1. Species Interactions & Population Control

2. Five Major Interactions
Interspecific Competition
Predation
Parasitism
Mutualism
Commensalism

3. Interspecific Competition
Different species competing for the same resources
Niche overlap
Greater overlap = more intense competition
Outcomes:
Resource partitioning
Evolution/speciation
Competitive exclusion
Local Extinction

5. Resource Partitioning
When species divide a niche to avoid competition for resources

7. Competitive Exclusion
two species competing for the same resource cannot coexist at constant population values, if other ecological factors remain constant

8. Predation

9. Close long term associations between two or more species
Symbiosis
Close long term associations between two or more species
Three types:
Mutualism
Commensalism
Parasitism

10. Brood Parasitism
The manipulation and use of a host to raise the young of the brood parasite
*Nest hypothesis
*Mafia hypothesis
18:26 on video
Nest hypothesis – look for similar nest & egg characteristics & sneak in – cuckoo
Click nest 1st for how and hypothesis for what happens after
Mafia -  Not only do these brood parasites usually differ significantly in size and appearance, but it is highly probable that they reduce the reproductive success of thei

11. A group of interbreeding individuals of the same species
Population
A group of interbreeding individuals of the same species

12. Population Characteristics
Size
Density
Dispersion
Age distribution

13. = Population Size Four variables determine population size: Births
Deaths
Immigration
Emigration =
Population
Change
(Births + Immigration) - (Deaths + Emigration)

14. Dispersion

15. Dispersion Clumps -most popular 1. Cluster near resources
2. Groups increase chance
of finding resources
3. Protection
4. Hunting

16. Dispersal Examples Territorial Solitary Clumped (elephants) Uniform
(creosote bush)
Random
(dandelions)
Territorial
Solitary

17. Age Structure Distribution of individuals among various ages
Dictates how rapidly a population
Three groups:
1. Pre-reproductive stage
not mature enough to reproduce
2. Reproductive stage
capable of reproduction
3. Post-reproductive stage
too old to reproduce

18. A B C D

19. Life Tables Shows life expectancies for age groups
Demography: Study of a populations vital statistics and how they change over time
Life table
females
males
The difference in life-span between male and female Richardson's ground squirrels in nature is attributable to the different reproductive strategies adopted by the two sexes. Juvenile males pursue the high-risk strategy of dispersal, emigrating from their natal area to an unfamiliar location where they encounter squirrels that are not kin. Dispersal has the reproductive advantage of avoiding inbreeding but incurs the disadvantages of traversing unfamiliar territory, exposure to predators, contact with machinery or vehicles while crossing roads, and being attacked by resident ground squirrels as they attempt to settle in a new location. Adult male Richardson's ground squirrels experience extreme pressures during the mating season due to intra-sexual competition for access to estrous females. Males engage in vigorous fights, and the resulting wounds and stress can cause fatalities. Additionally, males are less vigilant about watching for predators during the mating season.
Female Richardson's ground squirrels are more sedentary and conservative in their reproductive strategies than males. Females tend to stay in a familiar location in or near their natal home range throughout their lifetime, and females do not engage in fights during the mating season.
What adaptations have led to this difference in male vs. female mortality?

20. Exponential Growth Constant growth of a population J shaped curve
Birth rate exceeds the death rate
J shaped curve

21. Conditions for Exponential Growth
Unlimited resources
Abundant space
Abundant food
Shelter
Decrease in predators
Decrease in disease
Reproduction

22. Rule of 70 How long does it take to double? Rule of 70 Resource use
Population size
Money in a savings account
Rule of 70
70 divided by the percentage growth rate = doubling time in years
70 / 7% means it takes ten years to double

23. Human Population

24. Logistic Growth
Growth of a population slows or stops as resources become less available
S curve

25. Carrying Capacity
The largest number of individuals that a given environment can support at a given time

26. Regulation of population size
Limiting factors
density dependent
competition: food, mates, nesting sites
predators, parasites, pathogens
density independent
abiotic factors
sunlight (energy)
temperature
rainfall
marking territory = competition
competition for nesting sites

27. St. Matthew’s Island

28. Ecological Succession
Predictable changes that occur in a community over time
Two types:
Primary
Secondary

29. Begins in a place without any soil
Primary Succession
Begins in a place without any soil
Examples:
Volcanos
Glacier retreats
Process begins with pioneer species
lichens or cyanobacteria

30. Primary Succession Moss move in bringing insects Ferns & grasses
Shrubs & Trees

31. Organisms evades an ecosystem that already existed before
Secondary Succession
Organisms evades an ecosystem that already existed before
Usually a result of disturbance
Human disturbance
Natural catastrophes

32. Steps in Secondary Succession
Major disturbance – weeds come in
Grasses
Pines begin to grow
Grasses are shaded out
Old pines die – hardwoods begin to replace

33. Secondary Succession

34. Climax Community
A stable group of plants and/or animals that colonize an area after a succession event Ex: Old Growth Forest

35. Climax Community Climax communities are not always BIG trees!
Grasses in prairies
Cacti in deserts

36. Aquatic Succession
Transition of aquatic habitats (mainly ponds) filling with sediments & the eventually becoming a terrestrial ecosystem