1. POPULATION DYNAMICS CARRYING CAPACITY
CHAPTER 9
APES 12/2006

2. Figure 9-1 Page 190

3. Population Dispersion
Fig. 9-2 p. 191

4. Factors Affecting Population Growth
Births
deaths
immigration
emigration

5. The Biotic Potential Population potential capacity to grow
Intrinsic rate of increase(r ) - rate with unlimited resources
reproductive age
reproduce many times
many offspring
Two houseflies, ten years, several meters over entire earth - yuck :-(

6. Population Growth Rate
Birth Rate: births/popn at beginning
Death rate: deaths/popn at beginning
Growth rate = birthrate-deathrate
Example
Population of 5000 on Jan 1
Births 400 throughout year
Deaths 100 throughout year
What is Birthrate and deathrate?
How many added to this population this year
Calculate number added if population were 100,000 at beginning of year instead of 5000
Answers: BR=8%; DR =2%; GR=6%
Popn added is 6000

7. Rate of Growth – Births
What would affect number of births in a population?
Number of young in each “litter”
Examples of high and low number??
How often have young
Examples of seldom vs. often
Age at which females start having young
Rodents vs. elephants
Biotic potential for a population

8. Rate of Growth – Deaths
What would affect number of deaths in a population?
Lifespan
Outside environmental factors – limiting factors
density dependent
examples
density independent

9. Environmental Resistance
Limits population growth
Population size - interplay between biotic potential and environmental resistance
Carrying capacity (K) - number individuals of a given species that can be sustained - expressed as in a given area (say sq. m)
Minimum viable population
locate mates
sufficient genetic diversity

11. © 2004 Brooks/Cole – Thomson Learning (environmental resistance)
POPULATION SIZE
© 2004 Brooks/Cole – Thomson Learning
Growth factors
(biotic potential)
Decrease factors
(environmental resistance)
Abiotic
Too much or too little light
Temperature too high or too low
Unfavorable chemical environment
Abiotic
Favorable light & temperature & food
chemical environment
(optimal level of critical factors)
Generalized niche
Adequate food supply
Suitable habitat
Ability to compete for resources
Ability to hide from or defend
against predators
Ability to resist diseases and parasites
Ability to migrate and and adapt to
environmental change
Low reproductive rate
Specialized niche
Changing food supply
Too many competitors
Insufficient ability to hide from or defend
against predators
Inability to migrate and live in other
habitats
Biotic
Biotic

13. Exponential vs. Arithmetic Growth
Arithmetic: constant amount per time unit
Independent of population size
Exponential: increases by constant fraction, or exponent, by which current population multiplied
Dependent on population size
Power of biological reproduction
Compound interest

14. The J Curve

15. The Rule of Seventy
At 1% per year, population doubles in 70 years (Table 6.1)
Doubling time = 70 / % increase
So, if 4% growth (interest) rate, what is doubling time?

16. Logistic Strategies Exponential or J-phase Followed by S-phase
Do not overshoot carrying capacity
As populations increases, birthrate decreases
Intrinsic: Territoriality, decreased fertility
Extrinsic: predators, parasites, resources - may overshoot, then return to carrying capacity

17. Logistic Growth

18. Carrying Capacity

19. Factors Regulating Population Growth
Extrinsic vs. Intrinsic
Biotic vs. Abiotic
Density-Dependent vs. Density-Independent
Interspecific: predation, parasitism, competition
Intraspecific: Competition, territoriality
Stress Related factors

20. Malthusias or Irruptive Growth
May go through repeated cycles
Early successional species
Opportunists

21. Malthusian or Irruptive Growth
Rapid exponential growth (J curve) followed by population crash
Population surpasses carrying capacity
Deathrate exceeds birthrate
Thomas Malthus: human populations tend to grow until resources exhausted, death by famine, disease, war

22. Malthusian or Irruptive Growth

27. Moose and Wolves of Isle Royale

28. Isle Royale - Wolves and Moose
What caused 1930 crash in moose popn.?
Why did the moose not decrease their population before the crash occurred?
Why did the predators not exterminate the moose population?
What happened when the wolf population declined in the 1980s?

29. © 2004 Brooks/Cole – Thomson Learning
Irregular
Stable
Number of individuals
Cyclic
Irruptive
Figure 9-7 Page 194
Time

30. Few but large young, protect young, lower infant mortality
K-Strategists
Few but large young, protect young, lower infant mortality
Long lifespan
Later reproductive age
Less energy on reproduction
Later successional environments
More specialized niches

31. R-Strategist Species
Prolific reproduction, up unprotected young, high mortality rate of young
Low in trophic levels
Early succession
Opportunists
Populations regulated by extrinsic environmental effects
Insects, parasites, algae, annual plants, many fish

32. Survivorship Curves
Percent of population surviving at different ages

34. Deer in PA
DCNR and State Forest
Deer browsing studies

35. The Cats Dropped In ! What - cats parachuted into North Borneo?
What lessons can be learned?
What are the ecological connections?
(“Ecological Surprises” - page 200)