Properties of populations Flashcards
Organism
an individual life form; “individual” is a moving target
Population
size of a group in a given area; have to define individuals
Module
any number of distinct but interrelated parts
Stolons
specialized aboveground stem; runner that develops roots and aboveground clones
Rhizomes
specialized belowground stem
Suckers
plant roots that sprout new stems from the surface roots
Types of lateral modules
- stoloons
- rhizomes
- suckers
Genet
a plant produced sexual reproduction, arising from a zygote; genetic individual
Ramets
the clones; the genetically identical modules; referred to as clonal colonies
What are the two levels of population structure for modular organisms?
Genets and ramets
Hybridogenesis
produces hemiclones
hybrid individual originates from cross between two sexual species
then reproduces with parental species but doesn’t use the genome of parental species
Has only mothers genome
Parthenogenesis
reproduction without fertilization
The distribution of a population defines its
spatial location
Spatial location
describes a population’s geographic range
Ubiquitous
when a species is widespread
endemic
when a species is highly localized
Minimum convex polygons
assumes the smallest possible geographic range
hyperconservative
-underestimates geographic range
-does not take animal movement into account
Environmental heterogeneity typically brings about subdivisions in
populations
Subpopulations
local populations occupying suitable habitat within a larger landscape of unsuitable habitat
Metapopulation
a group of sub populations in a sourrce-sink dynamic
____ populations provide new individuals to other populations
source
____ populations are areas with limited breeding and few migrants
sink
Environmental heterogeneity
variation in the biotic and abiotic components of an ecosystem
What ultimately determines where an organism lives?
Two laws
- Liebig’s Law
- Shelford’s Law
Liebig’s Law
“law of the minimum”
- of all the biotic and abiotic variables, one or two have to be the most limiting
- a limiting factor is one in which minimal change brings about major shifts in population sizes
Shelford’s Law
“law of tolerance”
- organisms success is based on a complex set of conditions and that each organism has a certain minimum, maximum, and optimum for each environmental factor
- a low level of one factor can sometimes be compensated by high abundance of other factors
- factors act in combination rather than in isolation
abundance
defines population size
- the number of individuals in the population
- function of two facts: population density and area
Population density
number per unit area
Crude density
a measure of the total # of individuals per total area
_____ reflects population density and distribution
abundance
Clumped distribution
- most common
- species move in groups, herds, or packs
- dispersal is limiting
- seeds cannot travel very far, or plants are supported by “parental plants”
- resources are not evenly distributed so a population will only occur where resources are found
- may lead to high levels of competition or conflict
What is the benefit of the clumped distribution?
strength in numbers
Uniform distribution
- space between each individual is maximized
- most often found in plants that compete for soil moisture and nutrients
- when in animals, often the result of behavior conflict (territoriality)
- ex. fire ants
Random distribution
- uncommon occurrence
- a single individual’s position in an ecosystem is independent of the other members of the species
- pattern is characterized by lack of any strong social interactions between species
- ex. dandelion seeds
Ecological density
the number of individuals per unit of available living space
Quadrat sampling
a series of quadrats of a set size are placed in an ecosystem and the species are counted within them
-based on quadrat size, total population sizes can be estimated
Mark-recapture methods
- bassed on capturing individuals
- marking and releasing
- recapture
- for mobile species, subsampling can reveal larger trends
- common estimate: lincoln-peterson index
Measures of population structure include:
age, developmental stage, and sex
In general, populations can be divided into three distinct categories:
- pre-reproductive
- reproductive
- post-reproductive
Annual organism
completes entire life cycle in one year
The ___________ individuals will ultimately determine future population size
pre-reproductive
Why do sex ratios typically change with age?
Mammals/Birds
- males typically have shorter life spans
- rivalries, territoriality, sexual selection
- females are more likely to live to reproductive age but are more likely to die at/after reproduction
- death at delivery
- increased predation on nesting females
Dispersal
the movement of individuals in space
unidirectional
emmigration
movement out of an area
immigration
movement into an area
Migration
roundtrip movements
- typically revolves around breeding seasons and available resources
- repeated trips can be daily or seasonal
