How do unicellular organisms exhibit the characteristics of life?

Unicellular organisms exhibit the characteristics of life through growth, reproduction, metabolism, response to stimuli, and evolution.

Unicellular organisms, despite their simplicity, are capable of performing all the necessary functions that define life. They grow by increasing their cell size or cell number. This is achieved through the process of cell division, where the organism duplicates its genetic material and divides into two. This process also allows for reproduction, another key characteristic of life. Unicellular organisms reproduce asexually, meaning they produce offspring that are genetically identical to the parent organism.

Metabolism is another crucial characteristic of life that unicellular organisms exhibit. They take in nutrients from their environment, which they use to produce energy through a series of chemical reactions. This energy is then used for growth, reproduction, and other essential functions. Unicellular organisms also produce waste products as a result of these metabolic processes, which they excrete into their environment.

Unicellular organisms also respond to stimuli in their environment. This can include changes in temperature, light, or the presence of certain chemicals. They can move towards or away from these stimuli, a behaviour known as taxis. For example, many unicellular organisms move towards light (positive phototaxis) or away from harmful substances (negative chemotaxis).

Finally, unicellular organisms are capable of evolution. Over time, changes in their genetic material can lead to new traits that may be beneficial for survival. If these traits are passed on to future generations, they can become more common in the population, leading to evolution. This process of natural selection is a fundamental characteristic of life and is exhibited by all living organisms, including those that are unicellular.