Organisms and Populations — BIOLOGY STD 12 Science — Question

In nature, living organisms such as animals, plants and microbes, cannot live in isolation and therefore, interact in various ways to form a biological community.
The interactions between populations of species in a community are broadly divided into two categories:
Positive Interactions:
Symbiosis or Mutualism: When two species live together in a close association that is helpful to both species, the relationship is known as symbiosis. The oxpecker bird and the rhinoceros exhibit this relationship. The oxpecker receives protection and obtains food from the ticks and other pests infesting the rhino’s skin.

Commensalism: Some organisms live together so that one organism benefits by the relationship while the other organism is neither helped nor harmed. This type of relationship is known as commensalism. An example of this association is the relationship between the shark and the small remora fish.

Negative Interactions: Certain interactions between different species give rise to negative effect on either or both species. Parasitism and predation are interaction where one species gains and the other suffers. While in the interaction called competition both species are harmed.
Parasitism: This is a relationship in which one organism, the parasite spends much or all of its life living in or another organism, the host. The parasite is dependent upon the host for food. The parasite benefits from the relationship and the host is always harmed. Parasites may bring about the death of their host, but most often only weaken their host. Human parasites may be external (ectoparasites) such as body lice, ticks, mites and leeches, or internal (endoparasites) such as tapeworms, some types of roundworms, malarial parasite, microfilaria and guineaworm.
Predation: This is commonly associated with the idea of strong attacking the weak such as the tiger pouncing upon the deer, the hawk upon the sparrow, and the frog upon the insects and so on. A species such as the frog may be both a prey and a predator. The relationship between a snake and a rat is more than that between a prey and a predator as the snake also seeks shelter in the rat holes.
Competition: The amount of food, light, space, minerals and water that are available in a particular habitat is limited. As a result, organisms are in competition with one another for one or more of these factors. Competition occurs not only among individuals of a given species but also between members of two or more species.
For instance, carnivorous animals such as tigers and leopards, compete for the prey. The members of kingdom Plantae, such as trees, shrubs and herbs in a forest are to compete for sunlight, nutrients and water and biological agents for pollination and dispersal.