Island Biogeography

Question 1

What is an oceanic island?

Answer 1

Water surrounded, the result of volcanic activity. Was never connected to mainland. (i.e. Mariana Islands)

Question 2

What is a continental island?

Answer 2

Was connected to mainland but now isolated due to sea level change. (i.e. UK)

Question 3

What is Wallaces line? (1823-1913)

Answer 3

1. Wallace studied the islands of Bali and Lombok and noted that they had similar climate and size and were 30km apart.
2. However, Bali has tigers, monkeys and bears and Lombok has birds of paradise, very different taxa.
3. They’ve never been joined and fast currents run between the islands as a biogeographic barrier.
4. Bali is continental and Lombok is oceanic which explains why there are only birds on Lombok as it’s easier to disperse.

Question 4

What are the three island processes?

Answer 4

1. Immigration (arrival)
2. Speciation (modification)
3. Local extinction on island (if it survives elsewhere - Extirpation)`

Question 5

What is community (species richness) equilbrium?

Answer 5

1. When an island is formed there are no species
2. Population will increase from immigration and speciation
3. Some colonists will go locally extinct from competitive predation or change in niche
4. Eventually rate of species will balance net gain and loss - equilibrium

Question 6

What is species-area relationship?

Answer 6

Larger islands have more species than smaller islands

Question 7

What is dwarfism?

Answer 7

The process of large animals evolving and reducing body size when population range is limited to a small environment. This is caused by a niche of resources, causing stunted growth and reduced reproduction.`

Question 8

Give an example of dwarfism.

Answer 8

Pygmy Mammoth on channel islands.

Question 9

What are the implications of dwarfism?

Answer 9

Introduction of predators would mean dwarf species would be unable to defend

Question 10

What are the implications of dwarfism?

Answer 10

Introduction of predators would mean dwarf species would be unable to defend

Question 11

What is gigantism?

Answer 11

Size of a species grows rapidly in comparison to mainland species, due to the absence of predators, size is used for competitive resources

Question 12

Give an example of gigantism.

Answer 12

Giant tortoise, Galapagos

Question 13

What are vestigal features?`

Answer 13

A feature that no longer has any purpose, often had a purpose but species has evolved to not need it. For example; boa constrictors have back legs.