(outdated) Ecology

Name the stage in the nitrogen cycle in which this step occurs.

Describe how nitrogen in nitrate can be returned to the atmosphere in the form of nitrogen gas.

ecosystem

producer

habitat.

the producer

an organism feeding only as a primary consumer.

The hawks are top predators.

Name one other top predator shown in Fig. 6.1.

Name the processes in the nitrogen cycle in which the following changes occur:

nitrate ions $\longrightarrow$ nitrogen gas

______

ammonium ions $\longrightarrow$ nitrate ions

______

nitrogen gas $\longrightarrow$ ammonium ions.

______

State the ecological terms applied to each of the following descriptions of these species.

Explain the importance of nitrogen-fixing organisms, such as A. azollae, in ecosystems.

Add an arrow to Fig. 1.1 to show where the ecosystem receives its initial input of energy.

State the process represented by A.

State one type of organism that is a member of the decomposer system.

Name two processes represented by arrow B.

Explain why D. rotundifolia can be considered to be both an autotroph and a heterotroph.

In 1999, Dutch scientists discovered a new reaction, the anammox reaction, to add to the nitrogen cycle. They discovered the bacterium Brocadia anammoxidans that converts ammonia, nitrite ions and nitrate ions to nitrogen gas ($\text{N}_2$) in anaerobic environments.

The reaction carried out by these bacteria is thought to be responsible for the loss of a large quantity of nitrogen-containing compounds from marine ecosystems, such as the oceans.

Suggest and explain the effect that this reaction has on marine ecosystems.

Name processes A, B and C.

A ______
B ______
C ______

Dead animal and plant material can also contribute to the pool of inorganic nitrogen in soil.

Describe how this happens.

State one use for phosphate and one use for nitrate in organisms.

phosphate ______
nitrate ______

Nitrogen and phosphate are both cycled more rapidly in ecosystems where there are high rates of growth within trophic levels and high rates of energy flow between trophic levels.

With reference to the use of both nitrogen and phosphate in organisms, explain this statement.

Explain the meaning of the terms niche and community.

niche ______

community ______

With reference to the food web in Fig. 6.1, suggest why sea otters are considered to be a keystone species.

Suggest how the efficiency of energy transfer from kelp to sea urchins could be determined.

Explain the ecological terms population and community, using examples given in the passage.

population = ______

community = ______

Suggest why the sloth and its fur can be described as a small ecosystem.

state the meaning of the terms habitat and community

habitat = ______
community = ______

name the producer in the pond ecosystem

describe the features of producers.

Explain why only some of the energy taken in by the catfish is used to increase biomass.

In the wild, only about 10% of the energy taken in by the catfish in their food is used to increase biomass.

Suggest why this percentage is lower in the wild than in the pond.

Name the trophic levels occupied by the following organisms in the food web in Fig. 4.1:

kelp ______

arrow worms ______

narwhals. ______

The population of polar bears in the Lancaster Sound area is quite small in comparison to populations of animals that feed on Arctic cod.

Using only the information shown in Fig. 4.1, explain why the population of polar bears is small.

Populations of many fish species are under threat of extinction as a result of over-fishing.

Explain the likely consequences of over-fishing of Arctic cod.