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Exercise 5. Give detailed answers to the following questions using the information from the text:

1. Why do birds migrate?

2. What adaptations allow birds to accomplish their migrations? Describe each in detail.

3. How are migratory birds different from non-migratory species?

4. How do birds prepare for the hardships of migration?

5. What is Zugunruhe?

Exercise 6. In the following text the paragraphs are mixed. Put them in the correct logical order. The first paragraph is in its right place.

How do deep-diving sea creatures withstand huge pressure changes?

Paul J. Ponganis and Gerald L. Kooyman of the Center for Marine Biotechnology and Biomedicine at Scripps Institution of Oceanography provide the following answer.

A sperm whale can dive down more than 2,000 meters and can stay submerged for up to an hour.

(A) Some sea creatures exploit great depths. The biggest physiological challenges in adapting to pressure are probably faced by those animals that must routinely travel from the surface to great depth. Two such animals are the sperm whale and the bottlenose whale. From the days of whaling, these animals have been recognized as exceptional divers, with reports of dives lasting as long as two hours after they were harpooned. Today, with the use of sonar tracking and attached time-depth recorders, dives as deep as 6,000 feet (more than a mile below the surface of the ocean) have been measured. Routine dive depths are usually in the 1,500- to 3,000-foot range, and dives can last between 20 minutes and an hour.

(B) Loss of gas exchange at depth has another important implication: the lungs of the deep diver cannot serve as a source of oxygen during the dive. Instead deep-diving whales and seals rely on large oxygen stores in their blood and muscle. Several adaptations enable this. First, these animals have mass specific blood volumes that are three to four times those found in terrestrial mammals (i.e., 200 to 250 milliliters of blood per kilogram body mass, in contrast to a human value of 70 milliliters blood per kilogram). Second, the concentration of hemoglobin (the oxygen-transport protein in blood) is also elevated to a level about twice that found in humans. Third, the concentration of myoglobin, the oxygen storage protein in muscle, is extremely elevated in these animals, measuring about 10 times that in human muscle.

(C) In summary, the primary anatomical adaptations for pressure of a deep-diving mammal such as the sperm whale center on air-containing spaces and the prevention of tissue barotrauma. Air cavities, when present, are lined with venous plexuses, which are thought to fill at depth, obliterate the air space, and prevent "the squeeze." The lungs collapse, which prevents lung rupture and (important with regard to physiology) blocks gas exchange in the lung. Lack of nitrogen absorption at depth prevents the development of nitrogen narcosis and decompression sickness. In addition, because the lungs do not serve as a source of oxygen at depth, deep divers rely on enhanced oxygen stores in their blood and muscle.

(D) Diving to depth can result in mechanical distortion and tissue compression, especially in gas-filled spaces in the body. Such spaces include the middle ear cavity, air sinuses in the head, and the lungs. Development of even small pressure differentials between an air cavity and its surrounding tissue can result in tissue distortion and disruption—a condition in human divers known as "the squeeze." In some species of cetaceans, the middle ear cavity is lined with an extensive venous plexus, which is postulated to become engorged at depth and thus reduce or obliterate the air space and prevent development of the squeeze. Cetaceans also have large Eustachian tubes communicating with the tympanic cavity of the ear and the large pterygoid sinuses of the head. These air sinuses of the head have an extensive vasculature, which is thought to function in a manner similar to that of the middle ear and facilitate equilibration of air pressure within these spaces. Lastly, most marine mammals lack frontal cranial sinuses like those present in terrestrial mammals.

(E) Collapse of the lungs forces air away from the alveoli, where gas exchange between the lungs and blood occurs. This blunting of gas exchange is important in the deep diver because it prevents the absorption of nitrogen into the blood and the subsequent development of high blood nitrogen levels. High blood nitrogen pressures can exert a narcotic effect (so-called nitrogen narcosis) on the diver. It may also lead to nitrogen bubble formation during ascent—a phenomenon known as decompression sickness or "the bends." Collapse of the lungs in the deep diver avoids these two problems.

(F) Another organ susceptible to compression damage is the lung. In deep-diving whales and seals, the peripheral airways are reinforced, and it is postulated that this allows the lungs to collapse during travel to depth. Such collapse has been observed radiographically and confirmed with blood nitrogen analyses in the deep-diving Weddell seal.

Exercise 7. Make up a list of the 10 key terms used in the text, then agree with the whole group on the final list. Retell the article using these terms.

Exercise 8. Prepare your own report about adaptations of other species to their habitat and lifestyle.

Section 2. Recommended Report and Presentation Topics

1. Mental disorders.

2. Brain regions and their functions.

3. What exactly are dreams?

4. Dreams and nightmares.

5. Early bird or night owl?

6. Coffee – friend or foe? Health effects of coffee.

7. Decaffeinated coffee.

8. Tea or coffee?

9. Eugenics.

10. Gene therapy.

11. GM plants.

12. GM animals.

13. Engineered animals and natural populations.

14. Animal conservation.

15. Ecotourism.

Section 3.

Unit 11. Human Evolution

The species does not grow into perfection: the weak again and again get the upper hand of the strong,—their large number, and their greater cunning are the cause of it.

Friedrich Nietzsche

Exercise 1. What is evolution?

1. Why is Africa considered the birthplace of Homo sapiens?

2. What is the difference between monocentrism and polycentrism?

3. What caused bipedalism (bipedal locomotion) and upright posture in humans?

4. Why do people living in the south tend to have dark skin colour, while people living in the north have fair complexion?

5. How did human races originate?

6. What factors can speed up evolution?

Exercise 2. Explain the meaning of the following key terms connected with evolution:

Exercise 3. Now read the article to check some of your answers in Exercise 1.

Culture Speeds Up Human Evolution

Analysis of common patterns of genetic variation reveals that humans have been evolving faster in recent history

By David Biello

Homo sapiens sapiens has spread across the globe and increased vastly in numbers over the past 50,000 years or so—from an estimated five million in 9000 B.C. to roughly 6.5 billion today. More people means more opportunity for mutations to creep into the basic human genome and new research confirms that in the past 10,000 years a host of changes to everything from digestion to bones has been taking place.

"We found very many human genes undergoing selection," says anthropologist Gregory Cochran of the University of Utah, a member of the team that analyzed the 3.9 million DNA sequences* showing the most variation. "Most are very recent, so much so that the rate of human evolution over the past few thousand years is far greater than it has been over the past few million years." "We believe that this can be explained by an increase in the strength of selection as people became agriculturalists—a major ecological change—and a vast increase in the number of favorable mutations as agriculture led to increased population size," he adds.

Roughly 10,000 years ago, humanity made the transition from living off the land to actively raising crops and domesticated animals. Because this concentrated populations, diseases such as malaria, smallpox and tuberculosis, among others, became more virulent. At the same time, the new agriculturally based diet offered its own challenges—including iron deficiency from lack of meat, cavities and, ultimately, shorter stature due to poor nutrition, says anthropologist John Hawks of the University of Wisconsin–Madison, another team member. "Their bodies and teeth shrank. Their brains shrank, too," he adds. "But they started to get new alleles that helped them digest the food more efficiently. New protective alleles allowed a fraction of people to survive the dread illnesses better."

By looking for wide swaths of genetic material that vary little from individual to individual within these sections of great variation, the researchers identified regions that both originated recently and conferred some kind of advantage (because they became common rapidly). For example, the gene known as LCT gave adults the ability to digest milk and G6PD offered some protection against the malaria caused by Plasmodium falciparum parasite. "Ten thousand years ago, no one on planet Earth had blue eyes," Hawks notes, because that gene—OCA2—had not yet developed. "We are different from people who lived only 400 generations ago in ways that are very obvious; that you can see with your eyes."

Comparing the amount of genetic differentiation between humans and our closest relatives, chimpanzees, suggests that the pace of change has accelerated to 10 to 100 times the average long-term rate, the researchers write in Proceedings of the National Academy of Sciences USA. Not all populations show the same evolutionary speed. For example, Africans show a slightly lower mutation rate. "Africans haven't had to adapt to a fundamentally new climate," because modern humanity evolved where they live, Cochran says. "Europeans and East Asians, living in environments very different from those of their African ancestors and early adopters of agriculture, were more maladapted, less fitted to their environments."

And this speedy pace of evolution will not slow until every possible beneficial mutation starts to happen—the maximum rate of adaptation. This has already begun to occur in such areas as skin color in which different sets of genes are responsible for the paler shades of Europeans and East Asians, according to the researchers.

The finding raises many questions. Among them: "the medical applications of this kind of knowledge [as well as] exactly what most of the selected changes do and what drove their selection," Cochran says.

But the history of humanity is beginning to be read out from our genes, thanks to a detailed knowledge of the thousands of them that have evolved recently. "We're going to be classifying these by functional categories and looking for matches between genetic changes and historic and archaeological changes in diet, skeletal form, disease and many other things," Hawks says. "We think we will be able to find some of the genetic changes that drove human population growth and migrations—the broad causes of human history." (From Scientific American Online, December 10, 2007)

*This article wrongly characterized the HapMap genotype dataset used for this analysis as "genes" rather than "DNA sequences."

Exercise 4. Are the following statements true or false, according to the text? Explain your answer.

1. Homo Sapiens has demonstrated great biological progress over its history.

2. The rate of human evolution has slowed down due to vast numbers of people living.

3. Transition to agricultural lifestyle and domestication of animals provided a reliable source of food for people.

4. It also helped to improve human health condition.

5. Different populations demonstrate different rates of evolutionary changes.

6. Humans have developed numerous adaptations and thus have achieved the maximum rate of adaptation.

7. Genetic research sheds light on human evolution.

Exercise 5. Are humans still evolving? Discuss the following questions:

1. What changes have taken place since the emergence of Homo Sapiens? Give as many examples as you can.

2. What adaptations to their environment and lifestyle have people developed?

Exercise 6. Read the text which provides some information about the changes of human phenotype.

Why are we getting taller as a species?

Humans increased in stature dramatically during the last 150 years, but we have now likely reached the upper limit. The average height of a human man will probably never exceed that of basketball player Shaquille O'Neal, who stands 7 feet and 1 inch tall.

This answer comes from Michael J. Dougherty, assistant director and senior staff biologist at Biologic Image: SportsLine USA, Inc.

In fact, over the last 150 years the average height of people in industrialized nations has increased approximately 10 centimeters (about four inches). Why this relatively sudden growth? Are we evolving to greater heights? Before answering these questions, we need to remember that evolution requires two things: variation in physical and/or behavioral traits among the individuals in a population; and a way of selecting some of those traits as adaptations, or advantages to reproduction.

For example, finches that have large, powerful beaks also have an advantage cracking large, tough seeds during periods when small, soft seeds are scarce. As a consequence, large-beaked birds are more likely to eat better, survive longer and reproduce than small-beaked birds. Because beak shape is an inherited trait, more successful reproduction by large beaked birds means that the genes predisposing finches to large beaks are transmitted to the next generation in relatively larger numbers than those genes encoding small beaks. Thus, the population of finches in the next generation will tend to have larger beaks than finches in their parent's generation.

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