1. Interactions in Ecosystems
Chapter 14
Interactions in Ecosystems

2. Habitat and niche
Habitat-all biotic and abiotic factors in the environment where the organism lives
Niche-physical, chemical, and biological factors a species needs to survive
Habitat = where; niche = how

3. Competitive exclusion
The principle of two species competing for the same resources and resulting in one species gaining the advantage
The other species can be pushed into another niche or possibly become extinct
Could also result in
Niche partitioning (different parts being used)
Evolutionary response (divergent evolution)

4. Ecological equivalents
Species that occupy similar niches but in different geographical regions
Different regions means they DON’T compete for the same resources

5. Symbiosis Close and permanent relationship between different species
3 types
Commensalism
Mutualism
parasitism

6. Commensalism
One species benefits but the other is neither helped nor harmed
Ex: peregrine falcon and red-breasted goose

7. Mutualism
Both species benefit
Ex: lichen (green alga and a fungus)

8. Parasitism One species benefits and the other is harmed
Harmed species does not die
Benefiting species lives off tissues of the host

9. Population density
Population density-measurement of the number of individuals in a defined space or area
Can be used to determine the health of the population and ecosystem
Population dispersion indicates how species interact within the ecosystem

10. Survivorship curve
Generalized diagram showing surviving members of a species over time from a measured set of births

11. Survivorship curve

12. Survivorship types

13. Population growth Change in size of a population over time
Studied by bacterial growth
No linear growth
Have “J” curve growth cycles
Exponential growth
Population explosion
Reaches carrying capacity; “S” curve

14. Exponential growth
Occurs when individuals in a population reproduce at a constant rate
Population becomes larger over time

15. Logistic growth
Slowing or stopping of population growth after a period of exponential growth
Due to reduction in resources

16. Growth curves

17. Limiting factors Density-dependent Density-independent
Increased effect as population increases
Include disease, competition, parasites
Density-independent
Affect all populations regardless of size
Abiotic factors like temperature, drought, flood, habitat disruption

18. Mobility Immigration-movement of individuals into a population
Emigration-movement out of a population

19. Succession
Natural changes that take place in the communities of an ecosystem
3 types
Primary
Secondary
climax

20. Primary succession Colonization of new sites by organisms
First organisms are pioneer species
Example:
Forming new plant and animals colonies on volcanic rock

21. Secondary succession
Changes in a community that occur after disruption by a natural disaster or human interference
Takes less time than primary succession to reach climax

22. Climax succession
A mature community that undergoes little or no succession
All species in the community have reached their peak