Evidence of Evolution. 1.Fossil Record 2.Homologous Body structures 3.Similarities in Embryology 4.Biochemical Evidence.

Evidence of Evolution

Evidence of Evolution

1. Fossil Record2. Homologous Body structures

3. Similarities in Embryology 4. Biochemical Evidence

Evidence of Evolution:The Fossil Record

• Fossil record provides evidence that living things have evolved

• Fossils show the history of life on earth and how different groups of organisms have changed over time

Relative vs. Absolute Dating

Relative Dating

• Can determine a fossil’s relative age

• Performed by estimating fossil age compared with that of other fossils

• Drawbacks – provides no info about age in years

Absolute Dating

• Can determine the absolute age in numbers

• Is performed by radioactive dating – based on the amount of remaining radioactive isotopes remain

• Drawbacks - part of the fossil is destroyed during the test

– A half-life is the amount of time it takes for half of the isotope to decay.

• Radiometric dating uses decay of unstable isotopes.

– Isotopes are atoms of an element that differ in their number of neutrons.

Primate Fossils

Australopithecus Homo erectus Homo sapien

Primate Bone Structure

Evidence of Evolution:Homologous Body Structures

– Structures that have different mature forms but develop from the same embryonic tissues

Ex: Wing of bat, human arm, leg of turtle

Turtle

Alligator

Bird

Evidence of Evolution:Homologous Structures

• Features that are similar in structure but appear in different organisms and have different functions.

• Strong evidence for common ancestor.• Ex: forelimbs of humans, bats and moles.

Human hand Bat wingMole foot

Analogous Structures• Structures that perform a similar

function.• Not evidence of common ancestry.

Vestigial Structures• Remnants of organs or structures that had a

function in an early ancestor.• Ex: Ostrich wings, used for balance but not

flight• Ex: Humans’ appendix

Evidence of Evolution:Similarities in Embryology

In their early stages of development, chickens,

turtles and rats look similar, providing

evidence that they shared a common

ancestry.

Embryological Development

Evidence of Evolution:Biochemical Similarities

• Scientists study nucleotide sequences in DNA and proteins in different organisms to determine ancestry.

• If the organisms are closely related they will have similar sequences of nucleotides in their DNA and arrangement of amino acids in proteins.

Evidence of Evolution:Biochemical Similarities

Organism Amino Acid Differences

Organism Amino Acid Differences

Human beta chain 0 Mouse 27

Gorilla 1 Kangaroo 38

Rhesus monkey 8 Chicken 45

Dog 15 Frog 67

Cow 25 Soy bean 124

The more similar the amino acid sequence, the more closely related the organisms are.