Biology Ii Evolutionary Reading Review Pg 37 Answers

Learning Objectives

By the stop of this section, you lot will be able to do the following:

• Describe how scientists adult the present-twenty-four hour period theory of development
• Ascertain accommodation
• Explain convergent and divergent evolution
• Describe homologous and vestigial structures
• Discuss misconceptions nigh the theory of evolution

Development past natural option describes a mechanism for how species change over time. Scientists, philosophers, researchers, and others had made suggestions and debated this topic well earlier Darwin began to explore this idea. Classical Greek philosopher Plato emphasized in his writings that species were static and unchanging, nonetheless at that place were besides ancient Greeks who expressed evolutionary ideas. In the eighteenth century, naturalist Georges-Louis Leclerc Comte de Buffon reintroduced ideas about the development of animals and observed that diverse geographic regions have unlike institute and fauna populations, fifty-fifty when the environments are similar. Some at this fourth dimension also accustomed that there were extinct species.

Also during the eighteenth century, James Hutton, a Scottish geologist and naturalist, proposed that geological modify occurred gradually past accumulating minor changes from processes operating similar they are today over long periods of fourth dimension. This contrasted with the predominant view that the planet'southward geology was a consequence of catastrophic events occurring during a relatively cursory past. Nineteenth century geologist Charles Lyell popularized Hutton's view. A friend to Darwin. Lyell's ideas were influential on Darwin's thinking: Lyell'southward notion of the greater age of World gave more time for gradual change in species, and the procedure of alter provided an analogy for this change. In the early on nineteenth century, Jean-Baptiste Lamarck published a book that detailed a mechanism for evolutionary change. We at present refer to this mechanism as an inheritance of acquired characteristics by which the environment causes modifications in an individual, or offspring could use or decay of a structure during its lifetime, and thus bring about change in a species. While many discredited this mechanism for evolutionary modify, Lamarck's ideas were an important influence on evolutionary thought.

Charles Darwin and Natural Selection

In the mid-nineteenth century, ii naturalists, Charles Darwin and Alfred Russel Wallace, independently conceived and described the bodily mechanism for evolution. Chiefly, each naturalist spent time exploring the natural world on expeditions to the tropics. From 1831 to 1836, Darwin traveled effectually the globe on H.1000.South. Beagle, including stops in South America, Australia, and the southern tip of Africa. Wallace traveled to Brazil to collect insects in the Amazon rainforest from 1848 to 1852 and to the Malay Archipelago from 1854 to 1862. Darwin'due south journeying, like Wallace's later journeys to the Malay Archipelago, included stops at several island bondage, the terminal being the Galápagos Islands west of Ecuador. On these islands, Darwin observed species of organisms on unlike islands that were clearly similar, yet had distinct differences. For case, the footing finches inhabiting the Galápagos Islands comprised several species with a unique beak shape (Figure eighteen.two). The species on the islands had a graded serial of beak sizes and shapes with very minor differences between the well-nigh similar. He observed that these finches closely resembled another finch species on the South American mainland. Darwin imagined that the island species might be species modified from one of the original mainland species. Upon further study, he realized that each finch's varied beaks helped the birds acquire a specific type of nutrient. For example, seed-eating finches had stronger, thicker beaks for breaking seeds, and insect-eating finches had spear-like beaks for stabbing their prey.

Figure 18.ii Darwin observed that beak shape varies among finch species. He postulated that ancestral species' beaks had adapted over time to equip the finches to learn dissimilar food sources.

Wallace and Darwin both observed like patterns in other organisms and they independently developed the same caption for how and why such changes could take place. Darwin called this mechanism natural selection. Natural option, or "survival of the fittest," is the more prolific reproduction of individuals with favorable traits that survive environmental change because of those traits. This leads to evolutionary change.

For example, Darwin observed a population of behemothic tortoises in the Galápagos Archipelago to accept longer necks than those that lived on other islands with dry lowlands. These tortoises were "selected" considering they could reach more leaves and access more food than those with short necks. In times of drought when fewer leaves would be available, those that could attain more leaves had a meliorate chance to eat and survive than those that couldn't reach the food source. Consequently, long-necked tortoises would exist more than likely to be reproductively successful and pass the long-necked trait to their offspring. Over fourth dimension, only long-necked tortoises would be present in the population.

Natural pick, Darwin argued, was an inevitable outcome of iii principles that operated in nature. First, most characteristics of organisms are inherited, or passed from parent to offspring. Although no one, including Darwin and Wallace, knew how this happened at the fourth dimension, it was a mutual understanding. Second, more offspring are produced than are able to survive, so resources for survival and reproduction are express. The capacity for reproduction in all organisms outstrips the availability of resource to support their numbers. Thus, there is contest for those resources in each generation. Both Darwin and Wallace's understanding of this principle came from reading economist Thomas Malthus' essay that explained this principle in relation to human populations. Tertiary, offspring vary among each other in regard to their characteristics and those variations are inherited. Darwin and Wallace reasoned that offspring with inherited characteristics which allow them to all-time compete for limited resources will survive and have more offspring than those individuals with variations that are less able to compete. Because characteristics are inherited, these traits will be ameliorate represented in the next generation. This will lead to change in populations over generations in a process that Darwin called descent with modification. Ultimately, natural option leads to greater adaptation of the population to its local environment. Information technology is the only mechanism known for adaptive evolution.

In 1858, Darwin and Wallace (Figure 18.three) presented papers at the Linnean Society in London that discussed the idea of natural option. The following year Darwin's volume, On the Origin of Species, was published. His book outlined in considerable detail his arguments for development by natural selection.

Figure 18.three Both (a) Charles Darwin and (b) Alfred Wallace wrote scientific papers on natural selection that they presented together at the Linnean Lodge in 1858.

Information technology is difficult and time-consuming to document and present examples of development by natural selection. The Galápagos finches are an first-class instance. Peter and Rosemary Grant and their colleagues have studied Galápagos finch populations every year since 1976 and have provided important bear witness of natural selection. The Grants found changes from ane generation to the next in bill shape distribution with the medium ground finch on the Galápagos island of Daphne Major. The birds have inherited a variation in their bill shape with some having broad deep bills and others having thinner bills. During a period in which rainfall was college than normal because of an El Niño, there was a lack of large hard seeds of which the large-billed birds ate; however, there was an affluence of the small soft seeds which the small-billed birds ate. Therefore, the pocket-sized-billed birds were able to survive and reproduce. In the years following this El Niño, the Grants measured beak sizes in the population and found that the average beak size was smaller. Since bill size is an inherited trait, parents with smaller bills had more offspring and the pecker evolved into a much smaller size. As conditions improved in 1987 and larger seeds became more available, the trend toward smaller boilerplate nib size ceased.

Career Connection

Career Connection

Field BiologistMany people hike, explore caves, scuba dive, or climb mountains for recreation. People oftentimes participate in these activities hoping to see wildlife. Experiencing the outdoors can be incredibly enjoyable and invigorating. What if your chore entailed working in the wilderness? Field biologists past definition work outdoors in the "field." The term field in this instance refers to whatsoever location outdoors, even under water. A field biologist typically focuses research on a certain species, grouping of organisms, or a single habitat (Figure eighteen.iv).

Figure 18.4 A field biologist tranquilizes a polar bear for written report. (credit: Karen Rhode)

One objective of many field biologists includes discovering new, unrecorded species. Not only do such findings expand our understanding of the natural world, but they also lead to of import innovations in fields such as medicine and agriculture. Plant and microbial species, in particular, can reveal new medicinal and nutritive knowledge. Other organisms can play key roles in ecosystems or if rare crave protection. When discovered, researchers can use these of import species as evidence for environmental regulations and laws.

Processes and Patterns of Evolution

Natural pick can simply take place if at that place is variation, or differences, amid individuals in a population. Importantly, these differences must accept some genetic ground; otherwise, the selection will not lead to change in the next generation. This is disquisitional considering nongenetic reasons tin can cause variation amongst individuals such as an individual's peak because of better nutrition rather than different genes.

Genetic diversity in a population comes from two chief mechanisms: mutation and sexual reproduction. Mutation, a modify in DNA, is the ultimate source of new alleles, or new genetic variation in whatever population. The genetic changes that mutation causes tin can take one of three outcomes on the phenotype. A mutation affects the organism's phenotype in a way that gives information technology reduced fitness—lower likelihood of survival or fewer offspring. A mutation may produce a phenotype with a beneficial effect on fettle. Many mutations will also accept no effect on the phenotype'south fitness. We call these neutral mutations. Mutations may also have a whole range of effect sizes on the organism'south fettle that expresses them in their phenotype, from a pocket-size effect to a great issue. Sexual reproduction also leads to genetic diversity: when two parents reproduce, unique combinations of alleles assemble to produce the unique genotypes and thus phenotypes in each offspring.

Nosotros call a heritable trait that helps an organism's survival and reproduction in its nowadays environment an adaptation. Scientists depict groups of organisms adapting to their surroundings when a genetic variation occurs over time that increases or maintains the population'due south "fit" to its surround. A platypus'south webbed feet are an adaptation for swimming. A snowfall leopard's thick fur is an adaptation for living in the cold. A cheetah'southward fast speed is an adaptation for catching casualty.

Whether or not a trait is favorable depends on the electric current environmental weather condition. The same traits are not e'er selected because environmental conditions can alter. For example, consider a institute species that grew in a moist climate and did not need to conserve h2o. Large leaves were selected because they allowed the found to obtain more energy from the sun. Large leaves require more water to maintain than small leaves, and the moist surround provided favorable conditions to support large leaves. After thousands of years, the climate changed, and the expanse no longer had excess water. The direction of natural selection shifted so that plants with minor leaves were selected because those populations were able to conserve water to survive the new environmental conditions.

The evolution of species has resulted in enormous variation in form and function. Sometimes, evolution gives rise to groups of organisms that become tremendously different from each other. Nosotros phone call two species that evolve in various directions from a mutual betoken divergent development. We can see such divergent evolution in the forms of the reproductive organs of flowering plants which share the aforementioned basic anatomies; however, they tin can look very different as a event of choice in different physical environments and adaptation to different kinds of pollinators (Figure xviii.5).

Effigy 18.5 Flowering plants evolved from a common antecedent. Discover that the (a) dense blazing star (Liatrus spicata) and the (b) majestic coneflower (Echinacea purpurea) vary in appearance, yet both share a like basic morphology. (credit a: modification of piece of work past Drew Avery; credit b: modification of work by Cory Zanker)

In other cases, like phenotypes evolve independently in distantly related species. For example, flight has evolved in both bats and insects, and they both have structures we refer to as wings, which are adaptations to flight. All the same, bat and insect wings take evolved from very dissimilar original structures. Nosotros call this miracle convergent evolution, where similar traits evolve independently in species that practise not share a common beginnings. The two species came to the same function, flying, but did so separately from each other.

These physical changes occur over enormous time spans and help explain how evolution occurs. Natural option acts on individual organisms, which can so shape an unabridged species. Although natural selection may work in a single generation on an private, it can accept thousands or even millions of years for an unabridged species' genotype to evolve. It is over these large time spans that life on earth has changed and continues to modify.

Evidence of Evolution

The prove for development is compelling and extensive. Looking at every level of system in living systems, biologists come across the signature of past and present evolution. Darwin defended a large portion of his book, On the Origin of Species, to identifying patterns in nature that were consistent with evolution, and since Darwin, our understanding has become clearer and broader.

Fossils

Fossils provide solid evidence that organisms from the past are non the same equally those today, and fossils show the gradual evolutionary changes over fourth dimension. Scientists determine the age of fossils and categorize them from all over the world to determine when the organisms lived relative to each other. The resulting fossil record tells the story of the past and shows the evolution of class over millions of years (Figure 18.six). For example, scientists have recovered highly detailed records showing the evolution of humans and horses (Figure 18.half-dozen). The whale flipper shares a similar morphology to bird and mammal appendages (Figure 18.7) indicating that these species share a common ancestor.

Effigy xviii.6 In this (a) display, fossil hominids are arranged from oldest (bottom) to newest (elevation). As hominids evolved, the skull's shape inverse. An artist's rendition of (b) extinct species of the genus Equus reveals that these ancient species resembled the modern horse (Equus ferus) but varied in size.

Anatomy and Embryology

Another type of evidence for evolution is the presence of structures in organisms that share the aforementioned bones form. For example, the basic in human, domestic dog, bird, and whale appendages all share the aforementioned overall construction (Figure 18.7) resulting from their origin in a common ancestor's appendages. Over time, evolution led to changes in the bones' shapes and sizes in dissimilar species, but they have maintained the aforementioned overall layout. Scientists call these synonymous parts homologous structures.

Figure 18.vii The like structure of these appendages indicates that these organisms share a common ancestor.

Some structures exist in organisms that have no credible part at all, and appear to be residue parts from a past mutual ancestor. Nosotros telephone call these unused structures without office vestigial structures. Other examples of vestigial structures are wings on flightless birds, leaves on some cacti, and hind leg bones in whales. Non all similarities stand for homologous structures. Every bit explained in Determining Evolutionary Relationships, when similar characteristics occur considering of environmental constraints and non due to a shut evolutionary relationship, it is an analogy or homoplasy. For example, insects use wings to fly like bats and birds, but the fly structure and embryonic origin are completely different. These are coordinating structures (Figure 20.eight).

Link to Learning

Link to Learning

Watch this video exploring the basic in the homo trunk.

Some other testify of evolution is the convergence of course in organisms that share like environments. For example, species of unrelated animals, such every bit the arctic trick and ptarmigan, living in the arctic region have been selected for seasonal white phenotypes during winter to blend with the snowfall and ice (Effigy eighteen.8). These similarities occur non because of common beginnings, just considering of similar selection pressures—the benefits of predators not seeing them.

Effigy 18.eight The white winter coat of the (a) chill play a joke on and the (b) ptarmigan'due south plume are adaptations to their environments. (credit a: modification of work by Keith Morehouse)

Embryology, the study of the anatomy of an organism's development to its adult course, also provides prove of relatedness between now widely divergent groups of organisms. Mutational tweaking in the embryo can have such magnified consequences in the adult that tends to conserve embryo germination. As a result, structures that are absent in some groups often appear in their embryonic forms and disappear when they attain the developed or juvenile form. For example, all vertebrate embryos, including humans, exhibit gill slits and tails at some point in their early development. These disappear in the adults of terrestrial groups but adult forms of aquatic groups such every bit fish and some amphibians maintain them. Great ape embryos, including humans, have a tail structure during their development that they lose when they are born.

Biogeography

The geographic distribution of organisms on the planet follows patterns that we can explain all-time by development in conjunction with tectonic plate move over geological time. Wide groups that evolved earlier the supercontinent Pangaea broke up (about 200 million years agone) are distributed worldwide. Groups that evolved since the breakup appear uniquely in regions of the planet, such as the unique flora and creature of northern continents that formed from the supercontinent Laurasia and of the southern continents that formed from the supercontinent Gondwana. The presence of members of the plant family Proteaceae in Australia, southern Africa, and Due south America was most predominant prior to the southern supercontinent Gondwana breaking up.

Marsupial diversification in Australia and the absence of other mammals reflect Australia's long isolation. Australia has an abundance of endemic species—species found nowhere else—which is typical of islands whose isolation by expanses of water prevents species to migrate. Over time, these species diverge evolutionarily into new species that wait very different from their ancestors that may exist on the mainland. Commonwealth of australia'south marsupials, the Galápagos' finches, and many species on the Hawaiian Islands are all unique to their one point of origin, yet they brandish distant relationships to ancestral species on mainlands.

Molecular Biology

Like anatomical structures, the molecular structures of life reverberate descent with modification. Dna'due south universality reflects evidence of a mutual ancestor for all of life. Primal divisions in life between the genetic code, DNA replication, and expression are reflected in major structural differences in otherwise conservative structures such as ribosome components and membrane structures. In general, the relatedness of groups of organisms is reflected in the similarity of their DNA sequences—exactly the pattern that we would expect from descent and diversification from a common ancestor.

DNA sequences have also shed light on some of the mechanisms of evolution. For example, information technology is clear that the development of new functions for proteins normally occurs after factor duplication events that allow freely modifying one copy by mutation, selection, or drift (changes in a population'south genetic pool resulting from take a chance), while the second copy continues to produce a functional protein.

Misconceptions of Evolution

Although the theory of evolution generated some controversy when Darwin first proposed information technology, biologists most universally accustomed it, particularly younger biologists, within 20 years after publication of On the Origin of Species. Nevertheless, the theory of evolution is a hard concept and misconceptions about how it works grow.

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Link to Learning

This site addresses some of the main misconceptions associated with the theory of evolution.

Evolution Is Merely a Theory

Critics of the theory of evolution dismiss its importance by purposefully confounding the everyday usage of the word "theory" with the way scientists use the word. In science, we understand a "theory" to exist a body of thoroughly tested and verified explanations for a prepare of observations of the natural world. Scientists have a theory of the atom, a theory of gravity, and the theory of relativity, each which describes understood facts about the globe. In the same fashion, the theory of evolution describes facts about the living world. Every bit such, a theory in scientific discipline has survived pregnant efforts to discredit it by scientists. In dissimilarity, a "theory" in mutual vernacular is a word pregnant a guess or suggested explanation. This pregnant is more than alike to the scientific concept of "hypothesis." When critics of evolution say it is "simply a theory," they are implying that at that place is niggling evidence supporting it and that it is still in the procedure of rigorous testing. This is a mischaracterization.

Individuals Evolve

Evolution is the change in a population's genetic composition over time, specifically over generations, resulting from differential reproduction of individuals with certain alleles. Individuals do modify over their lifetime, obviously, but this is evolution and involves changes programmed past the set of genes the individual acquired at birth in coordination with the individual's environment. When thinking almost the evolution of a characteristic, it is probably best to think nigh the change of the average value of the feature in the population over fourth dimension. For example, when natural option leads to bill-size modify in medium basis finches in the Galápagos, this does non mean that individual bills on the finches are irresolute. If ane measures the average bill size among all individuals in the population at i time then measures them in the population several years later, this boilerplate value will be different equally a upshot of evolution. Although some individuals may survive from the outset time to the 2d, they will still have the same beak size; nevertheless, there will be many new individuals who contribute to the shift in average bill size.

Development Explains the Origin of Life

It is a common misunderstanding that evolution includes an explanation of life'south origins. Conversely, some of the theory's critics believe that it cannot explain the origin of life. The theory does not endeavor to explicate the origin of life. The theory of evolution explains how populations change over fourth dimension and how life diversifies the origin of species. Information technology does not shed light on the ancestry of life including the origins of the get-go cells, which define life. Importantly, biologists believe that the presence of life on Earth precludes the possibility that the events that led to life on Earth can repeat themselves because the intermediate stages would immediately become food for existing living things.

Nevertheless, once a mechanism of inheritance was in place in the form of a molecule like Dna either within a cell or pre-cell, these entities would be subject to the principle of natural selection. More constructive reproducers would increase in frequency at the expense of inefficient reproducers. While evolution does not explicate the origin of life, it may have something to say nearly some of the processes operating once pre-living entities caused certain properties.

Organisms Evolve on Purpose

Statements such as "organisms evolve in response to a change in an surroundings" are quite common, but such statements tin can lead to 2 types of misunderstandings. Get-go, do not interpret the statement to mean that private organisms evolve. The statement is shorthand for "a population evolves in response to a changing environment." However, a second misunderstanding may arise past interpreting the statement to mean that the evolution is somehow intentional. A changed environment results in some individuals in the population, those with particular phenotypes, benefiting and therefore producing proportionately more than offspring than other phenotypes. This results in alter in the population if the characteristics are genetically determined.

It is also important to understand that the variation that natural choice works on is already in a population and does non arise in response to an ecology change. For example, applying antibiotics to a population of bacteria will, over time, select a population of leaner that are resistant to antibiotics. The resistance, which a factor causes, did non arise past mutation because of applying the antibiotic. The gene for resistance was already present in the leaner's gene pool, likely at a low frequency. The antibiotic, which kills the bacterial cells without the resistance factor, strongly selects individuals that are resistant, since these would be the only ones that survived and divided. Experiments take demonstrated that mutations for antibody resistance do not arise as a result of antibiotic.

In a larger sense, development is non goal directed. Species do non become "better" over fourth dimension. They simply rails their irresolute environment with adaptations that maximize their reproduction in a particular environs at a particular time. Evolution has no goal of making faster, bigger, more complex, or fifty-fifty smarter species, despite the commonness of this kind of linguistic communication in popular discourse. What characteristics evolve in a species are a function of the variation nowadays and the surroundings, both of which are constantly changing in a nondirectional manner. A trait that fits in i environment at 1 time may well be fatal at some betoken in the future. This holds equally well for insect and man species.

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Source: https://openstax.org/books/biology-2e/pages/18-1-understanding-evolution

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