Biology 196: Evolution More Evidence (PWPT 4)

If species are related through descent, how should this be reflected?

It should be reflected in their structure.

Homology

-similarity resulting from common ancestry

-anatomical resemblances that represent variation on a structural theme present in a common ancestor

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Ex. Human, cat, whale, and bat forelimbs with different function

What is the best explanation for homologous characters?

Modification of structures from a common ancestor with different functions

What are early development homologies?

Embryological similarities in chordates that develop into different structures with different functions

-only explained by descent with modification

Vestigial structures

remnants that served function in ancestors

Molecular homology evidence

1. all cells consist of same organic compounds

2. all cellular reactions are controlled by the same class of proteins: enzymes

3. DNA is the molecule of inheritance for all organisms

4. DNA/RNA has same chemical structure in all organisms

5. All life essentially has the same universal genetic code (codons and amino acids)

Molecular evidence of descent with modification

Divergence of sequences of the same proteins as more unrelated through time

Convergent evolution

independent evolution of similar (analogous) features in different lineages

-Evidence of similar functional adaptions to similar environments

Know how to read this s**t: flip to back to see the sh*t :)

Fossil record

remaining traces of organisms from the past document pattern of evolution

Strata

formation of layers of sedimentary rock

What are predictions for the fossil record from the hypothesis of descent with modification?

1. If evolution occurred, species that lived in the past should be different from extant species (broadly evidenced by fossil record)

2. The older the sedimentary strata, the less chance of finding fossils of living species (uppermost strata= most recent, lower layers= oldest)

3. Descendant species will be found in upper strata, ancestors in lower strata

4. Transitional forms

What are transitional forms you may ask…

indeterminate forms between major taxonomic groups

Biogeography

study of geographic distribution of species

What are the predictions for biogeography?

1. Fossils in a given geographic area should show greater resemblance to the organisms there, than those living in another geographic region

2. Usually, closely related species will be in geographically close areas