### Step 3: Construct Growth Curve; Fit with Model

Plot your data on a graph and think about how the zebra mussel population has changed over time in Round Lake. Follow the instructions below.

#### 1. Lable Axes

Scientific graphs depict the relationship between an **independent variable** (the one controlled by the experimenter) and a **dependent variable** (the one measured by the experimenter).

Use the dropdowns to select the proper variables, their scales and their units for the graph, then **click “Submit”**.

##### Your Data: Zebra Mussels in Round Lake (ZM/m^{2})

Year | Site 1 | Site 2 | Site 3 |
---|---|---|---|

1 | 0 | 0 | 1 |

2 | 9 | 8 | 3 |

3 | 183 | 126 | 90 |

4 | 3,380 | 2,765 | 1,869 |

5 | 68,274 | 58,329 | 34,524 |

### Step 3: Construct Growth Curve; Fit with Model

#### 2. Plot the Data

Plot your data for each year, then draw a line through the data points.

##### Your Data: Zebra Mussels in Round Lake (ZM/m^{2})

Year | Site 1 | Site 2 | Site 3 |
---|---|---|---|

1 | 0 | 0 | 1 |

2 | 9 | 8 | 3 |

3 | 183 | 126 | 90 |

4 | 3,380 | 2,765 | 1,869 |

5 | 68,274 | 58,329 | 34,524 |

### Step 3: Construct Growth Curve; Fit with Model

#### 3. Fit your Data to Appropriate Model: Expert’s Predictions

Complete the following statement using the radio buttons.

The number of individuals added each new year...

Population density of zebra mussels (Number of zebra mussels per metre square) at the three sampling sites over time for the first five years of sampling at Round Lake, Ontario, Canada.

“No. You chose an answer that I predicted in my model: A small, constant number of new individuals each year. However, your data show a steep increase in population size. It looks like they were much more successful at reproducing at low population density than I thought.” **Please try again.**

“No. You chose an answer that resembles my model. Both my model and your data show that growth was proportional to the number of zebra mussels already present. However, I also predicted growth would level off by 5 years, but the population is still increasing! I guess the resources in Round Lake are not as limited as I thought.” **Please try again.**

“Yes! Your data are just as my model predicted! The number of individuals added each year was proportional to number already present, so that as N got bigger, growth became explosive. Also, my assumption about growth being unlimited by resources at Round Lake was correct too. You can see that nothing is stopping the zebra mussels yet!”** Click “Next” to continue.**

### Step 3: Construct Growth Curve; Fit with Model

#### 4. Fit your Data to Appropriate Model: Equations

Population growth models, as you know, are also expressed in equations.

Which equation matches the model you chose?

Which equation matches the model you chose?

Population density of zebra mussels (Number of zebra mussels per metre square) at the three sampling sites over time for the first five years of sampling at Round Lake, Ontario, Canada.

“No. This equation doesn’t describe your data. This is an equation for a straight line similar to my prediction in my model in which a constant number of individuals is added each year.”** Please try again**

“No. This equation doesn’t describe your data. This is an equation for a logistic curve similar to my model in which the number of individuals added each year is eventually limited by external factors.”** Please try again.**

“Yes! This equation describes your data! This is an equation for exponential growth similar to my model in which the number of individuals added each year is not limited.”** Click “Next” to continue.**