ICT Role in 21st Century Education & its Challenges.pptx
Grade 9,U3-L7 population ecology
1. Is the Population Increasing, or
Decreasing?
Populations vary dramatically over time
(boom/bust cycles)
Births (B) and Deaths (D) affect populations
Immigration (I), when populations move in (I)
and Emigration (E), when populations move
out also affect population
Change in population = (B-D) + (I-E)
2. What Controls Population Size and
Growth Rate?
• Density-dependent factors:
• competition
•food
•space
•contagious disease
•waste production
•Density-independent factors:
•disturbance, environmental conditions
•hurricane
•flood
•colder than normal winter
3. Example
The small town of Fruitopia has 526 inhabitants.
Last year there were 25 births, 17 deaths, 12
people moved into the area, and 9 people moved
out of town.
Calculate the population change. Did the population
increase or decrease?
Calculate the total population at the end of the year.
At this rate, what would the population be in 4 years?
4. Example
Δ Population = (B - D) + (I - E)
= (25 -17) + (12-9)
= 11 ∴Increased
Population in 1 year= 526 + Δ population
= 526 + 11
= 537
Population in 4 years = 526 + 4 x Δ Population
= 526 + 4 x 11
= 570