, meiosis, budding and forms of asexual reproduction. [O1]

Plenary suggestions

understanding of familiar and unfamiliar facts.

together.

• WS 1.1e Explain everyday and technological applications of science. • WS 1.4a Use scientific vocabulary, terminology and definitions.

Answers to Worksheets 2.8.1 and 2.8.2

Resources needed Worksheet 2.8.1 (low and standard demand); Worksheet 2.8.2 (high demand) Digital resources Presentation 2.8 Key vocabulary differentiation, gamete, meiosis, mitosis

Teaching and learning Engage • Ask students to work in pairs to make a word wall on poster paper. They should split the paper into four

sections. On each of the sections they should discuss and write down all the words relating to animal cells, plant cells, cell division and cloning, respectively. [O1]

• Students should join another pair and compare the words on their posters. Discuss and check students’ ideas as a class and ask them to add in any omissions. [O1]

Challenge and develop • Model the process of mitosis by gently blowing into a solution of bubbles. New bubbles are made from the original ones. Discuss the idea of cell growth, establishing that it occurs by the formation of new cells, and not simply the enlargement of old ones. [O2]

Worksheet 2.8.1 Cell division 1. b), d), a), c) 2. a. Mitosis – two new animal cells – identical daughter cells to each other and to parent cell b. Mitosis – two now plant cells – identical daughter cells to each other and to parent cell c. Mitosis – differentiated cells – identical daughter cells – different from parent cell d. Mitosis – differentiated cells – identical daughter cells – different from parent cell e. Budding – two new yeast cells – identical daughter cells to each other and to parent cell Worksheet 2.8.2 Meiosis and mitosis 1. Mitosis results in growth, so the new cells must have the same function as the original cell as they will belong to the same tissues.The cells must be identical. 2. Meiosis results in the formation of gametes, which must fuse together to become a new cell. The two gametes must have half the number of chromosomes in order for the new cell to have a complete set of chromosomes, and not a double set. Cell division

• Show students the image from the PowerPoint slide asking what mitosis is. Discuss the images and show

students some cells that are actively carrying out mitosis. Discuss what the cells are doing and help students to identify the meaning of mitosis. [O2]

• Low and standard demand students should read the first section from the Student Book or use the

PowerPoint to discuss how cells divide by mitosis. Students should complete task 1 and 2 from Worksheet 2.8.1. [O2]

• Check students’ ideas using the PowerPoint slide. [O2] • High demand students should read the section on cell division from the student book. Students should answer the questions on Worksheet 2.8.2. [O2]

• Show high demand students the PowerPoint and discuss the importance of meristems in plant cloning. OCR GCSE Biology: Teacher Pack

See answers to Question 2 on Worksheet 2.8.1 above. Plant versus animal cloning Similarities Identical daughter cells produced Daughter cells have same number of chromosomes as parent Stem cells are used

Differences Nuclei of meristem cells do not have to be removed No electrical shock is needed No ethical considerations with the use of meristems Only cells from one organism are involved

OCR GCSE Biology: Teacher Pack

Chapter 3: Organism level systems

Lesson 8: The endocrine system

Consolidate and apply • Ask students to complete section 3 of their worksheet, where they match the scenarios given to the

Lesson overview

hormones that are most likely to be involved. [O1, O2]

• Students should work in small groups. They should use one of the scenarios and produce a poster to

OCR specification reference

explain how the signals are picked up, and how the pituitary gland controls the release of the perspective hormone. They should explain what impact the hormone has on the body. [O1, O2, O3]

OCR B3.2a

Learning objectives • Recall that the endocrine system is made up of glands that secrete hormones into the blood. • Know the location of the major endocrine glands. • Understand why the pituitary gland is the ‘master gland’. Learning outcomes • Describe the endocrine system. [O1] • Explain the function of the major endocrine glands and their hormones. [O2] • Explain how the endocrine system works to bring about changes to the body. [O3] Skills development • WS 1.3e Interpret observations and other data. • WS 1.3i Communicate the scientific rationale for investigations, methods used, findings and reasoned conclusions.

• WS 1.4a Use scientific vocabulary, terminology and definitions.

Extend Ask students able to progress further to:

• find out more about the role of human growth hormone and how it is used today. They could discover why people with large amounts of growth hormone do not live very long. [O1, O2]

Plenary suggestions • Play ‘What am I?’ Think of a part of the endocrine system, without telling the students. Ask them to think of ‘yes or no’ questions. Students must guess the part with the fewest number of questions.

• Students write their own ‘true or false’ statements about the endocrine system, and test the class. [O1, O2]

Answers to Worksheets 3.8.1 and 3.8.2 1 Roles of the endocrine glands and their hormones Name of gland

Name of hormone(s) produced

pituitary

growth hormone, prolactin, TSH, ACTH, ADH, oxytocin

Resources needed Video of endocrine glands from Medline Plus at www.nlm.nih.gov; poster paper; Internet access. Worksheet 3.8.1 (low and standard demand); Worksheet 3.8.2 (high demand)

thyroid

thyroxine

Key vocabulary endocrine gland, endocrine system, hormone

pancreas

insulin, glucagon

adrenal

adrenaline, corticosteroids,

ovary

oestrogen, progesterone

testes

testosterone

Teaching and learning Engage • Show students the image of Robert Wadlow on page 124 of the Student Book. Discuss why he grew so tall

and died so young. Introduce the idea that hormones are chemicals produced by different organs that have a profound effect on our body. Ask students to list any hormones they have heard of and what their roles might be. [O1]

Challenge and develop • Show students the video about endocrine glands from www.nlm.nih.gov, which introduces the endocrine

system and its control. Discuss how the pituitary gland acts as the ‘master gland’. Ask students to think of an analogy to compare the role of the pituitary with the other endocrine glands. [O1, O2]

• Ask students to work in small groups and use the Internet to research the main endocrine glands, their

hormones and the effects on the body. Students should complete section 1 of Worksheet 3.8. [O1, O2]

• Ask students to use the information they have collected and produce a PowerPoint presentation on the

endocrine system. They should explain the role of the main endocrine organs: pituitary, thyroid, adrenal gland, pancreas, ovary and testes. [O1, O2, O3]

Explain • Ask students to annotate the diagram of the endocrine system in section 2 of Worksheet 3.8.1 and explain the roles of all the main hormones, and how this is brought about.

• High demand students (Worksheet 3.8.2) should compare the length of time each hormone is likely to act over, and rank each hormone according to how much it affects the body. [O1, O2, O3]

OCR GCSE Biology: Teacher Pack

107

Name of hormone

Effects on the body

growth hormone

stimulates growth of cells and tissues

ADH

regulates water balance in the body

thyroxine

regulates the rate of metabolism

insulin

reduces the levels of glucose in the blood

glucagon

increases the levels of glucose in the blood

adrenaline

increases heart rate, breathing rate, affects the release of insulin and glucagon, prepares the body for emergency action

oestrogen and progesterone

control the menstrual cycle, pregnancy, puberty and secondary female characteristics

testosterone

controls puberty and secondary male characteristics

2 Where are the endocrine glands? Diagram annotated as per Figure 3.20 in the Student Book. High demand: hormones likely to have a very long-term effect – oestrogen, progesterone, testosterone, growth hormone; hormones likely to have a more immediate effect (days or weeks) – insulin, glucagon, thyroxine, ADH; hormones likely to have a very quick response – adrenaline; most profound effects on the body – oestrogen, progesterone, testosterone, growth hormone; weaker effects – adrenaline, insulin, glucoagon, thyroxine 3 When do hormones act? 1. insulin, glucagon, thyroxine, pituitary 2. thyroxine, insulin, glucagon, pituitary 3. oestrogen, progesterone, testosterone 4. adrenaline, thyroxine, pituitary, insulin, glucagon 5. pituitary, thryoxine, insulin, and glucagon 6. adrenaline, pituitary, thyroxine, insulin, glucagon OCR GCSE Biology: Teacher Pack

108

Chapter 5: Genes, inheritance and selection

Check your progress

reproduce by asexual and sexual reproduction

■ identify meiosis as the cell division used to produce gametes

■ identify a mutation as a change in the DNA

➞

➞ ➞ ➞

■ recall that genes exist in

different forms called alleles, and know key genetic terms

■ distinguish between variation caused by genes and by the environment

➞ ➞ ➞

➞

■ identify the causes of extinction

O CR G CSE B iology: TTeacher eacher PPack ack OCR GCSE Biology:

in producing gametes

■ describe how mutations can,

on rare occasions, affect how an organism functions

➞ ➞

to show the inheritance of characteristics controlled by single genes

■ describe how variation

contributes to an organism’s survival selection leads to a struggle for existence

to the development of the theory of evolution by Darwin and Wallace

➞

genetics and evolution were not linked until the twentieth century

➞ ➞

■ describe how new species, predators and competitors can lead to extinction

1225 79

■ explain that the method of

The family tree shows that there is a history of PKU in the mother’s (8) family. The father (7) was unaware of the condition in his family.

■ explain that the gametes

The couple would like another child. A genetic counsellor draws a family tree.

reproduction may depend on circumstances produced by meiosis are genetically unique

Family A 1

■ explain how mutations can

➞

Family B

to predict the outcome of genetic crosses

female

The student has

known carriers

➞

of genetic variation

change operating with natural selection leads to the evolution of a new species

a What is the genotype of the father (7)?

Pp b What can be deduced about the genotype of the father’s parents, 1 and 2? Explain your answer.

occurrence of evolution and natural selection

work of many scientists contributed to the gene theory

The genetic counsellor talks about the father’s family’s medical history.

One is a carrier. c Draw a genetic diagram to show how 12 came to have PKU.

Mother ( P p)

➞

examination, fossils and biochemistry have led to modern evolutionary trees

■ evaluate circumstances that may lead to another mass extinction

gametes

■ explain how microscopic

➞

■ understand the mechanism

■ explain how the scientific

genotype correctly.

child with phenylketonuria

■ explain the evidence for the

➞

male

affect protein synthesis and structure

■ explain how environmental

■ explain the features used to develop evolutionary trees

A couple’s second child was born with a condition called phenylketonuria (PKU). The condition is caused by a recessive allele.

by coding for the production of a particular protein, and non-coding genes switch genes on and off

■ construct Punnett squares

■ identify the reasons why

■ recall and use the

classification system developed by Linnaeus

■ explain the need for meiosis

➞

■ describe the evidence that led

■ identify reasons why

evolution was not, to begin with, accepted

disadvantages of each type

➞

■ describe how natural

■ recall that the theory of

evolution was developed independently by Darwin and Wallace

■ describe advantages and

■ understand that genes work

■ complete Punnett squares

■ recall early ideas about evolution

of DNA that controls a particular characteristic

PP unaffected

Pp unaffected (a carrier)

pp has PKU

gametes

■ identify that organisms

■ describe a gene as a section

Male ( P p)

■ recall the definition of the

genome <MB_DYK_H>

Worked example

OCR GCSE Biology: Teacher Pack OCR GCSE Biology: Teacher Pack

The combination of alleles that produced 12

226

The answer would have been better with more explanation. One parent (or both) must be carriers. For 7 to be a carrier, he must have inherited one recessive allele. So, one parent must have passed on a recessive allele. The other parent would have passed on a dominant allele (otherwise 7 would have PKU). Their other allele could have been the recessive allele, which was not passed down to any of the three children. This a very good answer. The student has included the parental genotypes, the gametes produced, the possible genotypes and phenotypes produced, and has highlighted the combination of alleles that must have produced 12.

Chapter 6: Global challenges

Lesson 25: Looking at plant diseases

Explain • Students should complete the table on Worksheet 6.25.1 (low demand), Worksheet 6.25.2 (standard

Lesson overview

demand) or Worksheet 6.25.3 (high demand). Low demand students have been given a help sheet, which contains the information needed to complete the table. [O1, O2]

OCR specification reference

• Discuss with high demand students the different ways plant diseases can be detected; they will already be

OCR B6.3e; OCR B6.3f; OCR B6.3i

familiar with some of these from the discussions about the different diseases. [O2]

Learning objectives • Recall the causes and symptoms of plant diseases. • Describe how some plant diseases are spread and controlled. • Describe how some plant diseases can be detected and identified, both in the lab and in the field.

• Explain to high demand students how diseases are identified. Students should then use the Internet to

identify some different diseases listed on Worksheet 6.25.3. The information is sourced from www.planetnatural.com (go to ‘Learning centre’, then ‘Plant diseases’) and could be printed if the Internet is not available. [O2, O3]

Consolidate and apply

Learning outcomes • Recall the causes of plant diseases as bacteria, viruses, fungus and insects. [O1] • Describe the symptoms of infection by pathogens and damage by ion deficiency. [O2] • Understand how plant disease can be identified using monoclonal antibodies. [O3] Skills development

• Low and standard demand students research one of the plant diseases mentioned and produce a poster (see Worksheet 6.25.1 or Worksheet 6.25.2). If there is no Internet they can use the information in the Student Book. [O1, O2]

• High demand students should produce a fact sheet for inexperienced gardeners about plant diseases. The

fact sheet should include indicators to look out for and advice on how to get the diseases identified. [O2, O3]

• WS 1.1e Explain everyday and technological applications of science. • WS 1.4a Use scientific vocabulary, terminology and definitions. • WS 2d Communicating the scientific rationale for investigations, methods used, findings and reasoned conclusions.

Resources needed Image of plant with rose black spot; image of a plant with tobacco mosaic virus; video of aphids feeding; poster material; access to Internet. Worksheet 6.25.1 (low demand); Worksheet 6.25.2 (standard demand); Worksheet 6.25.3 (high demand) Key vocabulary barley powdery mildew, crown gall disease, TMV

Extend Ask students able to progress further to:

• discuss why using chemical insecticides to kill aphids may not be the best solution. [O3] Plenary suggestions • Read out the statements on the Technician’s notes – some are true and others are false. Ask the students to identify if they are true or false – this can be done with thumbs up or thumbs down.

• Once a false statement is identified, can they change it to make it true?

Teaching and learning

Answers to Worksheets 6.25.1, 6.25.2 and 6.25.3

Engage

Sample answers for table

• Show students an image of a plant with rose black spot. [O1] • Ask students to write down what is wrong with the plant, what might have caused it and why it is a problem

for the plant. This can be done in small groups using mini-whiteboards and should be revision from the lesson on fungal diseases. [O1]

Plant disease or deficiency tobacco mosaic virus

• Each group reports back to the class to build up a picture of what they remember about fungal plant diseases. [O1]

Challenge and develop • Use the introduction to discuss causes of disease in plants; explain that as well as bacteria, fungi and

aphid infection

viruses, insects will also damage plants. [O1]

• Show students an image of a plant with tobacco mosaic virus. Ask them to describe the symptoms and suggest why it will affect the rate of photosynthesis. [O1, O2]

• Ask students to recall what they remember about mineral deficiency in plants. Remind them of the symptoms

Cause

Treatment or control

mottling or discoloured leaves

infection by a virus

use insecticide to kill insects

curled leaves

that spread the disease.

stunted growth

destroy any infected plants

yellow streaks or spots on leaves

clean infected tools

decreased growth rate

aphids feeding on the

insecticides or removing the

mottled or yellow leaves

sap

aphids by hand or using

wilting

• Show students a video of aphids feeding. Ask the students to suggest what they are feeding on and what damage that will do to the plant, including the spread of diseases. [O2]

Symptoms

natural predators

low yields nitrate deficiency

stunted growth

not enough nitrates in

add minerals to soil

soil magnesium deficiency

chlorosis (yellow leaves)

not enough

add minerals to soil

magnesium in soil

of nitrate deficiency and introduce the term ‘chlorosis’, caused by magnesium deficiency. [O1, O2]

Identifying plant diseases 1. brown rot, 2. apple scab, 3. club root, 4. blossom end rot

OCR GCSE Biology: Teacher Pack

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OCR GCSE Biology: Teacher Pack

280

Chapter 6: Global challenges

When and how to use these pages: Check your progress, Worked example and End of chapter test

Percentage Total marks

Check your progress

Q. 19 (A02) 4 marks

Check your progress is a summary of what students should know and be able to do when they have completed the chapter. Check your progress is organised in three columns to show how ideas and skills progress in sophistication. Students aiming for top grades need to have mastered all the skills and ideas articulated in the final column (shaded pink in the Student book).

Q. 18 (A02) 2 marks Most demanding [Higher Tier] More Challenging [Higher Tier]

Q. 12 (A03) 4 marks Q. 11 (A02) 2 marks

Worked example

Q. 10 (A01) 2 marks Going Further [Foundation and Higher Tiers]

Q. 7 (A02) 2 marks

End of chapter test

Q. 6 (A01) 1 mark

The End of chapter test gives students the opportunity to practice answering the different types of questions that they will encounter in their final exams. You can use the Marking grid provided in this Teacher Pack or on the CD Rom to analyse results. This shows the Assessment Objective for each question, so you can review trends and see individual student and class performance in answering questions for the different Assessment Objectives and to highlight areas for improvement.

OCR GCSE Biology: Teacher Pack

Student Name

Getting Started [Foundation Tier]

Q. 1 (A01) 1 mark

315

Q. 2 (A01) 1 mark

OCR GCSE Biology: Teacher Pack

Q. 3 (A01) 1 mark

Questions could be used as a test once you have completed the chapter Questions could be worked through as part of a revision lesson Ask Students to mark each other’s work and then talk through the mark scheme provided As a class, make a list of questions that most students did not get right. Work through these as a class.

Marking Grid for End of Chapter 6 Test

Q. 4 (A02) 2 marks

•

Q. 5 (A01) 2 mark

• • •

Q. 8 (A01) 1 mark

Give students the Worked example worksheet (Teacher Pack CD). The annotation boxes on this are blank. Ask students to discuss and write their own improvements before reviewing the annotated Worked example in the Student Book. This can be done as an individual, group or class activity.

Q. 9 (A01) 1 mark

The worked example talks students through a series of exam-style questions. Sample student answers are provided, which are annotated to show how they could be improved. •

Q. 13 (A02) 1 mark

•

Ask students to construct a mind map linking the points in Check your progress Work through Check your progress as a class and note the points that need further discussion Ask the students to tick the boxes on the Check your progress worksheet (Teacher Pack CD). Any points they have not been confident to tick they should revisit in the Student Book. Ask students to do further research on the different points listed in Check your progress Students work in pairs and ask each other what points they think they can do and why they think they can do those, and not others

Q. 14 (A02) 1 mark

•

Q. 15 (A02) 4 marks

•

Q. 16 (A03) 2 marks

• •

Q. 17 (A02) 2 marks

Check your progress can be used for individual or class revision using any combination of the suggestions below:

316