READING PASSAGE 2

You should spend about 20 minutes on Questions 14-26, which are based on Reading Passage 2 below.

The return of monkey life

Rain forest trees growing anew on Central American farmland are helping scientists find ways for monkey and agriculture to benefit one another.

A.    Hacienda La Pacifica, a remote working cattle ranch in Guanacaste province of northern Costa Rica, has for decades been home to a community of mantled howler monkeys. Other native primates- white-faced capuchin monkeys and spider monkeys were once common in this area, too, but vanished after the Pan-American Highway was built nearby in the 1950s and most of the surrounding land was cleared for cattle-raising. At Hacienda La Pacifica, however, an enlightened ranch owner chose to leave some strips of native trees growing. He used these as windbreaks to protect both cattle and their food crops from dry-season winds. In the process, the farmer unwittingly founded a unique laboratory for the study of monkeys.

B.   Ken Glander, a primatologist from Duke University in the USA, is studying La Pacifica’s monkeys in an effort to understand the relationship between howlers and regenerating forests at the edges of grazing lands. Studying such disturbed woodlands is increasingly important because throughout much of the New World Tropics, these are the only forests left. In the 18^th century, tropical dry forests once covered most of Central America, but by the 1980s less than two percent remained undisturbed, and less than one percent was protected.

C.     Howlers persists at La Pacifica, Glander explains, because they are leaf-eaters. They eat fruit when it is available but, unlike capuchin and spider monkeys, do not depend on large areas of fruiting trees. Glander is particularly interested in howlers’ ability to thrive on leaves loaded with toxins- poisonous substances designed to protect the plants. For leaf-eaters, long-term exposure to a specific plant toxin can increase their ability to neutralize the poisonous substances and absorb the leaf nutrients. Watching generations of howlers at La Pacifica has shown Glander that the monkeys keep their systems primed by sampling a variety of plants and then focusing on a small number of the most nutritious food items. The leaves that grow in regenerating forests, like those at La Pacifica, are actually more howler-friendly than those produced by the centuries-old trees that survive farther south. In younger forests, trees put most of their limited energy into growing wood, leaves, and fruit, so they produce much lower levels of toxin than do well-established, old-growth trees.

D.   The value of maturing forests to primates is also a subject of study at Santa Rosa National Park, about 35 miles northwest of La Pacifica. Large areas of Santa Rosa’s forests had at one time been burnt to make space for cattle ranching and coffee farming, thereby devastating local monkey habitat. But in 1971 the government protected the area by designating it a National Park, and species of Indigenous Lees which had been absent for decades began to invade the abandoned pastures. Capuchins were the first to begin using the reborn forests, followed by howlers. Eventually, even spider monkeys, fruit-eaters that need large areas of continuous forest, returned. In the first 28 years following protection of the area, the capuchin population doubled, while the number of howlers increased sevenfold.

E.    Some of the same traits that allow howlers to survive at La Pacifica also explain their population boom in Santa Rosa, Howler reproduction is faster than that of other native monkey species. They give birth for the first time at about 3.5 years of age, compared with seven years for capuchins, and eight or more for spider monkeys. Also, while a female spider monkey will have a baby about once every four years, well-fed howlers can produce an infant every two years. Another factor is diet. Howlers are very adaptable feeders, and only need a comparatively small home range. Spider monkeys, on the other hand, need to occupy a huge home range. Also crucial is fact that the leaves howlers eat hold plenty of water, so the monkeys can survive away from open streams and water holes. This ability gives them a real advantage over capuchin and spider monkeys, which have suffered during the long, ongoing drought in the area.

F.   Alejandro Estrada, an ecologist at Estacion de Biologia Los Tuxtlas in Veracruz, Mexico, has been studying the ecology of a group of howler monkeys that thrive in a habitat totally altered by humans: a cacao plantation in Tabasco state, Mexico. Cacao plants need shade to grow, so 40 years ago the owners of Cholula Cacao Farm planted figs, monkeypod and other tall trees to form a protective canopy over their crop. The howlers moved in about 25 years ago after nearby forests were cut. This strange habitat seems to support about as many monkeys as would a same-sized patch of wild forest. The howlers eat the leaves and fruit of the shade trees, leaving the valuable cacao pods alone.

G.   Estrada believes the monkeys bring underappreciated benefits to such plantations, dispersing the seeds of fruits such as fig and other shade trees, and fertilizing the soil. Spider monkeys also forage for fruit here, though they need nearby areas of forest to survive in the long term. He hopes that farmers will begin to see the advantages of associating with wild monkeys, which could include potential ecotourism projects, ‘Conservation is usually viewed as a conflict between farming practices and the need to preserve nature,’ Estrada says. ‘We’re moving away from that vision and beginning to consider ways in which commercial activities may become a tool for the conservation of primates in human-modified landscapes.’

READING PASSAGE 3

You should spend about 20 minutes on Questions 27-40, which are based on Reading Passage 3 below.

The value of research into mite harvestmen

Few people have heard of the mite harvestman, and fewer still would recognize it at close range. The insect is a relative of the far more familiar daddy longlegs. But its legs are stubby rather than long, and its body is only as big as a sesame seed. To find mite harvestmen, scientists go to dark, humid forests and sift through the leaf litter. The animals respond by turning motionless, making them impossible for even a trained eye to pick out.' They look like grains of dirt.' said Gonzalo Giribet, an invertebrate biologist at Harvard University

Dr Giribet and his colleagues have spent six years searching for mite harvestmen on five continents. The animals have an extraordinary story to tell they carry a record of hundreds of millions of years of geological history, chronicling the journeys that continents have made around the Earth. The Earth's landmasses have slowly collided and broken apart again several times, carrying animals and plants with them. These species have provided clues to the continents' paths.

The notion of continental drift originally came from such clues. In 1911, the German scientist Alfred Wegener was struck by the fact that fossils of similar animals and plants could be found on either side of the Atlantic. The ocean was too big for the species to have traveled across it on their own. Wegener speculated correctly, as it turned out that the surrounding continents had originally been welded together in a single landmass, which he called Pangea.

Continental drift, or plate tectonics as it is scientifically known, helped move species around the world. Armadillos and their relatives are found in South America and Africa today because their ancestors evolved when the continents were joined. When South America and North America connected a few million years ago, armadillos spread north, too. Biogeographers can learn clues about continental drift by comparing related species. However, they must also recognize cases where species have spread for other reasons, such as by crossing great stretches of water. The island of Hawaii, for example, was home to a giant flightless goose that has become extinct.

Studies on DNA extracted from its bones show that it evolved from the Canada goose. Having colonized Hawaii, it branched off from that species, losing its ability to fly. This evolution occurred half a million years ago, when geologists estimate that Hawaii emerged from the Pacific

When species jump around the planet, their histories blur. It is difficult to say much about where cockroaches evolved, for example, because they can move quickly from continent to continent.

This process, known as dispersal, limits many studies. 'Most of them tend to concentrate on particular parts of the world.' Dr Giribet said. I wanted to find a new system for studying biogeography on a global scale.

Dr Giribet realized that mite harvestmen might be that system. The 5,000 or so mite harvestmen species can be found on every continent except Antarctica. Unlike creatures found around the world like cockroaches, mite harvestmen cannot disperse well. The typical harvestman species has a range of fewer than 50 miles. Harvestmen are not found on young islands like Hawaii, as these types of islands emerged long after the break-up of Pangea.

According to Assistant Professor Sarah Boyer, a former student of Dr Giribet. 'It's really hard to find a group of species that is distributed all over the world but that also doesn't disperse very far.'

What mite harvestmen lack in mobility, they make up in age. Their ancestors were among the first land animals, and fossils of daddy longlegs have been found in 400 million-year-ago rocks.

Mite harvestmen evolved long before Pangea broke up and have been carried along by continental drift ever since they've managed to get themselves around the world only because they've been around for hundreds of millions of years, Dr Boyer said. Dr Boyer, Dr Giribet and their colleagues have gathered thousands of mite harvestmen from around the world, from which they extracted DNA. Variations in the genes helped the scientists build an evolutionary tree. By calculating how quickly the DNA mutated, the scientists could estimate when lineages branched off. They then compared the harvestmen's evolution to the movements of the continents. The patterns are remarkably clear.' Dr Boyer said.

The scientists found that they could trace mite harvestmen from their ancestors on Pangea. One lineage includes species in Chile South Africa, Sri Lanka and other places separated by thousands of miles of ocean. But 150 million years ago, all those sites were in Gondwana which was a region of Pangea.

The harvestmen preserve smaller patterns of continental drift, as well as bigger ones. After analyzing the DNA of a Florida harvestman, Metasiro americanus, the scientists were surprised to find that it was not related to other North American species. Its closest relatives live in West Africa. Dr Boyer then began investigating the geological history of Florida and found recent research to explain the mystery. Florida started out welded to West Africa near Senegal. North America than collied into them Pangea was forming. About 170 million years ago, North America ripped away from West Africa, taking Florida with it. The African ancestors of Florida's harvestmen came along the ride.

Dr Giribet now hopes to study dozens or even hundreds of species, to find clues about plate tectonics that a single animal could not show.