Part 2 Evidence of Common ancestry Unit 3 Part 2 Evidence of Common ancestry Interpreting Fossil Evidence to show evolution of organisms

1. Interpreting Fossil Evidence to show evolution of organisms Copyright Pearson Prentice Hall

Fossils Fossil records tell the Earth’s story. Over years many many layers of rock have formed. Many fossils are found within layers of rock. Fossils are the preserved remains or traces of organisms that lived in the past

Relative Dating In relative dating, the age of a fossil is determined by comparing its placement to that of fossils in other layers of rock.

LAW of SUPERPOSITION Rock layers form in order by age—the oldest on the bottom, with more recent layers on top

Index Fossil In Relative dating you are comparing 1 fossil to another, generating a history. For this you need an INDEX FOSSIL An index fossil is a species that is recognizable and that existed for a short period but had a wide geographic range.

Absolute Dating . Absolute Dating= radioactive dating Paleontologists determine the age of fossils using the fact that elements decay into measureable radioactive quantities. Scientists use radioactive decay to assign an absolute age to rocks Using radioactive decay, C12-C14scientists can determine true age of a fossil.

Cladogram A branching diagram representing a Hypothesis about the evolution of groups of organisms from a common ancestor

2. Homology of Anatomy is evidence to show evolution of Organsims

Homologous Structures Similar structures in different species but perform different functions because they share a common ancestor Ex: human arm, dog front limb, horse leg, whale fin These “LOOK the SAME” But have different functions An

Analogous Structures Analogous structures Distantly related species have different structures that have the same function. Ex: wing of butterfly & bird These “look different” But have “same function”

Vestigial Structures Vestigial structures Structures reduced in size & often unused Remains of functional structures inherited from an ancestor Ex: leg & hip bones in pythons & whales

3. How Molecular Evidence shows Evolution of Organisms

DNA and Protein Homology Also called biochemical evidence Compares biomolecules such as DNA, RNA or amino acid sequences between organisms Related organisms have more of the same molecules in common

4. Developmental Homology shows evidence of evolution

Embryonic Development Common development of the organism throughout it’s embryonic development before being born.