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National 5 Assignment – Biology

National 5 Assignment – Biology

Aim

To find out why the population of bees is declining due to insecticides.

Insecticides

What are they? An insecticide is a type of pesticide used to prevent insects from eating plants and crops. Once an insect has consumed a plant that has insecticide on it, it is likely to die.

Why are they used? Insecticides are used in many different ways. They are mainly used in agriculture to protect plants from being eaten. Insecticides are a major factor behind the increase in in fresh-farm produce in the 20th century. The increase in crop yield is due to the fact that insecticides protect the crops from defoliation and diseases. There are several other reasons why they’re used, however. Insecticides can be used in order to prevent spoilage of certain food products. Insecticides can even prevent certain diseases. This conserves health and has saved the lives of thousands of people and domestic animals that consume certain types of crops. It is estimated that pests destroy over 37% of the potential yield of plant crops in North America alone. Much of this damage can be prevented by using insecticides. Insecticide spraying is also one of the crucial tools used to reduce the ever-irritating pest known as the mosquito as well as other insects that carry certain diseases (such as malaria) to humans. The use of insecticides as a form of population-control for certain vectors has managed to prevent people from harbouring diseases which can prove to be harmful and, in some cases, fatal.

This doesn’t mean that more insecticide use would yield further benefits. It’s been argued in great detail that pesticide use in North America could be decreased by up to 50% without causing a substantial decrease in crop yield. Sweden, Denmark & Holland passed legislation in the 1990s requiring at least a 50% reduction in agricultural pesticide use by the start of the millennium. Similar legislation may eventually be enacted in North America and other parts of the world.

Due to the vast benefits of insecticides, their use has increased enormously since the 1950s. For example, insecticide usage increased 10-fold in North America between 1945 and 1989. This didn’t last however; usage levelled out during the 1990s. Insecticides are now a fairly integrated part of the technological systems used in agriculture and forestry as well as various other industries.

Why are they harmful to the environment? Insecticides can greatly alter ecosystems; many of these chemicals are also toxic to humans. The majority of these insecticides concentrate along the food chain, causing bio-accumulation which is very damaging to certain organisms, bees included.

Honey Bees

What niche do they have in the environment? According to the U.S.D.A, honey bees pollinate around 80% of flowering crops, which contribute to about one-third of everything that we consume. Losing many more honey bees could affect not only dietary staples such as apples, broccoli, strawberries, blueberries and cucumbers; it may also threaten our beef and dairy industries if Lucerne is not readily available for feed. A study recently done by Cornell University estimated that honeybees annually pollinate around $14 billion worth of seeds and crops in the United States. In other words, if honeybees were to disappear entirely, they could take most of the pollinated plants with them. This, potentially, could reduce mankind to little more than a water based diet.

Honey Bees can be considered as ‘agents’ of cross-pollination. Many plants are entirely dependent on bees for reproduction. Insecticides for agricultural pest control have had a damaging effect of harming and potentially killing bees which are necessary for pollination of crops. Parasites also have a damaging impact on bees. Parasitic mites devastated populations of honey bees in the United States during the early 1980s. This meant that farmers often had to rent honey bees from beekeepers in order to ensure that their crops were pollinated.

What environmental factors affect the population?

Environmental activists have claimed that ‘stressors’ are causing the decline in bees: Farmers tend to grow crops that are likely to generate more revenue. This method of farming has decreased biodiversity in wild plants. These are plants that the bees like to feast upon. As a result, large amounts of wild bees have declined and it appears that this will carry on until further notice. With nearly every acre of land being put to use in the farming, hedges and bushes that are generally used for feeding cannot be utilised by subsequent bee populations. As Bee hives are transported across continents for commercialised pollination, they are exposed to foreign climates and living conditions for a short period of time. Changes like this have a damaging impact on the bees and, as a result, have been responsible for the bee decline; changes in climate prevent the bees from foraging effectively.

Impact of insecticide use on honeybee

There are some pesticides that directly kill the honeybees. This occurs when bees are on the flowers during the time when the pesticide is being applied. This results in the bees dying instantly. Certain types of pesticide prolong the deaths of the bees; they are able to return home, but their death is almost inevitable. There are a few pesticides that will not harm adult honey bees, but when a young be comes into contact with it, it will likely damage the bee.

There are two pesticides that are commonly used in modern framing which could damage the honey bee population: neonicotinoids and coumaphos. These pesticides target the bees brain which results in a slow learner. This, in turn, causes the bee to forget floral scents. These two pesticides coupled together have a greater effect than when they are individually applied. Honeybees that were exposed to multiple pesticides were incredibly slow to learn and they sometimes lost their ability to associate nectar and floral scents.

Neonicotinoids are relatively new; they target the bees’ central nervous system. Neonicotinoids are the most commonly used form of insecticides in the United States. Studies have shown that bees that feed on neonicotinoid contaminated pollen and nectar are likely to forage less and they generally produce fewer offspring. Coumaphos is an insecticide that is used in honey bee hives in order to kill a parasite called ‘Varroa’. Conclusion

In conclusion, insecticides are incredibly useful in increasing crop yield as well as protecting flowering plants from insects. However, insecticides are very damaging towards the bee population, and we must take precautions to ensure that we don’t wipe out the honeybees enmasse.