BSCI 124 – UNIT 4 Review SheetEcologyPopulationsAll the members of a single species living togetherHabitatsThe location where the population is found (the “address” of an organism)NicheThe functional role an organism plays in the ecosystem – it encompasses habitat plus relationships with other organisms in the ecosystemCommunity – dominant speciesPlant Community – different populations of plants living together in the same geographical areaDominant species – the most influential species in the community. For ex: Redwood forest. They control the structure and species composition of the community throughPhysical factorsLight (provide shade), Wind (wind screen), Humidity (higher than in open areas)Chemical factorsNutrients, pHBiotic vs. abiotic factorsBiotic there are many organisms that live in a community. Organisms interact in food chainsAbiotic – non-living components of the environment: climate, light, soil, inorganic substances. Biogeochemical cycles.Ecosystem Functional unit of study in environment. A Community with all its abiotic and biotic organismsFood Chains – Trophic levelsProducers (photosynthesis)  1st order (herbivores)  2nd order (carnivoresEach step is a trophic level. 85-90% energy lost at each levelBacteria and fungi are decomposers of dead materialFood websMore realistic than food chain. Multiple interaction between several food chains. Usually more than one producer and primary consumer. Consumers have alternative food sources.Biogeochemical cyclesCarbon cycle – what disrupts itCO2 enters plants through photosynthesis. Carbon is released back to the air through respiration, or combustion of fuels. Fossil fuels (oil, coal, gas) were formed from remains of ancient organismsGreenhouse EffectHumans upset the balance of the Carbon Cycle:1. Global deforestation2. More CO2 released due to burning fuelsResult: a 25% increase in global CO2Carbon dioxide acts as a heat trap, capturing sunlightConsequence: global warming; Earth’s temperature has increased 1o F, more expectedWater cycle – rain, seas, riversWater enters the atmosphere as vapor from the land and transpiration from plants. Vapor condenses  rainfall, into rivers, streams, oceansPlant TranspirationTranspiration of large plant populations (like trees in a tropical rainforest) can actually alter the rainfall patterns in an area!Trees can “create” rainfall through transpirationNitrogen cycle – role of legumesNitrogen Cycle – Nitrogen gas is fixed by bacteria in plant root nodules. Plants assimilate N and incorporate it into organic nitrogen compounds. Animals assimilate N by ingesting plants. Animal waste and organic nitrogen compounds are broken down.Phosphorous cycle – (not much)Phosphorous is absorbed by plants and goes back into the earth by animal waste from living organismsPhosphorous is used a lot in fertilizers, which run off a lot onto waterways. This kicks the system out of balance, and upsets the balance of phosphorous in ecosystemsPrimary vs. secondary successionPlant Succession – predictable changes over time in the kinds of plants growing in an areaPrimary SuccessionEcosystem are not static, they change over timeWhen plants become established on land completely devoid of soil and vegetationEX – new volcanic islandsSoil – portion of Earth’s surface of disintegrated rock and organic materials (humus)Pioneer species: first inhabitants, forms soil. Each stage prepares the way for the next invasion of speciesSecondary SuccessionSecondary succession - natural forces or human intervention destroy the existing vegetation (fire, flooding, logging, agriculture)When the disturbance stops, community begins secondary succession à back to climax communitySince soil is already in place, secondary succession can take place 5-10 times faster than primary successionAn example of secondary succession on barren rock or lava is Mount St. Helens in Washington State (1980 eruption)Mt. St. Helens recovery after the eruptionAlso, plant community affects these abiotic factorsFor example, in the tropical rain forests, the vegetation “creates” the rainfall through plant transpiration.When trees are removed, rainfall stops and land becomes aridThe resulting new climax community is often desert shrubsSecondary succession example – an abandoned corn fieldClimax communityRelatively stable community at the end of succession1. in equilibrium with the environment2. permanent (until some major change)3. varies depending on conditionsHumans usually knock out climax conditionSoil characteristicsParent material – soil particles of naturally occurring inorganic materialSoil texture – all soils contain 3 kinds of particles:SandSiltClay - most important: it holds nutrients for plantsOrganic matter – humus is decomposing organic matter in the soilSoil pH – acid (low pH) or basic (high pH) soil influences soil fertility and nutrient availabilityBest soil is neutral or slightly acidic pHBIOMESClimate characteristicsDetermined by the tilt of the Earth (23.5)Temperature – how hot or cold it can get, and the length of the growing seasonPrecipitation (rain, snow) – annual precipitation and seasonal distributionInfluenced by physiographic features, like mountains, rivers, oceansWind (differences in atmospheric heating create winds)Humidity, light, fire, soil typeElevation/altitudeIn N. America, weather patterns move from west to eastElevation – altitude influences biomes. Cooler temperatures high in the mountains favor biomes similar to biomes near North PoleBiomes:Tundra – “land without trees”Geographical location – northernmost land biome: around arctic circleClimate – very cold and dry (little precipitation)Temp – Freezing temperatures can occur any day of the year (rarely over 15 deg. Celsius)Soil type: Wet, shallow, or with permanently frozen soil called permafrost. Only top 0.5m thawsPlantsMost are perennials (20-100 years) and shortNo treesLow shrubs and herbs, grass-like plantsShort growing season, plants bloom in summer, plants adapted to cold temperature (antifreeze sap), hairy leaves that help retain heatLichens, mossesAnimalsMigratory birds, wolves, fox, polar bear, rain deer, voles, black fliesLow biodiversity and productivityHuman impactSensitive to human disruption – takes a long time to recover (slow growth)Arctic national wildlife refugeBoreal Forest – Taiga (17% of Earth’s land surface area)Geographical location – Area near arctic