Chp. 53 Population Ecology Flashcards
What does population ecology explore?
Explores how biotic and abiotic factors influence density, distribution, size, and age structure of populations.
What is a population?
Group of individuals of a single species living in the same general area
What 2 things describe a population?
- Boundaries
- Size
What is density?
The number of individuals per unit area or volume
What is dispersion?
Pattern of spacing among individuals within the boundaries of the population
What are the 3 sampling techniques that can be used to determine population size?
- Extrapolation from small samples
- Index of population size (ex. number of nests)
- Mark-recapture method
What are the steps of using the Mark-recapture method?
- Scientists capture, tag, and release a random sample of individuals (s) in a population
- Marked individuals are given time to mix back into the population
- Scientists capture a second sample of individuals (n), and note how many of them are marked (x)
- Population size (N) is estimated by N = sn/x
What is immigration?
Influx of new individuals from other areas
What is emigration?
Movement of individuals out of a population
What two things add individuals to a population?
- births
2, immigration
What two things will remove individuals from a population?
- Death
- Emigration
What two things does clumped dispersion depend on?
- resource availability
- behavior
What happens in a clumped dispersion?
Individuals aggregate in patches
What are the 3 patterns of dispersion?
- Clumped
- Uniform
- Random
What is territoriality?
Defense of a bounded space against other individuals
What happens in a random dispersion?
The position of each individual is independent of other individuals
What happens in uniform dispersion?
Individuals are evenly distributed
What is demography?
Study of the vital statistics of a population and how they change over time
What is a life-table?
A graphic way of representing the data in a life table.
What is a cohort?
A group of individuals of the same age
What is a survivorship curve?
Age-specific summary of the survival pattern of a population
What is type 1 survivorship curve?
Low death rates during early and middle life and an increase in death rates among older age groups
What is type 2 survivorship curve?
A constant death rate over the organism’s life span
What is type 3 survivorship curve?
High death rates for the young and a lower death rate for survivors
What is a reproductive table/fertility schedule?
An age-specific summary of the reproductive rates in a population
What does the exponential model describe?
Describes population growth in an idealized, unlimited environment
What is the formula of the change in population size?
Change in population size = births + immigrants - Death + emigrants
What is the population growth rate formula?
delta N /delta t = B - D
- delta N = change in population size
- delta t = time interval
*B = number of births, D = number of deaths
How to calculate birth?
B = bN
b = annual per capita birth rate, N = population size
How to calculate death rate?
D = mN
m = per capita death rate, N = population size
What is the zero population growth (ZPG)?
Occurs when the birth rate equals death rate
What is the exponential population growth?
Population increase under idealized conditions?
What type of curve does the exponential population growth result in?
J-shaped curve
What is the carrying capacity (K)?
The maximum population size the environment can support
What does the logistic population growth model show?
Shows that the per capita rate of increase declines as carrying capacity is reached
What does capital N refers to?
Population size
What does the lower case r refer to?
per capita rate of increase
What happens when N is small compared to K?
term (K–N)/K is close to 1 and the per capita rate of increase approaches the maximum
What happens when N is large compared to K?
term (K–N)/K is close to 0 and the per capita rate of increase is small
What happens when N equals to K?
Population stops growing
What happens when the N approaches K in a logistic growth model?
Population growth rate decreases
What shape does the logistic growth model show?
Sigmoid (s-shaped) curve
What is the Allee effect of a population?
Individuals have a more difficult time surviving or reproducing if the population size is too small
What does an organism’s life history comprise of?
Comprises of traits that affect its schedule of reproduction and survival
What are the 3 main variables of life history?
- The age at which reproduction begins
- How often the organism reproduces
- How many offspring are produced per reproductive episode
What is semelparity?
Big-bang reproduction, species reproduce once and die
What is iteroparity?
Repeated reproduction, species reproduce offspring repeatedly
Which environments prefer semelparity and iteroparity?
Semelparity: highly variable or unpredictable environments
Iteroparity: Dependable environments
What is K-selection?
Density-dependent selection, selects for life history traits that are sensitive to population density
What is r-selection?
Density-independent selection, selects for life history traits that maximize reproduction
What are the 2 general questions about regulation of population growth?
- What environmental factors stop a population from growing indefinitely?
- Why do some populations show radical fluctuations in size over time, while others remain stable?
What happens in density-independent populations?
Birth and death rate don’t change with population density
What happens in density-dependent populations?
Birth rates fall and death rates rise with population density
What kind of feedback are density-dependent birth and death rates
negative feedback
What happens in crowded populations?
Increasing population density intensifies competition for resources and results in a lower birth rate
What are the 6 mechanisms of density-dependent regulation?
- competition for resources
- disease
- predation
- territoriality
- intrinsic factors
- toxic wastes
What is the study of population dynamics?
Focuses on the complex interactions between biotic and abiotic factors that cause variation in population size
What is metapopulations?
Groups of populations linked by immigration and emigration
How to maintain population stability for humans?
Via zero population growth =
high birth rate - high death rate
or
low birth rate - low death rate
What is the demographic transition?
Move from the first state to the second state
What is age structure?
The relative number of individuals at each age
What is the ecological footprint concept?
Concept that summarize the aggregate land and water area needed to sustain the people of a nation
What does r(inst) refer to?
Refers to the instantaneous per capita rate of increase
