1. population dynamics
A look at the factors that tend to increase or decrease the size of a population.

2. The population size of a species in a given space at a given time is determined by the interplay between BIOTIC POTENTIAL and ENVIRONMENTAL RESISTANCE.
Biotic potential = growth rate with unlimited resources.
Environmental resistance = all the factors acting jointly to limit population growth.

3. (environmental resistance)
POPULATION SIZE
Growth factors
(biotic potential)
Favorable light
Favorable temperature
Favorable chemical environment
(optimal level of critical nutrients)
Abiotic
Biotic
High reproductive rate
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 live in other
habitats
Ability to adapt to environmental
change
Decrease factors
(environmental resistance)
Too much or too little light
Temperature too high or too low
Unfavorable chemical environment
(too much or too little of critical
nutrients)
Low reproductive rate
Specialized niche
Inadequate food supply
Unsuitable or destroyed habitat
Too many competitors
Insufficient ability to hide from or defend
Inability to resist diseases and parasites
Inability to migrate and live in other
Inability to adapt to environmental

4. Four variables change population size:
NATALITY = birth rate
MORTALITY = death rate
IMMIGRATION = rate of organisms moving in
EMIGRATION = rate of organisms moving out

5. REPRODUCTIVE STRATEGIES
Number of individuals
Time
Carrying capacity
K species;
experience
K selection
r species;
r selection K

6. Opportunistic or r-Selected Species
cockroach
dandelion
Many small offspring
Little or no parental care and protection of offspring
Early reproductive age
Most offspring die before reaching reproductive age
Small adults
Adapted to unstable climate and environmental
conditions
High population growth rate (r)
Population size fluctuates wildly above and below
carrying capacity (K)
Generalist niche
Low ability to compete
Early successional species

7. Competitor or K-Selected Species
elephant
saguaro
Fewer, larger offspring
High parental care and protection of offspring
Later reproductive age
Most offspring survive to reproductive age
Larger adults
Adapted to stable climate and environmental
conditions
Lower population growth rate (r)
Population size fairly stable and usually close
to carrying capacity (K)
Specialist niche
High ability to compete
Late successional species

8. Percentage surviving (log scale)
SURVIVORSHIP CURVES
Percentage surviving (log scale)
100 10 1
Age

9. Population density affects population growth.

10. R-strategists populations are most affected by these.
DENSITY INDEPENDENT FACTORS = affect a populations’ size regardless of its population density.
Weather
Earthquakes
Floods
Fires
. . . Natural disasters
R-strategists populations are most affected by these.

11. DENSITY DEPENDENT FACTORS = affect a populations’ size depending on its population density.
Predation
Disease
Availability of food and water
Space
Negative Feedback!!

12. INTERNAL FACTORS = might include density-dependent fertility or size of breeding territory.
EXTERNAL FACTORS = might include predation and disease.

13. Competition for resources.
Species interactions influence population growth and carrying capacity = SYMBIOSIS
Competition for resources.
High
Low
Relative population density 2 4 6 8 10 12 14 16 18
Days
Each species grown alone
Paramecium
aurelia
caudatum
High
Low
Relative population density 2 4 6 8 10 12 14 16 18
Days
Both species grown together
Paramecium
aurelia
caudatum

14. Resource Portioning

15. PREDATION
PREY POPULATION
PREDATOR POPULATION

16. Avoiding predators Span worm Bombardier beetle
Viceroy butterfly mimics
monarch butterfly
Foul-tasting monarch
butterfly
Poison dart frog
When touched, the
snake caterpillar
changes shape to look
like the head of a snake
Wandering leaf insect
Hind wings of io moth
resemble eyes of a
much larger animal

17. Parasitism

18. Oxpeckers and black rhinoceros Clown fish and sea anemone
Mutualism
Oxpeckers and black rhinoceros
Clown fish and sea anemone

19. Shark and ramora

20. Cleaning station
Cleaner blenny
Sabertooth blenny

21. Commensalism

22. Herbivory