Question 6: Evolution Evolution, through natural selection, chooses traits that

Question

Question 6: Evolution Evolution, through natural selection, chooses traits that increase the reproductive fitness of the organism. In other words, if some members of a population have trait X, and if trait X means that they produce more offspring that survive to maturity and reproduce, then trait X will become more common in the population. Given this deinition of evolution, consider each of the interaction categories (competition, commensaism, predation, parasitism, herbivory, or mutualism). Predict how each of the species in the interaction might evolve. For example, a parasite might evolve to become less virulent so that it doesn't kill so many of its host. Did you predict that in each interaction there would be an evolutionary pressure to reduce negative effects or increase positive effects? Those predictions make sense, but why, after 3.5 billion years of evolution, do we still have interactions with negative effects?

Explanation / Answer

Competition: Interaction between two species where both suffer adverse effects. Competition usually occurs when resources such as space, light and nutrients are limited. It may be interspecific or intraspecific. It is a negative interaction but are necessary to keep the species under control. Bothspecies evolve in a such way to survive the competition.

Commensalism: It is a relationship between two species where one species is benefited while the other neither gets any benefit nor is adversely affected under normal conditions. Since both can survive together without any negative effect, it is possible that they evolve together because the species that gets benefit from the other species with which it is living, will extict if the species with no effect extinct.

Predation: Interaction between species involving killing and consumption of prey is called predation. The species which eats the other is called predator and the one which is eaten is called prey. It is a herbivore -carnivore interaction. This negative effect helps the prey population under check.

if the predator over exploits the prey and consumes more prey leads to reduction of prey population which in turn reduce the population of predator also due to starvation and emigration. The reduction in predator population increases the prey population as they are not preyed upon and also increases intraspecific interaction and reduces the prey population. Both evolve and a stability is maintained between prey-predator population.

Parasitism: In this interaction, the species smaller in size lives in or on the larger species (host) and obtaines its food from its host. Parasites may alter the population growth of the host, shorten the life cycle, weaken the host and drastically reduce the reproduction by the host.

Herbovory: Herbivores directly depend on the plants and plant products. But herbivores are important to the next trophic level that is secondary consumers or primary carnivores. Hence any disturbance in the herbivory lead to the negave effect on primary carnivores.

Mutualism: An association of two species, in which both species are benefited. It may or may not involve close physical association between the individuals of pairs of species. Both try to evolve in such way which is beneficial for both. Because the life cycles of the organisms of one species depends on the other. and it is important for co-evolution. Extinction of one species leads to extinction of other species.

In each interaction, there is necessity to reduce the nagative effect so that an ecological stability is maintained. Interactions which have negative effect continue because, they help to keep the other species under control without which there will be an ecological instability.

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