Topic 10: Population Growth and Regulation Flashcards
what is meant by r when calculating birth and death rates?
birth rate - death rate = r or the instantaneous rate of growth.
Define the exponential growth model and what are the assumptions for the exponential growth model?
the rate of population growth is directly proportional to population size and the intrinsic growth rate r.
assumptions of model:
1. that there is unlimited resources.
2. that the environment is constant and stable (no seasonality or variation or change of any kind).
What does it mean if:
r = 0
r > 0
r < 0
- birth rate = death rate
- birth rate is greater than death rate
- birth rate is less than death rate
How is the r-value influenced?
r-value is influenced by life history, such as the frequency of reproduction, number of individuals born and environmental conditions.
What type of organisms does the exponential growth model work best for?
works best for r-type organisms.
What happens when the population grows?
as the population grows interactions between individuals causes an increase in mortality and a decrease in birth rate.
What is (1- N/K)?
(1- N/K) is a correction factor added to the exponential growth model.
What happens to (1- N/K) as the population increases in size?
as population increases in size and comes closer to carrying capacity the effect of the correction factor becomes stronger.
What is the assumption of the logistic growth model? What does it NOT assume?
1) constant/ stable environmental conditions.
does not assume infinite resources.
What kind of species does the logistic growth model work well with?
k-type species
What is meant by density independent factors?
typically includes changing environmental conditions beyond the optimal or even tolerance level for a species.
What does a life table do?
a life table quantifies mortality and survivability in different age classes within a population.
What assumptions do the life tables make?
1) the cohort will be representative of the larger population.
2) the environment is stable.
Define the variable: age class (years)
a given time interval after birth of the individuals (x).
Define the variable: cohort
a group of individuals born at the same time (n)
Define the variable: survivorship
the probability at birth of an individual surviving to any age (Ix)
Define the variable: age specific mortality
number of individuals from the cohort who have died during a time interval (dx).
Define the variable: mortality rate
the probability of death at any given age (qx)
There are 3 idealized types of survivorship curves. Name them and give an example of a species that follow that curve.
a) type 1 - very high initial survivability, very low initial mortality, indicative of k-type species. ex- reindeer, moose, elephant.
b) type 2 - no trend. survivorship and mortality is consistent over lifetime. ex- birds.
c) type 3 - very low initial survivability, very high initial mortality, indicative of r-type species. ex- insects, mice.
The estimation of birth rate involves 2 important factors. What are these factors?
a) in a sexually reproducing population, only females give birth
b) the birth rate w/n the female population will vary with age (some immature and others past age of fertility)
How do you determine net reproductive rate (R0)?
with birth rate (Bx) and survivorship (Ix).
When does competition occur?
competition occurs when individuals use a common resource that is in short supply relative to the numbers seeking to use it.
What is intraspecific VS interspecific competition?
intra - competition w/n the same species.
inter - competition b/w two species.
Intraspecific competition can be categorized into 4 categories; what are they?
a) scrambled competition: all individuals suffer a depression of growth and reproduction. (happens in herds)
b) contest competition: only some individuals suffer a depression of growth and reproduction.
c) exploitation: the presence of individuals leads to reduced availability of a resources with NO CONTACT.
d) interference: individuals interact DIRECTLY with each other preventing others from occupying a habitat or accessing resources within it.
