Slide 1- Population GrowthWhen a population increases in size.
Slide 2Population Growth Question
Population A
2000 = 10 Cats
2010 = 12 Cats
2012 = 16 Cats
Population B
2000 = 20 Cats
2010 = 20 Cats
2012 = 20 Cats
Slide 3Another Population Growth Question
Population A
2000 = 10 Cats
2010 = 12 Cats
2012 = 14 Cats
Population B
2000 = 20 Cats
2010 = 21 Cats
2012 = 22 Cats
Slide 4 – Types of GraphsEcologists study graphs to see how population size changes.
Graphs are named by how they are shaped!
Linear Graph J-Shaped Graph S-Shaped Graph
Slide 5 - Linear GraphPopulations would grow at the same rate over
time. E.g. $3/Hour
Amount that you make every hour doesn’t change!
Slide 6 J-Shaped GraphLooks like a “J”
(aka Exponential Growth Graph)Growth exponentially increases!
Every hour you would make more and more money!
1st hour = $3
2nd hour = 32 = $9
3rd hour = 92 = $81
4th hour = 812 = $6561
Slide -7J-Shaped Graph Question
A
B
Slide 8Limiting Factors (aka Resources)
What an organisms needs to stay alive.If these are not available, individuals will die!
No Food
Too Hot or Too cold
No shelter
No Water.
Etc.
Slide 9How do populations grow in the wild?Stage 1 = Grow exponentially.Stage 2 = Too many individuals, resources in short supply.Stage 3 = Population stops growing (levels off) “K” = Carrying Capacity
Slide 10 - Carrying CapacityThe # of individuals the environment can support/carry.
More Resources = More BirthsLess Resources = More Deaths
Slide 11Demography
The study of human population size.
Slide12 - Human PopulationWe are still growing exponentially!
1800 = 1 Billion People2015 = 6 Billion People
2052 = 10 Billion People
Slide 13 - Human Limiting FactorsWe don’t have as many limiting factors as other species!We have not reached carrying capacity yet!
Because we have:
Medicine (get rid of diseases)
Clothing (to keep us warm)
Houses (protect us from weather)
Agriculture (massive amounts of food)
Slide 14Calculating A Country’s Growth RateGrowth Rate = (Births + Immigration) – (Deaths +
Emmigration)
Birth rate: # of Births
Death Rate: # of Deaths
Immigration: Individuals moving in a country.
Emigration: Individuals moving out of a country.
Slide 15 - Doubling TimeTime needed for a population to double in size.
Slide 16 - Age Structure% of people in each age group.
Countries with high % of young people, will grow faster
Countries with high % of old people, will grow slower.
Slide 17Some populations of species grow faster than
others!
Fast Life-HistoryGrow fast
Slow Life-HistoryGrow slow
Slide 18Rapid vs. Slow Life History
Condition Fast Life History
Slow Life History
Example Bacteria or Bugs Animals (e.g. Elephant)
Body Size Small Big
Birth to Adult Very Quick (hours to days) Very Slow (Years)
Good Conditions Population increases rapidly Population stays the same
Bad Conditions Population declines rapidly Population stays the same
Life Span Short (Hours to Days) Long (Years)
Slide 19 - Population Density# of individuals in an area.
Density-DependentFactors
Disease
Competition
Predators
Parasites
Food
Crowding/Stress
Density-IndependentFactors
Volcanic Eruptions
Temperature
Storms
Flood
Drought
Chemical Pesticides
Note: Most are abiotic!
Slide 20 - Patterns of DispersalDispersal = movement of species
Some like to move close together, far apart, or don’t care either way.
Slide 21 - Crowding and StressMost organisms get stressed when forced to live close.
Symptoms of Stress:
Aggression
Decrease in ability to care for children.
Decreased fertility (ability to have kids)
Lower Immune systems, get sick more often!