Sample Assessments Ecclogy revised (Ccmpatibility Model Word Layout References M

Question

Sample Assessments Ecclogy revised (Ccmpatibility Model Word Layout References Mailings Review View Add-ins · , Emphasis Heading 1 INornal | Stiong Subtitle Tale Paragraplh Styles 35 30 26 20 15 10 250 kangaroo rats +plant productivity +150 100 60 1987 1988 1989 1990 1991 1992 1993 1994 1996 August Census Fig 2. Trends in kangaroo rat population and plant productivity in Califomia. (Source: http://esrp.csustanedu/publications/pubhmlphp?doc=smp&file;=chapterO2H00 html) 2A. Describe the most important pattem you see in Fig. 2. B. Explain this pattern, stating clearly which is the independent variable. C. Predict which will have a greater total biomass: kangaroo rats or grass. Explain your reasoning D. Predict which year had the highest rainfall Explain your reasoning

Explanation / Answer

2. A.

The most important pattern apparent from the fig. is that the kangaroo rat population is dependant on the plant productivity except for some exceptions. In other words, the plant productivity can, in turn, regulate the kangaroo rat population. The graph clearly shows that when the productivity increases the population also increases and vice versa. However, there are exceptions like the year 1991 and 1995 when the productivity is high but still, the population was low or the year 1987 when the population was high despite low productivity. These exceptions need to be examined further for more accurate analysis of what other environmental factors have influenced the population of the Kangaroo rats like the prey abundance, extreme event and so on.

B)

As stated earlier, population depend on productivity and not vice versa. Therefore, the productivity is the independent variable whereas the population is the dependent variable. Productivity is dependant on factors like the light, rainfall, temperature, nutrients etc., not population. However, the population of many herbivores like kangaroo rats is indeed dependant on the plant productivity. The pattern shows that the productivity regulates the kangaroo rat population.

C.

In trophic levels, grass come under the 'producers' whereas, the Kangaroo rats come under the 'herbivores'. As we know, the biomass goes on decreasing as we go up the trophic levels. Therefore, grass has almost 10 times the total biomass as that of the Kangaroo rat which eats it.

D.

The major factor that affects the plant productivity is the rainfall. Since other factors like Solar constant, temperature, nutrients etc tend to remain similar when taken as a yearly average, the impact of rainfall becomes the determinant of productivity in that year. As evident from the graph, the productivity was maximum in 1992 and then in 1996 therefore, these years experienced a maximum of rainfall.

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