Population Ecology Flashcards
Things you should know (3)
- How density, dispersion and demographics can
describe a population. - The differences between exponential and
logistical models of population growth. - How density-dependent and density-idenpendent
factors can control population growth.
Levels of Complexity (5)
Individual
Population
Community
Ecosystem
Biosphere
Group of individuals of same species in same area at same time.
Often described by their boundaries and size
Population
Rely on same resources
Interact
Interbreed
Population
Study the factors that cause population to increase and decrease (3)
Input Immigration & Births
>
Population Size
> Output Emigration & Deaths
Why population Ecology? (2)
Scientific goal: understanding the factors that influences the size of populations
Practical goal: management of populations
Under scientific goal of population ecology (2)
General principles
Specific cases
Under practical goal of population ecology (3)
Increase population size (endangered species)
Decrease population size (pests)
Maintain population size (fisheries management)
Factors that affect Population size (3)
Abiotic factors
Biotic factors (behavior/interactions): other livign organisms
Intrinsic factors (adaptations)
Abiotic factors
Sunlight and Temperature
Precipitation and water
Soil and Nutrients
Biotic factors
Prey (food)
Competitiors
Predators, Parasites, Disease
Characterize Population: Range
Geographical Limitations
Abiotic and biotic factors
Habitat
Characterize Population: Density
Add: immigration, births.
Remove: emigration, deaths.
Sampling techniques more common: mark and recapture
Rare: count all individuals. Difficult to count a moving target.
Number of individuals per unit area of volume
Density
The number of individuals that live in a defined area.
Is a measurement of the number of individuals living in a defined space.
Population Density
Population density formula
of individuals / area (units^2) = population density
Regulation of Population Size
Density Dependent:
Competition (food, mates, nesting sites)
Predators, parasites, pathogens.
Density Independent:
abiotic factors
Characterize Population: Dispersion (3)
Clumped Pattern (most common)
Uniform (rare)
Random
Spacing among individuals within the boundaries of the popultion
Provides insight into the environmental associations and social interactions of individuals in population.
Dispersion
Individuals are aggregated in clumps. Why? (3)
Microenvironment satisfies organism’s requirements
May be associated with mating behavior
May increase effectiveness of predation (wolves)
May result from direct interactions between individuals in the population (ex. territoriality)
Uniform
The position of each individual is independent of other individuals. (ex. dandelion seeds dispersal)
Random
Population growth patterns (2)
Changes in a population’s size are determined by immigration, births, emigration, and deaths.
Population growth is based on available resources.
Factors that affect the size of a population (4)
Immigration
Births
Emigration
Deaths
Is a rapid population increase due to an abundance of resources.
Exponential growth
Population growth models (2)
Exponential growth model
Logistic growth model
Growth rate formula
Growth rate = number of offspring - deaths
Under ideal conditions (with unilimited resources) each species has a particular:
the max for that species
intrinsic growth rate
Model calculates the maximum rate and displays it as a ___ (because there are no limits)
J-shaped curve
Includes environmental limits on the population growth
Logistic growth model
As the population reaches the ___, the growth slows and then stops.
carrying capacity
The logistic growth model produces a ___
S-shaped curve
Some populations cycle above and below the carrying capacity - this is ___ followed by ___
overshoot, die-off
___ (K): Number of individuals in a population that the environmental resources can support
Carrying capacity
When population reaches carrying capacity, growth rate is zero (N=K, r= 0)
Zero population growth (ZPG): when r = 0
Exponential (___)
Logistic (___)
Un-restricted
Restricted
is due to a population facing limited resources
Logistic growth
A ___ is a dramatic decline in the size of a population over a short period of time.
Population crash
____ limit population growth
Ecological factors
A ___ is something that keeps the size of a population down.
Limiting factor
___ limiting factors are affected by the number of individuals in given area
Density-dependent
(predation
competition
parasitism and disease)
____ limiting factors limit a population’s growth regardless of the density.
Density-independent
(Unusual weather
Natural disasters
Human activity)
Reproductive strategies (2)
K-selected
R-Selected
Late reproduction
Few offspring
Invests a lot in raising offspring
K-selected
(ex. Primates, walnut trees)
Early reproduction
Many offspring
Little parental care
r-selected
(ex. Insects, many plants)
Study of the vital statistics of populations and how they change over time.
Demography
Age specific summaries of the survival pattern of a population.
Life tables
(ex. Belding ground squirrels - Spermophilus beldingi)
Graphic representation of life table
Survivorship curve
In survivorship curves, relatively straight lines of the plots indicate ___ rates of death
relatively constant
3 types of survivorship curves generalized strategies
Type 1. High death rate in post-reproductive years (large mammals, humans)
Type 2. Constant mortality rate throughout life span (lizards, invertebrates, annual plants)
Type 3. Very high early mortality but the few survivors then live long/stay reproductive (long-lived plants, oysters)
Relative number of individuals of each age
Age structure
Factors affecting population growth rate (3)
Sex ratio
Generation time
Age structure
Characteristics of K-selected species
Large
Later maturing
Few offspring
Substantial parental care
