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Chapter 3: Communities and Biomes Community • interacting population in an area at one time Limiting Factors • factors that affect an organism’s ability to survive in its environment – Availability of water and food – predators – temperature • Any biotic or abiotic factor that restricts the existence, numbers, reproduction, or distribution of organisms Example – Plant life • Limiting factors – low temperature – strong winds - soil can’t support growth - fire - pollution - Factors that limit one population may also have an effect on other populations Ranges of Tolerance • the ability of organisms to withstand fluctuations in biotic and abiotic environmental factors Succession: Changes over time • ecologists can predict changes over time • Ex. Grass was allowed to grow without cutting 1. Grass gets taller, weeds start to grow. Resembles a meadow 2. Later – bushes grow, trees appear, and different animals enter area to live 3. Then – bushes and trees change the environment, less light reaches the ground. The grass slowly disappears 4. Thirty years later – the area is a forest Succession • orderly natural changes and species replacement that takes place in communities of an ecosystem – occurs in stages – at each stage different species of animals and plants may be present – as succession progresses – new organisms move in and others may die or move out – can take decades or centuries Two types of Succession 1. Primary 2. Secondary Primary Succession • colonization of barren land by communities of organisms • Takes place on land where there are no living organisms • Ex. Lava from a volcano destroys everything in its path – Forms barren land • First species to take hold- pioneer species – Lichen – first species to move in – Eventually die and settle into cracks – Promotes the first stage of soil development • New Soil – enables small weed plants to move in – – – – Plants Ferns Insects fungi • Primary Succession slows down and the community becomes fairly stable or reaches equilibrium = CLIMAX COMMUNITY Secondary Succession • the sequence of changes that takes place after an existing community of organisms inhabiting an area is severely disrupted in some way • fire destroys a community • field is not replanted • Occurs in areas that previously contained life • land still contains soil • soil already exists so takes less time than primary succession Secondary Succession 1. 1988 - Fire destroys Yellowstone Park 2. annual wildflowers first to grow back 3. 3 years later – perennial wildflowers, grasses, ferns, and thousands of pine seedlings are growing – Once the trees grow past the shade of the grasses and perennials, they will grow more quickly Biome • a large group of ecosystems that share the same type of climax community • Biomes on land – terrestrial biomes • Biomes in water – aquatic biomes Aquatic Biomes • water – covers 75% of earths surface • most of water is salty • oceans, seas, and some inground lakes – salt water • Freshwater – rivers, streams, ponds, and most lakes Marine Biomes – salt water biomes • Oceans: – Abiotic Factors – salinity, depth, availability of light, temperature – Biotic Factors – plants and animals – Large amounts of Biomass – living material • Study different zones 1. shallow, sunlit zones – photic zones 2. deeper, unlit zones – aphotic zones Photic Zones • shallow enough for sunlight to penetrate • along coastlines of most landmasses on earth • bays, rocky shores, sandy beaches, mudflats, and estuaries • coral reefs Aphotic Zone • deepest, least explored areas of the ocean Estuaries • fresh water mixes with salt water – Ex. Where a river joins an ocean • Estuary – coastal body of water, partially surrounded by land, in which fresh and salt water mix • Salinity – amount of salt – Ranges between that of salt water and that of freshwater – Also changes with tide – How much freshwater is brought in from the river – Can support a wide range of organisms Tides • gravitational pull of sun and moon causes a rise and fall of the ocean • Intertidal Zone – portion of the shoreline that lies between the high and low tides – Size depends on slope of land and difference between high and low tide – high levels of sunlight, nutrients, and oxygen Tide Pools • pools of water left when the tide is low • can isolate org. until the next high tide • Animals – – snails, sea stars, and barnacles have adaptations to keep them anchored in the intertidal zone – clams, worms, snails, crabs, and others burrow in sand Marine Biome - Light • shallow water region, that is less affected by waves • Nutrient runoff from the land contributes to abundant life Plankton • most of the organisms that live in the marine biome • small organisms that drift and float in the waters • autotrophs, diatoms, eggs, & juvenile stages of marine animals • base of all aquatic food chains • consumed by small and large animals • baleen whales and sharks feed on plankton Marine Biome – Dark • darkness blacker than night • extreme pressure Freshwater Biomes • shallow water on the shoreline • tadpoles, insects, turtles, worms and crayfish • water a few feet below surface remains cold • Temperature – abiotic factor that limits the kind of organisms that can survive • Light – abiotic factor that limits photosynthesis • Bacteria- at bottom break down dead organisms Other Aquatic Biomes • Wetlands- where land and water meet • swamps – have trees • marshes – no trees, but have water flowing through them – Both – highly productive – Source of food for many migrating birds and other animals • bogs – water from rain only Terrestrial Biomes • Latitude and Climate – • Latitude - describes your position in degrees north and south of the equator • At different latitudes the sun strikes the earth differently • Climate is different – – – – – – Wind Cloud cover Temperature Humidity Precipitation • Latitude and Climate – abiotic factors • affect plants & animals • small differences create different biomes Tundra • first area that circles the • • • • North Pole treeless areas with long summer days and short periods of winter sunlight temperatures never rise above freezing for long only uppermost layer of soil thaws in the summertime soil underneath top layer – permafrost- that is permanently frozen ground Top layer • thin – can only support shallow rooted grasses and other small plants • soil – lack nutrients • decay – slow – due to low temperatures • nutrients are not recycled quickly • limits types of organisms • Growing Season is Short – limits the types of plants – grasses and dwarf shrubs – resistant to drought and cold • Insects – mosquitoes and black flies • Animals – small mammals – – – – – rat like lemmings weasels artic foxes snowshoe hares birds – snowy owls and hawks • Why is the tundra treeless? Taiga • just south of the tundra • circles the north pole • Taiga – called the boreal or northern coniferous forest • Continuous belt of coniferous trees worldwide • Common trees – – – – – Larch Fir Hemlock Spruce • Soil- waterlogged • warmer and wetter than the tundra • still has harsh, long, severe winters • Stretches across- Canada, Northern Europe, and Asia • Top Soil – acidic and poor in minerals b/c of decaying coniferous needles • Trees – provide food and shelter for more animals • Animals – lynx, snowshoe hare, Caribou, weasels, red squirrels, wolves, elk, red deer, moose, and variety of migratory birds Desert • arid region with sparse to almost nonexistent plant life • driest biome • less than 25 cm of rain a year • Vegetation varies • More rain, more vegetation • Shrub communities • Less rain – scattered plant life Desert Plants • annual plants that can germinate from seed and grow to maturity quickly after sporadic rainfall • adaptations to conserve water • Cacti – waxy leaves, photosynthetic stems • Spines, thorns, or poisons • Leaves curl up or drop off altogether Desert Animals • emerge at night • Herbivores - Obtain water from the food they eat. Ex. kangaroo rat • coyotes, hawks, owls, and roadrunners – carnivores that eat lizards, snakes, small animals • scorpions – venom to capture prey Grassland • large communities covered with rich soil, grasses, and similar plants • receive approx. 25-75 cm of rain • experience a dry season • few trees • grasses die off in winter and put nutrients into soil • ideal for growing cereal grains: oats, rye, and wheat • breadbaskets of the world- each grain is a species of grass Grassland Animals grazing animals – bison • prairie animals – jack rabbits, deer, elk, and prairie dogs • insects, birds, and reptiles • Prairie = grassland = savanna = steppes = pampas Temperate Forest • precipitation ranges from 70-100 cm/year • Temperate or deciduous forests • Dominated by broad-leaved trees hardwood trees that loose their foliage annually – – – – – Maple Oak Birch Elm Ash Temperate Forest • Soil – rich top layer and some clay • Animals – squirrels, mice, deer, rabbits, bears, and many birds Rain Forests • home to more organisms than any other biome 2 types 1. Temperate rain forest 2. Tropical rain forest • extensive rainfall Tropical Rain Forest • • • • warm temperature (25ºC) wet weather (200-600 cm rain/year) lush plant growth near the equator Hypothesis as to why tropical rain forests contain so many species 1. Due to their location near the equator, they were not covered during the last ice age. Species had more time to evolve and biodiversity exists 2. Warm weather permits year round growing conditions which permits a greater food supply 3. they provide a multitude of habitats and niches for diverse organisms Rainforest • Vertical Layering – – creates a large number of niches – canopy, understory, ground layers • Few nutrients in soil – all in living things • Hot, humid environment – ants, termites, fungi, bacteria, and other decomposers to break down dead material quickly • Most species rich places on earth Biomass • total weight of organisms living in the area is high • important sources of medicinal products and hardwood trees • Not suitable farmland – little organic material in the soil – w/out org material – soil becomes exposed – soil will eventually become hard, almost brick-like