Evidence, Speciation, Macroevolution

Evidence supporting evolution

� Fossil record

� shows change over time

� Anatomical record

� comparing body structures

�homology & vestigial structures

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�homology & vestigial structures

� embryology & development

� Molecular record

� comparing protein & DNA sequences

� Artificial selection

� human caused evolution

Homologous structures (Divergent Evolution)

� Structures that come from the same origin� homo- = same

� -logous = information

� Forelimbs of human, cats, whales, & bats

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� same structure

� on the inside

� same development in embryo

� different functions

� on the outside

� evidence of common ancestor

But don’t be fooled by these…

� Analogous structures

� look similar� on the outside

� same function

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� same function

� different structure & development� on the inside

� different origin

� no evolutionary relationship

Analagous or Homologous?

� Dolphins: aquatic mammal

� Fish: aquatic vertebrate

� both adapted to life in the sea

� not closely related

Convergent evolution (Analagous structures)

� 3 groups with wings

evolving similar solutions to similar problemsevolving similar solutions to similar problems

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� Does this mean they have a recent common ancestor?

What data from the Genome Project can tell us about evolution of humans

Chromosome Numbers in the great apes:

human (Homo) 4646chimpanzee (Pan) 48chimpanzee (Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48

Change in chromosome number?Change in chromosome number?If these organisms share a common ancestor, then is there evidence in the genome for this change in chromosome number

Change in chromosome number?Change in chromosome number?If these organisms share a common ancestor, then is there evidence in the genome for this change in chromosome number

Chromosome Numbers in the great apes (Hominidae):

human (Homo) 46chimpanzee (Pan) 48gorilla (Gorilla) 48orangutan (Pogo) 48

Ancestral Chromosomes

Fusion

Homo sapiens

Inactivated centromere

Telomere sequences

Testable prediction:Testable prediction:If common ancestor had 48 chromosomes (24 pairs) then humans carry a fused chromosome; orIf common ancestor had 46 chromosomes (23 pairs) then apes carry a split chromosome.

Centromere

Telomere

“Chromosome 2 is unique to the human lineage of evolution, having emerged as a result of head-to-head fusion of two acrocentric chromosomes that remained separate in other primates. The precise fusion site has been located in 2q13–2q14.1 (ref. 2; hg 16:114455823 – 114455838), where our analysis confirmed the presence of multiple subtelomeric duplications to chromosomes 1, 5, 8, 9, 10, 12, 19,

Homo sapiens

Inactivated centromere

Telomere

Human Chromosome #2 shows the exact point at which this fusion took place

duplications to chromosomes 1, 5, 8, 9, 10, 12, 19, 21 and 22 (Fig. 3; Supplementary Fig. 3a, region A). 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 (42).”

Telomere sequences

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

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

Chr 2

Discuss with a Partner

WHAT ARE THE MAIN EVIDENCES FOR EVOLUTION?FOR EVOLUTION?

WHICH DO YOU FEEL IS THE STRONGEST SUPPORT OF NATURAL

SELECTION?

WHY?

Speciation

� A theory that species can change over time to become different groups because of isolation, mutation, and evolution

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Species

Groups of organisms that can successfully

reproduce, having viable offspring

(A species can indefinitely perpetuate).

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Speciation requires…

�Isolation

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�Mutation

�Evolution

How does one group become separated and isolated?

Reproductive Isolation

� Speciation requires reproductive isolation

� (If they cannot mate, they’re considered different species)

Western Meadowlark Eastern MeadowlarkWestern Meadowlark Eastern Meadowlark

Reproductive Isolation may be:

A. PRE-ZYGOTIC Isolation

o (mating or fertilization prevented)

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B. POST-ZYGOTIC Isolation

o (hybrid zygote forms, but may die early, be weak, or be sterile)

Prezygotic Isolation

A. Geographical

o separated by habitato Ex: land & water, mountain & valley, tree &

grass

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Prezygotic Isolation

B. Temporal

o Separated by time

o Ex: nocturnal v. diurnal, 17-year cicadas

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Prezygotic Isolation

C. Behavioral

o Ex: mating song or dance

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Prezygotic Isolation

D. Mechanical

o physically do not fit, cannot mechanically mate

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MULE

Are horses and donkeys the same species?

ZEBROID or ZORSE

Are horses and zebras the same species?

How about a donkey and zebra?

ZONKEY?

WHOLPHIN?

Are dolphins and orcas the same species?

TIGON

Are lions and tigers the same species?

Evolution Video

Macroevolution

� How then do we get from the mechanism of speciation to evolution on a grand scale; i.e., macroevolution?

� Two models:

- Gradualism model

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- Gradualism model- change is gradual with the accumulation of unique

morphological adaptation.

- Punctuated Equilibrium model- rapid change occurs, with a new species “erupting” from

the ancestral lineage and then staying the same thereafter.

Discuss with your Partner

� What defines a species?

� Come up with 2 examples of reproductive isolation.

� What are the two models of Speciation?

Selection

Directional Selection

Stabilizing Selection

DisruptiveSelection

� Shift in one direction

• Intermediate forms of a trait are

• Two extreme forms of a trait

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direction

� One extreme or the other is selected

forms of a trait are selected

• Most of the population is “average”—extremes are selected against

forms of a trait are selected

• Most are one extreme or the other—middle is selected against

DRAW THESE!

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This is

__________ Directional__________ Selection

Directional

This is

__________ Stabilizing__________ Selection

Stabilizing

This is

__________ Disruptive__________ SelectionDisruptive

This is

__________ Directional__________ Selection

Directional

Discus with your Partner…

� Using the fish in the lake below come up with an example of selection.

� What could cause Directional Selection?

� What could cause Stabilizing Selection?

� What could cause Disruptive Selection?� What could cause Disruptive Selection?

Hint: Look at body size, color, patterns (stripes or spots). Think about food sources and other resources. Consider Predators!

Adaptive Radiation

� When one species increases in number without

competition and evolves into new species in a new

environment.

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Extinction

� Irrevocable loss of a species

� (Usually followed by adaptive radiation of other species)

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Artificial Selection

� occurs when humansselect traits that

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select traits that survive and proliferate

� (Selective breeding)

What Does This Picture Have To Do With Artificial Selection?

What Kind Of Dog Do YOU Like?

Speciation Charades!

� Each group will pick a random vocabulary term

� Spend 3 minutes planning how you will act out your concept.

� No talking

� Props are encouraged! � Props are encouraged!

Each group will present until the class can correctly identify the concept on their white

boards or paper.

Possible Terms

Reproductive Isolation

Speciation Convergent Evolution

Divergent Punctuated Gradualism

Divergent Evolution

Punctuated Equilibrium

Gradualism

Adaptive Radiation

Geographic Isolation

ArtificialSelection

Homologous structures

Analogous Structures

Vestigial Structures