Question

1) do you think that parasites and pathogens have the potential to control natural populations significantly? Why? How?. Provide an example. (min. 300 and max 500).

Please do not copy and paste from other sources!! Thanks

Answer 1

Pathogens and parasites can control natural populations because of their ability to cause disease and destroy the host. MOre pathogens in a region will not allow the host population to reach its maximum density in a habitat. So the parasites can be like controlling agents. When the number of host individuals go beyond certain levels, the pathogen survival also is at stake. So there is always increase and decrease of the host and parasite populations. Parasites always keep the host population lower than the carrying capasity of the habitat.

This can be applied to control certain weeds in a given habitat. Or it can also can be used to kill certain insect pests.Bacillus thuringiensis is a bacterium which produces Bt toxins. There are about 200 toxins produced by these bacteria. Each destroying a different plant pest. The bacterium can be sprayed on to the plant in the form of spores. These spores grow in to new bacteria. The bacteria do not kill the insects. But they destory the insect larva with the help of their toxins. The toxin(Bt toxin) causes pores in the gut of the insect larva and hence kills the insect larva. This is how we can control the insect population growing on the plants. The pathogen host relation can be used to protect certain plants from their pests as it is shown in this example. The toxin produced by the bacterium also can be sprayed on the plants to control the growth of the boll worm. The toxins only affect when the conditions are alkaline. Acidic conditions that are seen in the human stomach will not activate the Bt toxin. So the toxin will not have any effect on the humans and hence it can be used as pest control measure for many vegetable crops such brinjal, tomato etc. The toxin released by the bacterium is not harmful to the environment because acidic soils degrade the toxin and also the other bacteria can digest and destroy the toxin.

Cochineal insects feed on catus like Opuntia and destroy the plant. Where the cacti are growing wild, these insects can be used to control the population of the cacti. So the pathogens or the parasites do control the natural population size in a habitat and this relation can be used to control certain pests in the habitat.