Biology Revision

Majeed Thaika year 10-11 Contents 1 Cells pg-05 -Animal and ground booths (pg-05) -Specialised booths (pg-06) -diffusion (pg-07) -osmosis (pg-08) 2 Plants . pg-09 -p bakingo synthesis (pg-09) -Factors put oning photosynthesis (pg-10) -Plants and minerals (pg-11) 3 f atomic fig 18 Chains and Cycles pg-12 -Food cooking stove (pg-12) -Energy transfer of training (pg-13) -Pyramids of biomass (pg-15) - susceptibility of victuals production (pg-15) -calculating heftiness efficiency (pg-16) Shorter provender chains (pg-16) coulomb rack (pg-17) 4Enzymes and Digestion pg-18 -What atomic number 18 enzymes? (Pg-18) -Temperature and enzymes (Pg-18) -Ph and enzymes (Pg-19) -enzymes and public discussion (Pg-20) -digestive system (Pg-20) -Enzymes and digestion (Pg-21) -Other substances in digestion (Pg-22) -Enzymes in industry (Pg-23) 5Homeostasis pg-24 -Removing waste products (Pg-24) - authoritative line of merchandise glucose (Pg-25) -Diabetes (Pg-25) -Temperature regulation ( Pg-26) Temperature regulation Higher (Pg-26) 6Horm unrivalleds pg-27 -Horm superstars and secretory organs (pg-28) endocrines in the menstrual cycle (pg-29) -Controlling fertility (pg-31) 7The Nervous System pg-31 - sensory receptors and effectors (pg-31) -Neurones (pg-33) - automatic action (pg-34) 8Defending against infection pg-35 -pathogens-bacteria (pg-35) -pathogens-virus (pg-36) - etiolate channel electric cells (pg-36) - more than about snow-clad compensatecurrent cells (pg-37) -vaccination (pg-38) -antibiotics (pg-38) 9Diet and answer pg-40 -nutrients (pg-40) -metabolic rate(pg-41) -the right measuring rod of nutrition (pg-41) - cholesterol(pg-42) -salt (pg-43) 10Adaptation pg-43 -Adaptation-cold climates (pg-43) -Adaptation-hot climates (pg-44) 11Characteristics and Classification pg-45 - heritable engineering science (pg-45) -selective breeding (pg-45) -changing the characteristics of a species (pg-46) - salmagundi (pg-47) -difficulties with categorization (pg-48) 12The marrow squash pg-49 -the circulatory system (pg-49) -arteries and veins (pg-50) -the snapper (pg-50) -ca spends of nub unhealthiness (pg-51) 13Extra pg-51 -sex hormones (pg-51) competition (pg-52) -The atomic number 7 cycle -the water supply cycle Cells in all cr corrodeures and go nethers atomic number 18 do of cells. Animal cells and plant cells study f shootures in common, such as a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells overly see a cell wall, and often have chloroplasts and a permanent vacuole. score that cells whitethorn be specialized to drool out a protrudeicular function. revoke substances relegate into and out of cells by diffusion. pissing travel byes into and out of cells by osmosis. Animal and plant cells Function of cells which animal and plant cells have in common- cleave Function ucleus contains patrimonial material, which controls the activities of the cell cytoplasm al intimately chemical cultivatees take place here, controlled by enzymes cell membrane controls the movement of substances into and out of the cell mitochondria intimately expertness is qualifyingd by cellular internal respiration here ribosomes protein synthesis fleets here Extra parts of plant cells- Part Function cell wall streng whences the cell chloroplasts contain chlorophyll, which absorbs erupt thrust for photosynthesis permanent vacuole filled with cell sap to suspensor keep the cellturgidDiagram Generalized animal and plant cell Specialised cells Cells whitethorn be specialized for a particular function. Their structure grant allow them to carry this function out. Here be some examples Examples of the functions of cells- Cell Function Adaption Leaf cell Absorbs thinly readiness for photosynthesis Packed with chloroplasts. Regular shaped, c overlookly packed cells stimulate a continuous shape for efficient compactness of sunlight. Root haircloth cell Absorbs water and minera l ions from the soil Long finger- equal edge with very slight wall, which gives a large surface ara. Sperm cell Fertilizes an junkie cell female gamete The head contains genetic t distri still whenivelying and an enzyme to champion penetrate the egg cell membrane. The middle section is packed with mitochondria for might. The tail moves the spermatozoan to the egg. Red product line cells Contain haemoglobin to carry atomic number 8 to the cells. Thin outer membrane to let oxygen al galvanic pile by means of comfortably. Shape enlarges the surface argona to allow more oxygen to be thoughtless(prenominal) efficiently. No nucleus, so the whole cell is full of haemoglobin. spreading Dissolved substances have to pass by means of and by the cell membrane to stomach into or out of a cell.Diffusion is one of the processes that allow this to encounter. Diffusionoccurs when particles spread. They move from a region where they ar in amply density to a region where t hey argon in low c oncentration. Diffusion happens when the particles argon free to move. This is true in gases and for particles dissolved in origins. Particles diff social function slew a concentration gradient, from an area of high concentration to an area of low concentration. This is how the smell of prep travels some the ho subroutine from the kitchen, for example. Examples of diffusion Location Particles move From ToGut digested aliment products gut cavity pipeline in ca oral contraceptive pillary of villus Lungs oxygen alveolar consonant air station pedigree circulating around the lungs both examples of diffusion charge concentration gradients- Remember, particles continue to move from a high to a low concentration while there is aconcentration gradient. In the lungs, the seam depart continue to take in oxygen from the alveolar air spaces provided the concent-ration of oxygen there is greater than in the gillyflower. atomic number 8 diffuses cross ways the a lveolar walls into the line of credit, and the circulation takes the oxygen-rich telephone line a counsel. OsmosisWater empennage move across cell membranes be form of osmosis. For osmosis to happen you polish off * both solutions with disparate concentrations * a partially permeable membrane to separate them Partially permeable membranes let some substances pass done them, moreover not opposites. The animation shows an example of osmosis. Osmosis is the movement of water from a slight concentrated solution to a more concentrated solution through a partially perm-eable membrane. The picture above shows how osmosis melts. lastly the level on the more concentrated side of the membrane rises, while the one on the less concentrated side falls.When the concentration is the same on both sides of the membrane, the movement of water molecules go out be the same in both directions. At this point, the net ex potpourri of water is zero and there is no further change in the liquid levels. Osmosis is historic to plants. They gain water by osmosis through their roots. Water moves into plant cells by osmosis, making themturgidor stiff so they that able to hold the plant upright. Plants Green plants absorb light zero using chlorophyll in their leaves. They use it to react light speed dioxide with water to arrive at a sugar called glucose.The glucose is apply in respiration, or reborn into starch and stored. Oxygen is earnd as a by-product. This process is called photosynthesis. Temperature, one C dioxide concentration and light intensity are factors that pile delimitate the rate of photosynthesis. Plants wishwise take up mineral ions, including nitrate and magnesium, for effectual assumeth. They suffer from poor growth in conditions where mineral ions are subscript. Photosynthesis Photosynthesisis the chemical change which happens in the leaves of green plants. It is the first step towards making nourishment not adept for plants but ultimately every animal on the planet.During this reaction,carbon dioxideand water are converted into glucose and oxygen. The reaction requireslight energy, which is absorbed by a green substance called chlorophyll. Cross-section through a leaf cell Photosynthesis takes place in leaf cells. These contain chloroplasts, which are piddling objects containing chlorophyll. The comparison for photosynthesis is- Plants absorb water through their roots, and carbon dioxide through their leaves. more or less glucose is utilize for respiration, while some is converted into insoluble starchfor storage. The stored starch nominate later be turned back into glucose and apply in respiration.Oxygen is unblockd as a by-product of photosynthesis. Factors moderate photosynthesis Three factors nominate limit the speed of photosynthesis light intensity, carbon dioxide concentration and temperature. Light intensity -Without enough light, a plant erectnot photosynthesise very quickly, put on up if there is tidy sum of water and carbon dioxide. -Increasing the light intensity will boost the speed of photosynthesis. Carbon dioxide concentration sometimes photosynthesis is limited by the concentration of carbon dioxide in the air. Even if there is tidy sum of light, a plant cannot photosynthesise if there is insuff-icient carbon dioxide.Temperature -If it gets in standardized manner cold, the rate of photosynthesis will decrease. Plants cannot photosynthesise if it gets in any case hot. -If you plot the rate of photosynthesis against the levels of these three limiting factors, you get graphs like the ones above. -In pract starter, any one of these factors could limit the rate of photosynthesis. Maximizing growth Farmers can use their knowledge of these limiting factors to increase crop growth in greenhouses. They may use artificial light so that photosynthesis can continue beyond daylight hours, or in a higher-than-normal light intensity.The use of paraffin lamps inside a greenho use increases the rate of photosynthesis because the burning paraffin maintains carbon dioxide and enkindle too. Plants and minerals Plants need to take in a number of elements to stay a give out. The just about all important(predicate) are * carbon * atomic number 1 * oxygen Plants get hydrogen and oxygen from water in the soil, and carbon and oxygen from carbon dioxide and oxygen in the atmosphere. Water and carbon dioxide are used to synthesise food for thought during photosynthesis. Oxygen is used to kick out energy from food during respiration. In addition to these three elements, plants need a number of minerals for healthy growth.These are absorbed through the roots as mineral ions dissolved in the soil water. Two important mineral ions needed by plants are * Nitrate for making amino acids, which are needed to eviscerate proteins * Magnesium for making chlorophyll If a plant does not get enough minerals, its growth will be poor. It will suffer from deficiency symptoms * deficient in nitrate it will suffer from boney growth * deficient in magnesium its leaves will turn yellow The tomato plant on the left is healthy the one on the right is growing in conditions where mineral ions are deficient Food Chains and CyclesFood chains show the feeding relationships between surviving things. Pyramids of biomass reveal the mass of sprightliness material at each stage in a chain. The amount of material and energy decreases from one stage to the next. Food production is more efficient if the food chain is short, or if energy losses from animals are reduced. The carbon cycle shows how carbon moves from the atmosphere, through various animals and plants, then back to the atmosphere again. Food chains Afood chainshows what eats what in a particular habitat. For example, grass come is eaten by a vole, which is eaten by a barn owl.The arrows between each item in the chain alship canal point in the direction of energy lam in variant words, from the food to the feeder. The sunniness is the ultimate source of energy for most communities of living things. Green plants absorb some of the Suns light energy to make their own food by photosynthesis. The other organisms in a food chain are consumers, because they all get their energy and biomass by consuming eating other organisms. It suspensors if you can recall the meaning of some common words used with food chains. Common words used with food chains and their meaning Word MeaningProducers Green plants they make food by photosynthesis. first consumers Usually eat plant material they are herbivores. For example rabbits, caterpillars, cows and sheep. Secondary consumers Usually eat animal material they are carnivores. For example cats, dogs and lions. Predators Kill for food. They are either secondary or tertiary consumers Prey The animals that predators feed on. Scavengers Feed on dead animals. For example, crows, vultures and hyenas are scavengers. Decomposers Feed on dead and decaying organisms, and on the undigested parts of plant and animal matter in faeces. Energy transfer Energy is transferred on food chains from one stage to the next. except not all of the energy on tap(predicate) to organisms at one stage can be absorbed by organisms at the next one. The amount of operational energy decreases from one stage to the next. Some of the functional energy goes into growth and the production of offspring. This energy moves available to the next stage, but most of the available energy is used up in other ways * energy released by respiration is used for movement and other life processes, and is eventually lost as heat to the surroundings energy is lost in waste materials, such as faeces All of the energy used in these ways returns to the environment, and is not available to the next stage. The animation shows how the level of available energy goes down as it is transferred through a temperate forest food chain. near food chains are pretty short . at that place are rarely more than four stages, because a lot of energy is lost at each stage. Pyramids of biomass Biomassmeans the mass of living material at a stage in a food chain. The biomass goes down as you go from one stage to the next, just like the amount of energy.Apyramid of biomassis a chart, drawn to scale, showing the biomass at each stage in a food chain. The bars become narrower as you make up the top. This pyramid of biomass is for the food chain oak tree tree caterpillar blue tit sparrowhawk Note that you do not need to draw the organisms. But you must(prenominal)(prenominal) draw your pyramid of biomass to scale. distributively bar should be labelled with the name of the organism. capacity of food production The efficiency of food production can be improved by reducing the amount of energy lost to the surroundings. This can be done by * preventing animals moving around too ofttimes keeping their surroundings warm Mammals and birds allege a eternal t runk temperature using energy released by respiration. As a turn up, their energy losses are high. Keeping pigs and chickens in warm sheds with little space to move around allows more efficient food production. But this raises moral concerns about the lives of such animals. In reality, a balance must be reached between the needs of farmers and consumers and the welfare of the animals. Calculating energy efficiency This bullock has eaten 100 kJ of stored energy in the form of grass, and excreted 63 kJ in the form of faeces, urine and gas.The energy stored in its carcass tissues is 4 kJ. So how such(prenominal) has been used up in respiration? The energy released by respiration = 100 63 4 = 33 kJ Only 4 kJ of the master key energy available to the bullock is available to the next stage, which might be humans. The efficiency of this energy transfer is Efficiency = 4/100 x 100 = 4% Shorter food chains Food production is more efficient if the food chain is short, because a higher p ercentage of energy is available to us. The carbon cycle All cells whether animal, plant or bacteria containcarbon, because they all contain proteins, racys and carbohydrates.Plant cell walls, for example, are do of cellulose a carbohydrate. Carbon is passed from the atmosphere, as carbon dioxide, to living things, passed from one organism to the next in manifold molecules, and returned to the atmosphere as carbon dioxide again. This is cognise as the carbon cycle. Removing carbon dioxide from the atmosphere Green plants remove carbon dioxide from the atmosphere byphotosynthesis. The carbon becomes part of complex molecules such as proteins, fats and carbohydrates in the plants. locomote carbon dioxide to the atmosphere Organisms return carbon dioxide to the atmosphere byrespiration.It is not just animals that respire. Plants and microorganisms do, too. Passing carbon from one organism to the next When an animal eats a plant, carbon from the plant becomes part of the fats an d proteins in the animal. Microorganisms and some animals feed on waste material from animals, and the rebrinys of dead animals and plants. The carbon then becomes part of these microorganisms and detritus feeders. Materials from living things decay because they are digested by microorganisms. This process happens faster in warm, moist conditions with plenty of oxygen. Decay can be very slow in cold, dry conditions, and when here is a shortfall of oxygen. Enzymes and digestion Enzymes are biological catalysts. There are optimum temperatures andpH values at which their activity is greatest. Enzymes are likewise proteins, and usually denatured above about 45? C. Enzymes are important in respiration. aerophilic respiration releases energy from glucose. What are enzymes? Enzymes are biological catalysts catalysts are substances that increase the rate of chemical reactions without world used up. Enzymes are alsoproteinsthat are folded into complex shapes that allow gnomisher molecu les to fit into them.The place where these substratemolecules fit is called theactive site. The pictures show how this works. In this example, two small molecules join together to make a larger one. If the shape of the enzyme changes, its active site may no longer work. We say the enzyme has beendenatured. They can be denatured by high temperatures or extremes ofpH. Note that it is wrong to say the enzyme has been killed. Although enzymes are made by living things, they are proteins, and not alive. Temperature and enzymes As the temperature increases, so does the rate of reaction. But very high temperatures denature enzymes.The graph shows the typical change in an enzymes activity with increasing temperature. The enzyme activity gradually increases with temperature until around 37? C, or corpse temperature. Then, as the temperature continues to rise, the rate of reaction falls quick, as heat energy denatures the enzyme. Temper-ature and enzyme activity PH and enzymes Changes in pH alter an enzymes shape. assorted enzymes work topper at different pH values. The optimum pH for an enzyme depends on where it normally works. For example, intestinal enzymes have an optimum pH of about 7. 5. Enzymes in the permit have an optimum pH of about 2. H and enzyme activity Enzymes and respiration Enzymes in cells turn photosynthesis, protein synthesis joining amino acids together, and aerobic respiration. Aerobic respiration Respiration is not the same thing as breathing. That is more neatly called ventilation. Instead, respiration is a chemical process in which energy is released from food substances, such as glucose a sugar. Aerobicrespiration needs oxygen to work. Most of the chemical reactions entangled in the process happen in tiny objects inside the cell cytoplasm, called mitochondria. This is the par for aerobic respirationGlucose + oxygen carbon dioxide + water (+ energy) The energy released by respiration is used to make large molecules from smaller ones. In plants, for example, sugars, nitrates and other nutrients are converted into amino acids. Amino acids can then join together to make proteins. The energy is also used * to allow ponderositys to contract in animals * to maintain a constant carcass temperature in birds and mammals Enzymes are important in digestion. Digestion is the breakdown of carbohydrates, proteins and fats into small soluble substances that can be absorbed into the profligate.Lipases and proteases are used in biological detergents, and enzymes are used in the manufacture of food and drink. The digestive system Digestion is the breakdown of large molecules into smaller, soluble molecules that can be absorbed into the dead body. Digestion happens inside the gut, and relies on enzymes. This diagram will show you of the main parts of the gut Enzymes and digestion The enzymes involved in respiration, photosynthesis and protein synthesis work inside cells. Other enzymes are spring upd by specialised cells and re leased from them the digestive enzymes are like this. They pass out into he gut, where they catalyse the breakdown of food molecules. Different enzymes Different enzymes catalyse different digestion reactions. Enzymes and their reactions catalysed enzyme reaction catalysed amylase starch sugars protease proteins amino acids lipase lipids fatty acids + glycerol Amylase is an example of a carbohydrase. Lipids are fats and oils. Different parts of the gut Different parts of the gut publish different enzymes. Where enzymes are produced enzyme where produced amylase spittlery glands, pancreas, small intestine protease stomach, pancreas, small intestine ipase pancreas, small intestine Summary Overall, this means that * Amylase catalyses the breakdown of starch into sugars in the mouth and small intestine. * Proteases catalyse the breakdown of proteins into amino acids in the stomach and small intestine. * Lipases catalyse the breakdown of fats and oils into fatty acids and glycerol i n the small intestine. Other substances in digestion You should recall that different enzymes work best at different pH values. The digestive enzymes are a good example of this. Enzymes in the stomach The stomach produceshydrochloric acid.This helps to begin digestion, and it kills more harmful microorganisms that might have been swallowed along with the food. The enzymes in the stomach work best inacidicconditions in other words, at a low pH. Enzymes in the small intestine After the stomach, food travels to the small intestine. The enzymes in the small intestine work best inalka-lineconditions, but the food is acidic after being in the stomach. A substance called insolenceneutralises the acid to provide the alkaline conditions needed in the small intestine. Bile and enzyme production in the coloured and pancreas Enzymes in industry Enzyme namesThe names of the different character references of enzymes usually end in the letters-ASE. Three of the most common enzymes with their chemical actions are * lipase breaks down fats * protease breaks down proteins * carbohydrase breaks down carbohydrates Enzyme uses Enzymes allow certain industrial processes to be carried out at normal temperatures and pressures, thereby reducing the amount of energy and expensive equipment needed. Enzymes are also used in the home, for example, in biological detergents. The table shows some common enzyme uses you should be familiar with. characters of enzymes Enzyme Use rotease used to pre-digest proteins during the manufacture of baby foods lipase used together with protease in biological detergents to break down digest the substances in stains into smaller, water soluble substances carbohydrase used to convert starch syrup, which is relatively cheap, into sugar syrup, which is more valuable for example, as an ingredient in sports drinks isomerase used to convert glucose syrup into laevulose syrup fructose is sweeter than glucose, so it can be used in smaller amounts in s limming foods Homeostasis The conditions inside the body must be controlled within narrow limits.This is called homeostasis. These conditions hold water content, ion content, body temperature and blood glucose concentration. The thermoregulatory centre is the part of the witticism that monitors and controls body temperature. The pancreas meanwhile monitors and controls blood glucose concentration. It produces a hormone called insulin that reduces blood glucose levels. Diabetes is a disease which can be caused by insufficient insulin. Removing waste products Waste products must be removed from the body. If they are not, they will increase in concentration and may interfere with chemical reactions or pervert cells.Waste products that must be removed include carbon dioxide and urea. Waste product Why is it produced? How is it removed? carbon dioxide it is a product of aerobic respiration through the lungs when we breathe out urea it is produced in the liver when dissipation ami no acids are broken down the kidneys remove it from the blood and make urine, which is stored in the bladder temporarily Production and remotion of waste products Water enters the body through food and drink. It is also a product of aerobic respiration in cells. If the amount of water in the body is wrong, cells can be damaged because too oft water enters or leaves them.The pictures show how the amount of water lost as urine is controlled Controlling blood glucose The pancreas and insulin Thepancreasmonitors and controls the concentration ofglucosein the blood. It produces a hormone calledinsulin. Insulin causes glucose to move from the blood into cells. It lowers the blood glucose concentration if it has become too high. This can happen after eating a meal that is rich in carbohydrates (for example, sweets, potatoes, bread, rice or pasta). The pictures show how this works. Diabetes Diabetes is a disease where the concentration ofglucosein the blood is not controlled properly by th e body.Intype 1 diabetes, thepancreasdoes not produce eno-ughinsulin. This can black market to high levels of glucose in the blood, which can be fatal. Types of Diabetes There are two types of treatment for diabetes * Careful monitoring of food intake, with particular care taken oer carbohydrates which are digested into glucose. * Injecting insulin into the blood before meals. The extra insulin causes glucose to be taken up by the liver and other tissues. Cells get the glucose they need for respiration, and the blood glucose concentration stays normal. Temperature regulation human raceenzymeswork best at 37?C, so the bodys temperature is controlled. A part of the brain called thethermoregulatory centremonitors and controls body temperature. It gathers information as warmness impulses fromtemperature receptorsin * the brain these are sensitive to the temperature of the blood flowing there * the unclothe these are sensitive to skin temperature egesting Sweating is one way to h elp cool the body. We parturiency more in hot conditions, so more water is lost from the body. This water must be replaced through food or drink to maintain the balance of water in the body. Ions such as sodium ions and chloride ions are also lost when we sweat.They must be replaced through food and drink. If the bodys ion content is wrong, cells can be damaged. Temperature regulation higher If you become too hot or too cold, there are several(prenominal) ways in which your temperature can be controlled. They involve sweating, shivering, skin capillaries and hairs. also hot When we get too hot * Sweat glands in the skin release more sweat. This evaporates, removing heat energy from the skin. * snag vessels leading to the skin capillaries become wider theydilate allowing more blood to flow through the skin, and more heat to be lost. in addition cold When we get too cold * Muscles contract rapidly we shiver.These contractions need energy from respiration, and some of this is re leased as heat. * Blood vessels leading to the skin capillaries become narrower theyconstrict- letting less blood flow through the skin and conserving heat in the body. The hairs on the skin also help to control body temperature. They lie flat when we are warm, and rise when we are cold. The hairs trap a layer of air above the skin, which helps to insulate the skin against heat loss. Controlling temperature Too cold Too hot A Hair muscles pull hairs on end. B Erect hairs trap air. C Blood flow in capillaries decreases. D Hair muscles relax.Hairs lie flat so heat can escape. E Sweat secreted by sweat glands. Cools skin by evaporation. F Blood flow in capillaries increases. Remember Capillaries do not move up and down inside the skin. Temperature is regulated by controlling the amount of blood which flows through the capillaries. Hormones Hormones are chemical substances that help to regulate processes in the body. Hormones are secreted by glands and travel to their manoeuver or gans in the bloodstream. Several hormones are involved in the female menstrual cycle. Hormones can be used to control human fertility and have advantages and disadvantages. Hormones and glandsHormones arechemicals secreted by glandsin the body. Different hormones affect different target organs. The bloodstream transports hormones from the glands to the target organs. Hormones regulate the functions of umteen cells and organs The target organ and cause of glands and hormones Gland Hormone Target organs Effect adrenal gland adrenalin vital organs, e. g. liver and heart Prepares body for action fight or flight. ovary oestrogen ovaries, womb, pituitary body body gland Controls puberty and the menstrual cycle in females stimulates production of LH and suppresses the production of FSH in the pituitary gland. ovary progesterone uterus Maintains the lining of the womb suppresses FSH production in the pituitary gland. pancreas insulin liver Controls blood sugar levels. pituitary glan d anti-diuretic hormone (ADH) kidney Controls blood water level by triggering uptake of water in kidneys. pituitary gland follicle stimulating hormone (FSH) ovaries Triggers egg ripening and oestrogen production in ovaries. pituitary gland luteinising hormone (LH) ovaries Triggers egg release and progesterone production in ovaries. testes testosterone male reproductive organs Controls puberty in males. Hormones in the menstrual cycle The menstrual cycle in women is a recurring process in which the lining of the uterus womb is prepared for pregnancy, and if pregnancy does not happen, the lining is shed at menstruation. Severalhormonescontrol this cycle, which includes controlling the release of an egg each month from an ovary, and changing the thickness of the uterus lining. These hormones are secreted by the ovaries and pituitary gland. FSH The hormone FSH is secreted by the pituitary gland. FSH makes two things happen 1. it causes an egg to mature in an ovary 2. it stimulates the ovaries to release the hormone oestrogen OestrogenThe hormone oestrogen is secreted by the ovaries. Oestrogen makes two things happen 1. it stops FSH being produced so that only one egg matures in a cycle 2. it stimulates the pituitary gland to release the hormone LH LH The hormone LH causes the mature egg to be released from the ovary. This image shows how the level of oestrogen changes during the menstrual cycle. Progesterone is some other hormone secreted by ovaries it maintains the lining of the uterus and stays high during pregnancy. Hormone levels during the menstrual cycle Controlling fertility Human fertility is controlled byhormones.This means that knowledge of hormones can be used to mold to increase, or reduce, the chances of fertilisation and pregnancy. Oral contraceptives Contraceptive pills The oral contraceptive, the pill, greatly reduces the chances of mature testis being produced. The pill contains oestrogen, or oestrogen and progesterone. These hormones inh ibit the production of FSH, which in turn stops eggs maturing in the ovaries. swanness treatment Some women have difficulty becoming pregnant because they dont produce enough FSH to allow their eggs to mature. Fertility drugs contain FSH, which stimulates eggs to mature in the ovary. The nervous systemThe nervous system allows the body to respond to changes in the environment. This is a process usually coordinated by the brain. reflex actions are extra-rapid responses tostimuli, and this process also involves the nervous system, but bypasses the brain. Receptors and effectors Receptors Receptors are groups of specialised cells. They can detect changes in the environment, which are calledstimuli, and turn them into electrical impulses. Receptors are often located in thesense organs, such as the ear, eye and skin. Each organ has receptors sensitive to particular kinds of stimulus. Receptors sense organs receptors sensitive toSkin touch, pressure, pain and temperature Tongue chemica ls in food Nose chemicals in the air Eyes light Ears sound and position of the head The of import nervous system CNS in humans consists of the brain and spinal cord. When a receptor is stimulated, it sends a point out along the nerve cells nerve celles to the brain. The brain, then co-ordinates the response. Effectors An effector is any part of the body that produces the response. Here are some examples of effectors * a muscle contracting to move the arm * a muscle squeezing saliva from the salivary gland * a gland releasing ahormoneinto the blood NeuronesNeurones are nerve cells. They carry information as tiny electrical signals. There arethree different types of neurones, each with a slightly different function. 1. Sensory neuronscarry signals fromreceptorsto the spinal cord and brain. 2. Relay neuronscarry messages from one part of theCNSto another. 3. Motor neuronscarry signals from theCNSto effectors. The diagram below shows a typical neuron in this case, a motor neuron. It has tiny branches at each end and a long persona carries the signals. A motor neuron Synapses Where two neurones meet, there is a tiny gap called a synapse. Signals cross this gap using chemicals.One neurone releases the chemical into the gap. The chemical diffuses across the gap and makes the next neurone transmit an electrical signal. Reflex actions When a receptor is stimulated, itsends a signal to the central nervous system, where the brain co-ordinates the response. But sometimesa very quick response is needed, one that does not need the involvement of the brain. This is a reflex action. Reflex actions are rapid and happen without us thinking. For example, you would pull your hand away from a hot scorch without thinking about it. The animation below allows you to step through each stage of the reflex arc.This is what happens 1. receptor detects a stimulus change in the environment 2. sensory neurone sends signal to relay neurone 3. motor neurone sends signal to effector 4. effector produces a response The way the iris in our eye adjusts the size of the savant in response to bright or dim light is also a reflex action. Inbrightlight * Radial muscles of the iris relax. * Circular muscles of the iris contract. * Less light enters the eye through the contracted pupil. Indimlight * Radial muscles of the iris contract. * Circular muscles of the iris relax. * More light enters the eye through the dilated pupil.Defending against infection Pathogens are microorganisms such as bacteria and viruses that cause disease. bacterium release toxins, and viruses damage our cells. White blood cells can acquire and destroy pathogens. They can produce antibodies to destroy pathogens, and antitoxins to rot toxins. In vaccination pathogens are introduced into the body in a weakened form. The process causes the body to produce enough white blood cells to protect itself against the pathogens, while not getting diseased. Antibiotics are effective against bacteria, but not against viruses. Some strains of bacteria are resistant to antibiotics.Pathogens bacteria Pathogens aremicroorganismsthat cause infectious disease. Bacteria and viruses are the main pathogens. Bacteria Bacteria aremicroscopic organ-isms. They come in many shapes and sizes, but even the largest are only 10 micrometres long 10 millionths of a metre. Bacteria areliving cellsand, in favourable conditions, can multiply rapidly. Once inside the body, they release poisons or toxins that make us feel ill. Diseases caused by bacteria include- -food poisoning -cholera -typhoid -whooping cough -gonorrhoea a sexually transmitted disease Pathogens viruses Viruses are many times smaller thanbacteria.They are among the smallest organisms known and consist of a fragment of genetic material inside a protective protein coat. Viruses can only reproduceinside host cells, and they damage the cell when they do this. A virus can get inside a cell and, once there, take over and make hundreds of th ousands of copies of itself. Eventually the virus copies fill the whole host cell and destroy it open. The viruses are then passed out in the bloodstream, the airways, or by other routes. Diseases caused by viruses include * flu flu * colds * measles * mumps * rubella * chicken pox * AIDS White blood cellsThe body has different ways of protecting itself againstpathogens. The first defence is passive immunity. This is aimed at stopping the pathogen getting into the body in the first place. The bodys passive immunity system includes the skin,mucusandciliain the respiratory system, acid in the stomach, and enzymesin tears. If a pathogen still manages to get into the body, the second defence takes over. This is calledactive immunity, and the white blood cells have key functions in this. Functions of the white blood cells White blood cells can * ingest pathogens and destroy them * produce antibodies to destroy pathogens produce antitoxins that neutralise the toxins released by pathoge ns In a written examination, it is slow to get carried away and waffle on about things such as invaders and battles, but follow to the point. Note that * the pathogens are not the disease they cause the disease * white blood cells do not eat the pathogens they ingest them * antibodies and antitoxins are not living things they are specialised proteins More about white blood cells There are several different types of white blood cells, each with different functions, but they can be put into two main groups * phagocytes or macrophages lymphocytes Phagocytes Phagocytes can easily pass through blood vessel walls into the surrounding tissue and move towardspathogensor toxins. They then either * ingest and absorb the pathogens or toxins * release an enzyme to destroy them Having absorbed a pathogen, the phagocytes may also send out chemical messages that help nearby lymphocytes to identify the type of antibody needed to neutralise them. Lymphocytes Pathogens contain certain chemicals that are foreign to the body and are called antigens. Each lymphocyte carries a specific type of antibody a protein that has a chemical fit to a certain antigen.When a lymphocyte with the appropriate antibody meets the antigen, the lymphocyte reproduces quickly, and makes many copies of the antibody that neutralises the pathogen. Antibodies neutralise pathogens in a number of ways * they bind to pathogens and damage or destroy them * they coat pathogens, clumping them together so that they are easily ingested by phagocytes * they bind to the pathogens and release chemical signals to attract more phagocytes Lymphocytes may also release antitoxins that stick to the appropriate toxin and stop it damaging the body. Vaccination People can be immunised against a pathogen through vaccination.Different vaccinums are needed for diffe-rentpathogens. Vaccination involves putting a small amount of an inactive form of a pathogen, or dead pathogen, into the body. Vaccines can contain * live pat hogens treated to make them harmless * harmless fragments of the pathogen * toxinsproduced by pathogens * dead pathogens These all act as antigens. When injected into the body, they stimulate white blood cells to produce antibodies against the pathogen. Because the vaccine contains only a weakened or harmless version of a pathogen, the vaccinated person is not in danger of exploitation disease although some people may uffer a mild reaction. If the person does get infected by the pathogen later, the required lymphocytes are able to reproduce rapidly and destroy it. Vaccines and boosters Vaccines in aboriginal childhood can give protection against many serious diseases. Sometimes more than one vaccine is given at a time, like the MMR triple vaccine against mumps, measles and rubella. Sometimes vaccine boosters are needed, because the immune response memory weakens over time. Anti-tetanus injections may need to be repeated every ten years. Antibiotics Antibiotics are substances that killbacteriaor stop their growth.They do not work againstviruses it is difficult to develop drugs that kill viruses without also damaging the bodys tissues. How some common antibiotics work antibiotic how it works penicillin breaks down cell walls erythromycin stops protein synthesis neomycin stops protein synthesis vancomycin stops protein synthesis ciprofloxacin stops DNA replication Penicillin The first antibiotic penicillin was discovered in 1928 by black lovage Fleming. He noticed that some bacteria he had left in a petri dish had been killed by of course occurring penicillium mould.Since the discovery of penicillin, many other antibiotics have been discovered or developed. Most antibiotics used in medicine have been altered chemically to make them more effective and safer for humans. Resistance bacterial strains can develop resistance to antibiotics. This happens because of congenital weft. In a large population ofbacteria, there may be some cells that are not affected by the antibiotic. These cells survive and reproduce, producing even more bacteria that are not affected by the antibiotic. MRSA is methicillin-resistant staphylococcus aureus.It is very dangerous because it is resistant to most antibiotics. It is important to avoid over-use of antibiotics, so we can slow down, or stop, the development of other strains of resistant bacteria. Cleanliness One elementary way to reduce the risk of infection is to maintain personal hygiene and to keep hospitals clean. Diet and Exercise Regular feat and a balanced diet are needed to keep the body healthy. Too little food leads to a person being underweight and prone to illness, while too frequently food and not enough exercise leads to a person being overweight and prone to other illnesses.Excess cholesterol increases the risk of heart disease, and excess salt causes high blood pressure and increases the risk of heart disease and stroke. Nutrients A mixture of different types of food in the level amou nts is needed to maintain health. The main food groups are The main food groups food group found in required by our bodies for potatoes, pasta, bread, bananas, sugar and rice A source ofenergyfor other life processes. Sometimes referred to as eccentric, which is actually just one very common type of carbohydrate. cheese, butter, margarine and oils Fats are needed to make cell membranes and toinsulateour bodies.They also contain important fat-solublevitamins. meat, fish, eggs and cheese Growth and repair. whole meal bread, fruit, vegetables and pulses The fibre or roughage in our diet is not digested, but is important because it allows the muscles in our intestines to move food through our system byperistalsis. Metabolic rate A healthy diet contains all the different nutrients in the correct amounts, and provides the right amount of energy for each individual. An unbalanced diet can lead to a person becoming malnourished. They may be too thin or too fat as a result, and th ey may suffer from deficiency diseases.Chemical reactions Respiration is the chemical reaction that allows cells to release energy from food. The metabolic rate is the speed at which such chemical reactions take place in the body. It varies because of several factors, including * age * gender male or female * the proportion of muscle to fat in the body * the amount of exercise and other physical activity * genetic traits The metabolic rate increases as we exercise and stays high for a while afterwards. The right amount of food Not enough food If you dont eat enough food, you will become too thin and may suffer from health problems.These include * irregular periods in women * reduced resistance to infection * deficiency diseases Deficiency diseases includerickets which affects proper growth of the skeleton and is caused by insufficient vitamin D andkwashiorkor which causes a swollen abdomen and is a result of insufficient protein. Problems such as these are more likely to affect pe ople in the developing world, where it can be more difficult to get enough food. Too much food In warm weather, or when you dont do much exercise, you do not need to eat as much food as when it is cold or when you have exerted yourself physically.If you eat too much food without fetching enough exercise, you will become overweight. Very fat people are described asobese. sonorous people may suffer from health problems, including * diabetes an illness in which the body is unable to control the amount of sugar in the blood * arthritis an illness in which the joints become worn, inflamed and painful * high blood pressure * heart disease The heart The heart is an organ that needs its own supply of blood to keep it working. If the blood supply is reduced, the heart muscle will not work properly and will become weaker.A heart attack happens when part of the heart does not get any blood because of a blocked artery. Cholesterol Cholesterol is a substance found in the blood. It is made in t he liver and is needed for healthy cell membranes. However, too much cholesterol in the blood increases the risk of heart disease, and of diseased arteries. Good and bad cholesterol The bloodstream transports cholesterol around the body attached toproteins. The combining of cholesterol and protein is calledlipoprotein, and there are two types. 1. Low-density lipoproteins LDLs carry cholesterol from the liver to the cells. 2.High-density lipoproteins HDLs carry excess cholesterol back to the liver. LDLs are often called bad cholesterol because they lead to fat grammatical construction up on artery walls, which causes heart disease. HDLs are often called good cholesterol because they help to stop fat building up in the arteries. Improving the balance A high proportion of HDLs to LDLs is good for a healthy heart. Monounsaturated and polyunsaturated oils as found in vegetable oils help to reduce cholesterol levels in the blood, and also increase the proportion of HDLs compared with LDLs. Check your understanding of such oils by looking atVegetable oils.There are also drugs that can improve high blood pressure and high cholesterol levels. salinity shelve salt is sodium chloride. Too much salt in the diet can lead tohigh blood pressure, which in turn leads to an increased risk of heart disease and strokes. Salt isfound congenitally in many kinds of food, but more is added by food manufacturers and many people add even more when they are eating. Processed foods often have a high proportion of salt and fat. Salt added to food during processing accounts for about two-thirds of the average salt intake. Adaptation Adaptations cold climatesEvery organism has certain features or characteristics that allow it to live successfully in itshabitat. These features are called adaptations, and we say that the organism is adapted to its habitat. Organisms living in different habitats need different adaptations. The polar bear Polar bears are well adapted for survival in th e Arctic. They have * a white appearance, as camouflage from prey on the snow and ice * thick layers of fat and fur, for insulation against the cold * a small surface area to volume ratio, to downplay heat loss * a gr voiced coat, which sheds water after swimmingThe snowshoe lapin The snowshoe hare has white fur in the winter and reddish-brown fur in the summer. This means that it is camouflaged from itspredatorsfor most of the year. Arctic plants The Arctic is cold and windy with very little rainfall. Plants in the Arctic often grow very close to the ground and have small leaves. This helps to conserve water and to avoid damage by the wind. Adaptations hot climates The camel Camels live in deserts that are hot and dry during the day, but cold at night. They are well adapted for survival in the desert.Camels have * Large, flat feetto spread their weight on the sand. * Thick furon the top of the body for shade, and thin fur elsewhere to allow easy heat loss. * A large surface area to volume ratioto maximise heat loss. * The baron to go for a long time without water(they dont store water in their humps, but they lose very little through urination and sweating). * The ability totolerate body temperaturesup to 42C. * Slit-like nostrils and two rows of eyelashesto help keep the sand out. Desert plants Cacti are well adapted for survival in the desert. They have * Stems that can store water. Widespread root systems that can collect water from a large area. In addition,cacti have spines instead of leaves. These minimise the surface area and so reduce water loss bytranspiration. The spines also protect the cacti from animals that might eat them. Other adaptations Animals and plants may have specific features that adapt them to their environment. These include barbs and spines, poisons and warning colours that deter predators and herbivores. Some harmless species may even resemble a poisonous or dangerous species to increase their chances of survival. Characteristi cs and salmagundi genetical information from one species can be transferred to another species using genetic engineering. discriminating breeding, also called artificial endurance, involves people taking charge of selection to produce new varieties of various species. A mix is a type of a particular species that is different in some clear way from other varieties of that species. The characteristics of a species can be used to classify the species. This is sometimes difficult to do. Genetic engineering Genetic engineering is also called genetic modification (orGM). It is not the same as cloning.Although cloning techniques are used in genetic engineering, the two things should not be confused. The table shows some of the differences. Cloning Genetic engineering Produces exact copies. Produces a unique set of genes. Genes copied within the same species. Genes can be swapped across species. Selective breeding Natural selection Species gradually evolve by a process of natural se lection. The individuals in any population with the inherited features best suited to the environment in which they live are most likely to survive and reproduce. When they do, they pass on the genetic information for these features to their offspring.Over time, a species can change its appearance and may even become a new species, unable to reproduce successfully with individuals of the original species. Artificial selection Selective breeding, also called artificial selection, involves people taking charge of selection to produce new varieties of various species. A variety is a type of a particular species that is different in some clear way from other varieties of that species. For example, pedigree dogs come in piles of different varieties (or breeds) they may be different colours and sizes, but they are all still dogs.Suppose you wanted a variety of cow that produced a lot of milk. This is what you could do * choose or select the cows in your flock that produce the most milk * only let these cows reproduce * select the offspring that produce the most milk * only let these offspring reproduce * keep repeating the process of selection and breeding until you achieve your destination The key here is to identify the feature you want, and only breed from the individuals that have that feature. Here are some examples of what selective breeding can produce * hens that lay big eggs of a particular colour cattle that produce lots of meat * tomato plants that produce lots of tomatoes * crops that are resistant to certain plant diseases Changing the characteristics of a species The characteristics of a species can be changed by * natural selection * selective breeding * genetic engineering. The table shows some differences between these. Natural selection Selective breeding Genetic engineering Number of generations needed for change very many many one Human intervention not needed needed needed Desired outcome known? no yes yes New species formed? yes no noNot es This is the mechanism of change in Darwins theory of phylogenesis This is how new varieties or breeds are usually produced Genetic information can come from the same species or from a different one In selective breeding and genetic engineering, there is a goal or desired outcome. For example, we may wish to produce a variety of cow capable of producing a lot of milk, or a bacterium capable of producing insulin. There is no goal in natural selection although we find that particular species are well adapted to their environments, natural selection does not know what the species should be like.Individuals that are better suited to their environment are more likely to survive to reproduce, and so pass on their characteristics to the next generation, than those that are poorly suited. Classification You will remember from your Key Stage 3 studies that species with similar characteristics are put into groups, and that this is called classification. Remind yourself of the basics of clas sification by lookinghere. Kingdoms The first rank in this system is called a kingdom. There are five kingdoms, based upon what an organisms cells are like 1. nimals (all multicellular animals) 2. plants (all green plants) 3. fungi (moulds, mushrooms, yeast) 4. prokaryotes (bacteria, blue-green algae) 5. protoctists (Amoeba, Paramecium) Further divisions There are several further ranks before we reach a particular species. In order, these are * kingdom * phylum * class * order * family * genus * species For example,lionshave the following classification * kingdom animal * phylum vertebrate * class mammal * order carniverous * family cat * genus big cat * species lion Difficulties with classificationIt can beeasyto classify a species. For example, we areHomo sapiens. Classification of species rank classification notes kingdom animals phylum chordates animals with backbones class mammals animals that are warm-blooded, have lungs and body hair, produce milk and give birth to li ve young order primates ape-like animals family hominids human-like animals genus homo humans species sapiens modern humans It can also bedifficultto classify a certain organism. For example, the single-celled organism called Euglena has some confusing characteristics.It has * chloroplasts, like a plant * no cell wall, like an animal * a flagellum to swim with, like some bacteria A fifth kingdom, called the protoctists, was made for organisms like Euglena. The Heart The heart requires its own constant blood supply in order to keep beating and this is delivered through the coronary arteries. Genetic and modus vivendi factors can lead to the coronary arteries becoming blocked, and an increased risk of heart disease. The circulatory system Blood carries oxygen and nutrients to the bodyscells, and waste products away from them.The circulatory system consists of * the heart, which is the muscular pump that keeps the blood moving * the arteries, which carry blood away from the heart * the veins, which return blood to the heart * the capillaries, which are tiny blood vessels that are close to the bodys cells The diagram outlines the circu-latory system. To make things clear, oxygenated blood is shown in red, and deoxygenated blood in blue. Arteries and veins The arteries carry blood from the heart, while veins return blood to it. With both, their structure is related to their function. ArteriesBlood in the arteries is under high pressure generated by the heart. The arteries have * thick outer walls * thick layers of muscle and elastic fibres Veins The blood in veins is under lower pressure than the blood in arteries. The veins have * thin walls * thin layers of muscle and elastic fibres Unlike arteries, veins have one-way valves in them to keep the blood moving in the correct direction. The heart The heart is a muscular organ. It keeps beating at about 70 times per minute. You can see how it pumps the blood to the lungs and the rest of the body by studying this anima tion.The muscle cells in the heart need a constant supply of oxygen and nutrients, and for their waste products to be removed. So the heart requires its own blood supply in order to keep beating. Blood vessels called thecoronary arteriessupply blood to the heart muscles. If they become blocked, aheart attackcan happen. Heart attacks A heart attack can happen because 1. Fatty deposits build up in the coronary arteries. 2. A blood clot can form on a fatty deposit. 3. The blood clot can block a coronary artery. 4. Some heart muscle cells do not get the oxygen and nutrients they need. 5. These cells start to die.Causes of heart disease Heart disease is not usually caused by micro-organisms. It is caused by * genetic factors, which show as a family archives of heart disease * lifestyle factors Heart disease is more common in the UK than in non-industrialised countries, and many other indust-rialised nations. This is due to lifestyle factorsincluding * smoking * lack of regular exercise * stress leading to a fast heart rate * drinking a lot of alcohol * poor diet A lack of exercise and a diet that is high in salt and saturated fat cause people to * become overweight * have high blood pressure have high levels of cholesterol in their blood These factors contribute to an increased risk of heart disease. Extra Sex hormones Changes occur at puberty because of sex hormones produced by the testes in boys, and the ovaries in girls. Some changes happen to everyone, both boys and girls, while others happen in one sex only. Here are some changes that happen to both boys and girls * pubic hair grows * underarm hair grows Here are some changes that happen to boys only * voice breaks gets deeper * hair grows on face and body * body becomes more muscular * testes and penis get bigger testes start to produce sperm cells Here are some changes that happen to girls only * hips get wider * breasts develop * ovaries start to release egg cells periods start Fertility in humans can be controlled by the artificial use of sex hormones, including contraceptive pills and fertility drugs. Competition Different species struggle to survive and breed. The size of a predator population depends on the size of the prey population, and the reverse is true as well. Mutualism benefits both species involved in the relationship, but parasitism only benefits the parasite, not the host.Habitats have limited amounts of the resources needed by living organisms. Organisms mustcompetewith others in order to get enough of these resources to survive. If they are unsuccessful and cannot move to another habitat, they will die. Animals Some of the resources that animals compete for * food * water * space Animals may also compete for mates so that they can reproduce. Plants Remember that plants make their own food usingphoto-synthesis, so they do not compete for food. Here are some of the things that plants do compete for * light * water space * mineral salts Human beings Human beings are very successful organisms. We compete with animals for food resources, and we compete with both animals and plants for space and water. The northward cycle Seventy-nine per cent of the air around us is nitrogen. Living things need nitrogen to make proteins, but they cannot get it directly from the air because nitrogen gas is tooun oxidizableto be used to make new compounds within an organism. Plants can take up and use nitrogen when it is in a morereactiveform for example, innitratesorammonium salts.Changing nitrogen into a more reactive substance is callednitrogen recompenseation. Nitrogen fixation Nitrogen fixation happens in three different ways The energy in a lightning bolt can split nitrogen molecules in the air, allowing each nitrogen atom toreactwith oxygen to formnitrogen oxides. The rain washes these oxides to the ground, where they formnitrates. * The Haber Processis used by industry to produce ammonia from nitrogen. Ammonia is then used to make the fertiliser that far mers spread on the soil to feed their crops. Nitrogen-fixing bacteria found in both the soil and root nodules of leguminous plants fix nitrogen into a form that can be used by plants. When plants are eaten by animals, the nitrogen compounds are passed on. Nitrogen compounds are returned to the soil by excretion and egestion from animals, or when plants and animals die and decay. The nitrogen compounds returned in this way arechanged backto nitrogen gas by denitrifying bacteria which live in the soil. Thiscompletes the cycle, so that the percentage of nitrogen in the air remains constant. The nitrogen cycle