To survive, an organism needs a habitat that features somewhere to attract mates and find resources, has food, and protects it from the weather and extreme temperatures. The specifics of what an organism needs to survive varies between species, and many must adapt to environments to thrive.
Organisms survive by finding habitats that provide everything they require. This includes shelter, which protects organisms from weather extremes. For example, when temperatures become too cold, animals may need thermal shelter. Additionally, this environment protects them from predators, and gives them somewhere to mate and forage for food. When this food is not available, the organisms experience nutritional deficiencies. The availability of food resources in the area also affects prey availability. This means that if there is not enough food available, smaller members of the food chain are not accessible for larger members to eat.
As food, water and suitable habitats are not always available, organisms must compete with each other and adapt to their surroundings. Some factors, such as changes in temperature and the presence of competitors, force organisms to adapt to their environment, but if local changes are too erratic they may find adaptation becomes impossible. If resources in a local area are scarce and there are two species present, they may not be able to exist alongside one another.