Presentation on theme: "Communities and biomes"— Presentation transcript:
1Communities and biomes Biology 2B - EcologyCommunities and biomes
2EcosystemsEcosystem is a term that describes ecological systems consisting of interacting organisms and their physical environmentAbiotic factorNon living factors eg temperature, rainfallBiotic factorLiving factors eg predation, competitionCommunityAll the organisms in an ecosystemEnvironmentAll the abiotic factorsHabitatParticular area in which a population livesPopulationAll the organisms from one species in an ecosystem
3Aquatic habitatsAquatic habitats come in many forms: lakes, rivers, wetlands, marshes, lagoons, streams, rivers, and swamps. Where freshwater mixes with saltwater you'll find mangroves, salt marshes, and mud flats.Seas and oceans stretch from pole to pole and reach around the globe. They cover more than 70 percent of the Earth's surface and hold in excess of 300 million cubic miles of water. Scattered throughout these vast waters are islands.Coral reefs are made up of millions of tiny coral polyps -- animals that together form vast colonies and secrete the limestone deposits. Reefs form in shallow, warm-water seas around the world. There are several types of reef including barrier reefs, fringe reefs, and atolls.Beaches and coasts lie at the threshold between land and sea where wildlife adapts to a constantly changing coastline and sways to the rhythms of the tides.
4Terrestrial habitatsDeserts and scrublands are landscapes that have scarce precipitation.Scrublands are semi-arid habitats that are dominated by scrub vegetation such as grasses, shrubs, and herbs.Forests and woodlands are habitats dominated by trees. There are many different types of forests—temperate, tropical, cloud, coniferous, boreal.Tundra is a cold habitat characterized by low temperatures, short vegetation, long winters, brief growing seasons, and limited drainage. Arctic tundra is located near the North Pole and extends southward to the point where coniferous forests grow. Alpine tundra is located on mountains around the world at elevations that are above the tree line.Alpine, or montane, habitats occur in highlands and mountain ranges around the world.
5Structural classification of communities Type and height of tallest layerPercentage foliage cover of tallest layerVery dense ( %)Dense ( %)Medium ( %)Sparse (30 -10%)Very sparse ( 10%)Trees 10 – 30 mTrees 10m = lowTrees 30m = tallClosed forestLowTallForestOpen forestWoodlandOpen woodland-Shrubs 2mShrubs mClosed scrubClosed heathlandScrubHeathlandOpen scrubOpen heathlandTall shrublandShrublandTall open shrublandOpen shrublandHummock grassesHummock grasslandOpen hummock grasslandHerbaceous layerMainly grassesMainly sedgesMainly herbsMainly fernsClosed grasslandClosed sedgelandClosed herblandClosed fernlandGrasslandSedgelandHerblandFernlandOpen grasslandOpen sedgelandOpen herblandVery open grasslandVery open sedgelandVery open herbland
6BiomesCommunities with similar abiotic factors have similar characteristics, although they contain different species of plants and animals.
8Changes in communities Ecosystems change:Abiotic factors may vary –eg light, water, temperature, salinity, tidesThese may vary cyclically eg day/night; monthly, seasonally, over longer periods, or catastrophically (eg fire, flood, volcanic eruption, ice age, etc)Biotic factors may vary –Numbers ofProducersPrey species (1st order consumers)Predators (high order consumers)
9Everything in an ecosystem is linked A change in one factor can lead to changes in other factors – this is called the domino effecteg decreased rainfall decrease in vegetation decrease in herbivores (prey species) decrease in predatorseg removal of predators (hunting or biomagnification) increase prey species (plague) decrease vegetation decrease in herbivores due to no foodKey species a species whose removal negatively affects an entire ecosystem eg otters in kelp forests – when hunted to extinction, sea urchin numbers increased so much that they destroyed the kelp decrease in the other species depending on kelp for food or shelter
10Changes in ecosystems – human interference Human presence disrupts ecosystems in many ways including:Loss of predators removal of predators (sg spiders, wolves) can lead to population explosions of prey speciesIntroduction of new carnivore eg foxes, cats, dogs loss of native wildlifeIntroduction of new herbivore eg rabbit, sheep, may out-compete natives loss of native species; may cause over grazing as no native predators erosionIntroduction of new producer eg brambles, prickly pear, may out compete natives (as often not edible to consumers) loss of native plant and animal species (now not enough food for them); aquatic plants eg duckweed may block rivers
11Changes in ecosystems - water Damschanges distribution of populations in ecosystems – can get animals accumulating around dams over grazing near the water source; loss of original ecosystem in flooded areaPresence of bores lowers water table; increases number of animals around bore over grazing near the water sourceTailing dams kills wildlife that tries to use it as waterRemoving water for human use lowers amount of water in river/streams eg Murray not enough water to maintain ecosystemFilling in wetlands destroys ecosystem; loss of habitat for migrating birds; damage to neighbouring ecosystems as wetlands act as filters to remove pollutants and excess nutrients
12Changes in ecosystems - clearing Loss of trees loss of habitat & nesting places as well as the followingLoss of topsoil (= erosion) loss of fertility decreased producers decreased biomass in the whole ecosystemRise of water table water logging in low lying areas, increased soil salinity as salts are brought up with the waterIncreased soil salinity loss of fertility decreased producers decreased biomass in the whole ecosystemIncreased water salinity loss of fertility decreased producers decreased biomass in the whole ecosystem; poisoning of consumers, loss of aquatic life
13Changes in ecosystems -agriculture Farming agricultural practices includeMonoculture presence of only one species in the crop, decreases biodiversity, encourages population explosions or plagues of pest species eg mice, locusts, in the long term reduces soil fertilityKilling insects (eg pesticides) disrupts ecosystems by destroying food source of higher order species (eg owls, wattle birds); can lead to ecological magnificationLoss of dead/decaying matter loss of fertility, loss of decomposers soil problems reduction in producers reduction in consumersFertiliser use chemical poisoning of plants or animals (eg high phosphate fertilisers kill many native trees; run-off into rivers can cause eutrophication (algal blooms)
14Changes in ecosystems – climate change Climate change changes in temperature, rainfall & humidity – also affects water availabilityIncreased temperature increased water loss higher water needs; may cause death of organisms if temperature too high; rising sea levels (thermal expansion of water) and melting of glaciers and polar icecaps may also impact on ecosystemsDecreased rainfall reduced water availability decreased biomass (less plants less animals)Reduced water table dries out seasonal water sources (eg swamps, small creeks) and cave systems, less water decreased biomass (less plants less animals)Change in seasons organisms may not be able to find enough food to survive & raise offspring eg birds breed as light levels change, insects breed as temperature rises