1. 2/29 Warm-up Homologous traits between two different species is an indication of a recent common ancestor What type of evolution is described in the above statement? 2. Explain how this may be used in classification of organisms (taxonomy).

2. classification based on evolution
CLADISTICS
classification based on evolution

3. Are dinosaurs more closely related
to birds or reptiles?

4. When taxonomists want to identify
evolutionary relationships among species, they examine certain characteristics of species
Geographic distribution
Structural similarities
Breeding behavior
Biochemistry
Eventually some biologist proposed that structural similarities reflect the evolutionary relationships of species for example…
With the six kingdom system in place many taxonomists focused their research on reclassifying living thing in terms of there evolutionary relationships rater than on their structural similarities
The modern classification systems organize organisms in this way.
Chromosome comparisons

5. Structural similarities reflect evolutionary relationships
Bats are classified as mammals rather than as birds reflecting the evolutionary history that bats share with other mammals.
Bats fly like birds; they also have hair and
produce milk for their young.

6. Geographical distribution – The location of species on Earth helps biologist determine their relationships with other species.
For example the Finches of the Galapagos Islands, it is felt that the finches originated on the continent of South America and found tier way over to the island became isolated, spread to different niches of the island and evolved over time – WHAT IS THIS CALLED?

7. Chromosome comparisons – Both the number and structures of chromosomes
as seen during mitosis and meiosis
provide evidence about relationships.
Chimpanzee
Human
gorilla
The similar appearance of chromosomes among chimpanzees gorillas and humans suggest a common ancestry

8. Biochemistry - closely related species have similar DNA sequences and
therefore similar proteins.
The more inherited nucleotide sequences that two species share the more closely related they are.

9. Species that share a common ancestor
also share an evolutionary history.
Species that share a common ancestor also share an evolutionary history. The evolutionary history of a species is called its Phylogeny
Scientists who use cladistics assume that as groups of organisms diverge and evolve from a common ancestral group they retain some unique inherited characteristics that taxonomists call derived traits.
Biologists identify a groups derived traits and use them to make a cladogram.
On a cladogram groups that share a diverging branch probably share a more recent ancestor than those groups farther away.
In this cladogram for modern birds taxonomists identified the derived traits of modern bird – flight feathers light bones a wishbone down feathers and feathers with shafts
Then the identified ancestral species tat have at least some of these traits.
Most biologist agree that the ancestors of birds are a group of dinosaurs callled theropods. This group also includes allosaurus, sinornis, velocira[tor, archaeopteryx.
Each of these ancestors has a different number of derived traits. Archaeopteryx and the modern bird share 4 derived traits so they are closer together on the clado gram than the bird and the allosaurus which only shares one trait.
Phylogeny – The evolutionary history of a species
Derived traits – unique inherited characteristic
that are shared by different organisms