Animals and Their Environment

To understanding individual animals, and in turn populations of animals, you must first understand the relationship they have with their environment.

Animal Habitats

The environment in which an animal lives is referred to as its habitat. A habitat includes both biotic (living) and abiotic (non-living) components of the animal's environment.

Abiotic components of an animal's environment include a huge range of characteristics, examples of which include:

• Temperature
• Humidity
• Oxygen
• Wind
• Soil composition
• Day length
• Elevation

Biotic components of an animal's environment include such things as:

• Plant matter
• Predators
• Parasites
• Competitors
• Individuals of the same species

Animals Get Energy From the Environment

Animals require energy to support the processes of life: movement, foraging, digestion, reproduction, growth, and work. Organisms can be categorized into one of the following groups:

• Autotroph—an organism that obtains energy from sunlight (in the case of green plants) or inorganic compounds (in the case of sulfur bacteria)
• Heterotroph—an organism that uses organic materials as a source of energy

Animals are heterotrophs, obtaining their energy from the ingestion of other organisms. When resources are scarce or environmental conditions limit the ability of animals to obtain food or go about their normal activities, animals' metabolic activity may decrease to conserve energy until better conditions prevail.

A component of an organism's environment, such as a nutrient, that is in short supply and therefore limits the organism's ability to reproduce in greater numbers is referred to as a limiting factor of the environment. 

The different types of metabolic dormancy or responses include:

• Torpor—a time of decreased metabolism and reduced body temperature in daily activity cycles
• Hibernation—a time of decreased metabolism and reduced body temperature that may last weeks or months
• Winter sleep—periods of inactivity during which body temperature does not fall substantially and from which animals can be awakened and become active quickly
• Aestivation—a period of inactivity in animals that must sustain extended periods of drying

Environmental characteristics (temperature, moisture, food availability, and so on) vary over time and location so animals have adapted to a certain range of values for each characteristic.

The range of an environmental characteristic to which an animal is adapted is called its tolerance range for that characteristic. Within an animal's tolerance range is an optimal range of values at which the animal is most successful.

Animals Become Acclimated to Survive

Sometimes, in response to a prolonged change in environmental characteristic, an animal's physiology adjusts to accommodate the change in its environment, and in doing so, its tolerance range shifts. This shift in tolerance range is called acclimation.

For example, sheep in cold, damp climates grow thicker winter coats. And, a study of lizards showed that those acclimated to warm weather could maintain a faster speed than lizards not acclimated to those conditions. Likewise, the digestive systems of white-tailed deer adjust to the available food supply in winter versus summer.