Chapter 51 Flashcards
Steps of Mark-recapture method
1) catch individuals and mark them
2) Release marked animals and allow them to mix well with the unmarked ones in the population
3) Catch individuals again - the percentage of marked individuals that were recaptured is recorded
4) solve equation (marked/? total = marked recaptured/second capture total)
What are the assumptions of the mark-recapture method
-Individuals are not moving in and out of the study area
-individuals mix between captures
-No bias exists regarding which individuals are caught in each recapture
-individuals do not learn to avoid or seek out traps after being caught once
-individuals do not change their behavior attract and or deter predators or mate or die from being handled
What 4 factors effect population size
birth, death, immigration, emigration
What is demography
the study of statistics which illustrate the changing structure of the human population
Things one needs to know to predict future size of popultion
- Age structure
-# of individuals of each age that are likely to survive to the following year
-# of offspring produced by females of each age
-how many individuals of different ages immigrate and emigrate each generation
-the average time between a mother’s first offspring and that of her daughter - generation length
What can you infer about population size if it consists of mostly young individuals with high survival and reproductive rates
should increase overtime
What can you infer about population size if it consists of mostly old individuals with low survival and reproductive rates
decline over time
What does a life table show
the probability that an individual will survive and reproduce in any given time interval over the course of its lifetime
What does age class refer to in a life table
individuals of a specific age
Survivorship
the proportion of offspring that survive, on average, to a particular age
Survivorship curve
a plot of the logarithm of the number of survivors versus age
Survivorship curve: Type 1
High survivor ship at young age, steep decline in old age
Survivorship curve: Type 2
Steady survivorship throughout lifetime
Survivorship curve: Type 3
Low survivorship at a young age but high survivorship through rest of life
Calculation of net reproductive rate
Net reproductive rate = Sum of all ages (survivorship at age x Fecundity at age)
Fecundity
the ability to produce an abundance of offspring
Life-History trade-offs
High fecundity, low survivorship vs low fecundity, high survivorship
-on a scale
Population growth
a population’s change in population size (deltaN) per unit time (deltat) is a function of birthrates, death rates, immigration rates and emigration rates
Per capita rate of increase
(r) is the difference between the birthrate and death rate per individual
Density-independent factors
usually abiotic factors which do not depend on the population size but change birth rates and death rates
-Ex: weather patterns
Density-dependent factors
Factors which depend on the population size and decrease fecundity or survivorship
-can be based on intraspecific and interspecific (predation, parasitism) interactions
Logistical growth
If a population of size N is below the carrying capacity K, the population can grow at a rate proportional to (K-N)/K
Carrying capacity
The upper limit of exponential growth, at which point population growth is switched to logistical growth patterns
Exponential growth equation
change in population size over time = births - deaths all multiplied by population size
