Biology G9 U3-5 PDF

Organisms AUTHOTROPHS = can HETEROTROPHS = can't make their own food make their own food Photosynthetic Chemosynthetic Omnivore =...

Organisms AUTHOTROPHS = can HETEROTROPHS = can't make their own food make their own food Photosynthetic Chemosynthetic Omnivore = Herbivors = Carnivore = = use light = use d/t consume both consume plants consume meat energy chemicals plant and meat The human diet Food: is the source of nutrients and energy for the body  It has three main use to human A. To provide energy for our cells to carry out all the functions of life B. To provide the raw materials for the new biological material needed in our bodies to grow and also to repair and replace damaged and worn out cells. C. To provide the resources needed to fight disease and maintain a healthy body. Nutrient: usable chemical compound found in food Roughage: indigestible substance that do not provide energy MACRONUTREINT: needed in large amounts i. Carbohydrates, ii. Proteins Nutrient iii. Lipids(fat & oil). MICRONUTREINT: needed in small amounts iv. Minerals V. Vitamins i. CARBOHYDRATE:-  They are made up of carbon, hydrogen and oxygen  provide us with energy  broken down to form glucose which is used in cellular respiration to produce energy  Stores in the from glycogen, which is found in your liver, muscles and brain.  excess carbohydrate that you eat is converted to fat  glucose is the sugar made by plants in photosynthesis and it is vital in cells for energy  starch is more complex carbohydrate stored in plants  Obtained from food like injera, honey, Potatoes, rice, bread, etc  They divide into three main types, depending on the complexity of the molecules. 10  Simple Sugars Double Comple Sugars Sugars The Simple Sugars/Monosaccharide/  There is 1-oxygen atom and 2-hydrogen atoms for each carbon atom present in the molecule.  (CH2O)n is general formula  Example: C6H12O6 is general formula for Glucose. Simple sugar Glucose Fructose Galactose The Double Sugars/Disaccharide  made up of two simple sugars join together  When two simple sugars join together to form a double sugar, a molecule of water (H2O) is removed (condensation reaction).  monosaccharide + monosaccharide → disaccharide Glucose Maltose (malt sugar) Glucose 11  Glucose Lactose (Milk sugar) Galactose Glucose Sucrose (sugarcane Fructose sugar)  Most simple and double sugars have properties to dissolve in water and they taste sweet. The Complex Sugars/Polysaccharide  Many single sugar units are joined to form a long chain.  properties of complex sugar are;  very compact molecules (for storing energy)  physically and chemically very inactive  sweet test is lost  do not dissolve in water  here are some examples of complex sugar a. Starch: energy store in plants  The sugars produced by photosynthesis are rapidly converted to starch b. Glycogen: sometimes referred to as ‘animal starch’  it is energy store found in animals  found mainly in muscle and liver tissue c. Cellulose: important structural material in plants  the main constituent in plant cell walls  consists of long chains of glucose  Human beings cannot break down its linkages and so they cannot digest cellulose. Test for Carbohydrate  Starch test  help to test presence of starch  reagent → iodine  result/color change → change to blue black  Benedict’s test (reducing, glucose)  help to test for simple sugars  reagent → benedict reagent/solution  result/color change → change to yellow ii. PROTEINS:-  Made up of the carbon, hydrogen, and oxygen, in addition they all contain nitrogen.  Some proteins also contain sulphur 12  Are polymers, made up of many small units joined together called amino acids.  There are about 20 different naturally occurring amino acids  The bond found between two amino acid is peptide bond.   proteins are coil, twist, spiral and fold amino acid  proteins differ in:  type  number of their amino acid  sequence  shape PROTEIN Water soluble Water insoluble -antibodies - connective tissue - enzymes - tendons - hormones - matrix of bone(collagen) -muscles -silk of spider web - silkworm cocoons - keratine  protein make 17-18% of human body  importance of protein are: provide less energy than carbohydrate and lipid for repair and damaged tissue and body building to make enzymes  the difference in temperature and PH denature the protein  lack of protein causes Marasmus and Kwashiorkor  Meat, fish, dairy product, white pea bean, egg, etc. are protein rich food. Test for Protein  Biuret test  reagent – Potassium hydroxide  and copper II salphate  result/color change – purple (mauve) colour iii. LIPID (FATS AND OILS):- Fat Oil Solid at room temperature liquid at room temperature Mainly Animal product Mainly Plant Product  lipids are made up of carbon, hydrogen and oxygen, but, lower proportion of oxygen than carbohydrates.  the simplest form of lipid is Glycerol and fatty acids.  fatty acids have a long hydrocarbon chain  One glycerol combines with three fatty acids  high levels of fat and Cholesterol in our diet are not good for health Saturated → each carbon atom is joined to another by single bond Fatty acid Unsaturated → carbon chains have one or more double bonds 13  source of energy in your diet and they are the most effective energy store  they contain more energy per gram than carbohydrates or proteins   Combined with other molecules, it has vital roles as hormones, in your cell membranes and in the nervous system.  All lipids are insoluble in water, but dissolve in organic solvents.  Meat, oily fish, eggs, butter, beef fat, sesame oil, niger seed oil (nug) and olive oil are sources of lipid.  Cholesterol: most made in your liver and some come from food we eat  carried around your body in your blood  Without cholesterol, you wouldn‘t survive.  It makes the cells membranes, sex hormones and the hormones which help your body deal with stress.  High levels of cholesterol in your blood seem to increase your risk of getting heart disease or diseased blood vessels. Test for Lipid  Reagent: Ethanol  Place a small sample of fat/oil in a test tube  add ethanol  Shake the test tube  add water  Result: White cloudy layer formed Testing for vitamin C  DCPIP (dichlorophenol indophenol) reagent  Pour about 3 cm3 of DCPIP into a clean test tube  Using a dropper, add orange or lemon juice drop by drop to DCPIP in the test tube.  Positive result: gradual fading of the blue color of DCPIP iv. MINERALS:  minerals are needed in small amount Mineral Approximate Location or role in body Example of foods Effects of deficiency mass in an rich in mineral adult body (g) Calcium 1000 Making bones and teeth Dairy products, fish, Rickets bread, vegetables Phosphorus 650 Making teeth and bones; part Most foods Improve formation of of many chemicals, teeth and bones; e.g. DNA failure of metabolism Sodium 100 In body fluids, Common salt, most Muscle cramps e.g. blood foods Chlorine 100 In body fluids, Common salt, most Muscle cramps e.g. blood foods Magnesium 30 Making bones; found inside Green vegetables Skeletal problem; cell cells chemistry affected, defects in metabolism Iron 3 Part of haemoglobin in red Red meat, liver, eggs, Anaemia blood cells; helps carry green leafy oxygen vegetables, e.g. spinach V. VITAMINS: Vitamins Food rich in Vitamins Deficiency disease Retinole (VA) Green pepper, carrot, leafy vegetables, cod Poor sight, poor growth liver oil Thiamin (VB1) Cereals, milk, liver, sprouted beans Beriberi, loss of appetite, disease of muscle Riboflavin (VB2) Green vegetables, liver, milk, meat, peas Slow growth, eye disease, tongue inflammation Niacin (VB3) Milk, meat, vegetables Pellagra Ascorbic Acid (VC) Green pepper, lemons, orange, vegetables Scurvy, bleeding gum, slow healing 14 Calciferol (VD) Fish liver oils; also made in skin in sunlight Ricket Tocopherol (VE) Cereal oil, milk, egg, yolk, lettuce, seeds Sterility Phylloquinine (VK) Green leaf vegetables Prolonged blood clothing time  v. The role of Water  your body is 60%-70% water  it is vital solvent  Transport substance in the body. example. urea, sweat  For body temperature regulation. example. sweat  for removal of waste material  it is a reactant in many important reaction in the body  needed for osmotic stability of the body Balanced diet  Is taking food from all food groups in order to maintain a healthy body. Malnutrition: when diet lacking in important elements needed for a healthy body. Over nutrition: when too much food is eaten Under nutrition: when too little food is eaten 3.2 The Digestive System Digestion: breakdown large, insoluble molecules in to smaller, simplest, & soluble molecule  It provides energy & new biological molecules. Digestion Physical (Mechanical) Chemical  Break down food in to smaller unit peaces -accomplished by enzyme  bite & chew food in mouth  squeezes food in stomach More about enzyme:- 1. enzymes are protein 2. enzymes are catalyst – remain unchanged 3. enzymes are specific – one enzyme catalyze only one reaction 4. enzymes are sensitive to temperature – all human enzymes are best at 37c0 5. enzymes are sensitive to PH – each enzymes have their own range of PH Intracellular – secreted and work inside the cell Enzymes Extracellular – different secretion and work outside the cell Digestion in mouth  Both chemical and physical digestion occur here  Ingestion: the act of taking in food  Mouth: select taste, smell and texture of food  Bite, chew and chop the food by teeth known as mastication  mix food with enzyme Starch + H2O Maltose The Human Teeth  there are 4 types of teeth  Incisors – front teeth  Canine - long and pointed teeth  Premolars - flat teeth  Molars - found at the back Structure of human teeth 15  Enamel→ the outer cover - The strongest part (hardest) - white color that resist decaying  - non-living part  Dentine → found next to enamel - very hard, similar to bone  Pulp Cavity → the center of the teeth - contain nerve and blood vessels - sensitive to heat, cold and pain  Cement → keep teeth firm with jaw (set in to your jaw) Moving the food:- Bolus: ball shaped saliva coated chunk of chewed food Peristalsis: wave like muscle contraction to move food along the throat Epiglottis: the flap that covers the trachea during swallowing so that food does not enter the lungs. Digestion in Stomach - Digestion in stomach take 1-4 hours - Sphincter: ring of muscle found at the first and last parts of the stomach - open only during swallowing and being sick - In stomach food mixed with gastric juice Hydrochloric acid (HCl) Gastric Juice Mucus Pepsin Protease enzyme, digest protein Enzyme Rennin - HCl: Make the food suitable for action of pepsin - kill some bacteria - Mucus: Protect wall of stomach from attack by HCl. - Pepsin: the major gastric juice enzyme - work best in acid Protein + H2O Pepsin Peptones - Rennin: Mostly found in mammals - Curdle milk protein - Chime: is grey soup like mixture pass to the intestine from the stomach Digestion in Intestine Small Intestine: is about 6-8m coiled tube - Produce protease, carbohydrase and lipase enzyme Duodenum → the upper part small intestine Jejunum → middle part Ileum → Lower part, digestion end here, both digestion and absorption occur a. In Duodenum - it contain bile and enzyme - pancreas secret pancreatic juice 16 Pancreatic Juice  Trypsin Lipase Pancreatic amylase  Peptone trypsin peptide  fat and oil lipase fatty acid and glycerol  starch amaylase maltose - Bile: secreted from liver, has no enzyme - it is alkaline (base) - stored in gall bladder - help to neutralize acid Fat Bile Fat droplet (emulsify fat) b. In Jejunum and Ileum - Intestinal juice is secreted here Erepsin maltase Intestinal juice lactase sucrase  Peptides Erepsin Amino acid  Maltose maltase Glucose and glucose  Lactose lactase Glucose and galactose  Sucrose sucrase Glucose and Fructose Absorption: glucose, amino acid and fatty acid and glycerol leave the small intestine by diffusion and go in to the blood supply. - Small intestine have finger like projection called Villi that absorbs food - glucose and amino acid directly go in to the blood - fatty acid and glycerol, move in to the lacteals - lacteals is part of lymph system with lymph fluid it goes to blood supply - Digested food in small intestine move in to the liver through hepatic portal vein then to each individual cell. Assimilation: taking in and uses of digested food by the cell Engestion: removal of the faeces from your body Issue of digestive health Constipation: compacted, hard and difficult to evacuate faeces, because of loss of water (lack of fiber) - treated by: eating more fiber - drinking plenty of water - taking laxatives Diarrhoea: very loose and watery faeces - treated by: drinking water with rehydration salt 17 3.3 The human respiratory system Structure of human respiratory system The respiratory system is a vital in order to get oxygen to oxidize food and release energy for proper functioning of the body. The human respiratory system consisting of the following structures: Mouth: is an organ through which the air enters into respiratory structures Nose/nasal cavity: is additional structure through which the air enters into respiratory tract. Nose contains the nasal passages, which have:- a large surface area, a good blood supply, Lots of hairs and a lining that secretes mucus.  The hairs and mucus filter out much of the dust and small particles that we breathe in, Whilst moist surfaces increase the humidity of the air we breathe into our bodies and the rich blood supply warms it  This means that the air we take in is warm, clean, and moist before it gets into the delicate tissue of our lungs. Pharynx: is the structure that serves as a common passage for both food and air Larynx or voice box: the upper part of trachea by directing air leaving the lungs over the vocal cords. Trachea: is the wind pipe which is made from C-shaped cartilage that supports it and holds it open. The lining of the trachea secretes mucus, which collects bacteria and dust particles. The cells that line the trachea are also covered in hair-like cilia that beat to move the mucus with any trapped micro-organisms and dirt away from the lungs and towards the mouth.  The opening of trachea is called glottis. The entrance of food and dust particles into the glottis is prevented by epiglottis. Bronchi (singular bronchus): are the branches that arise from the trachea, one leading to each lung. Bronchioles: are small tubes branching from each bronchus in the lung. They are much smaller than bronchi. Alveoli (singular alveolus): are tiny air sacs which are used for exchange of gases between the lungs and the blood capillaries, they are called functional unit of the lung. The lung is the major breathing organ of human; it is surrounded by membranous structure called pleural membrane. 18 The lung is spongy and elastic organ which is protected by ribs, vertebral column, diaphragm and intercostal muscle. Diaphragm: muscle separating heart and lung from abdomen. Intercostal muscle: are muscles that are found between the ribs and used in breathing. There are two sets of intercostal muscle in normal quite breathing only external intercostal muscle is involved, however if we need to breath deliberately internal intercostal muscle is involved How is air brought into the lungs? The process of breathing involves the process of inhalation and exhalation. The breathing movements are brought about by two different sets of muscles that change the pressure in the chest cavity. The mechanism of breathing Structure Inhalation (breathing in) Exhalation (breathing out) Diaphragm Contract & flatten Relax & become dome shaped External intercostal Contract Relax muscle Internal intercostal Relax Contract muscle Ribcage Moves up & outwards Moves down & inwards Chest cavity Looks bigger Looks smaller Pressure Decreases Increases Lung Inflated (filled with air) Constricts(defleats) The volume of thorax Increases Decreases The process of gaseous exchange  breathing in supplies us with the oxygen we need for cellular respiration  when we breathe out waste carbon dioxide is removed from the body  When the air is breathed into the lungs, O2 passes into the blood by diffusion along a concentration gradient.  At the same time CO2 passes out of the blood into the air of the lungs, also by diffusion along a concentration gradient.  This exchange of gases takes place in the alveoli, the tiny air sacs with a large surface area that make up much of the structure of the lungs.  The movement of O2 into the blood and CO2 out of the blood takes place at exactly the same time  There is a swap or exchange between the two and so this process is known as gaseous exchange The mechanism of gas exchange in the alveoli depends on:- a large surface area moist surfaces short diffusion distances a rich blood supply These maintain steep concentration gradient Factor affect breathing rate The breathing rate is determined by the rate of breathing and depth of breathing The normal rate of breathing in adult human being is 12-14 times per minute Depth of breathing: is the amount of air inhaled or exhaled per breath Tidal volume: is the amount of air that one can be breathed in & out at normal resting situation Vital capacity: is the maximum amount of air that is breathed in and out: The rate of breathing can be affected by the following major factors. These are: A. Exercise During exercise when muscular activity increases, the breathing rate and depth of breathing increases to supply more oxygen to release energy for the body. B. Anxiety During anxiety the body reacts as it is in danger, extra oxygen needed to more energy in order to survive danger, therefore the rate & depth of breathing increases. C. Drugs Stimulant drugs such as khat and cocaine can increases the rate and the depth of breathing. 19 D. Altitude At places of higher altitude; the level of oxygen becomes lower &lower. This makes breathing  difficult thus the rate and depth of breathing becomes higher. E. Weight Excess weight can also affect the breathing rate. It can be difficult to breathe deeply because of the fat around the abdominal organs, which makes it difficult for the diaphragm & other structures around the lungs to relax properly. F. Smoking Smoking is a habit that directly affects your respiratory system as well as other areas of your body The effect of smoking on The health: The cigarette smoke consists of around 4000 chemicals that are inhaled into the lungs. some of these include: Nicotine: is the addictive drug found in tobacco smoke. Carbon monoxide: is a very poisonous gas found in cigarette smoke.It takes up some of the oxygen carrying capacity of the blood. Tar: is a sticky black chemical in tobacco smoke and causes irritation of nose , throat & lung. Carcinogenic substances: are cancer causing substances; the most commonly carcinogenic are arsenic & benzeprene. Smoking-related diseases Smoker health may get affected in various ways : Tar is a sticky black chemical in tobacco smoke that is not absorbed into the bloodstream. It simply accumulates in the lungs, turning them from pink to grey. In a smoker, the cilia which move things away from the lungs are anaesthetized by each cigarette and stop working for a time, allowing dirt and bacteria down into the lungs. Tar makes smokers more likely to develop bronchitis -inflammation and infection of the bronchi. The build-up of tar in the delicate lung tissue can also lead to a breakdown in the alveolar structure. In these chronic obstructive pulmonary diseases (COPD) the structure of the alveoli break down and much larger air spaces develop. Cancers of lung, lips, and throat can be caused due to carcinogenic substances Smoking also affects heart & blood vessels which increases the risk of the heart attack and stroke. Smoking and the family: Smoking may have individual, family & the society; some of its effects include: Economic crisis Increased risk of respiratory diseases Psychological problems Conflict in the family Breathing hygiene: There are mechanisms that can be used to keep the breathing system into a healthy state: - Good oral hygiene - Covering the mouth during cough &sneezing - Consult a doctor for any problems related to respiratory organs 3.4 Cellular respiration The digestive system, breathing, and circulation systems all exist to provide the cells of the human body with what they need for respiration. Respiration: is the process in which energy is released from the breakdown of organic substances in the body. The energy that is used by the cells is stored in the form of a molecule known as ATP, Which stands for adenosine triphosphate. This is an adenosine molecule with three phosphate groups attached to it. When energy is needed for any chemical reaction in the cell, the third phosphate bond is broken 20 in a hydrolysis reaction. ATP+H2O→ ADP +Pi +energy  ATP is formed by the bond between adenosine diphosphate & a free inorganic phosphate group (Pi) and the all-important energy needed in the cell. ADP +Pi →ATP+H2O The importance of ATP to the body: to build up large molecules from smaller ones to make new cell material (anabolism). And also break large molecules down into smaller molecules (Catabolism). Anabolism + Catabolism = Metabolism To enable muscle contract and relax Provide energy for the active transport of some substances across cell boundaries Types of Respiration I. Aerobic respiration during the process of cellular respiration, glucose reacts with oxygen to release energy that can be used by the cell. Carbon dioxide and water are produced as waste products. The reaction can be summed up as follows: Glucose + oxygen → carbon dioxide + water + energy (ATP) Aerobic respiration takes place in the mitochondria in cells. These are tiny rod-shaped bodies (organelles) that are found in almost all cells. Cells that use a lot of energy contain lots of mitochondria II. Anaerobic respiration breaking down of food to release energy without oxygen it is a type of respiration that does not use oxygen. Anaerobic respiration produces far less ATP than aerobic respiration. It also produces a different waste product called lactic acid. Glucose → lactic acid + energy (ATP) 3.5 The circulatory system  The transport system is required to supply the needs of the body cell & remove the waste products they produce. The human transport system is the blood circulation system. It has three elements: the pipes (blood vessels), the pump (the heart), and the medium (the blood) A double circulation: Human circulatory system is called a double circulation.it consists: i. One carrying blood from the heart to the lungs and back again to exchange oxygen and carbon dioxide with the air. This is called pulmonary circulation ii. The other carrying blood all around the rest of the body from the heart and back again. This is called systemic circulation A. The blood vessels  A very important element of any transport system is the pathways along which the transport takes place.  In the human body there are three main types of blood vessels:- Arteries, Veins & Capillaries Arteries: carry blood away from the heart The largest artery is called aorta The smallest artery is called arterioles It have thick walls that contain muscle and elastic fibres It have a pulse: the pulse is the surge of blood from the heart when it beats 21 they have no valves Most arteries carry oxygenated blood ‗except:   Pulmonary artery which carry the blood away from your heart to your lungs  Umbilical artery which carries blood away from a foetus into the placenta Veins: carry blood towards the heart. The largest vein is called venacava The smallest vein is called venules ▲ They have much thinner walls than arteries & less elastic wall\ ▲ They do not have a pulse but they often have valves ▲ Most veins carry deoxygenated blood except:  Pulmonary vein, which carry oxygenated blood back from lungs to the left-hand side of heart  Umbilical vein, which carries oxygenated blood from the placenta back to the developing foetus. Capillaries ▲ They are narrow, thin walled blood vessels ▲ It help to connect arteries with veins and take blood to the tissues & cells ▲ They have no valve ▲ They are site of the exchange of substances within the body. ▲ Blood from the arteries passes into the capillaries, which have thin walls & massive surface area. B. The Human heart The human heart is a bag of reddish-brown muscle that beats right from the early days of development until the end the life, sending blood around the body. It is made up of a unique type of muscle known as cardiac muscle The walls of the heart are almost entirely muscle. These muscular walls are supplied with blood by the coronary arteries (supply oxygenated blood to cardiac muscle). The deoxygenated blood is carried away in the coronary veins, which feed back into the right atrium (atria).  Human heart is divided into 4 chambers The two upper chambers are the right & left atria The two lower chambers are the right & left ventricles  The walls of the atria are relatively thin, so they can stretch to contain a lot of blood.  The walls of the ventricles are much thicker, as they have to pump the blood out through the major blood vessels.  The muscle walls of the left-hand side of the heart are thicker than on the right. This is because the left hand side of the heart has to pump blood around the whole body whilst the right-hand side pumps only to the lungs. The working of the heart  The two sides of the heart fill and empty at the same time to give a strong, coordinated beat Mechanism of blood circulation Deoxygenated blood, which has supplied oxygen to the cells of the body and is loaded with carbon dioxide, comes into the right atrium of the heart from the veins of the body. The atrium contracts and forces blood into the right ventricle. The right ventricle contracts and forces blood out of the heart and into the lungs where it is oxygenated - it picks up oxygen. Oxygenated blood returns to the left-hand side of the heart from the lungs and the left atrium fills up. The left atrium contracts forcing blood into the left ventricle. The left ventricle contracts forcing oxygenated blood out of the heart and around the body 22 Valves Valves: mechanism in the veins that allows blood to flow in one direction only. inside the heart there are many different valves. their names describe their appearance; bicuspid (two parts): are found between the left atrium & left ventricle Tricuspid (three parts) are valves between the right atrium & right ventricles. Semilunar (half-moon): valve found at the base of aorta and pulmonary artery Septum: - wall separating the right and left sides of the heart Diastole is when the heart muscles relax and it fills with blood. Systole is when the heart muscles contract and force the blood out of the heart The pressure at which the blood travels around our arteries varies as the heart beats.  A normal blood pressure is about 120 mmHg/80 mmHg -the nominator is systolic & the denominator is diastolic pressure.  Sphygmomanometer: is an instrument that is used to measure blood pressure. C. The blood Blood is a complex mixture of cells and liquid that carries a huge range of substances around the body Blood consists of a liquid called the plasma. Plasma: - is a pale yellow liquid that transports all the blood cells & also number of other things. There are components of blood cells. These are: Red blood cells (Erythrocytes) They are more in number than other types of blood cells They are disc shaped & non-nucleated cells. They are made in bone marrow, when they mature they lose their nucleus. The RBC only live 100-120days so they are constantly being replaced. They are used to carrying O2 around our body. Because they are packed with a special red substance called haemoglobin, which picks up oxygen. Hemoglobin is a special red pigment, a large protein molecule folded around four iron atoms. 23 In a high concentration of oxygen, such as in the lungs, the hemoglobin reacts with oxygen to form oxyhaemoglobin.This is bright, which is why most arterial blood is bright red. In areas where the concentration of oxygen is lower, such as the cells and organs of the body, the  reaction reverses The oxyhaemoglobin splits to give purple-red haemoglobin (the colour of venous blood) and oxygen The oxygen then passes into the cells where it is needed by diffusion. White blood cells (leukocytes) They are much bigger than the red cells but they are fewer of them. They have a nucleus and form part of the body‘s defense system against microbes They can be classified as: Lymphocytes- form antibodies against microbes Phagocytes-engulf invading microorganisms Platelets (thrombocytes) They are small fragments of cells and very important in helping blood to clot at the site of a wound. Platelets have thread like protein fiber called fibrin for blood clotting to trap blood cells, platelets and fluid through a complex series of enzymes controlled reactions. The clotting of the blood prevents from bleeding to death from a simple cut It also protects the body from the entry of bacteria and other pathogens Human blood groups There are special proteins called antigens are found on the surface of all cells. They allow cells to recognize each other and also to recognize cells from different organisms If the cells of an immune system recognize a foreign antigen on a cell in the body, they will produce antibodies & it destroy the foreign cells. A number of different antigens are found specifically on the surface of the RBC, which gives different human blood groups. The blood grouping system is called ABO system. Based on presence and absence of these antigens , there are four types of blood groups There are two possible antigens : Antigen A & antigen B There are also two types of antibodies:- antibody A & antibody B  The below table describe the compatibility of Different blood groups Blood group Antigen on RBC Antibody in the plasma Donate to Receive from A A B A & AB A& O B B A B & AB B&O AB AB None AB only All groups O None A and B All groups O only Blood group ‗O ‗is called universal Donor, because it has no antigens so, it can be given to anyone. Blood group ‗AB‘ is called universal recipient , which has no antibodies can receive any type of blood If the blood from different blood groups is mixed together, there may be a reaction b/n the antigen & the complementary antibody which makes the red blood cells stick together, this is called agglutination. Two common problems of the circulatory system: A. Anemia: it is caused when there are:  too few red blood cells in the body, or too low levels of hemoglobin in the blood.  It is most commonly due to lack of iron in the diet so it is treated by iron rich diet. B. Hypertension (High Blood Pressure): Is considered high if the systolic pressure is >140mmHg or the diastolic pressure is >90mmHg There are a number of factors that can increase the risk of hypertension. Many of these factors mean that blood vessels are likely to be getting narrower, or becoming more rigid These factors include: - sedentary (inactive) lifestyle, Increasing age, smoking, 24 being overweight, kidney diseases, diabetes and Excessive salt intake, certain medicines such as steroids  Excessive consumption of alcohol, Treatment of hypertension Losing weight Lower salt level in diet Life style adjustment using medicines like: Diuretics: which increase frequency of urination to decrease the blood volume and Beta blockers: - these blocks the nerves w/c narrows the arteries UNIT: 4 MICROORGANISMS AND DISEASES 4.1. Micro-organisms Micro-organisms are tiny living organisms that are usually too small to be seen with the naked eye, these includes bacteria, viruses, yeast and mould Many of microorganisms are very useful while other cause diseases. Bacteria  Are single celled organisms  They are much smaller than the smallest plant& animal cells.  They contain cytoplasm surrounded by a membrane  They have non cellulose cell wall  Some bacteria have flagella to help to them move  They also come in a variety of different shape and size Viruses  are even smaller than bacteria  They usually have regular geometric shapes, and  They are made up of a protein coat surrounding genetic material containing relatively few genes.  They do not carry out any of the functions of normal living organisms except reproduction  They are obligate intracellular parasites  They have either DNA or RNA as genetic material Fungi (Yeast and mould)  Yeast are single -celled organisms  Each yeast cell has a nucleus, cytoplasm, and a membrane surrounded by a cell wall.  They reproduce is by asexual budding - splitting to form new yeast cells. Moulds  They are made up of, threadlike structures called hyphae.  The hyphae are not made up of individual cells - they are tubes consisting of a cell wall containing cytoplasm and lots of nuclei.  They reproduce asexually by spore formation. The germ theory of disease Germs are micro-organisms responsible for cause of some diseases The development of microscope Anton van Leeuwenhoek in 17th century helped different biologists to explain the relationship between infectious diseases & micro organisms The development of knowledge about micro-organisms is actually related to the theory of spontaneous generation. The theory of spontaneous generation States that living things could arise from non-living things spontaneously. This theory is opposed by many biologists & a French biologist Louis Pasteur disproved it finally by using an S- shaped flask that traps dust & microorganisms. Pasteur was convinced that any growths that appeared -for example, mould on food as it decayed - came from microscopic organisms already present in the air. 25 First he showed that the theory of spontaneous generation was wrong. Then he showed that if he boiled broth and sealed the container, the broth would stay clear until he introduced material which had been exposed to the air. At this point micro-organisms grew and the broth turned cloudy  Pasteur went on to identify the micro-organisms that caused a number of diseases including anthrax, rabies, and diphtheria. The immune system Immune system:- the system in the body which protects the body against invading microorganisms and foreign proteins. Like all living cells, pathogens carry unique protein molecules called antigens on their cell surfaces. When a pathogen gets into the body the antigens on the surface stimulate a response by the immune system. White blood cells (lymphocytes) produce antibodies to disable the pathogen. Other white blood cells (the phagocytes) then engulf and digest the disabled pathogens. Once someone have had a disease, the immune system ‗remembers‘ the antigen and the right antibody to deal with it. Control of microorganisms Sterilization is the killing of all micro-organisms in a material or on the surface of an object, making it safe to handle. These include the use of: High temperatures or heat It is highly efficient means of sterilization  Autoclaving: it involves the killing of microorganisms by boiling in water at 121 °C. under high pressure for 15-45 minutes of ‗cooking‘ at these temperatures  Ultra high temperature (UHT) is a way of treating food to kill all the micro-organisms on it. The temperatures used range from around 135 °C to 150 °C  Dry heat sterilization: Dry heat, over a long time, kills all micro-organisms. Special ovens used in microbiology use temperatures of 171 °C for an hour, or 160 °C for 2hours,.  Incineration - burning substances at high temperatures in the air - also kills micro-organisms  Pasteurization: it involves boiling or heating of milk, beer and other foodstuffs at 71.6 °C for at least 15 seconds or 62.9 °C for 30 minutes. A chemical approach to controlling micro-organisms  Possible pathogens can be attacked chemically in a number of ways.for e.g. 1. A disinfectant is a chemical or physical agent that is applied to an inanimate object to kill micro- organisms. Disinfection means reducing the number of living micro-organisms present in a sample This method discovered by Joseph Lister. some of example of disinfectant include: house hold bleach, Dilute bleach and calcium hypochlorite 2. Antiseptics: are chemical agents that are applied to living tissue to kill micro-organisms -disinfectants for the skin. it help to protect entrance of germs if the skin is cut or wounded. Growing of microorganisms Micro-organisms can be grown in laboratories under controlled condition. It is important for various purposes; these include: To know how to killed them To develop vaccines To identify their useful & harmful aspects For growing microorganism‘s biologist need to fulfill the following precondition: Isolating type of microorganisms to be studied developing suitable nutrient like agar and broth Agar: is a solid nutrient medium which is extracted from red algae Broth: is a liquid nutrient medium 26 Antibiotics  Drugs which kill bacteria but do not harm human cells  Penicillin was the first antibiotic to be discovered  Artificial immunity Our body has its own natural ability to protect itself against artificial disease, however if the immune system of the body fails to defend some dangerous disease it will be treated by artificial immunity. Artificial immunity is given in the form of vaccine Artificial active immunity: involves introduction of weakened or dead pathogen in the body which stimulates the body to produce its own antibodies. It can be natural from mother to child (natural passive) until the child produces its own natural active immunity Artificial passive immunity: it involves giving specific antibodies in the form of infection. It provides a high type of resistance but last only for short time. Natural active immunity;- acquired from exposure to the disease organism through infection with the actual disease. Vaccination (immunization):  is the use of dead or weakened strains of pathogens to produce immunity to dangerous diseases  the vaccination work through the following ways a weak or dead form of the infecting organism is put into the body by injection or by mouth once in the body, the white blood cells respond by producing antibodies If the living micro-organism enters the body in the future, antibodies are produced very rapidly to destroy it and so the disease does not develop. 4.2. Diseases Disease is any form of disorder in or on the body distorts its normal functioning Some of the most commonly known diseases which are caused by pathogenic organisms among them include: i. Tape worm (cestoda) Flat shaped worm that parasitizes the wall of intestine of humans They have no digestive system & but have cuticle to absorb nutrients The most common are beef tape worm(Taenia saginata) & the pork tapeworm(Taenia solium) They have complex life cycle which involves at least two different hosts. Transmission: eating improperly cooked or raw meat Symptoms: feeling weakness, weight loss, segments of tape worm in feaces Control & prevention: avoid eating raw meat, use antiworm drug & proper disposal of feaces Life cycle of beef tape worm Cows raised in unsanitary conditions may contain cysticerci ‗bladder worms‘ embedded in their muscles. These consist of a capsule containing a scolex. When a bladderworm is ingested (e.g. in undercooked beef), The scolex turns inside out and attaches by suckers and hooks to the wall of intestine. It then begins to produce buds, called proglottids, which remain attached to each other for a time and, as they mature, each develops both male and female sex organs. The most mature proglottids eventually break loose and are passed out in the faeces. If conditions are such that cows get access to the human faeces, they take in the eggs and the whole cycle starts again. ii. Tuberculosis  It is caused by a bacterium called Mycobacterium tuberculosis  It can affect anyone of any age, but People with weakened immune systems (such as people suffering from HIV/AIDS) are at increased risk 27 Transmission :  Droplet infection, but need prolonged exposure to someone with TB for infection to  occur. work in overcrowded conditions Symptoms  Some people may not have obvious symptoms (asymptomatic), however the symptoms of TB include: a low-grade fever fatigue a persistent cough Night sweats weight loss and Control and prevention In social terms avoiding overcrowded conditions Covering the nose &mouth during coughing Good ventilation vaccination Treatment People with active TB disease must complete antibiotic for four months or more The role of vectors in disease: A vector is an organism that transmits disease-forming micro-organisms from one host to another well-known example is the Anopheles mosquito, which carries the malarial parasite iii. Mosquitoes and malaria Malaria is a disease where mosquitoes are the vector The mosquito vector is the female Anopheles mosquito The disease itself is caused by the single-celled parasite Plasmodium It spends part of its life cycle in a mosquito and part in the human body Life cycle √ Female needs two meals of human blood to provide protein for her developing egg and this is when she passes on her load of malarial parasites. √ If the first feed the mosquito takes is from someone infected with malaria, the Plasmodium parasites called Plasmodium falciparum remain in her mouthparts √ the next time she feeds, the Plasmodium parasites pass into the blood of the victim along with the saliva - and someone else is infected with malaria Symptoms: These include fevers, chills, and sweats Control and prevention: Methods of controlling malaria must involve controlling the Anopheles mosquitoes. This can be done by: Using mosquito repellents having screens on doors and windows insecticide-treated mosquito nets Proper disposal of sewage‘ Minimize any opportunities for the mosquitoes to breed iv. Gastroenteritis/acute watery diarrhea (AWD) Intestinal infection causing acute watery diarrhea Some of the causative organisms include rotaviruses, the bacteria Salmonella and Escherichia coli (E. coli), or the protoctists Giardia and Amoeba. Transmission eating contaminated food or water prepares or handles food without washing their hands after going to the toilet poor sanitation poorly cooked and raw eggs if they are infected with bacteria such as Salmonella symptoms 28 violent abdominal cramps and pain feeling nauseous, vomiting or often both watery diarrhoea which does not usually have blood in it  slight fever general muscle aches and headache Control and prevention Good personal hygiene Avoid eating undercooked or raw food v. Cholera √ It is caused by bacteria called Vibrio cholera & it infects intestine Transmission: eating or drinking food or water contaminated by the faecal waste of an infected person Symptoms: include the pale, watery diarrhea, vomiting and dehydration, muscle cramps Treatment: taking more fluid to replace the lost through diarrhea &antibiotics, rehydration salt (ORS) Control and prevention: avoid consumption of uncooked food Proper disposal of feaces , Good personal hygiene and environmental sanitation Taking cholera vaccine vi. Typhoid (Typhoid fever) is a bacterial infection caused bacterium called Salmonella typhi - typhoid only affects humans transmission : Like other diarrhoea diseases they are spread by eating foods or drinking water contaminated by faeces from an infected individuals symptoms: it may include :A very high fever - 39-40 °C, A painful abdomen Sore throat and headache, an enlarged spleen and liver , Constipation or diarrhoea Treatment: antibiotics are used as a very effective treatment. Plenty of fluids to replace the ones they lose Control and prevention: careful hand washing after toilet visits, clean drinking water and good sewage disposal good food hygiene in kitchens and care in eating raw or lightly cooked foods vii. Sexually transmitted diseases (STDs) STDs are Infectious diseases spread by sexual contact it is also known as venereal diseases (VD) are a growing problem in Ethiopia -partly because sexual activity often starts relatively young the most commonly known STDs are: A. Gonorrhea (gonococcal infection) o Is caused by the bacterium Neisseria gonorrhoeae. o Gonorrhea germs are found in the mucus areas of the body (the vagina, penis, throat and rectum). o Transmission :It is spread through sexual contact, Having unprotected sex, having many sexual partner o Symptoms: burning sensation while urinating and a yellowish-white discharge from the genital organ  If a pregnant woman has untreated gonorrhea, she can pass the infection on to her baby result in blindness Treatment: it can be treated effectively in the early stages using antibiotic o Prevention& control: Infected individual do not have sex until your course of treatment is completed. Use a male or female condom Be faithful to sexual partner. B. Syphilis √ Is bacterial infection, caused by the spiral-shaped Treponema pallidum √ Any sexually active person can be infected Transmission: like gonorrhea It is spread through sexual contact It is congenital syphilis, which is spread from mother to foetus. This can cause very serious problems 29 for the baby when it is born. Structure of Treponema pallidum Symptoms: Syphilis progresses in distinct stages The symptoms occur in stages called primary, secondary and tertiary (late) Primary stage (the first six weeks): painless sores around reproductive organ, rectum, & mouth Secondary stage (six weeks after): The most common symptom during this stage is a rash. Other symptoms can include: Tiredness sore throat hoarseness patchy hair loss Fever headaches loss of appetite swollen glands Untreated the disease then goes into a long quiet phase Tertiary stage (late syphilis): Involve illness in the skin, bones, central nervous system and heart. It causes severe and irreversible problems that cannot be treated successfully. If a pregnant woman has untreated syphilis she may transmit the disease to her unborn child. This may result in death or deformity of the child. Treatment: It is treated easily with antibiotics such as penicillin or tetracycline Pregnant women can be treated with antibiotics to cure them and protect their baby Prevention& control: similar with gonorrhea C. Chancroid It is a bacterial STD that is caused by the bacterium Haemophilus ducreyi It is more commonly seen in men than in women. Transmission: having sex with an infected person & increase risk of becoming HIV-positive Symptoms: The first symptoms of chancroid are sore ulcerations on the genitals, particularly penis, it is soft and filled with pus. The second stage of the infection is that the lymph glands in the groin also become infected, Permanent loss of penis Treatment: it can be treated easily with a dose of antibiotics Prevention & control: be faithful sexual partner Use a male or female condom Good genital hygiene & male circumcision Using medicines correctly Traditional medicines are very &alternative form medicine in developing countries like Ethiopia o It is often holistic, based on treating the whole patient, but limiting their dose is very important. o It is based on extracts of plants including herbs and spices. Modern medicines: are responsible for cure various diseases &made in very carefully controlled doses The most common include: antibiotic & vaccine However care should be taken while using modern medicine: so the following precaution should be considered: 30 Do not take more than you are prescribed, Do not take less than you are given  Make sure you finish taking all the medicine Follow the instruction if not antibiotic-resistant bacteria may evolve which can be very serious indeed 4.3. HIV and AIDS Acquired Immune Deficiency Syndrome (AIDS) is the medical term for a combination of illnesses that result when the immune system is weakened or destroyed. It is caused by Human Immuno deficiency Virus (HIV), a virus that attacks the immune system. Transmission:  sexual intercourse which is un protected  It can pass from a mother to her baby in the womb, during birth or when she breastfeeds  Infected blood on needles used for injecting illegal drugs, or knives used for female genital mutilation. Symptoms Patients often have few symptoms to begin with but eventually their weakened immune system means they get many diseases. Treatment Antiretroviral drugs can slow down the progress of HIV/AIDS and protect unborn babies from infection.  The sooner people can start taking antiretroviral after infection, the longer they will stay healthy. Prevention & control It can be controlled by ABC rule means that: A: abstain from sex B: be faithful to sexual partner C: condom use HIV and the immune system How does HIV attack the immune system? There are two main types of white blood cells in the immune system. These are: 1. T-cells actually bind to the antigens on the invading micro-organism and destroy it. 2. B-cells make antibodies which bind to the antigen and destroy it. HIV attacks the T-cells of immune system. It gets inside them and so they can no longer work. As more T-cells are invaded by the virus, the immune system is less and less effective. This is why people with HIV/AIDS get so many other infections Stigma and discrimination Stigma is a mark of disgrace on people with HIV, while discrimination is an act of neglecting some from the group or other.& are the most serious cases that affects people living with HIV/AIDS Care and support It is important for people living with HIV/AIDS since it helps them live longer & healthier Unit 5: Classification 5.1. Principles of classification On Earth today there are many types of living things. This great variety of life is called biodiversity. Classification: is grouping of similar living things. Taxonomy: is study of classification of organisms (Greek, taxis-to arrange, nomos-law) 31 Need for classification Biologists classify living things for the following reasons:  To simplify their study To bring order out of chaos or confusion To try to understand how life originated What is a species?  A group of organisms that can breed successfully with one another to produce fertile offspring. How are living things classified? Living things are classified according to how similar they are One example is animals that are put in a group together because their limbs are built on the same basic plan. The limbs of a bat, horse, bird, human and whale all have the same basic pattern though they are used in different ways these limbs are called homologous structures. (Similar structure with d/t function) Today there are more sophisticated ways of comparing organisms. The fundamental chemicals of life - such as DNA, RNA and proteins - are found in almost all organisms The classification system ▲ Taxonomy: is the process of classifying living organisms‘ ▲ Taxa: category in classification ▲ The main taxonomic categories are kingdom, phylum (or for plants, division), class, order, family, genus and species. The largest groups into which living organisms are divided are the kingdoms. Kingdoms are subdivided into phyla, Each phylum into classes, each class into orders, Each order into families, each family into genera and each genus into species. The species is the smallest unit of classification Naming living things Different method of classification was introduced by different biologists at different times: Aristotle: Greece a philosopher.who tried to create a classification system for the living world, and grouped animals by: animals that live on land‘ and ‗animals that live in water The modern classification method is introduced by Swedish botanist Carl Linnaeus in 18th century. He developed the binomial system of nomenclature for organisms He published in a book called The System of Nature Binomial means two names. The two names of an organism are in Latin Simple rules for writing scientific names The first name is the name of the genus name & it is starts with capital letter. e.g. Homo sapiens, The second name is the name of a species & it is written with a small letter. The two names are underlined when handwritten or in italics when printed. Table 5.1 Examples of scientific names of some common organisms common name Scientific name Human beings Homo sapiens A dog Canis familiaris A housefly Musca domestica Domestic cat Felis domesticus Maize Zea mays Bean Phaseolus vulgaris Lion Panthera leo Living things are classified and named for the following main reasons. To create an internationally accepted way of referring to a particular living thing. 32 To avoid confusion created by different languages. To help in simplifying classification and study of living things.  Human Honeybee Teff Mushroom Kingdom Animalia Animalia Plantae Fungi Phylum Chordata Arthropoda Angiospermophyta Basidiomycot Class Mammalia Insecta Liliopsida Basidiomycetes Order Primates Hymenoptera Cyperales Agaricales Family Hominidae Apidae Poaceae Agaricaceae Genus Homo Apis Eragrostis Agaris Species sapiens mellifera teff campestris Table 5.2 Hierarchy of groups 5.2. The five kingdoms ▲ A kingdom is the largest taxon and consists of all the other taxa. In the modern classification, there are five kingdoms namely: 1 Kingdom Monera 4 Kingdom Plantae 2 Kingdom Protista 5 Kingdom Animalia 3 Kingdom Fungi This system of classification is known as the five-kingdom system Viruses are not classified in any of the above kingdom. This is because viruses do not have all the seven characteristics of life, although most scientists now classify them as living organisms. 1. Kingdom Monera The representative groups are Eubacteria (true bacteria) & the blue-green algae (Cyanobacteria). They are unicellular & prokaryotic (have no distinctive nucleus). They are all microscopic and they reproduce by simply splitting in two (binary fission) They have either autotrophic or heterotrophic mode of nutrition Examples include Mycobacterium tuberculosis and Haemophilus ducreyi which are pathogenic while others are useful. 2. Kingdom Protista Consists usually unicellular & eukaryotic (do have nucleus) They include plant-like organisms that can move around and animal-like organisms that cannot move Representative groups of this kingdom are subkingdom protozoa& subkingdom algae A. Subkingdom protozoa They are microscopic & have no chloroplasts They live as parasite or free living Have locomotory structure. e.g. Amoeba- pseudopodia , Paramecium:-cilia B. subkingdom algae They are photosynthetic & eukaryotic They live either in aquatic habitat or on land They have undifferentiated body called thallus. E.g. Dinoflagellates, red algae, & green algae 3. Kingdom Fungi Fungi are eukaryotic and usually multicellular. They are heterotrophic Many fungi are saprotrophs, which means they feed on dead material. They play a vital role within ecosystems as decomposers Examples of this type of fungus are Rhizopus ,Mucor and Penicillium 33 They can be parasites, feeding on living organisms. Such as Candida albicans (thrush) and Tinea pedis (athlete‘s foot) affect people and other animals. Some fungi are mutualists. This means they live in close association with another organism  and both benefit. Examples are lichens, which are a combination of a fungus and green algae Mycorrhizae, an association between a fungus and the roots of a plant. There are also single celled fungi like yeast. 4. Kingdom Plantae The plants - includes a great variety of organisms, which range from tiny mosses to giant trees & 80% of these are flowering plants The main characteristics of all plants include They have eukaryotic cells. They are multicellular organisms They contain chlorophyll and carry out photosynthesis. They are predominantly land dwelling. Their cell wall composed of cellulose Most have a waxy cuticle that helps to prevent drying out The kingdom is split into a number of divisions. Plant divisions are the same as animal phyla. The four most important divisions are: A. Division Bryophyta (mosses and liverworts) They are the simplest land plants. They do not have a true leave , stem & root system They are non-vascular (do not have xylem and phloem). The best examples of bryophytes are mosses like Etodon concinnus,and Funaria species. A moss plant: has a simple, slender stem. They also have thin simple leaves also have simple root-like structures called rhizoids and attach the mosses to the soil & used for absorption of water. The other example is the liverworts, which only grow in very wet places. Bryophytes are commonly found in rainforests and at high altitudes on mountains B. Division Pteridophyta (Filicinopyta)-ferns  They have true leaves, stems, and roots.  Fern stems have rhizomes, which grow horizontally just below the surface of the soil.  They have vascular tissue  They have large prominent leaves called fronds  Their spore produced in the fronds &dispersed by wind 34  They reproduce by alternation of generation(the sporophyte is well developed their gametophyte stage is reduced)  most ferns live in damp, shady places - they are very common in tropical rainforests   However, some ferns - such as Pteridium spp (commonly known as bracken) can grow and do well in full sunlight.  Another example of a pteridophyte is the fern Dryopteris spp. Ferns C. Spermatophytes(seed-bearing plants ) They are the most successful because of the following characteristic features that they possess: They have well-developed roots, stem and leaves. They have well-developed vascular tissues. The male gametes are contained within pollen grains and female gamete is contained within the embryo sac. The product of fertilisation in sexual reproduction is a seed that may or may not be enclosed in a fruit. The spermatophyta are divided into two divisions. These are: i. Division Gymnospermae(coniferopyta)- non-flowering plants ii. Division Angiospermae(flowering plants i. Division Gymnospermae(coniferopyta)- non-flowering plants These are more commonly known as the conifers or ‗naked seed plants‘. Pine trees, spruces and cedars ▲ The main characteristics of the gymnospermae are: Their seeds are not enclosed in fruits. They have small needle-shaped leaves with a thick waxy cuticle that reduces water loss and minimises damage by excess heat or cold. They are evergreen so they can photosynthesize all year long The reproductive structures are found in cones. They different types of cone. The male cone forms huge numbers of pollen grains that are blown by wind to a female cone. Fertilisation results in a small winged seed. The genus Pinus (for example, Pinus sylvestris, Pinus resinosa,) is a good example of a conifer 35  ii. Division Angiospermae(flowering plants)  They are the biggest group of land plants on the Earth. The main characteristics of the angiosperms are They have flowers as reproductive organs. They have their seeds enclosed in a fruit. They have well-developed xylem and phloem tissue Angiosperms are subdivided into two main classes according to the number of cotyledons they have in their seeds. These are: I. Class Monocotyledons (monocots)  are a group of enormous importance because they are cereal plants that form the staple diet The main characteristics of the monocotyledons are: The embryo has a single seed leaf (cotyledon). Leaves are generally long and thin with parallel veins. The stem contains scattered vascular bundles. They do not reach great sizes (palms are the exception to this). They are often wind pollinated Example grasses, orchids and maize. Maize& Teff II.Class Dicotyledons (dicots) They make up most of the trees, as well as many vegetable plants. The main characteristics of the dicotyledons are: The embryo has two seed leaves (cotyledons). The leaves are often relatively broad and have a network of veins. The stem contains a ring of vascular tissue. Some dicots reach great sizes. They are often insect pollinated.  Some common examples of dicots include sunflowers, peas, roses and beans. Most trees, such as Jacaranda, Eucalyptus, Cassia and mangos are dicotyledons. Shrubs include Hibiscus, Lantana camara, Bauhinia and oranges 5. Kingdom Animalia This kingdom includes the animals. There are at least two million species of animals alive today. They are multicellular, eukaryotic and heterotrophic 36 They exhibit locomotion, that is, can move their bodies from one place to another, and Their cells do not have cell walls.  They have nervous systems so they are sensitive to their surroundings. They are either invertebrates (not have a backbone.) or the vertebrates( - all the animals which have a spinal cord enclosed in a backbone of vertebrae) There are33 animal phyla but the main ones are 1. Phylum Porifera (the sponges) They are the simplest invertebrates. Most of them are hermaphroditic They have hollow filter feeders, and the body cavity is connected to its external environment by pores. There is little co-ordination or control. They range in size from a few millimetres to two metres and are supported by a calcareous spicules.  Sponges are an evolutionary dead end and have no other close living relatives 2. Phylum Coelenterata(cnidaria) They include some exceptionally beautiful creatures and also Some very poisonous ones. Sea anemones, hydra, jelly fish and coral are among the members of this phylum. They have soft bodies with a ring of tentacles for capturing prey. They have stinging cells on their tentacles for poisoning or immobilising prey and predators. They have two layers of cells in their bodies that surround a central cavity. They have only one opening, the mouth, and their bodies have radial symmetry Radial symmetry : is a body that can be divided into many halves. 3. Phylum Platyhelminthes - flatworms  They show a relatively high level of organization  They have flattened bodies with a mouth but no anus.  They have no body cavity and rely on diffusion for everything.  They are hermaphrodites  They live in other animals as parasites or are free-living in fresh water. Examples of Platyhelminthes include Planaria spp, which live in fresh water, tapeworms and liver flukes like Fasciola hepatica 4. Phylum nematoda(round worm) They have narrow, thread-like bodies, Their bodies are not segmented and are round in cross-section. They don’t have a circulatory system but they do have a complete digestive system. Bilaterally symmetrical. They contains many important parasites, such as Ascaris, which infects the guts of both humans and pigs, and the family Filariidae -which cause elephantiasis 5. Phylum Annelida(segmented worm) They have segmented body. They have a closed blood circulatory system. They are hermaphrodites, with male and female reproductive organs and 37 They have bristle like structures called chaetae to help them move. They are found in moist soil and water and most are free-living. The common earthworm, Lumbricus terrestris,& leech  Earthworm Snail (mollusc) e.g. of Echinoderms 6. Phylum Mollusca The most intelligent of the invertebrate species. Octopi and squid have well developed brains. They may have shells or be shell-less, live in the sea, or in fresh water or on land. They have a soft muscular foot with a soft body Their bodies are divided into head, foot and visceral mass and they are not segmented. They breathe through gills. Examples of molluscs include slugs and snails. 7. Phylum Echinodermata They are spiny skinned animals they have a mouth, a gut and an anus They are all marine animals, and move around using tube feet. The adults have five arms, but the larval stages do not. Examples include Asteris, the common starfsh, Echinus, the common sea urchin and Paracucumana tricolor, a brightly coloured sea cucumber known as a sea apple. 8. Phylum Arthropoda This phylum gets its name from two Greek words, arthron - joint, and podos - foot. They have an external exoskeleton made of chitin that prevents excessive water loss. They are animals with segmented bodies and jointed limbs. They have a well-developed nervous system and a complete gut from the mouth to anus. They divided into a number of classes according to the number of limbs, presence and number of antennae and number of body parts. Class insecta They live almost everywhere although most are land-based. They have a body divided into three body parts; head, thorax and abdomen. They have three pairs of jointed legs on the thorax along with one or two pairs of wings. On their head they have a pair of antennae and one pair of compound eyes. Insects include flies, butterflies and moths, beetles, wasps and bees and many other common groups. Class crustacea They are mainly aquatic. They vary in size from very small, for example water fleas, to quite large, for e.g. lobsters and crabs. Their body is made up of two parts - a cephalothorax (head fused with thorax) and abdomen. The body is often protected by a tough covering called a carapace. They have more than four pairs of jointed legs, two pairs of antennae and simple eyes. They include Daphnia, crab, prawn, shrimp, barnacle, water flea, lobsters, woodlice and crayfish. 38 Class chilopoda ( the centipedes )and the diplopoda (the millipedes) They both have long bodies with many segments and lots of leg  Centipedes Millipedes Have flattened bodies Cylindrical bodies Have brightly coloured bodies Dull-coloured bodies Have few or less segments Have more segments Have one pair of limbs per segment Have two pairs of limbs per segment Carnivorous (feed on other animals) Herbivorous Have poisonous claws for paralysing their prey Have claws for biting and chewing plant material Table 5.3 Differences between centipedes and millipedes Class Arachnida (the spiders) They are mainly terrestrial although some are aquatic. They have two body parts - a cephalothorax and the abdomen - with no antennae. They have eight legs in four pairs. They have simple eyes Spiders spin silken webs. Examples of arachnids include spiders, ticks, scorpions, and mites. 9. Phylum Chordata The term Chordata is derived from the term notochord Notochord flexible rod like structure of cartilage running along the dorsal side of the body. They have the following three features in common: They have a notochord at some stage of their lifecycle. They have a hollow nerve cord They have gill slits during early stages of development that are later replaced by lungs and gills. Vertebrates The chordates, the best known of which are the vertebrates (animals with vertebral column/backbone) In addition, they also have the following features: An internal skeleton (endoskeleton) made of bone or cartilage. A closed blood circulatory system consisting of blood vessels. A well-developed nervous system. Two pairs of limbs. Kidneys as excretory organs Phylum Chordata divided five classes i. Class pisces- fishes They are aquatic They have streamlined bodies with scales on their skin. They use gills for gaseous exchange and have fins for swimming They are ectothermic - they rely on heat from their environment to regulate their body temperature. Table 5.5 Differences between bony fish and cartilaginous fish Bony fish (teleosts) Cartilaginous fish(elesmobranches) Have bony skeleton Have cartilaginous skeleton Have round-shaped scales Have scales that are not round shaped Have opercula (gill covers) covering their gills Have no opercula (gill covers) but have gill slits Have homocercal tails (even size fins) Have heterocercal tails (one part is larger than the other) Are usually smaller in size Are usually larger in size e.g. Tilapia, Nile perch, mackerel and catfish E.g. Sharks, skates and rays. ii. Class Amphibia  Spend part of their lives in water and part of it on land.  They were the first vertebrates to colonise the land. 39  They have simple sac-like lungs (which are not very efficient) and smooth, moist skin  Their lifecycle includes metamorphosis, and they need water for successful reproduction as fertilization is external and the larval form (tadpole) is aquatic.   Gills are only present in the larval forms & they are ectothermic Example: frogs, toads, newts and salamanders Frog Toad Has a smooth skin Has a rough skin Has a moist skin Has a dry skin Has more webbed feet Has less webbed feet Has a brightly coloured body Has a dull-coloured body Has a more streamlined body Has a less streamlined body Has extra-long hind legs Has hind legs that are not extra long Table 5.6 Differences between a frog and a toad iii. Class Reptilia The reptiles are mainly terrestrial animals They have bony skeleton They have dry skin with scales and their gas exchange takes place exclusively in the lungs They have developed internal fertilisation Some reptiles even keep the eggs within their body and give birth to fully developed young. They are poikilothermic (ectothermic) & have no external ears Examples , snakes, crocodiles Two pair of pentadactyl limbs usually present iv. Class Aves(birds) Have skin that bears feather & scales on legs. Have bony skeleton Two pairs of pentadactyl limbs, front pair forms wings They are homoeothermic (endothermic) Example: domestic fowl, the wattled ibis, white collared pigeon and the Ethiopian eagle owl. v.Class Mammalia They are the best known of all animals Their skin bears hair , the skin consists of glands like sebaceous& sweat They produce live young which have developed for a time within the body of the mother in a structure called the uterus They have bony skeleton & Have external ear Have two pairs of pentadactyl limbs They use lungs for gas exchange A true mammal produces milk for its young in mammary glands Subdivisions of mammals Mammals are classified according to the way their young are produced. There are three sub-classes of mammals: i. Egg-laying mammals - lay eggs, e.g. duck-billed platypus. ii. Marsupials - produce immature young, which are nourished by milk in the pouch, E.g. Kangaroo, koala bear, opossum iii. Higher mammals - produce fully developed young, which are nourished by milk from the mammary glands, e.g. cows, elephants, cats, monkeys, and humans.  There are even flying mammals, as bats have been adapted to fly through the air on their leathery wings! UNIT 6 ENVIRONMENT 6.1. Ecosystems Ecosystem: all the animals and plants that live in an area along with the things that affect them. It is the home or habitat of the living organisms within it  Habitats may be on land - when they are known as terrestrial habitats 40 or they may be in water, when they are called aquatic habitats.