Unit 1 - Introduction to Ecosystems

Unit 1 Introduction to Ecosystem

    1. Ecosystems
  • Ecosystem: all living and nonliving things in an area
  • Biome: large area with similar climate conditions that determine plant and animal species there
  • Organism interactions –
    • Competition: organisms fighting over a resource like food or shelter; limits population size
    • Predation: one organism using another for energy source (hunters, parasites, even herbivores)
    • Mutualism: relationship that benefits both organism
    • Commensalism: relationship that benefits one organism and doesn’t impact the other
  • Predation
    • Herbivores: (plant eaters) eat plants for energy
    • True predators: (carnivores) kill and eat prey for energy.
    • Parasites: use a host organism for energy, often without killing the host and often living inside host
    • Parasitoids: lay eggs inside a host organism; eggs hatch and larvae eat host for energy
  • Symbiosis (sym = together | bio = living | osis = condition)
    • Any close and long-term interaction between two organisms of different species
      • Mutualism, commensalism, and parasitism are all symbiotic relationships.
  • Competition: reduces population size since there are fewer resources available and fewer organisms can survive
    • Resource partitioning: different species using the same resources in different ways.
    • Temporal partitioning: using resources at different times, such as wolves and coyotes hunting at different times.
    • Spatial partitioning: using different areas of a shared habitat.
    • Morphological partitioning: using different resources based on different evolved body features.
    1. Terrestrial (Land) Biomes
  • Biome: an area that shares a combination of average yearly temperature and precipitation (climate)
  • The community of organisms (plants and animals) in a biome are uniquely adapted to live in that biome.
  • Nutrient availability - plants need soil nutrients to grow, so availability determines which plants can survive in a biome.
  • Shifting biomes - biomes shift in location on earth as climate changes.
    1. Aquatic Biomes
  • Characteristics of Aquatic Biomes
    • Salinity: how much salt there is in a body of water, determines which species can survive and usability for drinking
    • Depth: influences how much sunlight can penetrate and reach plants below the surface for photosynthesis
    • Flow: determines which plants and organism can survive, how much O2 can dissolve in water
    • Temperature: warmer water holds less dissolve O2 so it can support fewer aquatic organisms
  • Freshwater: Rivers and Lakes
    • Rivers have high O2 due to flow mixing water and air also carry nutrient-rich sediments (deltas and flood plains = fertile soil)
    • Lakes = standing bodies of fresh H2O (key drinking H2O source)
      • Littoral: shallow water with emergent plants
      • Limnetic: where light can reach (photosynthesis)
        • No rooted plants, only phytoplankton
      • Profundal: too Deep for sunlight (no photosynthesis)
      • Benthic: murky bottom where inverts (bugs) live, nutrient-rich sediments
  • Freshwater: Wetlands
    • Wetland: are with soil submerged/saturated in water for at least part of the year, but shallow enough for emergent plants
      • Plants living here have to be adapted to living with roots submerged in standing water (cattails, lily pads, reeds)
    • Benefits of wetlands
      • Stores excess water during storms, lessening floods.
      • Recharges groundwater by absorbing rainfall into soil.
      • Roots of wetland plants filter pollutants
      • Highly plant growth due to lots of water and nutrients (dead organic matter) in sediments
  • Estuaries: areas where rivers empty into the ocean
    • Mix of fresh and salt water (species adapt to this)
    • High productivity (plant growth) due to nutrients in sediments deposited in estuaries by river.
    • Salt marsh:
      • Estuary habitat along coast in temperate climates
      • Breeding ground for man fish and shellfish species
    • Mangrove swamps:
      • Estuary habitat along coast of tropical climates
      • Mangrove trees with long, stilt roots stabilize shoreline and provide habitat for many species of fish and shellfish.
  • Coral Reef
    • Warm shallow waters beyond the shoreline; most diverse marine biome on earth
    • Mutualistic relationship between coral (animals) and algae (plant
      • Coral takes CO2 out of ocean to create calcium carbonate exoskeleton (the reef) and provides CO2 to the algae.
      • Algae lives in the reef and provides sugar (energy) to the coral through photosynthesis.
        • Both species rely on the other:
          • Coral couldn’t survive without energy from algae.
          • Algae need the home of the reef of CO2 from the coral.
  • Intertidal Zones
    • Narrow band of coastline between high and low tide
    • Organisms must be adapted to survive crashing waves and direct sunlight/heat during low tide.
    • Shells and tough outer skin can prevent drying out (desiccation) during low tides.
      • Different organisms are adapted to live in different zones.
  • Open Ocean
    • Low productivity/area as only algae and phytoplankton can survive in most of the ocean.
      • So large though, that algae and phytoplankton of ocean produce a lot of earth’s O2 and absorb a lot of atmospheric CO2.
    • Photic zone = area where sunlight can reach (photosynthesis)
    • Aphotic zone (abyssal) = area to deep for sunlight
    1. Carbon Cycle
  • Movement of molecules that contain Carbon (CO2, glucose, CH4) between sources and sinks.
    • Some steps are very quick (FF combustion); some are very slow (sedimentation and burial)
    • Leads to imbalance in which reservoirs or sinks are storing carbon.
  • The atmosphere is a key C reservoir, increasing levels of C in atmosphere. Leads to global warming.
  • Carbon sink: a carbon reservoir that stores more carbon than it releases.
    • Ocean (algae and sediments), plants, soil
  • Carbon source: processes that add C to atmosphere.
    • Fossil fuel (oil, coal, natural gas) combustion
    • Animal (cow burps and farts = CH4)
    • Deforestation, releases CO2 from trees
  • Photosynthesis and Cellular Respiration
    • Both processes are very quick
    • Cycle C between biosphere and atmosphere in balanced amount (no net C increases in atmosphere)
    • Photosynthesis
      • Plants, algae, phytoplankton
      • Removes CO2 from the atmosphere and converts it to glucose.
      • Glucose = biological form of C and stored (chemical) energy in form of sugar
      • CO2 sink
    • Cellular Respiration
      • Done by plants and animals to release stored energy.
      • Uses O2 to break glucose down and releases energy.
      • Releases CO2 into atmosphere
      • CO2 source (adds CO2 to atmosphere)
  • Ocean and Atmosphere
    • Direct axchange: CO2 moves directly between atmoshpere and the ocean by dissolving into and out of ocean water at the surface
      • Happens very quickly and in equal directions, balancing levels of CO2 between atmosphere and ocean
    • Because of direct exchange, increasing atmospheric CO2 also increases ocean CO2, leading to ocean acidification
    • Algae and phytoplankton take CO2 out of the ocean and atmosphere through photosynthesis
      • Coral reef and marine organisms with shells also take CO2 out of the ocean to make calcium carbonate exoskeletons
    • Sedimentation: when marine organisms die, their bodies sink to the ocean floor where they’re broken down into sediments that contain C
      • Burial: over long, periods of time, pressure of water compresses C – containing sediments on the ocean floor into sedimentary stone (limestone, sandstone) - long term C reservoir
  • Burial, Extraction, and Combustion
    • Burial: slow, geological process that stores C in underground sinks like sedimentary rock or fossil fuels
      • Sediments (bits of rock, soil, organic matter) compressed into sedimentary rock or fossil fuels by pressure from overlying rock layers or water.
    • Fossil Fuels (FF): coal, oil, and natural gases are formed from fossilized remains of organic matter.
    • Extraction and Combustion: digging up or mining fossil fuels and burning them as energy source, releases CO2 into the atmosphere
    • Burial (formation of fossil fuels) takes far longer than extraction and combustion, which means they increase concentration of CO2 in the atmosphere
    1. Nitrogen Cycle
  • Movement of Nitrogen containing molecules between sources and sinks/reservoirs
    • Sources releases N into atmosphere; sinks take N out of the atmosphere in increasing amounts.
  • Nitrogen reservoirs hold nitrogen for relatively short periods of time compared to the Carbon cycle.
  • Atmosphere = main Nitrogen reservoir
    • Nitrogen in the atmosphere exists mostly as N2 gas, not usable by plants or animas.
  • Nitrogen = critical plant and animal nutrient
    • All living things need nitrogen for DNA and amino acids to make proteins.
  • Nitrogen fixation
    • Process of N2 gas being converted into biologically available (useable by plants) NH3 (ammonia) or NO3- (nitrate)
    • Bacterial fixation: certain bacteria that live in the soil, or in symbiotic relationships with plant root nodules convert N2 into ammonia (NH3)
    • Synthetic fixation: humans combust fossil fuels to convert N2 gas into nitrate (NO3-)
  • Other Nitrogen Cycle Steps
    • Assimilation: plants and animals taking nitrogen in and incorporating it into their body
    • Ammonification: soil bacteria, microbes and decomposers converting waste and dead biomass back into NH3 and returning it to soil
    • Nitrification: conversion of NH4 into nitrite (NO2) into nitrous oxide (N2O) gas which returns to atmosphere
  • Human impacts on nitrogen cycle
    • Climate: N2O (nitrous oxide) = greenhouse gas which warms earth’s climat4
    • Ammonia volatilization: excess fertilizer use can lead to NH3 gas entering the atmosphere.
    • Leaching and eutrophication: synthetic fertilizer use leads to nitrates (NO3-) leaching, or being carried out of soil by water.
    1. Phosphorus Cycle
  • Phosphorus cycle basics
    • Movement of phosphorus atoms and molecules between sources and sinks/reservoirs
      • Rocks and sediments containing phosphorous minerals = major reservoirs
    • Phosphorus cycle is very slow compared to Carbon, water, nitrogen cycles.
    • Takes a long time for phosphorus minerals to be weathered out of rocks and carried into soil/bodies of water.
    • No gas phase of phosphorus (doesn’t enter atmosphere)
    • Because the cycle is so slow, it is limiting nutrients, meaning plant growth in the ecosystem is often limited by phosphorus availability in soil and water.
    • Phosphorus is needed by all organisms for DNA, ATP (energy), bones and tooth enamel in some animals.
  • Phosphorus sources
    • The major natural source of phosphorus is the weathering of rocks that contain phosphorus materials.
      • Wind and rain break down rock and phosphate are released and dissolved into water’ rainwater carries phosphates into nearby soils and bodies of water
      • Weathering is so slow that phosphorus is often a limiting nutrient in aquatic and terrestrial ecosystems.
    • Synthetic: (human) sources of phosphorus = mining phosphate minerals and adding to products like synthetic fertilizers and detergents/cleaners
      • Synthetic fertilizers containing phosphates are added to lawns or agriculture. Field: runoff carries phosphorus into nearby bodies of water. Phosphates from detergents and cleaners enter bodies of water via wastewater from homes.
  • Assimilation and Excretion/decomposition
      • Phosphorus is absorbed by plant roots and assimilates into tissues; animals assimilate phosphorus by eating plants or other animals.
      • Animal waste, plant matter and other biomass is broken down by bacteria/soil decomposers that return phosphate to soil.
      • Assimilation and excretion/decomposition form a mini loop within Phosphorus cycle just like assimilation and ammonification in nitrogen cycle, photosynthesis and respiration in carbon cycle.
  • Sedimentation and Geography uplift
      • Phosphate doesn’t dissolve very well into water; much of it forms solid bits of phosphate that fall to the bottom as sediment (sedimentation)
      • Phosphorus sediments can be compressed into sediment rock over long time periods by pressure of overlying water.
    • Geological uplift: tectonic plate collision forcing up rock layers that form mountain; phosphorous cycle can start over again with weathering and release of phosphate from rock.
  • Eutrophication (too much nitrogen and phosphorus)
    • Because they’re limiting nutrients in aquatic ecosystems, extra input of nitrogen and phosphorous lead to eutrophication (excess nutrients) which fuels algae growth.
      • Algae bloom covers surface of water, blocking sunlight and killing plants below surface.
      • Algae eventually die-off: bacteria that break down dead algae use up O2 in the water (because decomposition = aerobic process)
      • Lower O2 levels (dissolved oxygen) in water kills aquatic animals, especially fish.
      • Bacteria use up even more O2 to decompose dead aquatic animals.
      • Create positive feedback loop: less O2 🡪 more dead organism 🡪 more bacterial decomposition 🡪 O2.
    1. Hydrologic (water) Cycle
  • Water cycle overview
    • Movement of H2O (in different states) between sources and sinks
    • States of matter (solid/liquid/gas) as well as where water is moving are ley in H2O cycle.
    • Energy from sun drives the H2O cycle.
    • Ocean = largest water reservoir
    • Ice caps and groundwater are smaller reservoirs but contain fresh useable water for humans.
  • Evaporation and Evapotranspiration
    • 2 main sources of water (processes that cycle it from liquid on earth back into the atmosphere)
    • Sometimes called vaporization since liquid water becomes water vapor (gas) in atmosphere.
    • Transpiration: process plants use to draw groundwater from roots up to their leaves
      • Leaf openings called stomata open, allowing water to evaporate into atmosphere form leaf.
      • Movement of H2O out of leaf creates low H2O potential in leaf, pulling H2O up from roots.
    • Evapotranspiration: amount of H2O that enters atmosphere from transpiration and evaporation combined
    • Both processes are driven by energy from the sun
  • Runoff and Infiltration
    • Precipitation (rain) either flows over earth’s surface into a body of water (runoff) or trickles through soil down into groundwater aquifers (infiltration)
    • Groundwater (aquifers) and surface waters (lakes/rivers) are important freshwater reservoirs for humans and animals.
    • Precipitation recharges groundwater through infiltration, but only if ground is permeable (able to let water pass through)
    • Runoff recharges surface waters, but can also carry pollutants into water sources.
    1. Primary Productivity
  • Primary Productivity Basics
    • Primary Productivity: rate that solar energy is converted into organic compounds via photosynthesis over a unit of time.
      • (Rate of photosynthesis of all producers in an area over a given period of time
    • Ecosystems with primary productivity are usually more biodiverse than ecosystems with low primary productivity.
  • Calculating Primary Productivity
    • NPP = GPP – RL
    • Net primary productivity (NPP): the amount of energy (biomass) leftover for consumers after plants have used some for respiration.
      • Think of NPP as the actual amount of the plants paycheck it keeps after taxes.
    • Respiration loss (RL): plants use up some of the energy they generate via photosynthesis by doing cellular respiration (movement, internal transportation, etc.)
    • Gross Primary Productivity (GPP): the total amount of sun energy (light) that plants capture and convert to energy (glucose) through photosynthesis.
  • Ecological Efficiency
    • The portion of incoming solar energy that is captured by plants and converted into biomass (NPP or food available for consumers)
    • Generally, only 1% of all incoming sunlight is captured and converted into GPP via photosynthesis.
    • Of that 1%, only about 40% (or o.4% of total incoming solar energy) is converted into biomass/plant growth (NPP)
    • Some ecosystems are more efficient (higher NPP) than others.
  • Trends in Productivity
    • The more productive a biome is, the wider the diversity of animal life it can support.
    • Water availability, higher temperature, and nutrient availability are all factors that lead to high NPP.
    1. Trophic Levels
    2. The 10% Rule
  • Conservation of Matter and Energy
    • Matter and energy are never created or destroyed; they only change forms.
    • 1st law of thermodynamics: energy is never created or destroyed.
    • Biogeochem cycles demonstrates conservation of matter (C/N/H2O/P)
    • Food webs demonstrate conservation of energy.
  • 2nd Law of Thermodynamics
    • Each time energy is transferred, some of it is lost as heat.
      • Applied to food webs: the amount of useable energy decreases as you move up the food chain (organism use up most of it for movement, development, etc.)
    • Because available energy decreases with each step up the food chain, trophic pyramid (troph = nourishment or growth) is used to model how energy moves through an ecosystem
    • 10% Rule: in trophic pyramids, only about 10% of the energy from one level makes it to the next level; the other 90% is used by the organism and lost as heat.
  • Trophic Levels and 10% Biomass
    • Tertiary consumers: animals that eat secondary consumers or carnivores and omnivores (aka top/apex predators)
    • Secondary consumers: animals that eat primary consumers or herbivores (aka – carnivores and omnivores)
    • Primary consumers: animals that eat plants (herbivores)
    • Producers: (plants) “produce” – really convert sun’s light energy into chemical energy (glucose)
    • 10% rule also applies to biomass (or mass of all living things at each trophic level)
      • Since energy is needed for growth and only 10% of energy transfers from one level to the next, only 10% of the biomass can be grown/supported.
  • To calculate biomass or energy available at the next level up, move the decimal place one spot to the left (or divide by 10)
    1. Food Chains and Food Webs
  • Food Web Basics
    • Shows how matter and energy flow through an ecosystem, from organism to organism.
    • When one organism preys on (eats) another, the matter (C/N/H2O/P) and energy (glucose, muscle tissue, etc.) are passed on to the predator.
    • Arrows in food webs indicate direction of energy flow.
  • Food Web vs Chain
    • The food chain just shows one, linear path of energy and matter.
    • Food webs have at least 2 different interconnected food chains
  • Interactions and Trophic Cascade
    • Food webs show how increases or decreases in population size of a given species impact the rest of the food web.
    • Trophic cascade: removal or addition of a top predator has a ripple effect down through lower trophic levels