1. Species Interactions and Population Ecology

2. Community Ecology Involves the study of species interactions
Distribution of species around the world is determined by:
Species fundamental niche
Ability to disperse in an area
Interactions with other species
Competition
Predation
Parasitism
Mutualism
Commensalism

3. Intra- Specific Competition
1. Intra-specific competition: occurs among members of the same species
2. There is a limit to the number of individuals that can survive in an area
3. Compete for:
Living space
Mates
Food and water
Beta is on left and alpha is on the right. Beta challenges alpha for position in wolf pack.

4. Inter - Specific Competition
1. Inter-specific competition: competition between two or more species for some limiting resource such as:
food or nutrients, space, mates, nesting sites—
anything for which demand is greater than supply
one species is a better competitor, interspecific competition negatively influences the other species by reducing population sizes and/or growth rates
2. Importance: influences species evolution, the structuring of communities and the distributions of species

5. Competition
Competition: struggle of individuals to obtain limiting resources
Competitive exclusion: two species trying to utilize the same resources at the same time cannot co-exist.

6. Resource Partitioning
Resource partitioning: two or more species divide a resource based on the differences in the species’ behavior or morphology

7. Predation
Predation: the use of one species as a resource (prey) by another species (predator)
Predators help keep prey populations healthy
Co-evolutionary relationship
Examples:
True predators: hunt, kill, and consume prey
Herbivores: consume plants as prey

8. Parasitism  
Parasitism: One organism benefits (parasite), the other is harmed or hurt (host)
Endoparasites
Exoparasites
Parasitoids: lay eggs inside of other organisms
Nest (brood) parasitism

9. Mutualism   1. Mutualism: both species benefit from the relationship
2. Each species in the relationship assists the other to its own benefit
3. If the benefit is too small, it will no longer be worth the cost of helping the other species; natural selection would select against this relationship

10. Commensalism  
Commensalism: one species benefits and the other is neither harmed nor helped
Examples:
Birds perching on tree branch
Fish hiding from predators in coral reef

11. Population Ecology
Population Ecology: Study the factors that cause populations to increase or decrease.
When is it useful?
Endangered species
Cause of the decline?
Situation improving?
Invasive species
How did it get here?
How can we control growth?
Pests
How is the pest affecting humans and other organisms?

12. Density Dependent Limiting Factors
Influence an individual’s probability to survive and reproduce
Large populations are affects more than smaller populations
Examples:
Amount of available food
Parasitism and disease
Competition and predation

13. Density Independent Limiting Factors
Affects all members of the population regardless of the size of the population or the health of the individuals
Examples: Natural disasters (droughts, floods, hurricanes, tornados, wildfires, earthquakes) and pollution

14. Exponential Growth Model
J shaped curve
Population grows indefinitely as long as there is no environmental resistance
Continuously increasing population; grows at a fixed rate

15. Logistic Growth Model S-shaped curve
Population is initially exponential, but it slows as limits are placed on the population
Limits include:
Too little food
Too much waste
Disease

16. Carrying Capacity Carrying capacity: Referred to as K
Maximum number of individuals the population can support at a given time
Not fixed
Overshoot: when population becomes larger than spring food supply; will then result in a die-off or population crash

17. Survivorship Curves Patterns of survival Type I: K-selected
Have high survival rate throughout most of their life; die as they reach old age
EX: elephants, humans, whales
Type III: r-selected
Low survivorship early in life; few individuals reach adulthood
EX: salmon and mosquitoes
Type II:
EX: Rodents, birds, and corals
Relative constant decline in survivorship throughout life

18. Predator-Prey Populations
Populations of both species cycle over time. The lynx population peaks 1-2 years after the hare population peaks. As the hare population increases, it provides more food for the lynx population. Food becomes more scarce for the hare population, so their numbers fall. The lynx has less hares to eat, so its population fall.

19. Reproductive Strategies
K-selected species:
Low intrinsic growth rate; population increases slowly
Traits:
Long life span
Long time to reach maturity
Few reproductive events
Few offspring produced per pregnancy
Large offspring
Parental care
Population regulated by density dependent limiting factors
Abundance is determined by carrying capacity (K)

20. Reproductive Strategies
r-selected
r stands for rapid
Traits
Short life span
Short time to reproductive maturity
Many reproductive events
Many offspring at one time
Offspring small size
No parental care
Fast population growth
Population is regulated mainly by density independent limiting factors
Population dynamics variable

21. Ecological Succession
Ecological succession: the normal gradual change in species composition in a given area over time
Number and types of species in an ecosystem change in response to changing environmental conditions
Fires
Volcanic eruptins
Climate change
Clearing forests

22. Primary Succession
Begins with bare rock exposed by geologic activity - volcanism, glaciers, abandoned highway, newly created pond
No soil
Pioneer species: first to colonize previously disrupted or damaged ecosystems, beginning a chain of ecological succession

23. Secondary Succession
Begins on soil from which previous community has been removed (by fire, flood, agriculture)
Secondary succession can proceed much faster because the soil has been prepared by the previous community

24. Eco Succession & Biodiversity