Go Forth and Populate:

1
Go Forth and Populate

• Exploring Population Dynamics
• ECOLOGY NOTES

2
What is a population?

• Population
• A group of organisms of the same species living
  within an ecosystem
• Population size within a ecosystem drastically
  effects the stability of on ecosystem
• Ex.
• Cane Toad
• Lynx and Hare
• Grizzly and Salmon

3
Factors the determine how much a population will
change

• Births
• Deaths
• Migration
• Immigration - moving into an ecosystem
• Emigration - moving out of an ecosystem
• Stable populations occur when
• the of individuals joining the
  individuals leaving
• Population change (birth - deaths)
  (immigrants - emigrants)

4
How Populations Grow

• J-Shaped Curve
• shows exponential growth of a population
• Occurs in ideal conditions
• Resources are unlimited
• Predation absent
• Disease absent

5
How Populations Grow

• 2. S-Shaped Curve
• Shows population limited by environmental
  factors
• Occurs in non-ideal conditions
• Resources are limited
• Predation present
• Disease present

6
Can Populations Keep Growing Forever?

• Limiting Factors
• Abiotic and biotic components of an ecosystem
  that reduce the size of a population
• Major Categories
• Energy
• Raw Materials
• Disposal of Waste
• Organism interactions
• Carrying Capacity
• Maximum number of individuals in a population
  that an ecosystem can support

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The Growth Curve in More Detail

• Phase 0
• Lag Phase
• Slow growth when population 1st enters an area
• Phase 1
• Exponential phase. Unlimited population growth.
• Abundant food, no disease, no predators etc
• Phase 2
• Decline or transitional phase.
• Limiting factors slowing population growth.
• Phase 3
• Stable equilibrium phase
• No growth. The limiting factors balance the
  populations capacity to increase.
• The population reaches the Carrying Capacity (K)
  of the environment.
• Phase 4
• Death Phase
• Deaths exceeds births
• Population decreases

3
2
4
1
0
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Common Trends in Growth Curves

• Boom and Bust Cycles
• Rapid population growth followed by a massive
  die-off
• Populations that are influenced by seasonal
  weather patterns
• Frosts Droughts Fires Flood s
• Predator-Prey Cycles
• The prey population rises, causing the predator
  population to also rise.
• Predators then overfeed on prey, causing the prey
  population to drop,
• Once the prey population drops, the predator
  population drops due to lack of food.
• The cycle repeats indefinitely.

9
Example The Lynx Hare
10
Human Population

• We have examined factors that affect populations
• Lets examine the human population worldwide

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• Its a J-shaped curve
• Exponential Growth

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Individuals are not distributed equally!
13
Age structures of three nations
Shrinking
Growing
Stable
Are these growing, shrinking or stable
populations?