Evolution : processes that have transformed life on

Evolution : processes that have transformed life on
Earth from its earliest forms to the vast diversity that characterizes it today. *diversity of organisms *origins and relationships *similarities and differences *geographical distribution *adaptations to surrounding environment

What you must know: How Lamarck’s view of the mechanism of evolution differed from Darwin’s. The role of adaptations, variation, time, reproductive success, and heritability in evolution.

Descent with Modification
Theme: Evolutionary change is based on the interactions between populations & their environment which results in adaptations (inherited characteristics) to increase fitness Evolution = change over time in the genetic composition of a population

Historical Process of Science
Aristotle: life-forms arranged on scale on increasing complexity (scala naturae) Aristotle B.C.

Linnaeus: founder of taxonomy; binomial nomenclature
Domain – Kingdom – Phylum – Class – Order – Family - Genus – Species (Dear King Philip Came Over For Good Spaghetti) Domains = Bacteria, Archaea, Eukarya Classification based on anatomy & morphology Carolus Linnaeus

DOMAIN Kingdom Country Phylum State Class County Order Town
Family Neighborhood Genus Street Species House Number

Paleontologist – studied fossils
Cuvier: Paleontologist – studied fossils Deeper strata (layers) - very different fossils from current life Opposed idea of evolution Catastrophism – catastrophe destroyed many living species, then repopulated by immigrant species George Cuvier ( )

Created by impressions of organisms that existed in the past
Fossils in sedimentary rock – show succession of organisms through time (includes transitional forms and extinctions) Fossil record Slow and subtle processes persisting for long periods of time can add up to substantial change - Geology records this before ‘evolutionary’ theories (plate tectonics, mountain building/erosion……) Darwin’s views were influenced by fossils, the relics or impressions of organisms from the past, mineralized in sedimentary rocks. Sedimentary rocks form when mud and sand settle to the bottom of seas, lakes, and marshes. New layers of sediment cover older ones, creating layers of rock called strata. Fossils within layers show that a succession of organisms have populated Earth throughout time. Paleontology, the study of fossils, was largely developed by Georges Cuvier, a French anatomist. In particular, Cuvier documented the succession of fossil species in the Paris Basin. Cuvier recognized that extinction had been a common occurrence in the history of life. Instead of evolution, Cuvier advocated catastrophism, that boundaries between strata were due to local flood or drought that destroyed the species then present. Later, this area would be repopulated by species immigrating from other unaffected areas. In contrast to Cuvier’s catastrophism, James Hutton, a Scottish geologist, proposed that the diversity of land forms (e.g., canyons) could be explained by mechanisms currently operating. Hutton proposed a theory of gradualism, that profound change results from slow, continuous processes. Later, Charles Lyell, proposed a theory of uniformitarianism, that geological processes had not changed throughout Earth’s history. Hutton’s and Lyell’s observations and theories had a strong influence on Darwin. First, if geological changes result from slow, continuous processes, rather than sudden events, then the Earth must be far older than the 6000 years assigned by theologians from biblical inference. Second, slow and subtle processes persisting for long periods of time can add up to substantial change.

Formation of sedimentary strata with fossils

Slow & subtle changes in organisms  big change
Hutton / Lyell: Gradualism = geologic change results from slow & gradual, continuous process Uniformitarianism = Earth’s processes same rate in past & present  therefore Earth is very old Slow & subtle changes in organisms  big change James Hutton Charles Lyell

Jean-Baptiste Lamarck 1744-1829
Published theory of evolution (1809) Use and Disuse: parts of body used  bigger, stronger (eg. giraffe’s neck) Inheritance of Acquired Characteristics: modifications can be passed on Importance: Recognized that species evolve, although explanation was flawed

Jean Baptiste Lamarck: the outcaste!
used the fossil record as evidence proposed a theory of evolution where organisms became better and better Mechanism - ”use” and “disuse” leads to: inheritance of acquired characteristics (you ‘acquire’ a phenotype in your lifetime and pass it on to your kids) also means environmental influences can be inherited Darwin’s views were influenced by fossils, the relics or impressions of organisms from the past, mineralized in sedimentary rocks. Sedimentary rocks form when mud and sand settle to the bottom of seas, lakes, and marshes. New layers of sediment cover older ones, creating layers of rock called strata. Fossils within layers show that a succession of organisms have populated Earth throughout time. Paleontology, the study of fossils, was largely developed by Georges Cuvier, a French anatomist. In particular, Cuvier documented the succession of fossil species in the Paris Basin. Cuvier recognized that extinction had been a common occurrence in the history of life. Instead of evolution, Cuvier advocated catastrophism, that boundaries between strata were due to local flood or drought that destroyed the species then present. Later, this area would be repopulated by species immigrating from other unaffected areas. In contrast to Cuvier’s catastrophism, James Hutton, a Scottish geologist, proposed that the diversity of land forms (e.g., canyons) could be explained by mechanisms currently operating. Hutton proposed a theory of gradualism, that profound change results from slow, continuous processes. Later, Charles Lyell, proposed a theory of uniformitarianism, that geological processes had not changed throughout Earth’s history. Hutton’s and Lyell’s observations and theories had a strong influence on Darwin. First, if geological changes result from slow, continuous processes, rather than sudden events, then the Earth must be far older than the 6000 years assigned by theologians from biblical inference. Second, slow and subtle processes persisting for long periods of time can add up to substantial change. In 1809, Jean Baptiste Lamarck published a theory of evolution based on his observations of fossil invertebrates in the Natural History Museum of Paris. Lamarck thought that he saw what appeared to be several lines of descent in the collected fossils and current species. Each was a chronological series of older to younger fossils leading to a modern species. Central to Lamarck’s mechanism of evolution were the concepts of use and disuse of parts and of inheritance of acquired characteristics. The former proposed that body parts used extensively to cope with the environment became larger and stronger, while those not used deteriorated. The latter proposed that modifications acquired during the life of an organism could be passed to offspring. A classic example of these is the long neck of the giraffe in which individuals could acquire longer necks by reaching for leaves on higher branches and would pass this characteristic to their offspring. Lamarck’s theory was a visionary attempt to explain both the fossil record and the current diversity of life through its recognition of the great age of Earth and adaptation of organisms to the environment. However, there is no evidence that acquired characteristics can be inherited. Acquired traits (e.g., bigger biceps) do not change the genes transmitted by gametes to offspring.

NOW, Epigenetics makes Lamarck a new Hero!!!!

More babies born than deaths
Malthus: More babies born than deaths Consequences of overproducing within environment = war, famine, disease (limits of human pop.) Struggle for existence Thomas Malthus ( )

HMS Beagle

Who was Charles Darwin? Captain Fitzroy’s traveling companion on the Beagle Was a ‘substitute’ and almost did not get on the HMS Beagle Geologist, zoologist, paleontologist, naturalist Author of the book “Origin of the Species” Said - writing it was “Like Confessing a Murder”! Hated Medicine Hated Confrontations Spent time collecting beetles, catching rats, ….. Hated being in the ministry Was called a “disgrace to the family” by his father Robert Darwin! could not stand dissections or amputations withour anesthesia - did not tell his dad that he hated medicine, would shoot birds intead when he came home from collegeCharles Darwin ( ) was born in western England. While Darwin had a consuming interest in nature as a boy, his father sent him to the University of Edinburgh to study medicine. Darwin left Edinburgh without a degree and enrolled at Christ College at Cambridge University with the intent of becoming a clergyman. At that time, most naturalists and scientists belonged to the clergy and viewed the world in the context of natural theology. Darwin received his degree in 1831. After graduation Darwin was recommended to be the conversation companion to Captain Robert FitzRoy, preparing the survey ship Beagle for a voyage around the world. FitzRoy chose Darwin because of his education, his similar social class, and similar age as the captain. On November 24, 1959, Charles Darwin published On the Origin of Species by Means of Natural Selection. Darwin’s book drew a cohesive picture of life by connecting what had once seemed a bewildering array of unrelated facts. Darwin made two points in The Origin of Species: Today’s organisms descended from ancestral species. Natural selection provided a mechanism for evolutionary change in populations.

Charles Darwin (1809-1882) English naturalist
1831: joined the HMS Beagle for a 5-year research voyage around the world Collected and studied plant and animal specimens, bones, fossils Notable stop: Galapagos Islands

HMS Beagle ( )

Galapagos Islands

Darwin’s Finch Collection
The birds were all about the same size, but the shape and size of the beaks of each species were different.

The vice-governor of the Galapagos Islands told Darwin that he could tell which island a particular tortoise came from by looking at its shell. Giant Tortoise

Darwin waited 30 years before he published his ideas on evolution
Alfred Russell Wallace – published paper on natural selection first (1858) Charles Darwin (1859): On the Origin of Species by Means of Natural Selection Mechanism for evolution is Natural Selection Darwin didn’t use “evolution”, but rather “descent with modification”

“On the Origin of Species by Means of Natural Selection” By Charles Darwin (1859)

Adaptations enhance an organism’s ability to survive and reproduce
Eg. Desert fox - large ears, arctic fox - small ears Overproduction of offspring leads to competition for resources

Natural Selection Artificial Selection Nature decides “Man” decides Works on individual Selective breeding Inbreeding occurs eg. beaks eg. dalmations Therefore, if humans can create substantial change over short time, nature can over long time.

Key Ideas of Natural Selection:
Competition for limited resources results in differential survival. Evolutionary Fitness: Individuals with more favorable phenotypes more likely to survive and produce more offspring, and pass traits to future generations If environment changes or individuals move to new environment, new adaptations and new species may arise. Populations evolve, not individuals.

VOYAGE OF THE HMS BEAGLE : 1831 - 1836
The Origin of Species challenged a worldview that had been accepted for centuries. The key classical Greek philosophers who influenced Western culture, Plato and Aristotle, opposed any concept of evolution. Plato believed in two worlds: one real world that is ideal and perfect and an illusory world of imperfection that we perceive through our senses. Aristotle believed that all living forms could be arranged on a ladder (scala naturae) of increasing complexity with every rung taken with perfect, permanent species. The Old Testament account of creation fortified the idea that species were individually designed and did not evolve. In the 1700’s, the dominant philosophy, natural theology, was dedicated toward studying the adaptations of organisms as evidence that the Creator had designed each species for a purpose. At this time, Carolus Linnaeus, a Swedish botanist, developed taxonomy, a system for naming species and grouping species into a hierarchy of increasingly complex categories. Darwin had the freedom to explore extensively on shore while the crew surveyed the coast. He collected thousands of specimens of the exotic and diverse flora and fauna of South America. Darwin’s explorations ranged from the Brazilian jungles, the grasslands of the Argentine pampas, the desolation of Tiera del Fuego, and the heights of the Andes. VOYAGE OF THE HMS BEAGLE :

While on the Beagle, Darwin read Lyell’s Principles of Geology.
Lyell’s ideas and his observations on the voyage lead Darwin to doubt the church’s position that the Earth was static and only a few thousand years old. Instead, he was coming to the conclusion that the Earth was very old and constantly changing. After his return to Great Britain in 1836, Darwin began to perceive that the origin of new species and adaptation of species to the environment as closely related processes. For example, among the 13 types of finches that Darwin collected in the Galapagos, clear differences in the beak are adaptations to the foods available on their home islands.

Observation: 13 or so species of finches on different Galapagos islands; these finches resembled the South American (mainland) finches more than say finches in Asia…. Darwin noted that the plants and animals of South America were very distinct from those of Europe. Organisms from temperate regions of South America were more similar to those from the tropics of South America than to those from temperate regions of Europe. Further, South American fossils more closely resembled modern species from that continent than those from Europe. The origin of the fauna of the Galapagos, 900 km west of the South American coast, especially puzzled Darwin. On further study after his voyage, Darwin noted that while most of the animal species on the Galapagos lived nowhere else, they resembled species living on the South American mainland. It seemed that the islands had been colonized by plants and animals from the mainland that had then diversified on the different islands.

Can you summarize how EVOLUTION occurred to produce separate populations of large and medium beaked Ground Finches in Galapagos Islands?

Medium Ground Finch (smaller beak)
medium ground finch lives on seeds, cracks them open via force of beak the Grant's studied finches on Daphne Major, an small island (800 sq. yd) in 1977 island had only 2mm of rain instead of normal 130mm... drought resulted in a loss of 84% of medium ground finch population most died of starvation, seeds of Tribulus cistoides, primary food source --> were hard to open unless birds had large, deep beaks, [the survivors had deeper beaks] Natural Selection lead to increase in average beak depth of survivors (graph of data*) Offspring of survivors in subsequent years had beaks 0.5mm deeper back Large Ground Finch (Larger Beak)

Speciation/Macroevolution: Evolution of distinct species (that cannot mate)
One population of birds on one island

After a long time, there are now 2
islands and 2 populations with a reproductive barrier (geographic). many insects in tree lots of plants (with holes hard to crack seeds)

The birds adapt to their niche and cannot mate anymore = 2 different species!
many insects=long lots of plants with beak seeds=large beak

Microevolution: changes in allele frequencies (=how often you see a particular phenotype) from generation to generation

What did Darwin Say? Descent with modification (diverse life forms have risen from a common ancestor) (the CONCLUSION) Descent occurs through the process of Natural selection (the HOW?) Evolution as the explanation for life’s unity and diversity The Darwinian view of life has two main features. (1) The diverse forms of life have arisen by descent with modification from ancestral species. (2) The mechanism of modification has been natural selection working over enormous tracts of time.

Individuals in a population have varying characteristics.
Observations: Individuals in a population have varying characteristics. Much of this variation is heritable. Inferences: Survival depends on inheriting the “best fit” physical traits (“reproductive fitness”) This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over the generations. Observation #4: Individuals of a population vary extensively in their characteristics; no two individuals are exactly alike. Observation #5: Much of this variation is heritable. Inference #2: Survival in the struggle for existence is not random, but depends in part on the hereditary constitution of the individuals. Those individuals whose inherited characteristics best fit them to their environment are likely to leave more offspring than less fit individuals. Inference #3: This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population, with favorable characteristics accumulating over the generations. Island with many many insects

Darwin’s main ideas : 6 steps KNOW THIS INSIDE OUT!
1) All populations will try to increase in time; Resources are limited (intraspecific competition results). Struggle for existence follows. 2) There is an unequal ability of individuals to survive and reproduce - this is ‘variation’ based on genes/epigenome. 3) Natural Selection acts on this inherent VARIATION allowing the “best fit” to survive and pass on their genes. 4) The product of natural selection is the adaptation of populations of organisms to their environment. (= edits the variation to exclude ‘unfit’ individuals) 5) This adaptation is inheritable - so the next generation continues to express that ‘best fit’ trait and then in time….. 6) New species formed as sufficient adaptations accumulated in time such that they could no longer mate with the ancestral species Descent with modification - all present day organisms have descended from ancestors by the accumulation of adaptations through natural selection

Short period of time needed for Artificial Selection
Artificial Selection: The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits. Short period of time needed for Artificial Selection Darwin’s views on the role of environmental factors in the screening of heritable variation was heavily influenced by artificial selection. Humans have modified a variety of domesticated plants and animals over many generations by selecting individuals with the desired traits as breeding stock If artificial selection can achieve such major changes in a relatively short time, then natural selection should be capable of major modifications of species over hundreds or thousands of generations. Darwin envisioned the diversity of life as evolving by a gradual accumulation of minute changes through the actions of natural selection operating over vast spans of time.

Natural selection traits that improve survival or reproduction will accumulate in the population adaptive change

Fig. 22.9 Apply the concept of Natural Selection and predict what will happen to these beetle species in this new environment

For example, these related species of insects called mantids have diverse shapes and colors that evolved in different environments. Fig

What common EVOLUTION misconceptions do students have?
Organisms “choose” to evolve better traits (Lamarckian) Natural Selection causes variation Natural selection acts on ALL variation Natural Selection acts on individuals and therefore individuals evolve While natural selection involves interactions between individual organisms and their environment, it is not individuals, but populations that evolve. Populations are defined as a group of interbreeding individuals of a single species that share a common geographic area. Natural selection can only amplify or diminish heritable variations, not variations that an individual acquires during its life, even if these variations are adaptive. Also, natural selection is situational. Environmental factors vary in space and time. Therefore, adaptations for one set of environmental conditions may be useless or even detrimental under other circumstances. In general, natural selection operates not to create variation, but to edit existing variation. For example, resistant insects are favored and non-resistant individuals are not when insecticides are applied. Natural selection favors those characteristics in a variable population that fit the current, local environment.

What is EVOLUTION? Evolution is measured as the change in relative proportions of heritable variation in a population over a succession of generations.

1) Natural selection in action: the evolution of insecticide-resistance occurs in nature - individuals with the best fit genes that can resist the insecticide will survive…. The evolution of resistance to insecticides in hundreds of insect species is a classic example of natural selection in action. Insecticides are poisons that kill insects that are pests in crops, swamps, backyards, and homes. The results of application of new insecticide are typically encouraging, killing 99% of the insects. However, the effectiveness of the insecticide becomes less effective in subsequent applications. The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the percentage of insecticide-resistant individuals increases. Fig

2) Natural selection in action: the evolution of drug-resistant HIV - 3TC drug resistance developed - 100% HIV become resistant in 3-4 weeks! While researchers have developed many drugs to combat the human immunodeficiency virus (HIV), drug-resistant strains evolve rapidly in the HIV population infecting each patient. Natural selection favors those characteristics in a variable population that fit the current, local environment. The evolution of drug resistance or pesticide resistance differ only in speed, not in basic mechanism, from other cases of natural selection. For patients treated with the drug 3TC, which interferes with genome replication in HIV, 3TC-resistant strains become 100% of the population of HIV in just a few weeks.

3) Natural selection in action: the peppered moth - originally light colored on light bark; Industrialized England - bark became covered in soot; so bark became dark; moth evolved to become dark Figure 3.3. Left: The peppered moth, Biston betularia, and its melanic form, carbonaria, at rest on a soot-covered oak trunk near the industrial city of Birmingham, England. The carbonaria form is much less conspicuous than the typical peppered form, which is very conspicuous. Right: The same forms resting on a lichened tree trunk in unpolluted countryside. The typical form is much less conspicuous than the melanic. Reprinted, with permission, from Kettlewell, H. B. D., Department of Zoology, South Parks Road, Oxford, OX1 3PS. Arrows point to the moths.Professor H. B. D. Kettlewell demonstrated that the basis of the [182] change in frequency of the gene controlling the moth's pigmentation was their need for protective coloration against their natural predators such as birds (6). In rural areas he noticed that dark pigmented moths resting on tree trunks with light colored lichens (a fungus and alga growing together) were conspicuous to birds while the light varieties were camouflaged. In the industrialized areas lichens were scarce, having been killed by pollutants. In these regions the dark varieties of the peppered moth matched the color of the polluted tree trunks, making it difficult for predators to detect them. This phenomenon was very striking in the industrialized city of Birmingham. In contrast, the presence of any light colored moth resting on a tree trunk in the Birmingham area was obvious (Figure 3.3). Kettlewell theorized that birds selectively pick out the conspicuous varieties in both the polluted and nonpolluted environments, thereby contributing to the change in the frequency of the genes, controlling pigmentation. In order to test this hypothesis, he raised thousands of light- and dark-pigmented peppered moths, marked each with a dot of [183] paint, and released them into the polluted (industrialized) and nonpolluted (nonindustrialized) areas of England. He then set out to recapture these moths. In the nonindustrialized areas, he managed to recapture 14.6% of the light varieties but only 4.7% of the dark varieties. In the industrialized areas, he was able to capture only 13% of the light varieties; however, 27.5% of the dark varieties were recovered. In another series of experiments Kettlewell was able to photograph birds preying on moths that he placed on tree trunks. He demonstrated unequivocally that birds eat more light varieties in the polluted areas and more dark varieties in the nonpolluted areas. Direct experimental tests, as well as the discovery of dark varieties in regions far away from the industrialized areas, suggested that the dark varieties did not arise from mutations induced by particulate matter, such as heavy metals, emitted from industrial plants. Industrialization apparently changed the environment, resulting in natural selection favoring survival of dark varieties and loss of light varieties. Thus the natural selective force of predation in a changing environment caused by industrialization was responsible for microevolution in moths.

Anatomical -human hand, cat limb, whale flipper, bat wing - they all have the same basic bone structure and design; So they have ALL evolved from a common ancestor with a similar ‘limb design’. Related to this: Genetic Homologies: Homeoboxes are a common set of developmental genes seen in species as diverse as the fly to mammals! B) HOMOLOGIES – Similarities in characteristics resulting from common ancestry is known as homology. 1) Homologous Structures: Same skeletal elements, but different functions Same ancestor- tetrapod forelimb. In addition to those cases in which we can observe evolution directly, we see evidence of evolution by natural selection in the much grander changes in biological diversity documented by the fossil record. Evidence that the diversity of life is a produce of evolution pervades every research field of biology. As biology progresses, new discoveries, including the revelations of molecular biology, continue to validate the Darwinian view of life. In descent with modification, new species descend from ancestral species by the accumulation of modifications as populations adapt to new environments. The novel features that characterize a new species are not entirely new, but are altered versions of ancestral features. Descent with modification is indeed evident in anatomical similarities between species grouped in the same taxonomic category. For example, the forelimbs of human, cats, whales, and bats share the They are homologous structures. HOMOLOGOUS STRUCTURES

WASHINGTON - There is something fishy going on in your arms and legs — and it’s a good thing. With the discovery of the world’s oldest known arm bone, scientists conclude that many of the physical features we associate with life on land, including the bone structures and muscles necessary for walking and doing pushups, have their evolutionary roots in fish. advertisement Analysis of this newly discovered fossil arm bone, in addition to other recent finds, overturns the long-held idea that limbs evolved specifically for life on land. A full description of the 365-million-year-old arm bone from Pennsylvania appears in Friday's issue of the journal Science, published by AAAS, the nonprofit science society. “We are trying to untangle a very complicated and important evolutionary event — the shift from water to land,” said study author Neil Shubin from the University of Chicago. The upper arm bone, or humerus, that was discovered by the authors belongs to a new variety of four-limbed carnivore that lived long before the dinosaurs. These carnivores were some of the first tetrapods, members of a group that includes all creatures with limbs, including reptiles, amphibians, birds and mammals. “This is the earliest known arm bone. It’s a mosaic of fish features, tetrapod features and unique features,” Shubin explained. Art by Kalliopi MonoyiosThe cover illustration for the journal Science reconstructs the posture of an extinct animal from isolated bones. The humerus indicates that the creature could support the front end of its body in a low, wide stance. This posture reflects an intermediate stage in the evolution of amphibian limbs from fish fins.Shubin and his colleagues compared the arm fossil to the bones of both ancient and modern fish, and arrived at a new understanding of the beginnings of limb evolution. “The hybrid creature used its powerful limbs to do some of the world’s first pushups,” Shubin said. The new fossil, like a photo taken with high-speed film, catches limb evolution in action. It helps clarify when, where and how animals first learned to walk. The fossil evidence suggests that the first limbed animals tried all kinds of walking strategies. Without Devonian photo albums full of fish trying to put weight on their pectoral fins, paleontologists must rely on the fossil record to understand how new fossil finds fit into the story of life. “This humerus is quite unique,” said Jennifer Clack, the author of an accompanying article that provides some background information on this fossil. Clack said the fossil’s “bizarre shape” does not fit the patterns of other early tetrapods.She believes that there were a variety of limb shapes, sizes and strengths among early tetrapods experimenting with adaptations for life on land. Plants help limbs grow Before vertebrates took their first steps — in or out of the water — plants with stems, roots and leaves colonized shallow rivers and changed the nature of many aquatic environments and nearby shores. Plants grew thick in streams and rivers, their roots stabilized ecosystems, and their decomposing biomass generated organic muck. Plant-clogged waterways made weight-bearing fins, and eventually limbs, useful for getting around, Shubin suggests. Science MysteriesFor a limited time, MSNBC.com users have free access to the original research from the journal Science:• "The Early Evolution of the Tetrapod Humerus"• "From Fins to Fingers"• Sign up for Science • News from EurekAlert• Science Mysteries• More Mysteries of the UniverseThe fossil also shows that tetrapod shoulders changed the direction they face in order to adapt to life in a plant-tangled, aquatic environment. With shoulders facing sideways, the tetrapod’s arms projected out from its trunk at a right angle, similar to the limb arrangement of a crocodile. This shoulder and arm orientation would have made the front limbs more useful as weight-bearing limbs than paddles. In addition to altering land and water habitats in ways that probably encouraged limb development, the rise of more advanced plants also changed the oxygen balance. Plants contributed to dropping oxygen levels in water and rising oxygen concentrations in the air. This oxygen scenario, combined with the newfound ability to stick their heads out of the water, may have encouraged the evolution of lungs in fish. Streams full of toothy carnivorous fish — some with joints in their skulls to increase the size of their bites — may have also inspired tetrapods to take their head-propping, muck-stomping skills to higher ground. Fish are family, too The evolution of limbs from fins, one of the key transitions in the history of life, took place gradually and largely separate from the water-to-land transition. After comparing this fossil arm bone to those from other tetrapods and closely related fish, the scientists conclude that many of the limb and muscle developments needed for walking on land developed before fish and limbed animals split. For example, some modern fish can hold the same spot or lift up their trunks in moving water, thanks to bone and muscle changes that occurred before fish and limbed animals went their separate ways. Honk if you love fossils The scientists discovered the fossil in 1993, but they only recently exposed the entire bone from its red sandstone encasement and realized the significance of the specimen. The discovery site, Red Hill, holds a series of ancient stream deposits that preserve the birth, life and death of tropical to subtropical ecosystems from the Late Devonian period of Earth’s history. Red Hill includes a wall of rock along the shoulder of a highway in Pennsylvania’s Catskill Mountains. If the scientists discovered this arm bone along a shoulder of a highway, perhaps the secrets to tetrapod ankles and wrists are resting underneath the foot of a nearby mountain. © 2005 American Association for the Advancement of Science

Basic genetic Code (all organisms) and….
Molecular Homologies Basic genetic Code (all organisms) and…. The concept of homology also applies at the molecular level (molecular homology) and allows links between organisms that have no macroscopic anatomy in common (e.g., plants and animals). For example, all species of life have the same basic genetic machinery of RNA and DNA and the genetic code is essentially universal. Evidently, the language of the genetic code has been passed along through all the branches of the tree of live eve since the code’s inception in an early life-form. If hierarchies of homology reflect evolutionary history, then we should expect to find similar patterns whether we are comparing molecules or bones or any other characteristics. In practice, the new tools of molecular biology have generally corroborated rather than contradicted evolutionary trees based on comparative anatomy and other methods. Evolutionary relationships among species are documented in their DNA and proteins - in their genes and gene products. If two species have libraries of genes and proteins with sequences that match closely, the sequences have probably been copied from a common ancestor. For example, the number of amino acid differences in human hemoglobin when compared to other vertebrates show the same patterns of evolutionary relationships that researchers find based on other proteins or other types of data.

Embryological Homologies - embryos look alike in related species!
All vertebrate embryos have ‘pharyngeal pouches’ in their throat. These in the Adult become gills of fish or the Eustacean tubes in other vertebrates! Sometimes, homologies that are not obvious in adult organisms become evident when we look at embryonic development. For example, all vertebrate embryos have structures called pharyngeal pouches in their throat at some stage in their development. These embryonic structures develop into very different, but still homologous, adult structures, such as the gills of fish or the Eustacean tubes that connect the middle ear with the throat in mammals.

Ontogeny recapitulates phylogeny - what ever does this mean?

Ontogeny recapitulates phylogeny - the phylum origin is ‘recapped’ in the embryo

Homologies mirror the tree of life.
Some homologies, such as the genetic code, are shared by all life because they date to the deep ancestral past. Other homologies that evolved more recently are shared only by smaller branches of the tree of life. For example, only tetrapods (amphibians, reptiles, birds, and mammals) share the same five-digit limb structure. This hierarchical pattern of homology is exactly what we would expect if life evolved and diversified from a common ancestor, but not what we would see if each species arose separately.

Some Alleged Vestigial Organs in Man
Vestigial organs, structures that are not used, but which had important functions in ancestors - still retained in descendents, so evolution ‘happened’. Some Alleged Vestigial Organs in Man Tonsils Adenoids Coccyx (tail bone) Nictitating membrane of eye Thymus Appendix Little toe Wisdom teeth Nipples on males Parathyroid Nodes on ears "Darwin's points" Ear muscles for wiggling Pineal gland Body hair For example, the skeletons of some snakes and of fossil whales retain vestiges of the pelvis and leg bones of walking ancestors. Comparative anatomy confirms that evolution is a remodeling process via alteration of existing structures, rather than uniquely engineered for their existing function. Historical constraints on this retrofitting are evident in anatomical imperfections. For example, the back and knee problems of bipedal humans are an unsurprising outcome of adapting structures originally evolved to support four-legged mammals. The Appendix This is the classic vestigial organ of evolutionists. It sometimes becomes swollen, and it was noticed that people can survive if it is removed, and was therefore labeled as useless. We now know that it plays a role in antibody production and protects our intestines from infection. The appendix lessens the chances of a person getting leukemia, Hodgkin’s disease, cancer of the colon and cancer of the ovaries. The Tonsils These organs in the throat protect us from infections. The Coccyx These are vertebrae found at the bottom of the spine. It was once thought to be useless, a remnant of a tail from our evolutionary past. It has since been discovered that some important muscles attach to it, namely the levator ani and coccygeus. Without it, our pelvic organs would just fall down, we wouldn’t be able to walk, sit upright or have bowel movement. The Thymus This "worthless" organ has been discovered to play an important role in the development of the immune system. In this gland lymphocyte and antibody production takes place. Without it, our immune system would not develop properly. Pineal Gland Produces vital hormones, such as melatonin. It also affects the functions of other endocrine organs. Thyroid Gland Produces the hormone thyroxin that controls metabolism and growth. It’s deficiency at birth causes cretinism. Pituitary Gland It is the master endocrine gland which controls and stimulates almost all the other endocrine glands in the body. It ensures proper growth of the skeletal system and control the water balance of the body. It’s malfunctioning causes gigantism, Cushing’s syndrome, dwarfism, diabetes insipidus, acromegaly, etc. Vestigial organs- organs or parts of organs that are nonfunctional and degenerate- wingless birds with vestigial wing bones, whales and pythons with vestigial hind leg bones; blind cave-dwelling animals with vestigial eyes a. Occasional vestigial organ is to be expected as a species evolves and adapts to different modes of life b. When an organ loses its function, there is no selective advantage to possess it but there is no selective pressure to get rid of it

Vestigial organs – spurs in snakes, hind leg bones in whales.
For example, the skeletons of some snakes and of fossil whales retain vestiges of the pelvis and leg bones of walking ancestors. Comparative anatomy confirms that evolution is a remodeling process via alteration of existing structures, rather than uniquely engineered for their existing function. Historical constraints on this retrofitting are evident in anatomical imperfections. For example, the back and knee problems of bipedal humans are an unsurprising outcome of adapting structures originally evolved to support four-legged mammals. The Appendix This is the classic vestigial organ of evolutionists. It sometimes becomes swollen, and it was noticed that people can survive if it is removed, and was therefore labeled as useless. We now know that it plays a role in antibody production and protects our intestines from infection. The appendix lessens the chances of a person getting leukemia, Hodgkin’s disease, cancer of the colon and cancer of the ovaries. The Tonsils These organs in the throat protect us from infections. The Coccyx These are vertebrae found at the bottom of the spine. It was once thought to be useless, a remnant of a tail from our evolutionary past. It has since been discovered that some important muscles attach to it, namely the levator ani and coccygeus. Without it, our pelvic organs would just fall down, we wouldn’t be able to walk, sit upright or have bowel movement. The Thymus This "worthless" organ has been discovered to play an important role in the development of the immune system. In this gland lymphocyte and antibody production takes place. Without it, our immune system would not develop properly. Pineal Gland Produces vital hormones, such as melatonin. It also affects the functions of other endocrine organs. Thyroid Gland Produces the hormone thyroxin that controls metabolism and growth. It’s deficiency at birth causes cretinism. Pituitary Gland It is the master endocrine gland which controls and stimulates almost all the other endocrine glands in the body. It ensures proper growth of the skeletal system and control the water balance of the body. It’s malfunctioning causes gigantism, Cushing’s syndrome, dwarfism, diabetes insipidus, acromegaly, etc. Vestigial organs- organs or parts of organs that are nonfunctional and degenerate- wingless birds with vestigial wing bones, whales and pythons with vestigial hind leg bones; blind cave-dwelling animals with vestigial eyes a. Occasional vestigial organ is to be expected as a species evolves and adapts to different modes of life b. When an organ loses its function, there is no selective advantage to possess it but there is no selective pressure to get rid of it

Fossil Evidence- Capture evolutionary transitions - all species not present at the same time
The succession of fossil forms is compatible with what is known from other types of evidence about the major branches of descent in the tree of life. For example, fossil fishes predate all other vertebrates, with amphibians next, followed by reptiles, then mammals and birds. This is consistent with the history of vertebrate descent as revealed by many other types of evidence. In contrast, the idea that all species were individually created at about the same time predicts that all vertebrate classes would make their first appearance in the fossil record in rocks of the same age. This is not what paleontologists actually observe. The Darwinian view of life also predicts that evolutionary transitions should leave signs in the fossil record. For example, a series of fossils documents the changes in skull shape and size that occurred as mammals evolved from reptiles. Recent discoveries include fossilized whales that link these aquatic mammals to their terrestrial ancestors.

Biogeography- The geographical distribution of species .
Species tend to be more closely related to other species from the same area than to other species with the same way of life, but living in different areas For example, even though some marsupial mammals (those that complete their development in an external pouch) of Australia have look-alikes among the eutherian mammals (those that complete their development in the uterus) that live on other continents, all the marsupial mammals are still more closely related to each other than they are to any eutherian mammal. For example, while the sugar glider and flying squirrel have adapted to the same mode of life, they are not closely related. Instead, the sugar glider from Australia is more closely related to other marsupial mammals from Australia than to the flying squirrel, a placental mammal from North America. The resemblance between them is an example of convergent evolution. CONVERGENT EVOLUTION

Biogeography- extension- Island species related to mainland species
Island and island archipelagos have provided strong evidence of evolution. Often islands have many species of plants and animals that are found nowhere else in the world, called endemics. As Darwin observed when he reassessed his collections from the Beagle’s voyage, these endemic species are typically related more closely to species living on the nearest mainland (despite different environments) than those from other island groups. In island chains, or archipelagos, individual islands may have different, but related species as the first mainland invaders reached one island and then evolved into several new species as they colonized other islands in the archipelago. Several well-investigated examples of this phenomenon include the diversification of finches on the Galapagos Islands and fruit flies (Drosophila) on the Hawaiian Archipelago All of the 500 or so endemic species of Drosophila in the Hawaiian archipelago descended from a common ancestor that reached Kauai over 5 million years ago.

DESCENT WITH MODIFICATION – CORE OF DARWINIAN THEORY
Descent with modification - the conclusion. Descendents accumulated diverse modifications or adaptations that fit them to specific ways of life and habitats - resulting in formation of new species. All present day organisms are related through descent from unknown ancestors in the past. Viewed from the perspective of descent with modification, the history of life is like a tree with multiple branches from a common trunk. Closely related species, the twigs of the tree, shared the same line of descent until their recent divergence from a common ancestor. By the early 1840’s Darwin had developed the major features of his theory of natural selection as the mechanism for evolution. In 1844, he wrote a long essay on the origin of species and natural selection, but he was reluctant to publish his theory and continued to compile evidence to support his theory. In June 1858, Alfred Wallace, a young naturalist working in the East Indies, sent Darwin a manuscript containing a theory of natural selection essentially to identical to Darwin’s. Later that year, both Wallace’s paper and extracts of Darwin’s essay were presented to the Linnaean Society of London. Darwin quickly finished The Origin of Species and published it the next year. While both Darwin and Wallace developed similar ideas independently, the essence of evolution by natural selection is attributed to Darwin because he developed and supported the theory of natural selection so much more extensively and earlier. DESCENT WITH MODIFICATION – CORE OF DARWINIAN THEORY

More descent: Organisms are related through descent from
common ancestors So….. All organisms in a CLASS have a common ancestor at the level of the PHYLUM and so on… The other major point that Darwin pioneered is a unique mechanism of evolution - the theory of natural selection. Ernst Mayr, an evolutionary biologist, has dissected the logic of Darwin’s theory into three inferences based on five observations. These observations include tremendous fecundity, stable populations sizes, limited environmental resources, variation among individuals, and heritability of some of this variation.

This evolutionary tree of the elephant family is based on evidence from fossils.
Fig. 22.7

As Darwin said, “There is grandeur in this view of life.”
Fig

Darwin Awards? http://www.darwinawards.com/
Named in honor of Charles Darwin, the father of evolution, the Darwin Awards commemorate those who improve our gene pool by removing themselves from it.

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