Ecology

Species interactions, natural selection, speciation, and evolution in action

What is ecology?

Ecology studies how living organisms interact with each other and with their environment, and how those interactions, repeated over many generations, shape the traits species carry today through the process of evolution.

Relationships between species

Species living in the same area interact with each other in several characteristic ways. In mutualism, both species benefit — like bees pollinating flowers while collecting nectar for food. In parasitism, one species benefits at the other's expense, without necessarily killing it outright. In commensalism, one species benefits while the other is essentially unaffected. Recognizing these relationship types helps explain why particular species are so often found living closely together.

Natural selection: how species change over time

Natural selection is the well-established process by which individuals with traits better suited to their environment tend to survive and reproduce more successfully, passing those traits on more often to the next generation. Over many generations, this can gradually shift a population's characteristics, a process called evolution. This mechanism, first clearly described by Charles Darwin and Alfred Russel Wallace in 1858, has since been confirmed directly and repeatedly through both fossil evidence and, as covered in the advanced article, direct observation of evolution happening in real time.

Adaptation

An adaptation is a trait that has been shaped by natural selection because it improves an organism's ability to survive and reproduce in its particular environment — a polar bear's thick fur, a cactus's water-storing tissue, and a bird's wing shape suited to its particular flying style are all examples of adaptations to specific environmental demands.

Why ecology matters

Ecology explains the diversity of life on Earth and how species come to be so well suited to their particular environments, and it provides essential tools for conservation, managing agricultural pests and diseases, and understanding how species (including disease-causing organisms) respond and adapt to changing conditions.