Exam 1: The Web of Life

Suppose you were examining whether a synthetic chemical reduced the growth rate of mice. Which action would you take to ensure a controlled experiment?

Refer to the figures. The figures are based on studies of the effects of pesticides on the tadpole immune system. In a laboratory experiment, wood frog (Rana sylvatica) tadpoles were exposed to low or high concentrations of a pesticide, and then to Ribeiroia parasites. The tadpoles were then examined for (A) numbers of eosinophils and (B) numbers of Ribeiroia cysts. Error bars show one SD of the mean. Compared with the control group, the frogs exposed to low concentrations of pesticides had about how many times as many parasite cysts?

Refer to the table. The table represents the result of a survey of 39 lakes, some with and some without introduced rainbow or brook trout. The values are averages of the number of frogs present along a 10-meter piece of shoreline in lakes with and without trout. Given these results, one can conclude that

In a grassland ecosystem, plants capture 180 units per day of solar energy, and use 70 units per day in respiration. Animals consume about 20 units per day of the plants. The NPP of this system, in units per day, is

Which statement is not likely to be true within an ecological community?

What is the current consensus view regarding the primary cause of amphibian deformities and declines?

Biologists find that worms treated with a hormone live 1.3 days longer than untreated worms. To assess whether these differences are significant, the biologists would most likely use which aspect of the scientific process?

A rare, highly endangered bird species lives in a very remote area of the Amazonian rainforest. Almost nothing is currently known about this species' diet, behavior, life-span, breeding system, or its interactions with other species. Ecological research can be conducted at five major levels or scales (note that one has already been entered into the table). Complete the table, listing the four other potential levels of ecological study in order from the lowest to the highest level. For each level, list one potential research question that could be asked in a study of the endangered bird species.

A group of individuals of a single species of swamp sparrows lives in the Quabbin Reservoir in Massachusetts, and these individuals interact with one another. This is an example of a(n)

Biologists find that tomato plants treated with an insecticide produce 2.2% more tomatoes compared to untreated plants. To assess whether these differences are significant, the biologists would most likely use

Which quality is a biotic feature of the environment?

Refer to the figure. -The figure is based on studies of the effects of pesticides on the tadpole immune system. In a laboratory experiment, wood frog (Rana sylvatica) tadpoles were exposed to low or high concentrations of a pesticide, and then Ribeiroia parasites. The tadpoles were then examined for (A) numbers of eosinophils and (B) numbers of Ribeiroia cysts. Error bars show one SE of the mean. Which statement is supported by the evidence shown in the figure?

Ecologists try to reduce the likelihood that variables that are not under the control of the experimenter will unduly influence the results of an experiment by

Refer to the figure. The figure represents an ecological study done by Carson and Root to study how herbivorous insects affected a plant community. Based on the figure, what type of study were Carson and Root most likely performing?

An ecologist studying ecosystems would be most interested in which question?

A team of researchers is investigating the effects of fertilizer on the growth of forest trees. They use an old Christmas tree plantation with pine trees of the same species and age, and divide a section of the plantation into 60 plots. They separate the plots into two groups of 30. They apply high fertilizer levels to the group to the east of the plantation and low fertilizer levels to the western group. They set up the experiment to run for ten years and measure growth of all trees at the end of each year. Discuss the validity of the experimental design, concentrating on the formation of treatment groups and the use of controls. Based on this design, would the researchers be able to draw valid conclusions about the effect of fertilizer on tree growth rates? Why or why not?

A team of researchers is investigating the effects of fertilizer on the growth of forest trees. They use an old Christmas tree plantation with pine trees of the same species and age, and divide a section of the plantation into 4,000 plots, with each plot measuring 10 cm * 10 cm. They separate the plots into two groups of 2,000 and apply different amounts of fertilizer to the two groups. They collect data on tree growth in each plot for 12 hours and quantify the growth rates with high and low fertilizer applications. Discuss the validity of this design, concentrating on possible spatial and temporal flaws. Based on this experimental design, would the researchers be able to draw valid conclusions about the effect of fertilizer on tree growth rates? Why or why not? Consider the spatial and temporal scales of the design.

How do connections in nature lead to unanticipated side effects in the case of amphibian deformities?

A plant species has two different varieties, the characteristics of which are heritable. One grows very quickly to a large size, while the other grows slowly and remains small. The large plants produce 500 seeds when they reproduce; 20 of those seeds sprout and survive to become large adult plants. The small plants produce 100 seeds; 40 of those seeds sprout and survive to become small adult plants. Which variety is more likely to be better adapted to its environment?

An ecologist wants to study a large forest ecosystem which was last studied more than 50 years ago. She hopes to document the changes that have occurred in plant species composition, in light of recent global warming. She will probably begin her study using which method?