Other Characteristics of Life
In the previous lesson, we looked at some of the properties of life such as order, sensitivity, reproduction, growth and development. In this lesson, we’ll continue from where we stopped and look at other characteristics of life.
Even the smallest organisms are complex and require multiple regulatory mechanisms to coordinate internal functions, respond to stimuli, and cope with environmental stresses. Two examples of internal functions regulated in an organism are nutrient transport and blood flow. Organs (groups of tissues working together) perform specific functions, such as carrying oxygen throughout the body, removing wastes, delivering nutrients to every cell, and cooling the body.
In order to function properly, cells need to have appropriate conditions such as proper temperature, pH, and appropriate concentration of diverse chemicals. These conditions may, however, change from one moment to the next. Organisms are able to maintain internal conditions within a narrow range almost constantly, despite environmental changes, through homeostasis (literally, “steady state”)—the ability of an organism to maintain constant internal conditions.
For example, an organism needs to regulate body temperature through a process known as thermoregulation. Organisms that live in cold climates, such as the polar bear (see image above), have body structures that help them withstand low temperatures and conserve body heat. Structures that aid in this type of insulation include fur, feathers, blubber, and fat. In hot climates, organisms have methods (such as perspiration in humans or panting in dogs) that help them to shed excess body heat.
All organisms use a source of energy for their metabolic activities. Some organisms capture energy from the sun and convert it into chemical energy in food. On the other hand, others use chemical energy in molecules they take in as food (see image above).
How do organisms respond to change?
Organisms use energy to grow, develop, respond to stimuli, and maintain homeostasis. Energy is the ability to cause change. In general, organisms get their energy from food.
Any behavior, structure, or internal process that allows an organism to make changes in response to environmental factors and live long enough to reproduce is called an adaptation. For example, the leaves of many desert plants as in the image above have a thick, waxy coating. This is an adaptation that helps these plants conserve water. Similarly, having large eyes is an adaptation that lets owls see well at night. The gradual change in a species over time due to adaptations is called evolution.