Populations Flashcards
Population
A group of organisms of the same species that inhabit a defines geographical area at the same time
Population Density
The number of individuals in a population that inhabit a certain unit of land or water area
Population Dispersion
How individuals of a population are spaced within a region
Uniform: Members of a pop. are uniformly spaced throughout their geographic region. Often a result of competition for resources. ex. forests
Random: The position of each individual is not determined or influenced by the positions of others.
Clumped: Individuals flock together, many plants tend to grow in a habitat close to their parents and suit their requirements for life
Biotic potential
The amount that the population would grow if there were unlimited resources in its environment
The Carrying Capacity (K)
The maximum population size for the species that can sustainably be supported by the available resources in that environment
Exponential Population Growth J-curve
Resources are unlimited
Logistic Population Growth S-curve
A realistic model that portrays when populations are well below the size dictated by the K of the region they live in, they will grow exponentially but as they approach the K the resource base of the pop. shrinks relative to the pop. itself.
Overshoot
A population exceeds its carrying capacity
Environmental impacts: resource depletion
Leads to dieback of the pop. which is severe because the lack of available resources leads to famine, diseases, and/or conflict.
Once the dieback occurs, the population falls below carrying capacity K
Dieback
A population may recover
A population’s environmental carrying capacity is permanently lowered, the population recovers and becomes stable around the new carrying capacity
A population may be unable to recover from its dieback and go extinct
r-selected organisms
Pop. is below the carrying capacity
Competition is relatively low
These organisms tend to be small, have short lifespans, mature and reproduce early in life, and have many offspring at once (Reprod. once in a lifetime)
High capacity for reproductive growth
Little or no care is given to the offspring, but due to sheer numbers of offspring, enough will survive to enable the pop. to continue
r-selected organisms
Pop. is below the carrying capacity
Competition is relatively low
These organisms tend to be small, have short lifespans, mature and reproduce early in life, and have many offspring at once (Reprod. once in a lifetime)
High capacity for reproductive growth
Little or no care is given to the offspring, but due to sheer numbers of offspring, enough will survive to enable the pop. to continue
ex. bacteria, algae
invasive species
K-selected organisms
Population whose growth is limited by the carrying capacity of the environment
Live in stable environments where competition for resources is high
large and longer life spans
mature and reproduce later in life after years of parental care, produce fewer offspring, and more than once
devote significant time to parent-offspring
ex. humans, lions, cows
specialists
Boom-and-Bust Cycle
Common among r-strategist
A rapid increase in pop. then an equally rapid drop off
Changes may be linked to predictable cycles in the environment
When conditions good, they increase. When conditions bad, they decrease
Predatory-Prey Cycle
The predator population rises AFTER the prey population rises
Density Dependent Factors
influenced by the density of the pop.
ex. increased predation, competition, disease and buildup of toxic materials
