1. Population and Community Dynamics
Chapters 19 and 20

2. Populations
Population size: number of individual organisms present at any one time
May increase, decrease, undergo cyclical change or remain stable over time

3. Population Density Number of individuals in a population per unit area
High density makes it easier for organisms to mate and clump together, but can also increase competition and instances of infection diseases

4. Population Distributions
Spatial arrangement of organisms in an area
Random
Uniform
Clumped

5. Population Distribution
Random
Resources are plentiful and other organisms do not strongly influence the population
Uniform
Occur when individuals hold territory or compete for space; ex: desert plants
Clumped
Most common; arrangement according to availability of resources; ex: humans

6. Life History Patterns Type I: Type II: Type III:
Survival rates are high when organisms are young and decrease sharply when they are old
Type II:
Survival rates are equivalent regardless of an organism’s age
Type III:
Most mortality takes place at young ages and survival rates are greater at older ages

7. Life History Patterns

8. Population Growth Exponential Growth
Rate of increase goes up as the total number of females goes up
Populations undergo exponential growth unless they meet constraints

9. Habitats Limiting Factors
Physical, chemical, biological attributes of the environment that restrain population growth
Any factor whose shortage or absence restricts species success
Density Independent
Density Dependent

10. Carrying Capacity Carrying Capacity
Maximum population size of a species the environment can continuously support and sustain
The closer the population is to the carrying capacity, the greater the environmental resistance

11. Carrying Capacity

12. Logistic Curve is just a model

14. Kinds of Organism Interactions
Predation - One animal kills/eats another.
Predator benefits from food.
Prey adaptation is manifested in a higher reproduction rate.

15. Prey Defenses Prey defenses Mechanisms to prevent being eaten Spines
Tough epidermis (skin)
Poisonous Chemicals
Camouflage
Bright Coloration
Flocking Behavior

16. Lynx and Snowshoe Hare

17. Competition
Competition - Two organisms strive to obtain the same limited resource, and both are harmed to some extent.
Intraspecific - Members of same species competing for resources.
Interspecific - Members of different species competing for resources.
The more similar the competing species, the more intense the competition.

18. Mimicry Mimicry One species resembles another species
Mimicked species possesses an overt antipredator defense
2 types of Mimicry
Müllerian
Batesian

19. Mimicry
Müllerian Mimicry - Mimic shares same protective defense

20. Mimicry
Batesian Mimicry - Mimic lacks defense of the organism it resembles

21. Symbiotic Relationships
Symbiosis - Close, physical relationship between two different species. At least one species derives benefit from the interaction.
Parasitism - One organism (parasite) lives in or on another organism (host), from which it derives nourishment.

22. Ectoparasites - Live on host’s surface.
Fleas
Endoparasites - Live inside host.
Tapeworms

23. Symbiotic Relationships
Commensalism - One organism benefits while the other is not affected.
Remoras and Sharks
Mutualism - Both species benefit. Obligatory in many cases as neither can exist without the other.
Coral and Zooxanthellae

24. Cleaning Symbiosis