MS130 - Biology
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Pete Markiewicz

Week 04

Web Links Week 04 - Evolution

Dinosaur to dino-human - what if the asteroid hadn't hit?
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DEFINITION AND HISTORY OF EVOLUTION

Difference between evolution (observation) and evolutionary theory (hypothesis)

Evolutionary theory before Darwin

Charles Darwin's (particular) theory of evolution - by NATURAL SELECTION
Motivation: The Voyage of the Beagle - http://www.aboutdarwin.com/voyage/voyage01.html

 

Famous Books:
On the Origin of Species - 1859
The Descent Of Man, And Selection In Relation To Sex (1871)
Expression Of Emotions In Man And Animals (1872).

MECHANISM OF EVOLUTION - DARWINISM OR "NATURAL SELECTION"

Mechanism of evolution by natural selection (Darwinism)

 

EVIDENCE FOR EVOLUTION AND DARWIN'S MECHANISM OF EVOLUTION

Microevolution observed in the wild

Long-legged Cane Toads evolve, continue conquest of Australia
"...Cane toads, the poisonous, invasive pests that have caused mayhem in Australia, are evolving longer legs, enabling them to hop further and invade new territory faster...Longer legs make for a faster toad. Over three days, the invasion-front toads travelled about 500 metres further than the shorter-legged stragglers. The advantage for these toads is access to fresh territory with a good food supply and less competition, which could be the factor driving selection for longer legs..."
 http://www.newscientist.com/article.ns?id=mg18925394.700&feedId=online-news_rss20

"Transitional" organisms (missing links)

Fishy land-beast shows how life left the water (credit: Nature)
 http://www.livescience.com/animalworld/060405_fish_evolution.html

Homology between organisms - front limbs of tetrapod vertebrates

Vestigial organs (organs which are no longer used by organism atrophy)
 http://www.livescience.com/animalworld/top10_vestigial_organs.html

Chickens CAN grow teeth
 http://www.livescience.com/animalworld/060222_chicken_teeth.html

GALLERY - SELECTIVE BREEDING AND RELATED EVOLUTIONARY EXAMPLES

Embryo comparisons (early embryos all look alike, diverge later)
Explained as having all vertebrates using the same basic DNA "program" to generate a body, which is modified by additional "modules" in each organism. This program was present in the ancestor of all vertebrates (Amphixous-like?)
 http://www.starlarvae.org/SL_graphics/embryo_comparisons.jpg

"Ontogeny" (embryonic development) resembles "plylogeny"

 

Evolution in virtual worlds - show that Darwinism works on computer software as well as DNA

SPECIATION

Mechanisms of evolution leading to new species - http://en.wikibooks.org/wiki/Speciation

SEXUAL SELECTION IN EVOLUTION

Definition of sexual selection - features determined by mate choice rather than environmental advantage

OTHER EVOLUTIONARY THEORIES

"Intelligent Design" - an alternative theory of evolution with direction of evolution by a "higher force"

TRENDS IN EVOLUTION

NO DIRECTION - evolution does "whatever works" - no "master plan", "progress", "advancement" or "goal"

Fish capable of human-like reasoning - in one narrow domain (pecking order)
http://www.livescience.com/animalworld/070124_fish_brains.html

Neoteny - (retention of larval features in adult)

Convergent Evolution

Microevolution - http://en.wikibooks.org/wiki/Microevolution

Macroevolution

Trends based on environment

EVOLUTION AND MASS EXTINCTIONS - A NON-DARWINIAN FORCE

A non-Darwinian force in evolution is mass extinctions. These events happen very rarely and result in ultra-extreme environmental conditions. This makes it impossible for natural selection to happen for these events. Survival of a mass extinction is a matter of pure chance, not adaptation. The "better" organism may lose to one that just happens to have features allowing survival.

Features of mass extinctions

Sources of mass extinctions

Mass extinctions in the last 250 million years

EVOLUTION AND INTELLIGENCE

"Bird brains" shake up scientific theories about the evolution of intelligence
"...Scientists once assumed that intelligence evolved out of physical need - animals got smart in order to exploit natural resources. But the brainpower of birds suggests that intelligence is actually a byproduct of complex social interactions. Living in a group requires an animal to juggle lots of information about its peers. So it's not a coincidence that the smartest creatures are also the most social..."
http://www.boston.com/news/globe/ideas/articles/2007/09/16/eggheads/

FUTURE EVOLUTION

Evolution has not "stopped"

Evolution not always "upward and onward"

Future evolution

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