Evidence of Evolution

by Natural Selection

(Ch. 16.4)

Dodo bird

Evidence supporting evolution• Fossil record

• Anatomical record

• Molecular record

• Artificial selection

Fossil record• Layers of sedimentary rock contain fossils

– new layers cover older ones, creating a record over time

– Show that a succession of organisms have populated Earth throughout a long period of time

Formation of sedimentary strata containing fossils

1 Rivers carry sediment to the

ocean. Sedimentary rock layers

containing fossils form on the

ocean floor.

2 Over time, new strata are

deposited, containing fossils

from each time period.

3 As sea levels change and the seafloor

is pushed upward, sedimentary rocks are

exposed. Erosion reveals strata and fossils.

Younger stratum

with more recent

fossils

Older stratum

with older fossils

A gallery of fossil types

(a) Dinosaur bones being excavated

from sandstone

(g) Tusks of a 23,000-year-old mammoth,

frozen whole in Siberian ice

(e) Boy standing in a 150-million-year-old

dinosaur track in Colorado

(d) Casts of ammonites,

about 375 million

years old

(f) Insects

preserved

whole in

amber

(b) Petrified tree in Arizona, about

190 million years old

(c) Leaf fossil, about 40 million years old

Support (proof?) for a VERY old Earth.

A dragonfly fossil from Brazil, more than 100 million years old

The Geologic Record

Evolutionary change in horses

Millions of years ago

50

100

150

200

250

300

350

400

450

500

550

60 55 50 45 40 35 30 25 20 15 10 5 0

Equus

HyracotheriumMesohippus

Merychippus

Nannippus

Bo

dy s

ize (

kg

)

Evolution of birds

Smithsonian Museum,

Washington, DC

• Archaeopteryx– lived about 150 mya

– links reptiles & birds

?

?

?

?

Land Mammal

Whales, you ask...

A transitional fossil linking past and present

2006 Fossil Discovery of Early Tetrapod

• Tiktaalik

– “missing link” from sea to land animals

Anatomical record

• Homologous structures

– similarities in characteristics resulting from common ancestry

Homologous structures

• Similar structure

• Similar development

• Different functions

• Evidence of close evolutionary relationship

– recent common ancestor

spines

tendrils

succulent leaves

colored leaves

Homologous structures

leaves

needles

Analogous structures

Separate evolution of structures

similar functions

similar external form

different internal structure & development

different origin

no evolutionary relationship

Solving a similar problem with a similar solution

Don’t be fooledby their looks!

Convergent evolution• Flight evolved in 3 separate animal groups

– analogous structures

Does this mean they have a

recent common ancestor?

Convergent evolution of analogous burrowing characteristics

Convergent evolution

Fish: aquatic vertebrates

Dolphins: aquatic mammals

similar adaptations to

life in the sea

not closely related

Those fins & tails & sleek bodies are

analogous structures!

Parallel Evolution

• Convergent evolution in common niches– Similar ecological roles in similar environments, Similar

adaptations were selected

– but are not closely related

marsupial

mammalsplacental

mammals

Parallel types across continentsNiche Placental Mammals Australian Marsupials

BurrowerMole

Anteater

Mouse

Lemur

Flyingsquirrel

Ocelot

Wolf Tasmanian “wolf”

Tasmanian cat

Sugar glider

Spotted cuscus

Numbat

Marsupial mole

Marsupial mouse

Anteater

Nocturnalinsectivore

Climber

Glider

Stalkingpredator

Chasingpredator

Vestigial organs• Structures that serve little or no function

– remnants of structures that were functional in ancestral species

– deleterious mutations accumulate in genes for non-critical structures without reducing fitness

• snakes & whales — remains of pelvis & leg bones of walking ancestors

• eyes on blind cave fish

• human tail bone

This is notLaMarck’s loss from “disuse”!

Vestigial organs

• Hind leg bones on whale fossils

Why would whaleshave pelvis & leg bonesif they were always

sea creatures?

Comparative embryology

• Similar embryological development in closely related species

– all vertebrate embryos have similar structures at different stages of development

• gill pouch in fish, frog, snake, birds, human, etc.

Anatomical similarities in vertebrate embryos

Pharyngeal

pouches

Post-anal

tail

Chick embryo Human embryo

Molecular record

0 25 50 75 100 1250

25

50

75

100

Millions of years ago

Horse/donkey

Sheep/goat

Goat/cow

Llama/cow

Pig/cow

Rabbit/rodent

Horse/cow

Human/rodent

Dog/cow

Human/cow

Human/kangaroo

Nu

cle

oti

de s

ub

sti

tuti

on

s

• Comparing DNA & protein structure– universal genetic code!

• DNA & RNA

– compare common genes• cytochrome C (respiration)

• hemoglobin (gas exchange)

Closely related species have

sequences that are more similar

than distantly related species

A molecular record of evolutionary

relationships

Why comparethese genes?

Comparison of a protein found in diverse vertebrates

Species

Human

Rhesus monkey

Mouse

Chicken

Frog

Lamprey14%

54%

69%

87%

95%

100%

Percent of Amino Acids That Are

Identical to the Amino Acids in a

Human Hemoglobin Polypeptide

Comparative hemoglobin structure

Number of amino acid differences betweenhemoglobin (146 aa) of vertebrate species and that of humans

100 20 30 40 50 60 70 80 90 100 110 120

LampreyFrogBirdDogMacaqueHuman

328 45 67 125

Why does comparingamino acid sequencemeasure evolutionary

relationships?

Building “family” treesClosely related species (branches) share same line of descent until their divergence from a common ancestor

Artificial selection

• Artificial breeding can use variations in populations to create vastly different “breeds” & “varieties”

“descendants” of the wolf

“descendants” of wild mustard

Natural selection in action

• Insecticide & drug resistance

– insecticide doesn’t kill all individuals

– resistant survivors reproduce

– resistance is inherited

– insecticide becomes less & less effective

Evolution of drug resistance in HIV

Patient

No. 1

Patient No. 2

Patient No. 3

Weeks

Evolution Misconceptions

“if we came from apes how come

were not hairy and have a big

mouth and did we end up looking

like we do know and besides there

isnt any serious proof of apes they

showd a video saying an ape

waswondering around in the forest

that thing looked exactly like a

costume that i had saw at a store

know one ever cought an ape”

-From a post on the Internet

NOT THIS KIND!!!

(beyond help)

The Complexity Fallacy

Evolution is not goal-orientedAn evolutionary trend does not mean that evolution is goal-oriented.

Surviving species do not represent the peak of perfection. There is compromise & random chance involved as well

Remember that for humans as well!

Evolution is not the

survival of the fittest.

Rather it is the

survival of the just

good enough.

Unintelligent Design

Serial circulation in the

mammalian heart

"Nothing in biology makes sense except

in the light of evolution."

-- Theodosius DobzhanskyMarch 1973

Geneticist, Columbia University

(1900-1975)

-- Ernst MayrWhat Evolution Is

2001

Professor Emeritus, Evolutionary Biology

Harvard University

(1904-2005)

Evolution is "so overwhelmingly established that it has become

irrational to call it a theory."

I might be dead, but

Perhaps you children

would appreciate a bit of

what you call the “rap”

music?!?

Don’t Be

Unintelligent...

Ask Questions!!

Evidence of Evolution

by Natural Selection

Testable Hypotheses

Just Because Things Seem Obvious

Doesn’t Mean They Don’t Need To Be Supported

Peppered Moths

• Dark vs. light variants

Year % dark % light

1848 5 95

1895 98 2

1995 19 81

Peppered moth

• What was the selection factor?

– early 1800s = pre-industrial England

• low pollution

• lichen growing on trees = light colored bark

– late 1800s = industrial England

• factories = soot coated trees

• killed lichen = dark colored bark

– mid 1900s = pollution controls

• clean air laws

• return of lichen = light colored bark

– industrial melanism

Genome sequencing• What can whole genome

sequence data tell us about evolution of humans?

Primate Common Ancestry?Chromosome Number in

the Great Apes

(Hominidae)

orangutan (Pogo) 48

gorilla (Gorilla) 48

chimpanzee (Pan) 48

human (Homo) 46

Hypothesis:

Change in chromosome number?

If these organisms share a common

ancestor, then is there evidence in

the genome for this change in

chromosome number

Could we have just lost a pair ofchromosomes?

Chromosomal fusionTestable prediction:

If common ancestor had 48 chromosomes (24 pairs),

then humans carry a fused chromosome (23 pairs).

Centromere

Telomere

Ancestral

Chromosomes Fusion Homo sapiens

Inactivated

centromere

Telomere

sequences

Chromosome Number in

the Great Apes

(Hominidae)

orangutan (Pogo) 48

gorilla (Gorilla) 48

chimpanzee (Pan) 48

human (Homo) 46Testable!

This is what makes evolution science& not belief!

Test of the Human Genome“Chromosome 2 is unique to the human

lineage of evolution, having emerged as a

result of head-to-head fusion of two

chromosomes that remained separate in

other primates. The precise fusion site has

been located in 2q13–2q14.1, where our

analysis confirmed the presence of multiple

subtelomeric duplications to chromosomes

1, 5, 8, 9, 10, 12, 19, 21 and 22. During the

formation of human chromosome 2, one of

the two centromeres became inactivated

(2q21, which corresponds to the centromere

from chimp chromosome 13) and the

centromeric structure quickly deterioriated.”

Hillier et al (2005) “Generation and Annotation of the DNA

sequences of human chromosomes 2 and 4,” Nature 434: 724 – 731.

Chr 2

Ancestral

Chromosomes Fusion Homo sapiens

Inactivated

centromere

Telomere

sequences

Human Chromosome #2 shows the exact

point at which this fusion took place

Well I’llbe a monkey’s…or an ape’s…

uncle!

Geographic variation in chromosomal mutations

1 2.4 3.14 5.18 6 7.15

XX1913.1710.169.128.11

1 2.19 3.8 4.16 5.14 6.7

XX15.1813.1711.129.10

2007-2008

Any Questions??

Review Questions

1. A complete fossil record

1. Exists because of the great preservation in

ocean sediment

2. Exists because of the solidification of minerals

around organisms

3. Is available because of the small location in

which all organisms used to live

4. Exists because organisms that die become

embedded in the soil to form rocks

5. Does not exist.

2. The similarity of insect wings and bird wings is an

example of

A. Behavioral adaptations

B. Geographic isolation

C. Adaptive radiation

D. Convergent evolution

E. Divergent evolution

3. The human appendix is an example of

1. A balanced polymorphism

2. Divergent evolution

3. Convergent evolution

4. A vestigial structure

5. A homologous structure

4. One piece of evidence that supports evolution from

molecular biology is:

1. Carbohydrate structure

2. Amino acid sequences

3. Lipid composition

4. Nucleotide structure

5. Cellulose chains