Lecture 17 - Succession

Question 1

Define succession

Answer 1

The process of directional change in communities.

Question 2

What are 2 major kinds of succession? Give an example for each

Answer 2

1. Primary succession
   Occurs on a new sterile area, such as that uncovered by a retreating glacier or created by an erupting volcano.
   ex: Sand dunes on Lake Michigan
2. Secondary succession
   The recovery of distrubed sites, where a biological legacy (propagules, living organisms) exists.
   ex: Bog

Question 3

Name 3 factors that affect succession

Answer 3

1. Availability of colonizers. Ex: seeds, larvae
2. Abiotic and biotic environment. Ex: nutrient availability, soil formation, presence of herbivores
3. Processes among the successional species: Early species can help, hinder or not affect the establishment of later species (facilitation, inhibition).

Question 4

Name 4 models of succession (Why does the community change through time in a directional matter)

Answer 4

1. Facilitation: early species facilitate later ones.
2. Inhibition: early species inhibit later ones, but eventually die.
3. Tolerance: Later species are more tolerant of limiting resources, so remain at later stages.
4. Random

Question 5

Which factor of succession do each of this affect in the sand dune experiment?

1. Soil development
2. Seed arrival
3. Water shortage
4. Seed predation

Answer 5

1. Soil development: Facilitation
2. Seed arrival: Inhibition/random
3. Water shortage: Tolerance/facilitation
4. Seed predation: Inhibition

Question 6

Why did the Late successional species in the sand dune experiment have a high mortality rate?

Answer 6

High mortality due to: seed predation by rodents and water shortage

Question 7

How can succession change light regime of plants?

Answer 7

Plant species show physiological and morphological adaptation to specific position in a succession gradient (and access to light/ shade tolerance).

Question 8

What is forensic entomology? How is it related to succession?

Answer 8

Studying bugs in dead corpses to roughly calculate when a victim died based on the developmental stage of the bugs when the body is discovered.

We can calculate the time based on known successions of bugs.

Question 9

Explain the Seasonal succession of Plankton in Lakes.

Answer 9

Initially, the spring bloom forms a lot of small algae. Then, there’s a clear water phase was due to grazers that came in, they couldn’t get there at the beginning , they had to wait for that first big bloom of algae and then they could come in and graze the algae. After when nothing is left, they start declining. When large algae come in during summer, they are too big for the grazers. Then winter wipes everything away.

Question 10

Define climax in succession (old view then new view)

What’s the final view?

Answer 10

Climax: The end point of succession

Old view: final or stable community in a successional series. It is self-perpetuating and in equilibrium with the physical and biotic environment.

New view: Ecosystem is open and in non-equilibrium.

Climax is rarely a deterministic, fixed endpoint of succession, but rather a continuum of endpoints, depending on soil conditions, among others.
Climax is an abstract ideal that is seldom reached

Question 11

Why is the Climax is an abstract ideal that is seldom reached in many instances?

Answer 11

Climax is rarely a deterministic, fixed endpoint of succession, but rather a continuum of endpoints, depending on soil conditions, among others.

Reason: Impact of the abiotic (e.g. climate fluctuations) and biotic environment (e.g. grazing)

Question 12

Define patch dynamics.

Give 2 examples.

Answer 12

perspective that dynamics of an ecosystem can be understood as a mosaic of patches.

1. Wind-blown forest gaps:
   Tree falls > secondary succession > tree falls somewhere else nearby
2. Mussel bed build up and destabilization
   Mussels grow > patch destabilizes > removed by currents > new succession

Question 13

Relate the adaptive strategies of species in early and late stages of succession to the ideas of r and K selection.

Answer 13

R-selected species are early succession species, k-selected species are late succession species.

Question 14

How do early-successional species continue to exist?

Answer 14

Constant shifting and opening up of the niches

Question 15

Describe the difference between primary and secondary succession - which one occurs in forensic entomology?

Answer 15

Secondary