CIE IGCSE Biology Notes PDF

 TABLE OF CONTENTS 3 CHAPTER 1 Characteristic & Classification of Living Organisms 4 CHAPTER 2 Organization of the Organism 5 CHAPTER 3 Movement In and Out of Cells 6 CHAPTER 4 Biological Molecules 6 CHAPTER 5...

 TABLE OF CONTENTS 3 CHAPTER 1 Characteristic & Classification of Living Organisms 4 CHAPTER 2 Organization of the Organism 5 CHAPTER 3 Movement In and Out of Cells 6 CHAPTER 4 Biological Molecules 6 CHAPTER 5 Enzymes 7 CHAPTER 6 Plant Nutrition 9 CHAPTER 7 Human Nutrition 11 CHAPTER 8 Transport in Plants 12 CHAPTER 9 Transport in Animals 14 CHAPTER 10 Diseases & Immunity  CIE IGCSE BIOLOGY//0610 15 CHAPTER 11 Gas Exchange in Humans 16 CHAPTER 12 Respiration 16 CHAPTER 13 Excretion in Humans 17 CHAPTER 14 Coordination & Response 21 Drugs CHAPTER 15 22 CHAPTER 16 Reproduction 27 CHAPTER 17 Inheritance 28 Variation & Selection CHAPTER 18 29 CHAPTER 19 Organisms & their Environment 31 Biotechnology & Genetic Engineering CHAPTER 20 33 Human Influences on Ecosystems CHAPTER 21 PAGE 2 OF 35  CIE IGCSE BIOLOGY//0610  DNA is the chemical from which chromosomes are made 1. CHARACTERISTICS AND CLASSIFICATION OF  Each DNA molecule is made up of strings of smaller LIVING ORGANISMS molecules containing four bases  Biologists compare the sequences of the bases in the 1.1 Characteristics of Living Organisms DNA of organisms from two different species  Movement: action by an organism or part of an  The more similar the base sequence, the more closely organism causing a change of position or place related the species are to one another  Respiration: the chemical reactions that break down  Organisms which share a more recent ancestor have nutrient molecules in living cells to release energy base sequences in DNA that are more similar than those  Sensitivity: ability to detect or sense changes in the that share only a distant ancestor environment (stimuli) and to make responses  The sequences of bases in DNA and of amino acids in  Growth: permanent increase in size and dry mass by an proteins are used as a more accurate means of increase in cell number or cell size or both classification (cladistics)  Reproduction: processes that make more of the same kind of organism 1.3 Kingdoms  Excretion: removal from organisms of toxic materials,  Animal: Multi-cellular ingestive heterotrophs (eat living the waste products of metabolism (chemical reactions in organisms) cells including respiration) and substances in excess of  Plant: Multi-cellular photosynthetic autotrophic (make requirements their own food) organism with a cellulose cell wall.  Nutrition: taking in of nutrients which are organic  Fungi: Single celled or multi cellular heterotrophic substances and mineral ions, containing raw materials or organism with cell wall not made of cellulose, spread by energy for growth and tissue repair, absorbing and spreading of spores in moist/dark/warm environment, assimilating them saprotrophs (feed off dead organisms) or parasites  Prokaryotes: Single celled organism with no true nucleus 1.2 Concept & Use of a Classification System  Protocist: Single celled organism with a nucleus  Organisms can be classified into groups by the features that they share 1.4 Vertebrates  Classification systems aim to reflect evolutionary MR FAB relationships (change of adaptive features of a  Mammals population over time, as a result of natural selection) o Fur/hair on skin  Species: organisms which can reproduce successfully o Can live on land and in water  Classification is traditionally based on studies of o 4 legs morphology and anatomy o Lungs to breathe  Morphology: the overall form and shape of their bodies o Give birth to live young e.g. wings or legs  Reptiles: o Scales on skin  Anatomy: the detailed body structure determined by o Usually 4 legs dissection o Lungs to breathe  Binomial system: a system of naming species in which o Hard eggs the scientific name of an organism is made up of two  Fish: parts showing the genus (starting with a capitol letter) o Wet scales and species (starting with a lower case letter), written in o External fertilization and soft eggs italics when printed (therefore underlined when written) o Gills to breathe e.g. Homo sapiens  Amphibians: o Smooth, moist skin KING PHILIP CAME OVER FOR GOOD SPAGHETTI o External fertilization and soft eggs  Kingdom, Phylum, Class, Order, Family, Genus, Species o Gills/lungs to breathe so can live on land and in water o 4 legs  Kingdom  Species = Similarity increases PAGE 3 OF 35  CIE IGCSE BIOLOGY//0610  Birds 1.7 Viruses and Bacteria o Feathers on body and scales on legs VIRUS BACTERIA o Have 2 legs and 2 wings COVERED BY Protein coat Cell wall o Lungs to breathe CELL o Hard eggs No Yes MEMBRANE 1.5 Arthropods (Invertebrates with Legs) CYTOPLASM No Yes CAMI GENETIC DNA or RNA – DNA – enough for  Crustaceans: (e.g. crabs) MATERIAL only a few genes several 100 genes o Have an exoskeleton LIVING OR Non-living unless Living o 1 pair of compound eyes NOT? in host o 2 body segment – cephalothorax and abdomen  Two examples of virus structure o More than four pairs of legs o 2 pairs of antennae sensitive to touch and chemicals  Arachnids: (e.g. spiders) o 2 body segment – cephalothorax and abdomen o Four pairs of legs o Pair of chelicerae to hold prey o Two pedipalps for reproduction o Simple eyes  Myriapods: (e.g. centipede) o Segmented body o Additional segments formed 1.8 Dichotomous Keys o One pair of antennae  Dichotomous key: uses visible features to classify o 70+ pairs of legs – 1 or 2 pairs on each segment organisms. It is which gives you a choice of two features o Fused head and thorax and segmented abdomen and you follow the one that applies: each choice leads o Simple eyes to another choice until the organism is narrowed down  Insects: (e.g. bees) to its genus and finally species. o 3 body segments – head, thorax and abdomen o 3 pairs of legs 2. ORGANIZATION OF THE ORGANISM o 1 pair of antennae o 1 or 2 pairs of wings 2.1 Cell structure and Organization o Compound and simple eyes  All living things are made of cells. 1.6 Classifying Plants  All typical cells have: o Cell membrane: differentially or partially permeable  Ferns: to allow certain substances to enter and leave the cell. o Do not produce flowers o Cytoplasm: where chemical reactions take place o They are plants with roots, stems and leaves o Nucleus: contains DNA and controls the cell o Have leaves called fronds o Mitochondria: organelle where aerobic respiration o Reproduce by spores happens  Flowering plants: o Ribosome: makes protein and can be found floating o They are plants with roots, stems and leaves within the cytoplasm o Reproduce sexually by means of flowers and seeds  A typical animal cell (e.g. the liver cell) has all above o Seeds are produced inside the ovary in the flower  Only plant cells have: Monocotyledons Dicotyledons o Vacuole: stores food & water & helps to maintain  One cotyledon  Two cotyledons shape of cell  Parallel veins  Veins netlike o Cell wall: rigid to keep shape of cell o Chloroplasts: contain chlorophyll, which absorbs light  Fibrous root  Taproot present energy for photosynthesis  Floral parts in 3s  Floral parts in 4s or 5s PAGE 4 OF 35  CIE IGCSE BIOLOGY//0610  A typical plant cell (e.g. the palisade cell) has all the  Organelle: a specialized part of a cell that has its own above things. function, e.g. the nucleus  Cell: the smallest part of a living structure that can operate as an independent unit e.g. red blood cell  Tissue: a group of cells with similar structures, working together to perform a shared function e.g. muscle tissue  Organ: a structure made up of a group of tissues, working together to perform specific functions e.g. heart  Organ system: group of organs with related functions, working together to perform body functions e.g. 2.2 Levels of Organization respiratory system CELL FUNCTION ADAPTATION(S) DIAGRAM 2.3 Size of Specimens  Biconcave 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑑𝑟𝑎𝑤𝑖𝑛𝑔 𝑖𝑚𝑎𝑔𝑒 𝐼 shape 𝑀𝑎𝑔𝑛𝑖𝑓𝑖𝑐𝑎𝑡𝑖𝑜𝑛 = = = RED 𝑠𝑖𝑧𝑒 𝑜𝑓 𝑠𝑝𝑒𝑐𝑖𝑚𝑒𝑛 𝑎𝑐𝑡𝑢𝑎𝑙 𝐴 Transport  No nucleus BLOOD of oxygen  Flexible CELL  Has 3. MOVEMENT IN AND OUT OF CELLS haemoglobin 3.1 Diffusion  Long Contracts  This is the movement of molecules from a region of high  Many protein to get concentration to a region of low concentration down the MUSCLE fibres in structures concentration gradient. cytoplasm to CELL  This results in random movement of molecules until closer shorten cell equilibrium is reached together when energy available  The diffusion of gases and solutes is important as Move and without it, molecules which are needed for life, for CILIATED  Tiny hairs example glucose and oxygen for respiration, would not push CELL called cilia be able to get to the places they are needed. Water is mucus  Elongated needed as a solvent Absorb ROOT shape for  Factors influencing faster diffusion: minerals HAIR CELL more surface o Larger concentration gradient and water area o Higher temperature  No cytoplasm o Smaller surface area so water passes freely 3.2 Osmosis Transport  No cross walls  Movement of water molecules from a region of high XYLEM water and so cells water potential to a region of low water potential, VESSEL support connect to through a partially permeable membrane plant form tube  Conc. of solute outside cell = conc. inside cell → no  Lignin makes it change in size strong and  Conc. of solute outside cell > conc. inside cell → cell waterproof shrinks (Plasmolysis)  Regular shape  Conc. of solute outside cell < conc. inside cell → cell so many can swells (Turgid) PALISADE Photo- fit in a small  In animals: CELL synthesizes space o Increasing solute concentration inside of cell can  Many cause cell to explode as a result of it having too much chloroplasts water, crenation. PAGE 5 OF 35  CIE IGCSE BIOLOGY//0610  In plants:  Two strands coiled together to form a double helix o Increasing solute concentration inside of cell causes  Each strand contains chemicals called bases cell to become turgid, vacuole fills up.  Cross-links between strands are formed by pairs of bases o Decreasing solute concentration inside of cell causes  The bases always pair up in the same way: cell to become flaccid, losing water and vacuole gets o A and T smaller. Cell body shrinks, pulling away from cell wall o C and G 3.3 Active Transport 5. ENZYMES  Movement of particles through a cell membrane, from a region of lower concentration to a region of higher  Catalyst: a substance that speeds up a chemical reaction concentration against a concentration gradient, using and is not changed by the reaction energy released during respiration  Enzymes: proteins that function as biological catalysts  Active transport is needed when an organism wants to  Enzymes lowers amount of energy needed for reaction optimize the amount of nutrients it can take up - ion to take place uptake by root hairs and uptake of glucose by epithelial  Enzyme lowers the activation energy needed for reaction cells of villi. to take place  Lock and key theory: 4. BIOLOGICAL MOLECULES  Carbohydrates: made from Carbon, Hydrogen and Oxygen (CHO)  Fats and oils: made from Carbon, Hydrogen and Oxygen (CHO)  Proteins: made from Carbon, Hydrogen, Oxygen,  Substrate: the molecule(s) before they are made to Nitrogen and sometimes Sulfur (CHON[S]) react  Product: the molecule(s) that are made in a reaction BASIC UNITS LARGER MOLECULES  Catabolic reaction: molecules are broken down (MONOMERS) (MACROMOLECULES)  Anabolic reaction: molecules are combined Simple sugars Starch and glycogen Fatty acids and glycerol Fats and oils 5.1 Effect of Temperature on Enzymes Amino acids Proteins  Enzymes have an optimum temperature: the temperature at which they work best giving the fastest 4.1 Chemical Tests reaction ≈ 37°C in animals  Starch: Add few drops of iodine, +ve result = blue-black  When temperature increases, molecules move faster so colour collide with an enzyme in less time  Reducing sugars: Add Benedict’s reagent, then mixture  Having more energy makes them more likely to bind to is heated in water bath for 2 to 3 minutes. +ve result = active site. brick-red precipitate, -ve result = remains blue  If temperature is too high, enzyme molecules vibrate too  Proteins: Add few drops of Biuret reagent, +ve result = vigorously and enzyme is denatured; it loses its shape mauve colour and will no longer bind with a substrate.  Fats: Emulsion test; ethanol is added to mixture, and this  When the temperature is too low there is not enough is poured into a test tube with an equal amount of kinetic energy for the reaction so it reacts too slowly. distilled water, +ve result = milky-white emulsion  Vitamin C: Decolourisation of DCPIP shows that a 5.2 Effect of pH on Enzymes vitamin C is probably present.  Enzymes are sensitive to pH  Some enzymes work best in an acid and others in an 4.2 Structure of a DNA alkaline  Chromosomes are made of a molecule called DNA  Enzymes work best at their optimum pH  Each chromosome is a very long molecule of tightly  If the pH is changed then the enzyme will denature and coiled DNA will no longer fit with substrate- no reaction takes place PAGE 6 OF 35  CIE IGCSE BIOLOGY//0610 5.3 Graphs for Changes in Enzyme Activity  Warmed in ethanol until leaf is colourless to extract EFFECT OF TEMPERATURE EFFECT OF PH chlorophyll, which would mask observation  Dipped in water briefly: to soften leaf  Leaf is placed on a white tile and iodine is added. If starch is present, colour will be blue-black and if absent, it will remain orange 5.4 Enzymes and their Uses  Seeds to germinate: the enzymes turn insoluble food stores to soluble.  Biological washing powders: enzymes are added to 6.2 Light Is Necessary for Photosynthesis washing powders to help remove stains for example:  Destarch the plant by keeping it in darkness for 48hrs o Lipase for lipids from fatty foods and greasy  Place a stencil over part of a leaf fingerprints  Place the leaf in sunlight for 4-6 hours o Protease for proteins from blood stains  Remove the stencil and test for starch  Food industry:  +ve result = parts which received light turn black o Isomerase converts glucose to fructose which is  -ve result = parts which didn’t receive light remain sweeter, so less is needed to give a sweet taste yellow/brown o Pectinase helps break down cell walls in fruit juice production so it increases yield, lowers viscosity and reduces cloudiness 6. PLANT NUTRITION  Photosynthesis: process by which plants manufacture carbohydrates from raw materials using energy from light. 6.3 Carbon Dioxide is Necessary for 𝐶𝑎𝑟𝑏𝑜𝑛 𝐷𝑖𝑜𝑥𝑖𝑑𝑒 + 𝑊𝑎𝑡𝑒𝑟 → 𝑙𝑖𝑔ℎ𝑡 + 𝑐ℎ𝑜𝑙𝑜𝑟𝑝ℎ𝑦𝑙𝑙 𝐺𝑙𝑢𝑐𝑜𝑠𝑒 + 𝑂𝑥𝑦𝑔𝑒𝑛 Photosynthesis 𝑙𝑖𝑔ℎ𝑡 + 𝑐ℎ𝑜𝑙𝑜𝑟𝑝ℎ𝑦𝑙𝑙  Take two destarched potted plants. 6𝐶𝑂2 + 6𝐻2 𝑂 → 𝐶6 𝐻12 𝑂6 + 6𝑂2  Cover both the plants with bell jars and label them as A  The carbon dioxide diffuses through the open stomata of and B. the leaf of a plant and water is taken up through roots.  Inside A, keep NaHCO3 (sodium bicarbonate). It produces  Chlorophyll is a dye, which traps light energy and CO2. converts it into chemical energy for the formation of  Inside B, keep NaOH (Sodium hydroxide). It absorbs CO2. carbohydrates and their subsequent storage.  Keep both the set-ups in the sunlight for at least 6 hours. 6.1 Chlorophyll Is Necessary for  Perform the starch test on both plants. Photosynthesis  Take a potted plant with variegated (green and white) leaves.  Destarch the plant by keeping it in complete darkness for about 48 hours. A B  Expose the plant to the sunlight for a few days.  Leaf boiled in water for 2 minutes to break down cell  The leaves of Plant A will turn black after the starch test walls, denature enzymes and allow for easier  The leaves of Plant B will remain orange/brown after penetration by ethanol. starch test PAGE 7 OF 35  CIE IGCSE BIOLOGY//0610 6.4 Limiting Factors 6.6 Leaf Structure Limiting factor: something present in the environment in such short supply that it restricts life processes. Light intensity  As the amount of light increases, the rate of photosynthesis increases (a-b) C  The limiting factor is light B  Increasing the amount of light after a certain point has no effect A on the rate (c)  The limiting factor is now carbon dioxide or temperature Carbon dioxide concentration  Cuticle: waxy layer that prevents water loss from top of the leaf  As the amount of carbon dioxide increases, the rate of  Epidermis: transparent cell that allows sunlight to pass photosynthesis increases (a-b) through to the palisade cell  The limiting factor is carbon C  Palisade: found at the top of the cell and contains many dioxide B chloroplasts which absorbs sunlight.  Increasing amount of carbon  Spongy mesophyll layer: irregularly shaped cells which A create air spaces to allow gaseous exchange to take dioxide after a certain point has not effect on rate (c) place; do not contain many chloroplasts  The limiting factor is now light or  Vascular Bundle: made up of xylem and phloem temperature (warmth)  Xylem: vessel which transports water and dissolved Temperature minerals and has lignified walls made of cellulose  Phloem: vessel which transports nutrients  As temperature increases, the rate  Stomata: little holes that opens and closes to allow of photosynthesis increases until it gaseous exchange to take place. The stomata close to reaches optimum temperature prevent water loss and open to let gases come in and 40°c (a) out. When guard cells lose water, the stoma close (at  The limiting factor is the night), while the stoma open when guard cells gain temperature A B water & swell (during the day).  Increasing the temperature above 40°c will cause the enzymes to denature (b)  This will decrease rate of photosynthesis 6.5 Glasshouse Systems To increase the crop yield, farmers control the limiting factors: 6.7 Xylem  CO2 enrichment: paraffin is burnt to increase CO2 concentration by three times the original amount and  Unidirectional vessel which doubling the yield transports water and dissolved minerals.  Optimum temperature: thermostatically controlled heaters make the temperature right for enzymes to work  Walls are made out of waterproof lignin.  Optimum light: light has a high intensity for more photosynthesis, the correct wavelengths (red and blue  Water moves up due to not green) and duration controls production of fruit transpiration and osmosis PAGE 8 OF 35  CIE IGCSE BIOLOGY//0610 6.8 Phloem 7.1 Malnutrition  Bidirectional vessel  A condition caused by eating an unbalanced diet. Several  Contains sieve forms: elements which allow o Overnutrition: balanced diet but eating too much of sugars to pass from one everything cell to next downwards o Undernutrition: having too little food  Contains companion cells o Eating foods in incorrect proportions which provide energy for active transport of sugars all over 7.2 Effects of Malnutrition plant.  Starvation: losing strength & finally dying because of  Translocation moves organic molecules (sugars, amino lack of food acids) from source to sink.  Coronary heart disease: eating too much fats which are  Phloem vessels still have cross walls called sieve plates rich in saturated fatty acids and cholesterol, may lead to that contain pores. heart attack  Companion cells actively load sucrose into the phloem.  Constipation: lack of roughages in food causes  Water follows high solute in phloem by osmosis. A constipation because roughages are indigestible and positive pressure potential develops moving mass of form bulks. Friction between bulks and walls of intestine phloem sap forward. stimulate the peristalsis  Phloem still contains small amount of cytoplasm along  Obesity: Eating too much fats and carbohydrates leads the walls but the organelle content is greatly reduced. to their storage in storage in the body mainly in the  Companion cells actively unload (ATP used) the organic forms of fats and causing an increase in body weight. molecules This can cause; heart attack, stroke, joint pain, mobility impairment, high blood pressure 6.9 Mineral Requirements NITROGEN MAGNESIUM 7.3 Uses  Needed for protein  Needed for chlorophyll NUTRIENT USES synthesis synthesis CARBOHYD- Energy  Deficiency: small plant,  Deficiency: plant lack RATES slow growth, top leaves chlorphyll, leaves yellow FATS Source of energy, building materials, pale, bottom leaves but normal roots energy store, insulation, buoyancy, dead and roots slightly making hormones affected PROTEINS Energy, building materials, enzymes,  Nitrogen fertilizers: provide nitrogen in the form of haemoglobin, structural material nitrate ions, nitrite ions or ammonium ions. But using (muscle), hormones, antibodies fertilisers can lead to eutrophication, which is when the VITAMIN C Protect cells from ageing, production of fertiliser is transported by rain and leaches into stagnant fibres water e.g. pond or river VITAMIN D Absorption of calcium CALCIUM Development and maintenance of 7. HUMAN NUTRITION strong bones and teeth  Balanced Diet: getting all the right nutrients in correct IRON Making haemoglobin proportions FIBER Provides bulk for faeces, helps peristalsis  Diet related to age/sex/activity: WATER Chemical reactions, solvent for transport o Children Below 12: Require more calcium o Teenagers: Highest calorie Intake 7.4 Deficiencies o Adults: Balanced meal with less calories o Pregnant Women: more iron, calcium and folic acid  Vitamin C: Scurvy; loss of teeth, pale skin & sunken eyes o Males: Generally, require more energy  Vitamin D: Rickets; weak bones and teeth  Calcium: Rickets; weak bones and teeth, also poor clotting of blood, spasms PAGE 9 OF 35  CIE IGCSE BIOLOGY//0610  Iron: Anaemia: Fatigue (less iron → less haemoglobin →  Large intestine: tube shaped organ composed of two less oxygen transported → less respiration → less parts: energy) o Colon: organ for absorption of minerals and vitamins, and reabsorbing water from waste to maintain body’s 7.5 Human Alimentary Canal water levels  Ingestion: taking substances (e.g. food, drink) into the o Rectum: where faeces are temporarily stored body through the mouth.  Anus: ring of muscle which controls when faeces is  Egestion: passing out of food that has not been digested, released. as faeces, through the anus.  Digestion: the break-down of large, insoluble food 7.6 Diarrhoea molecules into small, water soluble molecules using  Diarrhoea: when not enough water is absorbed from the mechanical and chemical processes faeces  Mouth: contains teeth used for mechanical digestion,  To cure this is to give oral rehydration therapy area where food is mixed with salivary amylase & where  One of these this infectious by a bacterium causing the ingestion takes place diseases cholera (spreads rapidly)  Salivary glands: produce saliva  The cholera bacterium produces a toxin that causes which contains amylase secretion of chloride ions into the small intestine, and helps food slide causing osmotic movement of water into the gut, down oesophagus  Oesophagus: tube- causing diarrhoea, dehydration and loss of salts from the shaped organ which uses blood peristalsis to transport food from mouth to stomach 7.7 Teeth  Stomach: has sphincters to INCISOR CANINE PREMOLAR MOLAR control movement into and also has pepsin (a protease) to break down proteins into peptides, it also kills bacteria with hydrochloric acid. They also have elastic walls.  Small intestine: tube shaped organ composed of two Rectangular Sharp- Blunt for Blunt parts the: shape, sharp pointed for chewing and chewing and o Duodenum: fats are emulsified by bile, and digested for cutting holding and crushing crushing. by pancreatic lipase to form fatty acids and glycerol. and biting cutting Two roots Pancreatic amylase and trypsin (a protease) break down starch and peptides into maltose and amino acids 7.8 Structure of a Tooth o Ileum: Maltase breaks down maltose to glucose. This  Enamel: the strongest tissue in the body made from is where absorption takes place; adapted by having calcium salts villi and microvilli.  Cement: helps to anchor tooth  Pancreas: produces pancreatic juice which contains  Pulp cavity: amylase, trypsin and lipase and hydrogencarbonate. contains tooth-  Liver: produces bile, stores glucose as glycogen, producing cells, interconverting them to keep glucose concentration blood vessels, and constant. Also carries out interconversion of amino acids nerve endings which (transamination), deamination and removal of old red detect pain. blood cells and storage of their iron. Also site of  Dentine: calcium salts breakdown of alcohol and other toxins. deposited on a framework  Gall bladder: stores bile from liver of collagen fibres  Bile: produced by liver and stored in gall bladder, its role Neck: in between crown and root, it is the gums is to emulsify fats, to increase surface area for the action of enzymes. PAGE 10 OF 35  CIE IGCSE BIOLOGY//0610 7.9 Tooth Decay  Vein: delivers absorbed products to liver via hepatic portal vein.  Gland: produces enzymes  Lacteal: absorbs fatty acid and glycerol  Epithelium: only one cell thick for faster transport. The cells of the epithelium are folded to form microvilli.  Small intestine and colon absorb water o The small intestine absorbs 5–10 dm3 per day o The colon absorbs 0.3–0.5 dm3 per day 7.10 Prevention 8. TRANSPORT IN PLANTS  Eating food with low sugar content 8.1 Xylem and Phloem  Regular and effective teeth brushing to remove plaque  Functions of xylem and phloem  Finishing a meal with a crisp vegetable and a glass of o To transport substances from source, where they are water taken in or made, to the sinks, where they are used 7.11 Chemical Digestion o To support the stem  Where enzymes are used to break down large insoluble substances such as proteins into smaller soluble substances like amino acids so that they can be absorbed.  Amylase: breaks down starch into maltose, it is produced in the pancreas (but also in the salivary gland)  Protease: breaks down proteins to peptides (done by Root Stem pepsin) then into amino acids (done by trypsin). Pepsin comes from the stomach and trypsin comes from the pancreas.  Lipase: breaks down lipids into fatty acids and glycerol, produced by the pancreas.  Hydrochloric acid in gastric juice: o Denaturing enzymes in harmful microorganisms in Leaf food 8.2 Root Hair Cell o Giving the optimum pH for pepsin activity 7.12 Absorption  Movement of digested food molecules through wall of the intestine into the blood or lymph.  The small intestine is the region for absorption of digested food.  The small intestine is folded into many villi which increase the surface area for absorption. One villus will have tiny folds on the  Function: to absorb water and minerals from the soil cells on its outside called  They have an elongated shape for more surface area microvilli. which increases the rate of absorption of water by  More surface area osmosis and ions by active transport means more absorption can happen  Capillary: transports glucose and amino acids PAGE 11 OF 35  CIE IGCSE BIOLOGY//0610 8.3 Pathway Taken By Water 8.7 Translocation  Water enters root  Movement of sucrose and amino acids in phloem; from hair cell from regions of production (sources) to regions of storage or moist soil via to regions of utilization in respiration or growth (sinks). osmosis because  Translocation in different seasons: water potential is o Spring: sucrose transported from stores in roots to higher in soil than leaves in cytoplasm. o Summer & early autumn: sucrose goes from  Water passes photosynthesizing leaves to root stores, through the cortex cells by osmosis 9. TRANSPORT IN ANIMALS but mostly by  Circulatory system: system of tubes (veins, capillaries, “suction”. arteries) with a pump (heart) and valves (in heart and  Water and veins) to ensure one-way flow of blood. minerals are forced to cross the endodermis.  Water enters xylem then leaves when it gets to 9.1 Transport Systems mesophyll cells  Single circulation system (fish): o Two heart chambers 8.4 Transpiration o Blood absorbs oxygen in gills  Transpiration: evaporation of water at surfaces of the o Released in body cells then back to heart mesophyll cells followed by loss of water vapour from  Double circulation system: plant leaves, through stomata. o Four heart chambers  Water leaves mesophyll cells, into air spaces created by irregular shape of spongy mesophyll cells, then diffuses o Blood passes through heart twice out of the stomata. o Oxygenated in lungs, to heart, to body, back to heart  Wilting: occurs if water loss is greater than water uptake o Advantage: delivers greater blood flow rate to tissues – cells become flaccid, tissues become limp and plant no around the body as the heart pumps the oxygenated longer supported blood to it from the lungs 8.5 Uptake of Water 9.2 The Heart  Caused by water loss in leaves which lowers its water potential  Water moves from xylem to leaf tissues via osmosis  Water moves up the stem in the xylem due to tension (because of cohesion of water molecules to each other) caused by water loss from the leaves  Ends with the gain of water through roots Bicuspid  This upward flow of water is called the transpiration stream 8.6 Factors Affecting Rate of Transpiration  Temperature: higher temperatures increase water- holding capacity of air and increases transpiration rate Septum  Humidity: low humidity increases water potential gradient between leaf and atmosphere  increasing transpiration rate  Right atrium: collect deoxygenated blood & pump it to  Light intensity: high light intensity causes stomata to right ventricle open (to allow more photosynthesis) which causes  Right ventricle: pumps deoxygenated blood to lungs increase in transpiration PAGE 12 OF 35  CIE IGCSE BIOLOGY//0610  Pulmonary artery: carries deoxygenated blood from  The heart muscle cells are deprived of oxygen & glucose, right ventricle to lungs and poisonous wastes such as lactic acid build up.  Septum: separates left and right sides of the heart  Part of the heart muscle stops contracting, causing a  Pulmonary vein: carry oxygenated blood from lungs to heart attack left atrium  Caused by stress, smoking, poor diet, poor lifestyle &  Left atrium: collect oxygenated blood and pump it to left genetically ventricle  Can be prevented by not smoking, avoiding fatty food  Left ventricle: pumps oxygenated blood to the body via and exercising regularly the aorta  Treated by aspirin and surgery (stents, angioplasty and  Aorta: carries oxygenated blood from left ventricle to by-pass) rest of body  Tricuspid and bicuspid valves: prevent backflow of 9.6 Arteries, Veins and Capillaries blood into the atria when ventricles contract (atria VESSEL FUNCTION STRUCTURE ventricular valves)  Elastic walls expand and  Pulmonary and aortic valves: prevent backflow of blood relax as blood is forced from the arteries into the ventricles (semi-lunar valves)  Transport out; causes pulse high pressure  Thick walls withstand ARTERY 9.3 Cardiac Cycle blood away high pressure from heart  Rings of muscle narrow or widen artery to control blood flow.  Valves prevent backflow of blood.  Blood is at low pressure,  Transport but nearby muscles Cardiac diastole: Atrial systole, Atrial diastole, low pressure VEIN squeeze veins and help all chambers are ventricular ventricular blood to the push blood to the heart heart relaxed, and blood diastole: atria systole: after atria  Large diameter and thin flows into the contract, pushing relax, ventricles walls reduce resistance heart blood into the contract, pushing to flow of blood ventricles blood out of heart  One cell thick walls for  Physical activity makes the heart beat more quickly and  Allow easy diffusion more deeply, for an increased circulation of blood so  Highly branched; large substances to that more oxygen and glucose can get to the muscles. CAPILLARY surface area diffuse into  Capillary beds constantly cells 9.4 ECG Trace supplied with fresh  The electrical activity of the heart can be monitored blood, so diffusion occurs by the electrocardiogram, pulse rate and listening to  Useful substances move out of plasma of capillaries into tissue fluid (fluid in between cells in tissues) the sounds of the valves closing  Cells need oxygen and nutrients, and produce waste  Physical activity makes the heart beat more quickly products such as CO2 & useful products such as hormone and more deeply, for an increased circulation of  Capillaries are constantly supplied with new blood, blood so that more oxygen and glucose can get to the otherwise diffusion could not occur muscle  Lungs → heart  Heart → Lungs = Pulmonary vein = Pulmonary artery 9.5 Coronary Heart Disease  Liver → heart  Heart → Liver  Coronary artery becomes blocked, interrupting the = Hepatic vein = Hepatic artery supply of blood to the heart muscle.  Kidneys → heart  Heart → Kidneys = Renal vein = Renal artery PAGE 13 OF 35  CIE IGCSE BIOLOGY//0610 9.7 Lymphatic System  The pathogen for a transmissible disease may be  Circulation of body fluids, and the production of transmitted either: lymphocytes. o Direct contact e.g. through blood, body fluids  Lymph node contains many lymphocytes which filter o Indirectly e.g. from contaminated surfaces/food, from lymph. animals, from air  Tissue fluid: made when plasma is squeezed out of capillaries. 10.2 Body Defences  Substances diffuse between cells and tissue fluid.  The human body has many natural defences against  Lymph vessels collect lymph and return it to the blood. pathogens.  Tissue fluid returns to the capillaries by osmosis.  Mechanical barriers: o Nostrils contain hairs that help trap dust 9.8 Blood o Skin has a thick outer layer of dead cells  Red blood cells: haemoglobin and oxygen transport  Chemical barriers:  White blood cells: phagocytosis and antibody formation o Sticky mucus which can trap pathogens  Platelets: causing clotting o In the stomach, hydrochloric acid is secreted which kills  Plasma: transport of blood cells, ions, soluble nutrients, many of the bacteria in food hormones, carbon dioxide, urea and plasma proteins  Cells: Pathogens that manage to get through all these defences are usually destroyed by white blood cells: o Some of these cells take in and digest the pathogens by phagocytosis o Others produce antibodies that incapacitate or kill the 9.9 Immune system pathogen PHAGOCYTE LYMPHOCYTE o Vaccination against disease helps antibodies to  Phagocyte has lobed  Lymphocytes are found produce very quickly nucleus and vesicles in blood and in lymph containing digestive nodes 10.3 The Immune System enzymes.  Large nucleus and they  An antibody is a protein molecule which fits into another  Phagocytosis: engulf produce antibodies, molecule pathogen, vesicles fuse  Antibodies: Y-shaped  Pathogen molecules are called antigens. with vacuole, enzymes protein, bind to label  To destroy a pathogen, antibody molecules must be digest bacteria. pathogens.  Antigen: protein/ made which are exactly the right shape to fit into  Then either destroyed carbohydrate on surface by being ingested by molecules (antigens) on the outside of the pathogen. of pathogen which phagocytes, or the  Antibodies lock onto antigens leading to destruction of provokes immune system antibodies may do it. pathogen / marking of pathogens for destruction by phagocytes 9.10 Blood Clotting  If a pathogen enters the body, it meets a large number  Reduces blood loss and keeps pathogens out of lymphocytes. One of these will recognize the  Fibrinogen (inactive) turns to fibrin (activated), and pathogen and divide rapidly by mitosis forms a mesh to trap red blood cells, which eventually  These lymphocytes then secrete antibody, destroying dries to form a scab. the pathogens  Active immunity: defence against a pathogen by 10. DISEASES AND IMMUNITY antibody production in the body.  Active immunity is gained after an infection by a 10.1 Pathogens pathogen or by vaccination.  Pathogen: a disease-causing organism.  Vaccines immunise children against diseases caused by  Transmissible disease: a disease in which the pathogen pathogens can be passed from one host to another. PAGE 14 OF 35  CIE IGCSE BIOLOGY//0610  Process of vaccination: 11.2 Structure o Harmless pathogen given which has antigens o Antigens trigger an immune response by lymphocytes which produce antibodies o Memory cells are produced that give long-term immunity  In controlling the spread of disease, it is important to consider hygienic food preparation, good personal hygiene, waste disposal and sewage treatment  Passive immunity: short-term defence against a pathogen by antibodies acquired from another individual, e.g. mother to infant  Memory cells are not produced in passive immunity  Babies get passive immunity by breast feeding. o Breast milk contains antibodies from the mother which are passed on to her baby.  Cartilage (in trachea): prevents the trachea from o Useful because a young baby’s immune system is not collapsing during absence of air and also to protect it well developed and so the mother’s antibodies can  Ribs: to protect vital organs and blood vessels and protect it against any diseases to which she is immune expands and contracts (and efficient breathing) for the first few months of its life  Intercostal (internal & external) muscles: situated  Some diseases are caused by the immune system between the ribs that create and move the chest wall targeting and destroying body cells (Type 1 diabetes)  Diaphragm: produces volume and pressure changes in the thorax leading to the ventilation of the lungs 11. GAS EXCHANGE IN HUMANS 11.1 Gas Exchange INSPIRED AIR EXPIRED AIR PROPERTY OF SURFACE REASON  21% oxygen  18% oxygen THIN (ONE CELL THICK) Short distance to diffuse  0.04% carbon dioxide  3% carbon dioxide Many molecules can diffuse  78% nitrogen  78% nitrogen LARGE SURFACE AREA at once  Water vapour varies to  Saturated water vapour. climate MOIST Cells die if not kept moist Concentration gradients for  Test for CO2: Blow CO2 through limewater. +ve result = oxygen and carbon dioxide WELL VENTILATED turn cloudy are kept up by regular fresh supplies of air 11.3 Effect of Physical Activity on Breathing Gases can be carried CLOSE TO BLOOD  Physical activity increases the breathing rate – more to/from the cells that breaths per minute, and the tidal volume – more air per SUPPLY need/produce them breath  This is measured with a spirometer to produce a spirogram.  During exercise, tissues respire at a higher rate, the change in breathing volume and rate helps to keep CO2 concentration and pH at safe levels. PAGE 15 OF 35  CIE IGCSE BIOLOGY//0610 11.4 Breathing 12.2 Anaerobic Respiration BREATHING IN BREATHING OUT  Release of a relatively small amount of energy by the  External intercostal  External intercostal breakdown of food substances in the absence of oxygen. muscles contract – pulls muscles relax – rib cage  In muscles: rib cage upwards and falls downwards and Glucose → lactic acid outwards inwards C6H12O6 → 2 C3H6O3  Diaphragm muscles  Diaphragm muscles relax contract – diaphragm – returns to dome shape  In yeast (single-cell fungi): moves upwards  Lung volume decreases –  Lung volume increases – and pressure increases Glucose → ethanol + carbon dioxide and pressure falls  Air is forced out C6H12O6 → 2C2H5OH + CO2  Air rushes in to equalise  Disadvantages of anaerobic respiration: pressure o Only produces 1/20 of the energy per glucose molecule that aerobic respiration would o Produces poisonous lactic acid  Lactic acid: o Transported in blood to heart, liver and kidneys, which oxidize it o The heart, liver and kidneys need extra oxygen to do this which causes you to continue breathing heavily after exercise. o The extra oxygen is called the oxygen debt. 13. EXCRETION IN HUMANS  Excretion: the removal from organisms of toxic  Internal intercostal muscles: are used in coughing and materials, the waste products of metabolism (chemical sneezing. reactions in cells including respiration) and substances in  Mucus & cilia: goblet cells produce sticky mucus to trap excess of requirements. and eliminate particulate matter and microorganisms.  Substances should include carbon dioxide, urea and  Ciliated cells have cilia: little hairs which sweep back and salts. forward in a coordinated way to brush mucus up the lungs into the mouth 13.1 Function of Kidney  Removal of urea and excess water and the re-absorption 12. RESPIRATION of glucose and some salts  Urea is formed in the liver from excess amino acids  Chemical reactions that break down nutrient molecules  Alcohol, drugs & hormones are broken down in the liver in living cells to release energy.  Uses of energy in the body of humans: muscle contraction, protein synthesis, cell division, active transport, growth, the passage of nerve impulses and the maintenance of a constant body temperature.  Respiration involves the action of enzymes in cells 12.1 Aerobic Respiration  Release of a relatively large amount of energy in cells by the breakdown of food substances in the presence of  Cortex: contains Bowman’s capsules and coiled tubules oxygen.  Ureter: carries urine from kidney to bladder Glucose + oxygen → carbon dioxide + water  Medulla: contains loops of Henlé and collecting ducts C6H12O6 + 6O2 → 6CO2 + 6H2O  Loop of Henlé: selectively absorbs water/solutes PAGE 16 OF 35  CIE IGCSE BIOLOGY//0610  Collecting ducts: reabsorbs water into blood and store 5. Collecting duct: the remaining substances move wastes until they are passed into ureter through the second coiled tubule (distal tubule), into  Urethra: carried urine from bladder to the outside. the collecting duct. The permeability of this part of the  Bladder: stores urine nephron to water is controlled  Renal capsule: filters from blood: water, glucose, urea and salts. 13.3 Dialysis  Tubule: (yellow) reabsorbs 100% of glucose, most of the  When a kidney machine takes a patient’s blood and water and some salts back into the blood (red), leading cleans it, then returns the blood to circulation. to concentration of urea in the urine as well as loss of  This is how it works: excess water and salts into the tubule. o Blood enters machine from patient  Renal artery: brings wastes and water from blood o The pump passes the blood passes the dialysis tubing  Renal vein: reabsorbs water and useful molecules and which is semi-permeable therefore acting as a filter leaves wastes behind o The surrounding liquid contains some salts, glucose but no urea so waste materials pass from blood by 13.2 Structure of the Kidney diffusion; o The ‘cleaned' blood returns to patient's circulation/body DIALYSIS TRANSPLANT  More expensive in the  Less expensive in the long run long run  Very disruptive (three 6-  Not very disruptive (only 8 hrs sessions per week) have to take  Do not need to find medication) kidney  Need a kidney  Need a machine & must  Can go anywhere, live near one anytime  Risk of rejection 14. COORDINATION AND RESPONSE 14.1 Nervous Control in Humans 1. Ultrafiltration: blood from renal artery enters the  The nervous system consists of two parts: glomerulus. Water, urea, salts and glucose are forced o Central nervous system (CNS) consisting of the brain into the Bowman’s capsule. Blood cells and large and spinal cord, which are the areas of coordination proteins cannot pass through. o Peripheral nervous system (PNS) made up of nerves 2. Selective reabsorption: in the proximal tubule two thirds of the salt and water and all the glucose moves and neurones, which coordinate and regulate bodily out of the nephron, by active transport. These functions. substances are reabsorbed back into the blood  Involuntary actions: not under conscious control e.g. capillary. reflex action 3. Loop of Henlé: this part of the loop of Henlé is  Voluntary actions: are done if we decide to carry them permeable to water but not salt. Water passively out diffuses out of the nephron because of the low water potential of the medulla tissue fluid. 14.2 Types of Neurons 4. Loop of Henlé: this part is permeable to salt but not  Nerve impulse: an electrical signal that passes along water. The loss of water from the filtrate in the nerve cells called neurones previous stage increases the salt concentration. Some salt passively diffuses out of the loop here. PAGE 17 OF 35  CIE IGCSE BIOLOGY//0610 Motor Neurone: Sensory Neurone:  Reflex action: means of automatically and rapidly integrating and coordinating stimuli with the responses of effectors (muscles and glands) 14.4 Synapses  Synapse: a junction between two neurones, consisting of a gap across which impulses pass by diffusion of a neurotransmitter  Synaptic cleft: small gap between each pair of neurones Relay (connector) neurone:  Inside the neurones axom, there are 100s of tiny vacuoles (vessicles each contain a chemical called neurotransmitter)  When an impulse arrives, the vessicles move to the cell membrane and empty their content into the synaptic cleft  The neurotransmitter quickly diffuses across the tiny gap and attaches to receptor molecules in the cell membrane of the relay neurone  This can happen because the shape of the neurotransmitter molecules is complimentary to the 14.3 Reflex Arc shape of the receptor molecule  A reflex action is an involuntary, quick action to respond to a stimulus, in order to protect the body from danger  Many drugs e.g. heroin act upon synapses  E.g. quickly removing your hand from hot metal surface 14.5 Antagonistic Muscle  They involve three neurones: a sensory neurone, relay neurone and motor neurone.  A muscle that opposes the action of another; e.g. biceps  The gap between neurones is called a synapse. and triceps are antagonistic muscles or circular and radial muscles in the eye  How the reflex arc works:  Agonist: a muscle that contracts while another relaxes; o A stimulus affects a receptor (cell or organ that e.g. when bending the elbow the biceps are the agonist converts a stimulus into an electrical impulse) o A sensory neurone carries impulse from the receptor  Antagonist: a muscle that relaxes while another to the CNS contracts; e.g. when bending the elbow the triceps are o Connector/relay neurone carries impulse slowly the antagonist (because it has no myelin sheath) across the spinal  Sense organ: groups of receptor cells responding to chord specific stimuli: light, sound, touch, temperature and o Motor neurone carries impulse from the CNS to the chemicals. effector o Effector (either a muscle or a gland) carries out the response PAGE 18 OF 35  CIE IGCSE BIOLOGY//0610 14.6 The Eye 14.8 Pupil Reflex  The sense organ responsible for sight  Adjusting for high and low light intensity LOW LIGHT INTENSITY HIGH LIGHT INTENSITY  Radial muscles (straight  Circular muscles lines) contract and (circular lines) contract become shorter to pull and become shorter to the pupil (black dot) reduce the size of the making it wider, to let pupil to protect retina more light enter, to form from bleaching. a clear image on retina 14.9 Rods and Cones RODS CONES  Provide low detail, black  Provide detailed, & white images, good for coloured images; they  Cornea: refracts light seeing in low intensity work in high light  Iris: controls how much light enters pupil light (at night). intensity.  Lens: focuses light onto retina  Packed most tightly  Most tightly packed at  Retina: contains light receptors, some sensitive to light around edge of retina so centre of retina, so of different colours you can see things most objects are seen most  Optic nerve: carries impulses to the brain clearly when not looking clearly when being directly at them. directly looked at. 14.7 Accomodation  Fovea:  Adjusting for near and distant objects. o Part of the retina where the receptor cells are pushed most closley together o Where light is focused when you look straight at an object 14.10 Hormones  A chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver. 14.11 Adrenaline  A hormone secreted by the adrenal gland. NEAR OBJECT DISTANT OBJECT  It increases pulse rate, makes the glycogen in muscles  Ciliary muscles contract  Ciliary muscles relax get converted to glucose, and released into blood,  Ligaments relax  Ligaments are tight makes you breath deeper and more rapidly, airways  Lens becomes short and  Lens becomes long and become wider, and makes skin become pale as blood is fat thin diverted away.  Increases conc. of glucose in the blood for respiration.  Adrenaline is secreted for example: while bungee jumping or riding a rollercoaster PAGE 19 OF 35  CIE IGCSE BIOLOGY//0610 GLAND HORMONE FUNCTION 14.15 Glucoregulation ANDRENAL Adrenaline Prepares body for vigorous  Blood glucose levels are monitored and controlled by the GLAND action pancreas Reduces conc. of glucose in  The pancreas produces and releases different hormones PANCREAS Insulin blood depending on the blood glucose level Testos- Causes development of  Insulin is released when blood glucose levels are high – TESTIS the liver stores excess glucose as glycogen terone male sexual characteristics Causes development of  Glucagon is released when blood glucose levels are low – OVARY Oestrogen female sexual the liver converts stored glycogen into glucose and characteristics releases it into the blood 14.12 Nervous and Hormonal Systems NERVOUS ENDOCRINE COMPARISON SYSTEM SYSTEM SPEED OF Very rapid Can be slow ACTION NATURE OF Electrical Chemical MESSAGE impulses, messenger travelling along (hormones) nerves travelling in  When the control of blood glucose does not work, a bloodstream person is said to have diabetes DURATION OF Usually within May take years  Type 1 diabetes is caused by the death of the cells that RESPONSE seconds (puberty) secrete insulin AREA OF Localized Widespread o Symptom: hyperglycaemia (feel unwell, dry mouth, RESPONSE response (only response (in blurred vision and feel thirsty) or hypoglycaemia (tired, one area usually) many organs) show confusion and irrational behaviour) EXAMPLE OF Reflexes such as Development of o Treatment: eating little and often and avoiding large PROCESS blinking reproductive amount of carbohydrates, injecting insulin to reduce CONTROLLED system blood glucose concentration  Hormones are used in food production, for example oestrogen is used to boost growth rate of chickens. 14.16 Thermoregulation  Advantage: chickens grow quickly meaning more profit. Constant body temperature is maintained by:  Disadvantages: this may cause human males to develop  Insulation: provided by feminine characteristics, and it is unnatural. fatty tissue retains heat. Hairs become erect to 14.13 Homeostasis trap warm air by  The maintenance of a constant internal environment. contracting erector muscles and vice versa.  Homeostasis is the control of internal conditions within  Vasodilatation: when it is set limits hot, arterioles, which supply blood to the skin- 14.14 Negative Feedback surface capillaries, dilate  Feedback controls the production of hormones – the (become wider) to allow more blood near to skin surface hormones regulate their own production. to increase heat loss (face redder)  A negative feedback control is when the change in  Vasoconstriction: when it is cold, arterioles, which hormone level acts as a signal to cancel out that change, supply blood to the skin-surface capillaries, constrict so when blood hormone level is low, hormone (become smaller) to allow less blood near to skin surface production is stimulated, when it is high, it is inhibited. to decrease heat loss PAGE 20 OF 35  CIE IGCSE BIOLOGY//0610  Sweating: the water evaporates giving a cooling effect  Phototropism: a response in which a plant grows  Skin receptors: sense heat and sensory neurons send towards (positive) or away (negative) from the direction impulses to the hypothalamus from which light is coming.  Shivering: muscular activity generates heat  Auxins’ role in phototropism:  Thermoregulatory centre: in the hypothalamus, it o If sun shines on right side of a plant’s shoot, auxins controls the use of corrective mechanisms (e.g. sweating will accumulate on dark opposite left side. and shivering). o Auxins accumulating makes cells on left side grow faster than cells on right side. o When left side of shoot starts growing faster than right side, shoot will start to bend to right side towards sunlight.  Hormones can be used as weed killers: spraying with high concentrations of hormone (2,4-D) upsets normal growth patterns. It affects different species differently so might only kill one species not the other (this is good). 15. DRUGS 14.17 Homeostatic Organs 15.1 Drugs  Cells: change composition of blood as they remove  Any substance taken into the body that modifies or nutrients and O2 and add wastes and CO2 affects chemical reactions in the body.  Heart: keeps blood pressure constant to deliver oxygen and nutrients around body 15.2 Antibiotics  Skin: to maintain heat exchange with external  Antibiotics work by stopping a metabolic practice environment performed by the bacteria you are trying to get rid of,  Kidneys: regulate water and salt levels (osmoregulation) but not performed by human cells. and the removal of wastes like urea (excretion)  Some bacteria are resistant to antibiotics which reduces  Lungs: regulate gas exchange the effectiveness of antibiotics  Intestines: supply soluble nutrients and water to blood  Development of resistant bacteria such as MRSA can be  Liver: regulates blood solutes and removes toxins minimised by limiting use of antibiotics only when essential and ensuring treatment is completed 14.18 Tropic Responses  Antibiotics don’t work on viruses because they are not  Auxin: really living and they make the host cell perform the o Plant hormones or growth substances tasks for them. o Controls tropisms o It is produced by cells at the tip of roots and shoots of 15.3 Heroin plants Effects of the abuse of heroin: a powerful depressant  Gravitropism: a response in which a plant grows towards  Problems of addiction (positive) or away (negative) from gravity.  Severe withdrawal symptoms (vomiting, restlessness)  Auxins’ role in gravitropism:  Malnourishment as drug depresses appetite o Tend to settle at the bottom end of the root.  Financial problems – stealing, loss of job o However, this does not make the cells of the tip of  Infection from sharing needles e.g. HIV/AIDS the root grow longer; auxins prevent cells at bottom tip  Heroin affects the nervous system by its effect on the of root from growing, making cells at top of root grow function of synapses faster. o When cells of top of the root grow faster, they push root deeper into soil and root gets longer. o The root grows in direction of the gravitational pull. PAGE 21 OF 35  CIE IGCSE BIOLOGY//0610 15.4 Alcohol 16 REPRODUCTION Effects of excessive consumption of alcohol –a depressant:  Causes coronary heart diseases 16.1 Asexual Reporudction  Reduced self-control  The process resulting in the production of genetically  Depression identical offspring from one parent.  Effect on reaction times  Bacteria:  Damage to liver – cirrhosis o Reproduce by binary fission, each bacterium divides into two. 15.5 Smoking o The generation time is the time taken for a cell to Some effects of tobacco smoke: divide into 2.  Drying effect and heat irritate lungs – destroys cilia  Fungi:  Nicotine is addictive, it is also a stimulant, it increases o Single-celled yeast reproduces by binary fission. pulse rate and narrows blood vessels which can cause o All other fungi produce via spores. damage o When the sporangium bursts it spreads the spores.  Tobacco smoking can cause chronic obstructive o Spores land and grow mycelium (roots) for example pulmonary disease (COPD), lung cancer and coronary mushrooms heart disease  Potatoes:  Tar causes cancer, and is an irritant so causes coughing. o The shoot from a potato goes back underground and  There are other irritants in tobacco smoke including: the stem swells to form a new genetically identical smoke particles, ammonia, and sulphur dioxide potato.  Emphysema: walls between alveoli break making large o The swollen stem acts as a storage organ. sacs, reducing surface area massively and making you ADVANTAGES DISADVANTAGES breathless after a couple of steps  Fast: no need to find  No variation  Loss of limbs due to poor circulation, CHD and lower mate, fertilise etc.  Harmful genes sperm-count  Good characteristics are transferred  Carbon monoxide irreversibly bonds with haemoglobin kept  Overcrowding- fighting which can lead to oxygen starvation for food  Cancer of the stomach, pancreas and bladder etc.  Liver is the site of breakdown of alcohol and other toxins 16.2 Sexual Reproduction  Sexual reproduction: process involving the fusion of the 15.6 Hormones and Sports nuclei of two gametes (sex cells) to form a zygote and  Hormones: can be used to improve sporting the production of offspring that are genetically different performance from each other  Testosterone  Fertilisation: the fusion of gamete nuclei o Improved hand- eye coordination  Nuclei of gametes are haploid and that the nucleus of a o Improved body-fat composition zygote is diploid o Increased muscle mass  Anabolic Androgenic Steroids ADVANTAGES DISADAVNATGES o Affects limbic system  Produces genetically  Takes lots of time and  Mood swings different offspring; don’t energy  Impaired judgement all die from change in  Good characteristics can  High blood pressure the environment be lost  Kidney failure  Energy on improving o Increased risks of prostate cancer (male) appearances or pollen o Inconsistencies of menstrual cycle (female) volume for pollination o Changes in blood cholesterol (plants) PAGE 22 OF 35  CIE IGCSE BIOLOGY//0610 16.3 Sexual Reproduction in Plants  Anther & stigma inside  Anther & stigma hangs  Insect pollinated, dicotyledonous flowering plant: flower out foxglove  Stick stigma Stigma hairy  Flowers have stripes which act as guide-lines for insects  Pollen tube: pollen grain lands on stigma and creates a tunnel down the style, through the micropyle, to the ovules.  Structure of non-endospermic seed: Wind pollinated flower structure: grass  Formation of a seed: the zygote divides many times by mitosis to form and embryo. The cotyledon is the food store. The testa stops drying out of embryo.