CHAPTER 37 – Part II

1. CHAPTER 37 – Part II Biomes and Animal Distribution

2. Distribution of Life on Earth Terrestrial Environments: Biomes • Biome • Major biotic unit bearing a characteristic and easily recognized array of plant life • Plant distribution is easier to map, but plant formations support characteristic animal life • Biomes are distinctive but boundaries are not • Communities blend into one another • A gradient from forest to woodlands to prairies forms an ecocline • Biomes have distinctive dominant plants and animals

4. Distribution of Life on Earth • Temperate Deciduous Forest • Well-developed in eastern North America • Deciduous, broad-leafed trees such as oak, maple, and beech predominate • Deciduous trees are adapted for low-energy levels from the sun and for freezing winter conditions • In the summer, the closed canopy creates a deep shade underneath • Understory plants grow rapidly in spring or fall • Rain falls throughout the year and climate is relatively wet • Animal communities are adapted to seasonal changes • Some migrate and some hibernate

5. Distribution of Life on Earth • Coniferous Forest • Form a broad, continuous belt across Canada and Alaska and south through the Rocky Mountains into Mexico • Also continues across northern Eurasia • Dominated by evergreens: pines, fir, spruce, and cedar • Plants adapted to withstand freezing and survive with short summer growing seasons • Trees conical shape and shed snow • Northernmost edge is boreal forest, often called taiga

7. Distribution of Life on Earth • Mean annual precipitation • Less than 100 cm (40 inches) and temperatures fairly cold • Mammals include deer, moose, elk, snowshoe hares, many rodents, foxes, wolverines, lynxes, weasels, martins, and bears • Animals adapted physiologically or behaviorally for long, cold, and snowy winters • Birds adapted to the forest resources • Many mosquitoes and flies are adapted to feed on the blood of large mammals • Southern coniferous forests lack northern mammals, but have snakes, lizards and amphibians

8. Distribution of Life on Earth • Tropical Forest • Worldwide equatorial belt of tropical forests has high rainfall and constant temperatures • Nurtures luxurious, uninterrupted growth that is at a maximum in rain forests • May have up to a thousand species and none are dominant • Often stratified into six to eight feeding strata • Insectivorous birds and bats fly the air above the canopy • Middle zones have tree species such as monkeys and tree sloths, birds and amphibians

10. Distribution of Life on Earth • Climbing animals range along the trunks • Large mammals that are unable to climb forage on the forest floor • A large community of carnivores and herbivores scavenges in the litter and on trunks for food • Food webs are intricate and difficult to unravel • Litter is thin and the soil is an impoverished laterite • Most of the biomass is in the forest above

11. Distribution of Life on Earth • Grassland • North American prairie • One of the most extensive grasslands in the world • Much prairie has been transformed into the most productive agricultural region in the world • In grazing lands, nearly all native grasses have been replaced by exotic species • The bison was the dominant herbivore, but jackrabbits, antelope, and prairie dogs remain • Mammalian predators include coyotes and the now uncommon ferrets and badgers

13. Distribution of Life on Earth • Large areas of tall-grass prairie remain in Kansas and Oklahoma • Large tracts of short-grass prairie can be found in western Kansas and Nebraska • Annual rainfall is more than in deserts, less than deciduous forests, at 40–80 cm (16–31 inches)

14. Distribution of Life on Earth • Tundra • Severely cold biome in treeless Arctic regions or high mountaintops • Plant life restricted to a short growing season of about 60 days • Soil remains frozen most of the year • Annual precipitation usually less than 25 cm • Dwarf woody vegetation, lichens, grasses, and sedges predominate • Arctic animals include lemming, caribou, musk ox, arctic fox, ptarmigan, and migratory birds

16. Distribution of Life on Earth • Desert • Receives less than 25 cm of rainfall a year • Desert plants have reduced foliage, drought-resistant seeds, and adaptations to conserve water • Large desert animals are adapted for keeping cool and conserving water • Smaller animals often live in burrows or are nocturnal • Desert mammals include mule deer, jackrabbit, peccary, kangaroo rat, and ground squirrel • Desert birds include the roadrunner, cactus wren, turkey vulture, and burrowing owl • Lizards, snakes, and tortoises are numerous and many insects and arachnids are also desert adapted

17. Distribution of Life on Earth Aquatic Environments • Inland Waters • Freshwater constitutes only 2.5% of the water in the world. • Most stored in ice caps or underground aquifers Leaves only 0.01% as freshwater habitat • ¼ of the world’s vertebrates and half of fish live in freshwater • Lotic waters • Flowing and have high oxygen content • Lentic water • Standing water and has less dissolved oxygen

18. Distribution of Life on Earth • Large number of animals live on underwater substrates as benthic organisms • Nekton • Swimming freshwater organisms found in lakes and larger ponds • Plankton • Small floating plants and animals • Lakes and ponds are generally short-lived • Eventually fill up with sediment • Human pollution includes the inflow of nitrates and phosphates that cause huge algal blooms

19. Distribution of Life on Earth • Oceanic Environments • Represent largest portion of earth’s biosphere • Marine world relatively uniform, compared to land • Over 200,000 species live in oceans • 98% are benthic and live on the seabed • 2% are pelagic, swimming freely in the ocean • Of the benthic forms, most live in intertidal or shallow regions • Less than 1% live in deep ocean • Species diversity of benthic organisms increases from shallow waters to maximum at 2000–3000 m, declines at greater depths • Most productive areas occur where upwelling currents bring nutrients to sunlit photic zone • With a few exceptions, life below the photic zone lives on the “rain” of organic matter from above

20. Distribution of Life on Earth • Continental margins are closest to shore • Continental shelf extends from shore to a depth of 120–140 m • Continental slope descends sharply from the edge of the shelf to a depth of 3,000–5000 m • Continental rise is a bed of thick sediments at the base of continental slope • Beyond the continental margin lies the abyssal plain • Averaging 4,000 m depth but reaching depths of 11,000 m

22. Distribution of Life on Earth • Intertidal zone • Portion of continental shelf exposed to air during low tides • Animals in this zone experience daily fluctuations between marine and terrestrial environments • Attached forms typically have exoskeletons • Protection from dessication and physical abrasion • Consumed by predators like gastropods and seastars • Interactions between physical stress and competition often result in zonation

24. Distribution of Life on Earth • Depressions in the rocky surface may result in isolated tidepools • Sometimes support organisms not well suited to the exposed habitat • Attached seaweeds are often dispersed among the invertebrate faunas • Rocky intertidal habitats • Abundant on the northern Atlantic and Pacific coasts of North America

25. Distribution of Life on Earth • Rocky subtidal zone • Often dominated by kelps • Kelps attach to firm substrate by holdfasts and grow upward • Grazing by sea urchins and storm damage can alter kelp forest structure • Abalone, sea urchins, and limpets graze Pacific kelp forests • Suspension-feeding mussels and their crustacean predators are abundant • Sea otters increase kelp density by removing sea urchins

27. Distribution of Life on Earth • Coral reefs • Occur off the coasts of continents and volcanic islands • Include atolls • Series of reefs encircling submerged volcanic island • Protect a very diverse subtidal community • Formed by mutualistic growths of corals and single-celled algae • No single species dominates • Many species inhabiting coral reefs show agonistic interactions • Mutualistic relationships also common

29. Distribution of Life on Earth • Nearshore • Soft sediments include beaches, mudflats, salt marshes, sea-grass beds, and mangrove communities • Intertidal sand flats are initially colonized by grasses, followed by a variety of invertebrates and vertebrates • Shallow coastal subtidal environments include beds of sea grasses • Along calm tropical and subtropical marine coasts, mangrove trees flourish

31. Distribution of Life on Earth • Deep sea regions • Contain mostly soft sediments, with clean sands in areas of strong currents and fine muds where currents are weak • Sandy deep sea deposits dominated by suspension-feeding invertebrates • High turbidity in muddy areas damages suspension-feeding mechanisms • Muddy substrates are rich in deposit-feeding invertebrates • Dead fish and plants fall to the sea floor, supporting bacteria and deposit feeders

32. Distribution of Life on Earth • Hydrothermal vents • Occur on the abyssal plain in areas of submarine volcanic activity • Archaebacteria form mats on rocky surfaces near vents • Bacteria are grazed by invertebrates • Some bivalves have symbiotic archaebacteria in gills • Pogonophoran worms harbor symbiotic archaebacteria • Hydrothermal vents are ephemeral

33. Distribution of Life on Earth • Estuary • Nutrient-rich transition zone where freshwater mixes with seawater • Neritic or shallow water zone • Extends to end of continental shelf • Nutrients delivered by rivers and upwellings • Algal growth is prolific. • Upwellings • Restricted to small areas • Productive fisheries centered on upwellings • Open ocean • Constitutes the pelagic realm • Except in upwellings, organisms that die here sink to the bottom

35. Distribution of Life on Earth • Polar seas • Combine upwellings with high oxygen content • Support enormous populations of krill that feed on phytoplankton. • Epipelagic layer • Surface • Mesopelagic zone • “Twilight zone” where dim light supports a community of animals

36. Distribution of Life on Earth • Bathypelagic, abyssopelagic, and hadopelagic zones • In perpetual darkness • Limited by the portion of organic debris that rains from above • Most deep ocean bottom dwellers are deposit feeders with slow growth and long lives