Please enable JavaScript.
Coggle requires JavaScript to display documents.
Population and Community Ecology - Coggle Diagram
Population and Community Ecology
Population Ecology
Population Characteristics
Definition: group of individuals of the same species in an area
Key features
Dispersion - clumped, uniform, random
Size - total individuals
Density - number per unit area
Demographics
Age structure diagrams
Fecundity and mortality patterns
Example: clumped dispersion in schools of fish increases protection
Population Growth Models
Exponential Growth
Ideal conditions - r is constant
J-shaped curve
Example: invasive species early in colonization
Logistic Growth
S-shaped curve
When N is large, growth slows
Carrying capacity (K) limits growth
Assumptions/Limitations
No immigration/emigration
Constant birth/death rates
Life Histories
Definition: traits that affect an organism’s schedule of reproduction and survival
r-selection
Many offspring, low survival
Example: insects
Unstable environments
K-selection
Few offspring, high parental care
Example: elephants
Stable environments
Trade-offs
Reproduction vs. survival
Semelparity vs. iteroparity
Population Dynamics
Influences on size fluctuations
Resources
Disease
Predation
Density-dependent factors
Competition, disease, territoriality
Density-independent factors
Natural disasters, climate events
Human impact
Habitat fragmentation - isolated populations
Interactions in Communities
Species Interactions
Competition
Resource partitioning
– / – interaction
Competitive exclusion principle
Predation
– interaction
Adaptations: fangs, claws, camouflage
Herbivory
Plant defenses: toxins, spines
Parasitism / Mutualism / Commensalism
mutualism - bees and flowers
parasitism - ticks
Ecological Niches
Realized niche
Actual conditions due to competition
Niche differentiation
Reduces overlap - coexisting
Fundamental niche
All possible conditions species can occupy
Example: Anolis lizards dividing tree microhabitats
Trophic Structure
Food webs
Realistic network of interactions
Trophic levels
Primary, secondary, tertiary consumers
Food chains
Linear energy flow
Primary producers to consumers to predators
Keystone species
Disproportionate impact (sea stars, wolves)
Community Structure and Diversity
Disturbance and Succession
Disturbance
Fire, storms, logging
Intermediate disturbance hypothesis
Primary succession
No soil - pioneer species (lichens, mosses)
Secondary succession
Soil remains - faster recovery
Climax community
Stable, long-term state
Biogeography and Community Patterns
Latitudinal gradients
Richness highest at equator
Area effects
More space - more niches
Island Biogeography
Larger islands = more species
Closer islands = higher immigration
Immigration vs. extinction rates
Example: Galapagos finch communities differ by island size
Species Diversity
Components
Species richness - # of species
Species evenness - relative abundance
Shannon diversity index
Measures community complexity
Influences
Disturbance, climate, geography
Example: tropical rainforests = high diversity
Community Stability and Energy Flow
Energy Flow in Communities
Limits to productivity
Nutrients, light, temperature
Trophic efficiency
10% rule: energy lost
Primary production
GPP - total energy made by producers
Biomass pyramids
Represent amount of energy at each level
Trophic Cascades
Definition:Top-down effects where predators shape community
Example: wolves - regulate elk - restore vegetation
Indirect interactions
Effects ripple across trophic levels
Mesopredator release
Loss of apex predators leads to explosion of mid-level predators
Community Stability
Resilience
Ability to recover after disturbance
Role of diversity
More species - more stable communities
Resistance
Ability to remain unchanged during disturbance
Ecosystem engineers
Modify environment (beavers)