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Transcript of Pesticide
(answer to #2 for 4.4 pg 134)
compete or damage crop species
therefore reducing crop yields
there are no pests in nature, just a reference to human wishes; all organisms are producers and consumers within food webs
(Answer to # 6 for 4.4 pg 134)
eg: weeds are plant pest, mice are rodent pest A pesticide is a substance used to kill a pest. Pesticides differ in terms of the number of species they are able to control:
Broad-spectrum pesticide: a pesticide that is effective against many types of pest
Narrow-spectrum pesticide: a pesticide that is effective against only a few types of pest
e.g DDT (dichlorodiphenyltrichloroethane), an insecticide, is toxic to most insects
natural pesticides are better than sinthetic pesticides because they are less persistant.
(answer to #5 for 4.4 pg 134)
(answer to #4 for 4.4 pg 134) How do pesticides work? Pesticides work by causing physical or biological harm to the pest organism. While some pesticides are delivered by contact, others are indirectly applied.
Example of biological harm: pesticides that interfere with biological processes such as photosynthesis
An indirect appliance:
Insecticides can be sprayed on a certain plant, then later consumed by an insect.
Target pest must be touched by the pesticide. Maybe even your siblings..? What are pests? 4.5 Issues with Pesticides Non-target species Pesticides often kill species that were not meant to be killed such as organisms that are not threatening, but beneficial to the environment.
Improper use of pesticides can also kill non-target species
for example: spraying insecticides at the wrong time of year may kill honeybees
honeybees are vital for pollinating fruit crops, resulting in less fruits being produced
Consequences of non-target species may be severe Organisms at this high level are much more likely to suffer toxic effects. There are 5 different types of pesticides: insecticides, herbicides, rodenticides fungicides, molluscicides
(Answer to # 3 for 4.4 pg 134) Pesticides have dramatically increased global food production. However the disadvantages of using pesticides are:
causes harm to non-target species
bioamplification (increase in concentration of a substance)
Therefore, an alternative solution of agriculture is organic farming.
organic farming: the system of agriculture that relies on non-synthetic pesticides and fertilizers.
Organic farmers rely on a range of ecologically sustainable techniques.
Organic framing reduces environmental impacts, but it could result in lower crop yields. Therefore an intermediate approach called integrated pest management is employed.
integrated pest management (IPM): a strategy to control pests that uses a combination of physical, chemical, and biological controls
This goal is to maximize efficiency, keep costs low, and reduce harm to the environment.
(answer to #9 for 4.5) Arctic ecosystems are more prone to biomagnification of toxic substances. Consumers such as whales, polar bears and walruses have habitats in the Arctic.
Therefore Inuits that live within these environments and depend on these animals for food, are in a dangerous situation to toxic exposure. Reducing Our Dependence on Pesticides Pesticide Resistance When pesticides are used for a long time, pest species build an immunity to the chemicals and therefore become resistant.
These pesticides are no longer capable to control the pests. Organisms that are resistant will reproduce and pass on their immunity to their offspring.
This increases the farmer's dependency on pesticides, creating a situation where a greater concentration of pesticide needs to be used or a different use of pesticide. 4.4 Questions 1. Lack of biodiversity is the unusual characteristics of food webs in agroecosystems
3. The loss of non-target species lead to a greater use of pesticides because beneficial organisms are killed and cannot control the population of other pests. This results in farmers using more pesticide to make up for the lost organisms.
5. There are synthetic pesticides and natural pesticides. Usually natural sources are better than synthetic pesticides because they are less persistent.
7. Population of pest are likely to be larger in agroecosystem that they would be in natural because large monocultures found in agroecosystem create ideal environment for particular herbivores; monoculture single, large source of food for pest and also low biodiversity so there are few predators that prey on pests.
8. Both insects and weeds compete with crops that are valuable to us. Their populations increase rapidly, consume and destroy large quantities of plants. Weeds prevent us from growing crop yields. Bioamplification Bioaccumulation: the concentration of a substance, such as a pesticide, in the body of an organism one of the most serious side effects of pesticide is their tendency to accumulate in organisms
this occurs because some pesticide is not broken down or eliminated with body waste
pesticides that bioaccumulate do so due to that they are unable to exit from the body-they are not soluble in water but are soluble in fat and oil--bioaccumulation
(answer to #4 for 4.5) 4.5 QUESTIONS 3. The loss of non-target species lead to a greater use of pesticides because beneficial organisms are killed and cannot control the population of other pests. This results in farmers using more pesticide to make up for the lost organisms.
4. Pesticides bioaccumulate because they cannot be easily excreted from the body. Some pesticides bioaccumulate because they are soluble in fats and oils, but not in water.
5. DDT, a pesticide, accumulates in the food chain. DDT bioamplifies because the chemicals are being stored in organisms. Small organisms consume micro-organisms that absorb the pesticides in large quantities. Since the pesticides are retained within the organisms, they keep building as the food chain continues. Therefore, it accumulates in the top consumer. Ex. micro-organisms --> shrimp --> smelt --> herring
7. Pesticide resistance is a major concern because pests are able to withstand pesticides and destroy crops. The resistance level keeps increasing with each generation.
8. There are many alternatives to the widespread use of pesticides. Some alternatives are:
Biological control - allowing nature to take it’s course. Allowing predatory insects, mites, and disease causing micro-organisms to prey on and infect species of pests.
Crop rotation - when farmers do not grow monocultures in the same location year after year, pest populations do not have the same opportunities to prosper.
baiting pests - pheromone baits can be used to confuse some mating insects.
9. Integrated pest management is using physical, chemical, and biological farming methods. It is used to reduce environmental impacts while being more efficient. Integrated pest management is an approach that lowers costs and incorporates farming methods of organic and conventional farmers.
10. Organic methods do not use synthetic pesticides and rely on predation to rid of pests. Organic farming uses the relationships in natural ecosystems to control pest populations. In addition, organic methods make use of biological materials to support crop yields. For example, compost is a great fertilizer.