Question

1) Explain why we typically find more species under conditions of intermediate disturbance compared to either rare or frequent disturbance. (Ch. 18)

2) Why might you expect communities with fewer species to contain fewer trophic levels? (Ch. 18)

3) How do ecologists distinguish between primary and secondary succession? (Ch. 19)

4) When using a chronosequence to document the pathway of succession, what are the assumptions? (Ch. 19)

5) Why should we not expect a single climax community within a biome? (Ch. 19)

6) Compare and contrast the concepts of facilitation, inhibition, and tolerance in the context of ecological succession. (Ch. 19)

7) When a community experiences succession, why does the species richness of a community initially increase, then plateau, and finally decline? (Ch. 19)

8) Why do early- and late-successional species tend to possess different adaptations? (Ch. 19)

9) Why is the efficiency of energy transfer between two trophic levels generally quite low? (Ch. 20)

10) How do ecologists distinguish between gross primary productivity and net primary productivity? (Ch. 20)

11) Compare and contrast the measurement of primary productivity in terrestrial vs. aquatic systems. (Ch. 20)

12) What factors limit the net primary productivity of terrestrial systems? (Ch. 20)

Answer 1

1- intermediate disturbance hypothesis states that more species under intermediate disturbance are found. this is because, in high disturbances like disaster or fire all species are in danger whereas, in rare disturbances, species will exist till resources become scarce after that dominant species will only be able to survive.

2- communities with the larger population have more trophic levels as compared with communities with the small population due to larger resources like producers and consumers.

3- primary succession is the development of ecosystem on a place without any life whereas secondary succession is the development of ecosystem on a place previously inhabited or existing biota destroyed by disaster or major disturbances like the forest fire.

4- assumptions- various sites have similar abiotic conditions and the sites pass through same stages of growth.

5- due to changes in environment the single climax community can be destroyed thus, different climax communities are there to support the succession.

6-

• facilitation- a process in which species alter the environment to make it suitable for them or other species.
• inhibition- a process in which one species inhibit other species growth and thus have the negative impact on other
• tolerance- no specific species can have the effect on other, species tolerate each other.

7- due to the limitation of resources over the time and competitive exclusion.

8- due to the availability of different resources and an increase of competition within the biome over the time.

9- because energy is lost in the form of metabolic heat

10- NPP= GPP-R(Respirtion)

Where GPP is gross primary production i.e, amount of carbohydrate produced by plants during photosynthesis.

11- in the terrestrial ecosystem, PP is measured using NPP only whereas, in the aquatic ecosystem, oxygen concentration variation is measured.

12- factors like temperature, moisture, avalable nutrients, photosynthesis rate can affect PP.