The model simulates the life cycle of daphnia. Female daphnia carry a brood of babies under their carapace. The circles on the daphnia's back are the babies. After 2 days the female molts and the babies are released or born. These babies spend 7 to 9 days growing as juveniles.
After about 8 days the juveniles mature into females. As females, every two days they molt and release babies.
After about 30 days the female dies. If the female is stressed by pollution or cold weather she doesn't live as long.
In the summer the females reproduce asexually. They produce almost all females. In the fall or when they are stressed some males are produced. The males mate with the females to produce eggs. The eggs have a hard shell that allows them to wait for years if necessary. When conditions are right the eggs hatch and the process starts again.
Since a few males are produced the model needs to also simulate their lives.
The model simulates the effect of two kinds of medicine on daphnia, clofibric acid and fluoxetine. These medicines are found in dilute quantities in lakes and rivers. They affect the quantity and ratio of the births. The medicines also affect the death rate of the adults.
The model allows you to do 4 experiments.
You can observe the reproduction of daphnia with:
Ask your teacher if you will be working with the STELLA model or the Excel spreadsheet.
