Unit 1 Ecology D1

Which species would most likely represent humans if they were part of this ecosystem?

• A

• B

• C

• D

Which species represents a photosynthetic organism?

• A

• B

• C

• D

Which species are herbivores?

• A

• B

• C

• D

Which species are most likely to be omnivores?

• A

• B

• C

• D

The food web above represents feeding relationships in a biological community near a deep-sea hydrothermal vent. Hydrothermal vents are geysers on the seafloor that gush super-heated, mineral-rich water. The seawater surrounding hydrothermal vents typically contains carbon dioxide (CO2), molecular hydrogen (H2), hydrogen sulfide (H2S), and methane (CH4). Sunlight, however, fails to reach the seafloor where deep-sea hydrothermal vents are located. As part of an investigation, researchers collected living specimens from an area near a deep-sea hydrothermal vent. Mussels in the collection were found to be dependent on molecular hydrogen in seawater. Also, the researchers discovered multiple species of bacteria living in the gills of the mussels. Mussels use gills for filter-feeding and gas exchange with the surrounding seawater. On the basis of their experimental results, the researchers hypothesized that some bacteria living in the gills of the mussels are capable of chemosynthesis.

Which of the following best explains how biological communities near deep-sea hydrothermal vents can exist in a habitat lacking sunlight?

• Environmental conditions on some distant planets resemble those experienced by organisms living near hydrothermal vents.

• Heterotrophs metabolize carbon-containing compounds produced by the photosynthetic organisms that live on the seafloor.

• Some organisms rely on energy captured from inorganic compounds to drive basic biological processes.

• Some organisms that can tolerate high temperatures are single celled, whereas others are multicellular.

Zebra mussels are an invasive species that has become widely established throughout the United States. Figure 1 shows the percent change in the population sizes of selected groups of organisms in the Hudson River since the introduction of zebra mussels. In this study chlorophyll-containing bacteria are considered phytoplankton and all other bacteria are considered bacterioplankton. What can be inferred from the data?

• The introduction of zebra mussels led to an increase in the population size of phytoplankton.

• The introduction of zebra mussels led to a decrease in the population size of bacterioplankton.

• The introduction of zebra mussels had no significant impact on the population sizes of the studied organisms.

• The introduction of zebra mussels led to a decrease in the population size of phytoplankton.

Zebra mussels are an invasive species that has become widely established throughout the United States. Figure 1

shows the percent change in the population sizes of selected groups of organisms in the Hudson River since the

introduction of zebra mussels. In this study chlorophyll-containing bacteria are considered phytoplankton and all

other bacteria are considered bacterioplankton.

Which hypothesis about the effect of zebra mussels on the Hudson River community is best supported by the data in Figure 1?

• Shoreline fish have replaced open water fish as top predators in a stable community.

• Zebra mussels have integrated into the existing community with little effect on the community stability.

• The reduction in primary productivity has resulted in an unstable community that will eventually collapse.

• Bacterioplankton have replaced phytoplankton as the energy harvesters in the community.

A group of biologists were investigating the effects of light color on phototropism (growing toward the light source)

in tomato plants. Four groups of tomato plants were grown in the same greenhouse under identical conditions. Each

group was then placed in a different room, each room having a different color of light, exposed to that single color

of light from different directions for one week at a time. After each week, the biologists counted the number of

tomato plants in the groups that were showing evidence of phototropism. The results are summarized in Table 1.

Which of the following correctly identifies the dependent and independent variables in this experiment?

• The color of the light is the dependent variable, and the percentage of plants showing phototropism is

  the independent variable.

• The percentage of plants showing phototropism is the dependent variable, and the color of the light is

  the independent variable.

• The direction of the light is the dependent variable, and the percentage of plants showing phototropism

  is the independent variable.

• The color of the light is the dependent variable, and the direction of the light is the independent variable.

Assume there are 50,000 joules (J) of energy available in trophic level II in the figure. According to the

conventional model of energy flow in ecosystems, which of the following statements correctly describes the flow of

energy in the system?

• Trophic level I generates a maximum of 50,000 J of energy.

• Trophic level I has approximately 5,000 J of available energy.

• Trophic level III has approximately 50 J of available energy.

• Trophic level IV has approximately 500 J of available energy.

The diagram here is called a trophic pyramid. It shows trophic levels of a grassland habitat. The size of each trophic level represents biomass, with producers representing the largest amount of biomass.

Which of the following best explains the unique shape of the trophic pyramid?

• The higher levels of the pyramid are smaller due to human interference with those organisms.

• Decomposers work more rapidly breaking down animal tissue than plant tissue.

• The organisms on the lower level of the pyramid tend to be smaller in size.

• The higher levels of the pyramid are smaller due to the inefficiency of energy transfer.