Summary

Ecosystems exist underground, on land, at sea, and in the air. Organisms in an ecosystem acquire energy in a variety of ways, which is transferred between trophic levels as the energy flows from the base to the top of the food web, with energy being lost at each transfer.

Earth has terrestrial and aquatic biomes. There are eight major terrestrial biomes: tropical rainforests, savannas, subtropical deserts, chaparral, temperate grasslands, temperate forests, boreal forests, and Arctic tundra. Temperature and precipitation, and variations in both, are key abiotic factors that shape the composition of animal and plant communities in terrestrial biomes. Sunlight is an important factor in bodies of water, especially those that are very deep, because of the role of photosynthesis in sustaining certain organisms. Other important factors include temperature, water movement, and salt content. Aquatic biomes include both freshwater and marine environments. Like terrestrial biomes, aquatic biomes are influenced by abiotic factors. In the case of aquatic biomes the abiotic factors include light, temperature, flow regime, and dissolved solids.

Mineral nutrients are cycled through ecosystems and their environment. Of particular importance are water, carbon, nitrogen, phosphorus, and sulfur. All of these cycles have major impacts on ecosystem structure and function. Ecosystems have been damaged by a variety of human activities that alter the natural biogeochemical cycles due to pollution, oil spills, and events causing global climate change. The health of the biosphere depends on understanding these cycles and how to protect the environment from irreversible damage.

Review Questions

1. Secondary consumers would eat which one following?

A. Producers

B. Plants

C. Herbivores

D. Carnivores

E. Tertiary consumers

2. If you are concerned about biomagnification of toxins, which one of the following would you most want to avoid eating?

A. Tuna (tertiary consumer)

B. Seaweed (producer)

C. Urchin (primary consumer)

D. Sculpin (secondary consumer)

E. Any photoautotroph

3. Which one of the following is not a biogeochemical cycle?

A. Energy cycle

B. Nitrogen cycle

C. Carbon cycle

D. Phosphorus cycle

E. Water cycle

4. Which one of the following would not increase the amount of water in the atmosphere?

A. Evaporation

B. Transpiration

C. Sublimation

D. Infiltration

E. Evapotranspiration

5. Which one of the following processes would remove nitrates from contaminated water by converting it into nitrogen gas?

A. Nitrification

B. Nitrogen fixation

C. Denitrification

D. Assimilation

E. Ammonification

6. What do deserts and chaparral have in common?

A. Dry and hot summers

B. Dominated by abundant evergreen shrubs

C. Both can exist as either the hot or cold variety

D. Very small amounts of rainfall consistently throughout the year

E. Very low biodiversity

7. Which one of the following would most likely live within the benthic realm of the ocean?

A. Squid

B. Tuna

C. Phytoplankton

D. Marine worm

E. Shark

8. What two variables most strongly contribute to the type of biome that exists in a particular area?

A. Precipitation levels and temperature

B. Type of producers and density of herbivores

C. Amount of sunlight and annual rainfall

D. Soil type and amount of O₂

E. Distance from ocean and elevation

9. The conversion of nitrogen gas (N₂) into ammonia (NH₃) happens during which specific process?

A. Ammonification

B. Dentification

C. Nitrification

D. Nitrogenous cycling

E. Nitrogen fixation

10. Use your knowledge of the relative energy content among trophic levels to answer the following question: A larger human population could be supported if all humans derived their food from which trophic level?

A. Producers

B. Primary consumers

C. Secondary consumers

D. Tertiary consumers

E. Quaternary consumers

See Appendix for answers

Attributions

Concepts of biology by OpenStax is licensed CC BY 3.0.  Modified from Original by Kamala Doršner and Matthew R. Fisher.

Essentials of Environmental Science by Kamala Doršner is licensed under CC BY 4.0.

“Review Questions” is licensed under CC BY 4.0 by Matthew R. Fisher.