Ecology Practice Exam Flashcards

Energy vs. Nutrients in Ecosystems

• Energy Flow
  • Origin: Sunlight \odot
  • Movement: One-way \longrightarrow
  • Pathway: Producers \rightarrow Consumers \rightarrow Decomposers
  • Ends as: Heat lost to the environment (not reusable) \texttt{🔥}
  • Must be constantly replenished.
• Nutrient Cycling
  • Origin: Earth's abiotic reservoirs (air, water, rocks, soil).
  • Movement: Cyclical (reused).
  • Pathway: Biotic uptake \rightarrow waste/death \rightarrow decomposition \rightarrow abiotic return.
  • Ends as: Reused in the ecosystem.
  • Does not need to be constantly added from outside.

Nutrient Cycles

Carbon Cycle

• Major Pools
  • Atmosphere: CO_2
  • Biosphere: Plants and animals.
  • Soil: Organic matter.
  • Oceans: Dissolved CO_2
  • Geological: Fossil fuels, limestone.
• Key Fluxes
  • Photosynthesis: CO_2 \longrightarrow sugars
  • Respiration: Sugars \longrightarrow CO_2
  • Decomposition: Organic matter \longrightarrow CO_2
  • Combustion: Burning fossil fuels \longrightarrow CO_2
  • Ocean-atmosphere exchange.
  • Sedimentation: Marine carbon forms rocks.
• Human Influences
  • Burning fossil fuels \uparrow
  • Deforestation \downarrow
  • Climate change.

Nitrogen Cycle

• Major Pools
  • Atmosphere: N_2 gas \texttt{⭐}
  • Soil: Ammonium, nitrate, organic N.
  • Biota: Proteins, nucleic acids.
  • Water Bodies: Nitrate, ammonium in runoff.
• Major Fluxes
  • Nitrogen Fixation: N2 \longrightarrow NH3 by bacteria or lightning.
  • Nitrification: NH4 \longrightarrow NO2 \longrightarrow NO_3 by bacteria.
  • Assimilation: Plants absorb NH4 or NO3
  • Ammonification: Organic N \longrightarrow NH_4
  • Denitrification: NO3 \longrightarrow N2 gas.
• Human Influences
  • Fertilizers & Fossil Fuel Burning: N pollution.
  • Eutrophication of aquatic systems.
  • Increased Greenhouse Gases: N_2O

Phosphorus Cycle

• Major Pools
  • Rocks (lithosphere).
  • Soil: Inorganic phosphate.
  • Biota: DNA, ATP, bones.
  • Freshwater/Oceans: Sediments.
• Major Fluxes
  • Weathering: Rocks \longrightarrow phosphate in soil.
  • Uptake by Plants: Absorbed as PO_4^{3-}
  • Consumption: Passed through food webs.
  • Decomposition: Organic P \longrightarrow inorganic PO_4^{3-}
  • Sedimentation: Phosphate settle in water bodies.
• Human Influences
  • Fertilizers & Detergents: P runoff.
  • Eutrophication: Algal blooms.
  • Mining phosphate rocks for agriculture.

Decomposition

• Importance \texttt{🌍}
  • Nutrient Cycling
    • Release N, P, and other nutrients back into the soil and water for reuse.
  • Carbon Flow
    • Released CO_2 into the atmosphere via microbial respiration.
  • Soil Formation
    • Builds up organic matter in soil.
  • Ecosystem Productivity
    • Sustains long-term plant growth by replenishing nutrients \hookrightarrow
• Process
  • Leaching: Water removes soluble compounds from dead material.
  • Fragmentation: Detritivores break down material into smaller pieces.
  • Chemical Alteration: Microbes and fungi break down complex molecules.
  • Mineralization: Organic compounds \longrightarrow inorganic nutrients.
• Factors Affecting Decomposition \texttt{🛞}
  • Temperature: Warmer = faster.
  • Moisture: Moderate is best.
  • Oxygen Availability: More oxygen = faster.
  • Litter Quality: High nitrogen, low lignin = faster.

Ecological Succession

• Definition \texttt{🌿}
  • The natural, directional change in a community's structure and composition over time.
  • Occurs as ecosystems recover from disturbances or colonize new environments.
• Changes During Succession \texttt{🌎}
  1. Species Composition
     • Early Succession: Dominated by pioneer species (fast-growing, small, hardy organisms like grasses, mosses).
     • Later Stages: Slower-growing, competitive species take over (e.g., shrubs and trees).
     • Late Succession/Climax: Stable community with high species diversity and complex interactions.
     • Climax community: species replace themselves - Described by frederic clements
  2. Biodiversity
     • Increases in species richness and evenness as new niches are created.
     • Eventually levels off or may decline slightly in mature systems.
     • Trends: Organic matter, moisture, and Nitrogen increase; Soil density, pH, and Phosphorous are stable then drop off
  3. Trophic Structure
     • Simple food chains in early stages \longrightarrow complex food webs later.
     • Higher trophic levels move as habitat matures.
  4. Biomass
     • Increases: more plant growth = more organic material stored in system
  5. Soil Development
     • Early stages: little or no soil
     • Later stages: more organic material, nutrients, and structure in soil
  6. Nutrient cycling
     • Becomes more efficient
     • Decomposition and plant uptake become faster and more balanced
  7. Productivity
     • Gross and net primary production rise during early stages
     • May stabilize or slightly decrease in very late stages as respiration increases
• Ways to Study Succession \texttt{🔎}
  • Chronosequence: Ordered sequences of sites with different beginning times (ex: Hawaiian Islands).
  • Old Field Succession:
    • 0-15 years: non-woody plants (annual and herbaceous).
    • 15-30 years: first woody plants (shrubs).
    • 30-60 years: soft wood (softwood trees like tulip).
    • More than 60 years: hard wood (oaks).
• Mechanisms of Succession \texttt{🦾}
  • Facilitation model: Early species improve conditions for later species.
  • Tolerance model: Early species are replaced by species more able to survive in new conditions (e.g., a dense, early successional tree may be replaced by a more lose/open tree).
  • Inhibition model: Early species prevent others from colonizing (ex: Moss dominates the intertidal zone after a disturbance)

Primary vs. Secondary Succession

• Primary Succession
  • Definition: Succession that begins in an area with no soil or previous biological community.
  • Starts from: Bare rock, lava flows, glacial retreat, dunes.
  • No organic matter.
  • Pioneer Species: Lichen, mosses, microbes \texttt{🌱}
    • Organisms that can survive in harsh conditions and begin soil formation.
  • Speed: Very slow (can take hundreds to thousands of years) \texttt{🐢}
    • Must build soil from scratch
• Secondary Succession
  • Definition: Succession that occurs in an area where a biological community was previously present and soil remains intact.
  • Starts from: After disturbances like fire, flood, farming, logging, or hurricane.
  • Soil is already present, possibly with seeds or roots.
  • Pioneer Species: Grasses, herbs, shrubs \texttt{🌱}
    • Fast-growing species.
  • Speed: Much faster than primary succession (decades to centuries) \texttt{⏱️}

Chronosequences

• Definition
  • A chronosequence is a set of different sites that are similar in all aspects except age.
  • Each site represents a different stage of succession, allowing scientists to study how ecosystems change over time without waiting for decades or centuries.
• Example \texttt{🔬}
  • Imagine four abandoned farm fields: One left alone for 1 year, one for 10 years, one for 50 years, and one for 100 years.
  • By comparing plant types, soil nutrients, and biomass at each site, scientists can reconstruct how succession progresses over a century.
• Benefits \texttt{✅}
  • Saves time.
  • Shows long-term trends.
  • Reveals stages of succession.
  • Used in many ecosystems

Geographic Ecology

• Definition
  • Geographic patterns of plant and animal life.
  • Typically LARGE scale
  • Biogeography: The study of regional patterns of distribution of organisms

Global Biodiversity Patterns

• Diversity is lowest at the poles.
• Diversity is higher at lower latitudes (tropics).
• Tropics are between 23.5°N and 23.5°S.
• Endemic: In one habitat and nowhere else.
• Biodiversity Hotspots: High diversity.

Latitudinal Variation in Species Richness

• Exceptions
  • Specific wasp/Insect parasitoids: Bell curve, Peak at 33°N.
  • Penguins: Peak is towards the south pole.
• Hypotheses
  • Productivity: Higher primary production near the equator supports for individuals and thus more species
  • Environmental heterogeneity, wide variety of soil types: Diversity of habitats, More soil types, Microclimates, Provides more niches.
  • Favorableness/climate harshness/climate stability: Stable climates reduce extinction rates and allows speciation.
  • Niche breadth, interspecific interactions: Narrower niches and more intense interactions.
  • Historic and geographic factors, e.g.: time since perturbation: Less affected by disturbances.
  • Evolutionary rate or effective evolutionary time: Faster evolution and more time without disruption \longrightarrow speciation.
  • More Land \texttt{⭐}
    • Stable Temperature

Island Biogeography

• Island Definition \texttt{🏖}
  • Any isolated habitat (sky islands: top of mountains or lakes: locked inside).
    • Have a subset of mainland species.
• Equilibrium Model of Island Biogeography
  • Species richness is driven by:
    • Immigration
    • Extinction
  • Immigration Rates
    • Highest on a new island with no organisms (\because anything arriving is an immigrant).
    • As species begin to accumulate, rate of immigration declines (\because fewer arrivals would be new species).
  • Extinction Rates
    • More species = larger pool of potential extinctions.
    • More species = each population size is lower.
    • More species = more competition.
  • Prediction
    • Higher species richness on large island, near the mainland.

Landscape Ecology

• Definition
  • Distribution and arrangement of ecosystems on a large scale.
  • "Studying and influencing the relationship between spatial pattern and ecological process across hierarchical levels of biological organization and different in space and time."
  • Mostly just about landscape structure.
  • Useful in conservation, land-use planning, and understanding ecological resilience.
• Landscape Structure
  • Created by:
    • Geological processes
    • Climate
    • Fire
    • Organisms (earthworms create mounds with poop and live on the mounds)
  • Description of landscape structure including elements such as patches \texttt{⭐}
    • Patches: Discrete area that is relatively uniform compared to their surroundings
      • Can vary in size, shape, type
    • Matrix: Background or dominant land cover in a landscape that surrounds patches
      • Has major influence on movement and ecological flow
    • Corridor: Linear features that connect patches and help organisms move Describe
  • What differs between patches?
    • Biodiversity, nutrients, species richness/evenness
• Methods to Capture Landscape-Scale Information
  • Remote Sensing
    • Using satellite or aircraft to gather data about the Earth’s surface.
    • Captures land cover types, vegetation health. Etc.
    • Strengths: large-scale coverage, repeated data collection
  • LiDAR
    • Sensor emits rapid laser pulses toward the ground
    • These pulses bounce back when they hit the surface
    • The time it takes for the light to return is used to calculate distances and create 3D
  • Satellite
    • Use reflective data to calculate temperature
    • NDVI: Use near infrared and red light to calculate vegetation
    • LAI: amount of leaf area per unit ground area
  • Ground Truthing: Verifying remote sensing data by collecting observations and measurements
  • GIS: store, analyze, and visualize spatial data
    • Puts all the layers together
  • Grain size (resolution) is very important
    • Smallest unit of measurement in spatial data
    • Need to choose the right resolution
  • Quantify patch shape based on edge-area (P/A) ratio
    • Perimeter Area
    • Edge (perimeter) to area ratio: P/A
      • Patch size index
        • Closer to 1 is circular
• Edge Effect
  • Same area, but patch effect changes the habitat space
  • 70% of the worlds forest are within 1 km of an edge
    • Land use / Land cover change
    • Invasive species
    • Human population growth
      • Birth rates are decreasing right now
• Corridors
  • Connectivity
    • The degree to which one patch is available to individuals in another patchHow easily can species move between patches
  • To help this, we create corridors
    • How very large edge effect but
    • Allow for improved dispersal between patches
    • Tested with butter fly Both species did better in the connected patches

Conservation Biology

• Definition
  • Study of how to conserve (protect, maintain, & restore) biodiversity.
  • May include aspects of population genetics, populations, community, ecosystem, geographic, and landscape ecology
• Species Employed in Conservation
  • Indicator Species
    • Restricted niches
    • May be first lost OR only show up when there is pollution
    • May flies🦗; narrow niches
  • Umbrella Species
    • Require large area
    • If protected, also protects other species
    • North Atlantic Right Whale

Global Climate Change

• Evidence and Causes
  • “Warming of the Climate System is unequivocal.” \texttt{⭐}
  • “It is extremely likely that human influence has been the dominant causes of the observed warming since the mid-20th century.”
  • Greenhouse effect:
    • 29% reflected
    • 23% absorbed in atmosphere
    • 48% absorbed at the surface
• Consequences
  • Think Pair Share
    • Glacier melts = sea levels rise
    • Extreme temperatures
    • Unusual seasonality
    • Worse hurricanes
• Arrangement of patches is important
  • Mandelbrot (1967)
    • How long is the coast of Britain?
    • He is known for fractal geometry
    • Ruler Length
• Climate Change Effects
  • Warmer on average
  • Extreme weather events
    • Droughts, hot/cold spells, heavy rain
  • Melting glaciers
    • Sea level rises
      • From polar ice caps
      • Water expanding as it gets warmer
  • Ocean acidification
    • Some CO_2 dissolved in the ocean
  • Challenging for agriculture \texttt{⭐}
  • Disease outbreaks
• Temperature Changes
  • 4-7° C change over 5000 years; Current Rate: 0.7° C last 100 years
  • Respiration, melting, etc. will increase rate \texttt{⭐}
  • Minimum temperatures will rise \texttt{☀️}
  • Extreme heat \texttt{🔥}
  • Increase in heavy rain events \texttt{🌧}
  • Droughts \texttt{🌵}
  • Species must adapt, disperse, or go extinct \texttt{⭐}

Land Use/Land Cover Change

• > ½ of wetlands in the contiguous US have been drained and converted
• Some ecosystem <5% of original extent remaining
• Loss of tropical rainforests
• Ecosystem services
  • Purification of air/water
  • Detoxification and decomposition of wastes
  • Cycling nutrients
  • Moderation of weather extremes
• Ecosystem effects
  • Habitat loss Forest, wetlands, grasslands are cleared Reducing biodiversity
  • Disrupted nutrient cycle Alter nutrients like N/P
  • Increased invasive species disturbed/cleared land is more vulnerable to invasive species
  • Altered water flow Paved surfaces increase runoff and decrease groundwater recharge Affects aquatic habitats
• Human Population Effects
  • Resources Access Improves food and housing Strain natural resources like water and soil
  • Health Impacts Air/water pollution from agriculture or urban expansion can lead to respiratory issues and disease
  • Natural Disaster Risk Removing vegetation increases risks of flooding, erosion, landslides

Invasive Species

• Definition
  • Non-native (did not evolve in the area), alien/exotic, invasive (causing damage).
  • They are in every taxa (plants, animals, fungi, bacteria, insects)
  • They are moved by humans (intentionally/unintentionally)Some are brought in for landscaping, ag, pest control - escape/released
• Problems Caused by Invasive Species
  • Outcompete native species for food, space, or light
  • Alter food webs by becoming dominant predator/prey
  • Spread disease
  • Disrupt nutrient cycling and soil composition
  • Reduce biodiversity, sometimes pushing native species to extinction
  • \$120 billion in damage in US alone; \$100 million in prevention, detection, management, research
  • Global Cost = \$26.8 billion

Mitigating Global Change

• Reduce carbon footprint
• Use energy-efficient appliances
• Walk/bike
• Eat less meat
• Support sustainable practices
  • Buy local
  • Organic
  • Fair trade
• Conserve water and energy