Population Ecology 1 & 2 Flashcards
Describe a population
- Group of individuals of a single species living in same general area
- Populations are described by their boundaries and size
What are the 5 Ds of population ecology?
- Density
- Distribution
- Dispersion (pattern of spacing)
- Dispersal (av distance an individual moves from where it was born to where it reproduces)
- Demographics
what factors influence spacing of individuals ?
- Environmental and social factors
Describe demographics
- Demographics: the statistical study of the structure of a population &
the changes that occur over time. - Incorporates:
- birth rates & death rates
- age structure
- sex ratios
What is Semelparity?
Single event (ollowed by death)
What is Iteroparity? what two types?
Repeated reproductive events =>
Seasonal iteroparity: e.g. birds, perennial plants
Continuous iteroparity: e.g. primates, tropical species
Population diagrams - how do they look when population is growing?
pyramid
Describe a mark-recapture survey
a method of population estimation in which
researchers capture and mark a subset of a
population from an area, return it to the area,
and capture a second sample of the population
after time has passed.
How is population size estimated:
What two life tables can we have?
Age specific summary of survival pattern of a population =>
1. Cohort Life Tables - follows an age group from birth to death
2. Time specific (static) - quantifies survival`::fecundity of ALL individuals at one time interval
What important stats for life history?
- age
- No alive each year
- survival
-Deaths - Mortality rate
- Mean expectation of further lfie at age x
What are the patterns of survivorship: intermediate types?
Type II/III intermediate
- High young mortality
* - then constant adult mortality rate
(e.g. many birds, mud turtles)
Type I/II intermediate
- Low mortality in young,
* - then steady adult mortality rate
Use of population models?
help understand complex real ecological
systems in simple terms.
- Test theories, enables predictions to be made & help in decision making for managing & conserving populations of species
why is it helpful to study population growth ?
in an idealized situation to help us
understand the capacity of species to increase and the conditions that
may facilitate this growth.
Population dynamics modelling?
Express mathematically population growth ?
How can births and deaths be expressedN
as an average number of births and deaths PER INDIVIDUAL during the specified time interval
What is the per capita rat of increase aka intrinsic growth rate?
(R) = b-m
r=0?
zero population growth
r>0 ?
population increases
r<0 = ?
population decrease
How can we now write the change in population size?
When does exponential population growth happen?
under idealized conditions
What is the equation for exponential population growth?
think of N as money in bank account and r as interest
When would we realistically see exponential population growth in nature?
populations introduced to new area
what would a more realistic population model growth?
incoportating carrying capacity (K)
What is carrying capacity?
s the maximum population size the environment can
support. K varies with the abundance of limiting resources
What is the logistic model ?
describes how a population grows more slowly as it nears its caryring capacity (K)
what happens in density-dependent limitations?
Birth rates fall and death rates rise with population density
(i.e. factors that affect population size in relation to the population’s density)
What happens in density-independent limitations?
Birth rate and death rate do not change with population density
(i.e. factors that limit population size regardless of the population’s density)
What are some density dependent factors?
- Competition
- Disease
- Predation
- Territoriality
- Intrinsic factors
- Toxic wastes @
Describe competition (density dependent factor)?
- Interspecific = between species
- Intraspecific= within species
- As population density inc, resources dec
Describe disease (density dependent factor)?
- As population inc, dx inc
- Population density can influence health and surviva or organisms
- In dense populations, pathogens can spread more rapidly
Describe Predation (density dependent factor) ?
- As population density inc, predation inc
- Peregrine falcon: nuthatcha/blackbird
- Cats, dogs : direct & inirect impacts on wildlife
Territoriality (density dependent factor)?
- As population density inc, territories dec
- In many vertebrates and some intervertebrates, competition for territory may lilit density
Describe Intrinsic factors (density dependent factor)?
- As population density inc, intrinsic factors inc
- For some populations, intrinsic (physiological) factors appear to regulate population size?
eg. stress, aggression
Describe Toxic wastes (density dependent factor) ?
- As population density inc , toxic waste inc
- Accumulation of toxic wastes, can contribute to density-dependent regulation of population size
Describe density independent factors?
- chance events or external factors
- Weather (cold wet winter, dought)
- Seeds finding fertile soil
Goal of reprod strategies?
Trade of bW quantity and quality (survival) of offspring
Describe K -selection (density-dependent selection (DD))
- Lives in more stable environment.
- Selects for offspring that have a higher
probability of survival to maturity – greater quality
r-selection (density-independent selection (DI
- Lives in unstable and unpredictable environments
- Selects for life history traits that maximize
reproduction (per capita rate of increase)
Table of r-selected & K selected reprod strategies?
