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{🌎}
- 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
- 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
- Trophic Structure
- Simple food chains in early stages \longrightarrow complex food webs later.
- Higher trophic levels move as habitat matures.
- Biomass
- Increases: more plant growth = more organic material stored in system
- Soil Development
- Early stages: little or no soil
- Later stages: more organic material, nutrients, and structure in soil
- Nutrient cycling
- Becomes more efficient
- Decomposition and plant uptake become faster and more balanced
- 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{🌱}
- 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{⭐}
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 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
- 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
