Animal Behavior

Have you ever left a fruit bowl out for a while and return to discover a fruit fly settlement? But why is the fruit fly attracted to ripe fruit in the first place? In other words, what is the stimulus that tells them where to go? This analysis is part of a wider field called ethology, which is the study of animal behavior.

A stimulus may cause two types of animal movement. Kinesis, which is non-directional or random, or taxis, which is directional. An example of kinesis would be the movement of the flies in random directions when chased away. Conversely, an example of taxis would be the directed movement of the flies back towards the ripe fruit. This specific type of taxis is referred to as chemotaxis and since it is towards the stimulant, food, it is further defined as positive chemotaxis. An example of negative chemotaxis would be the fly moving away from an insect repellent. Another common type of taxis is phototaxis, which is movement is response to a light stimulus. Moths are showing positive phototaxis when they move towards a light source. On the contrary, cockroaches that scuttle away when the light is turned on are being negatively phototactic. Geotaxis, also known as gravitaxis, is movement in response to gravity. Moving in the direction of gravity is positive geotaxis, while movement in the opposite direction is negative geotaxis. There are many other types of taxis, including aerotaxis, barotaxis, hydrotaxis, and magnetotaxis - which are movement in response to oxygen, pressure, water and magnetic fields respectively.

So why do scientists study animal behaviors like these? One of the goals may be to find the genetic basis for the behaviors exhibited by individuals or groups within a species. Sometimes, a behavior can even be traced to a specific mutation in a single gene. On a broader scale, understanding how genetics and behavioral traits are linked can also help us to gain a better understanding of behaviors across the animal kingdom, including our own.

In this lab, you will assess the geotactic, phototactic and chemotactic responses of the fruit fly Drosophila melanogaster, using choice chambers.