Community ecology - The study of interactions among species
Symbiosis - Two species living in a close and long-term association with one another in an ecosystem
Competition - The struggle of individuals, either within or between species, to obtain a shared limiting resource
Competitive exclusion principle - The principle stating that two species competing for the same limiting resource cannot coexist
Resource partitioning - When two species evolve to divide a resource based on differences in their behavior or morphology
Predation - An interaction in which one animal typically kills and consumes another animal
Parasitoids - A specialized type of predator that lays eggs inside other organisms (the host)
Herbivory - An interaction in which an animal consumes plants or algae
Mutualism - An interaction between two species that increases the chances of survival or reproduction for both species
Photosynthesis - The process by which plants and algae use solar energy to convert carbon dioxide (CO₂) and water (H₂O) into glucose (C₆H₁₂O₆) and oxygen (O₂)
Commensalism - An interaction between two species in which one species benefits and the other species is neither harmed nor helped
Native species - A species that lives in its historical range, typically where it has lived for thousands or millions of years
Exotic species - A species living outside its historical range
Alien species - Alternative term for exotic species
Why it occurs: Resource partitioning occurs because of the competitive exclusion principle. When two species compete for the same limiting resource, natural selection favors individuals that overlap less with the other species in resource use. This reduces competition between the species.
What happens to species: Over many generations, competing species evolve to reduce their overlap in resource use through three main methods:
Temporal partitioning - Using the same resource at different times (e.g., wolves and coyotes hunting at different times of day)
Spatial partitioning - Using different habitats (e.g., desert plants with different root depths)
Morphological partitioning - Evolving different body sizes or shapes (e.g., Galápagos finches with different beak shapes for different foods)
| Type of Interaction | Species 1 | Species 2 |
|---|---|---|
| Competition | - | - |
| Predation | + | - |
| Parasitism | + | - |
| Herbivory | + | - |
| Mutualism | + | + |
| Commensalism | + | 0 |
Biome - Plants and animals found in a particular region of the world
Terrestrial biome - Geographic region categorized by average annual temperature, precipitation, and distinctive plant growth forms
Aquatic biome - Aquatic region characterized by salinity, depth, and water flow
Habitat - Specific area where a particular species lives; subset of a biome
Temperature Categories:
Cold (<5°C): Tundra, Taiga
Temperate (5-20°C): Rainforest, seasonal forest, shrubland, grassland
Tropical (>20°C): Rainforest, savanna, hot desert
1. Tundra - Cold, treeless, 4-month growing season - Permafrost prevents deep roots - Low shrubs, mosses, lichens - Slow decomposition → organic soil accumulation
2. Taiga (Boreal Forest)
- Coniferous evergreens, cold winters - 50-60°N latitude - Poor soils,
short growing season - Major lumber source
3. Temperate Rainforest - Coastal, moderate temps, high precipitation - Giant trees (redwoods 90m tall) - 12-month growing season - Heavily logged
4. Temperate Seasonal Forest - Warm summers, cold winters, >1m precipitation - Deciduous trees (oak, maple, beech) - Fertile soils, high productivity - First converted to agriculture
5. Shrubland (Chaparral) - Hot dry summers, mild wet winters - Fire-adapted drought-resistant shrubs - Mediterranean climates - Ideal for grape cultivation
6. Temperate Grassland - Cold winters, hot dry summers - Rainfall determines grass height - Most fertile soils (98% converted to farms) - Frequent wildfires
7. Tropical Rainforest - Warm, wet, 20°N-20°S of equator - Highest biodiversity, multiple vegetation layers - Rapid decomposition = poor soils despite high productivity - 24,000 ha cleared annually
8. Savanna - Warm temps, distinct wet/dry seasons - Grasslands with scattered deciduous trees - Trees drop leaves in dry season - 99% converted in some regions
9. Hot Desert - ~30°N/S, extremely dry, hot - Water-storing plants with spines - Annual vs perennial plant strategies - Threatened by climate change
Soil Fertility: Grassland > Seasonal forest > Rainforest > Shrubland > Taiga > Tundra > Desert
Growing Season: Tropical (12 months) > Temperate (6-10 months) > Cold (4-6 months)
Decomposition Rate: Tropical > Temperate > Cold
| Biome | Location | General Climate | Soil | Dominant Plants | Animals found in biome |
|---|---|---|---|---|---|
| Tropical rainforest | Near the equator | Hot, wet all year | Poor, thin | Tall trees, vines, epiphytes | Jaguars, monkeys, frogs |
| Desert | Around 30° N & S | Very hot, very dry | Sandy, poor | Cacti, succulents | Camels, lizards, roadrunners |
| Tropical seasonal forest - Savanna | Africa, S. America, Australia | Warm, wet summers, dry winters | Fairly good | Grasses, a few trees | Zebras, lions, cheetahs |
| Woodland-Shrubland | Mediterranean, S. California | Hot dry summers, mild wet winters | Low nutrients | Shrubs, small trees | Quail, coyotes, rabbits |
| Temperate Grassland | Central NA, S. America, Asia | Cold winters, hot summers | Rich, deep | Grasses, wildflowers | Bison, prairie dogs, snakes |
| Northern coniferous forest | Canada, Russia, N. Europe | Cold, some rain | Poor, acidic | Pine, spruce, fir | Bears, moose, wolves |
| Temperate Seasonal Forest | Eastern US, Europe, China | Warm summers, cold winters | Rich | Oak, maple, hickory | Deer, foxes, squirrels |
| Tundra | Arctic, high mountains | Very cold, little rain | Frozen, poor | Moss, lichen, small shrubs | Polar bears, foxes, caribou |
| Temperate Rainforest | Pacific NW, Chile, NZ | Mild, rainy | Low nutrients | Fir, spruce, redwoods | Deer, salamanders, frogs |
Temperature, Rainfall
Tropical Rainforest
Tundra
Because Bananas are a tropical plant and none of the biomes within the US would be very good for growing them. Also importing them from countries with a lower median income can lead to a lower price.
Littoral Zone: Shallow water near shore where plants and algae grow. Most photosynthesis happens here.
Limnetic Zone: Open water where sunlight reaches but rooted plants can’t survive. Only floating algae live here.
Profundal Zone: Deep water with no sunlight. No plants can live here, and oxygen is very low.
Benthic Zone: Muddy bottom of water bodies made of sediments and organic matter.
Oligotrophic Lake: Low-nutrient lake with clear water and few algae.
Mesotrophic Lake: Medium-nutrient lake.
Eutrophic Lake: High-nutrient lake with lots of algae. Water looks green like pea soup.
Coral Bleaching: When stressed corals lose their algae, turn white, and die.
Photic Zone: Upper ocean where sunlight allows photosynthesis.
Aphotic Zone: Deep ocean with no sunlight or photosynthesis.
Chemosynthesis: How bacteria make energy using chemicals instead of sunlight.
Land Biomes:
Water Biomes:
Land Biomes:
Water Biomes:
Main Limiting Factors:
Structure:
Human Threats:
Both land and water biomes:
| Biome | Water Depth (Shallow/Deep) | Salinity (Salty or Not) | Flow/Still | Plants Found | Animals Found | Zones (if any) |
|---|---|---|---|---|---|---|
| Streams/Rivers | Shallow to Deep (varies) | Not salty (freshwater) | Flowing | Algae, mosses, riparian plants | Fish (trout, salmon), insects, amphibians | Headwaters, floodplain, riparian zone |
| Ponds/Lakes | Shallow and Deep zones | Not salty (freshwater) | Still | Algae, cattails, water lilies | Fish, amphibians, zooplankton, insects | Littoral, limnetic, profundal, benthic |
| Freshwater Wetlands | Shallow | Not salty (freshwater) | Still/slow | Grasses, reeds, cattails | Amphibians, insects, birds, fish, mammals | No formal zones |
| Salt Marshes/Estuaries | Shallow | Salty & fresh mix (brackish) | Flowing/tidal | Salt-tolerant grasses, algae | Fish, shellfish, birds, crabs, mammals | Intertidal |
| Mangrove Swamps | Shallow | Salty (coastal) | Tidal flow | Mangrove trees, algae | Fish nurseries, crabs, birds, reptiles | Intertidal |
| Intertidal Zones (coasts) | Shallow (exposed at times) | Salty (marine) | Tidal | Seaweeds, algae | Crabs, mollusks, starfish, shorebirds | High, middle, low tide zones |
| Coral Reefs | Shallow | Salty (marine) | Still/tidal | Coral, algae (zooxanthellae), seagrasses | Fish, mollusks, crustaceans, sea turtles | Photic |
| Open Ocean | Deep | Salty (marine) | Currents | Phytoplankton, kelp (near surface) | Whales, sharks, jellyfish, fish, zooplankton | Photic, aphotic, benthic |
Reservoir - Components of biogeochemical cycles that contain matter (air, water, organisms)
Sink - A reservoir that stores atoms and molecules
Aerobic respiration - Cells convert glucose + oxygen → energy + CO₂ + water
Greenhouse gases - Atmospheric gases that trap heat near Earth’s surface
Global warming - Increased global temperatures due to human greenhouse gas production
Nitrogen fixation - Converts N₂ gas into forms plants can use (NH₃/NO₃⁻)
Nitrification - NH₄⁺ → NO₂⁻ → NO₃⁻ conversion by bacteria
Assimilation - Plants/algae incorporate nitrogen into tissues
Mineralization/Ammonification - Decomposers break down organic matter → NH₄⁺
Denitrification - NO₃⁻ → N₂O → N₂ conversion in oxygen-poor environments
Anaerobic - Lacks oxygen | Aerobic - Has abundant oxygen
Leaching - Dissolved molecules transported through soil via groundwater
Major impacts: - Fossil fuel combustion - Rapidly moves carbon to atmosphere - Deforestation - Releases stored carbon, reduces CO₂ absorption
Result: CO₂ increased from 280 ppm (1800) to 420 ppm today
Largest carbon sink: Sedimentary rocks (limestone/dolomite)
Major impacts: - Synthetic fertilizers - Humans now fix more N than nature - Agricultural runoff - Excess nitrogen leaches into ecosystems - Fossil fuel burning - Creates nitrate deposition
Consequences: Reduced species diversity, altered plant communities, acid precipitation
Largest nitrogen sink: Earth’s atmosphere (78% N₂ gas)
Carbon Cycle: 7 processes - Fast: photosynthesis, respiration, exchange, combustion - Slow: sedimentation, burial, extraction
Nitrogen Cycle: 5 transformations 1. Fixation (N₂ → NH₃/NO₃⁻) 2. Nitrification (NH₄⁺ → NO₃⁻) 3. Assimilation (plant uptake) 4. Mineralization (organic N → NH₄⁺) 5. Denitrification (NO₃⁻ → N₂)
Algal bloom: A rapid increase in algal population in waterways caused by excess nutrients (especially phosphorus) that increases algae biomass.
Hypoxic: Low oxygen conditions in water, often resulting from algae decomposition consuming dissolved oxygen.
Dead zone: Water areas where oxygen levels become so low that fish and aquatic animals die, typically caused by algal blooms and decomposition.
Transpiration: Water release from plant leaves into the atmosphere during photosynthesis.
Evapotranspiration: Combined water loss through evaporation and transpiration from ecosystems.
Runoff: Water flowing across land surfaces into streams and rivers toward the ocean.
Autotrophs (Producers): Plants, algae, and bacteria that use solar energy to produce sugars through photosynthesis.
Cellular Respiration: Process by which cells convert glucose and oxygen into energy, CO₂, and water.
Anaerobic Respiration: Converting glucose into energy without oxygen (less efficient than aerobic respiration).
Primary Productivity: Rate of converting solar energy into organic compounds over time.
Gross Primary Productivity (GPP): Total solar energy captured by producers via photosynthesis.
Net Primary Productivity (NPP): Energy captured by producers minus energy used for respiration.
Biomass: Total mass of all living matter in a specific area.
Standing Crop: Amount of biomass present at a particular time.
NPP = GPP - R - NPP = Net Primary Productivity - GPP
= Gross Primary Productivity
- R = Respiration by producers
Math Problem: Tropical rainforest has NPP = 8,500 kcal/m²/year and GPP = 21,000 kcal/m²/year. Find R.
NPP = GPP - R 8,500 = 21,000 - R R = 12,500 kcal/m²/year
Terrestrial Plants (Green): Use chlorophyll which absorbs red and blue light but reflects green light. All wavelengths available on land.
Deeper Water Plants (Red Algae): Water absorbs red light in upper 1m but blue light penetrates to 100m. Red algae evolved additional pigments to capture available blue light at depth.
Heterotroph (Consumer): Organism that must obtain energy by consuming other organisms.
Primary Consumer (Herbivore): Consumer that eats producers. Examples: zebras, grasshoppers.
Carnivore: Consumer that eats other consumers.
Secondary Consumer: Carnivore that eats primary consumers. Examples: lions, hawks.
Tertiary Consumer: Carnivore that eats secondary consumers. Examples: bald eagles.
Trophic Levels: Successive levels of organisms consuming one another.
Food Chain: Linear sequence of consumption from producers through consumers.
Scavengers: Organisms that consume dead animals (vultures).
Detritivores: Organisms that break down dead tissues into smaller particles (dung beetles).
Decomposers: Fungi and bacteria that convert organic matter into recyclable elements.
The 10% Rule: Only about 10% of energy transfers from one trophic level to the next.
Trophic Pyramid: Representation of energy/biomass distribution among trophic levels.
Food Web: Model showing energy flow through interconnected food chains.
Given: Primary producers have 8,700 J
Answer: Secondary consumers would have 87 Joules.
• Biodiversity: Variety of life at multiple scales; indicator of environmental health
• Genetic Diversity: Genetic variation among individuals in a population; helps species adapt to changes
• Species Diversity: Number of species in a region or ecosystem
• Habitat Diversity: Variety of habitats in an ecosystem; supports different species types
• Specialists: Species with narrow habitat requirements (koalas only eat eucalyptus)
• Generalists: Species that survive in wide range of conditions (white-tailed deer)
• Ecosystem Diversity: Variety of ecosystems in a region
• Species Richness: Number of different species in an area
• Species Evenness: Whether species have similar population sizes or one dominates
• Enhanced stability during environmental changes • Faster recovery from disturbances • Higher primary productivity • Multiple species can fill similar roles if one is lost
• More vulnerable to disruptions • Slower recovery from disturbances • Higher risk of collapse when key species are lost
• Provides long-term population survival through adaptation • Enables disease resistance • Critical for agriculture - genetic variety helps combat new diseases • Loss affects species for thousands of years (cheetah example)
• Creates stable ecological networks • Provides species redundancy for ecosystem functions • Increases productivity through species interactions • Example: diverse soil fungi improve plant growth
• Supports both specialist and generalist species • Allows many species to coexist in different niches • Provides refugia during environmental changes • Loss affects specialists more than generalists initially
Ecosystem services: The processes by which life-supporting resources such as clean water, timber, fisheries, and agricultural crops are produced.
Provisions: Goods produced by ecosystems that humans can use directly (examples: lumber, food crops, medicinal plants, natural rubber).
Provisioning Services - Timber for construction and paper - Maple syrup from sugar maples - Wild berries, nuts, and mushrooms - Medicinal plants like ginseng
Regulating Services - Carbon storage to mitigate climate change - Water cycle regulation through transpiration - Air purification by filtering pollutants - Soil erosion prevention
Supporting Services - Nutrient cycling through leaf decomposition - Wildlife habitat provision - Soil formation from organic matter - Pollination by forest insects
Cultural Services - Recreational hiking and camping - Aesthetic beauty for photography - Educational value for ecology studies - Spiritual benefits from nature connection
Provisioning Services - Commercial fishing (salmon, crabs, oysters) - Salt production through evaporation - Seaweed harvesting - Shellfish aquaculture
Regulating Services - Storm surge protection for coasts - Water filtration before reaching ocean - Carbon sequestration in salt marshes - Flood control during high tides
Supporting Services - Nursery habitat for juvenile marine species - Nutrient cycling between fresh and saltwater - Primary productivity from marsh grasses - Migration sites for waterfowl
Cultural Services - Birdwatching and wildlife observation - Recreational boating and fishing - Marine biology research sites - Cultural significance for indigenous communities
Island biogeography: The study of how species are distributed and interacting on islands.
Species-area curve: How the number of species on an island increases with island area.
Two main factors determine species number:
Flightless ground-nesting birds are most vulnerable because they: - Cannot escape predators - Build accessible nests - Lack predator defenses - Have specialized diets
Small, far islands because they: - Support small populations (extinction-prone) - Receive few replacement colonists - Have limited habitat diversity - Cannot support complex food webs
Ecological Tolerance (Fundamental Niche): The range of abiotic conditions where a species can survive, grow, and reproduce.
Realized Niche: The actual conditions where a species lives after biotic interactions (competition, predation, disease) further limit its distribution.
Geographic Range: Areas of the world where a species actually lives.
Mass Extinction: Large numbers of species going extinct over short time periods due to major environmental changes.
Five historical mass extinctions occurred when environmental changes exceeded species’ tolerance limits: - 251 million years ago: 90% marine species extinct from unknown environmental changes - 65 million years ago: Meteorite impact blocked sunlight, halting photosynthesis
Human activities push species beyond tolerance through: - Rapid climate change: Faster than species can adapt or migrate - Habitat destruction: Eliminates suitable environments - New stressors: Invasive species, pollution, disease
Species go extinct when: 1. No suitable habitat remains within tolerance range 2. Physical barriers prevent migration 3. Better competitors occupy new habitats 4. Changes occur too rapidly for adaptation
Periodic disruptions - Regular, predictable disruptions like day/night cycles or tidal cycles.
Episodic disruptions - Somewhat regular disruptions like rain/drought cycles every 5-10 years.
Random disruptions - Unpredictable disruptions like volcanic eruptions or hurricanes.
Resistance - How much a disruption can affect ecosystem energy and matter flows. High resistance means the ecosystem maintains function despite disturbance.
Resilience - The rate an ecosystem returns to its original state after disruption. High resilience means quick recovery.
Intermediate disturbance hypothesis - Ecosystems with intermediate disturbance levels have higher species diversity than those with very high or low disturbance.
The hypothesis works because: - Low disturbance: Competitive species dominate and outcompete others - High disturbance: Only fast-reproducing, hardy species survive - Intermediate disturbance: Balance allows both competitive and resilient species to coexist
Example: New England marine algae with periwinkle snails. Few snails = competitive algae dominate. Many snails = only unpalatable algae survive. Intermediate snail density = 12 algae species coexist.
Causes: Ice ages trap water in ice sheets (lowering levels), warming periods melt ice (raising levels). Driven by Earth’s orbital changes.
Impacts: During last Ice Age, levels dropped 120+ meters. After warming, rose 85+ meters. Coastal areas repeatedly switched between land and marine ecosystems.
Why: Animals follow seasonal food availability and suitable habitats.
Example: Serengeti migration - millions of wildebeest, zebras, and gazelles migrate in circular patterns following seasonal rains. They move to areas where rains create fresh vegetation, returning when original areas recover.
Evolution - A change in the genetic composition of a population over time.
Microevolution - Evolution at the population level (e.g., different varieties of apples).
Macroevolution - Evolution that gives rise to new species, genera, families, classes, or phyla.
Artificial selection - Humans determine which individuals breed based on desired traits.
Natural selection - The environment determines which individuals survive and reproduce.
Fitness - An individual’s ability to survive and reproduce.
Adaptation - A trait that improves an individual’s fitness.
Allopatric speciation - Speciation that occurs with geographic isolation.
Sympatric speciation - Evolution of one species into two without geographic isolation.
Natural Selection Requirements: - Individuals produce excess offspring - Not all offspring survive - Individuals differ in traits - Traits can be passed to offspring - Trait differences affect survival/reproduction
Random Processes: - Gene flow - Individuals move between populations, altering genetic composition - Genetic drift - Random mating changes genetic composition (more likely in small populations) - Bottleneck effect - Population reduction decreases genetic variation - Founder effect - Small colonizing group creates genetically distinct population
Slow evolution: Cichlid fish evolved ~200 species over millions of years in Lake Tanganyika
Rapid evolution: Atlantic cod evolved smaller size and earlier maturity after decades of fishing pressure targeting large individuals
Very rapid evolution: Genetically modified organisms (GMOs) can gain new traits instantly through gene insertion
Ecological succession - Predictable species replacement over time.
Primary succession - Begins with bare rock, no soil. Secondary succession - Begins with soil intact.
Pioneer species - Survive with little/no soil. Keystone species - Low abundance, large community effects.
Indicator species - Demonstrate ecosystem characteristics.
Primary: Pioneer species (lichens, mosses) → soil formation → grasses → trees
Secondary: Disturbance leaves soil → rapid recolonization → early trees → shade-tolerant trees
Species richness: Increases then plateaus
Biomass: Increases and plateaus
Productivity: Increases then declines (mature forests =
low productivity, high standing crop)
Keystone: Beavers (create ponds), sea stars (control mussels), flying foxes (pollinate plants)
Indicator: Mayflies (clean water), E. coli (sewage contamination), lichens (air quality)
Population growth rate (intrinsic growth rate): Number of offspring produced minus deaths in a given time period.
Biotic potential: Maximum population growth under ideal conditions with unlimited resources.
K-selected species: Species with low growth rates that increase slowly to carrying capacity.
Carrying capacity: Maximum number of individuals an environment can support (denoted as K).
Overshoot: Population exceeding carrying capacity.
Dieback: Rapid population decline due to death.
Generalists: Live under wide range of conditions, broad diets, adaptable to change (gray kangaroos)
Specialists: Narrow conditions/diets, vulnerable to environmental change (koalas eating only eucalyptus)
r-selected species because they reproduce rapidly, produce many offspring, and can quickly exploit new environments.
Type I: High survival until old age (K-selected: elephants, humans)
Type II: Constant death rate throughout life (chipmunks, squirrels)
Type III: High early death, survivors live long (r-selected: fish, frogs)
Trapping data show cyclical oscillations: hare populations peak first, followed by lynx 1–2 years later. As hares overconsume vegetation, their numbers crash, causing lynx to decline from lack of prey. Reduced predation then allows hares to rebound—repeating the cycle.
When resources like food or nesting sites decline:
Example: Logging reduces nesting cavities for goldeneye ducks, lowering their population even if food is plentiful.
Population size = (Immigrations + births) - (emigrations + deaths)
%Change = New - Original / Original x 100%
Immigration: The movement of people into a country or region from another country or region.
Emigration: The movement of people out of a country or region.
Crude Birth Rate (CBR): The number of births per 1,000 individuals per year.
Crude Death Rate (CDR): The number of deaths per 1,000 individuals per year.
Age Structure Diagram: A visual representation of the number of individuals within specific age groups for a country, typically expressed separately for males and females, with each horizontal bar representing a 5-year age group.
Total Fertility Rate (TFR): An estimate of the average number of children that each woman in a population will bear throughout her childbearing years (typically ages 15-49).
Replacement-Level Fertility: The total fertility rate required to offset the average number of deaths in a population in order to maintain the current population size, assuming there is no net migration.
Global Population Growth Rate:
Global population growth rate (%) = [CBR - CDR] / 10
Where: - CBR = Crude birth rate (births per 1,000 people per year) - CDR = Crude death rate (deaths per 1,000 people per year) - Divided by 10 to convert from per 1,000 to percentage
National Population Percent Growth Rate:
National population % growth rate = [(CBR + immigration) - (CDR + emigration)] / 10
Where: - CBR = Crude birth rate (births per 1,000 people per year) - Immigration = number of people moving into the country (per 1,000 people per year) - CDR = Crude death rate (deaths per 1,000 people per year) - Emigration = number of people moving out of the country (per 1,000 people per year) - Divided by 10 to convert from per 1,000 to percentage
TFR is typically lower in developed countries for several reasons. Women tend to delay having their first child due to pursuing education and employment opportunities, which reduces their childbearing years. Higher income levels correlate inversely with TFR. Additionally, developed countries provide better access to family planning services and birth control information, allowing women greater control over reproduction.
Declining population: TFR below replacement level
No growth (stable) population: TFR at replacement level
Growing population: TFR above replacement level
Calculation of replacement-level fertility for a no-growth country:
In developed countries, replacement-level fertility is typically about two children per woman plus a small amount extra. This calculation is based on:
In developing countries, replacement-level fertility is higher because infant and child mortality rates are higher, meaning more births are needed to ensure enough individuals survive to reproductive age to maintain the population.
The key assumption is that there is no net migration (immigration equals emigration). If net migration is positive, a country can maintain or grow its population even with a TFR below replacement level.
Doubling time: The number of years it takes a population to double in size.
Rule of 70: A method to determine doubling time by dividing 70 by the percentage population growth rate. - Formula: Doubling time (years) = 70 / growth rate (%)
Theory of demographic transition: A theory stating that countries move from high to lower birth and death rates as they transition from preindustrial to industrialized economic systems.
Characteristics: - Preindustrial period with high infant mortality - Large families provide economic benefits (labor) - Poor sanitation and lack of healthcare
CBR and CDR: Both HIGH and EQUAL (no growth)
Characteristics: - Modernization begins with better sanitation and healthcare - Death rates drop but families still have many children - Population momentum occurs
CBR and CDR: CBR HIGH, CDR DROPS (rapid growth)
Characteristics: - Improved economy and education - Increased affluence and birth control access - Smaller families become preferred
CBR and CDR: Both DECREASE toward equality (slowing growth)
Characteristics: - High affluence and development - Aging population with fewer workers - Increased elderly care costs
CBR and CDR: CBR BELOW CDR (both LOW, population declines)
Plate tectonics: The theory that the lithosphere of Earth is divided into plates, most of which are in constant motion.
Earthquake: A sudden movement of Earth’s crust caused by a release of potential energy from the movement of tectonic plates.
Hot spots: Places where molten material from Earth’s mantle reaches the lithosphere.
Volcano: A vent in the surface of Earth that emits ash, gases, or molten lava.
Tsunami: A series of waves in the ocean caused by seismic activity or an undersea volcano that causes a massive displacement of water.
Divergent boundary: An area below the ocean where tectonic plates move away from each other.
Seafloor spreading: Rising magma forms new oceanic crust on the seafloor at divergent boundaries.
Convergent boundary: An area where one plate moves toward another plate and collides.
Subduction: The process in which the edge of an oceanic plate moves downward beneath the continental plate.
Island arcs: A chain of islands formed by volcanoes as a result of two tectonic plates coming together and experiencing subduction.
Transform boundary: An area where tectonic plates move sideways past each other.
Fault: A fracture in rock caused by a movement of Earth’s crust.
Plate tectonics impacts biodiversity through continental movement, which changes climates and creates or removes geographic barriers.
Example: Australia and Antarctica split apart and moved to different climatic regions. This separation led to allopatric speciation, where isolated species evolved along different paths. Species had to adapt to new climates or face extinction, with some evolving into entirely new species due to geographic isolation.
Physical weathering: The mechanical breakdown of rocks and minerals.
Chemical weathering: The breakdown of rocks and minerals by chemical reactions or dissolving of chemical elements from rocks.
Acid rain (acid precipitation): Precipitation high in sulfuric acid and nitric acid.
Erosion: The physical removal of rock fragments from a landscape or ecosystem.
Porosity: The size of the air spaces between particles.
Water holding capacity: The amount of water a soil can hold against the draining force of gravity.
Permeability: The ability of water to move through the soil.
┌─────────────────────────────────────────────────────────┐
│ O HORIZON (Organic Layer) │
│ Organic detritus in various stages of decomposition. │
│ Humus (fully decomposed matter) in lowest section. │
├─────────────────────────────────────────────────────────┤
│ A HORIZON (Topsoil) │
│ Organic material (including humus) mixed with minerals. │
├─────────────────────────────────────────────────────────┤
│ E HORIZON (Zone of Leaching) │
│ Iron, aluminum, and dissolved acids removed. Found in │
│ some acidic soils. Not present in all soils. │
├─────────────────────────────────────────────────────────┤
│ B HORIZON (Subsoil) │
│ Primarily mineral material with very little organic │
│ matter. Nutrients accumulate here. │
├─────────────────────────────────────────────────────────┤
│ C HORIZON (Parent Material Layer) │
│ Least-weathered horizon, similar to parent material. │
└─────────────────────────────────────────────────────────┘Note: Most soils have either an O or A horizon, usually not both.
Sandy Loam ranges: - Sand: approximately 50-70% - Silt: approximately 15-30% - Clay: approximately 0-20%
Sandy loam is dominated by sand with moderate silt and low clay content, creating well-draining soil that retains some moisture and nutrients.
Albedo: Percentage of incoming sunlight reflected from a surface. Snow/ice (80-95%) vs. forests (10-20%).
Saturation Point: Maximum water vapor air can hold at a given temperature. When temperature drops, water condenses → precipitation.
Hadley Cells: Convection currents between equator and 30°N/30°S. Warm air rises at equator → precipitation. Cool, dry air sinks at 30° → deserts.
Intertropical Convergence Zone (ITCZ): Latitude with most intense sunlight where Hadley cells converge. Shifts 23.5°N to 23.5°S yearly, creating tropical wet/dry seasons.
Polar Cells: Air rises at 60°N/60°S (precipitation), sinks at poles (90°N/90°S), returns to 60°.
Ferrell Cells: Convection currents between 30° and 60° latitudes. Driven by Hadley and polar cells. Creates variable mid-latitude winds.
Coriolis Effect: Deflection of moving objects due to Earth’s rotation. Creates prevailing wind patterns by deflecting air currents east or west.
EXOSPHERE (600-10,000 km) | 0-1,700°C | Satellites orbit here
THERMOSPHERE (85-600 km) | up to 2,000°C | Blocks X-rays/UV | Auroras
MESOSPHERE (50-85 km) | 0 to -90°C | Meteors burn up here
STRATOSPHERE (16-50 km) | -60 to 0°C | OZONE LAYER (O₃)
| Absorbs UV-B and UV-C
TROPOSPHERE (0-16 km) | -52°C to warmest | DENSEST layer
| Weather occurs here
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EARTH'S SURFACE2A[AGas Composition: Nitrogen (78%) + Oxygen (21%) + Other gases (1%) - Greenhouse gases (CO₂, CH₄, N₂O) = small amount but warm Earth by 33°C - Density and pressure decrease with altitude
NORTH POLE (90°N)
↓ sinking
POLAR CELL → Polar Easterlies
↓
60°N ← rising
↓
FERRELL CELL → Westerlies
↓
30°N ← sinking
↓
HADLEY CELL → NE Trade Winds
↓
EQUATOR ← rising (ITCZ)
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EQUATOR ← rising (ITCZ)
↑
HADLEY CELL → SE Trade Winds
↑
30°S ← sinking
↑
FERRELL CELL → Westerlies
↑
60°S ← rising
↑
POLAR CELL → Polar Easterlies
↑ sinking
SOUTH POLE (90°S)Earth rotates once every 24 hours → day/night cycle
Cause: Earth’s axis tilted 23.5° + orbit around Sun - Hemisphere tilted toward Sun = summer (direct rays, long days) - Hemisphere tilted away = winter (oblique rays, short days)
June Solstice (Jun 20-21)
N. Hemisphere Summer
☀️
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Sept Equinox ------🌍------ March Equinox
(Sep 22-23) (orbit) (Mar 20-21)
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December Solstice (Dec 21-22)
S. Hemisphere SummerSolar radiation → convection currents → Coriolis effect → prevailing winds → climate patterns → biome locations
Earth’s tilt creates seasons and shifts the ITCZ, determining where and when precipitation falls globally.
Watershed: All the land in an area that drains into a particular stream, river, lake, or wetland.
Description: The total land surface that drains water into the watershed’s outlet (can range from a few hectares to thousands).
Effect on Water Amount: 1. Larger areas collect more total precipitation 2. More water is channeled to the outlet 3. Example: Mississippi River drains nearly one-third of the U.S.
Description: Distance along the main water flow from beginning to outlet.
Effect on Water Amount: 1. Greater length increases travel time to outlet 2. Affects timing and concentration of water flow 3. Works with area to determine total water volume
Description: The steepness of land within the watershed.
Effect on Water Amount: 1. Gentle slopes: water moves slowly, more infiltration, less runoff, minimal erosion 2. Steep slopes: water moves fast, less infiltration, more runoff, substantial erosion and sediment
Description: Composition of soil particles (sand, silt, clay).
Effect on Water Amount: 1. Sandy soils: highly permeable, water infiltrates rapidly, less surface runoff 2. Clay soils: less permeable, more surface runoff, carries sediment easily
Description: Plants and root systems present in the watershed.
Effect on Water Amount: 1. With vegetation: roots hold soil, increase infiltration, reduce runoff, absorb nutrients 2. Without vegetation: increased erosion, more runoff, more sediment loss
Gyre: A large-scale pattern of water circulation that moves clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere.
Upwelling: The upward movement of ocean water toward the surface as a result of diverging currents.
Thermohaline circulation: An oceanic circulation pattern that drives the mixing of surface water and deep water.
Rain shadow: A region with dry conditions found on the leeward side of a mountain range as a result of humid winds from the ocean causing precipitation on the windward side.
El Niño–Southern Oscillation (ENSO): A reversal of wind and water currents in the South Pacific.
La Niña: Following an El Niño event, trade winds in the South Pacific reverse strongly, causing regions that were hot and dry to become cooler and wetter.
Direction: - Northern Hemisphere: Clockwise rotation - Southern Hemisphere: Counterclockwise rotation
Climate Effects: - Cold currents along west coasts → cooler temperatures (California Current) - Warm currents along east coasts → warmer temperatures (Gulf Stream)
Where: Along west coasts of continents
Process: Surface currents diverge → deeper water rises to replace it
Importance: - Brings nutrients from ocean bottom - Supports large phytoplankton populations → large fish populations - Critical for commercial fisheries
Process: 1. Gulf Stream carries warm water to cold North Atlantic 2. Evaporation and freezing leave salt behind → cold, salty water 3. Dense water sinks to ocean bottom 4. Deep current moves past Antarctica → northern Pacific 5. Water rises and returns to Gulf of Mexico (takes hundreds of years)
Climate Impact: England is 20°C (36°F) warmer in winter than Newfoundland (similar latitude) due to Gulf Stream
Climate Change Concern: Glacier melting → less salty North Atlantic → water won’t sink → could shut down circulation → much colder western Europe
Windward side (facing wind): - Humid ocean air rises up mountain - Adiabatic cooling → condensation - Heavy precipitation falls - Lush vegetation
Leeward side (away from wind): - Dry air descends mountain - Adiabatic heating - Warm, dry conditions → desert
Frequency: Every 3 to 7 years
What Happens: 1. Trade winds weaken or reverse 2. Warm water moves eastward toward South America 3. Suppresses upwelling off Peru coast 4. Lasts weeks to years
Global Impacts: - Reduced upwelling → fish populations crash - Southeastern U.S.: Cooler and wetter - Northern U.S., Canada, southern Africa, Southeast Asia: Unusually dry - Crop failures and food shortages - 2015-2016 ENSO: ~100 million people faced food shortages
Timing: Follows El Niño event
What Happens: Trade winds reverse back stronger than normal
Effects: Opposite of El Niño - hot/dry regions become cool/wet
Cycle: After La Niña, climate returns to normal for several years
Effect of soil compactness on the total gross growth of Brassica rapa