Chapter 53 Flashcards
Population Ecology
Explores how biotic and abiotic factors influence density, distribution, size, and age structure of populations
The number of loggerhead turtle hatchlings that survive their first journey to the ocean is affected by both _ and _ factors.
Biotic; abiotic
Population
A group of individuals of a single species living in the same general area
Populations are described by their _ and _.
Boundaries; size
Density
The number of individuals per unit area or volume
Dispersion
The pattern of spacing among individuals within the boundaries of the population
In most cases, it is _ to count all individuals in a population.
Impractical (or impossible)
_ can be used to estimate densities and total population sizes.
Sampling techniques
Population size can be estimated by either extrapolation from small samples, and index of population size (e.g., number of nests), or the _ method.
Mark-recapture
Determining population size 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
_ is the result of an interplay between processes that add individuals to a population and those that remove individuals.
Density
Immigration
The influx of new individuals from other areas (in)
Emigration
The movement of individuals out of a population (out)
Three patterns of dispersion:
- In a clumped dispersion, individuals aggregate in patches
- A uniform dispersion is one in which individuals are evenly distributed
- In a random dispersion, the position of each individual is independent of other individuals
Demography
The study of the vital statistics of a population and how they change over time (birth and death rates)
_ and _ are of particular interest to demographers.
Death rates; birth rates
Life Table
An age-specific summary of the survival pattern of a population
A life table best made by following the fate of a _, a group of individuals of the same age.
Cohort
Survivorship Curve
A graphic way of representing the data in a life table
Survivorship curves can be classified into three general types:
- Type I: Low death rates during early and middle life and an increase in death rates among older age groups (ex: humans and other high-level eukaryotes)
- Type II: A constant death rate over the organism’s life span (under constant threat of predation)
- Type III: High death rates for the young and a lower death rate for survivors (ex: sea turtles)
Many species are _ to the three types of survivorship curves.
Intermediate
The exponential model describes population growth in an idealized, _ environment.
Unlimited
The exponential model is useful to study population growth in an _ situation.
Idealized
Idealized situations help us understand the _ of species to increase and the conditions that may facilitate this growth.
Capacity
Change in population size =
Births + immigrants entering population - deaths - emigrants leaving population
If immigration and emigration are ignored, a population’s growth rate (r) equals _ minus _.
Birth rate; death rate
_ growth occurs when the birth rate equals the death rate.
Zero population
_ population growth is population increase under idealized conditions. Under these conditions, the rate of increase is at its maximum, denoted as _.
Exponential; rmax