How Ecosystems Change

One choice contains ONLY biotic (Relating to or resulting from living things, especially in their ecological relations.) factors that might be found in a home aquarium’s environment. That is

• fish, snail, and plants.

• fish, snail, and gravel.

• water, gravel, and the glass wall of the aquarium.

• fish, dissolved oxygen, and bacteria living in the water.

The graph shown above is from one of the most well-known and on-going ecological studies ever performed. Isle Royal National Park, an island on Lake Superior, keeps data of populations of wolves and moose living there. The moose are a major food source for the wolves.

Analyze the graph data to conclude how the moose population affects the population of wolves.

• As moose populations increase, wolf populations immediately increase.

• As wolf population falls, moose populations fall with a delayed effect.

• Moose populations don't really show any relationship to wolf carrying capacity.

• The wolf carrying-capacity rises as moose populations increase, but with a delayed effect.

Which event would probably NOT occur if all of the decomposers could be removed from a temperate forest ecosystem?

• Discarded leaves and dead animals would pile up.

• Plants would benefit, from decreased competition with mushrooms.

• Competition for food would increase among animals in the food chain.

• The soil quality would drop and some plants would gradually begin to die.

Biologists in Louisiana have become concerned about cadmium levels in the water near New Orleans and the probability that frogs will die out. They performed an experiment on bullfrog tadpoles to determine how toxic cadmium is to bullfrogs.

Suppose a small river with a population of 10,000 frogs becomes polluted with cadmium to a level of 3 mg per gallon per day. About how many bullfrogs would be expected to die?

• about 3,000

• about 7,000

• about 8,500

• about 1,500

All but one of these is a biotic (anything that is living.) factor in this wetland. It is the

• water.

• plants.

• predators.

• migratory birds.

Steam power plants produce a large amount of extra steam. That steam is released as heat energy into the water surrounding the power plant. What effect does the increase in water temperature have on living things in the area?

• All the water evaporates.

• The animals all leave that area.

• Some organisms die in the warmer water.

• The warmer water kills all life in the area.

In nitrogen fixation, the plant obtains the nitrogen it needs to synthesize proteins, while the bacteria obtain carbon from the plant and a secure environment to inhabit within the plant roots. Which statement best explains the symbiotic relationship between the plants and the bacteria?

• Both the plants and the bacteria benefit from the process of nitrogen fixation, showing commensalism.

• The plants benefit and the bacteria are unaffected by the process of nitrogen fixation, showing commensalism.

• Both the plants and the bacteria benefit from the process of nitrogen fixation, making it a mutualistic relationship.

• The bacteria benefit and the plants are unaffected by the process of nitrogen fixation making it a mutualistic relationship.

The state of Florida recently built pathways through sections of the Everglades in an effort to boost revenue through increased tourism. The pathways were raised and had guard rails for the pedestrians' safety. But Florida officials had not planned on the mosquito population being so fierce. What would be a reasonable solution to reduce the mosquito populations near the tourist walkways?

• night-time spraying of insecticides

• importing bats to the area to eat the mosquitoes

• repeated spraying of insecticides throughout the day

• pouring insecticides into the swamp where mosquitoes lay eggs

All but one of the organisms listed depends on the successful growth of kelp beds in a marine environment. That is the

• frogs.

• sea otters.

• young fish.

• crustaceans.

There are many factors that influence life on Earth. A biotic factor affecting life on the entire planet is the

• amount of carbon dioxide in the atmosphere.

• amount of drinkable water available.

• average air and water temperature.

• number of plankton in the oceans.