Biology 1130March 19th

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Announcements

• Chapter 9 reading quiz deadline: March 26th

• Chapter 10 reading quiz deadline: March 28th

Let’s Review!

• What’s a hypothesis? What notable features does a hypothesis have?

• What’s the scientific method?

Darwin’s Theory of Natural Selection

and its precursors

What’s a Scientific Theory?

• The result of repeated hypothesis testing• Provides an explanatory model in a scientific

discipline• The best explanation for what we see in the

natural world• As close to a fact as we can get

What did Western Europeans believe before the 1550s?

• The Earth was flat• The Sun and other heavenly

bodies moved around the Earth

• The Earth is young• The accounts of organismal

and human creation in Genesis were true:– Fixity of Species– Great Chain of Being

• What were some of the major discoveries, wars, and social events of this time period?

• How did these events change how people saw the world?

• How might these events have influenced scientific thought?

European History(1400s – 1900s)

Scientific Breakthroughs in the Renaissance and later

• Heliocentric, rather than geocentric universe• Earth is round• Invention of telescopes & microscopes

If the Biblical account of special creation is literally true, then…• There should be no evidence that organisms have

changed over time• All features of organisms should be perfectly designed

for their function• There should be no features that have no obvious

function• There should be no similarities between organisms• There should be no extinct organisms (that didn’t die in

the flood)• There should be no evidence of organisms existing more

than 6000 years ago

Discoveries that challenged the Biblical account of creation (1700 and 1800s)

Why organisms were more diverse than in the Bible

“New” Continents, “New” Species

Invention of the microscope

Breakthroughs in Biology in the Renaissance and later

• Why organisms were more diverse than in the Bible

Apparently extinct organisms

Mary Anning, Fossil Discoverer

Breakthroughs in Biology in the Renaissance and later

• Why organisms were more diverse than in the Bible

• Apparently extinct organismsGross anatomical similarities between organisms

Homology of mammal forelimbs

Bat Sea lion Lion Chimpanzee Human

Humerus

Radiusand ulna

Carpals

Metacarpals

Phalanges

Mammal ancestor

Squirrelmonkey Orangutan Gorilla

Commonchimpanzee Bonobo Human

increase in size ofgenital structures

delayed sexual maturitybroad incisors

shortened canine teethenlarged brow ridges

elongated skullreduced hairiness

large brain

increased flexibility of thumbmore erect posture

no tail

Order Primates

Family Hominidae

Subfamily Homininae

Breakthroughs in Biology in the Renaissance and later

• Why organisms were more diverse than in the Bible

• Apparently extinct organisms• Gross anatomical similarities between organismsVestigial structures

(a) Tail bone

(b) Goose bumps

“Useful” trait in primate relative Vestigial trait in human

Breakthroughs in Biology in the Renaissance and later

• Why organisms were more diverse than in the Bible

• Apparently extinct organisms• Gross anatomical similarities between organisms• Vestigial structuresSimilar embryonic development between species

Comparative Embryonic Development

Snake Chicken Possum Cat Bat Human

PharyngealslitsEarly

embryo

Intermediateembryo

Lateembryo

Tail

Breakthroughs in Biology in the Renaissance and later

• Why organisms were more diverse than in the Bible

• Apparently extinct organisms• Gross anatomical similarities between organisms• Vestigial structures• Similar embryonic development between speciesEvidence that organisms have changed over time

Hyracotherium(Eohippus)

Mesohippus

Merychippus

Equus

4 toes

3 toes

3 toes

1 toe

Horse ancestor Modern horse

55 40 17 4

Millions of years ago

Horses and their ancestors

Darwin and the armadillos

How can we explain all of this??

• Why organisms were more diverse than in the Bible

• Apparently extinct organisms• Gross anatomical similarities between organisms• Vestigial structures• Similar embryonic development between species• Evidence that organisms have changed over time

Darwin’s Voyage on the Beagle

Individuals who influenced Darwin

• Age of the Earth: – Lyell

• Similarities between organisms: – Ray – Linnaeus

• Fit between organisms and their environments: – Buffon – Lamarck

• Economics (?!):— Malthus

Charles Lyell: Uniformitarianism

• 1830s• Uniformitarianism &

deep time

Uniformitarianism

• Geologic processes (wind and water erosion, sedimentation, flooding, volcanic eruptions) are constant now and have been in the past

• These processes take place over a long time• The Earth is really old!

John Ray

• Late 1600s• Definition of

species (reproductive isolation)

Carolus Linnaeus: Linnaean Classification of Organisms

• 1735• Taxonomy (study of

relationships between organisms)

• included humans• differences and

similarities between species

• descent from a common ancestor

Mammal ancestor

Squirrelmonkey Orangutan Gorilla

Commonchimpanzee Bonobo Human

increase in size ofgenital structures

delayed sexual maturitybroad incisors

shortened canine teethenlarged brow ridges

elongated skullreduced hairiness

large brain

increased flexibility of thumbmore erect posture

no tail

Order Primates

Family Hominidae

Subfamily Homininae

Georges Leclerc Comte de Buffon

• 1749 • organisms are “well-suited” to their environments• adaptation• but against “transmutation”

Jean-Baptiste, Chevalier de Lamarck

• Late 1700s• Inheritance of

acquired characteristics

• first person to try to explain adaptation

Lamarck’s Inheritance of Acquired Characteristics

Thomas Malthus

• 1798• Economist• Populations have

finite resources• More individuals

born in most species than can survive

Malthus’ observation about populations and their resources

Charles Darwin

• Voyage of the Beagle (1830s)

• On the Origin of Species published (1859)

• Notice the gap in time…

Charles Darwin: Voyage of the Beagle (1830s)

What Darwin saw…• Similarities in Galapagos & South

American finches• Descent from a common ancestor• Differences seemed to be related to

food

What Darwin knew…• Knew about Malthus’

idea• Knew about artificial

selection • Sexual reproduction

produced variation

Alfred Russel Wallace:Almost “scooped” Darwin

• 1848: Amazonian journey

• knew species well-suited to environments

• Wrote to Darwin (1858)• 1859 Darwin published

On the Origin of Species• Why did Darwin wait?

1. Variation2. Variation must be heritable 3. Some variants better able to survive OR

reproduce than others in a given environment (reproductive fitness = differential reproductive success)

Over time, accumulation of successful variants result in adaptation

For Natural Selection to Happen, There Must Be:

• Survival only matters until the point of reproduction

• Environments contain selective pressures (predators, competition for food / mates)

• Environmental context is key (example: wooly mammoths)

More about natural selection

More about natural selection

Geographical isolation can produce new species: – if groups are exposed to different selective pressures

in their respective environments – gradually differences will accumulate– groups will no longer be able to interbreed

• Individuals survive & reproduce, but populations evolve

Evolution Example: “Peppered” Moths in England

What’s the selective pressure in the environment?

How did the population evolve?

Evolution Example: antibiotic-resistant bacteria (example: MRSA)

• What’s the selective pressure in the environment?

• How did the population evolve?

Misconceptions about Evolution

• It’s not testable• How does one formulate a testable hypothesis

about something that happened in the past?• It’s all about survival• If something exists, it’s the result of natural

selection (adaptationism) (example: male nipples)

Follow-up Questions

• What’s the Great Chain of Being?• What’s the Fixity of Species?• How do geocentric and heliocentric universes differ?• What’s a vestigial trait?• What’s uniformitarianism? What’s deep time?• What’s a species? What’s taxonomy?• What’s the inheritance of acquired characteristics?• What is adaptation?• What is required in order for natural selection to occur?

Judgment Day: Intelligent Design on Trial