Ecology - the study of the interactions of organisms with each other and their environment is one of the most important areas of modern sciences. We are only now beginning to understand the various interactions of plants, animals, and all other living organisms upon one another. By understanding the interactions of living organisms in a specific ecosystem, we may be able to better understand how humans are changing the face of the world in which they live.
In each ecosystem there are specific groups of individuals, which are called a population. Several populations, which occur at one place, are called a community. An ecosystem is a particular place where a community exists and interacts with its physical surroundings as well as itself.
These interactions between the species of an ecosystem have been grouped into three main categories, mutualism, competition, and plant herbivore (plant pathogen) interactions.
Mutualism is an interaction where both species benefit, in many mutualisms neither organism can survive with out the other. These interactions occur readily in many different ecosystems, such as the interaction of the nitrogen fixing bacteria and the legumes, an integral part of the nitrogen cycle.
Another interaction is that of ants and the acacia tree, the bulls horn acacia is an excellent example of mutualism, by forming a mutual relationship with a specific species of ant the acacia is able to gain protection while the ants gain shelter and food. The bulls horn acacia tree has large thorns which are hollow, these thorns serve as a protective home for the ants, along with the shelter the acacia also has special nectarines and belatin bodies which provide the ants with nourishment. In return for protection and nourishment the ants protect the acacia from herbivores such as caterpillars and competition of other plants. This allows the acacia tree to grow rapidly in areas of fierce competition among plants, without the ants the acacia would die and with out the acacia the ants would die this interaction is an excellent example of a mutual interaction between plant and animal.
Competition is another interaction which frequently occurs in an ecosystem. Competition occurs when more than one species in an ecosystem is competing for the same resource, this may be light, nitrogen, or any other factor which regulates a plants growth. This competition often results in species specialization. For example competition for light in the forest often is a controlling factor in plant growth. To overcome this obstacle many plants have evolved specialized habitats such as rapid growth in open areas where tree fall has occurred or broad leaves to absorb light. By adapting to the conditions available an organism is able to survive and reproduce.
Plant herbivore interactions occur in all ecosystems and are of primary importance. These interactions have led the evolution and adaptation of many plant species, since herbivores and pathogens destroy a plants leaves and fruits, this limits a plants ability to reproduce. For this reason many plants have become adapted to defend themselves with a variety of defenses. Many plants use chemical compounds to protect themselves from attack these compounds range from being distasteful to an organism to being poisonous. And are known to be of utmost importance to a plants survival. In addition to interacting with herbivores plants and animals in an ecosystem interact with one another, these interactions cause succession or change over time. The plants and animals of the ecosystem are divided into several different trophic levels based on the nutritional demands of the organism.