Darwin’s Theory of Evolution Darwin Presents his Case Image from: Biology by Miller and Levine; Prentice Hall Publishing©2006

results in changes in the inherited characteristics of a population. WHAT IS DARWIN’S THEORY? Over time, NATURAL SELECTION results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment. How Does Evolution Really Work?

WHAT IS DARWIN’S THEORY? SURVIVAL OF THE FITTEST = Organisms which are better adapted to their environment tend to produce more offspring than organisms without those traits. http://www.poster.net/bedard/bed202.jpg

WHAT IS DARWIN’S THEORY? OVERPRODUCTION of OFFSPRING Capacity to over-reproduce seems characteristic of all species. http://www.biospheres.com/photogallery2ag/images/ladybugs_jpg.jpg http://atthecreation.com/DEER/too.many.deer.jpg

WHAT IS DARWIN’S THEORY? STRUGGLE FOR EXISTANCE means that members of each species must compete for food, space, and other resources. http://www.wasatchcomputers.net/gallery/elk_fight.jpg

WHAT IS DARWIN’S THEORY? GENETIC VARIATION is found naturally in all populations Image from www.biologyzone.com http://www3.nationalgeographic.com/animals/images/primary/zebra-herd.jpg

WHAT IS DARWIN’S THEORY? Some organisms in a population are less likely to survive. http://www.cartoonstock.com/newscartoons/cartoonists/rrs/lowres/rrsn69l.jpg

IMPORTANT TO REMEMBER ! POPULATIONS evolve NOT INDIVIDUALS. NATURAL SELECTION only works on heritable traits. A trait that is favorable in one environment may be useless or detrimental in another.

DESCENT WITH MODIFICATION WHAT IS DARWIN’S THEORY? DESCENT WITH MODIFICATION suggests that each species has descended with changes from other species over time. This idea suggests that all living species are related to each other and that all species, living and extinct, share a common ancestor.

EVIDENCE OF EVOLUTION: ________________ 3. _______________ 4. _______________ 5. _______________ 6. _______________ 7. _______________ Artificial selection Fossil record Geographic Distribution Anatomical homologies Embryology Molecular homologies Can see Natural selection happen

ARTIFICIAL SELECTION WORKS Nature provides the variation through mutation and sexual reproduction and humans select those traits that they find useful EX: We have selected for and bred cows to produce more milk, turkeys with more breast meat, etc. http://www.pp3moo.com/hm2cow.jpg http://lazerbrody.typepad.com/photos/uncategorized/turkey.gif

WE’VE DONE IT WITH PLANTS BIOLOGY by Campbell and Reece Prentice Hall Publishing©2005

WE’VE DONE IT WITH ANIMALS If humans can select for beneficial traits, why can’t nature? If artificial selection can achieve so much change in relatively short time, why can’t major changes happen over thousands of generations? http://www.windows.ucar.edu/earth/geology/images/dogs_sm.jpg

How Do We Know Evolution Happens? The Fossil Record provides evidence that organisms have changed over time. http://www.bbc.co.uk/schools/gcsebitesize/img/bifossils.gif

If evolution has happened, we should be able to find evidence of evolution in the fossil record AND WE HAVE ! http://en.wikipedia.org/wiki/Image:Tiktaalik_BW.jpg BBC Tiktaalik video http://evolution.berkeley.edu/evosite/lines/IAtransitional.shtml

Lots of TRANSITIONAL FOSSILS have been found Scientific American; Dec 2005; Vol 293; p100-107

GEOGRAPHIC DISTRIBUTION = BIOGEOGRAPHY If Darwin’s theory is correct you would expect to find closely related yet different species living in a geographic region as they spread into nearby habitats and evolve. That’s EXACTLY what we do see!

The beaks of Galapagos finches have http://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/T014608A.gif GALAPAGOS FINCHES The beaks of Galapagos finches have adapted to eating a variety of foods

GALAPAGOS TORTOISES Tortoises adapted to different habitats as they http://www.newtonswindow.com/problem-solving.htm GALAPAGOS TORTOISES Intermediate vegetation Intermediate necks Little vegetation Long necks Image from: BIOLOGY by Miller and Levine; Prentice Hall Publisher©2006 Lots of vegetation Short necks Tortoises adapted to different habitats as they spread from the mainland to the different islands. = DIVERGENT EVOLUTION = ADAPTIVE RADIATION

If Darwin’s theory is correct you would also expect to find different species living in far apart geographic regions but similar habitats becoming more alike as they adapt to similar environments. That’s EXACTLY what we do see!

BOTH LIVE IN FOREST ECOSYSTEMS Adapted to similar environments, but evolved independently from different ancestors. SUGAR GLIDER in Australia is a marsupial more closely related to Kangaroos than North American FLYING SQUIRRELS because its ancestors were marsupials.

Whales and sharks have a similar body design http://www.flmnh.ufl.edu/fish/gallery/descript/TigerShark/scars.JPG http://news.bbc.co.uk/2/shared/spl/hi/guides/456900/456973/html/nn1page1.stm Whales and sharks have a similar body design even though they are very different organisms (one is a fish; the other, a mammal) because they have independently adapted to living in a similar environment. = CONVERGENT EVOLUTION

HOMOLOGOUS STRUCTURES-Forelimbs of all mammals share same arrangement of bones that can be traced to same embryological origin BIOLOGY by Campbell and Reece Prentice Hall Publishing©2005

EVOLUTION explains why certain characteristics in related species have an underlying similarity. Section 15-3 Turtle Alligator Bird Mammal Ancient lobe-finned fish

VESTIGIAL ORGANS Some homologous structures are vestigial and have no useful function even though they are still present. Examples: Hipbones and pelvis in whales and boa constrictors Cecum (appendix) in humans Skink legs http://www.txtwriter.com/backgrounders/Evolution/EVpage12.html

Most mammals have a pouch between their small and large intestine that contains bacteria to digest plants called a cecum. In humans the cecum is shrunken and unused. It is our appendix http://www.medicalgeo.com/images/appendix.gif

EMBRYOLOGY Development of vertebrate embryos follows same path Image from: http://calspace.ucsd.edu/virtualmuseum/litu/03_3.shtml

MOLECULAR HOMOLOGIES All life forms share same genetic machinery (DNA & RNA) Universal genetic code Important genes share highly conserved sequences

Similarities in protein sequences suggests similarities in DNA Image from: Modern Biology by Holt, Rinehart, and Winston

DNA and protein sequences MOLECULAR HOMOLOGIES Similarities in DNA and protein sequences suggest relatedness Image from: BIOLOGY AP EDITION by Campbell and Reece; Prentice Hall Publishing©2005

Similarities in karyotypes suggest an evolutionary relationship Human- 46 chromosomes Chimpanzee- 48 chromosomes Similarities in karyotypes suggest an evolutionary relationship Human: http://www.nationmaster.com/wikimir/images/upload.wikimedia.org/wikipedia/en/thumb/1/18/300px-Human_karyogram.png Chimpanzee: Middle School Life Science , published by Kendall/Hunt.

Even differences show relatedness Human- 46 chromosomes Chimpanzee- 48 chromosomes Even differences show relatedness Chimpanzees have 2 smaller chromosome pairs we don’t have Humans have 1 larger chromosome pair (#2) they don’t have. Human: http://www.nationmaster.com/wikimir/images/upload.wikimedia.org/wikipedia/en/thumb/1/18/300px-Human_karyogram.png Chimpanzee: Middle School Life Science , published by Kendall/Hunt.

Remember: Protective TELOMERE sequences found at ends of chromosomes http://joannenova.com.au/Speaking/Morslids.html

→ → → 2. TELOMERES IN MIDDLE Human chromosome is only human chromosome that has telomere sequences at the ends BUT ALSO IN THE MIDDLE . . . suggesting it was made by joining two other chromosomes together. → → http://www.evolutionpages.com/chromosome_2.htm

→ EXTRA CENTROMERE _________________ Chromosome #2 has a second inactive centromere region . . . suggesting it was made by joining two other chromosomes together. Which chromosomes? → http://www.evolutionpages.com/chromosome_2.htm

________________________ BANDING PATTERN MATCHES ________________________ If you take the two smaller chromosomes they have that we don’t, and place them end to end, the banding pattern is identical to human chromosome #2 http://www.evolutionpages.com/chromosome_2.htm

Slide by Kim Foglia@ http://www.explorebiology.com/

Slide by Kim Foglia@www.biologyzone.com