CHAPTER 1 - CELLS Living organisms have 7 features or characteristics which make them different from objects that are not alive. CHARACTERISTICS OF LIVING THINGS Movement Respiration Sensitivity Growth Reproduction Excretion Nutrition action that causes a change of position or place chemical reactions that break down nutrients and make energy ability to detect changes in the environment a permanent change in size the process that make more of the same kind of organism removal from an organism of substances in excess taking materials for energy, growth and development CELLS All organisms are made of cells, large organisms contain millions of them. Some organisms, such as bacteria, are unicellular, this means that they are made by only one cell. To see cells you need a microscope. There are two types of cells: plant cells and animal cells. CELL STRUCTURE CELL MEMBRANE Both animal and plant cells have a cell membrane. All cells have a cell membrane. The cell membrane is the one that contains all the cell. It is a very thin layer of protein and fat. it is partially permeable and controls what goes in and out the cell. CELL WALL Only plant cells have a cell wall. It is made of cellulose. It is a very strong covering of the cell. It helps to protect the cell and maintain its shape. The cell wall prevents the cell from bursting. The cell wall is fully permeable. CYTOPLASM Cytoplasm is a clear jelly. It contains all the organelles. It is made of 70% water. Many substances are dissoòlved in it, like proteins. Many different metabolic reactions (chemical reactions of life) take place in the cytoplasm. VACUOLES It is a space in the cell surrounded by a membrane and containing a solution. Plant cells have very large vacuoles, animal cells have little called vesicles. The solution is called cell sap. CHLOROPLASTS Chloroplasts are only in plant cells. They contain a green pigment called chlorophyll. This pigment is required to make food for the plant with photosynthesis. NUCLEUS The nucleus is where the genetic information is stored. It is kept in chromosomes, which are made of DNA. differences between animal and plant cells CHAPTER 2 - MOVEMENT IN AND OUT OF CELLS DIFFUSION Atoms, molecules and ions are always moving, so, in a gas or liquid, particles tend to spread themselves out as evenly as they can. The gas or liquid spreads out and diffuses into the liquid or the gas. DIFFUSION IN LIVING ORGANISMS Living organisms obtain many of their requirements by diffusion. They also get rid of many of their waste in this way. For example, the carbon dioxide needed by plants for photosynthesis diffuses from the air into the leaves. This happens because in the air there is a higher concentration of carbon dioxide, and in the leaf there is a lower concentration. Oxygen, which is a waste product of photosynthesis, diffuses out of the cell in the same way. Diffusion also happens to exchange the gas during respiration. An example of diffusion, where oxygen goes into the cell from the air. OSMOSIS Water is very important for our body, and it is inside and outside all cells, but in different concentrations. For this reason, water can enter or exit the cell passing through its membrane: this is called osmosis. In this example there is a concentrated sugar solution and a dilute sugar solution, separated by a partially permeable membrane. An example of this type of membrane is visking tubing. Water molecules are small, and can pass through the membrane, but sugar molecules are much bigger and can’t pass. If the membrane wasn’t there, the sugar molecules would pass from the higher concentration area to the lower concentration area, but in this care are the water molecules that diffuse by osmosis from the lower sugar concentration area to the higher sugar concentration area, to balance. The dilute solution (where there is a lot of water) is called high water potential, and a concentrated solution (where there is less water) is called low water potential. Cell membranes are partially permeable membranes, so they let some molecules pass through and other no. Animal cells burst in pure water, because the concentration of water is higher outside the cell, so by osmosis water gets in the cell and the cell bursts . Animal cells shrink in a concentrated solution, because the concentration of water is higher inside the cell (in the cytoplasm), so all the water goes out. OSMOSIS AND PLANT CELLS Plant cells do not burst in pure water because the cell wall maintains its shape and prevents the cell from bursting. When the plant cell is very blown up it's said to be turgid. If a plant cell is put in a concentrated solution, the cell is flaccid. The cell wall remains in its shape, but the cell membrane inside of it shrinks. CHAPTER 3 - BIOLOGICAL MOLECULES CARBOHYDRATES STRUCTURE FUNCTION ATOMS IT CONTAINS EXAMPLES OF MOLECULES HOW TO TEST FOR IT Composed by many monomers. The monomers are called MONOSACCHARIDE S. Carbohydrates are composed of long chains of monosaccharides. Monosaccharides are represented with an hexagon Fast energy source Carbohydrates are used first, then fats are used. CARBON (C) HYDROGEN (H) OXYGEN (O) Monosaccharides or simple sugars: Glucose Galactose fructose We can test the presence of reducing sugars using BENEDICT'S SOLUTION. If it contains reducing sugars like glucose or maltose it goes from blue to brick red. There are many different molecules of carbohydrates: Monosaccharides Disaccharides Polysaccharides Glucose is used in respiration. It is transported to the cells, to make energy. Also plants use glucose to provide energy but they transport sucrose. Animals store energy as GLYCOGEN. Plants store energy as STARCH Disaccharides: sucrose maltose Polysaccharide or complex sugars: cellulose starch glycogen To test for starch we use IODINE SOLUTION. If there is starch, we obtain a blue/black color, otherwise the iodine solution remains orange/brown. FATS/LIPIDS STRUCTURE FUNCTION ATOMS IT EXAMP HOW TO TEST CONTAINS LES OF FOR IT MOLEC ULES A fat molecule is made of four smaller molecules joined together. They are composed of a GLYCEROL backbone and 3 long molecules called FATTY ACIDS. LONG TERM ENERGY Carbohydrates are used first, then fats are used. Energy storing to use when is needed and all carbohydrates are used. Many plants store oils in their seeds. CARBON HYDROGEN OXYGEN Fats that are liquid at room temperature are called oils. Fats Oils TO PROVIDE INSULATION (KEEPING WARM) Ethanol emulsion test. Add ethanol to the sample of food and then pour it into water. If the test is positive, it goes to a cloudy/milky white. If there is no fat it remains transparent. MAKING PLASMA MEMBRANE: PROTEINS STRUCTURE FUNCTION ATOMS IT CONTAINS EXAMPLES OF MOLECULES HOW TO TEST FOR IT They are composed of long chains of AMINO ACIDS. Amino acids are represented with a circular shape. There are 20 types of amino acids. In different combinations to form different proteins. MUSCLE DEVELOPMENT CARBON HYDROGEN OXYGEN NITROGEN (N) SMALL AMOUNTS OF SULFUR (S) Collagen Insulin We can use the BIURET TEST. ENZYMES Enzymes are proteins DNA STRUCTURE IMMUNE SYSTEM A LITTLE BIT OF ENERGY MAKING NEW CELLS cell membranes and cytoplasm contain a lot of protein Fats and carbohydrates do not contain nitrogen and SULFUR If the solution gets purple, the test is positive, if it is negative it remains blue. BIOMOLECULES: CARBOHYDRATES LIPIDS PROTEINS NUCLEIC ACIDS: storage and expression of genetic information, they are in long chains of nucleotids. ATOM: The smallest particle that can exist. MOLECULE: A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound that can take part in a reaction. COMPOUND: Unique substance that consists of two or more elements chemically combined in fixed proportions. ENZYMES Proteins that function as biological catalysts. In all living organisms, chemical reactions take place all the time. They are metabolic reactions. Every metabolic reaction is controlled by catalysts called enzymes. For example, inside the alimentary canal, large molecules are broken down to smaller ones in the process of digestion. Not all enzymes help to break things down. Many enzymes help to make large molecules from small ones. NAMING ENZYMES Enzymes which catalyze the breakdown of carbohydrates are called carbohydrates. Enzymes that break down proteins are called proteases. Enzymes that break down fats are lipases. HOW AN ENZYME WORKS A chemical reaction always involves one substance changing into another. The substance which is present at the beginning of the reaction is called the substrate. The substance which is made by the reaction is called the product. Every enzyme has a dent in it called its active site. This has a shape that is complementary to the shape of its substrate. The substrate fits into the active site of the enzyme, forming an enzyme-substrate complex. Each enzyme has an active site that exactly fits its substrate, so each enzyme can only act on a particular kind of substrate. This is known as the lock and key mechanism. IMPORTANT: ALL ENZYMES ARE PROTEINS ENZYMES ARE MADE INACTIVE BY HIGH TEMPERATURE: they denature ENZYMES WORK BEST AT A PARTICULAR TEMPERATURE ENZYMES WORK BEST AT A PARTICULAR PH ENZYMES ARE CATALYSTS: they are not changed in the reaction, they can be used over and over again ENZYMES ARE SPECIFIC Most chemical reactions happen faster at higher temperatures, because the molecules have more kinetic energy. However, enzymes are damaged by high temperatures, they are denatured. There is an optimum temperature and an optimum ph. Most enzymes are optimum at a pH of 7, but the enzymes in the human body have an optimum ph of 2. IF AN ENGLISH WORD ENDS IN ASE WE KNOW THAT IT IS AN ENZYME METABOLIC REACTIONS There are two types of metabolic reactions: CATABOLIC REACTIONS: They produce energy ANABOLIC REACTIONS: They produce matter VOCABULARY: CATALYST: a substance that increases the rate of a chemical reaction and is not changed by the reaction ENZYME: proteins that function as biological catalysts MONOMER: Single unit of biological molecule POLYMER: Large complex biomolecule is called a polymer CHAPTER 4 - PLANT NUTRITION PHOTOSYNTHESIS the process by which plants and some other organisms use sunlight to synthesize nutrients from carbon dioxide and water. The process by which plants manufacture carbohydrates from raw materials using energy from sunlight. EQUATION: Carbon dioxide + water Light chlorophyll = Glucose + oxygen CHEMICAL FORMULA: 6CO2 + 6H2O + SUNLIGHT + C6H12O6 + 6O2 Plants make their own food using photosynthesis. The food produced is called Glucose. LEAVES Photosynthesis happens inside chloroplasts. This is where the enzyme and chlorophyll are that catalyse and supply energy for the reaction. In a typical plant, most chloroplasts are in the cells in the leaves. Leaves are therefore adapted to allow photosynthesis in the most efficient way. A leaf is made up of several layers of cells. The bottom and top of the leaves are covered with a layer of cells called epidermis, and its function is to protect the other cells that have chloroplasts. CURTICLE: stops water evaporating from the leaf. STOMATA: small opening in the lower epidermis GUARD CELL: open and close the stomata XYLEM VESSELS: carry water PHLOEM TUBES: carry away sucrose CARBON DIOXIDE Carbon dioxide is obtained from the air, it diffuses into all cells of the leaf. WATER Water is obtained from the soil. It is absorbed by the root hairs. SUNLIGHT The flat surface helps the leaf to obtain as much sunlight as possible. The leaves are arranged so that they do not cut off light from one another more than necessary. The sunlight can reach all the layers of cells. LEAF ADAPTATIONS: Leaves are adapted to obtain carbon dioxide, water and sunlight. USES OF GLUCOSE TO MAKE ENERGY Energy is released from the leaf. Some of the glucose which a leaf makes is broken down by respiration, to release energy. STORED AS STARCH Glucose may be turned into starch and stored in the leaf TO MAKE PROTEINS AND OTHER ORGANIC SUBSTANCES Glucose can be used to make proteins or other organic substances, such as sucrose and cellulose. CHANGED TO SUCROSE FOR TRANSPORT Sucrose is small and soluble to be transported easily. LIMITING FACTORS A factor which, if in short supply limits, reduces the rate of photosynthesis. ex: light, carbon dioxide, temperature. HOW IS PHOTOSYNTHESIS RELATED TO RESPIRATION? Photosynthesis converts carbon dioxide and water into oxygen and glucose. Glucose is used as food by the plant and oxygen is a by-product. Cellular respiration converts oxygen and glucose into water and carbon dioxide. Water and carbon dioxide are by- products and ATP is energy that is transformed from the process. CHAPTER 5 - ANIMAL NUTRITION The food an animal eats every day is called its diet. To have a balanced diet, you have to eat all these nutrients: -CARBOHYDRATES -PROTEINS -LIPIDS -VITAMINES -FIBER -MINERALS -WATER ENERGY NEEDS The energy you use each day comes from the food you eat. If you eat too much food, some of the extra will be stored as fat. If you eat too little, you may not be able to obtain as much energy as you need and this will make you feel tired. USES OF NUTRIENTES DIET RELATED DISEASE FAT AND HEART DISEASE Cholesterol, contained in saturated fat, if eated in too large quantities, can cause a heart disease, and this is very dangerous. Products such as milk, cream, butter, cheese, red meat and eggs contain a lot of saturated fat. OBESITY Being very fat is called obesity. Obesity is dangerous to our health. Being obese pincreases the risk of many serious health problems, such as heart disease, strokes and diabetes. STARVATION AND MALNUTRITION In poor countries such as some parts of Africa many people have died from starvation. And even if there is enough food to keep people alive, they may suffer from malnutrition. Malnutrition is caused by not eating a balanced diet. DIGESTION The alimentary canal of a mammal is a long tube running from one end of its body to the other. The food is broken down and absorbed (it goes into the bloodstream) The food that is eaten by mammals usually contains some large molecules of protein, carbohydrate and fat. Before these molecules can be absorbed, they must be broken down into small ones. This is called digestion. Large carbohydrate molecules, such as polysaccharides, have to be broken down into simple sugars (monosaccharides) Proteins are broken down to amino acids. Fats are broken down to fatty acids and glycerol. MECHANICAL AND CHEMICAL DIGESTION When food is broken up by teeth and by churning movements of the alimentary canal you call it mechanical digestion. When the large molecules are then broken down into smaller ones you call it chemical digestion. It involves a chemical change from one sort of molecule to another, and it is done by enzymes. KEY TERMS ingestion: taking substances into the body through the mouth. digestion: the breakdown of large, insoluble food molecules into small, water-soluble molecules using mechanical and chemical processes. mechanical digestion: the breakdown of food into smaller pieces without chemical change to the food molecules. chemical digestion: the breakdown of large insoluble molecules into small soluble molecules. absorption: the movement of digested food molecules through the wall of the intestine into the blood. assimilation: the movement of digested food molecules into the cells of the body where they are used, becoming part of the cell's egestion: passing out of food that has not been digested, as feces, through the anus. THE ALIMENTARY CANAL The alimentary canal is a long tube which runs from the mouth to the anus. It is part of the digestive system, that also includes the liver and the pancreas. THE MOUTH Food is ingested and the teeth bite the food into smaller pieces (mechanical digestion), the tongue mixes the food with saliva and forms it into a bolus. When the bolus is swallowed, it goes down the esophagus. THE ESOPHAGUS Behind the trachea there is the esophagus, which takes food down to the stomach. THE STOMACH In the stomach enzymes break down the food and the acidity kills bacteria. The food is now called chyme. After one or two hours, the chyme goes into the duodenum. An important enzyme is pepsin. THE SMALL INTESTINE The small intestine is about 5 m long. There are several enzymes in the small intestine, which are made in the pancreas. The pancreas transfers the fluid that produces in the small intestine. This fluid contains many enzymes, including amylase, protease and lipase. Amylase breaks down starch to maltose. Trypsin breaks down proteins to polypeptides. Lipase breaks down fats to fatty acids and glycerol. BILE Bile is a fluid made by the liver, and it helps to neutralise the acidic mixture from the stomach. Bile helps to digest fats. VILLI The inner wall of the small intestine is covered with millions of tiny projections. They are called villi. Each villus is about 1 mm long. VILLI ABSORB THE SUBSTANCES ABSORPTION OF DIGESTED FOOD Now the molecules are small enough to pass through the wall of the small intestine and into the blood. This is called absorption. THE LARGE INTESTINE The large intestine is a wider tube than the small intestine. The undigested food that cannot be absorbed in the small intestine forms feces, which pass through the anus. This process is called egestion. ASSIMILATION After they have been absorbed into the blood, the nutrients are taken into the liver and some of these are broken down. Then they go into the cells. This process is called assimilation. CHAPTER 6 TRANSPORT IN PLANTS PLANT TRANSPORT SYSTEM Plants need carbon dioxide and water for photosynthesis, and mineral ions, which they absorb from the ground. Carbon dioxide goes from the air into the leaves by diffusion. Plants absorb water through their roots. Water goes into the roots by osmosis. This water needs to be transported into the leaves. The transport system that does this is made up of XYLEM. Plants also have a second transport system, made up of PHLOEM. Phloem transports sucrose and amino acids from the leaves to other parts of the plant such as the roots. XYLEM goes up and PHLOEM goes down XYLEM A xylem vessel is like a long drainpipe, and it is made of many hollow, dead cells, joined end to end. Xylem vessels go from the roots upwards, right up the stem. They branch out into every leaf. PHLOEM Like xylem vessels, phloem tubes are made of many cells joined end to end. The cells are called sieve tube elements. They contain cytoplasm but no nucleus, and they are still alive. VASCULAR BUNDLES Xylem vessels and phloem tubes are usually found close together. A group of xylem vessels and phloem tubes is called a VASCULAR BUNDLE. WATER UPTAKE Plant roots have root hairs. The function of root hairs is to absorb water and mineral ions from the soil. Each root hair is a long epidermal cell. Water moves into a root by osmosis, and then it is taken up by xylem vessels. Water goes up the xylem vessels because the pressure at the top of the vessels is lowered, while the pressure at the bottom is high. The pressure at the top is reduced by transpiration. Water goes up for depression, thanks to respiration. TRANSPIRATION Transpiration is the loss of water vapor from a plant, and most of this takes place in the leaves. When water vapor evaporates from the leaves, water is pushed up in the xylem vessels. WATER POTENTIAL GRADIENT The constant loss of water from the leaves reduces the pressure at the top of the xylem vessels, so that water flows up them. Water molecules have a strong tendency to stick together (this is called COHESION), so, when water is pulled up the xylem vessels, all the water column goes up. Water potential is the way that water goes from the roots to the leaves and into the air. PLANT ADAPTATIONS The root hair cells have a big surface area through which water can be absorbed Xylem vessels are a good path for water The air into the cells increases evaporation The stomata, when open, allows water vapor to go out MEASURING TRANSPIRATION RATES To measure the rate of transpiration, we can measure how fast the plant takes up water. We can do this with a potometer. TRANSPIRATION IS INCREASED BY HIGH TEMPERATURES AND LOW HUMIDITY SOURCES AND SINKS The part of a plant from which sucrose and amino acids are being translocated is called a SOURCE The part of a plant to which they are being transported is called a SINK. TRANSLOCATION The movement of sucrose and amino acids in phloem, from regions of production (source) to regions of storage, or regions of utilization in respiration or growth (sink) CHAPTER 7- TRANSPORT IN MAMMALS TRANSPORT SYSTEM -Blood -Hert -Blood vessels 3 CHARACTERISTICS OF THE HEART: -It is autonomous -Has rhythm -It never stops THE CIRCULATORY SYSTEM Blood flows into the left side of the heart, and then out to the rest of the body. Then it is brought back to the right side of the heart, before going back to the lungs again. OXYGENATED BLOOD The blood in the left side of the heart, that comes from the lungs. It contains oxygen. The oxygenated blood is then sent around the body and becomes deoxygenated. The deoxygenated blood is sent to the right side of the heart and then back to the lungs, where it gets oxygenated again. THE DOUBLE CIRCULATORY SYSTEM The blood passes through the heart twice on one complete circuit of the body. The circulatory system is made up by two parts: -The pulmonary system. The vessels that take the blood to the lungs and back -The systematic system. The vessels that take the blood to the rest of the body and back. Double circulatory systems are found in all mammals and also in birds and reptiles. Fish have a single circulatory system. ADVANTAGES OF A DOUBLE CIRCULATORY SYSTEM: When blood passes through the tiny blood vessels in the lungs, it loses a lot of pressure. In a double circulatory system, the low-pressure blood is delivered back to the heart, which raises the pressure again before sending it off to the rest of the body. THE HEART The function of the heart is to pump blood around the body, thanks to the cardiac muscle that contracts and relaxes regularly. The heart is divided into four chambers. The two upper chambers are called atria, while the lower chambers are called ventricles. The chambers on the left side are separated from the ones on the right side by the septum. Blood flows into the heart from the top, into the atria. The left atrium receives blood from the pulmonary vein, which comes from the lungs. The right atrium receives blood arriving from the rest of the body, through the vena cava. From the atria, the blood flows into the ventricles, which pump it out of the heart. The ventricles do this by contacting the muscle in their walls. The blood in the left ventricle is pumped in the aorta and goes in the body, and the right ventricle pumps the blood into the pulmonary artery, which brings it to the lungs. The left ventricle has a thicker wall, because it needs a bigger muscle to pump the blood all around the body. CORONARY HEART DISEASE The coronary arteries supply blood and therefore oxygen to the heart muscles. If the coronary artery gets blocked, the cardiac muscles run out of oxygen and the heart stops beating. This is called a heart attack or cardiac arrest. The blockage of the coronary artery is called coronary heart disease. The risk of getting a coronary heart disease increases if: -The person smokes cigarettes -The person has a diet high in salt and saturated fats. -The person is obese -The person in stressed -The person has specific genes. HEART BEAT Most people’s hearts beat around 60 and 75 times a minute when they are resting. If a person exercises, however, their heart beats faster because their muscles need more oxygen. The heart rate is controlled by a muscle in the right atrium called pacemaker. VALVES IN THE HEART Between the right atrium and the right ventricle and between the left atrium and the left ventricle there are one-way valves that stop blood from flowing from the ventricles back to the atria. BLOOD VESSELS ARTERIES Arteries carry blood away from the heart. They wave very thick walls to withstand the high pressure of the blood flowing through them. CAPILLARIES The arteries gradually divide into smaller vessels. Capillaries are very small vessels that penetrate to every part of the body. The function of capillaries is to take nutrients and oxygen to all cells of the body. VEINS Veins carry blood towards the heart. They have thinner walls compared to the arteries because the blood pressure is lower. Veins have valves in them that stop the blood from going in the wrong direction. BLOOD The liquid part of the blood is called plasma. There are also small fragments of cells called platelets. Plasma is mostly water, and many substances, such as nutrients, are dissolved in it. RED BLOOD CELLS They are made in the bone marrow of some bones and don’t have a nucleus. Red blood cells are red because they contain a pigment called hemoglobin. Hemoglobin carries oxygen. WHITE BLOOD CELLS They have a nucleus and their function is to fight pathogens and clear up any dead cell. PLATELETS They are small fragments of cells, with no nucleus, and they are involved in blood clotting. CHAPTER 8: THE RESPIRATORY SYSTEM AND RESPIRATION RESPIRATION Every living cell needs energy. -In humans they need energy to: -contract muscles -making protein molecules+making new cells -cell division -producing heat inside the body. All this energy comes from the food that we eat. The main nutrient used to provide energy is GLUCOSE. To make energy, cells have to break down the glucose molecules and release energy from them. They do this with a series of metabolic reactions called RESPIRATION. TYPES OF RESPIRATION AEROBIC RESPIRATION Aerobic respiration is what our cells do most of the time to release energy, and it consists in combining glucose with oxygen. DEFINITION: The chemical reactions in cells that use oxygen to break down nutrient molecules to release energy. GLUCOSE + OXYGEN → CARBON DIOXIDE + WATER C6 H12 06 + 6O2 → 6CO2 + 6H2O ANAEROBIC RESPIRATION It is not as efficient as aerobic respiration and it produces less energy, but this process is used by some organisms. DEFINITION: The chemical reactions in cells that break nutrient molecules to release energy without using oxygen. Yeast can respire aerobically. GLUCOSE → ALCOHOL + CARBON DIOXIDE 2 TYPES OF ANAEROBIC RESPIRATION ANAEROBIC RESPIRATION (ALCOHOLIC FERMENTATION) C6 H12 06 →yeast→ ETHANOL + CO2 ANAEROBIC RESPIRATION (LACTIC ACID FERMENTATION) C6 H12 06 →bacteria→ LACTIC ACID + CO2 Muscle cells in our body can respire anaerobically for a short time, but they make lactic acid instead of alcohol and no carbon dioxide is produced. This happens when your lungs and heart can not supply oxygen to your muscles as quickly as they are using it GLUCOSE → LACTIC ACID Yeast is a fungus AEROBIC: respiration with oxygen, 38 ATP ANAEROBIC: respiration without oxygen, 2 ATP GAS EXCHANGE IN HUMANS GAS EXCHANGE SURFACES Animals get sugars from carbohydrates . Humans obtain oxygen from the air. Carbon dioxide is a waste product that must be removed from the organism. The surfaces where gas is entering and leaving is called for gas exchange. The gas exchange surfaces have some characteristics that help the process to be quick and efficient. -They are thin to allow gas to diffuse across them quickly -They are close to a transport system -They have a large surface area -They have a good supply of oxygen THE HUMAN GAS EXCHANGE SYSTEM The lungs, each lung is filled with many air spaces called alveoli. It is here that oxygen diffuses into the blood. Lungs are supplied with air through the windpipe or trachea. THE PATHWAY TO THE LUNGS THE TRACHEA After the nose or mouth the air passes through the trachea. At the top of the trachea there is a piece of cartilage called epiglottis. This closes the trachea and stops food going down the trachea when you swallow. Below the epiglottis there is the larynx, it contains the vocal cords. The trachea has rings if cartilage around it that keep it open THE BRONCHI At the end the trachea divides in two, these two branches are called bronchi (singular bronchus). The bronchi branch into smaller tubes called bronchioles. THE ALVEOLI At the end of each bronchiole there are many tiny air sacs called alveoli. This is where gas exchange takes place. GOBLET CELLS These cells secrete sticky mucus, so when air passes over the mucus, microorganisms and particles of dust in the air get trapped in it. GAS EXCHANGE IN THE LUNGS The walls of the alveoli are the gas exchange surface. Tini capillaries are wrapped around the alveoli. Oxygen diffuses across the wall of the alveoli into the blood, and carbon dioxide diffuses the other way. Characteristic of the walls of the alveoli: They are very thin, only one cell thick The blood continues passing They have a large surface area They have a good supply of oxygen EXERCISE AND BREATHING RATE All our cells need oxygen, and this oxygen is supplied by the lungs. Sometimes, especially when we do exercise, the cells may need a lot of oxygen very quickly. When you run, for example, your muscles need much more oxygen, so you start to breathe faster. But there is a limit of speed at which the heart and the lungs can supply oxygen, and if muscles need more oxygen then the cells start to breathe anaerobically, and lactic acid is produced. When you stop running, your body starts to break down the lactic acid or transport it away. While you are running, you built up an oxygen debt. You borrowed some extra energy without paying for it with oxygen. When lactic acid is combined with oxygen, you pay off the debt. The rate at which your breathing your breathing rate are controlled by your brain. TOBACCO SMOKING Smoking damages your health, and the danger is for smokers but also non smokers. In fact, due to passive smoking, non-smokers can have damage staying in a smoker's environment. There are also other substances that can damage our health. NICOTINE It affects the brain and damages the circulatory system. TAR It contains carcinogenic chemicals. CARBON MONOXIDE It affects the blood and smoke particles that can damage the lungs. SMOKE PARTICLES They are little particles of carbon and other materials that are present in cigarette smoke that get trapped inside the lungs and seriously damage them. RESPIRATION VS BREATHING RESPIRATION: when cells produce energy from oxygen /transforming glucose into energy. BREATHING: moving air into and out of the body. Not all living things breathe. Bacteria, fish, plants, insects.. don’t breathe all living things respire. CHAPTER 12: INHERITANCE CHROMOSOMES Chromosomes are a number of long threads present in the nucleus of every cell. Each chromosome contains one very long molecule of DNA. The DNA carries a code that instructs the cell about which kinds of proteins to make. A part of a DNA molecule coding for one protein is called a gene. The genes determine everything about us. Each species of organism has its own number and variety of genes. Humans have 46 chromosomes inside each cell, all with many genes on them. Every cell in our body has an exact copy of all your genes. Our genes are unique. DNA (deoxyribonucleic acid): The molecule that contains the genetic information that determines the traits of all living organisms. CHROMOSOME: A thread-like structure of DNA, carrying genetic information in the form of genes. GENE: A length of DNA that codes for a protein. CELL DIVISION We begin our life as a single cell, a zygote, formed by the fusion of two gametes. Each gamete contains 23 chromosomes. Gametes are haploid cells, while a zygote is a diploid cell. HAPLOID NUCLEUS: A nucleus containing a single set of unpacked chromosomes DIPLOID NUCLEUS: A nucleus containing two sets of chromosomes In a diploid cell, there are two chromosomes of each kind. In each pair, one is from the mother and one is from the father. The two chromosomes of a pair are called homologous chromosomes. There are two types of cell division: mitosis and meiosis MITOSIS MITOSIS: Nuclear division giving rise to genetically identical cells. When a cell divides, two cells are produced with a perfect copy of the two sets of chromosomes in the original cell. The new cells produced are all genetically identical. Mitosis is the way in which any cell divides when an organism is growing. THE PROCESS Just before mitosis takes place, the chromosomes in the parent cell are copied. Each copy remains attached to the original one, so each chromosome is made up of two identical threads called chromatids joined together in the centromere. Two new cells are formed, each with one copy of each chromosome. MEIOSIS MEIOSIS: Reduction division in which the chromosome number is halved from diploid to haploid, resulting in genetically different cells. Gametes have only half the number of chromosomes of a normal body cell, they have only one set of chromosomes. Human gametes are formed by meiosis. One on each pair of homologous chromosomes comes from the mother, and one from the father. Meiosis produces genetic variation, because there are all sorts of different combinations. INHERITANCE INHERITANCE: The transmission of genetic information from generation to generation. Chromosomes contain many genes. There are about 20.000 genes. GENES AND ALLELES - CHINCHILLAS EXAMPLE GENE: A length of DNA that codes for a protein. ALLELE: A version of a gene. In chinchillas, genes determine the color of the fur. There are different forms of the color gene, and these are called alleles. We can call the allele that gives grey fur G and the allele that gives charcoal fur g. In each cell in a chinchilla’s body there are two copies of the gene giving instructions about which fur color protein to make. This means that there are three possible combinations of alleles: GG, gg, Gg. If the two alleles are the same (GG or gg), the chinchilla is homozygous. If the two alleles are different (Gg), it is heterozygous. HOMOZYGOUS: Having two identical alleles of a particular gene HETEROZYGOUS: Having two different alleles of a particular gene GENOTYPE AND PHENOTYPE - CHINCHILLAS EXAMPLE The genes that the chinchilla has are its genotype, and it can be GG, Gg, gg. The features the chinchilla has are called its phenotype, and this includes what we see, like the fur color. GENOTYPE: The genetic makeup of an organism in terms of the alleles present PHENOTYPE: The observable features of an organism DOMINANT AND RECESSIVE ALLELES - CHINCHILLAS There are three different possible genotypes, but two phenotypes. genotype phenotype GG grey Gg grey gg charcoal This happens because the allele G is dominant to the allele g. The dominant allele G has the same effect on the phenotype when there is one or two of it. The recessive allele g only affects the phenotype when there is no dominant allele present. A heterozygous chinchilla is said to be a carrier of the charcoal color. Only chinchillas with the genotype gg have charcoal fur. DOMINANT: An allele that is expressed if it is present RECESSIVE: An allele that is only expressed when there is no dominant allele of the gene present. ALLELES IN GAMETES - CHINCHILLAS EXAMPLE Each gamete has only one of each kind of chromosome instead of two, and therefore it only carries one of each pair of alleles of all the genes. GENES AND FERTILISATION - CHINCHILLAS EXAMPLE In a male chinchilla with genotype Gg, each of his sperm cells has either a G allele or a g allele. Half will have G and half will have g. In a female with genotype gg, all her eggs will contain a g allele. If a sperm carrying a G allele fertilizes the egg, the zygote will have a genotype of Gg, otherwise it will have gg GENETIC DIAGRAMS - CHINCHILLAS EXAMPLE 1 Parent 1: Gg - grey gametes: G, g Parent 2: gg - charcoal gametes: g, g g G Gg grey g gg charcoal Half of the offspring will be heterozygous with gray fur and half will be homozygous with charcoal fur. GENETIC DIAGRAMS - CHINCHILLAS EXAMPLE 2 Parent 1: Gg - grey Parent 2: Gg - grey G g gametes: G, g gametes: G, g G g GG Gg grey grey Gg gg grey charcoal Three quarters of the offspring will have gray fur and one quarter will have charcoal fur. PROBABILITIES IN GENETICS - CHINCHILLAS EXAMPLE In the last example, there were four possible offspring genotypes, so each time they have offspring, these are the possible genotypes that they might have. ● There is 1 in 4 chance that its genotype will be GG ● There is 2 in 4 chance that its genotype will be Gg ● There is 1 in 4 chance that its genotype will be gg But with small numbers, probabilities don’t always match reality. They are more likely to be accurate with a large number of offspring. PURE BREEDING Some populations of animals or plants always have offspring just like themselves. For example, a rabbit breed might have a strain of rabbits all with a brown coat. This happens if both parents are homozygous of the same allele. Heterozygous individuals are not pure-breeding. SEX DETERMINATION There is one pair of chromosomes responsible for determining what sex a person will be. They are called sex chromosomes. A woman has the genotype XX A man has the genotype XY X X Y X XX XX female female XY XY male male Each time, there is a 1:1 chance that the child is either sex. CHAPTER 13: VARIATION AND SELECTION VARIATION VARIATION: Differences between individuals of the same species. Differences between individuals are called phenotypic variation. There are two basic kinds of variation: ● discontinuous variation ● continuous variation Blood groups are an example of discontinuous variation, because everyone fits into one of four categories and there are no in-between categories. Height is an example of continuous variation because there are no definite heights that a person must be. If there is a normal distribution, most people are in the middle of the range and fewer at the lower or upper ends. GENETIC VARIATION One reason for the differences between individuals is that their genotypes are different. This is called genetic variation. For example blood groups. ENVIRONMENTAL VARIATION Another reason for variation is the difference between the environments of the individuals. For example tree height. In general, discontinuous variation is caused by genes alone, and continuous variation is often influenced by both genes and environment. CAUSES OF GENETIC VARIATION MUTATION MUTATION: Differences between individuals of the same species. Sometimes, a gene may suddenly change, and this is called mutation. Mutation is how new alleles are formed. Another type of mutation affects whole chromosomes. For example, in an egg cell, sometimes the chromosome 21s don’t separate and during meiosis one cell gets two chromosomes 21. The other one dies, and if the other one is fertilized, the child has Down’s syndrome. Mutations often happen for no reason, but there are some factors that make mutation more likely, for example ionizing radiation or chemicals. MEIOSIS Meiosis produces new cells that are genetically different from the parent cell. FERTILISATION Any two gametes of opposite types can fuse together at fertilization, so there are many possible combinations of genes. SELECTION Over millions of years, there have been gradual changes in organisms and populations. DARWIN’S THEORY OF EVOLUTION VARIATION Populations of organisms contain individuals which vary slightly from one to another. Some variations may adapt some organisms better to their environment. OVER-PRODUCTION Most organisms produce more young than will survive adulthood STRUGGLE FOR EXISTENCE There is competition for survival between the organisms. SURVIVAL OF THE FITTEST Only the organisms which are really well adapted to their environment will survive. ADVANTAGEOUS CHARACTERISTICS PASSED ON TO OFFSPRING Only well-adapted organisms will survive and they will pass their advantageous characteristics to their offspring. GRADUAL CHANGE Over time, the population will lose all the poorly adapted individuals and it will become better adapted to its environment. The theory is called the theory of natural selection. Gradually, the individuals in successive generations gain more and more advantageous features. We can describe evolution as change in adaptive features over time, as the result of natural selection. PROCESS OF ADAPTATION: The process resulting from natural selection, by which populations become more suited to their environment over many generations. AN EXAMPLE OF NATURAL SELECTION Resistance to antibiotics has arisen and spread to populations of bacteria. Antibiotics are substances that kill bacteria, or stop them reproducing. Many different kinds of bacteria are no longer affected by antibiotics such as penicillin. They are resistant to antibiotics. If only one bacterium mutates to be resistant to antibiotics, it will be able to reproduce and form a population of penicillin-resistant bacteria. SELECTIVE BREEDING Humans can also bring changes to living organisms, by selecting certain individuals for breeding. This process is called artificial selection. However, what humans think are desirable characteristics would often not be at all advantageous to the plant or animal if it was living in the wild. CHAPTER 14: ORGANISMS AND THEIR ENVIRONMENT ECOLOGY Animals and plants are affected by their environment, and the environment is affected by them. ECOLOGY: The study of the interaction between living organisms and their environment. HABITAT: The area where an organism lives. POPULATION: A group of organisms of the same species, living in the same area at the same time. COMMUNITY: All the organisms, all the different species, living in the same habitat. ECOSYSTEM: the set of living and non-living factors and the trophic relationships between them. ENERGY FLOW All living organisms need energy, and they get it from food and by respiration. All the energy in an ecosystem originates from the sun. Some of the energy in sunlight is captured by the plants and used to make food. Animals get their food, so their energy, from eating plants or other animals. The sequence b y which energy, in the form of chemical energy in food, passes from a plant to an animal and then to other animals is called food chain. Many different food chains link to form a food web. FOOD CHAIN: A diagram showing the flow of energy from one organism to the next, beginning with a producer. FOOD WEB: A network of interconnected food chains. PRODUCERS AND CONSUMERS Every food chain begins with a green plant. Green plants are producers, because they produce food. Animals are consumers. An animal which eats plants is a primary consumer, an animal which eats that animal is a secondary consumer, and so on along the chain. Primary consumers are called herbivores, and higher level consumers are called carnivores. PRODUCER: An organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis. CONSUMER: An organism that gets its energy by feeding on other organisms. HERBIVORE: An animal that gets its energy by eating plants. CARNIVORE: An animal that gets its energy by eating other animals. ENERGY LOSSES As energy is passed along a food chain, some of it is lost to the environment. ● ● ● When an organism uses food from respiration, some of the energy released from the food is lost as heat energy to the environment. When one organism eats another, it doesn’t eat all of it. When an animal eats another organism as food, not all molecules are absorbed. Some are lost as feces. This means that, the further you go along a food chain, the less energy is available for each successive group of organisms. This is why there are more herbivores than carnivores and more plants than animals. TROPHIC LEVELS Each stage in a food chain is called a trophic level. TROPHIC LEVEL: The position of an organism in a food chain, food web or pyramid of biomass or numbers. Because there is less energy available as you go up the trophic levels, the length of the food chain is limited. They rarely have more than five trophic levels. THE CARBON CYCLE DECOMPOSERS DECOMPOSER: An organism that gets its energy from dead or waste organic matter. Decomposers are extremely important because they help to release substances from dead organisms, so that they can be used again by living ones. THE CARBON CYCLE Carbon is a very important component of living things. The air contains about 0,04% carbon dioxide. When plants photosynthesise, carbon atoms become part of glucose or starch molecules. Some of the glucose is broken down by the plant for respiration, and the carbon becomes part of a carbon dioxide molecule again, and is released into the air. Some of the carbon in the plant will be eaten by animals, and when they respire carbon will go back into the air as carbon dioxide. When the plant or animal dies, decomposers will feed on them and the carbon becomes part of their body and will then be released into the air. HUMAN INFLUENCE ON ECOSYSTEMS DEFORESTATION Deforestation is the cutting down of large numbers of trees. Deforestation, especially of tropical rainforests, can cause serious damages to the environment. ● When an area of rainforest is cut down, the soil is exposed to the rain and washes away.The soil erosion can make it difficult for plants to grow back again and can cause flooding. ● Also, lots of habitats are lost and this can cause species of plants and animals to extinguish. ● Deforestation also increases the concentration of carbon dioxide in the atmosphere and decreases the concentration of oxygen. ● The loss of so many trees can also affect the water cycle, because less water goes back into the air as water vapor and less rain will fall. WATER POLLUTION 1.) reduction of oxygen needed by living organisms, caused by: ● Fertilizers, which contain nitrates and phosphates, can go into the water. Algae and green plants grow faster with nitrates, so they can grow so much that they completely cover the water and block light for plants beneath them, which die.Even the plants on top of the water eventually die, and this attracts bacteria, which use up oxygen from the water. This is called eutrophication. ● Untreated sewage can also cause eutrophication, because it provides a good food source for bacteria. 2.) Discharge of chemical waste into waterways These substances are very toxic and kill living organisms. 3.) Rubbish like plastic It is non-biodegradable and it can kill fish if they eat it.
