2. Comment on the ways of studying the evolutionary mechanisms using the table from ex. 1.

3. Give definitions of the following:

fossils, paleontologist, comparative anatomy, embryology, island biogeography.

4. Work in pairs. Make up all possible questions to the sentences and answer them.

1. Later species evolved progressively more humanlike features.

2. Information about evolutionary processes is also obtained by direct observation of species.

3. Bacteria may retain their resistance to antibiotics over many generations.

4. This calculation has provided new knowledge of the evolutionary relationship between modern apes and modern humans.

5. Other theories regarding the origin of life on Earth point to outer space.

5. Say what you have learnt about:

• determining the age of a fossil;

• influence of species distribution on evolutionary relationship;

• embryos of organisms that share a recent common ancestor;

• PNA structure;

• molecular clock concept;

• fruit fly as one of the most powerful tools in the study of evolutionary mechanisms;

• ribonucleic acid;

• theories about life's origin.

Unit 7 Development of Evolutionary Theory Word Study

1. Learn the meaning of the words:

dawn	рассвет	to anchor off	бросить якорь
to highlight	проливать свет	to deprive	лишать
to credit	зд. считаться	clergy	духовенство
attribute	свойство	random	случайный
to embrace	принимать	breeding	скрещивание
invertebrates	беспозвоночные	hinge	зависеть от
to acquire	приобретать	precise	точный
to squabble	вздорить	ultimately	в конечном итоге
to maintain	утверждать	abrupt	внезапный

2. Practice the following for pronunciation:

civilization	colleagues
the Renaissance	dominant
taxonomy	recessive
theorize	myth
biblical mechanism

3. Translate the word combinations into Russian and use them in the sentences of your own:

to be at a standstill static hierarchy of levels of perfection to be incapable of meeting the challenges of nature to meet the demands to embrace the idea marine invertebrates

to transmit the alterations to unearth the fossils long-extinct life competition for limited resources round-the-world mapmaking voyage to fall out of favor

Text a Development of Evolutionary Theory I

The origins of life on Earth have been a source of speculation among philosophers, religious thinkers, and scientists for thousands of years. Many human civilizations used rich and complex creation stories and myths to explain the presence of living organisms. Ancient Greek philosophers and scientists were among the earliest to apply the principles of modern science to the mysterious complexity and variety of life around them. During early Christian times, ancient Greek ideas gave way to Creationism, the view that a single God created the universe, the world, and all life on Earth. For the next 1,500 years, evolutionary science was at a standstill. The dawn of the Renaissance in the early 14th century brought a renewed interest in science and medicine. Advances in anatomy highlighted physical similarities in the features of widely different organisms. Fossils provided evidence that life on this planet was vastly different millions of years ago. With each new development came new ideas and theories about the nature of life.

The Greek philosopher Anaximander, who lived in the 500s B. C., is generally credited as the earliest evolutionist. Anaximander believed that the Earth first existed in a liquid state. Further, he believed that humans evolved from fishlike aquatic beings who left the water once they had developed sufficiently to survive on land. Greek scientist Empedocles speculated in the 400s B. C. that plant life arose first on Earth, followed by animals. Empedocles proposed that humans and animals arose not as complete individuals but as various body parts that joined together randomly to form strange, fantastic creatures. Some of these creatures, being unable to reproduce, became extinct, while others thrived. Outlandish as his ideas seem today, Empedocles' thinking anticipates the fundamental principles of natural selection.

The Greek philosopher and scientist Aristotle, who lived in the 300s B. C., referred to a "ladder of nature" – a progression of life forms from lower to higher – but his ladder was a static hierarchy of levels of perfection, not an evolutionary concept. Each rung on this ladder was occupied by organisms of higher complexity than the rung before it, with humans occupying the top rung. Aristotle acknowledged that some organisms are incapable of meeting the challenges of nature and so cease to exist. As he saw it, successful creatures possessed a gift, or perfecting principle, that enabled them to rise to meet the demands of their world. Creatures without the perfecting principle died out. In Aristotle's view it was this principle – not evolution – that accounted for the progression of forms in nature.

Many centuries later, the idea of a perfect and unchanging natural world – the product of divine creation – was predominant not only in religion and philosophy, but in science. Gradually, however, as knowledge accumulated from seemingly disparate areas, the beginnings of modern evolutionary theory began to take shape. A key figure in this regard was the Swedish naturalist Carolus Linnaeus, who became known as the father of modern taxonomy, the science of classifying organisms.

In his major work "Systema Naturae" (The System of Nature), first published in 1735, Linnaeus devised a system of classification of organisms that is still in use today. This system places living things within increasingly specific categories based on common attributes – from a general grouping (kingdom) down to the specific individual (species). Using this system, Linnaeus named nearly 10,000 plant and animal species in his lifetime. Not an evolutionist by any means, Linnaeus believed that each species was created by God and was incapable of change. Nevertheless, his orderly groupings of living things provided important insights for later theorists.

Perhaps the most prominent of those who embraced the idea of progressive change in the living world was the early 19th-century French biologist Jean-Baptista Lamarck. Lamarck's theory, now known as Lamarckism and based in part on his study of the fossils of marine invertebrates, was that species do change over time. He believed, furthermore, that animals evolve because unfavorable conditions produce needs that animals try to satisfy. For example, short-necked ancestors of the modern giraffe voluntarily stretched their necks to reach leaves high in trees during times when food was scarce. Proponents of Lamarckism thought this voluntary use slightly changed the hereditary characteristics controlling neck growth; the giraffe then transmitted these alterations to its offspring as what Lamarck called acquired characteristics. Modern scientists know that adaptation and natural selection are far more complicated than Lamarck supposed, having nothing to do with an animal's voluntary efforts. Nevertheless, the idea of acquired characteristics, with Lamarck as its most famous proponent, persisted for many years.

French naturalist and paleontologist Georges Cuvier feuded with Lamarck. Unearthing the fossils of mastodons and other vanished species, Cuvier produced proof of long-extinct life forms on Earth. Unlike Lamarck, however, Cuvier did not believe in evolution. Instead, Cuvier believed that floods and other cataclysms destroyed such ancient species. He suggested that after each cataclysmic event, God created a new set of organisms.

At around the same time that Cuvier and Lamarck were squabbling, British economist Thomas Robert Malthus proposed ideas extremely influential in evolutionary theory. In his 1798 work An Essay on the Principle of Population, Malthus theorized that the human population would increase at a much greater rate than its food sources. This theory introduced the key idea of competition for limited resources – that is, there is not enough food, water, and living space to go around, and organisms must somehow compete with each other to obtain resources necessary for survival. Another key idea came from Scottish geologist Charles Lyell, who supplied a deeper understanding of Earth's history. In his book Principles of Geology (1830), Lyell set forth his case that the Earth was millions of years old rather than only a few thousand years old, as was maintained by those who accepted the biblical story of divine creation as fact.

In 1831, Charles Darwin, who was intending to become a country minister, had an opportunity to sail as ship's naturalist aboard the HMS Beagle on a five-year, round-the-world mapmaking voyage. During the journey, as the ship anchored off South America and other distant shores, Darwin had the opportunity to travel inland and make observations of the natural world. In the Galapagos Islands, he noted how species on the various islands were similar but distinct from one another. He also observed fossils and other geological evidence of the Earth's great age. The observations Darwin made on that voyage seemed to suggest the evolution, rather than the creation, of the many local forms of life.

In 1837, shortly after returning to England, Darwin began a notebook of his observations and thoughts on evolution. Although Darwin had developed the major components of his theory of evolution by natural selection in an 1842 unpublished paper circulated among his friends, he was unwilling to publish the results until he could present as complete a case as possible. He labored for almost 20 additional years on his theory of evolution and on its primary mechanism, natural selection. In 1858 he received a letter from British naturalist Alfred Russell Wallace, a professional collector of wildlife specimens. Much to Darwin's surprise, Wallace had independently hit upon the idea of natural selection to explain how species are modified by adapting to different conditions. Not wanting Darwin to be unfairly deprived of his share of the credit for the theory, some of Darwin's scientific colleagues presented extracts of Darwin's work along with Wallace's paper at a meeting of the Linnaean Society, a London-based science organization, in June 1858. Wallace's paper stimulated Darwin to finish his work and get it into print. Darwin published "On the Origin of Species by Means of Natural Selection" on November 24, 1859. All 1,250 copies of the first printing were sold on that day.

Darwin's book and the theory it popularized – evolution through natural selection – set off a storm of controversy. Some of the protest came from the clergy and other religious thinkers. Other objections came from scientists. Many scientists continued to believe in Lamarckism, the idea that living things could consciously strive to accumulate modifications during a lifetime and could pass these traits on to their offspring. Other scientists objected to the seemingly random quality of natural selection. If natural selection depended upon random combinations of traits and variations, critics asked, how could it account for such refined and complex structures as the human eye? Perhaps the most serious question – one for which Wallace and Darwin had no answer – concerned the inheritance of traits. How exactly were traits passed along to offspring?

Darwin did not know it, but the answer was at hand – although it would not be acknowledged in his lifetime. In the Augustinian monastery at Brünn (now Brno in the Czech Republic), Austrian monk Gregor Mendel experimented with the breeding of garden peas, observing how their traits were passed down through generations. In crossbreeding pea plants to produce different combinations of traits – color, height, smoothness, and other characteristics – Mendel noted that although a given trait might not appear in every generation, the trait did not disappear. Mendel discovered that the expression of traits hinged on whether the traits were dominant or recessive, and on how these dominant and recessive traits combined. He learned that contrary to what most scientists believed at the time, the mixing of traits in sexual reproduction did not result in a random blending. Traits were passed along in discrete units. These units are now known as genes. Mendel performed hundreds of experiments and produced precise statistical models and principles of heredity, now known as Mendel's Laws, showing how dominant and recessive traits are expressed over generations. However, no one appreciated the significance of Mendel's work until after his death. But his work ultimately gave birth to the modern field of genetics.

In 1900, the Dutch botanist Hugo Marie de Vries and others independently discovered Mendel's laws. The following year, de Vries's book "The Mutation Theory" challenged Darwin's concept of gradual changes over long periods by proposing that evolution occurred in abrupt, radical steps. Having observed new varieties of the evening primrose plant coming into existence in a single generation, de Vries had subsequently determined that sudden change, or mutation, in the genetic material was responsible. As the debate over evolution continued in the early 20th century, some scientists came to believe that mutation, and not natural selection, was the driving force in evolution. In the face of these mutationists, Darwin's central theory threatened to fall out of favor.