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UNIT 2: ECOLOGY ECOSYSTEMS AND COMMUNITIES THE ROLE OF THE CLIMATE What is Climate? - Weather = the day-to-day condition of Earth’s atmosphere at a particular time and place. - Climate = the average, year-after-year conditions of temperature and precipitation in a particular region. - Many factors affect the climate: atmosphere trapping heat, latitude, winds currents, water currents, amount of precipitation, etc. - The energy of incoming sunlight drives Earth’s weather and climate - Certain atmospheric gases also effect temperature The Greenhouse Effect - The atmosphere aids in maintaining temperatures to sustain life. - Carbon dioxide, methane, water vapor, and a few other atmospheric gases trap heat energy and maintain Earth’s temperature range. - Just like the glass windows in a greenhouse, these gases trap the heat energy of sunlight inside Earth’s atmosphere. - Greenhouse Effect = the natural situation in which het is retained by this layer of greenhouse gases. - The incoming sunlight has shorter wavelengths and is able to pass through the greenhouse gases. - The Earth absorbs this energy and reradiates it back toward space as heat (longer wavelengths of energy). - Greenhouse gases “trap” the outgoing energy/heat and keep the Earth warm. - If these gases weren’t present in the atmosphere, Earth would be 30 Celsius degrees cooler than it is today. The Effect of Latitude on Climate - Earth’s 23.5 degree tilt on its axis causes different parts of Earth to receive different angles of solar radiation. - This results in a difference in heat distribution with latitude. - As a result of differences in latitude and thus the angle of heating, Earth has three main climate zones: polar, temperate, and tropical. - Polar Zones = cold areas where the sun’s rays strike Earth at a very low angle. o Between 66.5o and 90o North and South latitudes - Temperate Zones = sit between the polar and tropical zones. o Affected more by the changing angle of the sun over the course of a year (hot or cold). o More “Seasonal” - Tropical Zones (Tropics) = near the equator, between 23.5o North and 23.5o South of the Equator. o Receive direct or nearly direct sunlight year-round, making the climate almost always warm. Heat Transport in the Biosphere - The unequal heating of Earth’s surface drives winds and ocean currents, which transport heat throughout the biosphere. - Warm air at the equator rises and cool air at the poles sinks. - This creates air currents, or winds, that move heat throughout the atmosphere from regions of sinking air to regions of rising air. - “Prevailing Winds” - Ocean currents work in a similar pattern (Poles Sink and Equator Rise) - “Upwelling” - Prevailing winds also effect ocean currents - Ocean currents also transport heat within the biosphere - Landmasses can interfere with the movement of air and water currents (Mountains Rain shadow Desert) WHAT SHAPES AN ECOSYSTEM? Biotic and Abiotic Factors - Biotic Factors = the biological influences on organisms within an ecosystem - Abiotic Factors = physical, or nonliving factors that shape ecosystems (temperature, precipitation, wind, soil, etc.) - Together, biotic and abiotic factors determine the survival and growth of an organisms and the productivity of the ecosystem in which the organism lives. - Habitat = the area where an organism lives (both biotic and abiotic factors) The Niche - Niche = the full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions. - If an organism’s habitat is its address, its niche is its occupation - The combination of biotic and abiotic factors in an ecosystem often determines the number of different niches in that ecosystem. - A niche includes: the type of food the organism eats, how it obtains this food, which other species use the organism as food, the physical conditions the organism requires to survive, and when/how it reproduces - No two species can share the same niche in the same habitat. - Different species can occupy niches that are very similar. Community Interactions - Community interactions can powerfully affect an ecosystem - Competition: o Occurs when organisms of the same or different species attempt to use an ecological resource in the same place at the same time. o Resource = any necessity of life (water, nutrients, light, food, space, etc.) o Direct competition in nature often results in a winner and a loser (fails to survive). o Competitive Exclusion Principle = no two species can occupy the same niche in the same habitat at the same time. o CEP is a fundamental rule in ecology - Predation: o Predation = an interaction in which one organism captures and feeds on another organism o Predator and Prey - Symbiosis: o Symbiosis = any relationship in which two species live closely together (“living together”). 1. Mutualism = both species benefit from the relationship (flowers and pollinating insects). 2. Commensalism = one member benefits and the other is neither helped nor harmed (barnacles and whales) 3. Parasitism = one organism lives on or inside another organism (the host) and harms it (tapeworms in a dog) Ecological Succession - Ecosystems and communities are always changing (abruptly or gradually) in response to natural or human disturbances. - As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community. - Ecological Succession = this series of predictable changes that occurs in a community over time. o Primary Succession = succession (on land) that occurs on surfaces where no soil exists (volcanic eruptions, glaciers, etc.) Pioneer Species = the first species to populate the area when primary succession begins Lichen = a symbiotic relationship between a fungus and an algae (protist) o Secondary Succession = succession that occurs when a disturbance of some kind changes an existing community without removing the soil. Wildfires Proceeds in certain stages and ends with a mature community (“Climax Community”) than can continue to change. o Succession in a Marine Ecosystem Succession can even occur at the bottom of the oceans Whale carcass BIOMES - - Ecologists group Earth’s diverse environments into biomes. Biome = a complex of terrestrial communities that covers a large area and is characterized by certain soil and climate conditions and particular assemblages of plants and animals. Species vary in their adaptations to different conditions. Adaptation = an inherited characteristic that increases an organism’s ability to survive and reproduce. Adaptation lead to variation Tolerance = the ability to survive and reproduce under conditions that differ from optimal conditions Biomes and Climate - Because each species is adapted to certain conditions, the climate of a region is an important factor in determining which organisms can survive there. - Even within a biome, precise conditions of temperature and precipitation can vary over small distances. - Microclimate = the climate in a small area that differs from the climate around it. The Major Biomes - Ecologists recognize at least ten different biomes. - World’s Major Biomes: o Tropical Rain Forest o Tropical Dry Forest o Tropical Savanna o Desert o Temperate Grassland o Temperate Woodland and Shrubland o Temperate Forest o Northwestern Coniferous Forest o Boreal Forest o Tundra - Each of these biomes is defined by a unique set of abiotic factors – particularly climate- and a characteristic assemblage of plants and animals. - There is often ecological variation within a biome (microclimate, rock outcroppings, etc.) - Transitional areas occur between biomes Other Land Areas - Some areas of land on Earth do not fall neatly into the major biome categories. - Mountain Ranges: o Found on all continents o Abiotic and biotic conditions vary with elevation - Polar Ice Caps o The icy polar-regions that border the tundra are cold year-round. o Plants and algae are few, but do include mosses and lichens o North polar region (thinner ice): polar bears, seals, insects, and mites are the dominant animals o South polar region (thicker ice): penguins and marine mammals AQUATIC ECOSYSTEMS - Nearly ¾ of Earth’s surface is covered with water Oceans, streams/rivers, lakes, and marshes Contain a wide variety of communities These communities are governed by biotic and abiotic factors, including light, nutrient availability, and oxygen Aquatic ecosystems are determined primarily by the depth, flow, temperature, and chemistry of the overlying water. In contrast to land biomes, which are grouped geographically, aquatic ecosystems are often grouped according to the abiotic factors that affect them. Depth of water determines the amount of light that organisms receive. Water chemistry refers primarily to the amount of dissolved chemicals – especially salts, nutrients, and oxygen – on which life depends Latitude also plays a factor in aquatic ecosystems Freshwater Ecosystems - Only 3% of the surface of Earth is fresh water. - Freshwater ecosystems can be divided into two main types: flowing-water ecosystems and standing-water ecosystems. - Flowing-Water Ecosystems: o Rivers, streams, creeks, and brooks o Organisms are well adapted to the rate of flow o Typically originate in mountains or hills, often springing from an underground water source o Near the source, the turbulent water has plenty of dissolved oxygen but little plant life o As the water flows downhill, sediments build up and enable plants to establish themselves. o Farther downstream, the water may meander more slowly through flat areas, where turtles, beavers, and river otters make their homes. - Standing-Water Ecosystems: o Lakes and ponds o In addition to the net flow of water in and out of these systems, there is usually water circulating (turning-over) within them. o This circulation helps to distribute heat, oxygen, and nutrients o Plankton = a general term for the tiny, free-floating or weakly swimming organisms that live in both freshwater and saltwater environments. o Phytoplankton = single-celled algae supported by nutrients in the water Form the base of many aquatic food webs o Zooplankton = planktonic animals that feed on the phytoplankton - Freshwater Wetlands: o Wetland = an ecosystem in which water either covers the soil or is present at or near the surface of the soil for at least part of the year. o The water may be flowing or standing and fresh, salty, or brackish (a mixture of fresh and salt water). o Many wetlands are very productive and serve as a breeding ground for many animals (insects, birds, etc.) o 3 main types of freshwater wetlands: Bogs = often dominated by sphagnum moss, typically form in depressions where water collects. Water can be very acidic. Marshes = shallow wetlands along a river. May be underwater for all or part of the year. Swamps = water flows slowly through. Resemble flooded forest. The presence of trees and shrubs is what distinguishes a swamp from a marsh. Estuaries - Estuaries = are wetlands formed where rivers meet the sea - Contain a mixture of fresh water and salt water (brackish) - Affected by the rise and fall of ocean tides - Many are shallow, so sufficient sunlight reaches the bottom to power photosynthesis. - Primary producers include plants, algae, and both photosynthetic and chemosynthetic bacteria. - Most primary production is not consumed by herbivores. - Instead, much of that organic material enters the food web as detritus. - Detritus = is made up of tiny pieces of organic material that provide food for organisms at the base of the estuary’s food web - Organisms that feed on detritus include clams, worms, and sponges. - Estuaries support an astonishing amount of biomass, although they usually contain fewer species than freshwater or marine ecosystems. Serve as spawning and nursery grounds for commercially important fishes and for shellfish such as shrimp and crabs. - - Many young animals feed and grow in estuaries, then head out to sea to mature, and return to reproduce. Many waterfowl use estuaries for nesting, feeding, and resting during migrations. Salt Marshes: o Important temperate-zone estuaries dominated by salt-tolerant grasses above the low-tide line, and by seagrasses under water. Mangrove Swamps: o Coastal wetlands that are widespread across tropical region, including southern Florida (Everglades). o Mangroves are a salt-tolerant tree that dominate these ecosystems Marine Ecosystems - Sunlight penetrates only a relatively short distance through the surface of the water. - Photic Zone = the upper layer of marine ecosystems where photosynthesis can take place (down to a depth of about 200 meters where algae and other producers grow). - Aphotic Zone = below the photic zone and is permanently dark. o Chemosynthetic autotrophs are the only producers - In a addition to the division between the photic and aphotic zones, marine biologists divide the ocean into zones based on the depth and distance from shore: o The Intertidal Zone o The Coastal Zone o The Open Ocean o Benthic Zone (not exclusive to any of these marine zones) - Intertidal Zone: o Organisms in this zone are exposed to regular and extreme changes in their environment (tides) o Rocky Intertidal Zone = exists in temperate regions where exposed rocks line the shore. o Zonation = the prominent horizontal banding of organisms that live in a particular habitat o Competition leads to zonation - Coastal Ocean: o Extends from the low-tide mark to the outer edge of the continental shelf (the relatively shallow border that surrounds the continents). o Often shallow enough to fall mostly or entirely within the photic zone, so photosynthesis can usually occur throughout its depth. o Often rich in plankton and many other organisms o Kelp Forest = named for their dominant species: a giant brown algae (protist) that can grow at extraordinary rates (as much as 50cm a day) o Very productive communities that support a complex food web - Coral Reefs: o Exists in warm, shallow water of tropical coastal oceans o Among the most diverse and productive environments on Earth o Named for the coral animals whose hard, calcium carbonate skeletons make up their primary structure (Coral) o Coral animals are tiny relatives of jellyfish that live together in vast numbers. o Most are the size of your fingernail or smaller o Use tentacles to capture and eat microscopic creatures that float by. o Coral animals cannot grow in cold waters or water that is low in salt. o The types of coral that build “reefs” grow with the help of algae that live symbiotically within their tissues. o These algae carry out photosynthesis using the coral animals’ wastes as nutrients. o In turn, the algae provide the coral hosts with certain essential carbon compounds. o Because the algae require strong sunlight, most reef-building corals thrive only in brightly lit areas within 40 meters of the surface - Open Oceans: o “Oceanic Zone” o Begins a the edge of the continental shelf and extends outward o The largest marine zone, covering more than 90% of the surface of the world’s oceans. o Range from 500 meters deep along the continental slopes to more than 11,000 meters at the deepest ocean trench. o Organisms are exposed to high pressure, frigid temperatures, and total darkness. o Typically has very low levels of nutrients and supports only the smallest producers. o Productivity is generally low. o Still, because of the enormous area, most of the photosynthetic activity on Earth occurs in the part of the open ocean within the photic zone o Fishes dominate the open ocean o Marine mammals (dolphins and whales) must stay close to the surface to breathe. - Benthic Zone: o The “Ocean Floor” o Contains organisms that live attached to or near the bottom, such as sea stars, anemones, and marine worms. o Benthos = the organisms that live in the benthic zone o This zone extends horizontally along the ocean floor from the coastal ocean through the open ocean. o Benthic ecosystems often depend on food from organisms that grow in the photic zone, particularly the producers o Feed on pieces of dead organic material, or detritus, that drift down from the surface waters. o Near deep-sea vents, where superheated water boils out of cracks on the ocean floor, dwell chemosynthetic primary producers that support life without light or photosynthesis.