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Population Ecology and Community Ecology - Coggle Diagram
Population Ecology and Community Ecology
Chapter 53: Population Ecology
Introduction
Population ecology
Study of how populations interact with the environment
Focuses on population size, density, dispersion, and demographics
Population
Group of individuals of the same species living in the same area
Main ideas
Population growth
Carrying capacity
Life history
Population regulation
Human population trends
53.1 Biotic and abiotic factors affect population density, dispersion, and demographics
Population density
Number of individuals per unit area or volume
Changes through
Births
Deaths
Immigration
Emigration
Dispersion
Clumped
Most common
Resources unevenly distributed
Social behavior
Uniform
Even spacing
Often caused by territoriality
Random
No strong attraction or repulsion among individuals
Demographics
Study of population factors affecting growth and decline
Includes
Age structure
Sex ratio
Birth rate
Death rate
Life tables
Summarize survival patterns
Survivorship curves
Type I
Low mortality until old age
Example
Humans
Type II
Constant mortality across lifespan
Example
Some birds
Type III
High early mortality
Example
Many plants and fish
53.2 The exponential model describes population growth in an idealized, unlimited environment
Exponential growth
Occurs when resources are unlimited
Population grows rapidly
Per capita rate of increase
r = birth rate - death rate
Equation
dN/dt = rN
Characteristics
J-shaped curve
Growth accelerates as population size increases
Importance
Shows maximum potential for reproduction under ideal conditions
53.3 The logistic model describes how a population grows more slowly as it nears its carrying capacity
Logistic growth
Growth slows as population approaches carrying capacity
Carrying capacity
K = maximum population size the environment can sustain
Equation
dN/dt = rN((K-N)/K)
Characteristics
S-shaped curve
Rapid growth early
Slower growth near K
Why growth slows
Limited food
Limited space
Competition
Disease
Waste buildup
53.4 Life history traits are products of natural selection
Life history
Pattern of growth, reproduction, and survival
Life history traits
Age at first reproduction
How often reproduction occurs
Number of offspring
Amount of parental care
Trade-offs
Energy used for one function cannot be used for another
Example
Many small offspring vs few well-provisioned offspring
Semelparity
One major reproductive episode
Iteroparity
Repeated reproductive episodes
Natural selection
Shapes life history traits that maximize fitness
53.5 Density-dependent factors regulate population growth
Density-dependent factors
Effects increase as population density rises
Examples
Competition for food
Territoriality
Disease
Predation
Waste accumulation
Density-independent factors
Affect populations regardless of density
Examples
Fire
Storms
Drought
Extreme temperatures
Population regulation
Often caused by interaction of both density-dependent and density-independent factors
Population cycles
Some populations show repeating rises and declines
Example
Snowshoe hare and lynx
53.6 The human population is no longer growing exponentially but is still increasing rapidly
Human population growth
Slow for most of history
Rose sharply after agriculture and industrialization
Current trend
Still growing
But not at the peak exponential rate seen earlier
Age structure
Helps predict future growth
Regional differences
Some countries growing quickly
Some stable or declining
Ecological footprint
Measures environmental impact of human populations
Concerns
Resource use
Pollution
Habitat destruction
Climate change
Sustainability
Chapter 53 Key Concepts
Population size changes through
Birth
Death
Immigration
Emigration
Growth models
Exponential = unlimited resources
Logistic = limited resources and carrying capacity
Life history traits
Products of natural selection
Population growth
Regulated by environmental factors
Chapter 54: Community Ecology
Introduction
Community ecology
Study of interactions among species in a community
Community
All organisms living in a given area
Main ideas
Species interactions
Diversity
Trophic structure
Disturbance
Biogeography
Pathogens
54.1 Interactions between species can help, harm, or have no effect on the individuals involved
Species interactions
Competition
/ -
Both species harmed
Predation
/ -
Predator benefits, prey harmed
Herbivory
/ -
Animal eats plant or algae
Parasitism
/ -
Parasite benefits, host harmed
Mutualism
/ +
Both species benefit
Commensalism
/ 0
One benefits, other unaffected
Competition
Can reduce population sizes
Can shape niches
Competitive exclusion
Two species using the same limiting resource cannot coexist indefinitely
Resource partitioning
Species divide resource use to reduce competition
Coevolution
Reciprocal evolutionary change in interacting species
54.2 Diversity and trophic structure characterize biological communities
Species diversity
Species richness
Number of species
Relative abundance
How common each species is
Trophic structure
Feeding relationships in a community
Trophic levels
Primary producers
Primary consumers
Secondary consumers
Tertiary consumers
Detritivores and decomposers
Food chains
Simple linear feeding paths
Food webs
Network of feeding interactions
Dominant species
Most abundant or highest biomass
Strong effect on community
Keystone species
Disproportionately large impact relative to abundance
Ecosystem engineers
Modify the physical environment
Example
Beavers
Invasive species
Non-native species that spread and alter community structure
54.3 Disturbance influences species diversity and composition
Disturbance
Event that changes community structure
Examples
Fire
Flood
Storm
Human activity
Effects
Removes organisms
Changes access to resources
Opens habitat for colonization
Nonequilibrium model
Communities are often shaped by ongoing disturbance
Intermediate disturbance hypothesis
Moderate disturbance may produce highest diversity
Succession
Ordered sequence of community change
Primary succession
Starts where no soil exists
Example
New lava
Glacial retreat
Secondary succession
Starts where soil remains
Example
After fire
After farming
54.4 Biogeographic factors affect community diversity
Biogeography
Study of species distribution across space and time
Latitudinal gradient
Diversity tends to be higher in the tropics
Species-area relationship
Larger areas usually contain more species
Island biogeography
Species richness depends on
Island size
Distance from mainland
Immigration and extinction
Together determine island species number
Habitat fragmentation
Breaks habitats into isolated patches
Can lower biodiversity
54.5 Pathogens alter community structure locally and globally
Pathogens
Disease-causing organisms
Effects on communities
Reduce abundance of hosts
Shift species interactions
Alter food webs
Local effects
Disease outbreaks can change community composition
Global effects
Introduced pathogens can devastate species with little resistance
Examples
Chestnut blight
Chytrid fungus in amphibians
Human influence
Global travel and transport spread pathogens more easily
Chapter 54 Key Concepts
Communities are shaped by
Species interactions
Diversity
Trophic structure
Disturbance
Biogeography
Pathogens
Important ecological ideas
Competitive exclusion
Resource partitioning
Keystone species
Succession
Island biogeography
Connections Between Chapters 53 and 54
Ecology scale
Population ecology
Focuses on one species
Community ecology
Focuses on interactions among species
Common factors affecting both
Resource availability
Competition
Predation
Disease
Disturbance
Climate
Growth and regulation
Population size influences community interactions
Community structure can influence population growth
Evolutionary connections
Natural selection shapes life history traits
Species interactions can drive coevolution
Big picture themes
Environmental limits
Carrying capacity
Species interactions
Diversity and stability
Human impact on ecological systems