Interactions between Predators and Prey - Lab Report Example

Interactions between Predators and Prey Introduction The dynamics of a population are highly influenced by abioticand biotic factors within the ecosystem. Sunlight, soil, climate, air and water are the abiotic factors while birth rate, predation, mortality and diseases form the biotic factors. Predation is a process through which members of a species feed directly on the other species. In this respect, the prey is often harmed at the benefit of the predator. However, at the population level, the prey can benefit as a result of reduction of competition for food within the prey species as well as removal of aged and sick animals. As stated by Billick & Price (2011), this kind of interaction results into some species going through cyclic changes in their numbers thus sharp increases and periodic crushes can be observed. The process of natural selection outlines the way organisms survive within an ecosystem. This is because certain species are likely to reproduce many individual offspring beyond which the habitat in which they live can support. In this regard, species must have certain adaptations in order to gain advantage for their own survival including ability to run fast, adaptations, mimicry, moments of truth defenses as well as camouflage. These abilities are then passed through to the offspring by the parents who survive. This study examined the effect of growth on the population of mice when there are no predators and in the environment where there are predators. Mice in Habitat with no Predator The field that had been used for agriculture was left to recover for five years for grass to start growing before ten field mice moved in. since there was plenty of food the mice grew and start to reproduce. We assumed that a pair of mice produced three offspring in a generation and their parents do not die. To get the number of mice in a generation, the number of mice that initially moved to the agricultural firm were divided by two then multiplied by three. This was done for thirty generations assuming that there is plenty of food, water & no predators and results presented in the table and graph. Table 1: Growth in Mice in Habitat with no Predator 1 2 3 4 5 6 7 8 9 10 10 25 61 151 376 940 116 290 725 36 11 12 13 14 15 16 17 18 19 20 90 225 561 28 70 175 436 1090 54 135 336 21 22 23 24 25 26 27 28 29 30 336 840 42 105 261 651 32 80 200 500 Figure 1: Growth of mice in habitat without predators Lag phase This is the initial phase when the population adapts to the new environment hence shows very small increase. Even though there is positive growth in the overall population, many mice are new thus trying to adapt to climate, water, food and other abiotic factors. Exponential Phase This is the period of rapid growth and is characterized by highly adaptable mice and the availability of abundant food, water and favorable climate. Exponential phase, often referred to as logarithmic phase is also characterized by low competition for food, water, space and the other nutrients. Stationary Phase/ Carrying Capacity During this phase, growth rate of the population becomes stable since the rate of natality and mortality remains the same. This is mainly attributed to environmental resistance thus the population growth rate has to slow down till it reaches equilibrium. Natural Selection Plants are the primary producers of energy and organic nutrients through the process of photosynthesis. Primary consumers feed on the plants while secondary consumers feed on primary consumers in the food web. Predators get their energy through feeding on the prey hence they have direct effect on the number of breeding prey and the population in general. In this regard, we hold the hypothesis that in the presence of predators, the number of mice in the population will reduce in the presence of predators. The following observation was made in the growth rate of mice in the presence of predators. Table 2: Population of Mice In the Presence of Predators Mice Surviving 20 15 28 30 16 6 - 1 0 10 Mice after reproduction - 35 70 75 20 15 10 1 10 25 Predators surviving 2 2 4 7 12 9 5 3 - - Predators after reproduction - 4 8 13 24 17 9 5 - - Mice Surviving 25 61 151 47 116 290 36 90 225 28 Mice after reproduction 61 151 376 940 290 725 90 225 561 70 Predators surviving - - - - - - - - - - Predators after reproduction - - - - - - - - -- - - Natural selection – coloration Due to the fact that the presence of predators directly reduces the number of breeding and the overall population of the prey, the prey do not only adapt to the environment in terms of ability to run but also on the ability to camouflage. Color is very important characteristic feature that determines the ability of mice to hide and avoid being eaten by the predators thus reducing the population of that species. This concept was demonstrated by using mice with different colors red, Green, Blue, White and black and the results recorded in the table 3 below for each colored mice. Table 3: Natural Selection - Coloration Red Green Blue White Black 1 1 1 0 1 1 2 0 1 1 2 2 3 1 2 1 1 0 4 2 1 2 1 1 5 1 0 1 2 2 Average 1 1 1.2 1.5 1.2 My hypothesis was not correct because there are no significant variations within mice with different colors. Figure 2: Natural selection colored Discussion In this study, we had hypothesized that the presence of predators is likely to affect the breeding mice population thus affect the overall population of mice in general. With respect to the results of this study, my hypothesis was correct. This is because the presence of predators results into the reduction of mice directly and indirectly. Predators affect mice communities by inducing mortalities and feeding on the mice. The indirect ways is through predator-induced changes in the mice behavior thus resulting into dare consequences in population growth. For instance, predator avoidance behavior is harmful to the prey since it is costly in terms of losing feeding time, mating time and shifting to less favorable food and environment for safety. According to Billick & Price (2011), the nature of the interaction between the prey and their predators are important primarily because of two reasons: determining and maintaining a community structure and determining prey and predators’ populations. This is the reason why the population crushes changed in the presence of predator as shown in table 2. The change in frequency of population crush is mainly attributed to mice’s anti-predatory behavior as well as the increase in predators. The frequency was reduced also since the mice’s offspring are more susceptible than the adults coupled with increasing predators, many young ones are not able to grow to maturity and reproduce. The carrying capacity refers to the number of individuals that can be sustained indefinitely within a given habitat. The carrying capacity of mice in this experiment is determined by the number of mouse that can be sustained indefinitely within this ecosystem. From the table 1 and figure 1 of this report, we can see that the 18th generation had the highest number of mouse in it and out of the 30 generations, the population crushed six times. The carrying capacity of the prey is dictated by the limiting factors such as water, food, nutrients, oxygen, sunlight and vitamin. The pre population had a lot of influence on the predator’s population. As recorded in table 2, the higher the number of mice population, the higher the number of predators. This is so because the predators have readily available food and thus there is reduced competition for food. This is shown in table 2 of this study, moreover, when the population crushes, all the predators dies and when new mice is brought into the habitat without predators, there is higher number of preys survival. Reduced competition for preys, oxygen, water and other resources leads to increase in the population of predators. However, if more predators are added into the habitat, there would be increased population crushing frequency as well as survival of both predators and prey. Natural selection – Coloration The results of this study as recorded in table 3 and figure 2 shows that my hypothesis was not correct. This is because there no significant differences in the number of preys/mice counted for different colors. This shows that mice cannot effectively camouflage on the basis of color. However, it is important to note that they would probably adopt different survival traits to enable them live within the habitat. References Billick, I. & Price, M.V. (2011). The Ecology of Place: Contributions of Place-Based Research to Ecological Understanding. Chicago: University of Chicago Press. Read More