3: Terrestrial and Aquatic Biomes

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Desert bighorn sheep in the Hellhole Canyon in the Anza-Borrego Desert State Park. — Figure \(\PageIndex{1}\): Desert Bighorn Sheep are native to the deserts of the United States West and Southwest. A desert is a terrestrial biome that receives no more than 10 inches of rainfall per year. Deserts can be found on every continent and cover about one-fifth of Earth's land area. Water is scare and and, consequently, living conditions are hostile for plant and animal life. The desert bighorn sheep has adapted to this set of environmental conditions and unlike most mammals, their body temperature can safely fluctuate several degrees. They may go without visiting water for weeks or months, sustaining their body moisture from food and from rainwater collected in temporary rock pools. They may have the ability to lose up to 30% of their body weight and still survive. After drinking water, they quickly recover from their dehydrated condition. Wildlife ecologists are just beginning to study the importance of this adaptive strategy, which has allowed small bands of desert bighorns to survive in areas too dry for many of their predators.(CC-BY-SA 3.0; Andrew Barna via Wikimedia)

Chapter Summary

Earth’s biomes can be either terrestrial or aquatic. Terrestrial biomes are based on land, while aquatic biomes include both ocean and freshwater biomes. The location of Earth's major terrestrial biomes are determined by the average temperature and rainfall which affect the dominant type off vegetation and animal life that can exist in broad geographical regions. The aquatic biome is the largest of all the biomes, covering about 75 percent of Earth’s surface. Abiotic factors such as light, temperature, flow, and dissolved nutrients are important for determine the composition of plant and animal communities including estuaries, coral reefs, and kelp Forests.

Learning Objectives

After reading this chapter you should be able to:

Explain the difference between abiotic and biotic factors that influence life.
Explain why temperature and precipitation are the most influential abiotic factors.
Define Biogeography and endemic species.
Recognize distinguishing characteristics of each of the eight major terrestrial biomes.
Describe important abiotic factors influencing aquatic biomes and characteristics of each biome.
Compare and contrast the characteristics of the ocean zones.

3.1: Biogeography and Species Distributions
Biogeography studies the distribution of living things and how abiotic factors like temperature and rainfall impact the composition of plant and animal communities. Species distribution patterns are based on the influence of environmental factors during the very long periods of time required for species evolution.
3.2: Terrestrial Biomes
The eight major terrestrial biomes on Earth are each distinguished by characteristic temperatures and amount of precipitation. Annual totals and fluctuations of precipitation, as well as temperature variation on a daily and seasonal basis, affect the dominant type off vegetation and animal life that can exist in broad geographical regions. Since a biome is defined by climate, the same biome can occur in geographically distinct areas with similar climates.
3.3: Aquatic Biomes
The aquatic biome is the largest of all the biomes, and is dominated by its unique medium (water). This biome is usually divided into two categories: freshwater and marine. Typically, freshwater habitats are less than 1 percent salt and includes: ponds, lakes, rivers, streams, wetlands and estuaries. Marine life, however, has to be adapted to living in a habitat with a high concentration of salt. Marine habitats include the ocean and salty seas and are often subdivided further into zones or real