Adaptive radiation

Question 1

When do generalists compete well?

Answer 1

If resources are unpredictable year-to-year or season-to-season

Question 2

When do specialists complete well?

Answer 2

When resources are stable year-to-year or season-to-season

Question 3

The average rate of a new species on the Galapagos is 1 species every 240,000yrs.
What are the assumptions being made here?

Answer 3

> radiation is as old as the oldest islands

> no species have gone extinct

Question 4

What is adaptive radiation?

Answer 4

Process in which orgs diversify rapidly from an ancestral species into a multitude of new forms

Question 5

What are the 3 main features of adaptive radiations?

Answer 5

> high diversity
wide range of niches occupied (diets, feeding adaptations, behaviours, body sizes, habitats)
occurs over a geologically short period

Question 6

What is the Silversword Alliance?

Answer 6

Adaptive radiation of 50 species of plant in the Hawaiian islands

• best known = Mount Haleakala Silversword
• grow everywhere form arid volcano craters to rainforest bogs

1 new species every 100,000 yrs

Question 7

Why study islands?

Answer 7

Act like continents but on smaller scale

= easier to study

Question 8

What are the wide range of forms & eclogues of lemurs in Madagascar?

Answer 8

Omnivores, frugivores, incesctivores & herbivores

Aboreal & terrestrial

Nocturnal & diurnal

Social & asocial

Question 9

When does adaptive radiation ‘take off’?

Answer 9

When there is opportunity

• little/no competition for resources
  e. g. vacant island

Question 10

What happened at the Cretaceous-Tertiary

(K-T) boundary (68mya)?

Answer 10

Dinosaurs etc disappeared

Question 11

What is the evidence for an 6 mile asteroid impact causing the K-T extinction?

Answer 11

Spherules
Shocked quartz
Giant tsunami deposits in Texas
Chicxulub

Question 12

What affect do mass extinctions have on ecosystems?

Answer 12

Wipe out established flora & fauna
= provides opportunities for survivors to colonise disturbed environments
–> radiate

Question 13

When did mammals originate?

Why is this?

Answer 13

66mya

Extinction of dinosaurs
= less competition
= mammals radiate

Question 14

How do fossils & molecular clocks show birds radiating greatly?

Answer 14

1-12 species after impact

–> 10,00 living species

Question 15

What is another way adaptive radiations can occur?

Answer 15

If orgs hit upon novel ways of making a living

e.g. terrestriality, flight, flowers

Question 16

How was moving onto land beneficial?

Answer 16

Plants could radiate into unoccupied habitats

• > creates niches for herbivores = they radiate
• > creates niches for predators = they radiate

Question 17

What is punctuated equilibrium?

Answer 17

Bursts of evolution when there’s opportunity
-> once species appear in fossil record the population will become stable
= showing little evolutionary change for most of its geological history