Ecology 260 Ch 3 Notes
Ecology 260 Ch 3 Notes Bio 260
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This 7 page Class Notes was uploaded by Michaela Humby on Thursday January 14, 2016. The Class Notes belongs to Bio 260 at University of Tennessee - Knoxville taught by Charles Price in Spring 2016. Since its upload, it has received 45 views. For similar materials see Ecology in Biology at University of Tennessee - Knoxville.
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Date Created: 01/14/16
Chapter 3-‐ These notes include class notes, extra notes from the book, and extra things the professor stated in class. The biosphere is the zone of life on Earth. It lies between: • the lithosphere—Earth’s surface crust and upper mantle and • the troposphere—the lowest layer of the atmosphere • Most living things occur within a thin layer of Earth’s surface, from the tops of trees to the surface soil layers, and within 200 meters of the surface of the oceans. CONCEPT 1 Terrestrial biomes are characterized by the growth forms of the dominant vegetation. Biomes are large-‐scale terrestrial communities shaped by the physical environment, categorized by dominant plant forms and characteristics such as leaf deciduousness(deciduous trees) or succulence (ex-‐ cacti). • Plants occupy sites for a long time and are good indicators of climatic conditions and disturbances, they reflect the prevailing environment Convergence: Evolution of similar growth forms among distantly related species in response to similar selection pressures. In the same climate, they reach the same solution to stay alive in that climate. • Distribution of the terrestrial biomes is determined by Earth’s climate zones. • Example-‐ major deserts at 30 degrees North and South • Topography, ocean currents, and other factors also help determine biome distribution. • Temperature has direct physiological effects on plant growth form. • Precipitation and temperature act together to influence water availability and water loss by plants. • Water availability and soil temperature determine the supply of nutrients in the soil. • Average annual temperature and precipitation can predict biome distributions quite well, but seasonal variation is also important. • Climate extremes can sometimes be more important than average conditions. • Human activities can also influence the biome Climate diagrams are graphs of average monthly temperature and precipitation at a location, showing the characteristic seasonal climate pattern. The axes are scales so that 1 degree Celsius corresponds to 2 mm of precipitation • Plot avg annual precipitation on the X axis and the avg annual temperature on the y-‐axis 9 Biomes 1. Tropical Rainforest 2. Tropical Seasonal Forest and Savannas 3. Temperate Evergreen Forests 4. Temperate Deciduous Forests 5. Boreal Forests Chapter 3-‐ These notes include class notes, extra notes from the book, and extra things the professor stated in class. 6. Temperate Grasslands 7. Temperate Shrublands 8. Deserts 9. Tundra Tropical Rainforests: • Predictable and consistent precipitation to temperature correspondence • Between 10°N and 10°S • Annual precipitation > 2000 mm • No seasonal changes • High biomass, high diversity—about 50% of Earth’s species • Broadleaved evergreen and deciduous trees • Light is a key factor—plants must grow very tall above their neighbors or adjust to low light levels. • Emergents rise above the canopy. • Lianas (woody vines) and epiphytes use the trees for support. • Understory trees grow in the shade of the canopy, and shrubs and forbs occupy the forest floor. Tropical Seasonal Forests and Savannas • Precipitation and temperature varies • North and south of the wet tropics • Wet and dry seasons associated with movement of the ITCZ • Shorter trees, deciduous in dry seasons, more grasses and shrubs This biome includes: • Tropical dry forests • Thorn woodlands—trees have heavy thorns to protect from herbivores • Tropical savannas—grasses with intermixed trees and shrubs • Fires promote establishment of savannas; some are set by humans. • In Africa, large herbivores—wildebeests, zebras, elephants, and antelopes—also influence the balance of grass and trees. • On the Orinoco River floodplain, seasonal flooding promotes savannas. Deserts: • Temperature exceeds precipitation • In high pressure zones at 30°N and S • High temperatures, low moisture • Sparse vegetation and animal populations • Low water availability constrains plant abundance and influences form • Many plants have succulent stems that store water. • Convergence of this form is shown by cacti (Western Hemisphere) and euphorbs (Eastern Hemisphere). Chapter 3-‐ These notes include class notes, extra notes from the book, and extra things the professor stated in class. • Desert plants also include drought-‐deciduous shrubs, grasses, and short-‐ lived annual plants that are active only after a rain. • Abundance may be low but species diversity can be high. Temperate Grasslands: • Between 30° and 50°N latitude • Warm, moist summers and cold, dry winters • Grasses dominate; maintained by frequent fires and large herbivores such as bison • Grasses grow more roots than stems and leaves, to cope with dry conditions. • This results in accumulation of organic matter and high soil fertility. • Most fertile grasslands of central North America and Eurasia have been converted to agriculture. Temperate Shrublands and Woodlands: • Between 30° and 40°N latitude • Evergreen shrubs and trees • Mediterranean-‐type climates—wet winters and hot, dry summers • Fire is common and helps maintain the biome • Evergreen leaves allow plants to be active during cooler, wetter periods. • They also lower nutrient requirements—the plants do not have to develop new leaves every year. • Sclerophyllous leaves—tough and leathery—deter herbivores and prevent wilting. • After fires, shrubs sprout from underground storage organs or produce seeds that sprout and grow quickly. • Without regular fires at 30-‐ to 40-‐year intervals, shrublands may be replaced by forests. • Shrublands in continental interiors occur in rain shadows and seasonally cold climates. Temperate Deciduous Forests: • 30° to 50°N, on continental edges with enough rainfall for tree growth • Leaves are deciduous in winter • Oaks, maples, and beeches occur everywhere in this biome • Species diversity lower than tropical rainforests • Fertile soils and climate make this biome good for agriculture. Very little old-‐ growth temperate forest remains. • As agriculture has shifted to the tropics, temperate forests have regrown. • Shifts in species composition are due to nutrient depletion by agriculture and due to invasive species such as chestnut blight. Temperate Evergreen Forests: • 30° to 50°N and S, coastal, continental, and maritime zones • Lower diversity than tropical and deciduous forests • Leaves tend to be acidic, and soils nutrient-‐poor • Temperate evergreen rainforests are located on west coasts, at 45– 50°. Chapter 3-‐ These notes include class notes, extra notes from the book, and extra things the professor stated in class. • They receive high rainfall amounts and have mild winters. Boreal Forests (Taiga): • 50° to 65°N • Long, severe winters • Permafrost (soil that remains frozen year-‐round) prevents drainage and results in saturated soils • Trees present are conifers—pines, spruces, larches—and birches • Cold, wet conditions in boreal soils limit decomposition, so soils have high organic matter. • In summer droughts, forest fires can be set by lightning and can burn both trees and soil. • In low-‐lying areas, extensive peat bogs form. Tundra: • Above 65° latitude, mostly in the Arctic • Cold temperatures, low precipitation • Short summers with long days • Vegetation is sedges, forbs, grasses, low-‐growing shrubs, lichens, and mosses • Widespread permafrost CONCEPT 2: Biological zones in freshwater ecosystems are associated with the velocity, depth, temperature, clarity, and chemistry of the water. Streams and lakes connect terrestrial and marine ecosystems. They process chemical elements from terrestrial systems and transport them to the oceans. Biological assemblages are characterized by both plants and animals, reflecting the greater proportion of animals in aquatic ecosystems. Land surfaces are shaped by the erosional power of flowing water. Streams and rivers are lotic (flowing water) systems. The smallest streams at high elevation are first-‐order streams. These converge to form second-‐order streams. Large rivers are sixth-‐order streams or greater. THE ordering scheme is called Horton Strahler Orderign Scheme Streams tend to form a pattern of riffles and pools, with different biological communities. Riffles: Fast moving water with coarse particles on the stream bed-‐ go over rocks and stuff Pools: Deeper water, with slower flow and finer sediments. The river continuum concept describes changes in biological communities with stream order and channel size. Benthic zone organisms are bottom dwellers and include many kinds of invertebrates. Some feed on detritus (dead organic matter), others are predators. Chapter 3-‐ These notes include class notes, extra notes from the book, and extra things the professor stated in class. Some live in the hyporheic zone—the substratum(zone) below and adjacent to the stream where there are lots of invertabrates too (silky and sandy down there too) • As streams increase in size, detritus from riparian vegetation decreases and becomes less important as a food source; fine organic matter, algae, and macrophytes become more important. • Feeding styles of organisms also change: from shredders that tear up and chew leaves, to collectors that collect fine particles from the water. Lakes and still waters (lentic) occur where depressions in the landscape fill with water. Lakes can be formed by glacial processes, from river oxbows (where river bends back on itself), in volcanic craters, in tectonic basins, or by damming streams. Lake depth and area influence the composition of biological communities. Deep lakes with relatively small surface area tend to be nutrient-‐poor(limited photic zone vs a shallow lake). Shallow lakes with relatively large surface area tend to be nutrient rich. Pelagic zone: Open water; dominated by plankton (small and microscopic organisms suspended in the water). Phytoplankton are photosynthetic, restricted to the upper layers through which light penetrates (photic zone). Zooplankton are nonphotosynthetic protists and tiny animals. The littoral zone is near shore, where the photic zone reaches the bottom. Macrophytes(big plants) occur in this zone. In the benthic zone, detritus from the littoral and pelagic zones is food for animals, fungi, and bacteria. This zone may be cold and have low oxygen. Concept 3 Marine biological zones are determined by ocean depth, light availability, and the stability of the bottom substrate. Marine zones next to continents are influenced by local climate, tides, waves, and inputs from the land. Tides: Ocean water rises and falls in most nearshore zones twice daily. Tides produce unique transition zones between terrestrial and marine environments. Estuaries occur where rivers flow into oceans. Salinity varies as fresh water from the river mixes with salt water from the sea. Rivers also bring in terrestrial sediments and nutrients, contributing to the productivity of estuaries. Salt marshes: Shallow coastal wetlands dominated by grasses and rushes. Terrestrial nutrients enhance productivity. Tides produce salinity gradients that result in zones with different plant species. Marshes provide food and protection for fish, crabs, birds, and mammals. A lot of recruitment in this area Chapter 3-‐ These notes include class notes, extra notes from the book, and extra things the professor stated in class. Mangrove forests dominate some tropical coastal zones. Mangroves are salt-‐tolerant, evergreen trees and shrubs from 16 different plant families. The roots trap sediments, which build up and modify the shoreline. Mangrove forests provide nutrients to other marine ecosystems and habitat for many animals. Several unique animals associated with mangroves include manatees, crab-‐eating monkeys, fishing cats, and monitor lizards. Salt tolerant Rocky intertidal zones provide a stable substrate for many organisms. Sessile organisms must cope with wet and dry conditions and changing salinity as the tides rise and fall. Mobile organisms can move into pools at low tide to avoid desiccation. Sandy shores are not very stable(not as good of a place to live because most plants would not be able to root), have little available food, and lots of wave action. But many invertebrates, such as clams, sea worms, and mole crabs, burrow into the sand. Smaller organisms, such as polychaete worms, hydroids, and copepods live on or among the grains of sand. In shallow ocean zones, light penetrates to the bottom and supports sessile photosynthetic organisms. These organisms support a diverse community of other organisms by providing both energy and physical support. Coral reefs (in the photic zone) are restricted to warm, shallow water. Corals are related to jellyfish, form large colonies, and have associated algal partners (symbiotic mutualism). Coral bleaching is when the coral dies “tropical forest of the ocean” Seagrass beds are submerged communities of flowering plants in subtidal marine sediments. Large recruitment in this area because most are safe from predators Algae and animals grow on the plants, and larval stages of many organisms use them for habitat. Kelp beds, or “forests,” support a diverse marine community, including sea urchins, lobsters, mussels, abalones, many other seaweeds, and sea otters. Kelp are large brown algae, with leaf-‐like fronds, stems, and holdfasts which anchor them to the bottom. Pelagic zone: Open ocean beyond the continental shelves. The photic zone, which supports the highest densities of organisms, extends to about 200 m in depth. Below the photic zone, energy is supplied by falling detritus. In the pelagic zone: • Nekton (swimming organisms capable of overcoming ocean currents)—fish, mammals, sea turtles, squid, octopus • Phytoplankton—green algae, diatoms, dinoflagellates, cyanobacteria • Zooplankton—protists, crustaceans, jellyfishes Chapter 3-‐ These notes include class notes, extra notes from the book, and extra things the professor stated in class.
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