Organisms and Populations Test - 78

The global population growth was very slow until the 1750. There was a long period of stationary growth phase, with the world's population about 300 million. But after 1750, the world's population grew significantly. 

Biotic potential is the maximum reproductive capacity of a population under optimum environmental conditions. 

In 1972, the forest department realized its mistake while reviving the degraded sal forests of Arabari forest range. Arabari forest lies in Midnapore district of West Bengal. The earlier methods of policing and surveillance were a total failure as they often led to frequent clashes with local people. It also led to alienation of people from the conservation programme. Then a forest officer, named A K Banerjee involved the local people in the revival of 1,272 hectares of forest. In lieu of that the villagers were given employment in silviculture and harvest and were given 25% of the harvest. They were also allowed to gather firewood and fodder against a nominal payment. Due to active participation of the local community there was remarkable revival of the Arabari sal forest. By 1983, the value of the forest rose to Rs. 12.5 crores.

Herbivores are the group of animals that derive their nutrients from plants and plants products. With 25-30% of the insect species the largest animal group on earth being herbivorous, the green plants manged to survive. While the green plants have evolved a number of adaptations to survive the impact of herbivores, the population of terrestrial herbivorous arthropods are kept under control by high order predators.

Total primary production in an ecosystem is known as the ecosystem's gross primary production (GPP). 

When bacteria are placed in a medium that provides all of the nutrients that are necessary for their growth, the population exhibits four phases of growth that are representative of a typical bacterial growth curve. Upon inoculation into the new medium, bacteria do not immediately reproduce, and the population size remains constant. During this period, called the lag phase, the cells are metabolically active and increase only in cell size. The population then enters the log phase, in which cell numbers increase in a logarithmic fashion. The log phase continues until nutrients are depleted or toxic products accumulate, at which time the cell growth rate slows, and some cells may begin to die. The log phase of bacterial growth is followed by the stationary phase, in which the size of a population of bacteria remains constant, even though some cells continue to divide and others begin to die. The stationary phase is followed by the death phase, in which the death of cells in the population exceeds the formation of new cells. The length of time before the onset of the death phase depends on the species and the medium.

If the population of a species is transferred to the more suitable environment, then it will show  protection against enemies. Populations are groups of individuals belonging to the same species that live in the same region at the same time. Population density is a measure of the number of organisms that make up a population in a defined area. In the suitable environment, the species of the population becomes more strong to fight with enemies and protect themselves.

In mutualism, each individual benefits from the activity of the other. In commensalism relationships, one organism benefits from the other without affecting other. Predation is a biological interaction where a predator (an organism that is hunting) feeds on its prey (the organism that is attacked). Symbiosis is a close ecological relationship between the individuals of two (or more) different species. The term symbiotic is used to define a relationship that is mutually beneficial to the involved parties. 

The favourable conditions available for the survival determines the distribution of species in a particular area. The word niche refers to a species' requirements for survival and reproduction. These requirements include both resources (like food) and proper habitat conditions. If two species lives in the same area then they would compete for the same resources. Therefore, species must at least have slightly different niches in order to coexist. Therefore, the correct answer is option D.