Protect From Animals
Animals–organisms that range from microscopic to larger than a bus–embody a wide variety of harms to living systems, including other animals. They threaten through predation, herbivory, defense, and parasitism, and they compete for resources such as water, nutrients, and space. Any given living organism commonly faces threats from a variety of animals, requiring strategies that effectively defend from each. Trout and other bony fish, for example, escape predators by having scales made of very thin, flake-like pieces of bone covered with slippery mucus. They also have behavioral strategies such as camouflage, fast swimming, and twisting and turning to achieve release from a predator’s grip.
Sense Sound and Other Vibrations From the Environment
For living systems, sensing sound and other vibrations is important for communicating and detecting conditions within their environment. Living systems must locate a signal’s source so that they can move toward it (such as when it is food or a potential mate) or away from it (such as when it is a predator). To prompt an appropriate response, living systems must sense these signals, recognize their amplitude or volume (which is sometimes very low), and determine their direction. Living systems must be attuned to signals relevant to them and able to distinguish these from irrelevant sounds to avoid expending unnecessary energy. For example, owls’ ears are asymmetrically placed. This enables them to detect sounds more accurately, which helps them locate small prey at night and avoid wasting energy chasing down irrelevant sounds.
Sense Motion
Perceiving motion is important for a living system to sense where it is in relation to a moving environment, which is critical in locating resources or wayfinding. This applies whether the environment itself is in motion (such as water movement coming from a nearby fish) or the living system is moving within a stationary environment (such as a bird flying through the air). Because motion dampens over distance and the cost of missing those motion signals is high, living systems must be quite sensitive to these signals. For example, fast-flying big brown bats have microscopic, stiff, domed hairs on their wing membranes that act as a sensor array to monitor flight speed and airflow conditions.
