Evidence of Evolution by Natural Selection (Ch. 22) Dodo bird

Evidence supporting evolution Fossil record Anatomical record Molecular record Artificial selection

Fossil record Layers of sedimentary rock contain fossils – new layers cover older ones, creating a record over time – Show that a succession of organisms have populated Earth throughout a long period of time

Formation of sedimentary strata containing fossils 1 Rivers carry sediment to the ocean. Sedimentary rock layers containing fossils form on the ocean floor. 2 Over time, new strata are deposited, containing fossils from each time period. 3 As sea levels change and the seafloor is pushed upward, sedimentary rocks are exposed. Erosion reveals strata and fossils. Younger stratum with more recent fossils Older stratum with older fossils

A gallery of fossil types (a) Dinosaur bones being excavated from sandstone (g) Tusks of a 23,000-year-old mammoth, frozen whole in Siberian ice (e) Boy standing in a 150-million-year-old dinosaur track in Colorado (d) Casts of ammonites, about 375 million years old (f) Insects preserved whole in amber (b) Petrified tree in Arizona, about 190 million years old (c) Leaf fossil, about 40 million years old

Support (proof?) for a VERY old Earth.

A dragonfly fossil from Brazil, more than 100 million years old

The Geologic Record

Evolutionary change in horses Millions of years ago Equus Hyracotherium Mesohippus Merychippus Nannippus Body size (kg)

Evolution of birds Smithsonian Museum, Washington, DC Archaeopteryx – lived about 150 mya – links reptiles & birds

? ? ? ? Where are the transitional fossils? Land Mammal Whales, you ask...

A transitional fossil linking past and present Oh. Here they Are!

2006 Fossil Discovery of Early Tetrapod Tiktaalik – “missing link” from sea to land animals

Anatomical record Homologous structures – similarities in characteristics resulting from common ancestry

Homologous structures Similar structure Similar development Different functions Evidence of close evolutionary relationship – recent common ancestor

spines tendrils succulent leaves colored leaves Homologous structures leaves needles

Analogous structures  Separate evolution of structures  similar functions  similar external form  different internal structure & development  different origin  no evolutionary relationship Solving a similar problem with a similar solution Don’t be fooled by their looks!

Convergent evolution Flight evolved in 3 separate animal groups – analogous structures Does this mean they have a recent common ancestor?

Convergent evolution of analogous burrowing characteristics

Convergent evolution  Fish: aquatic vertebrates  Dolphins: aquatic mammals  similar adaptations to life in the sea  not closely related Those fins & tails & sleek bodies are analogous structures!

Parallel Evolution Convergent evolution in common niches – Similar ecological roles in similar environments, Similar adaptations were selected – but are not closely related marsupial mammals marsupial mammals placental mammals placental mammals

Parallel types across continents NichePlacental MammalsAustralian Marsupials Burrower Mole Anteater Mouse Lemur Flying squirrel Ocelot Wolf Tasmanian “wolf” Tasmanian cat Sugar glider Spotted cuscus Numbat Marsupial mole Marsupial mouse Anteater Nocturnal insectivore Climber Glider Stalking predator Chasing predator

Vestigial organs Structures that serve little or no function – remnants of structures that were functional in ancestral species – deleterious mutations accumulate in genes for non-critical structures without reducing fitness snakes & whales — remains of pelvis & leg bones of walking ancestors eyes on blind cave fish human tail bone This is not LaMarck’s loss from “disuse”!

Vestigial organs Hind leg bones on whale fossils Why would whales have pelvis & leg bones if they were always sea creatures?

Comparative embryology Similar embryological development in closely related species – all vertebrate embryos have similar structures at different stages of development gill pouch in fish, frog, snake, birds, human, etc.

Comparative hemoglobin structure Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans LampreyFrogBird Dog MacaqueHuman Why does comparing amino acid sequence measure evolutionary relationships?

Artificial selection A rtificial breeding can use variations in populations to create vastly different “breeds” & “varieties” “descendants” of the wolf “descendants” of wild mustard

Natural selection in action Insecticide & drug resistance – insecticide doesn’t kill all individuals – resistant survivors reproduce – resistance is inherited – insecticide becomes less & less effective

Evolution is not goal-oriented An evolutionary trend does not mean that evolution is goal-oriented. Surviving species do not represent the peak of perfection. There is compromise & random chance involved as well Remember that for humans as well! Evolution is not the survival of the fittest. Rather it is the survival of the just good enough.

Peppered Moths Dark vs. light variants Year% dark% light

Any Questions??

Review Questions

1.A complete fossil record 1.Exists because of the great preservation in ocean sediment 2.Exists because of the solidification of minerals around organisms 3.Is available because of the small location in which all organisms used to live 4.Exists because organisms that die become embedded in the soil to form rocks 5.Does not exist.

2.The similarity of insect wings and bird wings is an example of A.Behavioral adaptations B.Geographic isolation C.Adaptive radiation D.Convergent evolution E.Divergent evolution

3. The human appendix is an example of 1.A balanced polymorphism 2.Divergent evolution 3.Convergent evolution 4.A vestigial structure 5.A homologous structure