Evidence ofEVOLUTION

Evolution: Genetic change in a population through time

Charles Darwin

◎ On his journey around the world, Darwin found evidence of GRADUAL CHANGE (evolution)

◎ He cited evidences he found in ○ Fossil records○ Geographic distribution○ Homologous structures

Evidences of Evolution

Today, most evidences of evolution are grouped into 5 main categories: 1. Fossil record2. Biochemical3. Comparative anatomy4. Biogeography5. Observable events

Fossil Record◎ Paleontology: the study of fossils◎ Fossil: remains or traces of an organism

that lived long ago○ Remains of an organism are things like

bones, teeth, or shells○ Traces of an organism are things like

burrows, footprints, or imprints

#1

◎ Most fossils are found in layered sedimentary rock

◎ Oldest fossils are on the lowest layer

◎ Comparing fossils shows:○ Life on Earth has

changed over time○ An increased number of

life forms OLD

NEW

#1

Biochemical◎ The genetic code◎ Triplets of DNA nitrogen

base sequences that code for specific amino acids

◎ The amino acid triplet is the same in almost all organisms

#2

#2

◎ The similarity of triplet DNA codes making up amino acids shows: ○ A probable common

ancestor for all life on Earth

◎ “Universal” genetic code: from organism to organism, genes code for the same amino acids

Amino acid sequencing is probably the STRONGEST evidence for relationships among organisms

◎ Amino acid sequencing: the amino acid sequence in a particular protein is compared between organisms

◎ Amino acid sequencing shows: ○ closeness of

relationship○ a probable common

ancestor

#2

Number of differences from human hemoglobin

#2

◎ Cladogram: diagram that shows the evolutionary relationship among a group of organisms

#2

◎ Which organism belongs at each branch?

◎ Where does the common ancestor belong?

Species AA Difference

Gorilla 1

Rhesus Monkey 8

Mouse 27

Chicken 45

Frog 67

Lamprey 125

Comparative Anatomy◎ Homologous structures: structures with

similar structure but DIFFERENT FUNCTION○ ex: turtle, alligator, bird, mammal

◎ Homologous structures show: ○ similar genes○ descent from a common ancestor

#3

◎ Analogous structures: body parts of organisms that do NOT have a common evolutionary origin but are similar in function

◎ Analogous structures don’t illustrate evolutionary relationships; they do provide evidence for evolution

#3

◎ Vestigial structures: organs so reduced in size that they are nonfunctioning remnants of similar organs in other species○ ex: human tailbone, appendix,

whale pelvis◎ Vestigial structures show:

○ an organism’s evolutionary past

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

#3

◎ Embryology: the study of embryos

◎ Embryos of different species may appear similar in early stages of development○ ex: vertebrate development

◎ Comparison in similarities in embryos can show: ○ Relationship to a

common ancestor

#3

Biogeography◎ Geographic distribution

of organisms ◎ Organisms living widely

apart (even different continents) may be similar because they share a common ancestor

◎ Biogeography shows: ○ a common ancestor

#4

◎ 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 show that evolution is an ongoing process

Observable Events

#5

Summary1. Fossil records show that life on Earth has

changed, and that there is an increased number of life forms.

2. Biochemical evidence shows that there’s a probably common ancestor for all life on Earth. Amino acid sequencing is the strongest evidence for relationships among organisms

3. Comparative anatomy shows similar genes and descent from a common ancestor.

4. Biogeography shows common ancestry. 5. Observable events show that evolution is an

ongoing process.

Miller, Kenneth and Levine, Joseph. (2004). Biology. Prentice Hall.

Works Cited