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“Ecology Beyond Populations: Communities & Ecosystems” - Coggle Diagram
“Ecology Beyond Populations: Communities & Ecosystems”
Ecology
Levels of Ecological Organization
Ecosystem – A community plus its physical environment (biotic + abiotic factors)
Biome – Large regions characterized by similar climate, plants, and animals
Community – All the populations of different species living and interacting in the same area
Biosphere – The global sum of all ecosystems; all life on Earth and the environments where life exists.
Population – A group of individuals of the same species living in a specific area
Population Characteristics
Demographics: Statistical study of population structure (age, sex ratio, birth/death rates).
Population Growth
Population Size Formula:
N=(births+immigration)−(deaths+emigration)N = (births + immigration) - (deaths + emigration)N=(births+immigration)−(deaths+emigration)
Growth Rate (r):
r > 0 → population grows
r < 0 → population declines
r = 0 → stable
Types of Growth
Exponential Growth: J-shaped curve, occurs in ideal conditions.
Example: Bacteria in lab culture.
Logistic Growth: S-shaped curve, includes carrying capacity (K).
Example: Deer population in forest.
Overshoot & Crash:
Example: Daphnia population overshoots K, then crashes.
Factors Affecting Growth
Density-dependent regulation
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Examples:
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Density-independent regulation
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Dispersion Patterns (how individuals are spaced):
Clumped: Individuals aggregate in patches due to resources or social behavio
Example: Wolves in packs, mussels on rocks.
Uniform: Even spacing due to territoriality or competition.
Example: Penguins nesting, desert shrubs.
Random: No predictable pattern; resources evenly distributed.
Example: Dandelions, tropical trees
Survivorship Curves:
Type I: High survival early, most die old
(humans, elephants)
Type II: Constant death rate
(birds, rodents).
Type III: High mortality early
(oysters, fish)
Population Dynamics
Fluctuations in population size over time and space due to biotic and abiotic factors.
Piping plover populations fluctuate with habitat changes.
Moose and wolves on Isle Royale: Moose colonized ~1900, wolves arrived ~1950; both fluctuate due to food availability and climate.
Interactions
Fish population changes affect seabirds that eat fish
Organism – A single individual living thing
Immigration, Emigration, and Metapopulations
Immigration: Movement into a population.
Emigration: Movement out of a population.
Metapopulation: Group of spatially separated populations connected by migration.
Example: Butterfly populations in fragmented habitats.
Life History Strategies
Semelparous: Reproduce once, then die
(salmon, agave).
Iteroparous: Multiple reproductive events
(humans, elephants).
r-selected species
: Many offspring, little care (insects, weeds).
K-selected species
Few offspring, high care (elephants, whales).
The Global Human Population
Population Explosion: Began during Industrial Revolution (medicine, agriculture).
Regional Patterns of Change
Developed nations: Slow growth or decline.
Developing nations: Rapid growth.
Age Structure:
Pyramid shape → rapid growth (developing countries).
Column shape → stable (developed countries).
Global Carrying Capacity: Debate on Earth’s K for humans.
Ecological Footprint:
U.S.: ~8 hectares/person.
Developing nations: ~1-2 hectares/person.
Types of Ecology
Population vs Community Ecology
Population Ecology: Examines one species’ population size, density, growth, and dynamics.
Example: Moose population on Isle Royale.
Community Ecology: Examines interactions among species and their effects on diversity and stability.
Example: Wolves, moose, and plants on Isle Royale.
Biological Diversity
Definition: Variety of species, genes, and ecosystems.
Benefits: Stability, resilience, productivity.
Potential Harm: Invasive species increasing diversity but destabilizing ecosystem.
High diversity: More niches, better resource use, disease resistance.
Ecological Niche/interactions
Definition: The sum of a species’ use of biotic and abiotic resources in its environment.
Includes habitat, food, behavior, and ecological role.
Fundamental Niche: Full range of conditions a species could occupy without competition.
Realized Niche: Actual conditions occupied due to competition and interactions.
Example: Warblers feed in different tree zones → realized niche smaller than fundamental niche.
Your niche: Humans use diverse resources, modify environments, and occupy multiple roles.
Defensive Strategies
Mechanical defenses: Spines, shells (porcupine, turtle).
Chemical defenses: Toxins (poison dart frog).
Aposematic coloration: Warning colors (bright frogs).
Cryptic coloration: Camouflage (leaf insect).
Batesian mimicry: Harmless mimics harmful (viceroy butterfly mimics monarch).
Müllerian mimicry: Two harmful species mimic each other (bees and wasps).
Predator mimicry: Predators mimic prey attractants (anglerfish lure).
Food Chains vs Food Webs
Food Chain: Linear energy flow (grass → rabbit → fox).
Trophic Levels:
Producers → Primary consumers → Secondary → Tertiary → Decomposers.
Energy Transfer: ~10% passed to next level; 90% lost as heat.
Implication: Plant-based diets more energy-efficient than meat-based.
More energy required for tertiary consumers → explains why top predators are rare.
Food Web: Complex network of chains; more realistic.
Top-Down vs Bottom-Up Controls
Top-Down: Predators control prey populations.
Example: Wolves reduce deer numbers.
Bottom-Up: Nutrient availability controls producers → affects higher levels.
Example: Fertilizer increases plant growth → more herbivores.
Species Roles
Dominant species: Most abundant or biomass (trees in forest).
Keystone species: Strong impact despite low abundance (wolves in Yellowstone).
Ecosystem engineers: Modify environment (beavers build dams).
Invasive species: Non-native, disrupt ecosystems (zebra mussels).
Introduced species: Non-native, may or may not be harmful (trout in Colorado streams).
Endangered species: At risk of extinction (manatees).
Threatened species: Likely to become endangered (polar bears).
Ecological Succession
Definition: Gradual change in species composition over time.
Primary Succession: Occurs on bare rock (volcanic island).
Secondary Succession: Occurs after disturbance (forest fire).
Does it stop? No, communities keep changing.
Climax community: Stable end stage (though dynamic)
Competitive Exclusion Principle(there can only be one)
definition: Two species competing for the same limiting resource cannot coexist indefinitely.
Why? One species outcompetes the other → local extinction or niche shift.
Evolutionary Link: Drives resource partitioning and character displacement (traits diverge to reduce competition).
Resource Partitioning
Definition: Division of resources to reduce competition.
Example: Warbler species feed in different parts of trees.
Human Examples:
Gangs Like the Movie
Different crops in separate fields.
Time-sharing of fishing zones.
Urban resource use (restaurants, markets).
If resources become scarce: Increased competition → possible exclusion or adaptation.
Symbiosis (Species Interactions)
Predation: One species kills/eats another.
Example: Wolves eat moose; herbivory = deer eating plants.
Herbivoration One species eats plants
Cows Eat Grass
Parasitism: Parasite benefits, host harmed.
Ectoparasite: Lives on host (ticks).
Endoparasite: Lives inside host (tapeworm).
Mutualism: Both benefit.
Example: Bees pollinate flowers.
Commensalism: One benefits, other unaffected.
Example: Barnacles on whales.
Facilitation: One species benefits another without direct contact.
Example: Plants improving soil for other species.
Ecosystem Management
Preservation: Protect nature from use.
Conservation: Sustainable use of resources.
Wildlife Management: Regulate populations for human benefit.
Example: Controlled burns in forests (post-1960 policy).
Pre-1960s: Fire suppression → unnatural buildup of fuel.
Today: Prescribed burns maintain ecosystem health.
Biogeochemical Cycles
Water Cycle: Evaporation, precipitation, transpiration.
Carbon Cycle: Photosynthesis, respiration, fossil fuels.
Nitrogen Cycle: Fixation by bacteria, nitrification, denitrification.
Phosphorus Cycle: Weathering of rocks, uptake by plants.
Largest Reservoirs:
Water: Oceans.
Carbon: Sedimentary rocks.
Nitrogen: Atmosphere.
Phosphorus: Rocks.
Human impacts:
Burning fossil fuels → CO₂ increase.
Fertilizers → nitrogen/phosphorus runoff → eutrophication.