Essay On Krebs Ecology

Introduction According to Charles J. Krebs ecology is the “scientific study of the interaction between organisms and their environment that determine their distribution and abundance” (Krebs 1978). The environment is made up of different components that are classified as abiotic and biotic. Abiotic deals with nonliving and physical elements like rain, wind, soil or pollutions. Biotic are living components that include predation, parasites, and competition. Competition is an interaction between organisms that compete for resources and it can lower the population of one organism because the other one is better fit for the environment. Furthermore, the purpose of this laboratory exercise is to conduct an experiment as to why the two species of Paramecium Aurelia(Pa) and Paramecium Caudatum(Pc) would not habitually coexist in an environment. The observation was that the two species flourish when they were grown separately and in the mixed beaker, Pa thrived while Pc lessened. The population dynamics or changes in the size of population over time, included carrying capacity and important graph shaped curves. Carrying capacity (K) is the maximum of how big a population can grow, following stagnation and finally decreasing. The data presented is by sigmoid or S-shaped curve also known as logistic growth. Knowing about population dynamic is important because it sets the stage for prediction of carrying capacity. Moreover, competition was chosen from the abiotic and biotic elements because we wanted to verify if it was the competition of food that did not allowed the two species of ciliates to coexist in the same niche. The hypothesis was if the Pa and Pc were isolated, they would grow at an average rate because of the lack of competition for food, while the mixed solution would cause one to diminish its population in size. Procedure Procedures are as states in the Laboratory Manual for Biology 182 on pages 120-121 of exercise 9. (Bowker, 2015). Results Figure 1 Figure 1: Paramecium Aurelia (Pa) and Paramecium Caudatum (Pc) were used as the controlled group and PaMix and PcMix as the coexistence environment. The following was recorded over five weeks to measure competition. Conclusions In the Pa control (Figure 1), Pa grew logistically, but without evidence of a lag phase. From days 0 to 7, Pa was in the exponential phase increasing from a density of 10 cells/ml to 511 cells/ml. From days 17 to 35 Pa was in the stationary phase. Within the stationary phase, Pa continually increased from days 7 to 35 from 511 to 1505 cells/ml until the experiment was terminated on day 35. The estimated K for Pa in the control was 803_ cells/ml. The Pc control (Figure 1), Pc grew logistically, but without indication of a lag phase. From days 0 to 7, Pa was in the exponential phase with the density being 10 cells/ml to 150 cells/ml. From days 7 to 35 Pc continue to increase from 150 cells/ml to 459 cells/ml. The estimated K for Pc in the control was 266 cells/ml The PaMix (Figure 1), PaMix grew logistically, without a lag phase. Days 0 to 7 there was an exponential phase from a density of 5 cells/ml to 574 cells/ml. Then it …show more content…
The evidence that corroborates competition is that the percentages were 57% and 58% which dictates that competition can explain cohabitation. Furthermore the competitive exclusion hypothesis states that no two species can occupy the same niche and coexist. In figure one, we can see that PcMix was starting to diminish because it cannot inhabit the same niche and would have continued to decrease until extinction. The niche structured is made up of resource continuum which leads to resource partitioning. Resource continuum is when the Pa and Pc utilized the same food source leading to resource partitioning. To avoid competing, the Pa and Pc portioned the resources as to avoid extinction. Moreover, one similar experiment done was by Gause which derived the competitive exclusion hypothesis. The main differences between our experiment and his are we did not have a lag phase because we did not sample every day, instead we started in exponential. He managed to get similar numbers when beginning the experiment and we started with a random number. In conclusion, in his results, Pc became extinct which we only had decreasing