ANTH/BIOL/GEOL/HIST/ PHIL 225 Class 13, Feb 22 Natural selection and adaptation Prof. Beall for Prof. Princehouse

Dr. Princehouse will hold extra office hours Wednesday 3-4 pm. Materials you have read or seen: Futuyama on natural selection and adaptation Video on natural selection Video on sexual selection Spandrels article (?Spaniels article) Materials you have brought to class: 3 written questions on the readings

EVOLUTION The process of biological change through time. The mechanism is natural selection. The outcome is organisms adapted to their environments.

Evolution by natural selection has three essential elements. Organisms have reproductive capacity that is rarely fulfilled because environmental resources are limited. Organisms vary in their ability to survive and reproduce. Mapping slide for the presentation (note that a background slide or a slide justifying the importance might precede this slide). A common mistake with mapping slides is to give the audience simply a boring and unmemorable vertical list of topics (including the names “Introduction” and “Conclusion” and “Questions”). Such a list is quickly forgotten after the slide is removed. On a mapping slide, take the opportunity to show a key image or perhaps a representative image for each major section of the presentation. In the second case, each image would be repeated on the first visual of the corresponding section and would remind the audience that they have arrived to a major section of the presentation’s middle. In regards to the names “Introduction” and “Conclusion,” every talk has those sections, and the names are ignored by audiences. So why state them? Also, for the divisions that you do have, find a logical and parallel grouping. Note that groups of two’s, three’s, and four’s are much easier to remember and are not so nearly intimidating as groups of five’s, six’s, and seven’s. See the example mapping slide in the textbook. (CSP, pages 55-56, 74-75, 86, 143, 147, and 148) Variation is heritable.

EVOLUTION BY NATURAL SELECTION: 3 postulates 1. Species are capable of producing offspring faster than their resources can support

Some estimate there were 3-5 billion passenger pigeons in North America when Europeans first arrived. The last one died in 1914. Old magazine illustration of hunters shooting Passenger Pigeons. Note the density of the flight. During migration, flocks could be 1 mile wide and 300 miles long, taking several hours to pass. https://www.geology.ucdavis.edu/iype/sept/passengerpigeon.jpg http://www.stanford.edu/group/stanfordbirds/text/essays/essaypix/Passenger_Pigeon.gif

EVOLUTION BY NATURAL SELECTION: 3 postulates 2. Variation among organisms affects their ability to survive and reproduce in their environment

“Any minute variation in structure, habits or instincts adapting that individual to the new conditions would tell upon its vigour and health” (C. Darwin, 1858, p. ) http://www.pbs.org/safarchive/images/img_5cool/galapagos/finches.gif http://home.comcast.net/~mkent595/Micro10.JPEG http://www.anth.ucsb.edu/faculty/walker/classes/anth105/index_files/image002.jpg

Variation is abundant. http://www.newscientist.com/data/images/ns/cms/mg20427342.500/mg20427342.500-1_300.jpg http://learn.genetics.utah.edu/content/begin/traits/images/hand_clasp.jpg http://images.mirror.co.uk/upl/m4/aug2009/6/1/baboon-2957207.jpg

EVOLUTION BY NATURAL SELECTION: 3 postulates 3. Variations are heritable

Variations are heritable. Hitch-hiker’s thumb is a recessive trait. Non-roller is a recessive trait. Height is influenced by heredity and environment. http://www.newscientist.com/data/images/ns/cms/mg20427342.500/mg20427342.500-1_300.jpg http://learn.genetics.utah.edu/content/begin/traits/images/hand_clasp.jpg http://images.mirror.co.uk/upl/m4/aug2009/6/1/baboon-2957207.jpg

Galapagos finch species depicted here have all arisen from a common ancestor, but have evolved a remarkable diversity of beak shapes and sizes as they have adapted to exploit different food sources Depth and breadth of beaks controlled by calmodulin locus. Length of beaks controlled by BMP4 locus. http://www.nature.com/nature/journal/v442/n7102/images/442515a-f1.2.jpg

The outcome of evolution by natural selection Species are well adapted to their environment Tremendous variety of species Tremendous variety of organisms

Well adapted organisms are the outcome of evolution by natural selection Organisms with variants that make them better able to survive contribute disproportionately to the next generation Over time, what happens? Descendent organisms have different features, structures, behaviors than their ancestors. Environmental inevitably changes.

Adaptations are the features that improve survival. Adaptations work. Adaptations are not perfect. The process is called natural selection, not natural perfection. New features of organisms result from natural selection

The Antarctic ice fish has several new features The Antarctic ice fish has several new features. It is related to the mackerel. Mackerel is like the ancestor fish. http://www.glaucus.org.uk/Mackerel.jpg As an adaptation to low temperatures, the Antarctic ice fish has no red blood pigments (haemoglobin) and no red blood cells. 80 Ice fish is descended from its ancestor with more modifications. http://www.underwatertimes.com/news.php?article_id=632194710

Icefish are pale because they don’t make myoglobin. The ice fish have adapted to low ambient temperature and have low body temperature. Icefish are pale because they do not make hemoglobin and don’t have red blood cells. They have ‘ice water’ in their veins. Icefish are pale because they don’t make myoglobin.

They adsorb oxygen from the water. How did this come about? The Antarctic ice fish has no red blood cells, no hemoglobin, and no myoglobin. How can they survive? They adsorb oxygen from the water. How did this come about? Water temperature dropped from about 68 ºF to < º30 F in the past 55 million years.

The genetic fossil record reveals the changes that caused the loss of hemoglobin and myglobin. One hemoglobin gene is nonfunctional and one is just gone. Myoglobin gene is non-functional. We can see the remnants of these genes. They have ‘gone extinct’.

Genetic changes resulted in the addition of antifreeze proteins in veins. Antifreeze proteins are necessary to prevent freezing solid. These antifreeze genes arose from a part of a gene that originally encoded a digestive enzyme. Part of that enzyme broke off and relocated to another place in the fish genome, replicated, and now makes antifreeze.

Icefish adaptations are examples of chance, necessity and tinkering. Improvised series of steps. Destruction of some old genetic code Tinkering with some code to make new genetic code. Icefish evolved from a warm-water, hemoglobin-dependent lifestyle to a very-cold-water, oxygen adsorbing, antifreeze-making lifestyle.

Coat color of rock pocket mouse is another example of descent with modification that has occurred in many species. MC1R gene has two alleles. Two copies of light allele results in sandy color of mice. MC1R allele in humans and our ancestors accounts for blonde and red hair in modern humans and our ancestors including Neanderthals.

Galapagos finch species depicted here have all arisen from a common ancestor, but have evolved a remarkable diversity of beak shapes and sizes as they have adapted to exploit different food sources Depth and breadth of beaks controlled by calmodulin locus. Length of beaks controlled by BMP4 locus. http://www.nature.com/nature/journal/v442/n7102/images/442515a-f1.2.jpg

High-altitude natives are a natural experiment of adaptation to an extreme, lifelong stress: hypoxia. Hypoxia is severe and unavoidable. All residents at a given altitude are exposed to the same ambient stress. All steps in the process of oxygen delivery are affected. Sample body slide from the second section of the presentation’s middle. For the first body slide of the second section, consider repeating the corresponding image from the mapping slide. Use the headline (left justified, no more than two lines) to say something about this topic. In the body of the slide, support that headline with images and parallel points (no more than four). See CSP, pages 116-117 and 147-151. 24

The Tibet Plateau has an average altitude of 15,000’ and is about 1500 x 600 miles in extent and is extremely stressful. Qinghai Qinghai-Tibet Plateau Ladakh Phala Lhasa Shigatse Nepal India NASA image Phala’s is at 15,200-17,500’ altitude; Shigatse is at 13,000’.

Hemoglobin carries less oxygen at high altitudes. % Oxygen saturation Cleveland 98% Pike’s Peak 80% . Tibetans have genotypes for high or low oxygen saturation of hemoglobin. Altitude, Tibetans % Oxygen Saturation 4200m BB genotype 88% 4200m AA genotype 78% http://www.pennhealth.com/health_info/images/19443.jpg

Women estimated to have genotypes for high oxygen saturation have more living children. Estimated Genotype Genotypic Means # Pregnancies/ livebirths # Living Children # Infant Deaths Low O2 Sat (AA) 4.6/4.5 1.6 1.7 High O2 Sat (AB) 4.9/4.8 3.6 0.6 High O2 Sat (BB) 4.8/4.6 3.8 0.3 27

The outcome of evolution by natural selection is organisms adapted to their environments. An adaptation is a characteristic that increases an organism’s chance of survival and reproduction. How do we identify adaptations? St. Mark’s Cathedral, Venice

STEPHEN JAY GOULD AND RICHARD C. LEWONTIN The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptationist Programme STEPHEN JAY GOULD AND RICHARD C. LEWONTIN http://www.aaas.org/spp/dser/evolution/history/spandrel

Spandrels of San Marco, Venice http://www.jssgallery.org/Essay/Venice/San_Marco/Basilica_San_Marco/Basilica_San_Marco_interior.htm

Adaptationist Program, I Why does this trait exist? What is the function of a given structure or organ? How has this trait contributed to reproductive success? What is the evolutionary history of the feature? Is the trait part of some other adaptive machinery?

Adaptationist Program, II Develop a functional hypothesis Develop a test or tests of that hypothesis Predict other, unknown, aspects of human biology and test those hypotheses, too

There are potential pitfalls. It is necessary to demonstrate the operation of natural selection rather than to assume it. Current function may not explain why a trait evolved. If we start with the wrong trait, we get the wrong explanation. http://australianmuseum.net.au/Uploads/Images/9667/DSC_0027_big.jpg

The Spaniels of St. Marx and the Panglossian Paradox: A Critique of a Rhetorical Program David C. Queller Quarterly Review of Biology 70 (4): 485, 1995 http://www.honeybet.co.uk/photos/doggroupweb.jpg