Biology Notes Essay Example

Biology Notes Essay Example Biology Notes Essay Biology Notes Essay ACT Friday, 24/04/2009 Citrus trees are dying in Indonesia. The cause is citrus greening disease, a bacteria spread by insects. Australia is in real danger of catching the bug, with scientists suggesting it might blow on the wind, or fly in with a tourist. Australias biosecurity protection is one of the reasons our country has the massive commitment to aid in Indonesia. Citrus greening disease has already spread in the US, most recently into the orchards of South Carolina. On the populous island of Java, farmers should now be harvesting their small mandarins called jeruk but most trees have been pulled or are diseased. Citrus greening or Huanlongbing as its known in Asia was first found in the 1950s on one of the Indonesian islands, but its rapid spread over the past 10 years has surprised researchers at Gadja Mada University. Its a bacterium is spread by the psyllid insect and it destroys the phloem cells, the veins that carry sugar and nutrients throughout the plant, leaving the fruit barely edible. The fruit becomes abnormal, and more sour and hard, says Dr Siti Subandiyah, the Indonesian project leader on the Australian Centre for International Agricultural Research, (ACIAR) project based at Gadja Mada University in Jogjarkarta. Within just a few years the tree dies and there is no cure, so prevention is the main course of action being taken by the extension staff. Huanglongbing disease is also destroying citrus in Vietnam, so the ACIAR project has partners in Vietnam too. Meanwhile Australia should be on alert for the psyllid insect carrying the bacteria- which could devastate citrus production in Australia too. HSC Biology 9. 4-6 Page 13 A case study Quarantine and the spread of plant and animal diseases within Australia South Australia grows approximately 42 per cent of the annual Australian vine crop and produces more wine than all other States combined. One reason for South Australias viticultural success is that grape phylloxera (pronounced fil-er-a), the worst insect enemy of grape vines, has never been introduced into the State. Since 1899, quarantine regulations have forbidden the introduction of any part of a vine into South Australia. Quarantine of grapes, grapevines and grape rootstock is necessary to protect Australias wine and dried fruit industry from grape phylloxera. Grape phylloxera exists in most of the grape growing areas of the world. It does not occur in most grape growing areas of Australia. Phylloxera appeared in France in 1869, and within 30 years destroyed 75 per cent of the vineyards of this most important wine-producing country. By 1919, people carrying.\Â  infested parts of grape vines to clean areas had spread phylloxera to most wine-growing countries in the world, including the eastern States of Australia. Only Chile and Cyprus and two Australian States South Australian and Western Australia continue to grow European vines in soil that is free of phylloxera. Travellers carrying grapes or parts of vines could easily cause an outbreak of grape phylloxera in South Australia or Western Australia or re-infest other grape growing areas in Australia where phylloxera has previously been eradicated. An outbreak of grape phylloxera in the early 1900s in areas of Victoria and New South Wales caused widespread damage to the Australian grape industry. HSC Biology 9. 4-6 Page 14 Its an aphid Grape phylloxera is an aphid or plant louse. It is native to the eastern States of North America. Over the centuries, American vines have developed a resistance to it. Wherever phylloxera has appeared, European vines have been grafted on to the resistant American rootstocks. The tiny insects are too small to be seen without a microscope. They have a soft body and a tube-like mouth that they use to suck the sap of vine roots. This sucking causes hard round swellings, called galls, to form on the vine roots. A few months later, the galls decay, damaging, stunting and eventually killing the vine roots. A fertile aphid The reproductive power of the species is almost impossible to imagine. It has been reported that the offspring in one season from one egg may total 40,000 million aphids. Aphids may be present in soil clinging to vehicle wheels, footwear, cultivating equipment, picking boxes and, most likely of all, vine roots. Residents of South Australia visiting interstate vineyards should take care not to transport phylloxera back into South Australia. With the benefits of continuous research into grape growing, the South Australia Phylloxera Board has kept grape growers aware of phylloxera and its disastrous consequences should it ever be introduced. Not only would whole vine-growing areas be wiped out but it would also affect South Australias dried vine fruit industry and wine industry, currently a major export earner for the State. HSC Biology 9. 4-6 Page 15 Quarantine precautions Overseas travellers should never bring grapes or any parts of vines into Australia. The only safe method of introducing plant and vine material is through AQIS. The movement of grapes, grapevines and cuttings between the States and Northern Territory is either very restricted or, in most cases, prohibited. There are also restrictions on the interstate movement of various other fruit, vegetables and plant material designed to prevent the spread of pests and diseases to clean areas. Has quarantine been entirely successful in preventing the entry of grape phylloxera into Australia? Has quarantine within Australia been successful? When equine flu entered Australia in 2007, infected horses were found in New South Wales and in Queensland. Quarantine measures were enacted to prevent the transport of horses to regions that were free of equine flu. Equipment was disinfected, horse racing events were cancelled and animals at risk were vaccinated to prevent the disease from spreading. Because of the measures put in place, Victoria remained free of equine flu and there has not been another outbreak. HSC Biology 9. 4-6 Page 16. Evaluate the effectiveness of quarantine The greatest quarantine risks are plants, plant products, animals, animal products and soils. All items that pose a quarantine risk can carry hidden plant or animal diseases. At airports or shipping terminals, as well as at mail centres, prohibited goods are intercepted by AQIS. Quarantine checking stations are also set up across both State and agricultural region borders to intercept produce that may be a quarantine risk. The table below shows interceptions of goods and personal effects entering Australia, 1996 – 1998. Year 1996 1997 1998 Interceptions 5121 10 952 15 060 What do these figures suggest about the effectiveness of our quarantine service? Is it likely that all prohibited goods were intercepted? Suggest some reasons why quarantine would fail to intercept all prohibited goods. HSC Biology 9. 4-6 Page 17 To evaluate the effectiveness of quarantine in preventing the spread of plant and animal diseases into Australia or across regions of Australia, you firstly need to decide on criteria on which to base your judgement. What information do you need before you can make a judgement about the effectiveness of quarantine? You will need to show ways that the Australian Quarantine Inspection Service (AQIS) has successfully prevented the introduction or spread of diseases, and examples of failure. Identify examples of quarantine successes in preventing the entry of plant and animal diseases into Australia. Identify examples of quarantine successes in preventing the spread of plant and animal diseases across regions of Australia. Identify examples of quarantine failures in Australia. Read the article from the World Health Organization (www. who. int/csr/don/2004_01_15/en/) HSC Biology 9. 4-6 Page 18 Avian Influenza The disease in birds: impact and control measures Avian influenza is an infectious disease of birds caused by type A strains of the influenza virus. The disease, which was first identified in Italy more than 100 years ago, occurs worldwide. All birds are thought to be susceptible to infection with avian influenza, though some species are more resistant to infection than others. Infection causes a wide spectrum of symptoms in birds, ranging from mild illness to a highly contagious and rapidly fatal disease resulting in severe epidemics. The latter is known as highly pathogenic avian influenza. This form is characterized by sudden onset, severe illness, and rapid death, with a mortality that can approach 100%. Migratory waterfowl most notably wild ducks are the natural reservoir of avian influenza viruses, and these birds are also the most resistant to infection. Domestic poultry, including chickens and turkeys, are particularly susceptible to epidemics of rapidly fatal influenza. Direct or indirect contact of domestic flocks with wild migratory waterfowl has been implicated as a frequent cause of epidemics. Live bird markets have also played an important role in the spread of epidemics. Recent research has shown that viruses of low pathogenicity can, after circulation for sometimes short periods in a poultry population, mutate into highly pathogenic viruses. During a 1983-1984 epidemic in the United States of America, the H5N2 virus initially caused low mortality, but within six months became highly pathogenic, with a mortality approaching 90%. Control of the outbreak required destruction of more than 17 million birds at a cost of nearly US$65 million. During a 1999-2001 epidemic in Italy, the H7N1 virus, initially of low pathogenicity, mutated within 9 months to a highly pathogenic form. More than 13 million birds died or were destroyed. HSC Biology 9. 4-6 Page 19 The quarantining of infected farms and destruction of infected or potentially exposed flocks are standard control measures aimed at preventing spread to other farms and eventual establishment of the virus in a countrys poultry population. Apart from being highly contagious, avian influenza viruses are readily transmitted from farm to farm by mechanical means, such as by contaminated equipment, vehicles, feed, cages, or clothing. Highly pathogenic viruses can survive for long periods in the environment, especially when temperatures are low. Stringent sanitary measures on farms can, however, confer some degree of protection. Could migratory birds carry avian influenza to Australia? Explain What impact would this have on the effectiveness of Australian quarantine control? Use all of the previous information to make a judgement of the effectiveness of quarantine in preventing the spread of diseases into Australia OR across regions of Australia. Give reasons for your decision. (Hint: Using a plant and an animal disease example, describe the quarantine measures in place, explain how these measures assist in preventing the spread of disease into Australia or across regions of Australia, and, make a judgement about the effectiveness of the quarantine measure, which can be supported by data on the occurrence and spread of the disease. ) HSC Biology 9. 4-6 Page 20 Strategies for disease control and prevention There are several strategies for the control of preventable diseases. These include vaccination and quarantine. Three other strategies are public health programs, pesticides, and genetic engineering to produce disease resistant plants and animals. We will briefly look at all three of these, but concentrate on one, public health programs. Public health programs Public health programs provide sanitation, safe drinking water, immunisation programs and even the quarantine of disease sufferers entering the country. These have all played a part in disease control. You may accept a safe water supply as a fact of life, but that has not always been the case in Australia and certainly is not the case in many other countries. One of the first things aid agencies try to establish when working in these countries is a safe water supply. A classic epidemiological study was performed by English physician John Snow. He found that people who suffered from cholera in the 1849 London epidemic lived mostly in the area of the Broad Street pump. Water was collected daily from village pumps or wells. Snow found that nearly every person with the disease had consumed water from the Broad street pump. He had the pump closed and no further outbreaks occurred in the area. HSC Biology 9. 4-6 Page 21 Read the article The Development of Public Health and answer the questions below. Compare the age of death in Leeds with the age of death in a country area in 1842. What were living conditions in Leeds like in 1842? What were the main causes of death in Leeds? How are these diseases spread? Cholera and typhus epidemics in Leeds prompted some improvement. What was the government response? The Public Health Act in 1875 compelled Councils to improve what? What diseases were reduced as a result? How do improvements in housing reduce the incidence of tuberculosis? How do vaccination programs reduce the incidence of disease? HSC Biology 9. 4-6 Page 22 Modern public health programs Because you have probably seen TV advertisements showing the gruesome effects of smoking, sun exposure and alcohol you may be aware that health programs have been set up in NSW to prevent and control human disease. While pathogens are not implicated in non-infectious diseases, health strategies also target these diseases and aim to reduce their incidence. Methods used by NSW Health include public education such as advertisements about the health effects of alcohol, smoking (remember the ‘Quit’ campaign) and of having unprotected (without a condom) sex; mass immunization procedures such as for MMR (measles, mumps, Rubella) or Human Papilloma virus in schools; screening for high blood pressure, cervical cancer and breast cancer (BreastScreen NSW provides free mammograms to those over 50); and laws requiring that certain diseases such as HIV/AIDS are notifiable (there are penalties for not notifying public health units within 24 hours) or that people with other diseases such as rubella and chicken pox must be isolated. The table below shows some examples of notifiable diseases. To be notified by doctors HIV/AIDS Food poisoning (two or more cases) Gastroenteritis (in educational or residential institutions) Measles TB To be notified by laboratories Anthrax Giardiasis Hepatitis Malaria Influenza Rubella To be notified by hospitals Cholera Legionnaire’s disease Meningococcal disease Poliomyelitis Rabies Tetanus To be notified by school principals Diphtheria Measles Mumps Pertussis Poliomyelitis Rubella HSC Biology 9. 4-6 Page 23 Compulsory notification ensures early detection of these diseases so that strategies can be put in place to control the spread of the disease. Government regulations ensure that garbage is collected and disposed of correctly, sewage is removed and treated and water supplies are protected. Government regulations also ensure that safe procedures are in place for the handling, storage and preparation of food and for disease control in hospitals. Identify a public health strategy and explain how it can control or prevent disease. HSC Biology 9. 4-6 Page 24 Pesticides Pests are organisms that affect the normal growth of a plant or animal. For example, the cotton bollworm is a pest that can devastate a cotton crop, and ticks are pests that can affect the health and growth of cattle. Mosquitoes are pests because they can transmit diseases like malaria. Agricultural pests can be controlled by the use of pesticides or by biological control. Pesticides include insecticides that kill insects, fungicides that kill fungi, and herbicides that kill weeds. Because pests can kill or stunt food plants, the use of pesticides has been critical in contributing to the quality and quantity of food production. Since they are cheap, pesticides have been the preferred method of pest control but there have been serious environmental problems associated with the use of pesticides. Some long-term effects include: Pests have evolved resistance to some pesticides Non-target organisms are killed Toxic residues accumulate in food chains Farm workers can be poisoned by contact with pesticides Pesticides have been important in killing disease vectors, such as mosquitoes. You will remember the earlier section of work on malaria and how the malarial parasite, Plasmodium is transmitted by mosquitos. Malaria can be controlled by spraying with pesticides to kill mosquitos. Adult mosquitoes are killed by pesticides such as DDT or dieldrin. Beginning in 1956, the World Health Organisation began a campaign using DDT for mosquito control in malarial areas. This campaign successfully controlled malaria in Sri Lanka and other areas of the world but did not eliminate it globally. DDT resistant mosquitoes are now a problem in many areas. Insecticide-treated bed nets, which can reduce the transmission of malaria by 17% are cheap and effective ways to prevent people from getting malaria, but only 4% of Africa’s children sleep under one each night. HSC Biology 9. 4-6 Page 25. Biological control has been an effective alternative to the use of pesticides in some situations. Genetic engineering Genetic engineering is the purposeful manipulation of genetic material to alter the characteristics of an organism. Genetic engineering (and plant breeding) has been used to develop crops that are resistant to certain diseases. Rust resistance in wheat is an example of breeding being used to develop disease resistance. Genes from the bacteria Bacillus thuringiensis has been genetically engineered into cotton plants to eliminate the need for spraying for cotton bollworm caterpillar, Heliothis. Many predator insects feed on Heliothis caterpillars, so spraying with insecticides is not ideal. The Bt genes that produce the toxin responsible for caterpillar death have also been introduced into tomatoes, corn and potatoes. In Australia Bt cotton was the first genetically engineered crop grown. Cattle ticks cause significant economic loss because heavy infestation by ticks reduces the growth rate of cattle and ticks can also cause disease. Ticks are normally controlled by dipping the cattle in baths of pesticide, but these are toxic and can remain in meat. Genetic engineering has now been used to produce an anti-tick vaccine for cattle. Insulin produced by recombinant DNA technology and is another example of a strategy to fight disease by genetic engineering. HSC Biology 9. 4-6 Page 26 Read the Scientific American article Seeds of Concern abou.