Module 6 Quiz
Describe and give examples of the following evidences for evolution a. fossil record ii. lobe-finned fish
-Tetrapods are thought to have evolved from lobe-finned fish -The first amphibians likely evolved from lobe finned fish -Lobe finned fish had several adaptations that allowed them to transition to life on land -Tiktaalik Roseae is a type of lobe finned fish In 2004, a team of paleontologists discovered fossilized remains of Tiktaalik roseae, nicknamed the "fishapod" because it is the transitional form between fish and four-legged animals, the tetrapods. Tiktaalik fossils are estimated to be 375 million years old and are from a time when the transition from fish to tetrapods is likely to have occurred. As expected of an intermediate fossil, Tiktaalik has a mix of fishlike and tetrapod-like features that illustrate the steps in the evolution of tetrapods from a fishlike ancestor. For example, Tiktaalik has a very fishlike set of gills and fins, with the exception of the pectoral (front) fins, which have the beginnings of wrist bones (or legs) similar to those of a tetrapod. Unlike a fish, however, Tiktaalik has a flat head, a flexible neck, eyes on the top of its head like a crocodile, and interlocking ribs that suggest it had lungs. These transitional features suggest that it had the ability to push itself along the bottom of shallow rivers and see above the surface of the water—features that would come in handy in its river habitat. · Figure 14.13 Evolution of tetrapods. Tiktaalik roseae has a mix of fishlike and tetrapod-like features. Fossils such as that of Tiktaalik provide evidence that the evolution of new groups involves the modification of preexisting features in older groups. The evolutionary transition from one form to another, such as from a fish to a tetrapod, can be gradual, with intermediate forms having a set of adapted, fully functional features.
Four steps in the theory of natural selection
1) heritable variations 2) overreproduction of offspring 3) differential reproduction (competition) 4) frequency of adaptation over time increases 1) The members of a population have heritable variations. 2) The population produces more offspring than the resources of an environment can support. 3) The individuals that have favorable traits survive and reproduce to a greater extent than those that lack these traits. 4) Over time, the proportion of a favorable trait increases in the population, and the population becomes adapted to the environment.
Cuvier
A noted zoologist of the early nineteenth century, Georges Cuvier, founded the science of paleontology, the study of fossils. Cuvier was faced with a problem. He believed in the fixity of species (the idea that species do not change over time), yet Earth's strata clearly showed a succession of different life-forms over time. To explain these observations, he hypothesized that a local catastrophe had caused a mass extinction whenever a new stratum of that region showed a new mix of fossils. After each catastrophe, the region was repopulated by species from surrounding areas, which accounted for the appearance of new fossils in the new stratum. The result of all these catastrophes was change appearing over time. Some of Cuvier's followers, who came to be called catastrophists, even suggested that worldwide catastrophes had occurred and that, after each of these events, new sets of species had been created.
State Wallace's contributions to the theory of natural selection
After the HMS Beagle returned to England in 1836, Darwin waited more than 20 years to publish his book On the Origin of Species. During the intervening years, he used the scientific process to support his hypothesis that today's diverse life-forms arose by descent form a common ancestor and that natural selection is the mechanism by which species can change and new species can arise. Darwin was prompted to publish his book after reading a similar hypothesis formulated by Alfred Russel Wallace. · Wallace was an English naturalist who, like Darwin, was a collector at home and abroad. He went on collecting trips, each of which lasted several years, to the Amazon and the Malay Archipelago. After studying the animals of every island within the Malay Archipelago, he divided the islands into a western group, with organisms like those found in Asia, and an eastern group, with organisms like those of Australia. The sharp line dividing these two island groups within the archipelago is now known as Wallace's Line. A narrow but deep strait occurs along Wallace's Line. At times during the past 50 million years, this strait persisted even when sea levels were low and land bridges appeared between the other islands. Therefore, the strait served as a permanent barrier to the dispersal of organisms between the two groups of islands. · While traveling, Wallace wrote an essay called "On the Law Which Has Regulated the Introduction of New Species." In this essay, he said that "every species has come into existence coincident both in time and space with a preexisting closely allied species." A year later, after reading Malthus's treatise on human population increase, Wallace conceived the idea of "survival of the fittest." He quickly completed an essay proposing natural selection as an agent for evolutionary change and sent it to Darwin for comment. Darwin was stunned. Here was the hypothesis he had formulated but had never dared to publish. He told his friend and colleague Charles Lyell that Wallace's ideas were so similar to his own that even Wallace's "terms now stand as heads of my chapters." · Darwin suggested that Wallace's paper be published immediately, even though Darwin himself as yet had nothing in print. However, Lyell and others who knew of Darwin's detailed work substantiating the process of natural selection suggested that a joint paper be read to the renowned Linnean Society. On July 1, 1858, Darwin presented an abstract of On the Origin of Species, which was published in 1859. The title of Wallace's section was "On the Tendency of Varieties to Depart Indefinitely from the Original Type." This professional presentation served as the announcement to the world that species share a common descent and have diverged through natural selection.
Describe and give examples of the following evidences for evolution d. molecular evidence ii. developmental genes
Also of interest, evolutionary developmental biologists have found that many developmental genes, called Hox genes, are shared in animals ranging from worms to humans. It appears that life's vast diversity has come about through only slight differences in the same genes. The results have been widely divergent body plans. For example, a similar gene in arthropods and vertebrates determines the back-to-front axis. However, although the base sequences are similar, the genes have opposite effects. In arthropods, such as fruit flies and crayfish, the nerve cord is toward the front; in vertebrates, such as chickens and humans, the nerve cord is toward the back.
Describe and give examples of the following evidences for evolution b. biogeographical evidence i. marsupial mammals in Australia
Also, long ago, South America, Antarctica, and Australia were connected. Marsupials (pouched mammals) and placental mammals arose at this time, but today marsupials are plentiful only in Australia, and placental mammals are plentiful in South America. Why are marsupials plentiful only in Australia? After marsupials arose, Australia separated and drifted away, and marsupials were free to evolve into many different forms because they had no competition from placental mammals. In the Americas, the placental mammals competed successfully against the marsupials, and the opossum is the only marsupial in the Americas. In some cases, marsupial and placental mammals physically resemble one another—two such cases are the marsupial wombat and the marmot and the marsupial Tasmanian wolf and the wolf. This supports the hypothesis that evolution is influenced by the environment and by the mix of plants and animals on a particular continent—by biogeography, not by design. Figure 14.15 Marsupials of Australia. Marsupials in Australia and placental mammals in the rest of the world often have similar characteristics, even though the marsupials all evolved from a common ancestor that entered Australia some 60 MYA.
Describe and give examples of the following evidences for evolution c. anatomical evidence ii. analogous structures
Analogous structures serve the same function but are not constructed similarly, and therefore could not have a common ancestry. The wings of birds and insects are analogous structures.
Describe and give examples of the following evidences for evolution c. anatomical evidence i. homologous structures
Anatomically similar structures explainable by inheritance from a common ancestor are called homologous structures. Vertebrate forelimbs are used for flight (birds and bats), orientation during swimming (whales and seals), running (horses), climbing (arboreal lizards), and swinging from tree branches (monkeys). However, all vertebrate forelimbs contain the same sets of bones organized in similar ways, despite their dissimilar functions. The most plausible explanation for this unit of anatomy is that the basic forelimb plan belonged to a common ancestor, and then the plan became modified in the succeeding groups as each continued along its own evolutionary pathway. Figure 14.16 Significance of structural similarities. Although the specific details of vertebrate forelimbs are different, the same basic bone structure and position are present (color-coded here). This unit of anatomy is evidence of a common ancestor.
Explain how Darwin's study of fossils and biogeography contributed to the development of the theory of natural selection e. rheas (greater vs. lesser)
As Darwin sailed southward along the eastern coast of South America, he saw how similar species replaced one another. For example, the greater rhea (an ostrichlike bird) found in the north was replaced by the lesser rhea in the south. Therefore, Darwin reasoned that related species can be modified according to environmental differences caused by change in latitude. When he reached the Galápagos Islands, he found further evidence of this. The Galápagos Islands are a small group of volcanic islands located 965 km (600 miles) off the western coast of South America. These islands are too far from the mainland for most terrestrial animals and plants to colonize, yet life was present. The types of plants and animals found there were slightly different from species Darwin had observed on the mainland; even more important, they also varied from island to island according to each unique environment. Where did the species inhabiting these islands come from, and what caused the islands to have different species?
Explain how Darwin's study of fossils and biogeography contributed to the development of the theory of natural selection a. Lyell
Charles Lyell wrote a book called the Principles of Geology. Darwin took this book with him on the Beagle voyage. Lyell proposed the theory of uniformitarianism.
Explain how Darwin's study of fossils and biogeography contributed to the development of the theory of natural selection d. convergent evolution (hares)
Darwin could not help but compare the animals of South America with those he observed in England. For example, instead of rabbits, he found Patagonian hares in the grasslands of South America. The Patagonian hare is a rodent that has long legs and ears and the face of a guinea pig. While the Patagonian hare resembles a rabbit, or even a small deer, it is actually more closely related to the rodents. Its correct name is the Patagonian mara (Dolichotis patagonum). Darwin wondered whether the similarities between these two animals were not due to a common ancestor, but rather arose because the two types of animals were adapted to the same type of environment. Scientists call this process convergent evolution, and it explains how distantly related species may converge on the same overall body form because they live in similar habitats and have similar behaviors.
Explain how Darwin's study of fossils and biogeography contributed to the development of the theory of natural selection b. uniformitarianism
Darwin took Charles Lyell's book Principles of Geology with him on the Beagle voyage. Lyell proposed the theory of uniformitarianism, which states that the Earth is subject to slow but continuous cycles of erosion and uplift. Weathering causes erosion; thereafter, dirt and rock debris are washed into rivers and transported to oceans. When these loose sediments are deposited, strata result. Then the strata, which often contain fossils, are uplifted over long periods of time from below sea level to form land. Given enough time, slow natural processes can account for extreme geological changes. Lyell went on to propose the theory of uniformitarianism, which stated that these slow changes occurred at a uniform rate. Even though uniformitarianism has been rejected, modern geology certainly substantiates a hypothesis of slow and continual geological change. Darwin, too, was convinced that Earth's massive geological changes are the result of slow processes and therefore Earth must be very old.
Darwin's Conclusions
Darwin's Conclusions Darwin's conclusions that organisms are related through common descent and that adaptation to various environments results in diversity were based on several types of data, including his study of geology, fossils, and biogeography. Biogeography is the study of the distribution of life-forms on Earth.
Facts about natural selection
Due to the fact that natural selection utilizes only variations that happen to be provided by genetic changes (such as mutations), it lacks any directedness or anticipation of future needs. Natural selection is an ongoing process, because the environment of living organisms is constantly changing. Extinction, or the complete loss of a species, can occur when previous adaptations are no longer suitable to a changed environment.
Explain how Darwin's study of fossils and biogeography contributed to the development of the theory of natural selection h. tortoise diversity
Each of the Galápagos Islands also seemed to have its own type of tortoise, and Darwin began to wonder if this could be correlated with a difference in vegetation among the islands. Long-necked tortoises seemed to inhabit only dry areas, where food was scarce, and most likely the longer neck was helpful in reaching tall-growing cactuses. In moist regions with relatively abundant ground foliage, short-necked tortoises were found. Had an ancestral tortoise from the mainland of South America given rise to these different types, each adapted to a different environment? An adaptation is any characteristic that makes an organism more suited to its environment. It often takes many generations for an adaptation to become established in a population.
Describe and give examples of the following evidences for evolution a. fossil record i. Archaeopteryx
Fossil Evidence · The fossils trapped in rock strata are the fossil record that tell us about the history of life. One of the most striking patterns in the fossil record is a succession of life-forms from the simple to the more complex. Occasionally, this pattern is reversed, showing that evolution is not unidirectional. Particularly interesting are the fossils that serve as transitional links between groups. Even in Darwin's day, scientists knew of the Archaeopteryx fossils, which show that birds have reptilian features, including jaws with teeth and long, jointed tails. Archaeopteryx also had feathers and wings. (Archaeopteryx had a feather-covered, reptilian-type tail; feathers; teeth, claws; tail with vertebrae).
Summarize the contributions of Cuvier and Lamarck to the study of evolutionary change. c. fixity of species
Georges Cuvier believed in the fixity of species, the idea that species do not change over time, yet Earth's strata clearly showed a succession of different life-forms over time. To explain these observations, he hypothesized that a local catastrophe had caused a mass extinction whenever a new stratum of that region showed a new mix of fossils. After each catastrophe, the region was repopulated by species from surrounding areas, which accounted for the appearance of new fossils in the new stratum.
Describe and give examples of the following evidences for evolution a. fossil record v. snake with hip bones and hind limbs
In 2006, a snake fossil dated to 90 MYA was discovered that showed hip bones and hindlimbs—a trait absent in all living snakes. Some snakes, such as pythons, have vestigial hindlimbs, but these snakes lack the hip bones present in this fossil. Since all lizards have hip bones and most have limbs, this fossil is considered a transitional link between lizards and snakes.
Explain how Darwin's study of fossils and biogeography contributed to the development of the theory of natural selection c. marine shell locations
In Chile, Darwin witnessed the effects of an earthquake that caused the land to rise several feet and left marine shells inland, well above sea level. When Darwin also found marine shells high in the cliffs of the impressive Andes Mountains, he became even more convinced that Earth is subject to slow geological changes.
Lamarck
In contrast to Cuvier, Jean-Baptiste de Lamarck, another biologist, hypothesized that evolution occurs and that adaptation to the environment is the cause of diversity. Therefore, after studying the succession of life-forms in strata, Lamarck concluded that more complex organisms are descended from less complex organisms. To explain the process of adaptation to the environment, Lamarck proposed the idea of inheritance of acquired characteristics, in which the use or disuse of a structure can bring about inherited change. One example Lamarck gave—and the one for which he is most famous—is that the long neck of giraffes developed over time because giraffes stretched their necks to reach food high in trees and then passed on a long neck to their offspring. However, the inheritance of acquired characteristics is not the primary mechanism that drives the change in species over time. If this were the case, then the knowledge you acquire over your lifetime would be passed on to your offspring. Still, in recent years scientists have unveiled some conditions under which acquired characteristics may be passed on to the next generation. For example, in epigenetic inheritance, changes in the expression of a gene that are not associated with mutations or other nucleotide changes may be passed from one generation to the next. These cases are relatively rare and usually relate only to the inheritance of specific genes.
Explain how Darwin's study of fossils and biogeography contributed to the development of the theory of natural selection f. speciation
Later, Darwin speculated as to whether all the different species of finches he had seen could have descended from a mainland finch. In other words, he wondered if a mainland finch was the common ancestor of all the types on the Galápagos Islands. In Darwin's time, the concept of speciation, the formation of a new species, was not well understood. To Darwin, it was possible that the islands allowed isolated populations of birds to evolve independently and that the present-day species had resulted from accumulated changes occurring within each of these isolated populations over time.
Explain the steps in the theory of natural selection. d. frequency of adaptation over time increases
Over time, the proportion of a favorable trait increases in the population, and the population becomes adapted to the environment.
Describe and give examples of the following evidences for evolution a. fossil record iv. evolution of whales
The fossil record also provides important insights into the evolution of whales from land-living, hoofed ancestors. The fossilized whale Ambulocetus may have ben amphibious, walking on land and swimming in the sea. Rodhocetus swam with an up-and-down tail motion, as modern whales do; its reduced hindlimbs could not have helped in swimming. Hypothetical mesonychid skeletonàAmbulocetus natans. Probably walked on land (as do modern sea lions) and swam by flexing its backbone and paddling with its hindlimbs (as do modern otters). à The reduced hindlimbs of Rodhocetus kasrani could not have aided it in walking or swimming. Rodhocetus swam with an up-and-down motion, as do modern whales. à modern toothed whales.
Describe and give examples of the following evidences for evolution c. anatomical evidence iii. embryo similarities
The homology shared by vertebrates extends to their embryological development. At some point during development, all vertebrates have a postanal tail and exhibit paired pharyngeal pouches supported by cartilaginous bars. In fishes and amphibian larvae, these pouches develop into functioning gills. In humans, the first pair of pouches become the cavity of the middle ear and the auditory tube. The second pair becomes the tonsils; the third and fourth pairs become the thymus and parathyroid glands. Why should pharyngeal pouches, which have lost their original function, develop and then become modified in terrestrial vertebrates? The most likely explanation is that new structures (or structures with unique functions) originate by "modifying" the preexisting structures of an organism's ancestors. Figure 14.17 Significance of developmental similarities. At this comparable developmental stage, a chick embryo and a pig embryo have many features in common, which suggests the two animals evolved from a common ancestor.
1. Explain the steps in the theory of natural selection. a. heritable variations
The members of a population have heritable variations i. Darwin emphasized that the members of a population vary in their functional, physical, and behavioral characteristics. Prior to Darwin, variations were considered imperfections that should be ignored, since they were not important to the description of a species. Darwin, on the other hand, realized that variations are essential to the natural selection process. Darwin suspected that the occurrence of variations is completely random; they arise by accident and for no particular purpose. i. We now know that genes, together with the environment, determine the phenotype of an organism. The genes that each organism inherits are based on the assortment of chromosomes during meiosis and fertilization. New alleles of a gene are the result of inheritable mutations in the DNA of the organism. These mutations are more likely to be harmful than beneficial to an organism. However, occasionally, a mutation occurs that produces a benefit to the organism, such as a change in camouflage. This type of variation, which makes adaptation to an environment possible, is passed on from generation to generation.
Summarize the contributions of Cuvier and Lamarck to the study of evolutionary change b. inheritance of acquired characteristics
To explain the process of adaptation to the environment, Lamarck proposed the idea of inheritance of acquired characteristics, in which the use or disuse of a structure can bring about inherited change. One example Lamarck gave—and the one for which he is most famous—is that the long neck of giraffes developed over time because giraffes stretched their necks to reach food high in trees and then passed on a long neck to their offspring. However, the inheritance of acquired characteristics is not the primary mechanism that drives the change in species over time.
Describe and give examples of the following evidences for evolution d. molecular evidence iii. Cytochrome C
When the degree of similarity in DNA base sequences of genes or in amino acid sequences of proteins is examined, the data are as expected, assuming common descent. Cytochrome c is a molecule used in the electron transport chain of all organisms shown in Figure 14.18. Data regarding differences in the amino acid sequence of cytochrome c show that the sequence in a human differs from that in a monkey by only 1 amino acid, from that in a duck by 11 amino acids, and from that in Candida, a yeast, by 51 amino acids. These data are consistent with other data regarding the anatomical similarities of these organisms, and therefore demonstrate their relatedness. According to cytochrome c: We are related to pigs in a little less than 10 amino acids We are related to turtles in about 13 amino acids Fish about 20 Moth about 30
Explain how Darwin's study of fossils and biogeography contributed to the development of the theory of natural selection f. finch beak diversity
a. Although some of the finches on the Galápagos Islands seemed like mainland finches, others were quite different. i. Today, there are ground-dwelling finches with beak sizes dependent on the sizes of the seeds they eat. ii. Tree-dwelling finches have beak sizes and shapes dependent on the sizes of their insect prey. 1. A cactus-eating finch possesses a more pointed beak, enabling access to nectar within cactus flowers. 2. The most unusual of the finches is a woodpecker-type finch. A woodpecker normally has a sharp beak to chisel through tree bark and a long tongue to probe for insects. The Galápagos woodpecker-type finch has the sharp beak but lacks the long tongue. To make up for this, the bird carries a twig or cactus spine in its beak and uses it to poke into crevices. Once an insect emerges, the finch drops this tool and seizes the insect with its beak.
Summarize the contributions of Cuvier and Lamarck to the study of evolutionary change a. Catastrophists
a. Catastrophists believe that catastrophes cause mass extinctions whenever new stratum of that region show a new mix of fossils. After each catastrophe, the region was repopulated by species from surrounding areas, which accounted for the appearance of new fossils in the new stratum. The result of all these catastrophes was change appearing over time. i. Cuvier's followers came to be called catastrophists. They even suggested that worldwide catastorphes had occurred and that, after each of these events, new sets of species had been created.
Explain the steps in the theory of natural selection. c. differential reproduction (competition)
a. The individuals that have favorable traits survive and reproduce to a greater extent than those that lack these traits i. Because each generation has the same reproductive potential as the previous generation, there is a constant struggle for existence, and only certain members of a population survive and reproduce each generation.
1. Explain the steps in the theory of natural selection. b. overreproduction of offspring
a. The population produces more offspring than the resources of an environment can support i. In Darwin's time, a socioeconomist named Thomas Malthus stressed the reproductive potential of humans. He proposed that death and famine are inevitable, because the human population tends to increase faster than the supply of food. Darwin applied this concept to all organisms and saw that the available resources were not sufficient to allow all members of a population to survive. He calculated the reproductive potential of elephants and concluded that, after only 750 years, the descendants of a single pair of elephants would number about 19 million! Obviously, no environment has the resources to support an elephant population of this magnitude. Because each generation has the same reproductive potential as the previous generation, there is a constant struggle for existence, and only certain members of a population survive and reproduce each generation.
Describe and give examples of the following evidences for evolution d. molecular evidence i. DNA code
· All living organisms use the same basic biological molecules, including DNA (deoxyribonucleic acid), ATP (adenosine triphosphate), and many identical or nearly identical enzymes. Further, organisms utilize the same DNA triplet code and the same 20 amino acids in their proteins. Now that we know the sequence of DNA bases in the genomes of many organisms, it has become clear that humans share a large number of genes with much simpler organisms.
Organisms become adapted
· An adaptation may take many generations to evolve. We can especially recognize an adaptation when unrelated organisms living in a particular environment display similar characteristics. For example, manatees, penguins, and sea turtles all have flippers, which help them move through the water—also an example of convergent evolution. Adaptations also account for why organisms are able to escape their predators and why they are suited to their way of life. Natural selection causes adaptive traits to be increasingly represented in each succeeding generation. There are other processes at work in the evolution of populations, but it is the process of natural selection that allow a population to adapt to its environment.
Identify what Darwin couldn't explain about variations
· Darwin emphasized that the members of a population vary in their functional, physical, and behavioral characteristics. Prior to Darwin, variations were considered imperfections that should be ignored, since they were not important to the description of a species. Darwin, on the other hand, realized that variations are essential to the natural selection process. Darwin suspected that the occurrence of variations is completely random; they arise by accident and for no particular purpose. Darwin didn't know how variations come about Darwin didn't know how plants and animals passed down traits Darwin didn't understand genetics or heredity *******Darwin didn't know the source of variation and the mechanism for passing change from generation to generation. Darwin didn't know how plants or animals passed down traits. He didn't know about genetics. Darwin had a lack of explanation for heredity.****** (pg 93) Darwin's supposition that variation was unlimited, and so in time could give rise to strikingly different organisms, was not entirely convincing because he had no idea of where variation came from.
Distinguish between natural and artificial selection
· Darwin noted that, when humans carry out artificial selection, they breed selected animals that have particular traits they want to reproduce. For example, prehistoric humans probably noted desirable variations among wolves and selected particular individuals for breeding. Therefore, the desired traits increased in frequency in the next generation. The same process was repeated many times, resulting in today's numerous varieties of dogs, all descended from the wolf. In a similar way, several varieties of vegetables can be traced to a single ancestor. Chinese cabbage, brussels sprouts, and kohlrabi are all derived from a single sepcies, Brassica oleracea. · In nature, interactions with the environment determine which members of a population reproduce to a greater degree than other members. In contrast to artificial selection, the result of natural selection is not predesired. Natural selection occurs because certain members of a population happen to have a variation that allows them to survive and reproduce to a greater extent than other members. For example, any variation that increase the speed of a hoofed animal helps it escape predators and live longer; a variation that reduces water loss is beneficial to a desert plant; and one that increases the sense of smell helps a wild dog find its prey. Therefore, we expect the organisms with these characteristics to have increased fitness. Figure 14.9 contrasts Lamarck's ideas with those of Darwin.
Describe and give examples of the following evidences for evolution c. anatomical evidence iv. vestigial structures
· Darwin was able to show that a hypothesis of common descent offers a plausible explanation for vestigial structures and anatomical similarities among organisms. · Vestigial structures are anatomical features that are fully developed in one group of organisms but reduced and nonfunctional in other, similar groups. Most birds, for example, have well-developed wings used for flight. However, some bird species (e.g., ostrich) have greatly reduced wings and do not fly. Similarly, whales (see Fig 14.14) and snakes have no use for hindlimbs, yet extinct whales and snakes had remnants of hip bones and legs. Humans have a tailbone but no tail. The presence of vestigial structures can be explained by the common descent hypothesis. Vestigial structures occur because organisms inherit their anatomy from their ancestors; they are traces of an organism's evolutionary history.
Explains what determines the evolutionary success (fitness) of an organism
· Fitness is the reproductive success of an individual relative to other members of the population. Fitness is determined by comparing the numbers of surviving fertile offspring that are produced by each member of the population. The most fit individuals are the ones that capture a disproportionate amount of resources and convert these resources into a larger number of viable offspring. Because organisms vary anatomically and physiologically, and because the challenges of local environments vary, what determines fitness varies for different populations. For example, among western diamondback rattlesnakes living on lava flows, the most fit are those that are black. Among those living on desert soil, the most fit are typically light-colored with brown blotching. Background matching helps an animal both capture prey and avoid being captured; therefore, it is expected to lead to survival and increased reproduction. · Natural selection occurs because certain members of a population happen to have a variation that allows them to survive and reproduce to a greater extent than other members.
Describe and give examples of the following evidences for evolution a. fossil record iii. Synapsids
· Important because documents the evolutionary history of many distinctive features of mammals like the presence of a bony secondary palate, incorporation of bones from the lower jaw into the middle ear They are mammal-like reptiles · -Mammal-like features: They could be distinguished by a single large opening in the cheek, likely for jaw muscles; bony secondary palate, incorporation of bones from the lower jaw into the middle ear, teeth with complex occlusion patterns, upright limbs, the presence of a single opening behind the eye socket around which jaw musculature attaches · Reptiles that slowly began to evolve into mammals · They are more closely related to the extant mammal than to any reptile · They are an extinct species · Most striking changes was in their lower jaws—throughout synapsid evolution, the non-dentary elements in the jaw were crowded towards the back and were eventually lost. The dentary bone got larger and eventually took over the jaw until it made contact with the skull and developed a new articulation with it. Many of these non-dentary bones became the bones in the mammalian middle ear , becoming the malleus ("hammer") and incus ("anvil") bones Non-mammalian synapsids are an extremely important part of the fossil record because they document the evolutionary history of many of the distinctive features of mammals, such as the presence of a bony secondary palate, the incorporation of bones from the lower jaw into the middle ear, teeth with complex occlusion patterns, and upright limbs. Morphological features, such as the presence of a single opening behind the eye socket around which jaw musculature attaches, helps us recognize members of the synapsid lineage in the fossil record.
Describe and give examples of the three great classes of data as defined by Stephen Jay Gould, that support the idea that evolution has occurred: a. Direct evidence of small scale changes
· Our confidence in the fact of evolution rests upon copious data that fall, roughly, into three great classes. o First, we have the direct evidence of small-scale changes in controlled laboratory experiments of the past hundred years (on bacteria, on almost every measurable property of the fruit fly Drosophila) o or observed in nature (color changes in moth wings, development of metal tolerance in plants growing near industrial waste heaps) o or produced during a few thousand years of human breeding and agriculture. o Creationists can scarcely ignore this evidence, so they respond by arguing that God permits limited modification within created types, but that you can never change a cat into a dog (who ever said that you could, or that nature did?).
Describe and give examples of the three great classes of data as defined by Stephen Jay Gould, that support the idea that evolution has occurred: b. Direct evidence of large scale changes
· Second, we have direct evidence for large-scale changes, based upon sequences in the fossil record. · The nature of this evidence is often misunderstood by non-professionals who view evolution as a simple ladder of progress, and therefore expect a linear array of ''missing links.'' But evolution is a copiously branching bush, not a ladder. Since our fossil record is so imperfect, we can't hope to find evidence for every tiny twiglet. (Sometimes, in rapidly evolving lineages of abundant organisms restricted to a small area and entombed in sediments with an excellent fossil record, we do discover an entire little bush -- but such examples are as rare as they are precious.) · In the usual case, we may recover the remains of side branch number 5 from the bush's early history, then bough [a main branch of a tree] number 40 a bit later, then the full series of branches 156-161 in a well preserved sequence of younger rocks, and finally surviving twigs 250 and 287. · In other words, we usually find sequences of structural intermediates, not linear arrays of ancestors and descendants. · NUMBER 1) Such sequences provide superb examples of temporally ordered evo- lutionary trends. Consider the evidence for human evolution in Africa. What more could you ask from a record of rare creatures living in terrestrial environments that provide poor opportunity for fossilization? · We have a temporal sequence displaying clear trends in a suite of features, including threefold increase of brain size and corresponding decrease of jaws and teeth. (We are missing direct evidence for an earlier transition to upright posture, but wide-ranging and unstudied sediments of the right age have been found in East Africa, and we have an excellent chance to fill in this part of our story.) · What alternative can we suggest to evolution? Would God -- for some inscrutable reason, or merely t test our faith -- create five species, one after the other (Australopithecus afarensis, A. africanus, Homo habilis, H. erectus, and H. sapiens), to mimic a continuous trend of evolutionary change? NUMBER 2) Or, consider another example with evidence of structurally intermediate stages -- the transition from reptiles to mammals. The lower jaw of mammals contains but a single bone, the dentary. Reptiles build their lower jaws of several bones. In perhaps the most fascinating of those quirky changes in function that mark pathways of evolution, the two bones articulating the upper and lower jaws of reptiles migrate to the middle ear and become the malleus and incus (hammer and anvil) of mammals. · Creationists, ignorant of hard evi dence in the fossil record, scoff at this tale. How could jaw bones become ear bones, they ask. What happened in between? An animal can't work with a jaw half disarticulated during the stressful time of transition. · The fossil record provides a direct answer. In an excellent series of temporally ordered structural intermediates, the reptilian dentary gets larger and larger, pushing back as the other bones of a reptile's lower jaw decrease in size. · We've even found a transitional form with an elegant solution to the problem of remaking jaw bones into ear bones. This creature has a double articulation -- one between the two bones that become the mammalian hammer and anvil (the old reptilian joint), and a second between the squamosal and dentary bones (the modern mammalian condi- tion). · With this built-in redundancy, the emerging mammals could abandon one connection by moving two bones into the ear, while retaining the second linkage, which becomes the sole articulation of modern mammals.
Describe and give examples of the three great classes of data as defined by Stephen Jay Gould, that support the idea that evolution has occurred: c. Imperfections that reflect historical descent
· Third, and most persuasive in its ubiquity, we have the signs of history preserved within every organism, every ecosystem, and every pattern of biogeographic distribution, by those pervasive quirks, oddities, and imperfections that record pathways of historical descent. These evidences are indirect, since we are viewing modern results, not the processes that caused them, but what else can we make of the pervasive pattern? o Why does our body, from the bones of our back to the musculature of our belly, display the vestiges of an arrangement better suited for quadrupedal life if we aren't the descendants of four-footed creatures? o Why do the plants and animals of the Galapagos so closely resemble, but differ slightly from, the creatures of Ecuador, the nearest bit of land 600 miles to the east, especially when cool oceanic currents and volcanic substrate make the Galapagos such a different environment from Ecuador (thus removing the potential argument that God makes the best creatures for each place, and small differences only reflect a minimal disparity of environments)? The similarities can only mean that Ecuadorian creatures colonized the Galapagos and then diverged by a natural process of evolution. · This method of searching for oddities as vestiges of the past isn't peculiar to evolution, but a common procedure of all historical science. How, for example, do we know that words have histories, and haven't been decreed by some all-knowing committee in Mr. Orwell's bureau of New- speak? Doesn't the bucolic etymology of so many words testify to a different life style among our ancestors? In this article, I try to ''broadcast'' some ideas (a mode of sowing seed) in order to counter the most ''egregious'' [outstandingly bad, shocking] of creationist sophistries [use of fallacious arguments, especially with the intention of deceiving] (the animal ex grege, or outside the flock), for which, given the quid pro quo of business, this fine magazine pays me an ''emolument'' (the fee that millers once received to grind corn). · I don't want to sound like a shrill dogmatist shouting ''rally round the flag boys,'' but biologists have reached a consensus, based on these kinds of data, about the fact of evolution. When honest critics like Irving Kristol misinterpret this agreement, they're either confusing our fruitful consonance [agreement] about the fact of evolution with our vibrant dissonance about mechanisms of change, or they've misinterpreted part of our admittedly arcane technical literature.
