Evolution 101Understanding Evolution for the Layperson

Part IIJack Krebs

April 13, 2006

Co-sponsored byThe Shawnee Mission Universalist Unitarian Church

AndKansas Citizens for Science

Introduction

Jack Krebs

• President, Kansas Citizens for Science• Member, Kansas Science Standards Writing Committee (High

School Life Science sub-committee chairperson)• Longtime public school educator as a teacher, technology

director, and curriculum director.• Undergraduate degree in anthropology

Main source for this part of this course:

• The Understanding Evolution website at UCMP.

Resources at KCFS News

http://www.kcfs.org/kcfsnews

http://www.kcfs.org/kcfsnews/?page_id=26

Understanding Evolution

http://evolution.berkeley.edu/evosite/evohome.html

University of California Museum of Paleontology

The format of this class tonight

Outline for tonight:

1. Lines of evidence for evolution2. Common concerns about evolution3. Discussion

Take breaks as needed. We will take a three minute break at 8:30 forthose who may be ready to go, and then continue discussion until 9:00.

Discussion forum at KCFS website: KCFS Forums. Details are on yourhandout.

I will expect civil, thoughtful, and on-topic participation from all of us.

The Pyramid of Knowledge

Primate family tree

Human beings, like all animals, have evolved fromancestor species. We are related by common descentto all the rest of life on earth.

Human Evolution

Human Migration

http://www7.nationalgeographic.com/ngm/0603/feature2/map.html

How long ago did it happen? How can we tell?

Stratigraphy and radiometric dating

Read more on dating rocks at the Utah Geological Survey athttp://www.ugs.state.ut.us/surveynotes/gladasked/gladage.htm

Geographical distribution

Creatures similar to existing creatures are found in the samegeographical area

Creatures that vary from lowlands to mountains are more similarlocally than lowland creatures distributed worldwide vs. mountaincreatures worldwide

Migration of creatures is also documented in the fossil record

Because of continental drift, fossils may appear separated nowbut were not at the time they were formed

The Tasmanian Wolf

The Tasmanian Wolf (extinct for about 75 years) is a marsupial fromTasmania, related to kangaroos, not wolves.

Its similarity to wolves in looks and behavior is an example ofconvergent evolution - the Tasmanian Wolf evolved to fill the nichetaken by wolves in other environments.

www.amnh.org

www.americanheadhunters.com

Ancient species

Homologies

“Characteristics in different organisms that are similar because theywere inherited from a common ancestor that also had thatcharacteristic.”

Homologies are distributed in nested hierarchies. Note thathomologies inside nested hierarchies and the lack of homologiesoutside of nested hierarchies are both evidence for evolution.

Analogies and convergent evolution

Bird and bat wings are analogous—that is, they have separateevolutionary origins, but are superficially similar because theyevolved to serve the same function. Analogies are the result ofconvergent evolution.

Comparing homologies and analogies

Interestingly, though bird and bat wings are analogous as wings,as forelimbs they are homologous. Birds and bats did not inheritwings from a common ancestor with wings, but they did inheritforelimbs from a common ancestor with forelimbs.

Why convergent evolution?

1. The existing environment and the laws of physics are thesame for all organisms, and therefore similar adaptationsare successful.

2. For example, tuna (fish), whales (mammals), and penguins(birds) all have a stream-lined shape because of the physicsof moving through water.

3. Sometimes prior inheritance (for instance, four limbs)provides both a constraint and a starting point for differentsolutions (for example, bat wing and bird wing.)

Vestigial features and other signs of modification

Developmental evidence

http://www.talkorigins.org/faqs/comdesc/section2.html

Evolution of the middle ear

From embryological studies it is known that two bones of adeveloping reptile eventually form the quadrate and the articularbones in the hinge of the adult reptilian jaw (first reported in1837 by the German embryologist Karl Reichert). However, inthe marsupial mammalian embryo, the same two structuresdevelop, not into parts of the jaw, but into the anvil and hammerof the mammalian ear. (Talkorigins faq)

Cetaceans - Whales and dolphins

More on whales athttp://www.ucmp.berkeley.edu/mammal/cetacea/cetacean.html and athttp://www-personal.umich.edu/~gingeric/PDGwhales/Whales.htm

“Baleen whales have toothed ancestors

Toothed whales have full sets of teeth throughouttheir lives. Baleen whales, however, only possessteeth in the early fetal stage and lose them beforebirth. The possession of teeth in fetal baleenwhales provides evidence of common ancestry withtoothed whales and other mammals. In addition,fossil evidence indicates that the late Oligocenewhale Aetiocetus (left), from Oregon, which isconsidered to be the earliest example of baleenwhales, also bore a full set of teeth.

Again, these observations make most sense in anevolutionary framework where snakes have leggedancestors and whales have toothed ancestors.”

InvertebratesThe Museum of Invertebrate Paleontology at Kansas University

http://kumip.ku.edu/

<-- Trilobite fossil

Living now

mya

Trilobite evolution

Samples were obtained from every three million years [fromaround 500 mya]. The number of ribs of each species of trilobitechanged over time .

Some of these changes over time were so large that the animalsat the end of the series are assigned to a new genus!

Number of ribs

Time

Cellular homologies

The cell membrane

DNA

Genetic homologiesThree phylogenetic trees werereconstructed based on the DNAsequences of:

(a) 4700 bp of mitochondrialDNA,

(b) the testis specific protein onthe Y chromosome,

(c) noncoding regions of the globin gene.

All three trees show that humanand chimp DNA sequences aremore similar on average than arehuman and gibbon or human andorangutan sequences.

http://www.zoology.ubc.ca/~bio336/Bio336/Lectures/Lecture5/Overheads.html

Evidence in the present

Artificial breeding

Field studies

Experiments in the laboratory

Studies of particular genes

Misconceptions about evolution

http://evolution.berkeley.edu/evolibrary/misconceptions_faq

1. Young-earth creationism (Biblical literalism)

2. Old-earth creationism

3. The theory of evolution is fundamentally atheistic, andfundamentally incompatible with Christianity (andother theistic religions)

4. Those Christians who accept evolution are wrong -either confused about evolution or confused aboutChristianity, or living with a logical contradiction.

Facilitated Discussion Session

Civil, thoughtful, and on-topic behavior is expected.

Keep your questions and comments short.

Please respect my right and responsibility to manage the discussion.

Hand in your evaluations at the end.

Thanks for attending and

thanks to the Shawnee Mission Unitarian UniversalistChurch for sponsoring this event and inviting me to speak.