Defined as the relationship between organisms and their environment. Resources: consumed by organisms, making them less available for others: food, water, mates. Conditions influence organism but not consumed: temperature, day length, acidity. Organisms can compete for resources but not conditions. Conditions can impact resources by making them tough or unavailable to organism: freezing temp h2o into ice. Hazards: factors that only affect organism negatively: bad weather conditions, substances. Darwin natural sel theory distribution of organisms. Organisms interact with their environment many ways. Extracting resources from the habitat, while they protecting themselves from predators. Organism-organism interaction allows from recognizing friend to foe; potential mates. Main purpose: pass on genes and reproduce. Habitat: a physical location in time and space, can be large or small, but it is more then that it consists of other organisms; ecosystem: biotic community and its abiotic environment. Car and body coexist: ecosystem has both bio and abio features that work togeather.