EVOLUTION Dr Asl Tolun Dept Mol Biol and

EVOLUTION Dr. Aslı Tolun Dept. Mol. Biol. and Genetics April-May 2010 Science 102

EVOLUTION The most important theory in biology: The unifying theory. Not a hypothesis. Theory: NOT a speculation!! A statement of well-supported general laws, principles and causes of something known or observed. T. Dobzhansky in 1973: “Nothing in biology makes sense, except in the light of evolution. ”

CONCEPTS in SCIENCE Fact: An observation that has been repeatedly confirmed. Law: A descriptive generalization about how some aspects of the natural world behave under stated circumstances. Hypothesis: A testable statement about the natural world that can be used to build more complex inferences and explanations. Theory: A well-substantiated explanation of some aspects of the natural world that can incorporate facts, laws, inferences and tested hypotheses.

IN SCIENTIFIC RESEARCH You can: Perform experiments. Observe. Science: testable! No dogma.

EVOLUTION Individuals in a population have differences. The differences are heritable. Natural selection and elimination. Leads to speciation. A common ancestor for all species.

EVOLUTION is a FACT There is no (scientific) evidence against it. All scientists accept evolution. No “believing in” evolution, but “accepting evolution as a fact”.

CONSEQUENCES The fittest survives Selection works on it Evolution. Final outcome: Usually not perfect!

Vertebral column is not well adapted to vertical posture. A: A better arrangement in squid eye: axons arise from rear of retinal cells, so eye is more efficient plus there is no blind spot. B: Vertebrate eye with blind spot: nerve cell extentions arise from front of retinal cells to form optic nerve.

FINAL CONSEQUENCE: SPECIATION • All known species are descended from common ancestors. • Their relationships can be described as a branching tree (phylogeny) in which each fork represents divergence from a common ancestor into two different lineages. • Each lineage evolves various differences from other lineages and eventually leads to a new species. • Similarities between lineages are due to inheritance. THE THREE DOMAINS:

MECHANISMS OF SPECIATION • Geographic isolation. • Seasonal isolation. • Ethological isolation (behavioral incompatibilities). • Mechanical isolation. • Genetic changes leading to hybrid sterility. EXAMPLE for SPECIES RELATIONS:

DIVERGENCE vs CONVERGENCE D: Features diverge but retain the basic structures. Human arm vs horse leg. C: Distantly related species can evolve features that serve the same function and are seemingly similar. Bat wing vs insect wing.

Change in form with similar function

IS EVOLUTION POSSIBLE? Yes, if sufficient time passes. . .

IMPORTANCE of SCIENCE SCIENTIFIC THOUGHT IS BENEFICIAL Understanding humans: genes, development, function Applications for human health Understanding the evolution of microbes Applications in agriculture, pest control Biotechnology Utilizing natural resources (GAP) Leading a rational life.

WHY IS THERE OPPOSITION? In the 17 th and 18 th centuries, science was not developed. Bible: Earth was created in 4004 BC. All life forms were created as they are today, perfectly adapted to each other and to environment. Creation story is important for Christianity. But last year. . .

CONTRIBUTORS to MODERN SCIENCE Copernicus 1473 -1543 Galileo 1564 -1642 Newton 1642 -1727 Lamarck: directional change In 1860 s: biologists and geologists accepted evolution as a fact. Mechanism? Purpose?

CHARLES DARWIN 1809 – 1882. A naturalist. His father was a physician Grandfather Erasmus Darwin a physicist Education: Two years in medicine, later for a ministry. 1839 married his cousin, 10 children, – 2. 25

HMS BEAGLE • • • A navy survey ship South America in Dec 1831, 5 years. Collected specimens: fossils and living Driving force: curiosity Observation capacity Hard work.

HIS MOST IMPORTANT BOOKS Total of 25 books. Best known are: 1839 Excursions in Beagle, 3 volumes "Journal of Researches into the Natural History and Geology of the Countries Visited During the Voyage of H. M. S. Beagle”. Authors: Kaptan Philip King, Kaptan Robert Fitz. Roy ve Charles Darwin. 1859 "The Origin of Species by Means of Natural Selection: Or, the Preservation of Favored Races in the Struggle for Life”. 1871 "The Descent of Man and Selection in Relation to Sex”. 27

Charles Darwin The Origin of Species As more individuals are produced than can possibly survive … Can it be thought improbable, seeing that variations useful to man have undoubtedly occurred, that other variations useful in some way to each being in the great and complex battle of life, should sometimes occur in the course of thousands of generations? If such do occur, can we doubt that individuals having any advantage, however slight, over others, would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favorable variations and the rejection of injurious variations, I call Natural Selection.

INSPIRED by THOMAS MALTHUS Thomas Malthus (1766 -1834) in 1798: “Food is necessary to the existence of man. Secondly, that the passion between the sexes is necessary, and will remain nearly in its present state”. Populations tend to increase faster than the increase in resources. “This implies a strong and constantly operating check on populations from the difficulty of subsistence. ”

DARWIN’S HYPOTHESES ON COMMON ANCESTRY 1. Single origin of known life (or few origins) 2. Repeated branching of lineages (speciation) 3. Each lineage may acquire more differences over time, hence 4. Lineages gradually diverge (become more different), so 5. Very similar species are likely to have a recent common ancestor; more different species are likely to have a less recent (more remote) common ancestor.

Phylogenies form the basis for Hypotheses and Predictions In each great region of the world the living mammals are closely related to the extinct species of the same region. It is therefore probable that Africa was formerly inhabited by extinct apes closely allied to the gorilla and chimpanzee; and as these two species are now man’s nearest allies, it is somewhat more probable that our early progenitors lived on the African continent than elsewhere. Charles Darwin, 1871, The Descent of Man DO WE COME FROM MONKEYS? ?

GALAPAGOS ISLANDS • Similar land • Similar geography • Different species.

WHY IS EVOLUTION DARWIN’S? His work was scientific, intensive and explained evolution best. 1859: On the Origin of Species Evolution was accepted within a few years.

IMPACT OF EVOLUTION • Understanding biology, thus the world. • Establishment of scientific thought • Secularization of science and education.

EVIDENCE for EVOLUTION

SUPPORTING SCIENCES • Fossils – extinct species, ancestral species • Geology – the age of earth • Voyages • Classifications: Carl von Linné 39

EVIDENCE for EVOLUTION A. Homologous characters. A feature in two or more species is homologous when it is derived from the same feature of their nearest common ancestor. Wings of bats vs of flies

HOMOLOGY

EVIDENCE for EVOLUTION B. Reapitulation – appearance and subsequent loss of structures in ontology, which in related taxa are attained in the adults. Embryos of the baleen whales develop teeth that are observed later. Embryos of birds and mammals develop gill slits.

EVIDENCE for EVOLUTION C. Vestigial structures. Eyes in cave animals, human appendix, leg bones in snakes etc. → Common descent, variation, selection. D. Embryology – embryos of all vertebrates are similar.

Vestigial eye of cave fish, Astyanax mexicanus Figure 2 Surface dwelling (eyed) and cave-dwelling (eyeless) forms of Astyanax mexicanus. Adjacent to them are sections of the embryonic eyes, stained with a reagent (TUNEL) that binds to and stains DNA fragments produced by apoptosis. A 1. Surface form with eyes and pigmentation. A 2. 25 hour embryo of surface form, showing very little apoptosis in the lens. B 1. Cavefish from La Cueva Chica with reduced eyes and reduced pigmentation. B 2. 25 hour embryo of the Chica cave-dwelling form, showing severe apoptosis in the lens vesicle (arrowhead). C 1. Cavefish from Cueva de El Pachón showing neither eye nor pigmentation. C 2. Apoptosis in lens and corneal epithelium in the 25 hour embryo of the Cueva de El Pachón cavefish. (After Jeffery and Martasian, 1998. ) Apoptosis = Programmed cell death

EVIDENCE for EVOLUTION E. Biogeography. Similarities in fauna and flora in parallel with geological history. Dispersal.

Many oceanic islands lack organisms such as mammals and snakes that thrive there after being introduced by humans. Why weren’t there any mammals or snakes before introduction? Placentals vs marsupials Mongoose Brown tree snake

EVIDENCE for EVOLUTION F. Molecular evidence: a single ancestral cell and similarity in genomes. G. Imperfections. H. Fossils.

Archaeopteryx (B), intermediate between dinosaurs and birds, found in 19 th century. Recently, many other intermediates, such as Microraptor (top). Birds descended from dinosaurs; they ARE feathered dinosaurs!

Stages in evolution from lobe-finned fishes to tetrapods Note similarities and changes in skull Tiktaalik

EVIDENCE for EVOLUTION I. Artificial selection. J. Similarities in similar features.

Stages of eye complexity in mollusks (limpet Patella)

(slit shell mollusk Pleurotomaria)

HUMAN EVOLUTION

CHARACTERISTICS of APES and HUMANS • Posture: Bent over or quadrupedal, “knuckle-walking” common / upright, bipedal • Leg and arm length: arms longer than legs, arms adapted for swinging • Feet: Opposable big toes, capable of grasping / adapted for walking • Teeth: prominent / reduced • Skull: bent forward from spinal column / held upright

CHARACTERISTICS of APES and HUMANS • Face: sloping, jaws jut out, wide nasal opening / chin • Brain size: 280 to 705 cm 3 / 400 to 2000 cm 3 (fossil to present) • Amount of hair cover • Spine straight / S-shaped • No language / language

HUMAN EVOLUTION kafalar

HUMAN EVOLUTION About 40 000 years ago, at least 4 species of Homo • • Sapiens Neanderthals Flores people Altai.

WE KNOW THE GENES FOR Brain expansion Speech

Most relationships among primates that had been proposed, based on morphological data, have been supported by DNA sequences. The DNA sequences do not reflect adaptation of morphologically similar species to similar environments, because the same result is obtained from nonfunctional DNA sequences, such as the hemoglobin pseudogene.

Australopithecus afarensis, ca. 3. 5 million years Tanzania

DO NEW MUTATIONS OCCUR? • Duchenne type muscular dystrophy: – 1 in 3500 boys – 1/3 are new mutations • Hemophilia, achondraplasia etc. • Most are eliminated. 29 Eylül 2009 Kocaeli Üniversitesi 68

29 Eylül 2009 Kocaeli Üniversitesi 69

NOT ALL MUTATIONS ARE ELIMINATED ELIMINATION DOES NOT WORK ON: • Huntington disease • Osteoporosis • Most heart diseases Why? 70

AN EXAMPLE SICKLE CELL ANEMIA and THALLASEMIA • Heterozygotes are resistant to malaria SELECTION! 71

Red blood cells with normal hemoglobin and with sickle-cell hemoglobin

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OTHER RESISTANCES • Several genetic diseases Also, infectious diseases: • Tuberclosis, lepra, AIDS etc. Even to parasites, such as worms. 74

GENETIC SUSCEPTIBILITY • Diseases: heart disease, cancer etc. • Obesity • Alcoholism • Suicide • Aggression 75

ACKNOWLEDGMENT Douglas J. Futuyma, State University of New York. Boğaziçi University lecture in 2007. Francisco J. Ayala, University of California xx. Boğaziçi University lecture in 2009.