Chapter 11: Population Growth and Regulation Flashcards
Four Processes that influence populations
birth, death, immigration, and emigration
Population increases by a constant proportion
geometric growth and exponential growth
Geometric Growth
organisms reproduce in synchrony at discrete time periods
-the number of individuals added is larder with each time period, and the population grows larger by ever-increasing amounts
-results in a j-shaped set of points
Exponential Growth
organisms reproduce continuously over time
-results in a j shaped curve
Go look at slides 18 and 19 in Chapter 11
Doubling Time
number of years it will take a population to double in size
How do populations increase (addition or multiplication)?
multiplication
What type of factors change population size and growth rate over time?
-density independent factors and density dependent factors
Density-Independent Factors
-their effects on population size or growth rate are independent of the numbers of the individuals in the population
-weather conditions, catastrophes, climate change
Density-Dependent Factors
-their effects are dependent on the number of individuals in the population
-amount of resources such as food or habitat influence population size
How does gradual climate change impact populations
-increasing mortality rates in western coniferous forests over several decades is related to regional warming
-higher temps have led to less snowpack, earlier spring melt, and longer dry summers
-caused an increase in the tree’s climactic water deficit (amount by which a plant’s annual evaporative demand for water exceeds available water)
As population density increases…
birth rates often decrease, death rates increase, and dispersal (emigration) increases, all decrease population size
Population Regulation
density-dependent factors cause population to increase when density is low and decrease when density is high
Do density-independent factors regulate population size?
NO. Only density-dependent factors can regulate
Logistic Growth
population increases rapidly, then stabilizes at carrying capacity
What causes growth rate to slow as a population reaches carrying capacity?
resources begin to run short
What is the growth rate of a population at carrying capacity?
growth rate is zero
Who derived the logistic equation and predicted carrying capacity for the US population?
Pearl and Reed (1920)
Ecological Footprint
the total area required to support a human population
Life Table
summary of how survival and reproductive rates vary with age, size, or life stage of individuals
How are life tables used?
to predict future population trends and develop strategies for managing populations
Age Class
members of a population whose ages fall within a specified range
Age Structure
proportion of a population in each age class; influences whether population will increase or decrease in size
How does age structure affect population?
-if there are man people of reproductive age, it will grow rapidly
-a population with many older, it will grow slowly
-rapidly growing human populations have a greater percentage of people in younger age classes
Type I Survivorship Curves
most individuals survive to old age
Type II Survivorship Curve
chance of surviving remains constant throughout the lifetime
Type III Survivorship Curves
high death rates for young; those that reach adulthood survive well (species that produce a lot of offspring)
Survivorship curves can vary:
-among populations of a species
-between males and females
-among cohorts that experience different environmental conditions. The edicts of those conditions on populations can be assessed
Cohort Life Table
follows the fate of a group of individuals all born at the same time (cohort)
What are cohort life tables mostly used for?
mostly used for sessile organisms. organisms that are highly mobile or have long life spans are difficult to track
Look at slide 58-60 on Chapter 11
Generation Time
average age of parents of all offspring produced by the cohort
Static Life Table
survival and reproduction of individuals of different ages during a single time period
What are static life tables used for?
mobile organisms or ones with long life spans’ requires age estimation
Method to manage populations
identify the age-specific birth or death rates that most strongly influence population growth rate
