Evolution

Why not invoke the supernatural (god or gods) to explain how we

got here?• The task of science is to make use of nature’s

redundancy to describe the world simply.

• We can use only empirical data.

• Everything else is outside the realm of science.

• We can’t use the methods of science to confirm or reject the supernatural. (Science is falsifiable; the supernatural is not.)

The National Association of Biology Teachers affirms that teaching biology must be in a standards-based instructional framework, upholding scientific integrity and the right to teach accurate and current science without penalty of political or religious influences on content. Experimentation, logical analysis, and evidence-based revision, based on detectable and measurable data, are procedures that clearly differentiate and separate science from other ways of knowing. Explanations or ways of knowing that invoke metaphysical, non-naturalistic or supernatural events are outside the scope of science and not part of a valid science curriculum.

Submitted by the NABT Board of Directors April 8, 2008.

Theories of Evolution• Darwin Wasn’t the

First:– Heraclitus (543 –

477 BC)“Evolution might involve conflict and a struggle for survival.”

– LeMark: Inheritance of Aquired Characteristics

Theories of Evolution• Hutton:

"...if an organised body is not in the situation and circumstances best adapted to its sustenance and propagation, then, in conceiving an indefinite variety among the individuals of that species, we must be assured, that, on the one hand, those which depart most from the best adapted constitution, will be the most liable to perish, while, on the other hand, those organised bodies, which most approach to the best constitution for the present circumstances, will be best adapted to continue, in preserving themselves and multiplying the individuals of their race."

Darwin

• Was different because he came up with a MECHANISM that was TESTABLE:

The theory of evolution BY MEANS OF NATURAL SELECTION

• Unlike many theories, his has not yet been disproven. Amazing!

Early Earth

4.6 billion years old

Originally chaotic:Volcanoes

• Produced gases– N2, CO2, H2O, CO, CH4

– No O2; O in CO2, H2O, CO, CH4

» Know because rocks aren’t oxidized

• Extreme temperature variations

Lightening & UV Light• Energy sources

How did the first organic chemicals form?

• Oparin and Haldane hypothesized that organic chemicals were made from the gases of the early atmosphere and the energy from lightening, UV light, and radioactivity from the Earth’s core.

• These organic molecules accumulated in the ocean creating an “organic soup” or “primordial soup.”

Miller - Urey Experiment

Stanley Miller

Results of more recent, refined Miller – Urey experiments

• 13 of 20 amino acids• All bases of DNA and RNA• Ribose

ALSO: found amino acids in meteorites and formaldehyde in tail of Haley’s comet.

Life may have originated in undersea vents

Biological Evolution

• Organic compounds had to come together to form complex molecules.– Clay could have attracted, held, and catalyzed

the reactions between them.

• Molecules have to self-replicate– Some RNA can, AND they work as enzymes

• May have been original molecule of life.

Biological Evolution, cont’

• Membranes have to form:– Put amino acids and fat

in water, fat will surround amino acids in spheres similar to cells.

• Split when get too big.• Are selectively

permeable

Oldest Fossils

• Are of microorganisms

• 3.485 billion years old

• Found in stromatolites (mats of bacteria)

Earliest Life

• Bacteria (prokaryotes)– Heterotrophs

• Didn’t have the machinery to photosynthesize

• Absorbed organic nutrients from the primordial soup

– Probably a bag of RNA and that’s its• Similar to today’s prokaryotes

Earliest Eukaryotes

• Developed by endosymbiosis:– Theory by Lynn Margulis– Large bacteria incorporated smaller, energy

producing bacteria– Mutualistic, symbiotic relationship formed

eukaryotes from prokaryotes• Large bacteria get nutrients

• Small bacteria get protection

Earliest Eukaryotes

Evidence for endosymbiosis:

• Mitochondria and Chloroplasts have– Own DNA – like today’s bacteria– Own ribosomes – like today’s bacteria– Double membranes (outer may have been from

vacuoles that engulfed the bacteria)

Biodiversity Increased With the Accumulation of Oxygen

Presently Earth has about 3 million different kinds of organisms.

For variation you need sexual reproduction.

For sexual reproduction you need a lot of energy.

To get a lot of energy (ATP) you need aerobic respiration.

Biodiversity Increased With the Accumulation of Oxygen

For aerobic respiration you need oxygen.

For oxygen you need photosynthesis.

For photosynthesis you need plants.

Variation did not come about until plants had produced significant quantities of oxygen so that aerobic respiration could take place.

Biodiversity and Oxygen

Level of Oxygen Gas (O2)

Number of different kinds of organisms

600 million ybp4.6 billion

SO: # of critters = sex = energy = O2 = photosynthesis

Empirical Evidence of Evolution

Fossil Evidence

• Study of fossils = paleontology

• Record is incomplete– Most organisms decay– Not all found

• NOTE: Older fossils found in deeper rock

– Not many people who hunt for them

Empirical Evidence of Evolution

Fossil Evidence• Best finds:

Intermediate forms (species to species)– E.g., Archaeopteryx

& China fossils• Feathers and wings of

birds, but teeth and tails of reptiles.

Empirical Evidence of Evolution

Homologous Structures

Empirical Evidence of EvolutionEmbryology

Empirical Evidence of EvolutionGenetic Information

Origin of Species

• Individuals do not evolve, populations do.

• Evolution– change in a population through time– Source of changes in genes

• Mutations

• Recombination at fertilization

• Crossing over

• Independent assortment

Origin of Species

– Outside Influences led to study of Epigenetics• Chemicals in the environment

• Diet

• Family History

• ????

Origin of Species

• Microevolution– Change in gene frequency within an individual

population.• Studies can help us tell what is going on in the

environment.

• Have to look at the gene pool

Hardy-Weinberg Law(useful for studying large, sexually

reproducing populations)

A population will NOT change IF

1. There is no mutation

2. Mating is completely random

3. There is no migration in or out

4. Natural selection does not occur (one individual is not favored over another)

Hardy-Weinberg LawAnd How often does this happen?

A population will NOT change IF

1. There is no mutation

2. Mating is completely random

3. There is no migration in or out

4. Natural selection does not occur (one individual is not favored over another)

NEVER – all populations evolve because eventually the environment changes

http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/life4e_15-6-OSU.swf

The Hardy Weinberg Equilibrium

F = “The frequency of”

So:FA x FA + 2(FA X Fa) + Fa X Fa= FA2 + 2 (FAFa) + Fa2 = 100%

Microevolution Example

Natural Selection of the Peppered Moth

Microevolution Example

Kinds of Selection

Stabilizing Directional Disruptive

Microevolution ExampleGenetic Drift in Beetles: Occurs in small populations

because the chances of coming up with the expected results is low compared to a large population.

Microevolution Example

Founder Effect

Migrate out and found a new population with different gene frequency.

Microevolution ExampleBottleneck: number of organisms is drastically

reduced for a few generation and the ones that survive have a different gene frequency.

Origin of Species

• Macroevolution– Change in species– Source of change in species = MUTATIONS– Inherited variations give some individuals an

improved chance to survive and reproduce as the environment changes.

• NOTE: ENVIRONMENT = LIVING THINGS TOO!– Viruses and Bacteria– Competitors

Origin of Species

• Organisms do not intentionally change. They cannot “will” a mutation because they “need” it. Those with mutations that help them survive do. Those without, die.

Origin of Species

• For new species to evolve– Two populations become so different in their

genetic makeup that they can no longer interbreed.

– Most common mechanism that separates populations: geographic isolation.

Geographic Isolation

Prezygotic Isolation

Other Forms of Isolation

Gamete Isolation – sperm not chemically attracted to egg or not gain entry to egg

Prezygotic Isolation

Other Forms of Isolation

Seasonal Isolation – Trees may give off pollen at different times of year

Prezygotic Isolation

Other Forms of Isolation

Zygote doesn’t develop normally, or produces a sterile offspring.

Postzygotic Isolation

Back to Geographic Isolation

New environments with few competitors allow populations to easily separate and go their own ways. Speciation will result– Called adaptive radiation

Evolution - Rate• Darwin:

– gradualism

• Niles Eldridge and Stephan J. Gould:– Punctuated Equilibrium

• Fossil evidence shows long periods of stasis followed by rapid change (an asteroid falls on your head)

Gradualism

Punctuated Equilibrium

Extinctions - Many

So What Do We Have Today?

3,000,000 different types

of organisms.

“Types” means “species”

Species Concept

Two organisms are of the same species IF they• Breed naturally• Produce fertile offspring

“Species” is a man-made term to help us organize our thinking

Classification of Organisms = Taxonomy

Now based on evolutionary relationships (DNA) rather than just physical characteristics.

Physical characteristics are important still– About the only thing we

can see in fossils!

Classification SystemKingdom, Phylum (Division for plants), Class,

Order, Family, Genus, Species

Why not common names?

Which one of these is a gopher?

Florida Washington

Classification System

Binomial nomenclature = Two-name naming system

• Invented by Carolus Linnaeus– Uses Latin (dead language doesn’t change)

Classification System• Species name = genus + specific epithet

– E.g., • Homo sapiens (humans)• Amphiprion percula

(clown fish)

Classifying Organisms

• Cladistics - based on evolutionary relationships and homologous structures– Compare shared derived characteristics

Classifying Organisms

• Elves, Gnomes, Leprechauns, and Fairies are thought to form an evolutionary group of little people with magic powers. However, the exact relationships are unknown. Infer the phylogenetic pattern based on the following information.

Classifying Organisms

• Pointy ears evolved from ears that were not pointy.

• Inhabiting woods is more primitive than inhabiting other places

• Ability to find hidden treasure evolved from the lack of such ability

• Ability to fly is primitive

Classifying Organisms

• Elves: pointy ears; haunt woods; can't find treasure; can't fly

• Fairies:ears not pointy: live in woods; can't find treasure; can fly

• Gnomes: ears not pointy; live in mines and quarries; find treasure; can't fly

• Leprechauns:ears not pointy; live in woods; find treasure; can't fly

Classifying Organisms

Pointy Ears

NOT woods

Find Treasure

NOT fly

Elves X X

Gnomes X X X

Leprechauns X X

Fairies

Classifying Organisms

Fairies

GnomesLeprechaunsElves

Not Fly

Find Treasure

Pointy EarsNot live in woods

EvolutionNothing in Biology Makes Sense Except in the Light of Evolution

Theodosius Dobzhansky (1900-1975)