BIO 12D - Carbon and Nitrogen Cycle

Atmospheric nitrogen has to be combined with other elements, or fixed, in order to be used by plants. Lightning is one way that nitrogen is fixed. When lightning occurs, the extreme heat breaks the bonds in nitrogen molecules, allowing nitrogen to combine with oxygen and form nitrogen oxides. In what way is most of the nitrogen fixed by lightning made available for use by plants?

• It is moved by the wind toward dry areas.

• It is incorporated into the exoskeletons of flying insects that eat plants.

• It is inhaled and exhaled by birds roosting in trees during rainstorms.

• It is carried by rain to the soil.

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Scientists have observed many types of tropical fish moving beyond their traditional ocean ranges into waters that have historically been more temperate. These fish compete for food with native fish, consuming much from the kelp forests and beds of sea grass.

The expansion of the ranges of tropical fish was most likely caused by-

• agricultural runoff that contributes to dead zones in the ocean

• global droughts that raise the salt concentration of ocean waters

• the rising temperatures of ocean waters

• acid rain pollution that lowers the pH of ocean waters

In the mid-1980s an aggressive strain of algae known as Caulerpa was accidentally introduced into the Mediterranean Sea when a seaside aquarium cleaned out its tanks. The algae contain a toxin that prevents native herbivores from consuming it. Caulerpa quickly spread over the sea floor, crowding out many species including sponges, corals, sea fans, and lobsters.

Which statement explains the most likely impact Caulerpahas had on the biodiversity in the Mediterranean Sea?

• The presence of Caulerpa within an ecosystem in an indicator of the ecosystem's health.

• The spread of Caulerpa improved the habitat for many species of sea grasses and increased the biodiversity.

• Caulerpa interbred with native species with the same adaptations within the ecosystem.

• Caulerpa became dominant within the ecosystem and reduced the biodiversity

The diagram shows the flow of organic molecules through an ecosystem. One process that occurs in this ecosystem is labeled X, and another process that occurs is labeled Y. Which two processes are identified by the labels X and Y?

• X= Respiration and Y = Predation

• X = Adaptation and Y = Decomposition

• X = Fermentation and Y = Fixation

• X = Decomposition and Y = Respiration

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All of the organisms in a typical ecosystem are interdependent, helping to maintain the equilibrium of the ecosystem and sustaining each other. Which of the following processes can bacteria perform that is not possible for the other members of a typical ecosystem?

• converting radiant energy into chemical energy

• conserving water

• using nitrogen from the atmosphere

• decomposing the remains of dead organisms

The release of nitrates into a pond leads to an algae bloom. Algae grow and reproduce rapidly under high nutrient availability, but each alga is short lived, and the result is a high concentration of dead organic matter which starts to decay. This decay disrupts the pond ecosystem by reducing the available —

• nitrates, thereby killing fish

• sunlight, thereby killing water plants

• water, thereby killing insects

• oxygen, thereby killing fish

All of the organisms in an ecosystem are interdependent, helping to maintain the equilibrium of the ecosystem. Which of the following processes can bacteria perform that is not possible for the other members of a typical ecosystem?

• absorbing energy from sunlight

• preventing the erosion of topsoil

• using nitrogen from the atmosphere

• decomposing the remains of organisms

If organism 1 removes carbon from the abiotic atmosphere storage bank and brings it into the biotic ecosystem, it would best be described as a –

• Producer

• Herbivore

• Carnivore

• Decomposer

It is estimated that about one half of all commercial fertilizers ever produced have been applied to crops in the last 20 years. Of this fertilizer, only about half is incorporated into plant tissue and the remainder enters the environment. Which of these natural cycles is this most likely to impact?

• Nitrogen

• Carbon

• Oxygen

• Rock

Some species of fungi, protists, and bacteria all play a vital role in every biogeochemical cycle. Which best identifies the function of these organisms?

• releasing oxygen into the atmosphere

• inhibiting the growth of other organisms in an ecosystem

• taking energy from the environment and producing organic molecules

• returning basic nutrients back to the ecosystem so that they can be used by other organisms

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