Evidence of Evolution [15.2]

SPI 5 Apply evidence from the fossil record, comparative anatomy, amino acid sequences, and DNA structure that support modern classification systems.

• What are some of the way fossils are formed?• Transitional Species: description & examples• Vestigial Structures: description & examples• Comparative genomics• Comparative embryology

Fossils

• Compression/impression– Organism is squished or imprinted

into a 2D layer

• Permineralized fossils.– Minerals leech in from the ground

and replace soft tissue

• Casts and molds– Ground hardens around organism,

leaving the shape of it behind

• Preserved organic material– Ice, peat bogs, amber

• Homologous Structures – Characteristics that are similar because they share an evolutionary origin are homologous

• Analogous Structures – Characteristics that look similar but have independent evolutionary origins are analogous

Transitional Species

• If evolution happens to an extent that new species evolve from ancestral species, shouldn’t we find fossils of “in-between” species in the fossil record?

• Yes!

Winged Lizards

• 11 fossils from Southern Germany, dated to ~150mya

                                                                 

Archeopteryx

Microraptor gui

• China, 120mya – 4 winged dinosaur

Early tetrapods

Eusthenopteron- one of the earliest “lobe finned” fishes that display structures of both fish and amphibian

Late Devonian ~385mya

Acanthostega & Ichthyostega

• Upper Devonian ~365mya

Younger species of “fishapods” with progressively more developed pectoral and pelvic girdles, legs, and feet

Tiktaalik roseae• Early Devonian ~375mya

Fish: gills, scales

Fishapod: half-fish, half-tetrapod limb bones and joints, including a functional wrist joint and radiating, fish-like fins instead of toes; half-fish, half-tetrapod ear region

Tetrapod: tetrapod rib bones tetrapod mobile neck tetrapod lungs

Other examples?• Mammal-like Reptiles

• Horses

• Many others…

Vestigial structures – structures that once had a function but that there is no longer a use for.

Whales have a pelvis but no legs

Snakes have legs

Humans have a tail

Comparative Embryology – study of embryonic development

• Closely related species have very similar patterns of development

Fis

hS

alam

ande

r

Tur

tle

Chi

cken

Pig

Cow

Rab

bit

Hum

an

Genetics/Biochemistry

• Many genes share very similar sequences between species

• The more closely related two species are, the more similar the sequence

• All species share common sequences in genes that regulate the most basic aspects of life… from bacteria to humans!