Descent with Modification: A Darwinian View of Life

Descent with Modification: A Darwinian View of Life
Chapter 22 Descent with Modification: A Darwinian View of Life

Overview: Endless Forms Most Beautiful
A new era of biology began in 1859 when Charles Darwin published The Origin of Species The Origin of Species focused biologists’ attention on the great diversity of organisms © 2011 Pearson Education, Inc.

Darwin noted that current species are descendants of ancestral species
Evolution can be defined by Darwin’s phrase descent with modification Evolution can be viewed as both a pattern and a process © 2011 Pearson Education, Inc.

Figure 22.2 1809 Lamarck publishes his hypothesis of evolution. 1798 Malthus publishes “Essay on the Principle of Population.” 1812 1858 Cuvier publishes his extensive studies of vertebrate fossils. 1795 While studying species in the Malay Archipelago, Wallace (shown in 1848) sends Darwin his hypothesis of natural selection. Hutton proposes his principle of gradualism. 1830 Lyell publishes Principles of Geology. 1790 1870 1809 183136 1859 Charles Darwin is born. Darwin travels around the world on HMS Beagle. On the Origin of Species is published. Figure 22.2 The intellectual context of Darwin’s ideas. 1844 Darwin writes his essay on descent with modification. The Galápagos Islands

Scala Naturae and Classification of Species
The Greek philosopher Aristotle viewed species as fixed and arranged them on a scala naturae He thought since the Old Testament held that species were individually designed by God they were therefore perfect. Scala naturae- “scale of nature” © 2011 Pearson Education, Inc.

Carolus Linnaeus interpreted organismal adaptations as evidence that the Creator had designed each species for a specific purpose Linnaeus was the founder of taxonomy, the branch of biology concerned with classifying organisms He developed the binomial format for naming species (for example, Homo sapiens) © 2011 Pearson Education, Inc.

Qur’an, Surahs: The Light and The Bee
“And Allah has created every animal from water: of them there are some that creep on their bellies; some that walk on two legs; and some that walk on four.” 24 Light, 45 “Do they not look at the birds, held poised in the midst of…the sky? Nothing holds them up but (the power of) Allah.” 16 The Bee, 79

Bible/Torah, Book of Genesis, Chapt. 1
20 And God said, “Let the waters swarm with swarms of living creatures, and let birds[g] fly above the earth across the expanse of the heavens.” 21 So God created the great sea creatures and every living creature that moves, with which the waters swarm, according to their kinds, and every winged bird according to its kind. And God saw that it was good. 22 And God blessed them, saying, “Be fruitful and multiply and fill the waters in the seas, and let birds multiply on the earth.” 23 And there was evening and there was morning, the fifth day. 24 And God said, “Let the earth bring forth living creatures according to their kinds—livestock and creeping things and beasts of the earth according to their kinds.” And it was so. 25 And God made the beasts of the earth according to their kinds and the livestock according to their kinds, and everything that creeps on the ground according to its kind. And God saw that it was good. Aristotle and other philosophers, and later scientists interpreted the OT as saying that species were “fixed” because they were perfectly created by God. Therefore, evolution was impossible. According to Qur’an and the Bible do NOT state that animals do NOT change/evolve over time. It simply says that they are created according to their own kind. This means that evolution CAN occur, but it can’t occur to the point that one kind turns into another kind. Cats will remain cats, dogs remain dogs.

Evolution has been observed to occur within the same “kind” of organism. “Kind” can be likened with the Taxonomic level of CLASS

Ideas About Change over Time
The study of fossils helped to lay the groundwork for Darwin’s ideas Fossils are remains or traces of organisms from the past, usually found in sedimentary rock, which appears in layers or strata © 2011 Pearson Education, Inc.

Sedimentary rock layers (strata) Younger stratum with more recent
Figure 22.3 Sedimentary rock layers (strata) Figure 22.3 Formation of sedimentary strata with fossils. Younger stratum with more recent fossils Older stratum with older fossils

The different strata layers could be explained having different organisms because it’s the order in which the flood reach them. It would make sense that higher level animals would be able to run away and get buried last.

Paleontology, the study of fossils, was largely developed by French scientist Georges Cuvier
Cuvier, who also believed in God, advocated catastrophism, speculating that each boundary between strata represents a catastrophe © 2011 Pearson Education, Inc.

He concluded the Earth must be ancient
Gradualism- principle that profound change is the cumulative product of slow, continuous processes Gradualism challenged Charles Lyell’s principle of uniformitarianism states that the mechanisms of change are constant over time Although Darwin rejected this view, it strongly influenced his thinking He concluded the Earth must be ancient © 2011 Pearson Education, Inc.

Lamarck’s Hypothesis of Evolution
Lamarck hypothesized that species evolve through use and disuse of body parts and the inheritance of acquired characteristics The mechanisms he proposed are unsupported by evidence © 2011 Pearson Education, Inc.

Acquired Traits cannot be inherited
Figure 22.4 Acquired traits cannot be inherited.

Lamarkian Evolution Cheetahs can run faster than 60 miles per hour when in pursuit of prey. How would an evolutionary biologist explain how this ability evolved, assuming their ancestors could only run 20 miles per hour?

Concept 22.2: Descent with modification by natural selection explains the adaptations of organisms and the unity and diversity of life Some doubt about the permanence of species preceded Darwin’s ideas © 2011 Pearson Education, Inc.

Darwin’s Research As a boy and into adulthood, Charles Darwin had a consuming interest in nature Darwin first studied medicine (unsuccessfully), and then theology at Cambridge University After graduating, he took an unpaid position as naturalist and companion to Captain Robert FitzRoy for a 5-year around the world voyage on the Beagle © 2011 Pearson Education, Inc.

The Voyage of the Beagle
During his travels on the Beagle, Darwin collected specimens of South American plants and animals He observed that fossils resembled living species from the same region, and living species resembled other species from nearby regions He experienced an earthquake in Chile and observed the uplift of rocks © 2011 Pearson Education, Inc.

Figure 22.5 The voyage of HMS Beagle.
Darwin in 1840, after his return from the voyage HMS Beagle in port Great Britain EUROPE NORTH AMERICA ATLANTIC OCEAN The Galápagos Islands AFRICA PACIFIC OCEAN Pinta Genovesa Equator Marchena Malay Archipelago Equator SOUTH AMERICA PACIFIC OCEAN Santiago Daphne Islands Chile Brazil AUSTRALIA Fernandina Pinzón PACIFIC OCEAN Andes Mtns. Isabela Figure 22.5 The voyage of HMS Beagle. Darwin was influenced by Lyell’s Principles of Geology and thought that the earth was more than 6000 years old His interest in geographic distribution of species was kindled by a stop at the Galápagos Islands west of South America He hypothesized that species from South America had colonized the Galápagos and speciated on the islands Santa Cruz Cape of Good Hope Santa Fe San Cristobal Argentina Tasmania 20 40 Florenza Española Cape Horn Kilometers New Zealand

Darwin’s Focus on Adaptation
In reassessing his observations, Darwin perceived adaptation to the environment and the origin of new species as closely related processes From studies made years after Darwin’s voyage, biologists have concluded that this is what happened to the Galápagos finches © 2011 Pearson Education, Inc.

(a) Cactus-eater (b) Insect-eater (c) Seed-eater Figure 22.6
Figure 22.6 Three examples of beak variation in Galápagos finches. According to Galapagos presentation by Mr. T, how would you explain the rise of these three separate species? (c) Seed-eater

Descent with Modification
Darwin never used the word evolution in the first edition of The Origin of Species The phrase descent with modification summarized Darwin’s perception of the unity of life The phrase refers to the view that all organisms are related through descent from an ancestor that lived in the remote past © 2011 Pearson Education, Inc.

Is natural selection driven by the “Survival of the Fittest”???
In 1844, Darwin wrote an essay on natural selection as the mechanism of descent with modification, but did not introduce his theory publicly Natural selection is a process in which individuals with favorable inherited traits are more likely to survive and reproduce Is natural selection driven by the “Survival of the Fittest”??? In June 1858, Darwin received a manuscript from Alfred Russell Wallace, who had developed a theory of natural selection similar to Darwin’s Darwin quickly finished The Origin of Species and published it the next year © 2011 Pearson Education, Inc.

The Origin of Species Darwin explained three broad observations:
The unity of life The diversity of life The match between organisms and their environment © 2011 Pearson Education, Inc.

Darwin’s theory meshed well with the hierarchy of Linnaeus
In the Darwinian view, the history of life is like a tree with branches representing life’s diversity Darwin’s theory meshed well with the hierarchy of Linnaeus © 2011 Pearson Education, Inc.

Figure 22.7 Figure 22.7 “I think. . .”

Figure 22.8 Descent with modification. Elephas maximus (Asia)
Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) †Moeritherium †Barytherium †Deinotherium †Mammut †Platybelodon †Stegodon †Mammuthus Figure 22.8 Descent with modification. Elephas maximus (Asia) Loxodonta africana (Africa) Loxodonta cyclotis (Africa) 60 34 24 5.5 2 104 Millions of years ago Years ago

Darwin’s take on Malthus’ book
Observation #1: Species have such great fertility that their population would increase exponentially if they all reproduce © 2011 Pearson Education, Inc.

Figure 22.11 Spore cloud Figure Overproduction of offspring.

Observation #2: Most populations are stable in size
© 2011 Pearson Education, Inc.

Observation #3: Natural resources are limited

Inference: Production of more individuals than the environment can support leads to struggle for existence among individuals of a population

Observation #4: Individuals vary extensively in their characteristics

Observation #5: Much of this variation is heritable

Artificial Selection, Natural Selection, and Adaptation
Darwin noted that humans have modified other species by selecting and breeding individuals with desired traits, a process called artificial selection © 2011 Pearson Education, Inc.

Cabbage Brussels sprouts Broccoli Kale Wild mustard Kohlrabi
Figure 22.9 Cabbage Selection for apical (tip) bud Brussels sprouts Selection for axillary (side) buds Broccoli Selection for flowers and stems Figure 22.9 Artificial selection. Selection for stems Selection for leaves Kale Wild mustard Kohlrabi

Darwin was influenced by Thomas Malthus, who noted the potential for human population to increase faster than food supplies and other resources If some heritable traits are advantageous, these will accumulate in a population over time, and this will increase the frequency of individuals with these traits This process explains the match between organisms and their environment © 2011 Pearson Education, Inc.

Natural Selection: A Summary
Individuals with certain heritable characteristics survive and reproduce at a higher rate than other individuals Natural selection increases the adaptation of organisms to their environment over time If an environment changes over time, natural selection may result in adaptation to these new conditions and may give rise to new species © 2011 Pearson Education, Inc.

How would Lamarck and Darwin explain the mantids?
Figure Camouflage as an example of evolutionary adaptation. (a) A flower mantid in Malaysia (b) A leaf mantid in Borneo

Note that individuals do not evolve; populations evolve over time
Natural selection can only increase or decrease heritable traits that vary in a population Adaptations vary with different environments © 2011 Pearson Education, Inc.

Is Natural Selection able to occur?
No, N.S cannot occur since there is no variation within the stormtrooper clones

Concept 22.3: Evolution is supported by an overwhelming amount of scientific evidence
New discoveries continue to fill the gaps identified by Darwin in The Origin of Species © 2011 Pearson Education, Inc.

Direct Observations of Evolutionary Change
Two examples provide evidence for natural selection: natural selection in response to introduced plant species, and the evolution of drug-resistant bacteria © 2011 Pearson Education, Inc.

Explain the theory of evolution by natural selection as presented by Darwin. (5 points)
variation in populations adaptations: differences may enable some individuals to out-compete others differential survival: individuals with more favorable traits will be “selected” competition for food, nesting sites, mates, escape predators, survive disease/parasites survivors are then able to reproduce more and pass on favorable traits to (“survival of the fittest”) their offspring. individuals with favorable traits will make up a greater percentage of the population in the next generation.

Natural Selection in Response to Introduced Plant Species
Soapberry bugs use their “beak” to feed on seeds within fruits In southern Florida soapberry bugs feed on balloon vine with larger fruit; they have longer beaks In central Florida they feed on goldenrain tree with smaller fruit; they have shorter beaks Correlation between fruit size and beak size has also been observed in Louisiana, Oklahoma, and Australia © 2011 Pearson Education, Inc.

These cases are examples of evolution by natural selection
In all cases, beak size has evolved in populations that feed on introduced plants with fruits that are smaller or larger than the native fruits These cases are examples of evolution by natural selection In Florida this evolution in beak size occurred in less than 35 years © 2011 Pearson Education, Inc.

Soapberry bug with beak inserted in balloon vine fruit
Figure 22.13a FIELD STUDY Figure Inquiry: Can a change in a population’s food source result in evolution by natural selection? Soapberry bug with beak inserted in balloon vine fruit

On native species, southern Florida
Figure 22.13b RESULTS Beak 10 On native species, southern Florida 8 6 4 2 Number of individuals Museum-specimen average 10 8 On introduced species, central Florida Figure Inquiry: Can a change in a population’s food source result in evolution by natural selection? 6 4 2 6 7 8 9 10 11 Beak length (mm)

The Evolution of Drug-Resistant Bacteria
The bacterium Staphylococcus aureus is commonly found on people One strain, methicillin-resistant S. aureus (MRSA) is a dangerous pathogen S. aureus became resistant to penicillin in 1945, two years after it was first widely used S. aureus became resistant to methicillin in 1961, two years after it was first widely used © 2011 Pearson Education, Inc.

MRSA bacteria use a different protein in their cell walls
Methicillin works by inhibiting a protein used by bacteria in their cell walls MRSA bacteria use a different protein in their cell walls When exposed to methicillin, MRSA strains are more likely to survive and reproduce than nonresistant S. aureus strains MRSA strains are now resistant to many antibiotics © 2011 Pearson Education, Inc.

Chromosome map of S. aureus clone USA300
Figure 22.14 1 2,750,000 250,000 base pairs 2,500,000 Chromosome map of S. aureus clone USA300 500,000 2,250,000 Key to adaptations Methicillin resistance Ability to colonize hosts 750,000 Increased disease severity 2,000,000 Increased gene exchange (within species) and toxin production Figure Impact: The Rise of MRSA 1,000,000 1,750,000 1,250,000 1,500,000

Antibiotic gene already present
Explain how evolution by natural selection can explain emergence of MRSA. Antibiotic gene already present Environmental pressure (antibiotics) present Bacteria with antibiotic resistance will be selected for, those without will be selected against Bacteria with resistance will have a higher fitness (reproductive success) Time- generations of bacteria will see MRSA become more prevalent Acquired traits can NOT be passed on, unless it is due to a DNA tag (methylation or acetylation)--epigenome

Normal bacterium usually outgrow their

Natural selection does not create new traits, but edits or selects for traits already present in the population The local environment determines which traits will be selected for or selected against in any specific population © 2011 Pearson Education, Inc.

Lamarkian or Darwinian?
Population of individuals all of the same kind (identical characteristics in all members). Individuals capable of transformation

Darwinian Population of interbreeding individuals with similar characteristics, though variation is common among all of them at all times. Individuals fixed and unchanging. Population capable of transformation.

Lamarkian or Darwinian?
Keen eyesight of the hawk: “In a population of hawks, the power of their vision and the color of their feathers are necessary to successfully catch food. Since nature pressured hawks to possess keen eyesight and camouflaging coloration, individual hawks began to develop the ability of keen eyesight and camouflage. Those who adapted with the necessary traits could more easily spot their prey (small voles and mice) and thus were successful in securing food to eat. The hawks that failed to adapt, due to poor eyesight had difficulty spotting prey and died for lack of food. The hawks with the keen eyesight passed on this trait to their offspring. The hawks that died were not able to produce any offspring. Over a number of generations, the population of hawks all came to possess extremely powerful vision."

Darwinian Keen eyesight of the hawk: “In a population of hawks, individual variation existed in the power of their vision, just as variation exists in the color of their feathers. In their competition for food, the individuals with keener eyesight could more easily spot their prey (small voles and mice) and thus were successful in securing food to eat. The hawks with poor eyesight had difficulty spotting prey and died for lack of food. The hawks with the keen eyesight passed on this trait to their offspring. The hawks that died were not able to produce any offspring. Over a number of generations, the population of hawks all came to possess extremely powerful vision."

Which takes less faith? Naturalism Theistic Evolution Supernaturalism
Evolution can occur with enough time, mutations, and natural selection

Evidence from many fields of Biology for Evolution
Biogeography Fossil Record Comparative Anatomy Comparative embryology Molecular Biology

Biogeography Biogeography, the geographic distribution of species, provides evidence of evolution Earth’s continents were formerly united in a single large continent called Pangaea, but have since separated by continental drift An understanding of continent movement and modern distribution of species allows us to predict when and where different groups evolved © 2011 Pearson Education, Inc.

Biogeography

Biogeography does provide evidence for microevolution
Biogeography does provide evidence for microevolution. As species migrate and become isolated from other populations, microevolution occurs. Natural selection will be different in different environments. Different pressures will select different combinations of phenotypes. But does biogeography provide evidence for macroevolution? Evolution that takes one “class” to give birth to a new “class”?

The more recent, the more complex; the older, the simpler

Coelocanth Thought to be extinct with dinosaurs for 65 million years
Coelacanths are elusive, deep-sea creatures, living in depths up to 2,300 feet (700 meters) below the surface. They can be huge, reaching 6.5 feet (2 meters) or more and weighing 198 pounds (90 kilograms). Scientists estimate they can live up to 60 years or more.

Anything Into Oil Technological savvy could turn 600 million tons of turkey guts and other waste into 4 billion barrels of light Texas crude each year.

Trilobites Darwin discovered fossils of marine animals in the Andes mountains (elevation up to 23,000 ft or about 4 miles) Great Earthquake or Flood?

“Why then is not every geological formation and every stratum full of such intermediate links? Geology assuredly does not reveal any such finely graduated organic chain; and this, perhaps, is the most obvious and gravest objection which can be urged against my theory. The explanation lies, as I believe, in the extreme imperfection of the geological record.” -Charles Darwin (1859), The Origin of Species, p. 280.

Other even-toed ungulates
Figure 22.20 Other even-toed ungulates Hippopotamuses †Pakicetus †Rodhocetus Common ancestor of cetaceans †Dorudon Figure The transition to life in the sea. Living cetaceans 70 60 50 40 30 20 10 Key Pelvis Tibia Millions of years ago Femur Foot

Fossil remains of Pakicetus (found in Pakistan)
Fossil remains of Pakicetus (found in Pakistan). Land animals transition back into the water.

Ambulocetus Ambulocetus

Rodhocetus Rodhocetus

Stanley worked at the university of Hawaii at Manoa. PhD from Yale

Anatomical and Molecular Homologies
Homologous structures are anatomical resemblances that represent variations on a structural theme present in a common ancestor © 2011 Pearson Education, Inc.

Humerus Radius Ulna Carpals Metacarpals Phalanges Human Cat Whale Bat
Figure 22.15 Humerus Radius Ulna Carpals Metacarpals Figure Mammalian forelimbs: homologous structures. Phalanges Human Cat Whale Bat

‘If you look at a 1953 Corvette and compare it to the latest model, only the most general resemblances are evident, but if you compare a 1953 and a 1954 Corvette, side by side, then a 1954 and a 1955 model, and so on, the descent with modification is overwhelmingly obvious. This is what paleontologists do with fossils, and the evidence is so solid and comprehensive that it cannot be denied by reasonable people’ -Dr. Tim Berra, professor of Zoology, Ohio State University Evidence of descent with modification from a common ancestor? Or evidence from a common Designer?

Question to ponder at the biochemical level…
If so many homologies exist today due to millions of years of evolution, why do we not see more of a difference at the biochemical level? We still observe the same genetic code, the same 20 amino acids, the same process of transcription and translation, etc.

Homologies and “Tree Thinking”
Evolutionary trees are hypotheses about the relationships among different groups Homologies form nested patterns in evolutionary trees Evolutionary trees can be made using different types of data, for example, anatomical and DNA sequence data © 2011 Pearson Education, Inc.

Homologous characteristic
Figure 22.17 Branch point Lungfishes Amphibians 1 Tetrapods 2 Mammals Digit- bearing limbs Amniotes 3 Lizards and snakes Amnion 4 Crocodiles Homologous characteristic Figure Tree thinking: information provided in an evolutionary tree. 5 Ostriches 6 Birds Feathers Hawks and other birds

A Different Cause of Resemblance: Convergent Evolution
Convergent evolution is the evolution of similar, or analogous, features in distantly related groups Analogous traits arise when groups independently adapt to similar environments in similar ways Convergent evolution does not provide information about ancestry © 2011 Pearson Education, Inc.

Convergent Evolution? The Gray wolf and Tasmanian tiger (Australia, extinct 1936) are structural similar, yet supposedly evolution over millions of years from a common ancestor. So why do they look so similar? Analogous- no recent common ancestor, yet by chance, the similar environmental pressures brought about similar phenotypes

“Wings” homologous or analogous?
NORTH AMERICA Sugar glider Figure Convergent evolution. AUSTRALIA Flying squirrel

Homologous or Analogous?
Rainbow rose- artificially colored (plant takes up chemicals through water up stems)

180 vestigial structures named in 1890
Vestigial structures are remnants of features that served important functions in the organism’s ancestors Examples of homologies at the molecular level are genes shared among organisms inherited from a common ancestor 180 vestigial structures named in 1890 © 2011 Pearson Education, Inc.

Problem with Vestigial structures
There were once over hundred parts of the human anatomy that were considered vestigial, or useless. Here are a few that over the past couple decades have been deemed “useful”: Spleen Tonsils Appendix Coccyx (Tailbone) Spleen-immune system Tonsils-immune system Appendix-storehouse of beneficial bacteria

“Ontogeny Recapitulates Phylogeny” Ontogeny- growth and development Recapitulates- summarizes Phylogeny- evolutionary history Ontogeny-growth, development of an organism Recapitulate- summarize Phylogeny- evolutionary history of a species Embryological development can be used as a type of homology between two different species to trace back common ancestry. For example, humans (chordates) are thought to be closer related to the starfish than any other invertebrate (mollusks, insects, worms, etc) because of similar stages in embryonic development

Phylogenetic Tree- notice chordata and echinodermata

Chordates are grouped based upon those who produce an amnion.

Pharyngeal arches Post-anal tail Chick embryo (LM) Human embryo
Figure 22.16 Pharyngeal arches Post-anal tail It’s one thing to look at gill slits of fish, amphibians, reptiles, and mammals and see they all turn into different breathing mechanisms but they don’t. Likewise, the yolk sac present in birds and reptiles does not fuction as yolk sac in mammals Finally, the post-anal tail in birds and reptiles, does not form a tail or even a vestigial structure, but helps form the coccyx. Figure Anatomical similarities in vertebrate embryos. Embryology can be at bit misleading. The Pharyngeal arches (sometimes referred to as gill slits) are suggested to be the same structures that millions of years ago developed into the gills of our ancestor the fish. However, in terrestrial mammals they develop into the jaw and inner ear. Nothing related to breathing. In addition, the embryonic tail which developed into tails in our ancestors, although still called a tail in human embryology, does not turn into a tail, but develops into our coccyx. Lastly, the yolk sac that appears in amniotes, in birds may serve as a food source, but in humans it provides the first blood cells Chick embryo (LM) Human embryo

Molecular Biology

How much difference overall?
Humans and chimps are 96% identical in our DNA sequence. That 4% represents a total number of DNA differences of about 125 million “To put this number into perspective, a typical 8½ x 11-inch page of text might have 4,000 letters and spaces. It would take 10,000 such pages full of text to equal 40 million letters! So the difference between humans and chimpanzees includes about 35 million DNA bases that are different, about 45 million in the human that are absent from the chimp, and about 45 million in the chimp that are absent from the human” -Dr. David DeWitt

What Is Theoretical About Darwin’s View of Life?
In science, a theory accounts for many observations and data and attempts to explain and integrate a great variety of phenomena Darwin’s theory of evolution by natural selection integrates diverse areas of biological study and stimulates many new research questions Ongoing research adds to our understanding of evolution © 2011 Pearson Education, Inc.

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