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Evolutionary scale
• Recall Linnaean taxonomy? We’ll utilize that system again here:»Kingdom» Phylum»Class»Order» Family»Genus» Species
Evolutionary scale• Micro level evolution: change occurs below the level of species,
w/in a population, e.g. changes in gene frequency, such as sickle cell allele in U.S., represents?
• Transient polymorphism, level is changing, albeit slowly• Accumulation of smaller scale changes can bring about a larger
scale change, called?• Macro level evolution: changes above the level of species,
resulting in a brand new species
Biological Species
• This brings about the question, what’s the criteria to be classified as the same species?
• Biological species: can reproduce viable offspring & (perhaps most important) do so on their own
• Speciation: the process whereby a single species diverges into 2 separate species, requires reproductive isolation (cutting off of gene flow)
Extrinsic & Intrinsic Reproductive Isolation
Extrinsic (geographical isolation)– Climate change– http://news.nationalgeographic.com/news/2006/05/bear-hybrid-phot
o.html– http://www.actionbioscience.org/evolution/barnosky.html
– Plate tectonics activity, ex. on Madagascar (where?):
http://www.sciencemag.org/cgi/content/summary/312/5776/969i
Intrinsic Reproductive Isolation
separated into pre- & post- zygotic mechanisms• What’s a zygote??• The product of the fusion of an egg & sperm
Pre-zygotic reproductive isolation
-Seasonal (temporal)isolation: breeding seasons don’t overlaphttp://www.sparknotes.com/biology/evolution/reproductiveisolation/section1.html
-Habitat isolation:occupy slightly difft habitats of same gen area
-Mechanical isolation: incompatible genitalia
-Gametic: sperm & egg are incompatible
Post zygotic reproductive isolation
• Major developmental prob’s (resulting in spontaneous abortion)
• Hybrid inviability: sickly, weak hybrid offspring• Hybrid sterility: hybrids incapable of reproducing• Hybrid hypofecundity: hypo means? Fecundity?• ≠ hybrid vigor (humans)• http://www.crystalinks.com/hybridization.html• http://news.nationalgeographic.com/news/2005/08/photogalleries/ligers_dynamite/
Pace of evolutionary change
Phyletic (Darwinian) gradualism: slow, incremental changes that accumulate over long periods of timePunctuated Equilibrium: (S.J. Gould): General stasis
interrupted by periods of rapid change (adaptive radiation or mass speciation events)
Adaptive radiation• Adaptive radiation (mass speciation): rapid
expansion & diversification of a grp of organisms as they adapt to a new ecological niche
• ~65 mya, an adaptive radiation event took place, what triggered it?
• Mass extinction of the dinosaurs. What type of organisms moved in to inhabit those ecolog. niches?
• http://news.softpedia.com/news/What-Caused-Dinosaurs-039-Extinction-39017.shtml
»Mammals!
Species types
• Generalized species: are able to adapt to a wide range of ecological niches
• Specialized species: require a narrowly defined set of environmental circumstances in order to survive
• Examples?
Evolutionary cycle
• Extinctions open up new ecological niche(s)• Generalized species moves in, adapts to new ecolog.
zone, begins adaptive radiation process• As generalized line diversifies, organisms become
increasingly specialized to particular niches w/in the zone
• Overspecialization makes the organisms susceptible to?• Extinction. Thus triggering a repeat in the cycle
– Startling reality: current RATE of extinction: fastest the Earth has ever seen, due to?
– http://exitstageright.wordpress.com/2008/10/18/no-species-lasts-for-ever-but-the-current-rate-of-extinction-is-terrible/
Human Taxonomic ClassificationKingdom & Subkingdom?
Kingdom: Animalia, based on?Heterotrophic & motile
Subkingdom: Metazoa: multicellularPhylum?
Phylum: Chordata, based on?have a notochord: hollow nerve cord, replaced by?
Subphylum: VertebrataHave a vertebral column
Class?
Hum. Taxon. Classification cont’d
Mammalia, based on? (hint from name)Having mammary glands to feed young
cohort: Eutheria, based on?Well developed placenta
As opposed to?Marsupials
Order?Primates!
Shared Traits
• Ancestral (primitive) traits: relative term, ancestral trait is simply very old & maintained unchanged over time
• Derived traits: more recent trait that has emerged, a modification of the ancestral form
• Which set is utilized to classify organism’s into the same group? (counterintuitive)
• Shared derived traits are used to classify organisms together
• Next we’ll examine some of the key shared derived
traits in primates
