1. Presented by Mr. Rainbeau
How Populations Grow
Presented by
Mr. Rainbeau

2. Define Population
group of individuals of the same species that live in the same area

3. What 3 characteristics are used to describe a population?
Geographic distribution
Density
Growth rate

4. Define Population Density
the number of individuals per unit area
In which picture is the bird population most dense?

5. What factors affect population size?
number of births
number of deaths
number of individuals that enter or leave the population
immigration & emigration

6. Define Immigration the movement of individuals into an area
causes a population to grow

7. Define Emigration the movement of individuals out of an area
causes a population to decrease in size

8. Who is immigrating? Who is emigrating?

9. Define Exponential Growth
occurs when the individuals in a population reproduce at a constant rate.
J-shaped curve

12. What kinds of conditions are needed for exponential growth?
ideal conditions, with unlimited resources
plenty of food, water, space, mates, & no disease, parasites, predators

13. Define Logistic Growth
Occurs when a population’s growth slows or stops following a period of exponential growth
S-shaped curve

15. Define Carrying Capacity
number of individuals that a given environment can support

17. Presented by Mr. Rainbeau
Limits on Growth
Presented by
Mr. Rainbeau

18. Define Limiting Factors
a factor that causes population growth to decrease

19. What determines the carrying capacity of an ecosystem?
limiting nutrients; limiting factors
(the amount of available food, water, space, and other environmental factors)

20. Define density-dependent limiting factors.
a limiting factor that depends on population size

22. What are 4 examples of density-dependent limiting factors?
Competition
Predation
Parasitism
Disease

23. Competition
When organisms compete for food, water, mates, and space

24. Predation – one organism feeding on another

25. Parasitism
parasites take nutrients from their host

28. Disease
infectious diseases are caused by bacteria or virus

29. Define predator-prey relationship.
regulation of a population by predation
mechanism of population control

31. Boom-and-bust curve shows exponential growth followed by a sudden collapse

32. Define density-independent limiting factors.
affects all populations in similar ways, regardless of population size

33. What are 4 examples of density-independent limiting factors?
Unusual weather
Natural disasters
Seasonal cycles
Human activities

35. We can predict changes that may occur in a population
What is the advantage of understanding the factors that influence population growth?
We can predict changes that may occur in a population

37. III. Human Populations

39. 1.Currently the human population has been growing exponentially
Due to increasing gap between birth rates and death rates
Why?
a) Developments caused death rates to drop and the life expectancy to increase

40. 17501900 population doubled 800 million to 1.6 billion (150 years)
19001965 doubled again to 3.2 billion (65 years)
2004 population reached billion (39 years)

43. Population (in billions)
World population estimates milestones (USCB)
Population (in billions) 1 2 3 4 5 6 7 8 9
Year
1804
1927
1960
1974
1987
1999
2012
2027
2046
Years elapsed -
123 33 14 13 12 15 19

44. Exponential human growth cannot continue
Factors that affect human populations: crowding, food, natural disasters, pollution, space, water, mates, and disease

45. What would happen if the human population does not level off?
The Earth would not be able to provide a sufficient amount of resources to support the growing population and people would begin to die as a result of illness, starvation, and other related causes.