Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
22 Cards in this Set
- Front
- Back
Define:
Community |
Any assemblage of living organisms in a prescribed area or habitat.
Can be of any size, and any taxonomic composition. |
|
What are the 2 opposing views of what a community constitutes?
What "big question" does this ask? |
1) Community as a "super-organism". (similar to the "web of life")
2) "Individualistic" view Big Question: "Is the community an organized system of recurrent species OR a haphazard collection of a population with minimal integration?" |
|
Define:
Succession |
The directional change in community composition over time.
|
|
What are the 2 main types of succession?
Describe them briefly. |
1) Primary Succession - Colonization of a new, *sterile* site.
2) Secondary Succession - Recolonization of a disturbed site. |
|
The colonizing of an area near a volcano after a massive eruption would be an example of which type of succession?
|
Primary Succession
*The volcano's lava would sterilize (kills all life) an area around the volcano, thus making this an example of primary succession. |
|
The colonization of a forest after a large forest fire would be an example of what type of succession?
|
Secondary Succession
*There would still be bacteria living in the soil underneath the burned layer (i.e. the site is not completely sterile), thus making this an example of secondary succession |
|
What are 3 characteristics of a geographic site that would allow for Primary Succession?
|
1) Sterile habitat (i.e. no plants, seeds, or bacteria in the soil)
2) Low or no nutrient availability. 3) Erosion |
|
What are 3 characteristics of a geographic site that would allow for Secondary Succession?
|
1) Disturbance can be of any size.
2) Seed bank of later successional species present (i.e. the site is *not* sterile) 3) Bacteria and other soil organisms present. |
|
Define:
Old Fields |
Land that was formerly cultivated/grazed (i.e. used for agriculture) but later abandoned.
|
|
Define:
Obligate Seeder |
Plants with large, fire-activated seed banks that germinate, grow, and mature rapidly following a fire in order to reproduce and renew the seed bank before the next fire.
*source: Wiki |
|
Chaparral shrubs after fire:
Adenostoma (Chamise) is an example of a _____. |
resprouter/seeder
|
|
Chaparral shrubs after fire:
Ceanothus is an example of a _____. |
Obligate seeder
|
|
Describe the policy of fire suppression over the 1900's.
What is policy theorized to have caused? |
- Policy of fire suppression started in the early 1900's.
- Caused changes in the forest structure. - Increased the density of trees. - Shift from fire tolerant, shade intolerant TO fire sensitive, shade-tolerant species. --------------------------------------------------- Theorized to have increased the magnitude of fires that occur. - Higher densities increased the fuel load. - Understory of trees provided "ladder fuel" - Overall increased risk of catastrophic, stand-replacing crown fire. |
|
What are the 4 main Models of Succession used?
|
1) Facilitation Model
2) Inhibition Model 3) Tolerance Model 4) Random Colonization Model |
|
Models of Succession:
Describe the Facilitation Model (4 pts) |
1) Habitat colonized by a "pioneer species"
- Usually weeds (good dispersal power, rapid growth) 2) Pioneer species modify the environment (i.e. changes the soil structure and nutrient availability) 3) This modification facilitates colonization by other species 4) A climax community is reached (i.e. a stable endpoint) |
|
Models of Succession:
Describe the Inhibition Model (4 pts) |
1) "Who gets there first" is important
2) Initial species inhibits others from colonizing 3) Sequence is less predictable 4) A climax community is reached. |
|
Models of Succession:
Describe the Tolerance Model (3 pts) |
1) Any species can start succession
2) Good competitors predominate in climax community 3) Initial community composition directs succession. |
|
Models of Succession:
Describe the Random Colonization Model (3 pts) |
1) The "Null model"
2) No facilitation or inhibition 3) Succession is caused by: - Change survival of different species - Random colonization by new species |
|
Define:
Climax Community |
The final or stable community in a successional series.
- Self-perpetuating - In equilibrium with physical and biotic environment |
|
Who came up with the Monoclimax Hypothesis?
What does this hypothesis say? |
F.E. Clements in 1936.
- One region, one climax community - Climax community produced entirely by region's climate. |
|
Who came up with the Climax-Pattern Hypothesis?
What does this hypothesis say? |
R.H. Whitaker in 1953.
- Climax at any location is a result of all environmental factors such as: {climate, soil type, fire, biotic factors, wind} - Climax community for a contiuum along environmental gradients |
|
Of the following hypotheses:
- Monoclimax Hypothesis - Climax-Pattern Hypothesis ...which is generally accepted by ecologists today? |
Climax-Pattern Hypothesis
|