Ecosystems and Biomes Study Guide

Ecosystem Basics

  • Individual = One organism (e.g., elk).

  • Population = Group of individuals of the same species (e.g., elk herd).

  • Community = All living organisms in an area.

  • Ecosystem = All living (biotic) and nonliving (abiotic) things in an area (e.g., plants, animals, rocks, soil, water, air).

  • Biome = Large area with similar climate conditions that determine the plant and animal species present. Example: tropical rainforest.

Organism Interactions

  • Mutualism: Relationship that benefits both organisms (e.g., coral reef).

  • Competition: Organisms fighting over a limited resource like food or shelter, which limits population size.

  • Predation: One organism using another for energy source, including hunters, parasites, and even herbivores.

  • Commensalism: Relationship that benefits one organism and has no impact on the other (e.g., birds nesting in trees).

Predator-Prey Relationship

  • The predator-prey relationship oscillates, with predator populations lagging behind prey populations.

  • An increase in prey population leads to an increase in predator population due to more available food.

  • As predator population increases, the prey population declines due to increased predation.

  • The decline in prey then causes a decline in the predator population due to food deficiency.

  • This cycle continues with prey populations eventually recovering, starting the cycle anew.

Predation

  • Predators: Carnivores that kill and eat prey for energy (e.g., leopard & giraffe).

  • Herbivores: Plant eaters that consume plants for energy (e.g., giraffe & tree).

  • Parasites: Use a host organism for energy, often without killing the host and frequently live inside the host (e.g., mosquitoes, tapeworms, sea lamprey).

  • Parasitoids: Lay eggs inside a host organism; eggs hatch, and larvae eat the host for energy, eventually killing it (e.g., parasitic wasps, bot fly).

Symbiosis

  • Symbiosis definition: sym = together | bio = living | osis = condition. Any close and long-term interaction between two organisms of different species.

  • Mutualism (+/+), commensalism (+/0), and parasitism (+/-) are all types of symbiotic relationships.

  • Example of Mutualism: Coral and Algae

    • Coral (animals) provide reef structure & CO_2 for algae.

    • Algae provide sugars for coral to use as energy..

  • Lichen = composite organism of fungi living with algae; algae provide sugars (energy) & fungi provides nutrients

Competition and Resource Partitioning

  • Resource partitioning: Different species using the same resource in different ways to reduce competition. Reduces population size since there are fewer resources available & fewer organisms can survive.

  • Temporal partitioning: Using a resource at different times (e.g., wolves and coyotes hunting at different times—night vs. day).

  • Spatial partitioning: Using different areas of a shared habitat (e.g., different length roots).

  • Morphological partitioning: Using different resources based on different evolved body features (e.g., Darwin’s Finches).

Biomes

  • Biomes: Large regions characterized by distinct climate conditions, specifically yearly temperature and precipitation averages.

  • The community of organisms (plants & animals) in a biome are uniquely adapted to live in that biome.
    *Example: camels & cacti have water preserving traits for desert; shrubs & wildflowers store lots of energy in roots to recover quickly from fire in grasslands

  • Latitude (distance from the equator) determines temperature & precipitation, explaining why biomes exist in predictable patterns on Earth.

  • Deserts are typically located around 30° latitude.

  • Tundra & Taiga/Boreal biomes are found at higher latitudes (>60°).

  • Temperate biomes are at mid-latitudes (30°-60°).

  • Tropical biomes are closer to the equator.

Climate and Elevation/Altitude

  • As elevation increases:

    • Soil and nutrient availability decrease, leading to fewer plants.

    • Oxygen levels decrease due to lower air pressure, resulting in a thinner atmosphere, supporting fewer organisms.

    • Temperature decreases.

    • UV ray exposure increases, limiting plant growth and causing damage.

Terrestrial Biomes

  • Terrestrial biomes are classified by precipitation and temperature patterns.

  • These patterns determine the types of vegetation and animals specifically adapted to the climate.

Nutrient Availability

  • Tropical rainforest: Nutrient-poor soil due to high competition from numerous plant species.

  • Boreal forest: Nutrient-poor soil due to low temperature & slow decomposition rate of dead organic matter.

  • Temperate forest: Nutrient-rich soil due to abundant dead organic matter (leaves) and warm temperature/moisture that support decomposition.

  • Plants need soil nutrients to grow, so availability determines which plants can survive in a biome. Ex: frozen soils of tundra/boreal forests don’t allow nutrients in dead organic matter to be broken down by decomposers - Low soil nutrients - Low water availability - Few plants survive here

Shifting Biomes

  • Biomes shift in location on Earth as climate changes.
    *Example: warming climate will shift boreal forests further north as tundra permafrost soil melts & lower latitudes become too warm for aspen & spruce.

Climate Graphs

  • Climate graphs show average rainfall and temperature for each month of the year.

    • Precipitation is indicated by bars.

    • Temperature is indicated by a line.

Aquatic Biomes Characteristics

  • Depth: influences how much sunlight can penetrate and reach plants below the surface for photosynthesis, affecting temperature and nutrient availability.

*Temperature:
* Warmer water holds less dissolved O_2, which can support fewer aquatic organisms.
*Salinity:
* The amount of salt in a body of water, determines which species can survive & usability for drinking (Fresh water vs. estuary vs. ocean)

  • Flow: Determines which plants & organisms can survive, how much O_2 can dissolve into water *Turbidity:

    • Measure of clarity of water → how much light is scattered. Affected by amount and movement of particulate matter

  • Nutrient Availability

    • Greater nutrient availability with cold upwellings in oceans

    • Increased with higher net productivity

Freshwater Biomes

  • Rivers: Have high O_2 levels due to flow mixing water & air and carry nutrient-rich sediments (deltas & flood plains = fertile soil).

  • Lakes: Standing bodies of fresh H2O (key drinking H2O source).

    • Littoral zone: Shallow water with emergent plants.

    • Limnetic zone: Where light can reach (photosynthesis); no rooted plants, only phytoplankton.

    • Profundal zone: Too deep for sunlight (no photosynth.).

    • Benthic zone: Murky bottom where invertebrates live; nutrient-rich sediments.

Freshwater: Wetlands

  • Wetland: Area 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:

    • Store excess water during storms, lessening floods.

    • Recharge groundwater by absorbing rainfall into soil.

    • Roots of wetland plants filter pollutants from water draining through.

    • Highly plant growth due to lots of water & nutrients (dead organic matter) in sediments.

Estuaries, Salt Marshes, Mangrove Swamps

*Estuaries:
* areas where rivers empty into the ocean.
* Mix of fresh & salt water (species adapt to this ex: mangrove trees).
* 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 many fish & shellfish species
*Mangrove Swamps:
* Estuary habitat along coast of tropical climates
* Mangrove trees with long, stilt roots stabilize shoreline & provide habitat for many species of fish & shellfish

Coral Reefs

  • Warm shallow waters beyond the shoreline; most diverse marine (ocean) biome on earth.

  • Mutualistic relationship between coral (animals) & algae (plants).

  • Coral take CO2 out of ocean to create calcium carbonate exoskeleton (the reef) & also provide CO2 to the algae.

  • Algae live in the reef & provide 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 & CO_2 from the coral’

Intertidal Zones

  • Narrow band of coastline between high & low tide.

  • Organisms must be adapted to survive crashing waves & direct sunlight/heat during low tide Ex: Barnacles, sea stars, crabs that can attach themselves to rocks.

  • Shells & tough outer skin can prevent drying out (desiccation) during low tides.

  • Different organisms are adapted to live in different zones Ex: Spiral wrack (type of seaweed) curls up & secretes mucus to retain water during low tide

Open Ocean (Pelagic)

  • Low productivity/area as only algae & phytoplankton can survive in most of ocean.

  • Photic zone = area where sunlight can reach (photosynthesis)

  • Aphotic zone (abyssal) = area too deep for sunlight. So large though, that algae & phytoplankton of ocean produce a lot of earth’s O2 & absorb a lot of atmospheric CO2

Nutrient Cycle

  • Nutrients are stored in biomass, litter, and soil.

  • Nutrients are transferred through uptake by plants, release as litter decomposes, and fallout as tissues die.

  • Nutrients are gained through input from weathered rock and dissolved in rainfall.

  • Nutrients are lost through loss in runoff and loss by leaching.

Biome Nutrient Cycling Models (Gersmehl Diagrams)

  • Biomes can be compared by relative sizes of nutrient stores (biomass, soil, litter) and flows between them.

  • Factors such as temperature and precipitation affect nutrient cycling within a biome.

Carbon Cycle Overview

  • Movement of molecules that contain carbon (i.e. CO2, glucose, CH4, organic compounds) between sources and sinks.

  • Sinks store more carbon than they release. Sources release carbon. * QUICK MOVEMENT:

    • Fossil Fuel combustion

    • Respiration and Photosynthesis

    • Food Web

    • Decomposition

  • SLOW MOVEMENT

    • Sedimentation

    • Burial

    • Fossil Fuel Production/Storage

Carbon Sources and Sinks

  • Carbon reservoir/sink: A carbon reservoir that stores more carbon than it releases
    *Ocean (algae & sediments)
    *Plants and Animals
    *Soil
    *Stored Fossil Fuels
    *Atmosphere

  • Carbon source: Processes that add C to the atmosphere
    *Fossil fuel combustion
    *Animal agriculture (cow emissions = CH4) *Deforestation/burning (releases CO2)
    *Volcanic Eruptions
    *Decomposition / Respiration
    *Anthropogenic Actions
    *Lead to imbalance in sinks/reservoirs. Because create faster Movement from Sources To Sinks

Ocean and Atmosphere Interaction in the Carbon Cycle

  • Direct exchange: CO2 moves directly between the atmosphere & the ocean by dissolving into & out of ocean water at the surface. Happens very quickly & in equal directions. Increase in atmospheric CO2 → increased in dissolvedCO_2 Leading to ocean acidification INTO SINK/RESERVOIR

  • Algae & phytoplankton: take CO_2 out of the ocean & atmosphere through photosynthesis

  • Coral reef & marine organisms with shells: take CO_2 out of the ocean → calcium carbonate exoskeleton

  • Sedimentation: when marine organisms die, their bodies/shells sink to ocean floor broken down into sediments and form into layered rocks.
    *Sediments (bits of rock, soil, organic matter) compressed into sedimentary rock, or fossil fuels by pressure from overlying rock layers or water

Carbon Cycle: The slow cycle versus human impact.

  1. Plants absorb CO2 from air to grow and decompose to release CO2. This is one part of the natural carbon cycle.

  2. The rocks are uplifted and weathered to release carbon to soils and the atmosphere.

  3. The exchange of sea and air of CO_2.

  4. Phytoplankton take up CO_2.

  5. Some carbon sinks to depths in the form of decyaing biota.

  • Over millions of years, carbon can be incorporated into rocks or turned into hydrocarbons.

  • Air and sea exchange CO_2.

  • Zooplankton eat phytoplankton and respire CO_2.

  • Some carbon sinks to the depths in the form of decaying biota and fecal pellets.

Carbon Cycle: Burial, Extraction, & Combustion

  • Burial: slow, geological process that stores carbon in underground sinks like sedimentary rock or fossil fuels.

  • Fossil Fuels (FF): coal, oil, and natural gas are formed from fossilized remains of organic matter (e.g., dead ferns for coal, marine algae & plankton for oil).

  • Extraction & Combustion: digging up or mining FFs & burning them as energy source; releases CO_2 into atmosphere.

  • Burial (formation of FFs) is slower than extraction & combustion, so net movement is an increase concentration of CO_2 in atmosphere. THE SINK TURNS INTO A SOURCE

Nitrogen Cycle Overview

  • The nitrogen cycle describes the movement of nitrogen through various sources and sinks.

  • Atmosphere = main N reservoir

  • Sources release N into the atmosphere; sinks take N out of the atmosphere in increasing amounts

  • Nitrogen = critical plant & animal nutrient

  • All living things need N. -DNA -amino acids to make proteins

  • N reservoirs hold N for relatively short period of time compared to C cycle- Ex: plants, soil, atmosphere.

  • How do living things take in N if most exists as unuseable N_2 gas?

Nitrogen Fixation

  • Nitrogen fixation converts atmospheric N_2 gas into usable forms for plants.

  • Bacterial fixation: certain bacteria that live in thesoil, or in symbiotic relationship with plant rootnodules convert N2 into ammonia (NH3). Rhizobacteria live in root nodules of legumes (peas, beans) & fix N for them in return for amino acids from the plant.

  • Synthetic fixation: humans combust FFs to convert N2 gas into nitrate (NO3 -).

  • Nitrates are added to synthetic fertilizers like miracle grow & used in agriculture

Other Steps in the Nitrogen Cycle

  • Nitrification: Conversion of NH3/NH4 + into nitrite (NO2 -) & then nitrate (NO3 -) by soil bacteria

  • Ammonification: Soil bacteria, microbes & decomposers converting waste & dead biomass back into NH_3 and returning it to soil

  • Assimilation: Plants & animals taking N in and incorporating it into their body. Plant roots take in NO3 - or NH3 /NH_4 + from soil (take inorganic N compounds and turn into organic N compounds) then animals assimilate N by eating plants or other animals;

  • Denitrification: Conversion of soil N (NO3 -) into nitrous oxide (N2O) or N_2 gas which returns to atmosphere

Human Impacts on the Nitrogen Cycle

  • Leaching & Eutrophication: synthetic fertilizer use leads to nitrates (NO_3 -) leaching, or being carried out of soil by water

  • Climate: N_2O (nitrous oxide) = greenhouse gas which warm earthʼs climate

  • Ammonia volatilization: excess fertilizer use can lead to NH3 gas entering atmosphere-NH3 gas in atm = acid precipitation (rain) and respiratory irritation in humans & animals It also means less N stays in soil for crops to use for growth (lost profit)

  • Nitrates runoff into local waters, causing algae blooms that block sun & kill other aq. plants

Phosphorus Cycle Basics

*The P cycle is very slow compared to C/H_2O/N cycles

  • Movement of P atoms & molecules b/w sources & sinks/reservoirs.
    *Rocks & sediments containing P minerals = major reservoirs. Takes a long time for P minerals to be weathered out of rocks & carried into soil/bodies of water.
    *No gas phase of P (doesn’t enter atmosphere). B/c it cycles so slowly, it is a limiting nutrient, meaning plant growth in ecosystems is often limited by P availability in soil/water.

  • P is needed by all organisms for DNA, ATP (energy), bone & tooth enamel in some animals.

Phosphorus Sources

  • Major natural source of P is weathering of rocks that contain P minerals. Wind & rain break down rock & phosphate (PO_4 -3) is released and dissolved into water; rain water carries phosphate into nearby soils & bodies of water.

  • Synthetic (human) sources of P = mining phosphate minerals & adding to products like synthetic fertilizers & detergents/cleaners.
    *Weathering is so slow that P is often a limiting nutrient in aquatic & terrestrial ecosystems.

Phosphorus Cycle - Assimilation & Excretion/Decomposition

  • Just like N, P is absorbed by plant roots & assimilate into tissues; animals assimilate P by eating plants or other animals.

  • Animal waste, plant matter & other biomass is broken down by bacteria/soil decomposers that return phosphate to soil
    *Phosphate doesn’t dissolve very well into water; much of it forms solid bits of phosphate that fall to the bottom as sediment (sedimentation).
    *P sediments can be compressed into sed. rock over long time periods by pressure of overlying water
    *Sedimentation & Geological Uplift Geological uplift = tectonic plate collision forcing up rock layers that form mountains; P cycle can start over again with weathering & release of phosphate from rock.
    *Assimilation & excretion/decomp form a mini-loop within P cycle just like assimilation & ammonification in N Cycle, photosynth & resp. in C cycle

Eutrophication from Excess Nitrogen and Phosphorus

  • Extra input of N & P lead to eutrophication (excess nutrients) which fuels algae growth.

  • Algae bloom covers surface of water, blocking sunlight & killing plants below surface. **Can occur from fertilizer runoff, human/animal waste contamination

  • Algae eventually die-off; bacteria that break down dead algae use up O2 in the water (b/c decomp. = aerobic process). Lower O2 levels (dissolved oxygen) in water kills aquatic animals, especially fish

  • Bacteria use up even more O2 to decompose dead aq. animals - Creates pos. feedback loop: less O2 → more dead org. → more bacterial decomposition → less O_2

Water Cycle Overview

  • Movement of H_2O (in different states) b/w sources & sinks.
    *Ex: precipitation = atm. (gas) → land or surface water (liquid).

  • Energy from the sun drives the H2O cycle. State of matter (solid/liquid/gas) as well as where water is moving are key in H2O cycle
    *Ex: heat from sun causes liquid water in ocean to become a gas (evaporation) in atm.

  • Ocean = largest water reservoir Ice caps & groundwater are smaller reservoirs, but contain fresh, useable water for humans.

Runoff & 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) & surface waters (lakes/rivers) are important freshwater reservoirs for humans & animals

  • Precipitation recharges groundwater through infiltration, but only if the ground is permeable (able to let water pass through).

  • Runoff recharges surface waters, but can also carry pollutants into water sources

Evaporation & Evapotranspiration

  • Two main processes cycle water from liquid on earth back into the atmosphere.
    *Transpiration: process plants use to draw groundwater from roots up to their leaves. Leaf openings called stomata open, allowing water to evap. into atm. from leaf.

  • Evapotranspiration: Amount of H_2O that enters atm. from transpiration & evap. combined. Both processes are driven by energy from the sun

Photosynthesis & Cellular Respiration

  • Photosynthesis:

    • Removes CO_2 from the atmosphere & converts it to glucose - Glucose = biological form of C & stored (chemical) energy in form of sugar

    • Done by plants, algae, phytoplankton

    • CO_2 sink

  • Cellular Respiration:

    • Done by plants & animals to release stored energy. Uses O2 to break glucose down & release energy. Releases CO2 into atmosphere

    • CO2 source (adds CO2 to atm.)
      *Both processes are very quick. Cycle C between biosphere & atmosphere in balanced amount (no net C increase in atm.)

Primary Productivity Basics

*Primary Productivity: rate that solar energy is converted into organic compounds via photosynthesis over a unit of time *units: kcal/m2/yr. area time
PP Basics
*It is the rate of photosynthesis of all producers in an area over a given period of time
*Photosynthesis leads to growth via carbon compounds made from CO_2.
*So, it is the amount of plant growth in an area over a given period of time
*High Primary Productivity equates to:
*high plant growth
*lots of food & shelter for animals
*higher biodiversity

Calculating Primary Productivity

*Gross Primary Productivity (GPP): The total amount of sun energy (light) that plants capture and convert to energy (glucose) through photosynthesis
*Think of GPP as the total paycheck amount the plant earns
*Respiration loss (RL): plants use up some of the energy they generate via photosynthesis by doing cell. respiration
*Think of RL as taxes plant needs to pay
*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 plant’s paycheck it keeps after taxes. NPP = GPP - RL

Ecological Efficiency

*The portion of incoming solar energy that is captured by plants & converted into biomass (NPP or food available for consumers).
*Generally, only 1% of all incoming sunlight is captured & converted into GPP via photosynthesis Of that 1%, only about 40% (or 0.4% 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 (higher biodiversity)

  • Water availability, higher temperature, and nutrient availability are all factors that lead to high NPP Shortage of any of these three factors will lead to decreased NPP

Light Absorption and Reflection in Ecosystems

*Visible Light
*A red object reflects red and absorbs other colors.
*A white object reflects all colors equally.
*A black object absorbs all colors of white light.

Limited Light Availability in Deep Marine Environments

*Red and Blue Light most important for photosynthesis
*Euphotic Zones receive full range of light
*Turbidity and Angle of the sun affects the amount of light that can penetrate
*Deeper depths receives less sunlight, with red vanishing first, then blue (short wavelengths travel farthest)
*Aphotic zones do not get any sunlight

Aphotic zones

*No plants; bacteria use other mechanisms to drive primary productivity.
*Chemosynthesis
*Hydrocarbons or hydrogen sulfide

Conservation of Matter & Energy

*Matter & energy are never created or destroyed; they only change forms Ex: Tree dies & the C/N/H2O/P are returned to the soil & atmosphere. *Ex: Sun rays (light energy) hit leaves & are converted into glucose (chemical energy) 1st law of thermodynamics: energy is never created or destroyed-Biogeochem. cycles demonstrate conservation of matter (C/N/H2O/P) Food webs demonstrate conservation of energy. Ex: When a rabbit eats a leaf, the energy from the leaf (glucose) is transfered to the rabbit & stored as body tissue like fat/muscle

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 (organisms use up most of it for movement, development, etc.)
*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 & lost as heat-Because available energy decreases with each step up the food chain, a trophic pyramid (troph = nourishment or growth) is used to model how energy moves through an ecosystem

Trophic Levels & Biomass

*Producers (plants) “produce”- really convert sun’s light energy into chemical energy (glucose)
*Primary Consumers: animals that eat plants (herbivores)
*10% rule also applies to biomass (or mass of all living things at each trophic level)-Since energy is needed for growth & only 10% of energy transfers from one level to the next, only 10% of the biomass can be grown/supported
*Secondary Consumers: animals that eat primary consumers or herbivores (aka - carnivores & omnivores)
*Tertiary Consumers: animals that eat secondary consumers or carnivores & omnivores (aka - top/apex predators)

Food chains and food webs

*A food web is a model of an interlocking pattern of food chains that depicts the flow of energy and nutrients in two or more food chains.
*Positive and negative feedback loops can each play a role in food webs. When one species is removed from or added to a specific food web, the rest of the food web can be affected.

Food Web Basics

  • Shows how matter & energy flow through an ecosystem, from organism to organism

  • When one organism preys on (eats) another, the matter (C/N/H_2O/P) and energy (glucose, muscle tissue, etc.) are passed on to the predator

  • Arrows in food webs indicate the direction of energy flow (point to the org. taking in the energy)

Food Webs vs. Food Chains

*Food chains show one, linear path of energy & matter.
*Food webs have at least 2 different, interconnected food chains
*Webs show that organisms can exist at different trophic levels grass → hare → fox (sec. cons.) grass → grasshopper → mouse → fox (tert. cons.)

Interactions & Trophic Cascade

*Food webs show how increase or decreases in pop. size of a given species impact the rest of the food web Ex: Increase in python pop. -Decrease in frog & rat pops. -Increase in grasshopper pop. -Decrease in corn
*Trophic cascade: removal or addition of a top predator has a ripple effect down through lower trophic Levels Ex: decline in wolf pop. = increase in deer pop. which leads to overgrazing & decline in trees