Population Growth

1
Population Growth

• Period 4/5

2
Characteristics of Populations

• Main characteristics (4)
• Geographic distribution
• Density
• Growth rate
• Age structure

3
Population Growth

• Factors that affect population size (3)
• Number of births
• Number of deaths
• Number of individuals that enter or leave a
  population

4
Population Growth

• Ways to change a population (2)
• Emigration- movement out of a population
• Immigration- movement into a population

5
Exponential Growth

• Explanation This type of growth occurs when the
  individuals in a population reproduce at a
  constant rate under ideal conditions with
  unlimited resources represented by a J shape
  on a graph
• Example Bacteria can grow exponentially at first
  and reproduce themselves once every 20 minutes

6
Logistical Growth

• Explanation This type of growth occurs when a
  populations growth rate stops or slows down due
  to limited resources- represented by an S
  shaped curve on a graph
• Example a population of yeast after a few
  generations

7
Carrying Capacity

• Definition the largest number of individuals an
  environment can support due to the amount of
  resources
• Explanation as to why it is important to
  populations it limits a populations growth

8
What is a limiting factor?

• Any factor that causes a decrease in the size of
  a population

9
Limiting Factors Examples (5)

• Competition
• Predation
• Parasitism and disease
• Drought and other climate conditions
• Human disturbances

10
Density Dependent Factors

• Definition a limiting factor that depends on the
  size of the population

11
Density Dependent Factors

• Examples (4)
• competition
• parasitism
• predation
• disease

12
Predator- Prey Relationship

• Explanation the regulation of the size of a
  population by predation
• The size of the predator population changes based
  on the size of the prey population and vice versa.

13
Predator- Prey Relationship

• Explained example Killer whales limit the size
  of the sea otter population because they kill the
  sea otters for food

14
Density Independent Factors

• Definition limiting factors that affect all
  populations in the same way- it does not matter
  about the size of the population.

15
Density Independent Factors

• Examples (4)
• Unusual weather
• Natural disasters
• Seasonal cycles
• Human activities like damming rivers, clear-
  cutting forests, pollution

16
Types of Populations

• Opportunisitic
• Definition a population that takes advantage of
  a situation can reproduce rapidly- exponential
  growth
• Traits (3)
• Short life span
• Many offspring and many reproductive episodes in
  a lifetime
• Little parental care

17

• Opportunistic
• Examples (3)
• Gypsy moth
• Zebra mussel
• Dandelions and other weeds

18
Types of Populations

• Equilibrial
• Definition a more stable population
  representative of logistical growth
• Traits (3)
• Longer life span
• Few offspring and few reproductive episodes per
  lifetime
• Much parental care of young

19

• Equilibrial
• Examples (3)
• Elephants
• Humans
• Oak trees