#16-Change In Communities

Question 1

What are agents of change?

Answer 1

Act on communities across all temporal and spatial scales

- abiotic and biotic

Question 2

What is succession?

Answer 2

Directional change in species composition over time as a result if abiotic and biotic agents of change

Question 3

What is primary succession?

Answer 3

Starting with no life

• starting and regrouping from scratch
• not slot of competition

Question 4

What is secondary succession?

Answer 4

Some kind of disturbance to an already formed community

- not all species are lost

Question 5

What are the first colonizers?

Answer 5

They tend to be stress tolerant and can transform the habitat in ways that benefit their growth and that of other species

Question 6

What are the type of species that are found in the first stages of succession?

Answer 6

Ecosystem engineers

Question 7

What is a super organism?

Answer 7

Group of species working together towards some deterministic end

Question 8

What is a climax community?

Answer 8

Each community reaches a stable end point

- composed of dominant sledges that persist over many years

Question 9

What are the 3 models of succession?

Answer 9

1. Facilitation model- early species modify the environment in ways that benefit the later species
2. Tolerance model- assumes earliest species modify the environment but in neutral ways that neither benefit nor inhibit later species
3. Inhibition model- assumes early species modify conditions in negative ways that hinder later successional species

Question 10

Why are facultative interactions important?

Answer 10

They drive early succession

- especially when conditions are stressful

Question 11

What are alternative stable states?

Answer 11

Different communities follow different successional paths develop in the same area under similar environmental conditions

Question 12

When is a community stable?

Answer 12

When it returns to its original state after disturbance

Question 13

What is hysteresis?

Answer 13

An inability to shift back to the original community type, even when original conditions are restored

Question 14

How are alternative stable states driven?

Answer 14

By species interactions

- excluding ecosystem engineers as drivers of succession

Question 15

What are regime shifts?

Answer 15

Caused by the removal or addition of strong interactions that maintain a community type

Question 16

What is one of the strongest forces behind community change?

Answer 16

Human actions