CHAPTER 34 The Biosphere: An Introduction to Earth's Diverse Environments Modules 34.7 – 34.11

34.7 Oceans occupy most of Earth's surface AQUATIC BIOMES 34.7 Oceans occupy most of Earth's surface Oceans cover about 75% of the Earth's surface Light and the availability of nutrients are the major factors that shape aquatic communities

Estuaries are productive areas where rivers meet the ocean The saltiness of estuaries ranges from less than 1% to 3% They provide nursery areas for oysters, crabs, and many fishes They are often bordered by extensive coastal wetlands Figure 34.7A

The intertidal zone is the wetland at the edge of an estuary or ocean, where water meets land Salt marshes, sand and rocky beaches, and tide pools are part of the intertidal zone It is often flooded by high tides and then left dry during low tides Figure 34.7B

Abiotic conditions dictate the kinds of communities that ocean zones can support Intertidal zone Continental zone Photic zone Pelagic zone Benthic zone (seafloor) Aphotic zone Figure 34.7C

The pelagic zone is the open ocean It supports highly motile animals such as fishes, squids, and marine mammals Phytoplankton and zooplankton drift in the pelagic zone The benthic zone is the ocean bottom It supports a variety of organisms based upon water depth and light penetration

The aphotic zone is a vast, dark region of the ocean The photic zone is the portion of the ocean into which light penetrates Photosynthesis occurs here The aphotic zone is a vast, dark region of the ocean It is the most extensive part of the biosphere Although there is no light, a diverse and dense population inhabits this zone

Coral reefs are easily degraded by Coral reefs are found in warm tropical waters above the continental shelf They support a huge diversity of invertebrates and fishes Coral reefs are easily degraded by pollution native and introduced predators human souvenir hunters Figure 34.7D

Lake and pond communities are shaped by 34.8 Freshwater biomes include lakes, ponds, rivers, streams, and wetlands Lake and pond communities are shaped by light temperature the availability of nutrients and dissolved oxygen

A river environment changes greatly between its source and its mouth Temperature, nutrients, currents, and water clarity vary at different points Figure 34.8A

Wetlands are among the richest biomes in terms of species diversity Figure 34.8B

34.9 Terrestrial biomes reflect regional variations in climate Climatic differences, mainly temperature and rainfall, shape the major biomes that cover Earth's land surface Biomes tend to grade into each other Within each biome there is local variation This gives vegetation a patchy, rather than uniform, appearance

Major terrestrial biomes 30º N Equator 30º S Tropical forest Polar and high-mountain ice Temperate deciduous forest Savanna Chaparral Coniferous forest Desert Temperate grassland Tundra (arctic and alpine) Figure 34.9

34.10 Tropical forests cluster near the equator Several types of tropical forests occur in the warm, moist belt along the equator Figure 34.10

The tropical rain forest is the most diverse ecosystem on Earth Large-scale human destruction of tropical rain forests continues to endanger many species It may also alter world climate

34.11 Talking About Science: Ecologist Arial Lugo studies tropical forests in Puerto Rico The Luquillo Experimental Forest in Puerto Rico allows ecologists to study the effects of disruption on tropical forests It contains deforested as well as still-forested areas Figure 34.11B

The forest ecologist Dr The forest ecologist Dr. Ariel Lugo has been one of the key scientists at the Luquillo Experimental Forest He and other scientists have offered valuable insight into the peril these forests face as well as the promise they hold Studies indicate that tropical forests recover from natural disasters much more readily than they do from human destruction Figure 34.11A