Populations
1. 7 Billion –Videos
2. 7 Billion – Agree or Disagree
3. Intro to Populations - Notes
http://www.youtube.com/watch?v=s
c4HxPxNrZ0
https://www.youtube.com/watch?v=4B2xO
vKFFz4
https://www.youtube.com/
watch?v=VcSX4ytEfcE
Understanding Populations
Population: all the members
of a species living in the
same place at the same time.
3 words to describe a population:
1. Size – (7 billion people on the planet)
2. Density – (people per square mile)
3. Dispersion – (distribution or
arrangement of its individuals within a
given amount of space)
Even
 Clumped
 Random

Density
Dispersion
How Does a Population Grow?
 Growth rate: change in the size of a
population over a given period of time.
 Positive (+): birth rate > death rate
 Zero (0): birth rate = death rate
 Negative (-) = birth rate < death rate
Change in
population
size
=
Births
-
Deaths
How Fast Can a Population Grow?
 Reproductive potential: the maximum
number of offspring that a given organism
can produce.
 Examples:
 It would take elephants 750 years to produce 19 million
descendents
 It would take bacteria a few days to produce 19 million
descendents.
 What is another organism with a low reproductive rate?
How Fast Can a Population Grow?
 High reproductive potential when individuals…
 Produce more offspring at a time
 Reproduce more often
 Reproduce early in life
 Examples:
 Insects – can reproduce when they are a few hours or days
old
 Humans – reproduce after a number of years
How Fast Can a Population Grow?
 Exponential Growth: when populations grow
faster and faster
 Occurs when a population has:
 Plenty of food and space
 No competition or
predators
What Limits Population Growth?
Carrying Capacity: the largest
population that an environment can
support in any given time
What Limits Population Growth?
Limiting resources: a natural
resource that is consumed at the
same rate at which the ecosystem
produces the resource
 Example:
Limiting Factors
 Food
 Water
 Sunlight (producers)
 Space
 Disease
 Competition
 Predation
Two Types of Population Regulation
Density Dependent
Density Independent
 Same species close
 Portion of a
together
 Disease spreads
from one to the
next
 Death occurs
quickly
population dies
regardless of
population density
 Example: Natural
disasters
(hurricane)
If humans have no natural
predators, how is our population
controlled?
Human Carrying Capacity?
 Current human population: approx 7.12
billion people
 Ranges estimated from 4-16 billion people
 Hard to estimate how many people this
world can hold
 Technological innovations
 Medical breakthroughs
 http://www.census.gov/popclock/
What caused this
rapid growth?
What sparked our growth?
 Industrial Revolution (~1750)
 Modern medicine (20th century)
Death rates DROPPED due to better
care
 Agricultural Advances
 Transportation Advances
Human Population Growth
Population (in
billions)
1
2
3
4
5
6
7
8
9
Year
1804
1927
1960
1974
1987
1999
2012
2027
2046
Years elapsed
between
milestones
--
123
33
14
13
12
13
16
19
Source: U.S. Census Bureau-World POPclock Projection
What takes us out?
Pair and Share (2 min):
Humans are at the top of any food web resulting
in no natural predators to keep our populations
in check…
1. What are the limiting factors of the human
population?
2. How are we different than other species in
regards to population control?
What’s our limiting factor?
 Disease: Bubonic Plague, AIDS, Flu,
Malaria
 Access to food
 Access to clean water
 Competition (a.k.a. War)
Event
Casualties
American War Deaths, all-time
600,000
India Famine (1769-70)
3,000,000
AIDS deaths in 2011
1,700,000
Influenza Epidemic (1918)
21,000,000
Indonesian Tsunami/Earthquake (2004)
230,000
Bubonic Plague (1347-51)
75,000,000
Populations Review
1. What is growth rate?
2. What is reproductive potential?
1. High reproductive potential?
2. Low reproductive potential?
3. What are the two reasons that cause a
population to have exponential growth?
4. What is carrying capacity?
5. What is an example of a limiting factor?
How Many People Can Live on Planet Earth?
http://www.youtube.com/watch?v=d
N06tLRE4WE
Human population growth
Water
Food