Chapter 4: Populations and Communities Flashcards
Population
Members of the same species that live in the same area
Community
Different species that all live in the same area
Population growth
A change in populaion size
Equilibrium
(births + immigration) = (deaths + emigration)
Population Growth Rate
Amount the population has changed divided by the time it had to change
Exponential Growth
Growth at a constant rate of increase
Population Explosion
Results from exponential growth
J-curve
the curve of exponential growth
Logistic Growth
Some process slows growth so it levels off near carrying capacity
Carrying Capacity (K)
the maximum population of a species a habitat can support without being ruined
S-curve
Results from logistic growth
Biotic potential
The number of offspring produced under ideal conditions
Environmental Resistance
The biotic and abiotic factors that limit a population’s increase
K-strategists
Lower biotic potential
- care for and protect young
- live in stable environment
- larger, longer lived, well-adapted to normal environmental fluctuations
- populations fluctuate around carrying capacity
- equilibrian species
R-strategists
Produce lots of young, but leave their survival to nature
- low recruitment
- rapid reproduction/movement/life span
- adapted to changing environment
- “boom-and-bust”
3 Survivorship curves
Type 1 Survivorship: low mortality in early life
Type 2 Survivorship: Intermediate survivorship pattern
Type 3 Survivorship: many offspring that die young
Population Density
Number of individuals per area
Density-Dependent Factor
Increases with increased population density
Density-Independent Factor
Its effects are independent of the density of the population
Top-Down Regulation
Control of a population
Bottom-Up Regulaion
Control of a population occurs as a result of scarcity of a resource
Critical Number
the minimum population base allowing the survival and recovery of a population
Threatened Species
populations are declining rapidly
Endangered Species
Populations are near critical number
Predator
The organism that does the feeding
Prey
the organism that is fed upon
Parasite
An organism that feeds on its “prey,” usually without killing it
Host
The organism that is being fed upon
Herbivory
Eating plants
Keystone Species
Play a crucial role in maintaining ecosystem biotic structure
Intraspecific Competition
Competition between members of the same species for resources
Territory
An area defended by an individual or group
Territoriality
Reduces intraspecific fighting, which ensures adequate resources for some
Interspecific competition
Fighting between different species in the same area
Competitive Exclusion Principle
Species can’t survive if they compete directly in many respects
Resource Partitioning
The dividion of a resource and specialization in different parts of it
Mutualism
Both species benefit
Commensalism
one species benefits but the other is unaffected
Amensalism
One species is harmed while the other in unaffected
Symbiosis
A relationship between two organisms
Selective Pressures
Environmental resistance factors that affect survival and reproduction
Natural Selection
The process of specific traits favoring survival of certain individuals
Biological Evolution
Modification of the gene pool of a species by natural selection over generations
Fitness
An individual’s average contribution to the gene pool of the next generation
Reproduction Isolation
The original populations separate into two populations
Plate Tectonics
Populations becaome isolated through the slow movement of Earth’s continents
Tectonic Plates
Huge slabs of rock in the Earth’s crust that float on an elastic layer beneath them
