(Chuck)
Darwin, Chuck
Charles 1809 - 1882
The Origin of Species - 1859
Created a scientific revolution Unlike some other scientific revolutions, this one did not require any new methods, observations, or calculations Instead it came from the meticulous accumulation and synthesis facts from many different fields including Geology, Systematics, Natural History, Plant and Animal Breeding, and Economics Darwin
Outline
His intellectual time period The voyage of the Beagle 1831-1836 The O rigin of Species 1859
Descent with Modification Natural Selection Closing remarks
Linnaeus (classification) Hutton (gradual geologic change) Lamarck (species can change) Malthus (population limits) Cuvier ( fossils, extinction) Lyell (modern geology) Darwin (evolution, n utural s election) Mendel (inheritance) American Revolution 1750 Wallace (evolution, natural selection) French Revolution U.S. Civil War 1800 1850 1900 1795 Hutton proposes his theory of gradualism. 1798 Malthus publishes Essay on the Principle of Population. 1809 Lamarck publishes his theory of evolution. 1830 Lyell publishes P rinciples of Geology. 1831 1836 Darwin travels around the world on HMS Beagle. 1837 Darwin begins his notebooks on the origin of species. 1844 Darwin writes his essay on the origin of species. 1858 Wallace sends his theory to Darwin. 1859 The O rigin of Species is published. 1865 Mendel publishes inheritance papers.
Early Classification of Species
Aristotle
Viewed species as fixed and unchanging Species arranged in a linear sequence of increasing approach towards god
The Old Testament
Holds that species were individually designed by God and therefore perfect and that man and woman were the final creations representing the highest forms of life
Some of Darwins Influences Classification Linnaeus Geology Hutton, C uvier, L yell Populations Malthus
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Lamarcks Theory of Evolution
Carolus Linnaeus (1707-1778) Lamarck: Theory of Inheritane of Acquired Characteristics. Hypothesized that species evolve
Through use and disuse and the inheritance of acquired traits But the mechanisms he proposed are unsupported by evidence Shows that biologists were thinking about species as potentially changing and evolving into new species
Was a founder of taxonomy, classifying lifes diversity into a nested system of relationships or affinities (e.g. kingdom, phylum, class, order, family, genus, species) Provides a more tree-like view of the relationships among living species Interpreted organisms fit to their environment (adaptations) as evidence that the Creator had designed each species for a specific purpose
Geology
The study of fossils helped to lay the
groundwork for Darwins ideas
Georges Cuvier
Developed paleontology, the study of fossils Noted that more recent strata contained organisms more similar to the ones living today Cuvier opposed the idea of gradual evolutionary change
And instead advocated catastrophism, speculating that each boundary between strata represents a catastrophe After a catastrophe, new organisms appear, perhaps through migration from elsewhere Cuvier w as convinced that species were immutable
Fossils are remains or traces of organisms from the past
Usually found in sedimentary rock, which appears in layers or strata
Figure 22.3
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Hutton and Lyell
Gradualism
Is the idea that profound change can take place through the cumulative effect of slow but continuous processes The processes that we see acting today (sedimentation, erosion, volcanism, earthquakes) can, over long time periods, create the landforms we currently observe Requires that earth is substantially older than the biblical account. Darwin carried and read Lyells b ook on voyage of the Beagle
Darwins Life Before the Voyage
As a boy and into adulthood, Charles Darwin had a consuming interest in nature Went to Cambridge where he studied Biology and was particularly encouraged by the BOTANIST Henslow. Failed to make it as a pre-med. Thought he might become a country clergyman, so he could earn a steady income while continuing his study of natural history (when not writing sermons). Henslow was also a clergyman. Soon after Darwin received his B.A. degree Henslow suggested him as a candidate to be naturalist aboard the voyage of the HMS Beagle.
In 1831, when he returned home after graduation and a vacation, Darwin found two important letters waiting for him. One invited Darwin to become an unpaid naturalist on an exploratory voyage led by Captain FitzRoy on the H.M.S. Beagle starting in early October. The purpose of the voyage was to complete a government survey of the "southern extremity of America. This meant the ship would spend time along the coasts carefully mapping shipping channels, while Darwin, as naturalist, could explore the interior. The other letter was from his former professor, John Henslow, who explained why he had recommended Darwin: "I have stated that I considered you to be the best qualified person I know of, not on the supposition of your being a finished Naturalist, but as amply qualified for collecting, observing, and noting any thing worthy to be noted in natural history."
Chucks dad thought the voyage was a bad career move. Some of his arguments below.
Disreputable to your character as a clergyman A wild scheme The job must have been offered to other, more qualified, naturalists who must have had good reasons to refuse it Youll never settle down to a steady life Accommodations will be most uncomfortable This will be another change of profession Its a useless undertaking
Darwin got support from his maternal uncle Joseph Wedgewood, then wrote this whimpering letter to his dad.
My dear father, I am afraid I am going to make you very uncomfortable. But upon consideration, I think you will excuse me once again stating my opinions on the offer of the Voyage . But prey do not consider, that I am so bent on going, that I would for one single moment hesitate, if you thought, after a short period, you should continue uncomfortable .If you make up your mind directly will you send me an answer on the following day?
Voyage of the Beagle 1831-1836
England NORTH AMERICA PACIFIC OCEAN Galpagos Islands SOUTH AMERICA AUSTRALIA Andes Cape of Good Hope Cape Horn Tasmania New Zealand ATLANTIC OCEAN AFRICA HMS B eagle in port EUROPE
Darwin in 1840, after his return
Apparently, the answer was Well, OK
Figure 22.5
Tierra del Fuego
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Seven ports of call to discuss:
Cape Verde Islands Brazil Tierra Del Fuego Falklands Chile Galapagos Cocos Islands
Cape Verde Islands
A ring of white sedimentary rock containing marine shells occurs around the islands about 45 ft. above sea level. Darwin reasoned there must have been uplift (Lyells influence), with the old seafloor now raised above sea level.
Brazil
Darwins first exposure to wet tropical environments Delight itself, however, is a weak term to express the feelings of a naturalist who, for the first time, has wandered by himself in a Brazilian forest. The elegance of the grasses, the novelty of the parasitical plants, the beauty of the flowers, the glossy green of the foliage, but above all the general luxuriance of the vegetation, filled me with admiration. Collected extensively, documented the behavior of vampire bats, d iscovered many brightly colored terrestrial flatworms.
Darwin also discovered the bones of this giant ground sloth (Megatherium), as well as other large mammals such as giant armadillos. Darwin knew these were recent as they were embedded in shell beds containing shells identical to nearby living species. Darwin recognized that these mammals were related to smaller living forms.
Falkland Islands
"As far as I am aware, there is no other instance in any part of the world, of so small a mass of broken land, distant from a continent, possessing so large an aboriginal quadruped peculiar to itself. Their numbers have rapidly decreased; Within a few years after these islands shall become regularly settled, in all probability this fox will be classed with the dodo, as an animal which has perished from the face of the earth."
Tierra Del Fuego
Jeremy Button On a previous trip, Fitzroy, captain of the Beagle, had captured and brought back to England 4 F uegians. Who had learned English language and customs and Anglican religion. Three of them returned on the Beagle, along with a missionary. When the Beagle put them ashore to found a mission, the Fuegians r everted back to their native ways, refusing to help with missionary work or return to England (the missionary went back to England). Darwin had interacted with these men f or a year before they reverted. This and other observations convinced him that no real differences in abilities existed between races of men.
Falklands fox, now extinct
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Chile
Darwin traveled and collected extensively up into and over the Andes. Found fossil shells in sediments at 12,000ft Darwin witnessed (from the safety of the ship) both a volcanic eruption and a massive earthquake The earthquake raised portions of the coastal shelf by eight feet. Thought experiment: If there were one earthquake every 250 years that raised the earth by 5ft, how long would it take for the Andes to rise to 20,000ft? Darwin seeing the world through Lyells eyes, that forces observable today can create what we see around us, given enough time.
Galapagos
" A group of finches, of which M r. Gould considers there are thirteen species; and these he has distributed into four new sub-genera. These birds are the most singular of any in the archipelago. They all agree in many points; namely, in a peculiar structure of their bill, short tails, general form, and in their plumage. The females are gray or brown, but the old cocks jet-black. All the species, excepting two, feed in flocks on the ground, and have very similar habits. It is very remarkable that a nearly perfect gradation of structure in this one group can be traced in the form of the beak, from one exceeding in dimensions that of the largest grosbeak, to another differing but little from that of a warbler."
Adaptive Radiations
Hawaiian honeycreepers Galapagos finches
Cocos Islands
Atoll formation
Others had postulated that corals build themselves up from the sea floor over time. Darwin found evidence of coral only to a depth of about 120ft. From this Darwin surmised t hat coral had probably first formed as a circular reef in the shallow waters around a small island. Eventually the island started to sink as the ocean floor subsided. The coral continued to grow upward, m aintaining the circular reef at the right height for growth, as the island sank. Today, the original island is submerged, but portions of the reef remain as the islands of the atoll. The full details of the formation of a coral atoll were published Darwin by in his 1842 book, "The Structure and Distribution of Coral Reefs."
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Darwin returns (1836)
Already famous due to promotion of his natural history observations by Henslow Sets about to synthesize his knowledge Vague doubts about the stability of species Publishes The Origin of Species in 1859
Two influences further Darwins ideas about Natural Selection
Malthus essay on population growth Experiments in plant breeding and consultations with animal breeders
"In October 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement M althus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long-continued observation of the habits of animals and plants, it at once struck me that under these circumstances favourable v ariations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species. Here, then I had at last got a theory by which to work". Charles Darwin, from his autobiography. (1876)
Pigeon Breeds
Alfred Russell Wallace
A naturalist who spent decades collecting, particularly in tropical Asia Founded ideas of biogeography Wrote to Darwin in 1858 with his independent, but essentially identical, ideas on e volution by natural selection Lyell and others published essays by Wallace and Darwin together in 1858 Darwin rushes The Origin of Species into press in 1859.
Darwins Book
Sold out the first day Convinced several leading scientists immediately Particularly Thomas Huxley who became known as Darwin s Bulldog in the ensuing debate with clerics and others Darwin engaged in this debate only with further writings.
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Darwins books (partial list)
1859: O n the Origin of Species by Means of Natural Selection. 1862: O n the various contrivances by which British and foreign orchids are fertilised b y insects 1868: V ariation of Plants and Animals Under Domestication 1871: T he Descent of Man and Selection in Relation to Sex 1872: T he Expression of Emotions in Man and Animals 1875: M ovement and Habits of Climbing Plants 1875: I nsectivorous Plants 1876: T he Effects of Cross and S elf-Fertilisation i n the Vegetable Kingdom 1877: T he Different Forms of Flowers on Plants of the Same Species 1881: F ormation of vegetable Mould Through the Action of Worms
Thomas Huxley
'How incredibly stupid of me, not to have thought of that myself!'
Huxleys Letter to Darwin
I finished your book yesterday... no work on Natural History Science I have met with has made so great an impression on me & I do most heartily thank you for the great store of new views you have given me... As for your doctrines I am prepared to go to the Stake if requisite... I trust you will not allow yourself to be in any way disgusted or annoyed by the considerable abuse & misrepresentation which unless I greatly mistake is in store for you... And as to the curs which will bark and yelp - you must recollect that some of your friends at any rate are endowed with an amount of combativeness which (though you have often & justly rebuked it) may stand you in good stead - I am sharpening up my claws and beak in readiness.
Evolution by Natural Selection: Simple Necessary Concepts
Evolution - genetic change through time Fitness - reproductive success of an individual Adaptation - a heritable change that becomes common or pervasive in a population or species because it increases fitness Natural selection - The process by which heritable variations that increase fitness become more prevalent in successive generations Evolution by natural selection - requires heritable variation that affects fitness
The Origin of Species
Darwin developed two main ideas
Evolution explains lifes unity and diversity Natural selection is a cause of adaptive evolution
Descent with Modification
The phrase descent with modification
States that all organisms are related through descent from an ancestor that lived in the remote past Defines what Evolution is, heritable change through time.
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In the Darwinian view, the history of life is like a tree with multiple branchings from a common trunk to the tips of the youngest twigs that represent the diversity of living organisms. This view explains the hierarchical relationships in Linnaean classification.
Sirenia Hyracoidea (Manatees (Hyraxes) and relatives)
Deinotherium Mammuthus Stegodon Mammut
Years ago
Elephas Loxodonta Loxodonta maximus africana cyclotis (Asia) (Africa) (Africa)
Millions of years ago
Moeritherium
Barytherium
Figure 22.7
Platybelodon
Natural Selection
Descent with modification, or evolution, describes the changes of organisms through time. Natural Selection is one mechanism of change Natural Selection is the process that leads to adaptation
Deductive reasoning for evolution by natural selection
Observation #1: For any species, population sizes would increase exponentially
If all individuals that are born reproduced successfully This is the argument of ?
A Lyell B Cuvier C Copernicus D M althus E Darwin
Figure 22.8
Observation #2: Nonetheless, populations tend to be stable in size Observation #3: Resources are limited
Inference #1: Production of more individuals than the environment can support
Leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving
Observation #4: Members of a population vary extensively in their characteristics
No two individuals are exactly alike
This is the inference Darwin arrived at after reading Malthus.
Figure 22.9
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Observation #5: Much of this variation is heritable
Experiments in plant and animal breeding prove this.
Terminal Lateral buds bud Cabbage Brussels sprouts
Inference #2: Survival may depend in part on inherited traits
Individuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individuals
Inference #3: The unequal ability of individuals to survive and reproduce
Will lead to a gradual change in a population, with favorable characteristics accumulating over generations
Flower cluster
Leaves
This is the process called Natural Selection
All that is required for this process is heritable (that is, genetic) variation that affects fitness
Cauliflower
Kale
Flower and stems Broccoli Wild mustard
Stem Kohlrabi
Figure 22.10
Summary of Natural Selection
Natural selection is differential success in reproduction
That results from the interaction between individuals that vary in heritable traits and their environment
Natural selection can produce adaptations of organisms to their environment
(a) A flower mantid in Malaysia
(b) A stick mantid in Africa
Figure 22.11
Natural Selection in Action
If an environment changes over time
Natural selection may result in adaptation to these new conditions
Two examples
Darwins Finches HIV
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A case study: Natural Selection Darwins Medium Ground Finch
Seed eater living on Daphne Major Island Drought in 1977 caused 84% mortality Only large hard seeds remained for food
Evolution by Natural Selection
Requires heritable variation that affects fitness Predicts:
That survival or mortality should be related to some trait (lets guess beak size) of the organism. Variation in the trait is heritable.
Larger billed birds tend to survive (variation affected fitness)
Beak size is heritable
Offspring resemble their parents. Much of the variation in beak size is due to genetics
Daphne Major
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The Evolution of DrugResistant HIV
In humans, the use of drugs
Selects for pathogens that through chance mutations are resistant to the drugs effects
Researchers have developed numerous drugs to combat HIV
But using these medications select for viruses resistant to the drugs
Natural selection is a cause of adaptive evolution Ignoring evolution is dangerous to the public health
Percent of HIV resistant to 3TC
Patient No. 1 Patient No. 2
Patient No. 3
Weeks
Figure 22.13
Evolutionary Theory
Homology Provides a cohesive explanation for many kinds of observations
Homologies among organisms
Morphological Genetic
Homology
Is similarity resulting from common ancestry
Biogeography The fossil record
Anatomical Homologies
Homologous structures between organisms
Are anatomical resemblances that represent variations on a structural theme that was present in a common ancestor
Molecular Homologies
Biologists also observe homologies among organisms at the molecular level
Such as genes that are shared among organisms inherited from a common ancestor
Figure 22.14
Human
Cat
Whale
Bat
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Anatomical resemblances among species
Are generally reflected in their molecules, their genes, and their gene products
Species Human Rhesus monkey Mouse Percent of Amino Acids That Are Identical to the Amino Acids in a Human Hemoglobin Polypeptide 100%
The uniformity of the genetic code
Is another example of homology One of the most convincing pieces of evidence that all life on earth has a common ancestor
95%
87%
Chicken
69% 54%
Frog
Figure 22.16
Lamprey
14%
Homologies and the Tree of Life
The Darwinian concept of an evolutionary tree of life
Can explain the homologies that researchers have observed
Biogeography
Is the study of the geographic distribution of species
Formed an important part of his theory of evolution Explains why related species may today be found in disconnected places (with plate tectonics)
For example marsupials in S. America and Australia
Some similar mammals that have adapted to similar environments
Have evolved independently from different ancestors This is called convergent evolution the opposite of homology
The Fossil Record
The succession of forms observed in the fossil record
Is consistent with other inferences about the major branches of descent in the tree of life
Sugar glider
NORTH AMERICA
AUSTRALIA
Flying squirrel
Figure 22.17
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The Darwinian view of life
Predicts that evolutionary transitions should leave signs in the fossil record
What Is Theoretical about the Darwinian View of Life?
In science, a theory
Accounts for many observations and data and attempts to explain and integrate a great variety of phenomena
Paleontologists
Have discovered fossils of many such transitional forms
Darwins theory of evolution by natural selection
Integrates diverse areas of biological study and stimulates many new research questions
Figure 22.18
Resistance to the Idea of Evolution
The Origin of Species
Shook the deepest roots of Western culture Challenged a worldview that had been prevalent for centuries Continues to bother proponents of biblical versions of creation Questions whether God is necessary to explain the existence of life and man
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