1. And Human Population Trends
Population Notes
And Human Population Trends

2. Population- group of similar individuals (species) living in one area
The size of a population will change over time

3. Population Determiners
Natality (+)- birth rate
Mortality (-)- death rate
- both of these are rates within a pop. in a community
Immigration (+)- the arrival of individuals into a community from somewhere else
Emigration (-)- the departure of indiv from a community

4. Open v. Closed Populations
Open population- a pop. (or community) where immigration and emigration occur freely; ex- the state NC
Closed Population- a pop. in which individuals are not allowed to leave and enter freely. This is usually due to some physical barrier; ex- Galapagos Islands

5. Example (do not copy)
An open population of Elk in the Comanche River Basin of Wyoming has a natality rate of 12.4 elk/year and a mortality rate of 10.6 elk/yr. This population of elk emigrates to a hanging valley to forage for vegetation in the winter. At this time, a herd of 9 elk immigrates into the Comanche River Basin population from the Shoshone River Basin elk population.

6. Factors that Affect Pop.
Biotic Potential- the highest possible rate of reproduction under ideal conditions
Limiting Factors- circumstances that keep org. from reaching biotic potential

7. Limiting Factors * tied to population size Density Dependent
Density Independent
Limiting Factors
(related)
(individual)
shortage of food*
temperature , drought, floods, volcanic eruptions, natural disasters
lack of space*, disease*, predators*, parasites*
oxygen supply
* tied to population size

8. Carrying Capacity
The greatest number of individuals a community can support
Can change as conditions (biotic/abiotic) change
When a community reaches c.c. natality and mortality are approximately equal

9. Homeostasis
When a pop is in balance with all the abiotic and biotic factors that influence it

10. Population Graphs
Populations of a species can follow one of two basic graph shapes: J or S curves.

11. J-Curve Most populations cannot maintain a J-curve forever…why not?
Features: Population growth starts slow and then speeds up (shows exponential growth)
As population increases, rate of growth increases
* Population will continue to grow exponentially as long as there are no limiting factors
Most populations cannot maintain a J-curve forever…why not?

12. J-Curve Examples
Bacteria
Duck Weed
Cancer Cells

13. S-Curve
Population growth starts slow, speeds up, but hits a limit (Carrying Capacity) and balances out.
More realistic because, populations can’t grow forever due to limiting factors.
Shows Logistic Growth
. Limiting factors slow or control the population (Examples: predators, space, shelter, food, disease).
Carrying Capacity: the number of individuals of a species an environment can support without becoming harmed.

14. Life History Patterns Slow-life history Rapid-life history
*reproduce slowly; long time to mature * reproduce quickly; quick to mature
* few offspring in a lifetime * many offspring in a lifetime
* long life span * short life span
* large bodies * small bodies
* live in a stable environment * live in unpredictable/harsh envir.
humans, elephants, pandas, etc. * bacteria, flies, mosquitoes, etc.
*good for scientific experiments

15. I. Why is human population growth an environmental problem?
A. Causes of human population growth
1. Agricultural Revolution – people settle into communities and more people were needed for division of labor; more reliable food supply can support a larger population.
2. Industrial Revolution – In the early 20th century technological advancements led to improvements in medicine and sanitation allowing for an increased birth rate and decreased death rate.
3. Urbanization (development of cities) leads to economic and social development which influences human population growth in an area.

16. I. Why is human population growth an environmental problem?

17. I. Why is human population growth an environmental problem?
Industrial Revolution

18. Human Population Density
What problems do heavily populated areas have environmentally?

19. Population Pyramids

20. Population Pyramids
What can you tell about this country based on its age structure graph?
Wide base = rapid growth
Skinny top = poor health care

21. What can you tell about this country based on its age structure graph?
Base not much wider than middle = slow growth
Balanced fairly evenly throughout ages = good health care
# of females at top = females have longer life expectancy

22. What can you tell about this country based on its age structure graph?
Base smaller than middle = population decline
Balanced fairly evenly throughout age groups = good health care
# females at top = live longer

23. Human Population Graphs