In your own words, how would you define

Evolution?

Can you think of an example of Evolution?

How do you know when something

has evolved?

EVOLUTION IS

GENETIC CHANGE IN A POPULATION THROUGH TIME.

GENETIC CHANGE IN A POPULATION THROUGH TIME.

EVIDENCES OF EVOLUTION

Charles DarwinOn his journey around the world, Darwin found evidence of gradual change (evolution).

Darwin cited evidences he found in fossil records, geographic distribution and homologous structures.

Evidences of EvolutionToday most evidences for evolution are grouped into five main categories:

Fossil RecordBiochemicalComparative

AnatomyBiogeographyObservable Events

FOSSIL RECORD Paleontology Fossil – remains or traces of an

organism that lived long ago

Remains: ex. bone, tooth, or shell

Traces: ex. burrow, footprint, or imprint

FOSSIL RECORD Most fossils are found in

layered sedimentary rock

Oldest fossils are in the lowest layers

Newest fossils are in the top layers

FOSSIL RECORD

Comparing fossils from different layers shows:

Life on Earth has changed

Increased number of life forms

BIOCHEMICALDNA & the genetic code One codon codes for one amino

acid – it works the same way in all species The codon

code for each amino acid is the same in almost all organisms.

BIOCHEMICAL

The similarity of the way DNA codes for amino acids shows:

A probable common ancestor for all life on Earth

BIOCHEMICAL

“Universal” GENETIC CODE Similar genes Over the ages, the genetic code

has passed unchanged (or nearly so) from parent to offspring.

BIOCHEMICAL AMINO ACID SEQUENCING

The amino acid sequence in a particular protein is compared between organisms. Number of differences

from human hemoglobin

45

167

8

27

125

BIOCHEMICAL Comparing amino acid sequence

shows: Closeness of

relationship A probable

common ancestor

Species DifferenceGorilla 1Rhesus Monkey

8

Mouse 27Chicken 45Frog 67Lamprey 125

Amino Acid Difference in Hemoglobin

Compared with Human

Human hemoglobin has 146 amino acids

Amino Acid Sequencing is probably the STRONGEST evidence for relationships among organisms.

What organism belongs at

each branch?

BIOCHEMICAL CLADOGRAM: diagram that

shows the evolutionary relationship among a group of organisms.

Species Difference

Gorilla 1Monkey 8Mouse 27Chicken 45Frog 67Lamprey

125

Amino Acid Difference in Hemoglobin

Compared with Human

Number of Amino Acid Differences150

10050

040 2030 10

G

FE

DCBA

Common ancestor

Where would the common ancestor be?

COMPARATIVE ANATOMY

HOMOLOGOUS STRUCTURES

structures with similar structure but different function

TurtleAlligator

BirdMammal

COMPARATIVE ANATOMY

Homologous structures show

Similar genes – similar proteins Descent from a common ancestor

TurtleAlligator

BirdMammal

Ancient lobe-finned fish

COMPARATIVE ANATOMYVESTIGIAL STRUCTURES organs so reduced in

size that they are nonfunctioning remnants of similar organs in other species

ex: human tailbone, appendix, gallbladder, whale pelvis

COMPARATIVE ANATOMY

Vestigial structures show:

an organism’s evolutionary past

a common ancestor with species that have similar structures that are still functioning

BIOGEOGRAPHY GEOGRAPHIC DISTRIBUTION

OF ORGANISMS

organisms living far apart may be similar because they share a common ancestor

OBSERVABLE EVENTS

Some changes in species have been observed and studied:

Peter & Rosemary Grant’s Study of Beak Size Shift in Darwin’s Finches

H. Kettlewell’s Study of Peppered Moth Color Shifts

OBSERVABLE EVENTS

Observable events show that evolution is an ongoing process

Peter & Rosemary Grant’s Study of Beak Size Shift in Darwin’s Finches

H. Kettlewell’s Study of Peppered Moth Color Shifts