Ecosystems

Which terrestrial biome features the greatest biodiversity?

• Tropical rainforest
• Savanna
• Tundra
• Desert

Which of the following is one way nitrogen atoms are returned to the atmosphere?

• burning fossil fuels

• decay

• fixation

Answer explanation

Fossil fuels contain nitrogen. When they are extracted and burned, this releases nitrogen oxides to the atmosphere.

Which of the following processes release carbon into the atmosphere?

Select all answers that apply.

• weathering

• making concrete

• forest fires

• carbon sequestration

Answer explanation

Limestone is an example of sedimentary rock that contains carbon. When limestone rock weathers, carbon is released into the atmosphere.

What is carbon sequestration?

• A method for increasing atmospheric carbon dioxide levels.
• The process of converting carbon dioxide into oxygen.
• Carbon sequestration is the process of capturing and storing atmospheric carbon dioxide to mitigate climate change.
• A technique for measuring carbon emissions in the atmosphere.

Cattle egrets are birds that live near cattle because as the cattle graze, insects in the ground are stirred up to the surface. When the insects are stirred to the surface, the birds eat the insects. The cattle are unaffected by the birds or the insects. This relationship between the cattle egrets and the cattle can best be described as:

• commensalism
• mutualism
• parasitism
• predation

In the tundra, caribou often dig through the snow in order to eat the lichens underneath. Arctic foxes sometimes follow the caribou and hunt small mammals they find in the freshly dug holes left behind by the caribou.

The above description of the fox and caribou best matches which of the following types of relationships?

• Mutualism
• Parasitism
• Commensalism
• Predation

Answer explanation

The fox benefits from the caribou, but the caribou is unaffected by the fox.

Clownfish live in the ocean. While the clownfish hatch their eggs, they hide them in and around sea anemones. When the eggs develop, the clownfish explore the ocean in search for food. If the sea anemones were damaged by strong ocean currents, what would most likely be the first thing to happen to the clownfish?

• decrease in predation

• decrease in population

• migration to freshwater

• change to a new source of food

A population of antelope normally graze on the abundant grasses in the savannah. However, a drought occurs and the amount of grass decreases. That year, many young, sick, and old antelope starve to death. A change in what variable lowered the antelope's population?

• temperature

• predation

• prometaphase

• carrying capacity

Answer explanation

Carrying capacity is the the number of organisms an ecosystem can support. Since the amount of grass (the food source) decreased, the antelope's carrying capacity decreased, which reduced their population levels.

Sand at the bottom of a ship channel is dredged and removed to a nearby island's beach. Without this removal process, which of the following would happen?

• The channel would narrow and the island would be covered with water.

• The island will move inland as the channel becomes deeper.

• The beaches would narrow and the channel would become shallower

Answer explanation

The beaches would narrow because of erosion from waves and the sand would not be replaced by the dredging process. The channel itself would become shallower as it fills with sediment deposited from the river into the delta.

The atmosphere surrounding Earth is composed of approximately 78% nitrogen. How do multicellular organisms obtain this atmospheric nitrogen?

• Surface water is absorbed into the ground, releasing nitrogen.

• Plants absorb atmospheric nitrogen from the air.

• Nitrogen-fixing bacteria release forms into the soil.

• Condensation of nitrogen drops from the clouds.

Answer explanation

For nitrogen to be converted to a usable form, it must be converted by nitrogen-fixing bacteria.

Nitrogen is not taken out of the atmosphere through condensation and precipitation, but rather by bacteria.