romikgosai/squad_modified_2 huggingface dataset:
Darwin proposes sexual selection, driven by competition between males for mates, to explain sexually dimorphic features such as lion manes, deer antlers, peacock tails, bird songs, and the bright plumage of some male birds. He analysed sexual selection more fully in The Descent of Man, and Selection in Relation to Sex (1871). Natural selection was expected to work very slowly in forming new species, but given the effectiveness of artificial selection, he could "see no limit to the amount of change, to the beauty and infinite complexity of the coadaptations between all organic beings, one with another and with their physical conditions of life, which may be effected in the long course of time by nature's power of selection". Using a tree diagram and calculations, he indicates the "divergence of character" from original species into new species and genera. He describes branches falling off as extinction occurred, while new branches formed in "the great Tree of life ... with its ever branching and beautiful ramifications".

Q1: What does Darwin say can explain diverse feature such as antlers on deer and bright feathers on certain male birds?
A1: sexual selection, driven by competition between males for mates
Q2: Which of Darwin's written works has more in depth information about sexual selection?
A2: The Descent of Man, and Selection in Relation to Sex
Q3: What did Darwin expect to see between species with the addition of artificial selection?
A3: no limit to the amount of change, to the beauty and infinite complexity of the coadaptations between all organic beings
Q4: What did Darwin use to illustrate the way that original species change and adapt into new ones?
A4: a tree diagram and calculations
In Darwin's time there was no agreed-upon model of heredity; in Chapter I Darwin admitted, "The laws governing inheritance are quite unknown." He accepted a version of the inheritance of acquired characteristics (which after Darwin's death came to be called Lamarckism), and Chapter V discusses what he called the effects of use and disuse; he wrote that he thought "there can be little doubt that use in our domestic animals strengthens and enlarges certain parts, and disuse diminishes them; and that such modifications are inherited", and that this also applied in nature. Darwin stated that some changes that were commonly attributed to use and disuse, such as the loss of functional wings in some island dwelling insects, might be produced by natural selection. In later editions of Origin, Darwin expanded the role attributed to the inheritance of acquired characteristics. Darwin also admitted ignorance of the source of inheritable variations, but speculated they might be produced by environmental factors. However, one thing was clear: whatever the exact nature and causes of new variations, Darwin knew from observation and experiment that breeders were able to select such variations and produce huge differences in many generations of selection. The observation that selection works in domestic animals is not destroyed by lack of understanding of the underlying hereditary mechanism.

Q1: What is the theory that is based on acquired characteristics within a species?
A1: Lamarckism
Q2: What did Darwin learn about about the characteristics of domestic animals?
A2: use in our domestic animals strengthens and enlarges certain parts, and disuse diminishes them
Q3: What did Darwin speculate might be how inheritable variations might come about in a species?
A3: environmental factors
Q4: What did Darwin admit about acquired characteristics in chapter one of On the Origin of Species?
A4: "The laws governing inheritance are quite unknown."
Q5: What did Darwin learn about variations by observing breeders?
A5: breeders were able to select such variations and produce huge differences in many generations of selection
More detail was given in Darwin's 1868 book on The Variation of Animals and Plants under Domestication, which tried to explain heredity through his hypothesis of pangenesis. Although Darwin had privately questioned blending inheritance, he struggled with the theoretical difficulty that novel individual variations would tend to blend into a population. However, inherited variation could be seen, and Darwin's concept of selection working on a population with a range of small variations was workable. It was not until the modern evolutionary synthesis in the 1930s and 1940s that a model of heredity became completely integrated with a model of variation. This modern evolutionary synthesis had been dubbed Neo Darwinian Evolution because it encompasses Charles Darwin's theories of evolution with Gregor Mendel's theories of genetic inheritance.

Q1: When was The Variation of Animals and Plants under Domestication by Charles Darwin published?
A1: 1868
Q2: What was the hypothesis that attempted to explain heredity?
A2: hypothesis of pangenesis.
Q3: While Darwin wasn't sure about blending inherited traits, what was his opinion about utilizing inherited variation?
A3: Darwin's concept of selection working on a population with a range of small variations was workable
Q4: When did a model of heredity begin to be integrated with that of variation?
A4: in the 1930s and 1940s
Q5: What was the modern evolutionary synthesis named?
A5: Neo Darwinian Evolution
Chapter VI begins by saying the next three chapters will address possible objections to the theory, the first being that often no intermediate forms between closely related species are found, though the theory implies such forms must have existed. As Darwin noted, "Firstly, why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms? Why is not all nature in confusion, instead of the species being, as we see them, well defined?" Darwin attributed this to the competition between different forms, combined with the small number of individuals of intermediate forms, often leading to extinction of such forms. This difficulty can be referred to as the absence or rarity of transitional varieties in habitat space.

Q1: What is one possible objection to the theory of integrated variation?
A1: often no intermediate forms between closely related species are found
Q2: Why did Darwin wonder why all of nature isn't chaotic and random?
A2: why, if species have descended from other species by insensibly fine gradations, do we not everywhere see innumerable transitional forms?
Q3: What did Darwin ultimately decide was the reason that nature is not a chaos of variation?
A3: the competition between different forms, combined with the small number of individuals of intermediate forms, often leading to extinction of such forms.
His answer was that in many cases animals exist with intermediate structures that are functional. He presented flying squirrels, and flying lemurs as examples of how bats might have evolved from non-flying ancestors. He discussed various simple eyes found in invertebrates, starting with nothing more than an optic nerve coated with pigment, as examples of how the vertebrate eye could have evolved. Darwin concludes: "If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case."

Q1: What are some flying animals that Darwin thought might have evolved from bats?
A1: flying squirrels, and flying lemurs
Q2: What example did Darwin give of eyes evolving?
A2: simple eyes found in invertebrates, starting with nothing more than an optic nerve coated with pigment
Q3: How did Darwin justify his theory not breaking down?
A3: any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.
Chapter VII (of the first edition) addresses the evolution of instincts. His examples included two he had investigated experimentally: slave-making ants and the construction of hexagonal cells by honey bees. Darwin noted that some species of slave-making ants were more dependent on slaves than others, and he observed that many ant species will collect and store the pupae of other species as food. He thought it reasonable that species with an extreme dependency on slave workers had evolved in incremental steps. He suggested that bees that make hexagonal cells evolved in steps from bees that made round cells, under pressure from natural selection to economise wax. Darwin concluded:

Q1: How does Darwin theorize that instincts have evolved in slave-making ants?
A1: He thought it reasonable that species with an extreme dependency on slave workers had evolved in incremental steps.
Q2: How does Darwin theorize that instincts have evolved in bees?
A2: He suggested that bees that make hexagonal cells evolved in steps from bees that made round cells, under pressure from natural selection to economise wax
Q3: What did Darwin notice specifically about slave-making ants?
A3: some species of slave-making ants were more dependent on slaves than others
Chapter VIII addresses the idea that species had special characteristics that prevented hybrids from being fertile in order to preserve separately created species. Darwin said that, far from being constant, the difficulty in producing hybrids of related species, and the viability and fertility of the hybrids, varied greatly, especially among plants. Sometimes what were widely considered to be separate species produced fertile hybrid offspring freely, and in other cases what were considered to be mere varieties of the same species could only be crossed with difficulty. Darwin concluded: "Finally, then, the facts briefly given in this chapter do not seem to me opposed to, but even rather to support the view, that there is no fundamental distinction between species and varieties."

Q1: Why would hybrids have characteristics that keep them from being fertile?
A1: in order to preserve separately created species
Q2: What are Darwin's thoughts on producing hybrids of related species?
A2: the viability and fertility of the hybrids, varied greatly, especially among plants
Q3: What conclusion did Darwin come to after realizing that some diverse species were able to create variations easily, while other species thought to be closely related had difficulty?
A3: support the view, that there is no fundamental distinction between species and varieties
In the sixth edition Darwin inserted a new chapter VII (renumbering the subsequent chapters) to respond to criticisms of earlier editions, including the objection that many features of organisms were not adaptive and could not have been produced by natural selection. He said some such features could have been by-products of adaptive changes to other features, and that often features seemed non-adaptive because their function was unknown, as shown by his book on Fertilisation of Orchids that explained how their elaborate structures facilitated pollination by insects. Much of the chapter responds to George Jackson Mivart's criticisms, including his claim that features such as baleen filters in whales, flatfish with both eyes on one side and the camouflage of stick insects could not have evolved through natural selection because intermediate stages would not have been adaptive. Darwin proposed scenarios for the incremental evolution of each feature.

Q1: Why did Darwin introduce a new chapter in On the Origin of Species in the sixth edition?
A1: to respond to criticisms of earlier editions
Q2: What was one of the objections that Darwin addressed in his new chapter in On the Origin of Species?
A2: that many features of organisms were not adaptive and could not have been produced by natural selection
Q3: Which of Darwin's books featured a plant whose elaborate structure aided with fertilization by insects?
A3: Fertilisation of Orchids
Q4: Which scientist was addressed the most often in the new chapter of On the Origin of Species?
A4: George Jackson Mivart
Q5: What was Darwin's response to the claims that certain animals could not have evolved through natural selection?
A5: Darwin proposed scenarios for the incremental evolution of each feature.
Chapter IX deals with the fact that the geologic record appears to show forms of life suddenly arising, without the innumerable transitional fossils expected from gradual changes. Darwin borrowed Charles Lyell's argument in Principles of Geology that the record is extremely imperfect as fossilisation is a very rare occurrence, spread over vast periods of time; since few areas had been geologically explored, there could only be fragmentary knowledge of geological formations, and fossil collections were very poor. Evolved local varieties which migrated into a wider area would seem to be the sudden appearance of a new species. Darwin did not expect to be able to reconstruct evolutionary history, but continuing discoveries gave him well founded hope that new finds would occasionally reveal transitional forms. To show that there had been enough time for natural selection to work slowly, he again cited Principles of Geology and other observations based on sedimentation and erosion, including an estimate that erosion of The Weald had taken 300 million years. The initial appearance of entire groups of well developed organisms in the oldest fossil-bearing layers, now known as the Cambrian explosion, posed a problem. Darwin had no doubt that earlier seas had swarmed with living creatures, but stated that he had no satisfactory explanation for the lack of fossils. Fossil evidence of pre-Cambrian life has since been found, extending the history of life back for billions of years.

Q1: Whose argument did Darwin borrow that geological record is very imperfect, because fossilization is rare?
A1: Charles Lyell
Q2: Which book written by Charles Lyell contains the argument that fossils are too rare to be used as proof of life suddenly arising?
A2: Principles of Geology
Q3: What did Darwin hope to find as he continued to explore new geologic discoveries?
A3: that new finds would occasionally reveal transitional forms
Q4: How long did Darwin estimate the erosion of the Weald to be?
A4: 300 million years
Q5: What is the name of the group of well-developed organisms that were discovered within fossil-bearing layers?
A5: the Cambrian explosion
Chapter X examines whether patterns in the fossil record are better explained by common descent and branching evolution through natural selection, than by the individual creation of fixed species. Darwin expected species to change slowly, but not at the same rate – some organisms such as Lingula were unchanged since the earliest fossils. The pace of natural selection would depend on variability and change in the environment. This distanced his theory from Lamarckian laws of inevitable progress. It has been argued that this anticipated the punctuated equilibrium hypothesis, but other scholars have preferred to emphasise Darwin's commitment to gradualism. He cited Richard Owen's findings that the earliest members of a class were a few simple and generalised species with characteristics intermediate between modern forms, and were followed by increasingly diverse and specialised forms, matching the branching of common descent from an ancestor. Patterns of extinction matched his theory, with related groups of species having a continued existence until extinction, then not reappearing. Recently extinct species were more similar to living species than those from earlier eras, and as he had seen in South America, and William Clift had shown in Australia, fossils from recent geological periods resembled species still living in the same area.

Q1: How did Darwin expect species to change and evolve?
A1: slowly, but not at the same rate
Q2: What did Darwin believe were the key things needed for variation of species to form?
A2: variability and change in the environment
Q3: Which scientist theorized that the earliest members of a class in a species were simple and generalized?
A3: Richard Owen
Q4: What did Darwin discover about more recently extinct species?
A4: Recently extinct species were more similar to living species than those from earlier eras
Chapter XI deals with evidence from biogeography, starting with the observation that differences in flora and fauna from separate regions cannot be explained by environmental differences alone; South America, Africa, and Australia all have regions with similar climates at similar latitudes, but those regions have very different plants and animals. The species found in one area of a continent are more closely allied with species found in other regions of that same continent than to species found on other continents. Darwin noted that barriers to migration played an important role in the differences between the species of different regions. The coastal sea life of the Atlantic and Pacific sides of Central America had almost no species in common even though the Isthmus of Panama was only a few miles wide. His explanation was a combination of migration and descent with modification. He went on to say: "On this principle of inheritance with modification, we can understand how it is that sections of genera, whole genera, and even families are confined to the same areas, as is so commonly and notoriously the case." Darwin explained how a volcanic island formed a few hundred miles from a continent might be colonised by a few species from that continent. These species would become modified over time, but would still be related to species found on the continent, and Darwin observed that this was a common pattern. Darwin discussed ways that species could be dispersed across oceans to colonise islands, many of which he had investigated experimentally.

Q1: Why couldn't differences in flora and fauna be explained by differences in regions alone?
A1: South America, Africa, and Australia all have regions with similar climates at similar latitudes, but those regions have very different plants and animals
Q2: What did Darwin consider that could explain why different regions could have such different species when they are close together?
A2: barriers to migration played an important role in the differences between the species of different regions.
Q3: What was the combination of effects that Darwin considered the most important in determining the differences in species that evolved separately in similar environments?
A3: His explanation was a combination of migration and descent with modification.
Darwin discusses morphology, including the importance of homologous structures. He says, "What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include the same bones, in the same relative positions?" He notes that animals of the same class often have extremely similar embryos. Darwin discusses rudimentary organs, such as the wings of flightless birds and the rudiments of pelvis and leg bones found in some snakes. He remarks that some rudimentary organs, such as teeth in baleen whales, are found only in embryonic stages.

Q1: What theory does Darwin discuss that is related to the importance of homologous structures?
A1: morphology
Q2: What are some examples that Darwin gives of species whose basic form of limbs is similar, but who have vastly different uses for them?
A2: the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat
Q3: What does Darwin note about the embryos of many different species in the same class?
A3: animals of the same class often have extremely similar embryos
Q4: What are some examples of rudimentary organs that Darwin discusses in the chapter?
A4: e wings of flightless birds and the rudiments of pelvis and leg bones found in some snakes
The final chapter reviews points from earlier chapters, and Darwin concludes by hoping that his theory might produce revolutionary changes in many fields of natural history. Although he avoids the controversial topic of human origins in the rest of the book so as not to prejudice readers against his theory, here he ventures a cautious hint that psychology would be put on a new foundation and that "Light will be thrown on the origin of man". Darwin ends with a passage that became well known and much quoted:

Q1: What hopes does Darwin have for his theory in the natural history fields?
A1: that his theory might produce revolutionary changes
Q2: Why did Darwin avoid the topic of the origins of humans in most of his book?
A2: so as not to prejudice readers against his theory
Q3: What does Darwin allude to hoping in the final chapter of On the Origin of Species about humans?
A3: that psychology would be put on a new foundation and that "Light will be thrown on the origin of man"
Darwin's aims were twofold: to show that species had not been separately created, and to show that natural selection had been the chief agent of change. He knew that his readers were already familiar with the concept of transmutation of species from Vestiges, and his introduction ridicules that work as failing to provide a viable mechanism. Therefore, the first four chapters lay out his case that selection in nature, caused by the struggle for existence, is analogous to the selection of variations under domestication, and that the accumulation of adaptive variations provides a scientifically testable mechanism for evolutionary speciation.

Q1: What were Darwin's two important aims about evolution?
A1: to show that species had not been separately created, and to show that natural selection had been the chief agent of change
Q2: What did heknow his readers were already familiar with from Vestiges?
A2: the concept of transmutation of species
Q3: How did Darwin view Vestiges in the introduction to On the Origin of Species?
A3: his introduction ridicules that work as failing to provide a viable mechanism.
Q4: What is Darwin's belief about the accumulation of adaptive variations?
A4: the accumulation of adaptive variations provides a scientifically testable mechanism for evolutionary speciation.
Later chapters provide evidence that evolution has occurred, supporting the idea of branching, adaptive evolution without directly proving that selection is the mechanism. Darwin presents supporting facts drawn from many disciplines, showing that his theory could explain a myriad of observations from many fields of natural history that were inexplicable under the alternate concept that species had been individually created. The structure of Darwin's argument showed the influence of John Herschel, whose philosophy of science maintained that a mechanism could be called a vera causa (true cause) if three things could be demonstrated: its existence in nature, its ability to produce the effects of interest, and its ability to explain a wide range of observations.

Q1: What does Darwin do to show that his theory can support many theories that could not be explained by individual creation of species?
A1: Darwin presents supporting facts drawn from many disciplines
Q2: Whose scientific philosophy argued that a mechanism could be called a vera causa if three things could be shown as true?
A2: John Herschel
Q3: What are the three things John Herschel maintains need to be shown to allow for a mechanism be called a true cause?
A3: its existence in nature, its ability to produce the effects of interest, and its ability to explain a wide range of observations