An environmental stimulus refers to any external factor in the environment that can evoke a response from an organism or a system. These stimuli can be physical, chemical, or biological and are crucial for survival, growth, and behavior.
For instance, in the case of animals, environmental stimuli can include changes in temperature, light, sound, or the presence of other animals. A classic example is how a bird may respond to the sight of a predator by seeking shelter or flying away. In plants, environmental stimuli could involve light (phototropism), where plants grow towards light sources to maximize photosynthesis.
The ability to respond to environmental stimuli is essential for adaptation and can influence various aspects of life, such as migration patterns in animals or flowering in plants. Understanding how organisms react to their environments can provide insights into ecological balance and the effects of changes within ecosystems.