_____________ organs, _____________ genes
DESCRIPTION
Evolution by natural selection can create adaptation, that tangible sense of “designed for function”. But it is also an historical process – only works with existing variation, has a characteristic “makeshift” quality. _____________ organs, _____________ genes. “Panda’s thumb”. - PowerPoint PPT PresentationTRANSCRIPT
Evolution by natural selection can create adaptation, that tangible sense of “designed for function”
But it is also an historical process – only works with existing variation, has a characteristic “makeshift” quality
_____________ organs, _____________ genes
“Panda’s thumb”
The late evolutionary biologist Stephen J. Gould loved to dwell on this historical component of design in nature
A favorite example – the “thumb” of the Giant Panda
http://www.athro.com/evo/pthumb.html
_____bone – radial sesamoid
Ratites: Ostrich, cassowary, moa (extinct) , rhea, emu, kiwi, tinamou
http://www.camacdonald.com/birding/Sampler1.htm
George C. Williams’ favorite example
Williams, G.C. 1992. Natural selection: domains, levels, and challenges. Oxford Press.
Vas deferens
My favorite example – why is the slime green??
Recall that much of the energy in sunlight is in the _____________portion of the visible spectrum
Does plant greenness relate to the use of this energy?
Light energy is obtained by the absorption of photons (light “particles”) by PIGMENTS Photosynthetic pigment molecules include
Chlorophyll a, b, cCarotenoidsPhycobilins
Each pigment has its own ______________ SPECTRUM
The rate of photosynthesis is also a function of wavelength as a result of the pigments – __________ SPECTRUM
So, plants use light in the visible range where most energy is, but there is a ____ in absorption in the green-yellow range. So that’s why plants are green – that light is __________, so it is reflected (so we see it). Ok, but this means lots of energy is ____________________?
Maybe – a mistake? Historical accident? Some _____________ (photosynthetic bacteria) have _____________
If plants were fully utilizing sunlight, what color would they be?So, why the slime is green is still a mystery.
2,3 - chlorophyll a,b4 - phycoerythrobilin5 – beta-carotene
So design by natural selection has a distinctive historical “signature”
While many details of organisms in nature seem beautifully, exquisitely adapted for survival, they also need to be given a history - how did it get there?
In fact, many details really don’t seem to make much “sense” without that history
Extinction – loss of species – speciation _______diversity, extinction ________ it
The fossil record documents the existence of many species that _________________
http://www.xs4all.nl/~kwanten/http://www.dinofish.com/
Coelacanth
Ginkgo
Occasionally, a species known first from fossils has been found still existing.
Tree of life has many aborted branches
http://home.socal.rr.com/wangsong/CaniEvol/CaniEvol.html
Canidae – dogs: many more ______ than ______
Extinction rates have been ________ over time, with occasional “_____” extinctions
3.4
Despite this, there have been long term _______ in measures of diversity
Often _________ is suspected
Adaptive Radiation
Speciation rates are ______ as well, especially within groups
Adaptive radiation – “______” production of descendant species
Probably a result of new adaptive “opportunity”1. 2. 3.
Classic island examples
_________ finches
http://www.rit.edu/~rhrsbi/GalapagosPages/DarwinFinch.html
Adaptive radiation
Sato et al. 2001
Mass extinctions followed by major biotic shifts
1. _________ extinction (250 MYA)
2. __________ extinction (65 MYA)
Before -amphibians and fernsAfter – reptiles and gymnosperms
Before – reptiles and gymnospermsAfter – mammals and angiosperms
http://www.dinosaursinart.com/http://gpc.edu/~pgore/images/mastodon.gif
Adaptive radiation
Adaptive innovations
“Cambrian explosion” – innovation?
Large category, most important traits probably qualify (e.g., photosynthesis, nucleus, multicellularity, flowers…)
Adaptive radiation
By 543 MYA – all extant animal phyla38 body plans from 3 in 20MY
http://instruct1.cit.cornell.edu/courses/bionb424/students/ckr5/phylogeny.html
Whales (Cetacea)
Tremendous diversification in a short time
Where did they come from?
Jean-Renaud Boisserie / UC Berkeley
Whales are _________ most closely related to the ___________, in the Artiodactyls, the even-toed ungulates. Horses and rhinos are Perissodactyls, odd-toed ungulates.
What are the Archaeocetes?
http://evolution.berkeley.edu/evosite/evo101/IID2Understanding2.shtml
Archaeocetes
http://www.sci.tamucc.edu/~wcrc/cetaceans/extinct/archaeocetes.html
Pakicetidae 50 MYA
Ambulocetidae 50 MYA
Remingtonocetidae 45 MYAProtocetidae
Morphological reconstruction of the Cetacea phylogeny (no DNA for extinct taxa)
http://palaeo.gly.bris.ac.uk/Palaeofiles/whales/archaeoceti.htm
Whales are a striking example of how evolution can, relatively quickly, result not only in dramatic radiation, but extreme changes in phenotype.
Consider: _______ are more closely related to _______ than to _______.
What was the “force” that caused this?
End Part 2