Chapter 5: Principles of Ecology Biomes and Aquatic Life Zones

Chapter 5: Principles of Ecology Biomes and Aquatic Life Zones

5.1 Weather and Climate: An Introduction Weather refers to daily conditions such as rainfall and temperature. Climate is the average weather over a long period. Climate determines the plant and animal life of a region.

The Earth is unequally heated, which creates three major climatic zones: Tropical Temperate Polar Major Factors That Determine Weather and Climate Figure 05.01: Climate zones. The Earth s surface can be roughly divided into the three major climate zones shown here.

Figure 05.02: Global air circulation.

The Coriolis Effect Air tends to flow from the equator to the poles. Weather within the major climatic zones is altered by wind flow patterns. Wind flow patterns are profoundly influenced by the spin of the Earth.

Topography Weather is also affected by topography, especially mountain ranges. Figure 05.03: Rain shadow effect. This shows the effect of mountain ranges on rainfall.

Ocean Currents Warm water from the equator flows toward the poles. This warms landmasses near which it passes. Figure 05.04: Major ocean currents.

5.2 The Biomes The Earth s surface can be divided into biologically distinct zones called biomes. Each has a distinct climate and unique assemblage of plants and animals. Regional variations occur within each biome.

Figure 05.05: The Earth s biomes.

The Tundra The Arctic tundra, the northernmost biome, is characterized by the harshest climate. Because the growing season is so short, life on the Arctic tundra is extremely vulnerable to human actions. Courtesy of U.S. Fish & Wildlife Services

Photodisc Photodisc Figure 05.07A: Tundra species. (a) The ptarmigan and (b) musk ox are both well adapted for life in the cold Arctic tundra. Courtesy of U.S. Fish & Wildlife Services

Figure 05.08: Arctic oil. Oil development on Alaska s North Slope causes significant alteration of the delicate tundra, as shown here. Hugh Rose/Accent Alaska

The Taiga The taiga is a band of coniferous trees spreading across the northern continents south of the tundra. Its climate is milder, and its life-forms are more diverse than those of the tundra.

Photodisc/Getty Images The taiga supports many large populations of wild animals. The forests of this region are under heavy pressure to meet rising demands for wood and wood products. Figure 05.09: Old-growth forests such as these contain species that cannot survive in younger forests.

The Temperate Deciduous Forest Biome The temperate deciduous forest biome occurs in regions with abundant rainfall and long growing seasons. This biome has been heavily settled by humans and dramatically altered.

Photodisc Photodisc Figure 05.11AB: Animals of the temperate deciduous forest. (a) Black bear, (b) white-tailed deer. Snehit/ShutterStock, Inc.

The Grassland Biome The grassland biome occurs in regions of intermediate precipitation enough to support grasses but not enough to support trees. On most continents, the rich soil of the biome has been heavily exploited by humans for agriculture.

MedioImages/Photodisc/age fotostock Figure 05.12: Grassland biome.

The Desert Biome The desert biome is characterized by dry, hot conditions. Often, it abounds with plants and animals adapted to the heat and lack of moisture. The world s deserts are expanding because of human activities such as overgrazing livestock and the production of greenhouse gases.

Photos.com Arco Images GmbH/Alamy Images Figure 05.17AB: Animals of the desert. (a) Gila monster and (b) ringtail. SuperStock/age fotostock

The Tropical Rain Forest Biome The tropical rain forest is the richest and most diverse biome on Earth because of its abundant rainfall and warm climate.

Photodisc Figure 05.18: Tropical rain forest. This endangered biome covers vast areas and is rich in species. Photodisc

Rain Forests About half of the world s rain forest has been destroyed. Huge tracts could be eliminated in the near future, with devastating effects on climate, plants, and wildlife if current trends continue.

Altitudinal Biomes Because climate varies with altitude, the distribution and abundance of life also change. Figure 05.19: Altitudinal biomes.

Alpine tundra Figure 05.20: Alpine tundra. Harald Høiland Tjøstheim/ShutterStock, Inc.

5.3 Aquatic Life Zones Aquatic systems are divided into distinct regions, known as aquatic life zones. They may be freshwater or saltwater. The abundance of life is determined by energy and nutrient levels. Phytoplankton form the base of aquatic food chains.

John D. Cunningham/Visuals Unlimited Cabisco/Visuals Unlimited T.E. Adams/Visuals Unlimited Figure 05.21A: Phytoplankton. Unicellular algae like these are called phytoplankton and form the base of many aquatic food chains. Figure 05.21B: Phytoplankton. Unicellular algae like these are called phytoplankton and form the base of many aquatic food chains. Figure 05.22: Zooplankton. These organisms feed on algae and are consumed by small fishes.

Freshwater Lakes Each has very different conditions and, consequently, very different life-forms. Lakes are divided into four regions: the littoral zone the limnetic zone the profundal zone the benthic zone Figure 05.23: Zones of a lake.

Figure 05.24: Thermal stratification and turnover in lakes.

Rivers and Streams Rivers and streams are complex ecosystems that rely more on agitation for oxygenation of their waters than lakes do. Many nutrients in streams that support aquatic life come from neighboring terrestrial ecosystems. The quality of water in a stream is profoundly influenced by activities in the watershed.

Protecting Freshwater Ecosystems Like lakes and ponds, streams are selfpurging but extremely vulnerable to pollution if sources exceed the capacity to self-cleanse.

Courtesy of Mr. Mohammed Al Momany, Aqaba, Jordan/NOAA krishnacreationz/shutterstock, Inc. Saltwater Life Zones The oceans cover over 70% of the Earth s surface The oceans can be divided into ecologically distinct life zone Figure 05.27: The coral reef is bathed in sunlight and found in warm water. These features and ample nutrients make it the richest of all marine aquatic zones. Figure 05.28A: Coral reef inhabitants. Coral reefs house some of the most spectacular fishes known to science.

The Coastal Life Zones The coastlines are highly productive waters. They are characterized by abundant sunlight and a rich supply of nutrients, both of which contribute to an abundance of life-forms. Figure 05.27: The coral reef is bathed in sunlight and found in warm water. These features and ample nutrients make it the richest of all marine aquatic zones. Courtesy of National Estuarine Research Reserve Collection/NOAA

Figure 05.25: Coastal wetland. Aerial view of an estuary and mangrove swamp. Courtesy of National Estuarine Research Reserve Collection/NOAA

The Coastal Life Zones Estuaries are nutrient-rich zones at the mouths of rivers. They are often associated with coastal wetlands, together forming the estuarine zone. The estuarine zone is highly productive and of great value to humans and other species. Human activities severely threaten this important biological asset.

The Coastal Life Zones The shorelines of the world are rocky or sandy regions. They are home to a surprising number of organisms adapted to the tides and the turbulence created by wave action. Coral reefs are the aquatic equivalent of the tropical rain forests and are being rapidly destroyed.

The Marine Ecosystem The marine ecosystem consists of four ecologically distinct life zones, similar to those found in lakes. Figure 05.28B: Brightly colored anemones filter food from the water. Photos.com

Figure 05.29: Ocean zones.