the study of populations and interactions with their environment
groups of organisms of the same species occupying a defined area at a specific time
Characteristics of populations (5)
# of births/individuals born/unit time
# deaths/ #individuals/year
Mortality rate is the number of individuals in a population dying during any given time interval divided by the number alive at the beggining of the time interval
distribution of numbers of individuals of various ages
ratio of number of males to number of females
# individuals/unit area
Birth Rate and immigration often,..
Mortality and emigration often...
Hos is birth rate often expressed?
number of offspring/female/year or per 100 females/year
What is the denisty dependent factor
factor that takes a varying % of the population depending on the density of the population (competition, predation, crowding, parasites, disease)
What is the density independent factor?
factor that takes a constant % of the population independent of pupulation density (climate and weather, shortage of resources-nest sites, den sites, etc, non infections diseases, pollution)
What is exponential population growth?
growth under no environmental resistance or limiting factors
competition and its effects of food, cover, space and water resources, predation (interspecific competition), disease, starvation, etc
What do we have to assume with exponential growth?
that there are no limits such as predation, diseases, etc
Characteristics of exponential growth
population grows at increasing rates
"j curve" depicts population growth at increasing rates
Does exponential growth last?
usually no, environment is not constant and resources are limited
birth rates will decline, death rates will increase, or both to even out once K is reached
Logistic population growth
biotic potential of the population is held in check or limited by environmental resistance
biotic potential is synonymous with reproductive potential, maimum rate of population increase under ideal conditions
In Logistic pop growth
environmental resistance dictates the carrying capacity of the area or habitat
there is an S curve graph
What is Carrying Capacity?
the number of animasl an area can support over a period of time without damage to that habitat
What are reproductive strategies
the more energy spent on reproduction, the less energy it can distribute for growth and maintenence
investment includes not only the production of offspring but also care and nourishment
species in different environments will differ in life history traits such as size, productivity, age at first reporduction, # of reproductive events during lifetime, and total life span
r and k selection
What is r seleciton?
selection under low population densities
favors high reproductive rates under conditions of low competition
fish, bugs, etc
What classifies an r strategist?
density independent mortality
variable pop size
short life span
high rate of increase
What is K selection?
selection under carrying capacity conditions and a high level of competition
What classifies a k strategist?
constant pop size
long life span (>1year)
reproduce less often
low rate of increase
clumped together populations
most common type of dispersion
ex: packs of wolves, elephants, etc
evenly spread out, very specific
random spacing and distribution
ex: flower pollen, tree seeds, etc
Population growth equation
N- number of individuals
ri- max growth rate, intrinsic growth rate
d- rate of change
b- birth rate
What are survivorship curves? what different kinds?
survivorship curves are graphs showing the survival and reproduction of populations
Types 1,2, and 3
Type 1 survivorship curve?
like k selection
few offspring, but live long time
high mortality rate towards post reproduction years
Type 2 survivorship curve?
constant mortality rate throughout life
Type 3 survivorship curve?
like r selection
many offspring, but many die close to birth
few lucky ones survive a longer time
high mortality rate at pre reproduction years
Reproduces once before death
reproduce ofthen througought life
how do limited resources and trade offs affect life histories?
limited resources can cause the pop to decrease and the fit survive and trade offs have organisms with low survival rate produce many offspring for a chance and organisms with a higher survival rate produce fewer organisms