Competition

INTRODUCTION:

Competition occurs between any organisms living in a mutual habitat. Whether it is for food, water, shelter, or a mate, competition can be harmful or helpful to each organism. There are two basic types of competition; intraspecific and interspecific. These terms refer to competition within a specific species and the competition between different species, respectively. In this lab, we conducted 3 basic experiments. Our goal was to observe the effects of the competition in each instance.The first one was to observe the intraspecific competition between the wheat plant species, the second was for the intraspecific competition between the mustard plant species. The third was the interspecific competition of the wheat and mustard species together. The latter experiment's data was divided into two sub groups of high density and low density, for purposes of graphing Dewitt diagrams. Dewitt diagrams are a way of expressing % yield and total productivity data so it can be evaluated and compared effectively.

It has been noted that intraspecific competitions tend to be more intense than interspecific ones (Ciara, 1993). This is because members of the same species need the same types and amounts of nutrients. When these similar species are in the same habitat with fixed resources, then they consequently have to "fight " for their needs. This is was basis for our hypothesis. We hypopthesized that the species that were involved with the interspecific competitions would have greater production (by ave. weight of grams) than their counterparts involved in the intraspecific competitions. Furthermore, we hypothesized that as the density of the intraspecific and interspecific competition species increased, then the production of the plants (by ave, weight in grams) would go down.

MATERIALS AND METHODS:

Six weeks previous to the conductance of this lab, Biology 108 section,planted wheat and mustard plants according to table#1 on page 3 of the Principles of Biology 108 Lab Manual . This table depicts all of the total pots and number and type of seeds planted in the pots. It accounts for the experiments of the intraspecific competition and interspecific competition. Replicates of each pot were planted to add precision and more acceptable statistics. Therefore, there were 40 pots, that is, 20 treatments conducted twice(Ciara, 1993).

Each Biology 108 section planted these pots and the data from every section was to be combined for an overall data sheet. Our group in section 6 had the role of planting 5 of the experimental pots with the assigned number of wheat seeds or mustard seeds or both. We filled each 4" pot with artificial soil mix and packet it down below the rim, and then placed the required number of seeds onto the surface and sprinkled a little more soil on top. We were ordered by the TAs to plant a few extra seeds into each pot, depending on the original number of seeds originally assigned to each pot. This was meant to account for the statistical expected non-germination of some of the seeds. In a week or two following the initial planting, the extra plants were weeded out, so that each pot contained the originally assigned number of plants.

The pots were then placed in the University greenhouse and watered routinely , and given supplemental light (Ciara, 1993). Six weeks later the data was collected.

There were several calculations included in the expression of the data, primarily the interspecific data and the Dewitt diagrams. The Dewitt diagrams were graphs that enabled comparison of; the percent yield of the mustard ( mustard ave. pot weight in mixture / mustard ave, pot weight when alone x 100) and percent yield of wheat ( wheat ave. pot weight in mixture / wheat ave, pot weight when alone x 100). The Dewitt diagrams also enabled us to graph the Total Pot Productivity, which is the percent yield of mustard added to the percent yield of wheat, all on the same graph. The data for the Dewitt diagrams were divided into 2 groups, that of high density and low density relating to the number of plants in a pot.

RESULTS:

INTERSPECIFIC DATA

The interspecific data is displayed on figures #1 and #2, the Dewitt Diagrams. The low density data is on figure #1 and it shows the percent yield of the mustard plant treatments in relation to the treatments of 0, 2, 4, 6 and 8 number of mustard plants compared to the percent yield of the wheat plant treatments with the same number of plants per treatment, respectively.

Also shown ( by the dotted line) is the optimum percent yield of each species had there been no interaction or competition between species. In comparison

to the optimum percent yield, the species in this low density competition, the graph shows us that the mustard exhibited a slightly higher percent yield than the wheat, as it had more plotted points above its optimum percent yield.

Another set of data that it recorded on this graph is Total Pot Productivity. This curve showed that the biomass of both species was slightly higher than the optimum of 100%.

In figure #2, the high density Dewitt Diagrams, the percent yield of the mustard plant treatments in relation to the treatments of 0, 8, 16, 24 and 32 number of mustard plants compared to the percent yield of the wheat plant treatments with the same number of plants per treatment, respectively. Again, as in the low density results, the mustard had a higher percent yield. There was one extravagently high percent yield for the mustard at the 24 mustard / 8 wheat plant treatment. There was also a higher percent yield at the same treatment for the wheat.

INTRASPECIFIC DATA

In figure #3 (Density Data) there is a visualization of the data collected for the intraspecific experiments. This graph shows the average plant weight compared to the number of plants in its respective pot. There is a line graphed for the wheat plants and one for the mustard plants. We see that, overall, the average plant weight of each species decreases as the density of the plants in each pot increases.

Figure #4 displays the comparison between the average weights per treatment of the mustard plants in intraspecific competition and interspecific competition. It also compares the weights per treatment of the wheat plants in intraspecific competition and interspecific competition. In the interspecific competition, the number of plants ( of the particular species being documented) does have an additional number of the other species in its pot which is indicated in the figure. Both the mustard and the wheat