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Lab 4
POPULATION GROWTH byDrs. Michael T. Dixon and Edith C. Marsh |
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Exercise 1
We will start lab by calculating population growth by hand (or calculator) over ten generations and then graphing the growth.
In this exercise we will explore rates of population growth using several models. In science a model is not just a six-inch wooden sailing ship in a bottle or a plastic ’55 Chevy held together by glue. A model is a description, often mathematical, of how two or more things relate to each other. For example, the simplest biological model I can think of is "your age plus one" which predicts how old you will be next year. Weather is forecasted using models that include air currents, land temperatures, ocean temperatures, geography, relative humidity, reflectance, and many other factors. My simple age model is extremely accurate, weather models are somewhat less accurate!
The Bacterial Model
In bacteria, a given individual divides every 20 minutes (under optimum conditions) to give two new individuals. The original cell becomes two new cells - no more, no less - and the original cell no longer exists. We will modify the starting number of cells and the death rate to see how they effect population growth.
The Perennial Plant Model
Most organisms do not disappear when they reproduce but instead continue to live and reproduce again in the future. It is possible for parents and their offspring to both be alive and reproducing. Imagine a majestic oak tree, several hundred years old that has been producing acorns for hundreds of years surrounded by younger oaks, its offspring, that also reproduce each year. Having parents and offspring reproducing together in future generations changes population growth curves.
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