Similar traits often indicates common ancestry Phylogeny (fahy-loj-uh-nee): evolutionary histories of a species Determined by examining: – Fossils – Living specimens – Molecular data – Development Domain Eukarya Kingdom Animalia Phylum Chordata Family Mammalia

Fossil Evidence Homologous structures: body parts that have a similar structure, but different function Relationships identified among different species Fossils link past life to modern life

Anatomy shows nonrelationships also

Comparing DNA, amino acids, chromosomes, proteins – Similarities and differences can be found – Splits in evolution can be estimated

Chromosome order: Human, orangutan, gorilla, pygmy chimp

Molecular data may confirm classification. Molecular data may lead scientists to propose a new classification. Molecular evidence reveals species’ relatedness. DNA is usually given the last word by scientists.

Cladistics is a common method to make evolutionary trees. –classification based on common ancestry –species placed in order that they descended from common ancestor –Shown in tree branching diagrams

A clade is a group of species that share a common ancestor. Derived characters are traits shared in different degrees by clade members. –Derived Characteristic –basis of arranging species in cladogram –more closely related species share more derived characters –represented on cladogram as hash marks FOUR LIMBS WITH DIGITS Tetrapoda clade 1 Amniota clade 2 Reptilia clade 3 Diapsida clade 4 Archosauria clade 5 EMBRYO PROTECTED BY AMNIOTIC FLUID OPENING IN THE SIDE OF THE SKULL SKULL OPENINGS IN FRONT OF THE EYE & IN THE JAW FEATHERS & TOOTHLESS BEAKS. SKULL OPENINGS BEHIND THE EYE DERIVED CHARACTER Nodes represent the most recent common ancestor of a clade. CLADE NODE

List 2 characteristics of a salamander. Where would a 3 rd be located? From the diagram, which organism is most closely related to the Chimp?

1) What does an amphibian & crocodile have in common? Vertebrae, Bony skeleton, Four limbs 2) List the traits of a ray-finned fish. Doesn’t have 4 limbs, has bony skeleton, has vertebrae