What are the 2 processes that can increase population size?
Immigration and birth
What are the 2 processes that can decrease population size?
Death and emigration
Which of these are relevant at the local scale?
birth, immigration, death, and emigration
which are relevant at the global scale?
Birth and death
What does it mean if r (populatin growth rate) is positive, negative, or 0?(b-d)+ (i-e);
if it is stable it will be zero, if it is increasing: positive, if it is decreasing: negative
Population starts with 10,000 people and has 200 births per years and 200 deaths
-calculate b,d, and r
-is the population inreasing or decreasing?
b=200/10000= 0.02 or 2%
d= 100/10000= 0.01 or 1% per year
r= (200-100) 100/10000= 0.01 or 1%per year
-population is increasing
In nature, populations rarely grow exponentially (j-shaped growth). Logistical (S-shaped) is more commonly observed. why?
J: unrealistic bc of resources
S: at first it grows slow, but then you hit critical point where there are enough individuals where growth becomes very fast but then growth rate slows down because you hit points where resources are being utilized. Stablize
What is K, the environmental carrying capacity?
plateau of where the rate of growth levels off. environmental carrying capcity is not a characteristic of each species it's a characteristic of the environment. different environments have different amounts of resources. Max number of organisms that can b
What are factors that determine the environmental carrying capacity (K)?
food
How can you increase the environmental carrying capacity for a population of an endangered species?
migration, agriculture, medicine, and communication
How can you decresae the environmental carrying capacity for a population of an invasive species?
introduce predators. encourage hunting (death). Neutering (birth). research on how invasive species is entering area and make efforts to create barriers
Human population has been increasing exponentially. What were some of the milestones that promoted faster population growth and may have increased our environmental carrying capacity?
The 1700s: new sources of energy- industrial revolution, manufacturing methods.
-then fossil fuels
then agriculture green revolution: synthetic fertilizers. then widespread production of antibiotics: advances in medicine
What is currently happening with global raets of birth, death, and populatin growth for humans?
increased birth rates and decreased rates. Longer lifespan
What are some factors that determine environmental carrying capacity for humans?
start growing more food in same space. start producing more than previously with same number ofowrkers.
-technology has influenced environemntal carrying capacity for humans.
-in part it is a social construct: standard of living, consumption, resource pro
What is demography?
the study of how human populations change in size (growth rates) and in structure (sex and age distribution)
Population growth rate (R) formula
(b-d)+ (i-e)
Changes occurring in local popualtion size
increase: Birth and immigration
Decrease: Death and emmigration
Changes in global population size
increase: birth
decrease: death
How are b,d,i,e and r expressed
percent per year
-proportion of the population that is born,dies,immigrates into or emmigrates out of the population each year
carrying capacity
the maximum number of individuals from a species that an environment can support at a given time
-it can change over time
yearly growth rates globally are...
declining
projections for 2050 on population size
birth rates are decreasing
but death rates are decreasing faster
r is decreasing, but still positive
r will reach zero by end of this century
Estimates of human carrying capacity (K)
4-16 billion ppl (vary drastically)
what factors influence the environmental carrying capacity for humans?
standard of living
consumption
resource production
technology
waste generation