Lecture 3- Causes Of Local Diversity

Question 1

Define competitive exclusion

Answer 1

A process by which the most competitive species within a given habitat drive the others to extinction

Question 2

What are the two overarching theories for the processes that allow species co-existence?

Answer 2

1. Equilibrium

2. Non-equilibrium

Question 3

What are the three equilibrium controls on local biodiversity?

Answer 3

1. Niche concept
2. Heterogeneity
3. Island biogeography

Question 4

What are the two non-equilibrium theories for species coexistence?

Answer 4

1. Diversity productivity relationship

2. Intermediate disturbance hypothesis

Question 5

In equilibrium theories, how is community diversity regulated?

Answer 5

Competition and evolution

Question 6

In equilibrium theories, how are conception and evolution regulated?

Answer 6

Through STEADY STATE

Question 7

In non equilibrium theories, how is community diversity thought to be maintained?

Answer 7

Processes that prevent competitive exclusion

Question 8

Describe the niche concept (equilibrium theory)

Answer 8

Specialisation into specific environments allows co existence , as utilisation of different resources causes limited competition.

Question 9

Explain the heterogeneity concept (equilibrium theory)

Answer 9

Then more diverse a habitat, the greater the available niches and therefore more space for specialised organisms. This then leads to the niche concept

Question 10

What are the problems associated with the niche-heterogeneity concept?

Answer 10

Only zoological as the needs for plants are fairly HOMOGENOUS
Resource partitioning Is not a strict process for all niches

Question 11

Explain the island biogeography concept (equilibrium theory)

Answer 11

The species present on an island are directly linked to the island area and isolation from the continent. Smaller populations in smaller areas are more likely to go extinct, as forces fo extinction DECREASE with island size

Question 12

Explain the link between immigration and extinction on an island

Answer 12

The closer the island, the greater the immigration and introduction of new species within the environment. However, this occurs up to a THRESHOLD, at which competition and predation act

Question 13

Explain the link between species richness and extinction rates on an island

Answer 13

The greater the species richness, the greater the extinction rate from increased competition and predation

Question 14

What is the link between species richness and area?

Answer 14

Species richness increases with area, with smaller populations in smaller areas more likely to go extinct. This is because forces of extinction DECREASE WITH SIZE

Question 15

Where is the equilibrium point between extinction and immigration on an island?

Answer 15

Multiple equilibrium points exist on islands depending on the balance between island area and immigration

Question 16

Explain the diversity productivity relationship (non equilibrium theory)

Answer 16

Peak diversity occurs at intermediate productivity as there is maximum resource avaliability, as at peak productivity dominat species cause competitive exclusion and a decrease in diversity.

Question 17

What is the name for conditions of medium productivity and maximal diversity

Answer 17

The diversity productivity sweetspot

Question 18

Explain the intermediate disturbance hypothesis (non-equilibrium theory)

Answer 18

Disturbances create a FLUCTUATING ENVIRONMENT, which prevents dominant species becoming prevent ant and causing competitive exclusion.

Question 19

Explain levels of diversity at:low,medium,high disturbance levels

Answer 19

Low disturbance= low diversity and competitive exclusion
Medium disturbance= max diversity as competitive exclusion does not occur
High disturbance= low diversity with few species able to tolerate conditions

Question 20

How is local diversity determined?

Answer 20

By the balance between extinction and immigration forces