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

http://www.kamcom.co.nz/kiwi/index.html

Kiwi egg

Why would such a little bird have such a big egg?

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 ______

Horses (Equidae)

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

___________honeycreepers

Fleischer et al 1998

Hawaiian ____________

California _______

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

Whales (Cetacea)

Since <___MYA

Adaptive radiation

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

Possible transitional whale fossil Basilosaurus 35 MYA

Archaeocetes

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