Adaptive radiation Flashcards
What does the difference in size and beak shape reflect?
Different foraging strategies - ecological niche.
What was surprising about the birds darwin collected?
He thought they were all different species, but they were from the same lineage.
What are the closest relatives to the finches?
The tanagers from South America.
When do generalists compete well?
If resources are highly unpredictable year to year or season to season as it can rapidly shift to what is available.
When do specialists compete well?
When resources are stable year-to-ear and season to season.
What are the three features of adaptive radiation?
High diversity, wide range of niches occupied (diets, feeding adaptations, behaviours, body sizes etc) and occurs over a geologically short period - diversification of organisms into filling different ecological niches.
Honeycreeper finches?
SImilar to darwin finches but are more specialised for their lifestyles and more diverse.
What do honeycreeper finches evolve from?
Rosefinches.
SIlversword alliance?
Adaptive radiation of 50 species of plant in the Hawaiian islands. Grow everywhere - arid volcano craters to rainforest bogs.
Why are islands focused on within studies?
THey behave like continents but on a smaller scale and are easier to study. They show the same evolutionary processes but on a smaller scale - models.
Kangaroo?
Product of adaptive radiation.
What are colonization radiations?
Following a colonization of a vacant habitat, species can rapidly occupy empty niches.
What is strange about groups of organisms that have successful adaptive radiations?
They are not successful in the place they come from - niches already filled.
Why do adaptive radiations arise?
Due to opportunities - little or no competition for resources.
What is the creaceous-tertiary boundary?
When the dinosaurs and everything else went extinct.
What was found in the K-T boundary clay?
Iridium.
How does mass extinction have events similar to adaptive radiation?
Allows survivors to colonise disturbed environments and radiate. Similar to the galapagos but play out on the scale of continents.
What happens to birds at the K-T boundary?
They disappear and never show up again.
What happened to birds 10 million years after the K-T extinction?
New kinds of birds appeared - massive radiation.
What other organisms went extinct at the K-T boundary?
Lizards and snakes,
How have modern lizards formed?
Diversification to take advantage of niches left vacant by extinction of cretaceous lizards.
What is creative destruction?
Rise and spread of new tech. is linked to the destruction of old ones - economy is constantly renewing and destroying itself.
K-T extinction effects ?
75% of species eliminated but diversity rebounds rapidly and soon surpasses cretaceous diversity levels.
What are the 5 big mass extinctions?
Cretaceous-tertiary, triassic-jurassic, permian-jurassic, permian-triassic, late devonian and cambrian ordivician.
Cambrian explosion significance?
Biggest adaptive radiation of all time.
What were the features of the Cambrian explosion?
Dramatic increase in diversity, new kinds of organisms, happened very quickly - modern annelids, arthropods, chordates, mollusks.
What drives radiations in the Cambrian explosion?
Destruction of the old order - creative destruction - origins of new, complex, multicellular life may be in the extinction of the old.
How else can adaptive radiations occur?
If organisms hit upon entirely novel ways of making a living - they don’t wait for an opportunity, they create it.
What is terrestriality?
The evolution of life on land - migration of plants/arthropods etc. onto land creates a new ecosystem - one that doesn’t directly compete with the old, marine ecosystem.
What does the evolution of flight allow?
Opens up new niches - airborne predators, herbivores, fish-eaters etc. Animals can exploit low-density resources or seasonal resources.
What did evolution of flowers lead to?
A massive adaptive radiation of flowering plants in the Mid-Cretaceous.
What is punctuated equilibrium?
The idea that evolution occurs in fits and starts - bursts of creativity followed by periods where there are little changes.
What do the Cambrian explosion, the rise of the mammals and the evolution of flight and success of Darwin;s finches all have in common?
They can all be seen as adaptive radiations.
-summary- What are adaptive radiations?
Evolutionary bursts characterized by an increase in diversity, an increase in morphology and a range of niches occupied. They occur over a geologically short period of time.
-summary- When do adaptive radiations occur?
When groups exploit previously unavailable niches by colonizing a new environment, occupying niches left vacant by extinction, evolving new adaptations.
