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OCR 21st Century Science: B2 Keeping healthy

COLLINS NEW GCSE SCIENCE © HarperCollinsPublishers Ltd 2011

B2 Module Introduction

Pages 38−39 in the Student Book provide an introduction to this module.

When and how to use these pages

These pages summarise what students should already know from KS3 or from previous GCSE units and provide

an overview of the content that they will learn in this module.

o Use these pages as a revision lesson before you start the first new topic. o Brainstorm everything that students remember about the different topics using the headings as a starting point. Compare your list with the points on page 38. o Use the questions on page 38 as a starting point for class discussions. o Ask students if they can tell you anything about the topics on the right-hand page. o Make a note of any unfamiliar / difficult terms and return to these in the relevant lessons.

Suitable answers to the questions on page 38 are:

o To prevent loss of blood and to minimise the chance of pathogens entering the body through the wound. o The nervous system and the skeletal system. o Mammals, such as a horse, dog or mouse, and birds.

You could revisit these pages at the following points:

o before lesson b2_07 on the heart, pages 54−55 o before lesson b2_11 on homeostasis, pages 62−63.

Overview of module

This module helps to develop students’ understanding of how to keep healthy. It covers maintaining a healthy lifestyle, avoiding infection and taking medicines when they are required.

Students will learn about the microbes that inhabit their bodies and how their immune systems cope with

pathogens. Students will begin to understand how their lifestyle choices influence their health, particularly in the

context of heart disease. They will learn how new drugs (medicines) and vaccines are developed, including how

drugs and vaccines are tested for safety.

Obstacles to learning

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

Microbes

Students may be surprised how many bacteria there are living in and on their bodies. It is important that they

distinguish between these harmless bacteria and those that are pathogenic and cause disease.

Antibodies and antigens

Students find ideas about antibodies and antigens difficult. Use every opportunity to reinforce that pathogens have

proteins on their cell membranes that can be recognised by the body, and that these are called antigens. Students

often think that all antigens are the same, but this is not the case. Each type of pathogen has a unique antigen.

Students need to understand the antibody−antigen relationship in order to be able to explain how memory cells create vast numbers of specific antibodies in response to a threat from a pathogen the body has previously

encountered.

Risk

People may perceive some risks to be much higher than they actually are, for example where medical treatments

such as vaccinations are concerned. Conversely, students may consider the risks of non-prescription drugs such

as nicotine or alcohol to be much lower, or the risks of activities they enjoy, such as horse riding or mini-moto

riding, to be lower than they actually are. Some students may have preconceived views about vaccination and the

risks involved, perhaps due to a family view on the subject. Help students to differentiate between ‘real’ risk based on scientific evidence and ‘perceived’ risk based on gut feeling.

Correlation

Students find correlation difficult. A correlation between two factors may be present, but this does not necessarily

mean that one of those factors was caused by the other. A good example is the sales of ice cream being correlated

with the sales of swimwear. Neither of these is caused by the other, even though a correlation is present. Have in

mind other examples where there is correlation but one factor does not cause the other. For example, young males

have a disproportionate number of cycling accidents. This is because most cyclists are young males, and does not

B2 Module Introduction continued


mean that young males are worse cyclists. Check students’ understanding by asking them to give other examples

of correlation.

Clinical trials

Students may have heard news reports highlighting the problems or dangers of clinical trials. It is important to

balance this prior knowledge with information about the numbers of clinical trials (there are many thousands going

on all the time) and that most of these trials take place with no serious incident.

The heart and circulation

Students are easily confused about the convention of labelling the heart. A solution to this is to look at the heart

inside a model (for example a plastic model that can be dismantled) and then students can see which side of the

person’s heart is the ‘right’ and which is the ‘left’. Students need to remember that waste products are taken away in the blood as well as nutrients and oxygen being

delivered to active cells. Students often forget to include this in their answers to questions about why heart rate

increases with exercise.

Epidemiological studies

Students need to understand that large-scale epidemiological studies are not the same as clinical trials. Large-

scale epidemiological studies look at very large groups of individuals and consider which factors lead to disease.

Clinical trials use a smaller group of individuals and test a drug (medicine) or treatment. Often the participants in a

clinical trial are volunteers who are paid to take a drug (medicine) that they do not need. Large-scale

epidemiological studies generally record what happens to individuals who have not received any interventions.

Homeostasis

It is important for Higher tier students to remember that a description of a negative feedback loop must include an

explanation of what happens when the body gets back to normal and the effector is directed to stop.

It is necessary that students understand the ways that humans gain and lose water. The process of respiration

uses glucose and oxygen and produces energy, carbon dioxide and water. This water is produced in the muscles,

and students need to realise that it is dealt with the same way all water in the body is dealt with, by the kidneys.

Students find it difficult to recall the way in which alcohol or Ecstasy affects the kidneys. A helpful way for students

to remember this is that a hangover suffered after excessive alcohol is caused by dehydration, and work back from

there. They may be able to remember this as many hangover cures involve drinking soft drinks, which work

because they rehydrate the body.

Practicals in this module

In this module students will do the following practical work:

o Modelling the spread of infection o Modelling the ‘lock and key’ antibody−antigen relationship o Preparing a TV/radio advert about the importance of vaccination o Role-play discussion of ethical considerations that compulsory vaccination might raise o Investigating the effects of antibiotics on bacteria o Heart dissection o Taking the pulse o Measuring blood pressure o Kidney dissection o Investigating the effect on onion cells in solutions of different concentration

Key vocabulary covered in this module

microorganism pathogen toxin binary fission

immune system white blood cell antibody antigen memory cell immune

antigen memory cell vaccine vaccination

risk side effect antimicrobial antibiotic resistance

antimicrobial antibiotic resistance superbug correlation mutation

clinical trial control group placebo

heart circulatory system deoxygenated oxygenated artery vein capillary coronary artery

coronary heart disease saturated fat correlation cholesterol

heart rate pulse rate resting heart rate blood pressure high blood pressure low blood pressure

blood pressure high blood pressure epidemiological study

homeostasis receptor processing centre effector negative feedback vasodilate

blood plasma kidneys urea excretion

antidiuretic hormone (ADH)



B2 Module Checklist

Pages 68−69 in the Student Book provide a student-friendly checklist for revision.


This checklist is presented in three columns showing progression, based on the grading criteria. Bold italic means

Higher tier only.

Remind students that they need to be able to use these ideas in various ways, such as:

o interpreting pictures, diagrams and graphs

o applying ideas to new situations

o explaining ethical implications

o suggesting some benefits and risks to society

o drawing conclusions from evidence they have been given.

These pages can be used for individual or class revision using any combination of the suggestions below.

o Ask students to construct a mind map linking the points on this checklist.

o Work through the checklist as a class and note the points that need further class discussion.

o Ask students to tick the boxes on the checklist worksheet (on the Teacher Pack CD) if they feel confident that they are well prepared for the topics. Students should refer back to the relevant Student Book pages to revise the points that they feel less confident about.

o Ask students to use the search terms at the foot of the relevant Student Book pages to do further research on the different points in the checklist.

o Students could work in pairs, and ask each other what points they think they can do, and why they think that they can do those, and not others.

B2 Module Checklist continued


Module summary

In the introduction to this module, students were presented with a number of new ideas. Work through the list

below as part of their revision. Ask students to write their own summaries and mind maps, using this list as a

starting point.

The immune system, vaccines and antibiotics

o when pathogens get inside the body, the body’s immune system works to defend the body against infection

o vaccinations cause the immune system to produce memory cells that help it to defend against a particular pathogen at a later date

o antimicrobials such as antibiotics destroy certain microorganisms, but the microorganisms can become resistant to these

Clinical trials

o drugs and vaccines are tested for effectiveness and safety in clinical trials

o human trials may be carried out on healthy volunteers and on patients with a condition

o there are ethical issues to consider in human trials

The heart and circulatory system

o the heart functions as a double pump

o there is a correlation between lifestyle factors and heart disease

o there are measures that can be taken by an individual to reduce the risk of heart disease

o measurements of heart rate and blood pressure are indications of heart health

Homeostasis

o homeostasis is the maintenance of a constant internal environment in the body

o automatic controls systems keep several factors, including water level, at a steady level

o the kidneys’ function is to balance water levels, by producing dilute or concentrated urine

o intake of alcohol or use of Ecstasy interfere with this control system



Checklist B2 Aiming for A

Use these checklists to see what you can do now. Refer back to the relevant topic in your Student Book if you are not sure. Look across the rows to see how you could progress – bold italic means Higher Tier only.

Remember that you will need to be able to use these ideas in various ways, such as:

interpreting pictures, diagrams and graphs

applying ideas to new situations

explaining ethical implications

suggesting some benefits and risks to society

drawing conclusions from evidence that you are given.

Working towards an A grade

Aiming for Grade C Aiming for Grade A

explain how our immune system, including white blood cells, defends us against disease

understand what vaccinations are and that they work by triggering an immune response to a dead or inactive disease

explain how antibodies protect us from pathogens and how they recognise and respond to organisms that have been encountered before, using memory cells;

understand what vaccines are and how they are tested

understand why, to prevent epidemics of infectious diseases, it is necessary to vaccinate a high percentage of a population

understand the ways to reduce resistance to antimicrobials and antibiotics

understand that random changes (mutations) in the genes of microorganisms sometimes lead to varieties which are less affected by antimicrobials

recall that human trials may be carried out on groups of healthy volunteers to test the safety of a drug and also on people with illness to see how effective the drug is;

understand the ethical issues related to using placebos in human trials

describe and explain the different types of drug trial, including ‘open-label’, ‘blind’ and ‘double-blind’ human trials, in the testing of a new medical treatment;

understand the importance of long-term human trials

OCR 21st Century Science: B2 Checklist


Aiming for Grade C Aiming for Grade A

understand how the structure of arteries, veins and capillaries is related to their function, and how lifestyle factors can lead to fatty deposits in the blood vessels that supply the heart muscle leading to a heart attack

describe actions that could be taken to reduce the risk of heart disease when provided with lifestyle and genetic data

understand that there is a range of normal measurements for heart rate and blood pressure; that high blood pressure increases heart disease risk, and how large-scale studies are used to identify factors that put people at risk of heart disease

understand that the systems that maintain the body’s environment have detectors, processing centres and effectors

understand what negative feedback is and how it reverses changes to a system

understand that the kidneys are important in controlling the level of water, waste and other chemicals in the blood, and that the kidneys change the concentration of the urine according to whether the body needs to retain or lose water;

understand that alcohol and ecstasy disrupt this process and can lead to too much or not enough water being lost by the body

understand that the concentration of urine is under the control of a hormone called ADH, which is released into the bloodstream by the pituitary gland, and understand that ADH release is controlled by negative feedback



Checklist B2 Aiming for C

o achieve your forecast grade in the exam you will need Use these checklists to see what you can do. Refer back to the relevant topic in your Student Book if you are not sure.

Remember that you will need to be able to use these ideas in various ways, such as:

interpreting pictures, diagrams and graphs

applying ideas to new situations

explaining ethical implications

suggesting some benefits and risks to society

drawing conclusions from evidence that you are given.

Working towards a C grade

Aiming for Grade E Aiming for Grade C

understand that microorganisms can produce substances that harm the body

explain how our immune system, including white blood cells, defends us against disease

understand that our bodies provide ideal conditions for microorganisms to grow and multiply

explain how antibodies protect us from pathogens and also how they recognise and respond to organisms that have been encountered before, using memory cells; understand what vaccines are and how they are tested

recall that chemicals called antimicrobials can be used to kill bacteria, fungi and viruses, and understand that over time bacteria and fungi may become resistant to antimicrobials

understand the ways to reduce resistance to antimicrobials and antibiotics

recall that new drugs and vaccines are tested for safety and effectiveness using animals and human cells grown in the laboratory and then using human trials

recall that human trials may be carried out on groups of healthy volunteers to test the safety of a drug and also on people with illness to see how effective the drug is; understand the ethical issues related to using placebos in human trials

describe the role of the heart as a double pump in the circulatory system and understand why heart muscle cells need their own blood supply

understand how the structure of arteries, veins and capillaries is related to their function, and how lifestyle factors can lead to fatty deposits in the blood vessels that supply the heart muscle leading to a heart attack

OCR 21st Century Science: B2 Checklist


Aiming for Grade E Aiming for Grade C

understand what heart rate and blood pressure are and how they can be measured

understand that there is a range of normal measurements for heart rate and blood pressure; that high blood pressure increases heart disease risk, and how large-scale studies are used to identify factors that put people at risk of heart disease

understand that the body keeps the environment inside it the same whatever the external conditions, and this is called homeostasis

understand that the systems that maintain the body’s environment have detectors, processing centres and effectors

understand how the body takes in and loses water, and why it is important for the amount of water in the body to remain stable

understand that the kidneys are important in controlling the level of water, waste and other chemicals in the blood, and that the kidneys change the concentration of the urine according to whether the body needs to retain or lose water; understand that alcohol and ecstasy disrupt this process and can lead to too much or not enough water being lost by the body



B2 Applying your knowledge

Pages 48−49 in the Student Book prepare students for assessment.


This activity provides an opportunity for students to apply their science knowledge in a different context.

Ask students to:

o read through the context and tasks, listing any terms that they do not understand

o as a whole class or in small groups, discuss the tasks to ensure that all students understand the terminology

used and to clarify what is required

o answer the questions for each task.

If time allows, ask students to mark one another’s work using the mark scheme provided.

Notes

The purpose of this activity is for students to show how they can apply to a new context their understanding of

infectious diseases and how these are controlled through vaccination.

The challenge of the questions increases through the tasks. The questions may be attempted individually but the

students may get more out of the activity if they work in small groups, sharing ideas and developing joint

responses. This may help them to develop ways of approaching more challenging questions.

Answers

Task 1

Polio is a virus and travels through the body by entering the bloodstream.

Polio is a serious illness that can leave its victims permanently disabled.

Task 2

The body’s existing antibodies are not effective against polio; by the time they were able to respond the virus

would have spread too far.

Task 3

Viruses have a different form from other microorganisms; a particular virus is recognised by the antigens on its

surface.

Her body would have developed antibodies to deal with the virus and would have prevented it from spreading.

Task 4

Prior infection means that the body has had the opportunity to develop antibodies by being exposed to the virus

on a previous occasion so that it is prepared to deal with it.

Being protected against infection by a particular pathogen.

Task 5

The concept that if a large proportion of a population have been immunised against a condition, then that

condition will find it much harder to spread.

Even those members of the population who haven’t been immunised are much less likely to come in contact with a member of the population who has been infected.

B2 Applying your knowledge continued


Mark scheme

For grade E, students should show that they can:

o understand that microorganisms can produce substances that damage the body

o understand that our bodies provide ideas conditions for microorganisms to grow and multiply

For grades D, C, in addition students should show that they can:

o explain how our immune systems, including white blood cells defend us against disease

o explain how antibodies protect us from pathogens and also how they recognise and respond to organisms

that have been encountered before using memory cells

o understand what vaccines are

For grades B, A, in addition students should show that they can:

o understand what vaccinations are and that they work by triggering an immune response to a dead or

inactive disease

o explain what is meant by herd immunity and how it can protect species



B2 Exam-style questions

Pages 70−71 in the Student Book are exam-style questions.


These questions are based on the whole of Module B2 and cover a range of different types of questions that

students will meet in their written exams.

o The questions could be used as a revision test once you’ve completed the module. o Work through the questions as a class as part of a revision lesson. o Ask students to mark each other’s work, using the mark scheme provided. o As a class, make a list of the questions that most students did not get right. Work through these as a class.

Notes on the worked examples

The first question asks the students to apply what they know about lifestyle choices and heart disease to a

particular individual. Part b of the question has 6 marks available and the quality of written communication is

assessed. In this type of question students should structure their answer and be particularly careful that the spelling

and grammar are accurate. It is worth students becoming familiar with the ‘banded’ type of mark scheme by which

these questions are graded; for 6 marks it is not enough to include six relevant bullet points – the answer must be

correct, but also well organised and well expressed.

Assessment Objectives

These exam-style questions cover the Assessment Objectives as described below.

Assessment Objectives Questions

AO1 Recall, select and communicate their knowledge and understanding of science

1, 2c, 4a

worked examples 1a, b, 2

AO2 Apply skills, knowledge and understanding of science in practical and other contexts

2a, 3a, 4b, 5a, b

worked example 1c

AO3 Analyse and evaluate evidence, make reasoned judgements and draw conclusions based on evidence

2b, 3b, 5c

Answers

These answers are also supplied on the Teacher Pack CD, so students can mark their own or their peer’s work.

Question

number

Answer Additional notes Mark

1 Artery:

oxygenated (except pulmonary artery);

thick elastic wall to withstand pressure of pumping heart

Vein:

deoxygenated (except pulmonary vein);

thin wall because pressure is low, valves to prevent the

backflow of blood

Capillary; single cell thick to allow maximum diffusion of

oxygen, carbon dioxide and other substances

Students may need a review

of the structure of the heart

and the double-pump system

if they make errors in

answering this question. In

particular, the exceptions to

the oxygenated blood

/deoxygenated blood pattern

may be missed if

understanding is poor.

2

2

2

2a Even without prior use, 10% of bacteria are already resistant

to antibiotic 1.

With use of any prior antibiotic, the resistance goes up to

about 17%.

If an antibiotic of the same type has been used before, the

resistance rises to about 21%.

1

1

1

b Antibiotic 2 1

B2 Exam-style questions continued


Perhaps this antibiotic is extremely powerful and so

extremely difficult to develop resistance to / perhaps the way

it works to kill bacteria means that virtually none survive.

1 mark for any reasonable

explanation

1

c Patients should be encouraged to finish the course of

antibiotics so that as many as possible are destroyed.

Perhaps industry could be encouraged to use fewer

antibiotics, for example in intensive farming.

Antibiotics should only be prescribed when they are really

needed .

1

1

1

3a (i)

(ii)

As exercise begins, the heart rate of the fit person rises less

quickly (at a slower rate) than the unfit person, because the

heart is more efficient and able to pump more blood per beat

than the unfit person. The unfit person’s heart rate rises very steeply.

After exercise, the fit person’s heart rate goes back to

normal more quickly than the unfit person’s. The unfit person takes longer to get rid of the waste products from the

blood (e.g. carbon dioxide) than the fit person.

Students need to be clear

about the term ‘rate’, and

how they can tell if the rate is

fast or slow by looking at the

gradient of the graph.

2

2

b Fitness enables the heart to deal more effectively with the

increased demand for oxygen caused by exercise. Fitness

enables the body to rid itself of waste products more quickly

after exercise, returning to its pre-exercise state more

quickly.

2

4a Hypothermia is the term for when the body temperature

drops below 35 °C and the body cannot control its own

temperature. It is dangerous because it can cause death.

2

b (i)

(ii)

In the cold sea, Jake’s temperature would have begun to drop. This was detected by receptors. These sent a

message to the processing centre (the brain) which then co-

ordinated the response, which was a message sent to the

effectors (the blood vessels, to vasoconstrict to conserve

heat, and the muscles, to shiver to generate heat.)

Once Jake was out of the water in the sunshine, the

receptors detected that he was beginning to warm up, and

once 37 °C was reached, the processing centre sent the

message to the effectors to stop. This led to him going back

to a pink colour, as the blood vessels returned to their

normal width, and the shivering stopped.

The correct use of scientific

terms is important here.

5

4

5a Better practices in hospitals and a reduction in child poverty

could have brought about the reduction in deaths.

2

b The vaccinations have reduced the numbers of people

suffering from measles, and also brought about a reduction

in the rate of spread. This has reduced the death rate.

2

c Some people are choosing not to have their children

vaccinated, possibly because they are no longer familiar

with the problems that measles can cause since, as seen in

the graph, very few cases now occur. Also, scare stories

circulated on the internet may cause people to erroneously

believe that it is safer for their children not to have the

vaccine.

2



b2_01 Microbes and your body

1 What causes disease?

Diseases are caused by pathogens. Most diseases that humans suffer from are caused by bacteria or viruses. You may ask friends, your teacher or use an internet search engine to find out more about pathogens for the following activity. 1 Write a list of all the diseases you can think of.

2 Sort your list of diseases into those caused by bacteria and those caused by viruses. Use the table below. In the third column put those diseases you’re not sure about.

Diseases caused by bacteria

Diseases caused by viruses

Not sure – find out

3 Share your table with someone else in the class and see if you can find out from their

table about the ones in your ‘Not sure’ column.

4 Choose one disease caused by a virus and one caused by bacteria and find out more about each. What are the symptoms of the disease? Is there a treatment, and if so, what is it?

Virus disease: ………………………………………………………………………......................

…………………………………………………………………………………………………………

…………………………………………………………………………………………………...........

…………………………………………………………………………………………………...........

Bacteria disease: …………………………………………………………………………………...

…………………………………………………………………………………………………...........

…………………………………………………………………………………………………………

…………………………………………………………………………………………………...........

b2_01 Microbes and your body continued


2 How microorganisms can harm our bodies

Carry out the practical activity as directed by your teacher. 1 How many of the group became ‘infected’ in the five minutes?

2 Get into groups of three. Your experiment used a ‘model’ for the spread of infection. Discuss the following, and then share your conclusions with the rest of the class.

If the infection was a cough or cold, was this a good model?

In what ways could your model be improved? 3 Individually, write an email to the head teacher advising what precautions should be

taken in your school to reduce the spread of infections, such as colds and flu.

3 Reproduction of microorganisms

Get into small groups. Look at the graph and then answer the questions.

1 Describe the shape of the graph. 2 Explain what is happening to the bacteria during the ‘stationary phase’ (the ‘flat’ part of the curve). 3 Why do the numbers of bacteria decrease significantly at the right-hand side of the

graph?



b2_02 Defending against disease

1 How our bodies fight disease

Draw round someone in your class on to a large piece of paper, or draw a body outline on a piece of A4 paper.

Use the labels below to show how the body defends itself against disease by adding them to your outline in the correct places. Add more labels if you can think of more ways that our bodies fight disease.

Saliva in mouth has mild antibiotic properties

Nose hairs

Cilia in windpipe

Strong acid in stomach

Blood has ability to clot

Waterproof skin

Saline tears have mild antibiotic properties

2 Response to antigens

You teacher will give you scissors, pipe cleaners, Plasticine and/or card. Make a model of the relationship between an antibody and an antigen. Remember that each type of pathogen has an antigen that is unique to that type of pathogen. This means that the immune system can create an antibody that ‘fits’ exactly on to the shape of the antigen and can ‘lock on’ to it. Choose a simple shape for the antigen on the surface of the pathogen and make a model of it with card and/or Plasticine. Then make a model of the antibody that fits this antigen. When something fits together like this, biologists call it ‘complementary’. As a pair, share your model with another pair. Give the other pair constructive feedback on their model, and receive feedback on yours. Are the models good representations?

3 Recognising antigens

You are going to use the analogy of a battle to explain the immune response to pathogens. First, summarise the immune response in about six steps. Then, draw a blank ‘storyboard’ with six squares on a piece of A4 paper. Consider how you will represent the invading pathogen or pathogens and their antigens, white blood cells, memory cells and antibodies using the analogy of a battle. For each step of the immune response, write a battle heading for your storyboard. For example, for the first square you might write the heading ‘Despite external defences, pathogen enters body’. This could be represented as the ‘enemy’ (pathogen) breaking through the castle wall (skin) to get into the castle (body).



b2_03 Vaccination

Resources

Student Book pages 44−45 Interactive Book: iCould career video ‘How vaccinations work’ Interactive Book: Quick starter ‘Vaccination’ Homework pack b2_03

Files on Teacher Pack CD: b2_03_worksheet

Method of recording and re-playing students’ scripts; scissors

Learning outcomes B2.2.1 understand that vaccinations provide protection from microorganisms by establishing memory cells that

produce antibodies quickly on reinfection

B2.2.2 understand that a vaccine usually contains a safe form of a disease-causing microorganism

B2.2.3 understand why, to prevent epidemics of infectious diseases, it is necessary to vaccinate a high

percentage of a population

Ideas about Science IaS 4.1 scientists report their claims to other scientists through conferences and journals. Scientific claims are

only accepted once they have been evaluated critically by other scientists

Numeracy focus: Extracting information from charts, graphs and tables, including data from epidemiological

studies.

ICT focus: Showing a video clip to illustrate the smallpox vaccination programme; showing an animation of the

immune response.

In this lesson students are learning to:

describe how vaccinations keep us healthy

explain why it is important for society that children are vaccinated

Key vocabulary

antigen memory cell vaccine vaccination


Many students have difficulties in grasping the antibody−antigen relationship. They need to understand this in order

to be able to explain how memory cells create vast numbers of specific antibodies in response to a threat from a

pathogen that the body has previously encountered.

Stimuli and starter suggestions

Ask students to form a continuum line in response to the statement ‘I understand how vaccination works’. A

continuum line has ‘strongly agree’ at one end and ‘strongly disagree’ at the other. Ask some of the students for their explanation of how vaccination works. It will be useful to know where the students stand to be able to pitch

the lesson correctly.

Learning activities worksheet b2_03 Low demand Begin by showing students an animation of the immune response. You can find a suitable one

using a search engine. Ask students to draw a cartoon-strip with four or five squares to show what happens when a

pathogen invades the body and is ‘recognised’ as one that has been encountered before. Activity 1 on the

worksheet gives guidance.

Teaching and learning notes: Ask students to write captions for each cartoon square before they begin drawing.

Students need to do the organising and thinking part of the activity before they start to draw. In this way if they take

too long on their drawings their understanding of the process can still be checked. This is a useful review activity

and by breaking the immune response into stages students’ understanding is increased and the activity may reveal misconceptions or gaps in their knowledge.

Standard demand To begin this part of the lesson, show a video clip showing the smallpox vaccination

programme. Use a search engine to find a suitable video. Ask students to comment on why the smallpox

vaccination programme was so successful. Ask students to prepare a TV or radio advert, explaining the importance

of measles and polio vaccination and how doctors make it as safe as possible, for an audience in an

underdeveloped country. Students need to focus on the ‘public information’ role of their advert. They need to

b2_03 Lesson continued


organise relevant information and redraft it in a format suitable for their audience. Activity 2 on the worksheet gives

guidance.

Teaching and learning notes: Ask students to write their script before they record their advert. Set recording

guidelines – for example, the presentation must be only one minute long, there must be only one ‘take’, with no

editing. These guidelines keep learning focused.

High demand ‘Herd immunity’ refers to the fact that if a high proportion of a population is vaccinated against a

disease, that disease is very unlikely to spread through the small proportion of the population who are not immune;

thus an epidemic is unlikely. It has been suggested that in order to ensure ‘herd immunity’, children should not be allowed to start school at the age of five if they have not completed their course of childhood vaccinations. Ask

students to carry out in pairs a role-play discussion of the ethical questions involved in whether or not it should be

compulsory for children to have completed their vaccinations before they start school at the age of five. Cards are

provided in activity 3 on the worksheet.

Plenary suggestions Ask students to pick out five key words that summarise what they know about the immune system and vaccination.

For each key word they should provide a definition. Ask a number of students for their key word and definition as

students leave the lesson.

Student Book answers Q1 It produces very large numbers of antibodies that are specific to an antigen on the surface of a pathogen that

has invaded the body before. In this way the memory cells enable the body to mount a very quick response to

the ‘known’ pathogen.

Q2 They introduce a small amount of inactive pathogen into the body so that the body can create antibodies to it.

Memory cells remember the pathogen so that many antibodies can be produced rapidly if the pathogen is

encountered again.

Q3 A baby’s immune system has not fully developed and the vaccinations protect him or her from childhood

diseases.

Q4 So that the person who is vaccinated does not become ill.

Q5 Any reasonable answer: adverse reactions to vaccinations; safety of vaccination compared to mortality of the

disease; effectiveness of vaccine etc.

Q6 To include: safety and effectiveness of vaccine; particularly if not breastfed, a baby’s immune system is very immature; some diseases that vaccinations protect against can be fatal.



b2_03 Vaccination

1 How vaccination works

Vaccination takes advantage of the fact that the body has a ‘learned’ response to a pathogen it has encountered before.

Draw a cartoon-strip four or five squares in length to show what happens when the immune system recognises a pathogen it has previously encountered.

Write captions for each of the squares before you start your drawings.

Things to think about are:

What does a pathogen have on its surface?

Why is this useful to the immune system?

What does the body produce that responds to the surface of the pathogen?

What particular cells have a special role in this response?

What happens to the pathogen after it has been ‘recognised’?

What other cells are involved in the immune response?

2 Vaccination programmes

Imagine you work for an aid agency in a country where the vaccination programme is not yet complete and vaccinations are new to the area.

Your task is to write and record an advert for use on the local radio station to encourage parents to bring their children to be vaccinated against measles and polio. You need to outline the benefits of vaccination and also to put their minds at rest about the safety of the vaccination process.

Your radio advert needs to cover:

what the vaccination involves for the child

how a vaccination works to prevent disease

how we can be fairly sure that vaccination is safe.

b2_03 Vaccination continued


3 Preventing epidemics (Higher tier only)

Work in pairs. Cut out the cards below and use them to help you to discuss whether or not it should be compulsory for children to be vaccinated before they start school at the age of five.

One person should have the shaded cards and the other should have the white cards.

Argument for compulsory vaccination

Argument against compulsory vaccination

It is important that a high proportion of children are vaccinated to give society ‘herd immunity’

Some vaccines have side-effects and those in families with sensitivities or allergies should not be forced to risk a side-effect

Some parents do not vaccinate because they forget or are disorganised – this rule would encourage them to get their children vaccinated

Most parents still decide to vaccinate, so a few children who are not vaccinated is unlikely to cause an epidemic to start

It is not fair on the child that it risks contracting a childhood disease because of the views of its parents

Education is a basic right for children and you cannot deny it on the basis of a decision made by the child’s parents



b2_04 Making vaccination safe

1 How safe is safe?

Drugs (medicines) and vaccinations are carefully tested for safety before they are released to be prescribed by doctors for patients.

However, some people are still nervous of the risks of drugs (medicines), and even if they have been prescribed them for a serious condition they may not take them because of what they see as the risks.

Write five statements to go on a reassuring poster to be displayed in a doctor’s surgery explaining how drugs (medicines) and vaccines are tested for safety and why it is important for people to take the drugs they have been prescribed.

Your statements could include ideas about:

how drugs are thoroughly tested and monitored for safety

what patients should do if they suffer from side effects

that most treatments have a long history of safe use by patients

that a patient’s doctor will have carefully considered which medicines are most appropriate and in what doses

that it may be dangerous to a patient’s health to stop taking or change the dose of a prescribed medicine.

2 Reactions to vaccinations

Cut out the cards and then for each card, discuss:

‘Would this information make you (or other parents) more or less likely to vaccinate your (or their) child, and why?’

Over 260 million people have been vaccinated against measles. Why does the fact that such a large number of people have had the vaccination improve our confidence in its safety?

A system is in place so that any bad response to a drug or vaccination can be reported anonymously, and these claims are recorded and acted upon if necessary.

Some parents choose not to have their children vaccinated just in case there is a risk; they prefer to risk the disease, which their child might not catch, than the vaccination.

Some diseases, such as polio, have been completely eradicated from Britain because of the vaccination programme.

Many vaccinations contain albumin, a substance that is found in eggs. For this reason, some people who have an allergy to eggs are more at risk of an adverse reaction to a vaccination.

Modern society is not so familiar with childhood diseases, such as mumps and measles, because for the past 30 years most children have been vaccinated against them and so there has been ‘herd immunity’.

b2_04 Making vaccination safe continued


3 Ways of reducing resistance to antimicrobials

Antimicrobial substances, if overused, can cause resistant microorganisms to develop that are resistant to the antimicrobials.

Using information on page 47 of the Student Book and from the internet, write a short information panel for inclusion on the packaging of an antimicrobial substance to explain how it should be used to minimise the chance of resistance developing.



b2_05 Inhibiting bacterial growth

P The effect of antibiotics on bacteria

Objectives

In this activity you will:

determine which of two antibiotics is more effective against E. coli bacteria

assess the risk associated with doing the practical and take steps to control it.

Note:

Throughout this practical, aseptic technique must be practised. You will need to use ‘flaming’ to sterilise the forceps. The discs with antibiotic on them should always be handled with tweezers or forceps to avoid contamination.

Safety:

You need to work close to a lit Bunsen burner. Be especially careful that all long hair is tied back, ties are tucked away, and that you are working in a safe way, bearing in mind you are next to a flame.

When working with microorganisms it is very important to follow all the safety guidelines that your teacher gives you.

Equipment and materials

nutrient agar Petri dish inoculated with E. coli bacteria • Bunsen burner • forceps • marker pen • sticky tape • incubator set at 30 °C • discs impregnated with: penicillin (5 iu); streptomycin (25 iu) • control disc (no antibiotic)

Risk assessment

Under guidance from your teacher, carry out a risk assessment of the practical work and agree any control measures that need to be put in place to control each risk.

Method

1 Assemble your apparatus close to a Bunsen burner.

2 Light the Bunsen burner. This creates a draught that carries microorganisms in the air away so they don’t contaminate your agar plates.

3 Sterilise the forceps by holding them in the Bunsen flame for a few seconds. Carefully (without breathing on or touching the agar jelly) take the lid off the Petri dish (stay close to the Bunsen burner) and use the forceps to pick up each disc that has been impregnated with antibiotics in turn. Place the discs on the agar, with equal spacing between them. Place the control disc on the agar. Replace the lid on the agar plate. Sterilise the forceps again.

4 Use sticky tape to secure the lid of your Petri dish. Mark, using a marker pen, which disc has been placed where, your name, class and the date.

5 Your Petri dish will be incubated at 30 °C.

b2_05 Inhibiting bacterial growth continued


Results

In the next lesson, you will be able to look at the agar plates. You will see that the bacteria have not grown so well around some of the discs. Record your observations in the table.

Nutrient agar plate with E. coli …

Observation of the area under and around the disc

plus penicillin (5 iu) disc

plus streptomycin (25 iu) disc

plus control disc

Questions

1 Which antibiotic was more effective at inhibiting bacterial growth?

.............................................................................................................................................

............................................................................................................................................

2 Why was a control used in this experiment?

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3 How good was your aseptic technique? How do you know? (Hint: Did anything unusual

grow on your agar plate?)

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b2_06 Human guinea pigs

1 Making drugs (medicines) and vaccinations safe

New drugs (medicines) and vaccines are tested carefully before they become available for doctors to prescribe to their patients. Complete this flow chart to show the test stages a new drug (medicine) or vaccine goes through.

.

2 Designing a trial

Imagine that you work for a clinic and that a company has asked you to design a trial to test the safety of a new drug (medicine) to treat high blood pressure.

Work in pairs or threes to design the trial, which will last a month. Answer the questions below when working on your trial design. Remember that you do not have unlimited funds, although you have to make sure the trial is safe. Some ethical issues to consider include the side effects in your test subjects that you would consider acceptable, and if there are any side effects that would make you stop the trial.

How many ‘subjects’ will you have in the trial? How many doctors and nurses will you need?

How many of your test subjects will get the blood pressure drug?

Will you control the activities of the test subjects? What will you allow/not allow them to do?

What will you measure in your trial subjects? How often will you take the measurements?

What else will you record?

Is there anything that would make you stop the trial? Does the whole group agree?

Are there any side effects that would be acceptable?

3 Trial methods (Higher tier only)

Consider the trial that you planned in Activity 2 above, and add these questions to your planning stages.

What type of trial would you plan? (Open-label, blind or double-blind?)

Explain why you have chosen this type of trial.

Would you use a placebo for any of the individuals on the trial? Why/why not?

The drug (medicine) is tested on _____________ in the lab, to check that the drug (medicine) is not poisonous.

The drug (medicine) may then be tested on ____________ .

If animals show no negative response, then the drug (medicine) may be tested on ___________ in a ___________ trial.



b2_07 Your amazing heart

1 Two pumps in one heart

Your teacher will demonstrate how to carry out the dissection of a heart. When you carry out your dissection, try to find the answers to the following questions.

1 How many chambers does the heart have? …………………………………………….

2 Which chamber has the thickest muscle wall? Can you explain why?

…………………………………………………………………………………………………….

…………………………………………………………………………………………………….

3 Thinking about the way the heart pumps, what structures prevent blood from the bottom chambers flowing backwards into the top chambers when the bottom chambers contract?

…………………………………………………………………………………………………….

…………………………………………………………………………………………………….

2 Blood vessels

1 During your dissection, find the main blood vessels that are attached to the heart. How can you tell the difference between an artery and a vein?

2 How many of the blood vessels that are attached to the heart can you name? You should be able to identify:

the aorta − the main artery leaving the heart, carries blood to the body

the pulmonary artery − carries blood to the lungs from the right side of the heart

the pulmonary vein – carries blood from the lungs and enters the left side of the heart

the vena cava − the main vein from the body to the heart, carries blood from the body.

3 Supplying the heart with blood

1 Can you see the blood vessel that supplies the heart itself with blood? What is this vessel called?

2 What do you think the yellow/white substance on the outside of the heart is?



b2_08 Keeping your heart healthy

1 Reducing the risk

Helen has a busy weekend. On Saturday she plays hockey for a local team in the morning and in the afternoon she goes out shopping with her friends. She is always hungry after hockey so they usually go out for a burger or pizza for lunch. On Sundays she swims with her family in the mornings and then takes the dog for a long walk in the afternoon.

Tim believes weekends are for relaxing. He goes out for a few drinks with his friends on Friday and is often in bed with a hangover on Saturday mornings. He has a fried breakfast around lunchtime and starts to organise his evening. He goes out with friends again, this time to a club and only gets a few hours sleep. He has a late start on Sunday, has black coffee instead of breakfast and watches a football match on TV in the afternoon. He doesn’t smoke much, just a few cigarettes in the evening.

Consider the lifestyles of these two people. Discuss with the class:

To what extent are Helen and Tim looking after their hearts?

How could they improve their lifestyles to improve the health of their hearts?

2 Keep on moving

Exercise is an important part of keeping your heart healthy. Record the exercise you take part in during an average week.

Does it meet the recommendation of 30 minutes of exercise each day?

What exercise could you include in your routine to make your lifestyle healthier?

3 A lifestyle disease?

This role play gives you an opportunity to give or to receive advice about a healthy lifestyle. Work in pairs – one of the pair has the ‘doctor’ card, the other has the ‘patient’ card. No-one can read their card out loud, but they have to get the information across during their conversation.

Patient Doctor

I have come to the doctor because I have started to get chest pain and I get out of breath when I walk up the stairs. My father had heart disease; I think I have heart disease too. I am not overweight, but I do smoke 20 cigarettes a day and I have high blood pressure. I want the doctor to prescribe tablets to reduce my blood pressure and reduce my risk of suffering a heart attack.

The patient has a family history of heart disease. He/she is not overweight but he/she has high blood pressure. I must find out her/his symptoms and lifestyle and give her/him advice on how to reduce her/his chances of getting heart disease. I would rather she/he changed her/his lifestyle than prescribe drugs, because I think a lifestyle change would have more impact on reducing the symptoms.



b2_09 Get your pulse racing

Resources

Student Book pages 58−59 Interactive Book: Practical investigations ‘Measuring pulse rate’ Homework pack b2_09

Files on Teacher Pack CD: b2_09_worksheet

Stethoscopes; electronic blood pressure monitor; stopclocks

Learning outcomes B2.3.4 understand that heart rate can be measured by recording the pulse rate

B2.3.5 understand that blood pressure measurements record the pressure of the blood on the walls of the artery

B2.3.6 understand that a blood pressure measurement is given as two numbers, the higher value when the heart

is contracting and the lower value when the heart is relaxed

Numeracy focus: Collecting a class set of data on resting-pulse rate; calculating mean and range for the data set.

ICT focus: Collating class data set using Excel or similar.

In this lesson students are learning to:

explain what the ‘pulse rate’ is

understand what a blood pressure measurement tells us

carry out calculations using experimental data

Key vocabulary

heart rate pulse rate resting heart rate blood pressure high blood pressure low blood pressure


Students need to remember that waste products are taken away in the blood, as well as nutrients and oxygen

being delivered to active cells. Many students forget to include this in their answers to questions about why heart

rate increases with exercise.

Stimuli and starter suggestions

Supply a number of stethoscopes (these can be obtained quite cheaply) and ask students what they are used

for. This should get students talking about listening to the heart, which leads on to counting heart rate. This is

also a good opportunity to find out which students have aspirations toward medicine, nursing or veterinary

school.

Learning activities worksheet b2_09 Low demand Show students how pulse can be measured. Ask them to find the pulse in their wrist (the radial

pulse) or their neck (the carotid pulse). Students practise taking their pulse following the instructions in activity 1 on

the worksheet. They repeat readings, calculate the average of similar readings, and consider the meaning of

‘anomaly’.

Teaching and learning notes: Students need to consider the accuracy and reliability of their results. This activity

reinforces that an average should be taken only if the results collected are similar.

Standard demand Ask students to pool their results of pulse rate. Activity 2 on the worksheet leads students

through some data-processing exercises to find mean pulse rate and range of pulse rates. Reinforce the idea that a

range of pulse rates is normal. In addition, students learn about blood pressure. Blood pressure is hard to measure

without training using a manual machine, but an electronic blood pressure monitor could be used to measure

students’ blood pressures.

Teaching and learning notes: This is an opportunity to revisit ideas about mean, mode and median as different

types of average. The mean is the sum of all the readings divided by the number of readings. The median is the

middle reading if all the readings are written down in order from lowest to highest, and the mode is the most

common reading if all the readings are written in ordert. The range is the difference between the highest value and

the lowest value.

High demand Ask students to look at the relationship between resting heart rate and the amount of exercise they

take in an average week to develop the idea of correlation. In activity 3 students devise a way of determining how

much exercise their classmates do in an average week and plot this against average resting heart rate. The

b2_09 Lesson continued


resulting graph is analysed to determine if there is a relationship between average amount of exercise taken and

resting heart rate. Where an electronic blood pressure monitor is available, this activity can be extended by plotting

student blood pressure on the same graph. Is there a relationship between the average amount of exercise taken

and blood pressure? Ask students to explain any relationships they see. Remind them that a correlation does not

necessarily imply that one factor causes another.

Plenary suggestions Ask students to explain why, when a patient has internal bleeding (bleeding into the inside of the body), the blood

pressure drops and the pulse becomes very faint.

Student Book answers Q1 Because blood vessels are close to the skin’s surface and the blood can be felt pulsing through them.

Q2 Heart rate is measured in beats per minute (bpm).

Q3 They carry blood away from the heart; at a higher pressure than in veins.

Q4 The person could be more likely to die from heart disease or stroke; it might be an indication that they are in

poor overall health.

Q6 The same amount of blood has to travel along a narrower tube partially blocked by fat; so the blood has to flow

at a higher pressure.

Worksheet answers

Activity 1 (Low demand)

Q4 a) A result that does not fit the general trend or is very different from other results in a set.

b) Because you do not know which of the readings lies close to the true (accurate) value; an average taken

from very different readings will give you an inaccurate answer; averages are only accurate if the repeated

readings have values close to each other.

Activity 3 (High demand)

Q1 Slower resting heart rate because their heart muscle would be stronger and able to pump more blood per beat.

Q2 A suitable method might be to give an individual one point for each hour of exercise they do per week and see

how that relates to the resting heart rate. It might be expected that those who do more exercise would be fitter

and so have a lower resting heart rate because their heart is able to pump more blood per beat and it needs to

beat less often to get the same amount of blood around the body.



b2_09 Get your pulse racing

1 Feel the beat

Use your first and second fingers (the two next to your thumb) of your right hand to measure your pulse on the opposite wrist. Turn your left hand palm up and you will find your pulse towards the left side as shown in the diagram.

1 Take your pulse for 1 minute and write the reading below. Repeat a further three times, recording each reading.

Reading 1 ........................ beats per minute




2 If the readings are all fairly similar, calculate the average value for your readings.

Average pulse rate = ....................... beats per minute.

3 If one or two of the readings are very different, you may wish to take additional readings to see what is normal for you.

Additional reading 1 .......................... beats per minute



4 a) What is meant by the term ‘anomaly’?

………………………………………………………………………………………………

b) Why should you not take an average of very different readings?

………………………………………………………………………………………………..

b2_09 Get your pulse racing continued


2 Average pulse rate

Once everyone in the class has measured their pulse rates, collect a class data set. A spreadsheet, such as Excel, could be used to record all the data.

Find out the mean pulse rate of the class. To calculate the mean, add all the resting pulse rates together, then divide by the number of readings.

Average (mean) pulse rate for the class = ………… beats per minute

What is the range of pulse rates (i.e. what was the highest and lowest)?

Highest: ………… beats per minute Lowest: ………… beats per minute

3 Too high or too low?

1 Do you think that people who take regular exercise have a lower or a higher resting heart rate? Explain your answer.

2 Think of a way to quantify the amount of exercise students in your class do in one week. You need to decide what ‘counts’ as exercise. Collect information from at least 10 class members about their resting heart rate and the average amount of exercise they do in one week. Plot this on a graph.

Is there a correlation between resting heart rate and the average amount of exercise a person does? Can you explain why this might be?



b2_10 Blood pressure and lifestyle factors

1 Who should take part in the study?

Imagine you are a doctor at a large practice that is taking part in a large-scale study of how lifestyle factors affect blood pressure.

The study needs to include a large number of randomly selected individuals. You will be asking patients who come to your surgery if they are prepared to take part. The study involves filling in a short questionnaire about their lifestyle and then recording their blood pressure each time they visit for the next two years.

In your group of three, decide which of the patients below would not be suitable to take part in the study, and explain why.

Julie is a 20 year old woman who is three months pregnant. She has no history of heart problems and she does not smoke. She is not overweight, but is anxious about the pregnancy.

Frankie is a 54 year old accountant who has asthma. He smokes 30 cigarettes a day and frequently has a cough or a chest infection.

Helen is 31 and is visiting your area on her one-week holiday. She has trodden on a rusty nail. She thinks her tetanus inoculation is out of date so she has come to have a tetanus booster before she travels home.

Graham is 19 and has diabetes, which is controlled well by insulin injections. He attends a monthly clinic to check that his condition is well managed.

2 A patient’s point of view

If you were a patient at the doctor’s practice where this study was being carried out, what questions would you want to ask before taking part in the study? Still in your groups of three, list the questions about the study you would want to ask the doctor.

Your teacher may ask one person in your group to play the role of the doctor, and the other two in your group to play the role of the patients.

If you were a doctor, how would you invite a patient to take part in such a study?

3 Epidemiological studies

It is very important that the information gathered for an epidemiological study is useful in determining the risk factors for a disease, so scientists have to make sure they are collecting the right information.

1 List the information you think scientists would need about a patient’s lifestyle when they joined the study.

2 Design a questionnaire that would collect the information you would need if you were studying what lifestyle factors were associated with high blood pressure. (Hint: you need to think carefully about how you will ask patients to quantify how healthy their diet is, how stressful their lifestyle is etc.)



b2_11 Homeostasis

1 A constant internal environment

Homeostasis is the process by which the body maintains a steady state inside itself despite the conditions outside. A good model for this system is an incubator for a premature baby. A baby who is born before about 37 weeks’ gestation has difficulty maintaining the correct body temperature. The baby may be put in an incubator at 37 °C until the baby is able to stay at this temperature on its own. Look at this diagram of an incubator and explain how the temperature is controlled, using the key words ‘receptor’, ‘processing centre’ and ‘effector’.

Ventilation flaps may be opened

to lower the temperature. The fan heater increases

the air temperature.

Sometimes a

temperature

sensor may be

taped to the

baby’s abdomen.

The required temperature is set at the

control panel by medical staff. The

computer monitors the temperature and

responds to changes by sending messages

to the heater and ventilation flaps.

b2_11 Homeostasis continued


2 How the control systems work

It is important that the human body stays within a narrow range of temperatures in order to function normally. Because of this, the human body has a system with receptors, a processing centre and effectors, just like an incubator, for controlling its temperature.

The receptors are found in the hypothalamus, which is in the brain.

The processing centre is in the brain.

If the body becomes too hot, it can cool itself by a process called vasodilation – the blood vessels dilate and become closer to the skin surface.

If the body becomes too cold, vasoconstriction occurs – this means that the blood vessels narrow and move away from the skin surface.

,Using the key terms ‘receptors’, ‘processors’ and ‘effectors’, describe how the human body maintains its temperature at 37 °C in the two situations below:

If it is outside for a few hours on a snowy day at a temperature of −2 °C.

If the external temperature is 40 °C.

You may wish to refer to some parts of the diagram in the Student Book on page 63.

3 Negative feedback (Higher tier only)

Negative feedback keeps a system at a steady state by reversing any changes that occur. In an incubator, it would cause problems for the baby if the temperature was too high or too low. Many incubators have small ‘flaps’ or windows in the top that can open if the temperature gets too high. 1 Write out the explanation below, filling in the gaps, of how negative feedback allows

an incubator to detect and respond to an increase in air temperature inside the incubator above the set temperature (32 °C).

The rise would be detected by the ______. The processing centre would send a message to the heater to ______ ______ , and the windows to ______ . The heater would ______ _____ . The windows would ______ . 2 Using the same structure for your response, write what would happen if the

temperature of the air in the incubator fell below the set temperature of 32 °C. 3 How is the negative feedback system in the incubator similar to the negative feedback

system in the body? (Hint: In the body, what would be the equivalent of the incubator’s ‘heater’? What would be the body’s equivalent of the windows opening?)



b2_12 Water in, water out − practical

P Investigating the effect of concentration of solutions on onion cells

Objectives

In this experiment you will be learning how red onion cells respond to being immersed in distilled water and then in sucrose solution. This will help you to understand how important it is that the blood plasma concentration within our bodies remains within a narrow range.

You will observe what happens to the vacuole of red onion cells when the cells are immersed in:

distilled water

and then in concentrated sucrose solution.

Safety warning:

You may need to use a scalpel or dissecting needle to peel away the layer of onion cells. Be very careful not to injure yourself or others.

Equipment and materials

microscope • slide and coverslip • red onion • distilled water • pipette • sucrose solution • tissue or blotting

paper • scalpel or dissection needle • cutting tile

Method

1 Set up your microscope.

2 Take a piece of red onion and peel away the layer containing the cells that contain red pigment very carefully. Place a piece of the skin that has these cells in it on the microscope slide, add a drop of distilled water, and then lower the coverslip carefully. (Put one edge of the coverslip down first and then gently lower the other side. This helps to prevent air bubbles forming.)

3 Look at the cells under the microscope. Describe what you see.

4 Now add a few drops of sucrose solution along one side of the coverslip and put the tissue or blotting paper in the fluid on the other side. This will ‘draw through’ the sucrose solution so the cells will then be bathed in sucrose solution instead of water. Observe the cells as the sucrose solution is drawn through and for several minutes afterwards.

5 Make labelled drawings of what you observed:

Red onion cells in distilled water Red onion cells in sucrose solution

b2_12 Water in, water out continued


Questions

1 Describe the differences between the cells in the two solutions. .................................................................................................................................................. .................................................................................................................................................. .................................................................................................................................................. 2 Explain, using your observations of the red onion cells, why it is so important that the

concentration of fluid surrounding cells is exactly right. .................................................................................................................................................. .................................................................................................................................................. ..................................................................................................................................................

.................................................................................................................................................. ..................................................................................................................................................



b2_12 Water in, water out

1 Keeping the right amount of water

The kidneys are the organs responsible for maintaining the correct level of water in the body. You will either dissect a kidney or watch a video or demonstration of a kidney dissection. Use the diagram below to write a description of the different parts of the kidney that you see in the dissection.

…………………………………………………………………………………………………………

…………………………………………………………………………………………………………

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b2_12 Water in, water out continued


2 Why water level is important

If cells are bathed in fluid that does not have the correct balance of water and salts for that organism, the cells may take in water and become swollen, or lose water and become dehydrated. You can see this happening if you look at red onion cells under a microscope when they are bathed in distilled water and then in sucrose solution. 1 Plant cells have a cell wall so they do not burst when you do this experiment. What do

you think would happen if you carried out this experiment using red blood cells? 2 Most freshwater fish die if put into salt water. Explain why.

3 Kidneys control water levels

‘Explain how the collecting duct of the kidney controls the concentration of the urine’. (6 marks) Work in pairs to answer this exam-style question. You will need to use the information in the Student Book on page 65 to help you.

Written answers should have good spelling, grammar and punctuation.

They should answer the question clearly and fully.

They should be well structured and not include irrelevant material.

After you have written your answer and made as good as it can be, team up another pair of students and assess each other’s work – use the mark scheme that your teacher will provide.



b2_13 Your kidneys

1 The kidneys

Working in pairs, cut these cards out and use them to construct a summary flow chart to show how the balance of water in the body is maintained. Discuss with your partner the best way to present the information.

Draw arrows between the boxes to show how events might occur and add annotations and examples where possible.

Do not stick your boxes down until you have discussed your flow chart with another pair.

2 Drugs that affect water balance in the body

Add these cards and any further explanations you can to your summary flow chart.

Blood plasma concentration is just right.

Blood plasma is too dilute.

Blood plasma is too concentrated.

Kidneys produce a greater quantity of more dilute urine.

Kidneys produce a smaller quantity of

more concentrated urine.

Alcohol causes the kidneys to

produce a large quantity of dilute urine, even if the blood plasma is too concentrated.

Ecstasy causes the kidneys to

produce a small quantity of concentrated urine, even if the

blood plasma is too dilute.

This excess of water in the body can lead to the cells

swelling. If this occurs in the brain, this can cause brain

damage.

This reduction of water in the body can lead to dehydration, which can cause headache,

nausea and dizziness.

b2_13 Your kidneys continued


3 The kidneys and ADH (Higher tier only)

Use the statements below to add information about ADH to your flow chart. You may like to use a different colour for this information.

The action of the kidneys and the amount of water they retain or release is under the control of anti-diuretic hormone (ADH).

ADH decreases the water lost by the kidneys.

Alcohol inhibits the action of ADH.

Ecstasy increases ADH production.

Documents

B2 Module Introduction - WikispacesKeeping+Healthy... · B2 Module Introduction ... Students will learn about the microbes that inhabit their bodies and how their immune systems