Professor D. Anderson
Jerry “Sean” Hughes
Some studies and experiments have shown that population growth can be followed with the flour beetle (Tribolium confusum). Studying these beetles for over a month in varying habitats showed there was a dramatic increase in the populations with larger quantities of food, and a much slower growth rate with more space and the space amount of food. The experiment that I conducted provides a direct correlation between the roles of space and food in a controlled study of these differing populations.
Thomas Malthus, in the year 1798, found that varying populations of both plants and animals are geometrically progressive. Populations increase exponentially, while food supplies increase at approximately the same rate. Because of the progression, any animal or plant could spread over most livable places; however, populations of species remain at a constant level because of death and therefore do not grow indefinitely. Also, there is something in place that restricts population growth (Malthus 1798). To test Malthus’s statement the Tribolium confusum, or confused flour beetle can be used for certain hypothesis and predictions that test limiting factors, such as food and space. The Tribolium confusum are functional specimens for a study of these limiting factors because of the growth rate. The growth period of these particular beetles are relatively fast. After approximately 5-12 days of fertilization, the egg hatches into larvae. The larvae last 22-100 days and the pupae last around 8 days (Brereton 1962). These beetles are easy to examine, because they can thrive off of flour with very little moisture, and vermiculite can be used to create space. The life span of the Tribolium confusum tends to last around 200 days; our experiment takes place within that time limit. Hypothesis:
Hypothesis 1: The amount of food is a limiting resource for the population of the Tribolium confusum. Hypothesis 2: The amount of space is a limiting resource for the population of the Tribolium confusum. Predictions:
Prediction 1: I predicted that the more food that Tribolium confusum had the more the population will grow. Prediction 2: I predicted that the more space Tribolium confusum had the more the population would grow. Methods and Materials:
To test whether food or space are limiting factors on population growth, our lab group created different artificial habitats for Tribolium Confusum thrive. For the experiment 6 different treatments where created. In this experiment we used 6 different half pint, large opening mason jars. All of these jars were the same size, and contained different amounts of food (corn flour) and livable space (vermiculite + flour). A measurable amount of corn flour and/or vermiculite were added to each jar. Jar A received 5g of corn flour. Jar B received 45g of corn flour. Jar C received 5g of corn flour and mixed with vermiculite to the volume of 25g. Jar D received 5 grams of corn flour with vermiculite to the volume of 45g. Jar E received 5 grams of corn flour with vermiculite to the volume of 65g. Jar F received 25 grams of corn flour with vermiculite to the volume of 45g. Table 1: Amount of Corn flour and Vermiculite added to the 6 different jars. Jar
| Amount of Flour
| Fill Volume 25g
| Fill Volume 45g
| Fill Volume 65g
| Fill Volume 45g
After the flour and vermiculite were added to the jars, 10 adult Tribolium confusum were counted out and placed in each jar. A paper towel was placed over the mouth of each jar, a mesh layer, and a ring to secure the jars. They were then labeled with the above information, each coinciding with the amounts in the jar, labeled with the group name and then placed in an environment conducive for accurate results. After the given time limit, the jars were reopened...
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Pearl, Raymond. 1925. Biology of Population Growth. NY: Knopf. 260 pp.
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