Science

• What is the goal of science?– to understand the natural world in terms of

scientific theories• How does it do this?

– The Scientific Method– It’s a general phrase– Philosophy of Science

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The Classic Scientific Method

Observation – leads to a hypothesis Hypothesis – provides a testable

prediction about the observable world Experiment – reproducible (data, by

way of a reproducible methodology) and designed to discriminate between alternative hypotheses (a critical experiment)

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Basic Definitions

Hypotheses: hypotheses are like theories (they seek to explain a set of facts) Not supported by a large pool of facts Yet to be subject to experimentation (or have

undergone limited experimentation) Hypotheses must be testable

Provides a testable prediction about the natural world

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Basic Definitions

Theories: theories explain facts, essentially putting multiple facts into a cohesive context.For example … gravitywell testedsupported by a large amount of evidenceMuch more important than facts

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Evolution Evolution is the central theme of biology

Nothing in biology makes sense except in the light of evolution

Theodosius Dobzhansky

If all you think of when you hear “evolution” is the relationship between man and ape, you are missing a LOT.

Evolution and Faith• I can email you the “BYU packet” on evolution if you

request it• If your are of another faith I may be able to direct

you to something similar• If you do not practice any faith but have belief

related questions about evolution I can still try• I cannot offer “scientific” answers about religion.

Religious questions are, for the most part, outside the realm of science (and scientific questions are largely not approached by religious inquiry).

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Evolution

Organic (or biological) evolution: change in allele frequencies over time Allele = alternate form of a gene

E.g. …. relationship between genotype and

phenotype

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Speciation

Allopatric Speciation: believed the most common method of speciation (and the method of our speciation). Results primarily from genetic drift and Natural

selection

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History of Evolution

Evolution is an old theory Darwin didn’t come up with evolution

He did provide evidence for it and therefore popularized it and made possible the scientific discipline called evolutionary biology.

He also didn’t come up with the phrase “survival of the fittest” that you should probably forget you ever heard.

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Darwin

Charles Darwin used and preferred descent with modification

Darwin developed the theory of Natural Selection It is a mechanism, not an equivalent term to evolution

Who came up with the idea of natural selection independent of Darwin? Alfred Russel Wallace

Known as the father of biogeography

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Natural Selection - Logical Argument

1 Reproduction 2 Variation in trait (phenotype) 3 Heredity 4 Variation in fitness as a result of that trait

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Fitness

Fitness: average number of offspring left by an individual relative to the number of offspring left by an average member of the population

Relative Reproduction

What can influence fitness?

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Natural Selection

If natural selection occurs: the distribution of genotypes (phenotypes) of

the next generation will reflect the distribution of the more fit members of the previous generation

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Forms of Selection

Stabilizing selection Directional selection Disruptive selection Lets draw

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What happens depends on the nature of the selective force: It is not progressive, it depends on the environment

Why do some find this idea so disturbing?

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How does Evolution Illustrate the History of Life?

Phylogeny: branching diagram indicating the evolutionary history of an organism What does the history of life look like?

A phylogeny is a data based hypothesis about evolutionary relationships How is it a hypothesis?

What is the framework that Homo sapiens

fits in?

• American Museum of Natural History depiction of a Neanderthal hunter.

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Human Evolution and Classification

Tetrapods 4-limbed vertebrates (amphibians, reptiles

(including birds), and mammals are the extant groups).

Amniota Egg contains amnion, chorion, and allantois

Synapsida Fenestra arrangement, mammal-like reptiles

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Human Evolution and Classification

Mammalia Mammary glands Monotremes, Marsupials, and Placentals

EutheriaPlacental mammals

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Synapsid

ancestor

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Lice data Lice data confirmationconfirmation

Humans are most closely related to bonobos (pigmy chimpanzees) and chimpanzees

We diverged around 5 - 7 mya (sooner or later?)

We call this branch the Hominini

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Dra

w a

Phy

loge

netic

Tr

ee

Mon

ophy

letic

Humans

Chimpanzees

Gorillas

Orangutans

Gibbons

OWMs

NWMs

Why is it useful to know this framework?

• Kingdom: Animalia• Phylum: Chordata• Class: Mammalia• Order: Primates• Family: Homin• Genus: Homo• Species: sapiens

What do we share with other mammals?

I’m better than you! I have NINE

cervical vertebrae!

• Mammals have lungs with alveoli, with breathing mainly powered by a diaphragm

• Mammals have a 4-chambered heart• Mammals have a neocortex (part of the

cerebral cortex) in the brain• Mammals have differentiated teeth

(heterodontia)• All vertebrates have an integumentary system

with epidermis, dermis, hypodermis, but only mammals have fur (hair)

• Endothermy?• Viviparity?• Mammary glands and nipples?• Intelligence?

Lice dataLice data

Genetic data suggest an African origin

The Americas were the last continents colonized, apparently from North East Asia

What is the history of anatomy?• What did the painters at

Lascaux cave understand about anatomy 16,000 years ago?

• 6,600 + year old Egyptian manuscript shows that the heart, its vessels, liver, spleen, kidneys, uterus and bladder were recognized, and that the blood vessels were known to come from the heart.

Hippocrates• Greek• 5th century B.C.

The original Hippocratic Oath• I swear by Apollo, Asclepius, Hygieia, and Panacea,

and I take to witness all the gods, all the goddesses, to keep according to my ability and my judgment, the following Oath. To consider dear to me, as my parents, him who taught me this art; to live in common with him and, if necessary, to share my goods with him; To look upon his children as my own brothers, to teach them this art.

• I will prescribe regimens for the good of my patients according to my ability and my judgment and never do harm to anyone.

Hippocratic Oath (slide 2 of 4)

• To please no one will I prescribe a deadly drug nor give advice which may cause his death.

• Nor will I give a woman a pessary to procure abortion.

• But I will preserve the purity of my life and my arts.• I will not cut for stone, even for patients in whom

the disease is manifest; I will leave this operation to be performed by practitioners, specialists in this art.

Hippocratic Oath (slide 3 of 4)

• In every house where I come I will enter only for the good of my patients, keeping myself far from all intentional ill-doing and all seduction and especially from the pleasures of love with women or with men, be they free or slaves.

• All that may come to my knowledge in the exercise of my profession or in daily commerce with men, which ought not to be spread abroad, I will keep secret and will never reveal.

Hippocratic Oath. The End.

• If I keep this oath faithfully, may I enjoy my life and practice my art, respected by all men and in all times; but if I swerve from it or violate it, may the reverse be my lot.

Galen (from Rome; student of Hippocrates)

• He lived about 200 BC• He compiled findings from earlier

anatomists and dissected dogs, from which he made drawings

• His books were THE reference book for medicine for 1500 years!!!– His ideas were kept alive by Arabic

medicine, as Western medicine took several steps back after the fall of the Roman Empire

People didn’t challenge Galen’s ideas

• Because Galen said it, people believed that arterial blood came from the heart and venous blood came from the liver

• Because Galen said it, people thought the left ventricle of the heart was filled with air. Even when they saw blood in the heart they thought they were wrong, not Galen.

• Because Galen said bloodletting was a good practice, people carried it out until the 1800’s.

• There were two key concepts in his system of bloodletting. – The first was that blood

was created and then used up, it did not circulate and so it could 'stagnate' in the extremities.

– The second was that humoral balance was the basis of illness or health, the four humours being blood, phlegm, black bile, and yellow bile, relating to the four Greek classical elements of air, water, earth and fire.

In order to balance the humours, a physician would either remove 'excess' blood (plethora) from the patient or give them an emetic to induce vomiting, or a diuretic to induce urination.

Hippocrates believed that menstruation functioned to "purge women of bad humors." Galen began physician-initiated blood-letting.

A curious man• Andreas Vesalius

(1514-1564) came from a long line of Belgium physicians

• He wrote the famous De humani corpus.

• You can thank him for the idea of putting anatomical terms in Latin (or Greek)

Why Vesalius was different• Hands-on direct observation was considered the

only reliable resource, a huge break with medieval practice.

• He kept meticulous drawings of his work for his students in the form of six large illustrated anatomical tables

• In 1539 a judge became interested in Vesalius' work, and made bodies of executed criminals available for dissection. He soon built up a wealth of detailed anatomical diagrams.– Many of these were produced by commissioned

artists, and were therefore of much better quality than those produced previously.

• Anatomy flourished in the Renaissance (this is a 1559 print).

• Rembrandt’s depiction of an anatomy lesson, 1632

• In England, the Murder Act (1752) stipulated that only the corpses of executed murderers could be used for dissection. By the early 19th century, the rise of medical science, occurring at the same time as a reduction in the number of executions, had caused demand to outstrip supply. The Anatomy Act (1832) expanded the legal supply of cadavers for medical research and education, in reaction to public fear and revulsion of the illegal trade in corpses.

Gray's Anatomy: Descriptive and Surgical , by Henry Gray

• This book was first published in 1858.• While studying the anatomical effects of

infectious diseases, Gray contracted smallpox from his dying nephew and died shortly after the publication of the 1860 second edition, at the age of 34.

• Work on his much-praised book was continued by others and on November 24, 2004, the 39th British edition was released.

Which do you prefer?