Grade 9 Biology Unit 4 Short Notes PDF

Prepared By: Mr. Simon Solomon Grade 9 Biology UNIT 4 Email:[email protected] 1 prepared by: Simon Solomon 13/12/2014  Unit 4 Microorganisms and diseases 4.1. Micro-organisms What is...

Prepared By: Mr. Simon Solomon Grade 9 Biology UNIT 4 Email:[email protected] 1 prepared by: Simon Solomon 13/12/2014  Unit 4 Microorganisms and diseases 4.1. Micro-organisms What is 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. prepared by: Simon Solomon 13/12/2014 2 By the end of this section you should be able to: Define micro-organisms and list the main types. Explain the useful and harmful effects of some micro-organisms. Explain how vaccines are made, how they work and their importance. Distinguish between disinfectants, antiseptics and antibiotics. Describe the methods used to control micro-organisms. Describe how to grow a bacterial culture and show simple staining methods of micro-organisms. Explain Explain how vaccination works and evaluate the impact of vaccination on diseases in Ethiopia 3 prepared by: Simon Solomon 13/12/2014 Bacteria  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 Some are rod-shaped, some are round, some are comma-shaped and some are spirals.  some bacteria cause disease, many are harmless and some are actively useful to people. 4 prepared by: Simon Solomon 13/12/2014 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. 5 prepared by: Simon Solomon 13/12/2014 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. 6 prepared by: Simon Solomon 13/12/2014  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.  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. 7 prepared by: Simon Solomon 13/12/2014  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. 8 prepared by: Simon Solomon 13/12/2014 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. 9 prepared by: Simon Solomon 13/12/2014 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. A disinfectant is a chemical or physical agent that is applied to an inanimate object to kill microorganisms. 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 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 10 prepared by: Simon Solomon 13/12/2014 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 11 prepared by: Simon Solomon 13/12/2014 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/drugs. 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 It has long-lasting effect on the body 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. 12 prepared by: Simon Solomon 13/12/2014 vaccination(immunization) Vaccine 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.\  If you are vaccinated with antibodies against a disease you will have temporary passive immunity. A baby gets natural passive immunity from its mother. Antibodies from the mother pass into her fetus across the placenta. Many more antibodies are passed to the baby through breast milk, protecting the baby in its early months of life. 13 prepared by: Simon Solomon 13/12/2014  4.2. Diseases By the end of this section you should be able to: explain the role of parasites in causing disease. Describe the causes, symptoms, methods of transmission, prevention and control of a tapeworm infection. List the causes of tuberculosis, AWD, cholera and typhoid, and describe the signs and symptoms of these common infectious diseases. Explain how tuberculosis, AWD, cholera, typhoid and gastroenteritis are spread from one person to another and the methods of prevention and controlling them. Define the term vectors. State signs and symptoms, causative agents, methods of transmission, methods of limiting spread and possible treatment of the following infectious diseases: gonorrhea, syphilis and chancroid. 14 prepared by: Simon Solomon 13/12/2014 Disease is any form of disorder in or on the body distorts it’s 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 15 prepared by: Simon Solomon 13/12/2014 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 bladder worm 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. 16 prepared by: Simon Solomon 13/12/2014  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  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, - weight loss night sweats, fatigue and - a persistent cough Control and prevention In social terms avoiding overcrowded conditions - Good ventilation Covering the nose &mouth during coughing - Vaccination Treatment: people with active TB disease must complete antibiotic for four months or more 17 prepared by: Simon Solomon 13/12/2014  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 18 prepared by: Simon Solomon 13/12/2014 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 19 prepared by: Simon Solomon 13/12/2014 iv. Gastroenteritis/acute watery diarrhoea (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 and poorly cooked and raw eggs if they are infected with bacteria such as Salmonella symptoms : violent abdominal cramps and pain feeling nauseous, vomiting or often both watery diarrhea which does not usually have blood in it slight fever and general muscle aches and headache Control and prevention - Good personal hygiene - Avoid eating undercooked or raw food 20 prepared by: Simon Solomon 13/12/2014 V. Cholera It is caused by bacteria called Vibrio cholera & it infects intestine Transmission: eating or drinking food or water contaminated by the fecal waste of an infected person Symptoms : include the pale, watery diarrhea, vomiting and dehydration, muscle scramps 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 , Taking cholera vaccine Good personal hygiene and environmental sanitation 21 prepared by: Simon Solomon 13/12/2014 Vi. Typhoid (Typhoid fever) It 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 food 22 prepared by: Simon Solomon 13/12/2014 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)  Is caused by the bacterium Neisseria gonorrhoeae.  Gonorrhea germs are found in the mucus areas of the body (the vagina, penis, throat and rectum).  Transmission :It is spread through sexual contact, Having unprotected sex, having many sexual partner  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 23 prepared by: Simon Solomon 13/12/2014  Treatment: it can be treated effectively in the early stages using antibiotic  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 for the baby when it is born.  Symptoms: Syphilis progresses in distinct stages  The symptoms occur in stages called primary, secondary and tertiary (late) 24 prepared by: Simon Solomon 13/12/2014 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 t: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& 25 control: similar with gonorrhea prepared by: Simon Solomon 13/12/2014 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 Prepared by: Mr. Simon Solomon 26 prepared by: Simon Solomon 13/12/2014 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: T-cells actually bind to the antigens on the invading micro-organism and destroy it. 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 27 prepared by: Simon Solomon 13/12/2014  Prepared by: Mr. Simon Solomon 28 prepared by: Simon Solomon 13/12/2014