Positive feedback occurs when a change in the state of a system leads to additional and increased change. Thus, an increase in the size of one or more of the system’s outputs feeds back into the system and results in self-sustained change that alters the state of a system away from its original equilibrium towards instability Draw and example of a positive feedback loop into the space below: Predator-prey interactions and negative feedback The Hudson Bay Trading Company in Northern Canada kept very careful records of pelts (skins) brought in and sold by hunters over almost a century. This is a classic set of data and shows this relationship because the hare is the only prey of the lynx and the lynx its only predator. Usually things are more complicated. We have to assume that the numbers of animals trapped were small compared to the total populations and that the numbers trapped were roughly proportional to total population numbers. Also assumed is the prey always has enough food so it does not starve. Given that, the cycles are remarkably constant with the lynx populations always smaller than and lagging behind the hare ones. On average, what was the cycle length of the lynx population? On average, what was the cycle length of the hare population? Why do lynx numbers lag behind hare numbers?
Positive feedback occurs when a change in the state of a system leads to additional and increased change. Thus, an increase in the size of one or more of the system’s outputs feeds back into the system and results in self-sustained change that alters the state of a system away from its original equilibrium towards instability Draw and example of a positive feedback loop into the space below: Predator-prey interactions and negative feedback The Hudson Bay Trading Company in Northern Canada kept very careful records of pelts (skins) brought in and sold by hunters over almost a century. This is a classic set of data and shows this relationship because the hare is the only prey of the lynx and the lynx its only predator. Usually things are more complicated. We have to assume that the numbers of animals trapped were small compared to the total populations and that the numbers trapped were roughly proportional to total population numbers. Also assumed is the prey always has enough food so it does not starve. Given that, the cycles are remarkably constant with the lynx populations always smaller than and lagging behind the hare ones. On average, what was the cycle length of the lynx population? On average, what was the cycle length of the hare population? Why do lynx numbers lag behind hare numbers?