7.13. (10/9) Population Structure and Distribution Flashcards
What are subpopulations?
some amount of geographic barrier between them
where do populations exist?
heterogeneous (different) landscapes
what does population mean?
individuals of the same species living in a particular area
What does subpopulation isolation depend on?
distances between, nature of intervening environment, mobility of the species
what is a metapopulation?
a group of subpopulations that are separated but rely on the exchange of individuals (genetic flow)
What is the mark and recapture method?
go into a system, collect individuals, mark them, release them, come back later, and count how many you recollected that were marked vs not marked
*can be done without actually capturing and marking species because of the special markings found on the animal (photographic)
How do you compute with mark-recapture?
initial sample with M number of marked individuals, recaptured sample the size of n, containing x marked individuals, population size N
N = nM/x
What assumptions are made with the mark-recapture method?
- equal probability of capture
- no birth/immigration increase
- marked and unmarked individuals are dying and emigrating at the same rate
- no markings were erased or lost
What is the relationship between species size and density?
density declines with increasing size
What trend do plants demonstrate when it comes to size and density?
they range in size during their life causing density to change accordingly
In what ways do populations constantly change?
numbers of individuals, age distribution, sex ratio, death and birth rate
What are life tables?
they track number of surviving individuals and number of individuals that die
What is a cohort table? What are some advantages and disadvantages of this method?
- tracking a small group of organisms from birth until they die
- all cohort individuals must be marked
- most reliable
- some organisms live longer than humans
What is a static life table? What are some advantages and disadvantages of this method?
- determining the age at death of a large number of individuals
- you see a picture
- must be able to estimate age upon death
- less reliable
- individuals belong to different cohorts
- easier to do
What is age distribution? What are some advantages and disadvantages of this method?
- how many are alive at different age levels
- looks at the current population structure
- must precisely gage individuals
- constructed with current data
- examines total population
- can be displayed as an age pyramid
- must be able to age individuals accurately
- don’t have to wait for birth or death
how are survivors plotted per 1000 births?
on a log scale
what does a type I survivorship curve look like?
juveniles don’t die easily, but death increases with age
* humans
What is a type II survivorship curve?
linear, constant probability of dying no matter how old you are
*good determinate: if offspring and adults are the same size
*some birds and turtles
What is a type III survivorship curve?
high mortality at a young age but once past a certain age the chances of dying are low
*fish, sea turtles, octopus
What does the age distribution of a population reflect?
- history of survival
- reproduction
- potential for future growth
What does an abundance of young individuals suggest?
the population is increasing
What does an equal amount ages in a population mean?
stable
What does an absence of young individuals suggest?
the population is declining
What does knowing the age structure of a population provide?
- if a population is growing, stable, or declining
- historical periods of high or low birth/death rates
What is climate space?
combination of climate variables where a species occurs
what is geographic range?
distribution of species
how does the physical environment limit the geographic distribution of species?
- species cannot tolerate the full range of earth’s environments
- energy usage is limited for organisms
- energy cost of adapting to environmental variation is too much sometimes
Apart from biological/biotic and physical factors, what else affects distribution?
competition
What scale does competition affect? Climate? What is the spatial-dependent distribution like?
- competition at the small spatial scale
- climate at the geographic scale
- distribution is scale-dependent (space matters)
- factors that control geographic range are different than the factors controlling distribution in a region/finer scale
What is dispersion?
- where individuals are relative to each other at a small spatial scale
- individuals within a population describes their spacing with respect to one another
What is the clumped pattern?
individuals can be found in clumps
What is the evenly spaced pattern?
individuals maintain a minimum distance from others
* if we know the location of one individual we can predict the location of every other individual
What is the random pattern?
- not relatively spaced to the other
- individuals distributed independently of others within a homogeneous area
- equal probability of occurring anywhere
What causes different dispersions?
- social interactions
- structure of the physical environment
- distribution of resources
What causes the even spacing pattern?
- competition for limited resources
- territorial
- direct interactions
- maintenance of minimum distance
What causes the random pattern?
when there are neutral interactions between the individuals and their local environment
*less heterogeneity of resources across space
What causes the clumped pattern?
-social predisposition
- clumped distribution of resources
- progeny not able to disperse far or don’t have that tendency
What causes different dispersion patterns?
social interactions within population, structure of physical environment
Why is the creosote bush unique in terms of distribution?
their distribution changes over time
- clumped at a young age (safe sites)
- after some time competition becomes fierce, so distribution becomes random as they die
- at adulthood: higher mortality when close to neighbors causing a more even distribution
- compete for water at the roots (4%)
Aspens
- large clones
- connected underground
- send up shoots
