Population
Population Biology and
Human Population
Essential Question: How many
people can sustainably live on Earth?
Objectives
Students will:
• Apply the power of exponential growth to
population problems
• Perform calculations involving doubling of
populations (rule of 70)
• Draw a J and S curve and explain the difference
between them
• Describe environmental resistance and discuss how
it can lead to logistic growth
Objectives, continued
• Define and calculate: fertility rate, birth rate, life
expectancy, death rate, population density, and
survivorship
• Compare and contrast density-dependent and
density independent events
• Explain the results of habitat fragmentation
• Explain how genetic drift, founder effect, and
bottleneck effect impact populations
Dynamics
• Exponential growth:
Unlimited resources and
lack of predators results in
unrestricted increase in a
population size
• Biotic potential of a
population is growth that
would occur in absence of
interfering factors
• Such organisms are
generalists: quantity of
individuals ensures survival
of some
Classic J-curve
World Population Doubling
Time Change
First doubling:
1 – 2 billion
Second doubling: 2 – 4 billion
Third doubling: 2.5 – 5 billion
Fourth doubling: 3 – 6 billion
What is happening to doubling time?
_________ years
_________ years
_________ years
_________ years
Population doubling
• Exponential growth results in doubling of the population.
• Example: The human population doubled from 2.5 billion
to 5 billion between 1950 and 1990 – 40 years
• 70 ÷ r = Doubling time, where r is the percentage growth rate.
This is called the RULE OF 70. (It comes from the natural
log of 2, which is .70)
• Apply the rule: If the world population doubled in 40
years, what was the growth rate between 1950-1990?
• Use: Doubling time is used by countries to predict the need
for resources and infrastructure and to aid in planning.
Limits
• Carrying capacity – maximum number of
individuals an ecosystem can support
• Some species naturally limit their population growth
when resources are limited
• Logistic growth curve – appears as an S, illustrates
population size limited by resource availability
• Other species experience oscillating cycles of
growth and decline
J-curve
Oscillation curves
Predator and prey
populations often
oscillate. Think
about it.
Host and parasite
populations oscillate
in a similar manner.
Be familiar with this
concept.
Overshoot / Crash
Some species overreproduce which can
lead to a population
crash – case study
St. Matthew Island
Reproductive Strategies
r and K strategists
- K strategists
- r strategists
Factors that change population
• Nutrition, climate, soil, water are required
• Fecundity: the ability to reproduce
• Natality: production of new individuals
• Total Fertility Rate: measure of offspring produced in an
average female’s life time
• Crude Birth Rate: number of births / thousand
individuals
• Life expectancy: the number of years an individual is
expected to live
• Life span: the longest period of time an organism reaches
Factors that change population
• Population density: number of individuals per square mile
or kilometer
• Mortality rate: death rate of a population
• Crude Death Rate: number of deaths / thousand
• Immigration: population growth by individuals coming in
• Emigration: population decrease by individuals exiting
• Migration: movement of populations
• Replacement Rate: the number of offspring required for a
couple to replace themselves (accounts for deaths)
Factors that regulate
population
DENSITY INDEPENDENT
• Abiotic factors
• Natural disasters, weather, climate change over time
DENSITY DEPENDENT
• Biotic factors
• Predator-prey, territoriality
• Stress, crowding, disease
Conservation Biology
• What is Conservation Biology? A multidisciplinary science that
has developed to address the loss of biological diversity.
• Why should we be concerned about conserving
biodiversity? For the first time in Earth’s history, a single
species, Homo sapiens, could cause a mass extinction. The main
cause of loss of biodiversity is loss of habitat caused by human
activities.
• What is Phytoremediation? The use of plants and soil bacteria
to reduce the concentrations of toxic chemical compounds in the
environment. Phytoremediation is widely accepted as a costeffective environmental restoration technology.
• Is it possible to restore rainforests?
• How to save endangered species
Demographic transition
• Theory of growth and change in population and its
characteristics as a result of industrialization
• 4 distinct phases
• Modeled with a graph in which you can see the
following three changes over time:
• birth rate
• death rate
• actual population
Demographic transition graph
Population on the Y axis, Time on the X axis.
Phase analysis
• Why are birth and death rates high in Phase I (Preindustrial)?
• Why does death rate plummet in Phase II (Early
Transitional)?
• Why does birth rate begin to decrease in Phase III
(Transitional)?
• Why does the population remain high in Phase IV
(Industrial) when birth and death rates are low?
• Is there a Phase V? What might it look like?
Phase analysis 1
Thanksgiving Population Project
Research one country’s demographics and report on:
1. Population
2. Birth rate
3. Death rate
13. State the
4. Infant mortality rate
Demographic Transition
5. Life expectancy
6. Growth rate 2013 / 1995
Phase your country is in.
7. Education levels
14. Cite evidence to
8. Primary Industries (1-3)
support your assertion.
9. Employment levels
10. Income per capita
11. Government Type
12. Key current events (1-3)
Rubric
• Information: concise, up to date, accurate, complete
• Illustrations: demographic transition, population
age structure diagram, photos showing life in your
country
• Audience: Presentation is professional, interesting,
compelling…. makes audience want to write an
award-winning screenplay with this country as a
setting…. (or visit, or join the Peace Corps)
Logistics
• FORMAT?
• Add a page to APESlahs2013.wordpress.com
• Poster
• Power point
• Where to get info?
• http://populationpyramid.net/
• https://www.cia.gov/library/publications/the-worldfactbook/
• How many students per presentation?
Due date: Monday, December 2
Email or text me with questions
Thanksgiving HW
• Define all terms in this ppt
• Population Math Problems B 1-5
• Read and summarize 3 articles on
Conservation Biology
• Population Project
• Meet Wednesday, November 27 from 10-noon
Resources
• http://www.worldometers.info/world-population/
• http://www.census.gov/popclock/
• http://worldof7billion.org/
• http://www.worldof7billion.org/index.php/student
_video_contest
• http://populationpyramid.net/
• https://www.cia.gov/library/publications/theworld-factbook/