Relationship between organisms and their environment
Ecology is the science of relationships between organisms and their environment. Organisms (biotic factors) are influenced by their environment, such as temperature, soil conditions, food plants, competitors, or predators.
On the other hand, organisms have an effect on their environment by out competing other species or killing their prey, and also by influencing their abiotic environment. Organisms are an integral part of carbon and nutrient cycles of the ecosystems. The composition of the atmosphere and large parts of the lithosphere (rigid outermost shell of a rocky planet) are products of life on earth.
Understanding ecological relationships is essential in today's society. Climate change, contaminated soils, loss of bio-diversity, alien species, and animal–spread diseases such as West–Nile virus are examples of current issues the understanding of which requires knowledge of the underlying ecological processes.