BIOLOGY - Assets.pearsonglobalschools
Uncorrected proof, all content subject to change at publisher discretion. Not for resale, circulation or distribution in whole or in part. Pearson 2017EDEXCEL INTERNATIONAL GCSE (9 –1)BIOLOGYStudent BookPhilip Bradfield, Steve PottereBookincluded
Uncorrected proof, all content subject to change at publisher discretion. Not for resale, circulation or distribution in whole or in part. Pearson 2017EDEXCEL INTERNATIONAL GCSE (9 –1)BIOLOGYStudent BookPhilip BradfieldSteve Potter
Uncorrected proof, all content subject to change at publisher discretion. Not for resale, circulation or distribution in whole or in part. Pearson 2017CONTENTSiiiCOURSE STRUCTUREIVABOUT THIS BOOKVIASSESSMENT OVERVIEWVIIUNIT 1: ORGANISMS AND LIFE PROCESSES02UNIT 2: ANIMAL PHYSIOLOGY38UNIT 3: PLANT PHYSIOLOGY134UNIT 4: ECOLOGY AND THE ENVIRONMENT186UNIT 5: VARIATION AND SELECTION226UNIT 6: MICROORGANISMS AND GENETIC MODIFICATION280APPENDIX303GLOSSARY306INDEX311
Uncorrected proof, all content subject to change at publisher discretion. Not for resale, circulation or distribution in whole or in part. Pearson 201798ANIMAL PHYSIOLOGYCHEMICAL COORDINATION7 CHEMICAL COORDINATIONThe nervous system (Chapter 6) is a coordination system forming a link between stimulus and response. The bodyhas a second coordination system, which does not involve nerves. This is the endocrine system. It consists of organscalled endocrine glands, which make chemical messenger substances called hormones. Hormones are carried in thebloodstream.LEARNING OBJECTIVESBy the end of this chapter you should be able to: progesterone* oestrogen* describe how responses can be controlled by hormonalcommunication understand the differences between nervous andBIOLOGY ONLY antidiuretic hormone (ADH)*hormonal control follicle stimulating hormone (FSH)* understand the sources, roles and effects of the luteinising hormone (LH)*following hormones: adrenaline insulin testosterone**These hormones will be dealt with in more detail in laterchapters.GLANDS AND HORMONESA gland is an organ that releases or secretes a substance. This means thatcells in the gland make a chemical which leaves the cells through the cellmembrane. The chemical then travels somewhere else in the body, where itcarries out its function. There are two types of glands – exocrine and endocrineglands. Exocrine glands secrete their products through a tube called a duct.For example, salivary glands in your mouth secrete saliva down salivary ducts,and tear glands secrete tears through ducts that lead to the surface of the eye.Endocrine glands have no duct, and so are called ductless glands. Instead,their products, the hormones, are secreted into the blood vessels that passthrough the gland (Figure 7.1).exocrine glandendocrine glandblood supplyduct(outside ofgland, e.g. lumenof gut) Figure 7.1 Exocrine glands secrete their products though a duct, while endocrine glands secretehormones into the blood.This chapter looks at some of the main endocrine glands and the functions ofthe hormones they produce. Because hormones are carried in the blood, theycan travel to all areas of the body. They usually only affect certain tissues or
Uncorrected proof, all content subject to change at publisher discretion. Not for resale, circulation or distribution in whole or in part. Pearson 2017ANIMAL PHYSIOLOGYCHEMICAL COORDINATIONKEY POINTThe receptors for some hormonesare located in the cell membraneof the target cell. Other hormoneshave receptors in the cytoplasm, andsome in the nucleus. Without specificreceptors, a cell will not respond to ahormone at all.99organs, called ‘target organs’, which can be a long distance from the glandthat made the hormone. Hormones only affect particular tissues or organsif the cells of that tissue or organ have special chemical receptors for theparticular hormone. For example, the hormone insulin affects the cells of theliver, which have insulin receptors.THE DIFFERENCES BETWEEN NERVOUS AND ENDOCRINECONTROLAlthough the nervous and endocrine systems both act to coordinate bodyfunctions, there are differences in the way that they do this. These aresummarised in Table 7.1.Table 7.1: The nervous and endocrine systems compared.NERVOUS SYSTEMENDOCRINE SYSTEMworks by nerve impulses transmitted through nerve cells (althoughchemicals are used at synapses)works by hormones transmitted through the bloodstreamnerve impulses travel fast and usually have an ‘instant’ effecthormones travel more slowly and generally take longer to actresponse is usually short-livedresponse is usually longer-lastingimpulses act on individual cells such as muscle fibres, so have a verylocalised effecthormones can have widespread effects on different organs (although theyonly act on particular tissues or organs if the cells have the correct receptors)THE ENDOCRINE GLANDSpituitarythyroidThe positions of the main endocrine glands are shown in Figure 7.2. A summaryof some of the hormones that they make and their functions is given in Table 7.2.The pituitary gland (often just called ‘the pituitary’) is found at the base ofthe brain. It produces a number of hormones, including antidiuretic hormone(ADH), which acts on the kidneys, controlling the amount of water in theblood (see Chapter 8). The pituitary also releases hormones that regulatereproduction (see Chapter 9).Just above the pituitary is a part of the brain called the hypothalamus. Thepituitary contains neurones linking it to the hypothalamus, and some of itshormones are produced under the control of the brain.Table 7.2: Some of the main endocrine glands, the hormones they produce and their functions.adrenalGLANDpituitarypancreasHORMONESOME FUNCTIONS OF THE HORMONESfollicle stimulating hormone(FSH)luteinising hormone (LH)stimulates egg development and oestrogensecretion in females and sperm production in malesstimulates egg release (ovulation) in females andtestosterone production in malescontrols the water content of the bloodantidiuretic hormone (ADH)ovary(in women)testis (in men) Figure 7.2 The main endocrine glands of thebody.KEY POINTThe pituitary is a link between thenervous and endocrine coordinationsystems.thyroidthyroxinecontrols the body’s metabolic rate (how fastchemical reactions take place in cells)pancreasinsulinglucagonlowers blood glucoseraises blood glucoseadrenalsadrenalineprepares the body for physical activitytestestestosteronecontrols the development of male secondary sexualcharacteristicsovariesoestrogencontrols the development of female secondarysexual characteristicsregulates the menstrual cycleprogesterone
Uncorrected proof, all content subject to change at publisher discretion. Not for resale, circulation or distribution in whole or in part. Pearson 2017100 ANIMAL PHYSIOLOGYCHEMICAL COORDINATIONThe pancreas is both an endocrine and an exocrine gland. It secretes twohormones involved in the regulation of blood glucose, and is also a gland ofthe digestive system, secreting enzymes through the pancreatic duct into thesmall intestine (see Chapter 4). The sex organs of males (testes) and females(ovaries) are also endocrine organs. In addition to their role in producing sexcells, the testes and ovaries make hormones that are involved in controllingreproduction. This topic is covered more fully in Chapter 9. We will now look atthe functions of two hormones in more detail.ADRENALINE – THE ‘FIGHT OR FLIGHT’ HORMONEDID YOU KNOW?‘Adrenal’ means ‘next to thekidneys’, which describes wherethe adrenal glands are located– on top of these organs (seeFigure 7.2).When you are frightened, excited or angry, your adrenal glands secrete thehormone adrenaline.Adrenaline acts at a number of target organs and tissues, preparing the bodyfor action. In animals other than humans this action usually means dealingwith an attack by an enemy, where the animal can stay and fight or run away– hence ‘fight or flight’. This is not often a problem with humans, but there areplenty of other times when adrenaline is released (Figure 7.3).glucose is releasedfrom the liverhair stands on end,making the animallook largerblood is directedaway from the gutand towards themusclespupils dilateheart beats fasterbreathing becomesfaster and deeper Figure 7.3 Many human activities cause adrenaline to be produced, notjust a ‘fight or flight’ situation! Figure 7.4 Adrenaline affects the body of an animal in many ways.If an animal’s body is going to be prepared for action, the muscles need agood supply of oxygen and glucose for respiration. Adrenaline producesseveral changes in the body that make this happen (Figure 7.4) as well as otherchanges to prepare for fight or flight. The breathing rate increases and breaths become deeper, taking moreoxygen into the body. The heart beats faster, sending more blood to the muscles, so that theyreceive more glucose and oxygen for respiration. Blood is diverted away from the intestine and into the muscles. In the liver, stored carbohydrate (glycogen) is changed into glucose andreleased into the blood. The muscle cells absorb more glucose and use itfor respiration. The pupils dilate, increasing visual sensitivity to movement. Body hair stands upright, making the animal look larger to an enemy. Mental awareness is increased, so reactions are faster.
Uncorrected proof, all content subject to change at publisher discretion. Not for resale, circulation or distribution in whole or in part. Pearson 2017ANIMAL PHYSIOLOGYCHEMICAL COORDINATIONIn humans, adrenaline is not just released in a ‘fight or flight’ situation, but inmany other stressful activities too, such as preparing for a race, going for a jobinterview or taking an exam.INSULIN – CONTROL OF BLOOD GLUCOSEYou saw earlier that adrenaline can raise blood glucose from stores in theliver. The liver cells contain carbohydrate in the form of glycogen. Glycogenis made from long chains of glucose sub-units joined together, forming a largeinsoluble molecule (see Chapter 4). Being insoluble makes glycogen a goodstorage product. When the body is short of glucose, the glycogen can bebroken down into glucose, which then passes into the bloodstream.Adrenaline raises blood glucose concentration in an emergency, but otherhormones act all the time to control the level, keeping it fairly constant at alittle less than 1 g of glucose in every dm3 (cubic decimetre) of blood. The mainhormone controlling glucose is insulin. Insulin is made by special cells in thepancreas. It stimulates the liver cells to take up glucose and convert it intoglycogen, lowering the level of glucose in the blood.DID YOU KNOW?The pancreas also makes ahormone called glucagon, whichhas the opposite effect to insulin– it raises blood glucose.The concentration of glucose in your blood will start to rise after you have hada meal. Sugars from digested carbohydrate pass into the blood and are carriedto the liver in the hepatic portal vein (Chapter 5). In the liver the glucose isconverted to glycogen, so the blood leaving the liver in the hepatic vein has alower concentration of glucose than when it enters the liver.DIABETESSome people have a disease where their pancreas cannot make enoughinsulin to keep their blood glucose level constant – it rises to very highconcentrations. The disease is called diabetes. One symptom of diabetes canbe detected by a chemical test on urine. Normally, people have no glucoseat all in their urine. Someone suffering from diabetes may have such a highconcentration of glucose in the blood that it is excreted in their urine. This canbe shown up by using coloured test strips (Figure 7.5).KEY POINT Figure 7.5 Coloured test strips are used todetect glucose in urine.We should really refer to this disease by its full name, which is 'type 1' diabetes. Thereis also a ‘type 2’ diabetes, where the pancreas produces insulin but the body showsinsulin resistance, where insulinhas less effect than it should do. At first the pancreas makes extra insulin, buteventually it can’t continue to make enough to maintain blood glucose at a normallevel. Type 2 diabetes is common in people who are overweight and eat a poor dietthat is high in sugar and other carbohydrates. It can be prevented and controlled byeating a good diet and taking regular exercise. Type 2 diabetes also tends to happen inmiddle-aged or older people, whereas type 1 can happen at any age, and is commonin childhood.Another symptom of diabetes is a constant thirst. This is because the highblood glucose concentration stimulates receptors in the hypothalamus of thebrain. These ‘thirst centres’ are stimulated, so that by drinking, the person willdilute their blood.Severe diabetes is very serious. If it is untreated, the sufferer loses weight andbecomes weak and eventually falls into a coma and dies.Carbohydrates in the diet, such as starch and sugars, are the source ofglucose in the blood, so a person with diabetes can help to control their blood101
Uncorrected proof, all content subject to change at publisher discretion. Not for resale, circulation or distribution in whole or in part. Pearson 2017102 ANIMAL PHYSIOLOGYCHEMICAL COORDINATIONsugar if they limit the amount of carbohydrate that they eat. However a personwith diabetes (type 1) also needs to receive daily injections of insulin to keepthe glucose in their blood at the right level.KEY POINTInsulin is a protein, and if it were to betaken by mouth in tablet form, it wouldbe broken down by protease enzymesin the gut. Instead it is injected intomuscle tissue, where it is slowlyabsorbed into the bloodstream.People with diabetes can check their blood glucose using a special sensor.They prick their finger and place a drop of blood on a test strip. The strip isthen put into the sensor, which gives them an accurate reading of how muchglucose is in their blood (Figure 7.6). They can then tell when to inject insulinand how much to inject.DID YOU KNOW?Insulin for the treatment ofdiabetes has been availablesince 1921, and has kept millionsof people alive. It was originallyextracted from the pancreases ofanimals such as pigs and cows,and much insulin is still obtainedin this way. However, sincethe 1970s, human insulin hasbeen produced commercially,from genetically modified (GM)bacteria. The bacteria have theirDNA ‘engineered’ to containthe gene for human insulin (seeChapter 22). Figure 7.6 Sensor for measuring blood glucose.CHAPTER QUESTIONSSKILLSMore questions on chemical coordination can be found at the end of Unit 2 onpage 136CRITICAL412 THINKING35671 Which10 following89 of the1112 statement(s) is/are true?1 Insulin converts glucose to glycogen2 Insulin causes blood glucose levels to fall3 Glucose is stored as glucagon in the liver4 Glycogen can be broken down to release glucose into the bloodA 2 onlyB 2 and 4C 3 and 4D 1 and 212345671089 hormone11controls122 Whichthe development of the male secondary sexualcharacteristics?A testosteroneB oestrogenC progesteroneD follicle stimulating hormone (FSH)
1SKILLSCHEMICAL COORDINATION10312345610 following7 Which89 the1112will not happen when the hormone adrenaline is3ofreleased?A an increase in heart rateB an increase in blood flow to the gutC dilation of the pupilsD an increase in breathing rate12345610 following7 Which89 the1112is a symptom of type 1 diabetes?4ofA high insulin level in the bloodB low glucose level in the bloodC glucose present in the urineD insulin present in the urine234567851011 are 12a 9Hormonessecreted by endocrine glands. Explain the meaning of thefour words in italicsANALYSIS123456710 hormones91112 A to D in the table.b 8IdentifytheHORMONEONE FUNCTION OF THIS HORMONEAstimulates the liver to convert glucose to glycogenBcontrols the ‘fight or flight’ responsesCcontrols the breaking of the voice at puberty in boysDcompletes the development of the uterus lining during the menstrual cycle6 The graph shows the changes in blood glucose in a healthy woman over a12-hour period.blood glucose/mg per 100cm3 of bloodUncorrected proof, all content subject to change at publisher discretion. Not for resale, circulation or distribution in whole or in part. Pearson 2017ANIMAL PHYSIOLOGY130120110100XY908070080012001600time of day200012345678911 why12 there was a rise in blood glucose at X.a 10Explain123456789b 10How11does12the body bring about a decrease in blood glucose at Y? Youranswer should include the words insulin, liver and 8933455c Diabetes is a disease where the body cannot control the concentration ofglucose in the blood.10 i Why1112 this dangerous?isii 10Describetwoways a person with diabetes can monitor their blood91112glucose level.iii Explain101112 two ways that a person with diabetes can help to control theirblood glucose level.
Uncorrected proof, all content subject to change at publisher discretion. Not for resale, circulation or distribution in whole or in part. Pearson 2017EDEXCEL INTERNATIONAL GCSE (9 –1)BIOLOGYStudent BookPhilip Bradfield, Steve PotterEdexcel International GCSE (9–1) Biology prepares students for the new2017 International GCSE (9–1) Biology specification. This resource providescomprehensive coverage of the new specification. This book, which includesaccess to the eBook, is designed to provide students with the best preparationpossible for the examination: Written by highly experienced International GCSE Biology teachers andauthors Philip Bradfield and Steve PotterContent is mapped closely to the specification to providecomprehensive coverageExam practice throughout, with differentiated revision exercises and examstyle practiceSignposted transferable skillsIntegrated Pearson Progression ScaleReviewed by a language specialist to ensure the book is written in a clearand accessible style for students whose first language may not be EnglishGlossary of key Biology terminology, along with full answers included onthe eBookeBook included.www.pearsonglobalschools.com
EDEXCEL INTERNATIONAL GCSE (9–1) BIOLOGY Student Book Philip Bradfield, Steve Potter eBook Uncorrected included proof, all content subject to change at publisher discretion. Not for resale, circulation or distrib
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