chapter 35: population growth. ecologists study the relationship between biotic and nonbiotic...
TRANSCRIPT
Chapter 35:Population Growth
Chapter 35:Population Growth
• Ecologists study the relationship between biotic and nonbiotic factors at 5 levels:
A. Organisms
B. PopulationsC. CommunitiesD.
Ecosystems
E. Biosphere
II. Levels of Organization
A. PopulationA. Population
• Definition: a group of individuals of the same species living in a particular area at the same time
B. Population density = # of individuals ------------------ unit area of space
How do you calculate population density?
Example:
If there are 10 red tail hawks in a 5 mile2 piece of land, what is the density of hawks per mile2?
A: 10 ÷ 5 = 2 hawks/mi2
A. Exponential Growth Definition: under ideal conditions with unlimited
resources, a population will grow exponentially
• Occurs when the individuals in a population reproduce at a constant rate.
J CURVE!
C. Logistic Growth Exponential growth does not continue for very long
Growth slows or stops as resources become less available
• Logistic growth
occurs when a
population's
growth slows or
stops following
a period of
exponential
growth
E. Carrying Capacity
Carrying capacity is the largest # of individuals of
a population that an environment can support
F. As a population approaches Carrying Capacity, average growth rate reaches ZERO (levels off)
Carrying capacity (K)
Pressure begins due to environmental
resistanceLag phase
Time
Limiting Factors
Factor that causes population growth to decrease Density-Dependent limiting factor that depends on population size
Density-Independent affects all populations in similar ways, regardless
of the population size
Density-Dependent Factors A limiting factor that depends on population size
Food, clean water competition predation parasitism disease
Density-Independent Factors
Affect all populations in similar ways, regardless of the
population size unusual weather natural disasters seasonal cycles certain human activities—
such as damming rivers
and clear-cutting forests
Human Population Growth
A. Human population began growing more rapidly about 500 years ago because life was made easier and safer by advances in agriculture and industry
B. Life improved for humans (and death rates reduced) due to:
Improved sanitation Medicine and healthcare
Birthrates remained high
With these advances, human population experienced exponential growth
C. Factors that affected pop growth: - Agriculture - Bubonic Plague - Industrial Revolution
WHAT TREND DO YOU SEE ON THIS SLIDE COMPARED TO NEXT SLIDE?
E. Current population and beyond
* There are currently 7.1 BILLION people in the world
* By the time you are in your 50’s, it is estimated there could be up to 9.6 BILLION!
Source: UN.org Report World Population Projections, June 2013
link
Negative population growth has been seen in:
Germany, Japan, and Russia among other countries.
Growth in U.S. & much of Europe has slowed dramatically
In the Future
F. Ecologists suggest that if growth does not slow down, there could be serious damage to the environment and global economy.
G. How can population growth be helped? Science Technology Use of contraceptives Smaller family sizes Starting family at older age Education