IELTSwithJurabek

PASSAGE 2

Read the text and answer questions 14-26

AUSTRALIAN PARROTS AND THEIR ADAPTATION TO HABITAT CHANGE

A. Parrots are found across the tropics and in all southern hemisphere continents except Antarctica, but nowhere do they display such a richness of diversity and form as in Australia. One-sixth of the world's 345 parrot species are found there, and Australia has long been renowned for the number and variety of its parrots.

B. In the 16th century, the German cartographer Mercator made a world map that included a place, somewhere near present-day Australia, that he named Terra Psittacorum - the Land of Parrots - and the first European settlers in Australia often referred to the country as Parrot Land. In 1865, the celebrated British naturalist and wildlife artist John Gould said: "No group of birds gives Australia so tropical and benign an air as the numerous species of this great family by which it is tenanted."

C. Parrots are descendants of an ancient line. Due to their great diversity, and since most species inhabit Africa, Australia and South America, it seems almost certain that parrots originated millions of years ago on the ancient southern continent of Gondwana, before it broke up into the separate southern hemisphere continents we know today. Much of Gondwana comprised vast rainforests intersected by huge slow-flowing rivers and expansive lakes, but by eight million years ago, great changes were underway. The centre of the continent of Australia had begun to dry out, and the rainforests that once covered it gradually contracted to the continental margins, where, to a limited extent, they still exist today.

D. The creatures that remained in those shrinking rainforests had to adapt to the drier conditions or face extinction. Reacting to these desperate circumstances, the parrot family, typically found in jungles in other parts of the world, has populated some of Australia's harshest environments. The parrots spread from ancestral forests through eucalypt woodlands to colonise the central deserts of Australia, and as a consequence they diversified into a wide range of species with adaptations that reflect the many changes animals and plants had to make to survive in these areas.

E. These evolutionary pressures helped mould keratin, the substance from which beaks are made, into a range of tools capable of gathering the new food types favoured by various species of parrot. The size of a parrot's short, blunt beak and the length of that beak's curved upper section are related to the type of food each species eats. Some have comparatively long beaks that are perfect for extracting seeds from fruit; others have broader and stronger beaks that are designed for cracking hard seeds.

F. Differently shaped beaks are not the only adaptations that have been made during the developing relationship between parrots and their food plants. Like all of Australia's many honey-eating birds, the rainbow-coloured lorikeets and the flowers on which they feed have long coevolved, with features such as the shape and colour of the flowers adapted to the bird's particular needs. For example, red is the most attractive colour to birds, and thus flowers which depend on birds for pollination are more often red, and lorikeets have tongues with bristles which help them to collect as much pollen as possible.

G. Today, most of Australia's parrots inhabit woodland and open forest, and their numbers decline towards both deserts and wetter areas. The majority are nomadic to some degree, moving around to take advantage of feeding and breeding places. Two of the dry country parrots, the pink and grey galah and the pink, white and yellow corella, have expanded their ranges in recent years. They are among the species that have adapted well to the changes brought about by European settlement: forest felling created grasslands where galahs and corellas thrive.

H. But other parrot species did not fare so well when their environments were altered. The clearing of large areas of rainforest is probably responsible for the disappearance of the double-eyed fig parrot, and numbers of ground parrots declined when a great part of their habitat was destroyed by the draining of coastal swamps. Even some parrot species that benefited from forest clearing at first are now confronted by a shortage of nesting sites due to further man-made changes.

I. New conditions also sometimes favour an incoming species over one that originally inhabited the area. For example, after farmers cleared large areas of forest on Kangaroo Island off the coast of South Australia, the island was colonised by galahs. They were soon going down holes and destroying black cockatoo eggs in order to take the hole for their own use. Their success precipitated a partial collapse in the black cockatoo population when the latter lost the struggle for scarce nesting hollows.

J. There may be no final answer to ensuring an equitable balance between parrot species. Nest box programmes help ease the shortage of nesting sites in some places, but there are not enough, they are expensive and they are not an adequate substitute for large, old trees, such as the habitat they represent and the nectar, pollen and seeds they provide. Competition between parrots for nest sites is a result of the changes we humans have made to the Earth. We are the most widespread and dangerous competitors that parrots have ever had to face, but we also have the knowledge and skill to maintain the wonderfully rich diversity of Australia's parrots. All we need is the will to do so.

PASSAGE 3

Read the text and answer questions 27-40

WHALE CULTURE

A. Most social scientists stubbornly resist the idea that animals have culture. Even such advanced cetacean mammals as whales and dolphins clearly do not have art, literature, or architecture. But patient observation over many years has begun to reveal behaviours that can only have been learnt from other whales. And that, say whale biologists, constitutes culture.

B. So far, humpback and killer whales provide the best evidence of culture in cetaceans, and the song of the male humpback is among the most striking examples. Humpback populations in different oceans sing different songs, but within the same ocean they all stick to the same one. However, during the breeding season the sounds change, as it appears that females are drawn to novel songs. One male might add an extra set of groans; another might drop a series of grunts. Soon all the other males have altered their own rendition to incorporate the changes until they are once again singing the same song. Since this occurs among thousands of whales spread across a vast part of the planet, the change cannot be in response to any factor in the animals' environment. The latest version of the song can be learnt only from other whales - almost certainly by imitation.

C. Culture plays an even bigger part in the life of killer whales. Nowhere is this more obvious than along the north-west coast of America, where killer whales are split into two distinct populations - residents and transients. They live in the same stretch of water, but they do not mingle. In effect, they belong to two quite separate cultures. Residents live in stable groups, or pods, made up of two or three mothers and their offspring - perhaps 20 whales in all. Calves stay with their mothers throughout adulthood, and in many years of observation no one has ever seen a whale switch pods. Transients travel in smaller, more changeable groups of between three and six.

D. One of the most obvious distinctions between the transient and resident societies is the way they impart information. Killer whales detect prey with a range of echo-locating clicks, but converse with a vocabulary of squeaks, whistles and whines. Transients have only a few such calls, and all transient societies share the same ones. Residents have a much more extensive repertoire, and each family group has its own unique and distinctive set of calls. Despite regular interaction between them, each resident pod sticks firmly to its own dialect. Research shows these dialects are maintained for at least 40 years.

E. To qualify as part of killer whale culture, dialects must be learnt from other members of the pod. Animals with different dialects share the same waters, so the variations cannot be a product of the physical environment. "And we can throw out the notion that the dialects are inherited," says Lance Barrett-Lennard of the University of British Columbia. He has spent the past seven years analyzing DNA from 270 whales. His paternity tests reveal that female killer whales invariably attract mates from outside their own pod - males with a very different dialect. If dialects were programmed by genetics, call patterns from both father and mother would be passed on to the calf. "A calf uses the calls of its maternal pod very precisely. There is no input from the father," says Barrett-Lennard.

F. The question still remains - is this culture? It is, according to Frans de Waal of Emory University in Atlanta, who argues that culture is just another biological adaptation that has evolved in many creatures. One benefit of viewing culture in this way is that you can start to understand how and why it might have arisen in these creatures. Whales have several biological attributes that give them an advantage in social learning. Apart from their advanced mental abilities, they are adept at recognizing sounds: ideal for communication in the marine environment. Many species spend years rearing their offspring, and live in small, stable, multi-generational societies, a social system that provides ample opportunity for teaching and learning.

G. But why have cetaceans evolved the ability to learn from other group members? Experts in whale biology believe that ecological factors and the need to adapt to sudden changes in the environment played a large part in the emergence of culture. Although the ocean is a relatively stable habitat in many ways, it is highly changeable in one crucial respect - the availability of food. One moment there might be a plentiful supply of fish, the next they have disappeared. When that happens, the past experience of the senior members of the group - and the ability to share this knowledge - is a huge asset. The dialects of killer whales allow members of the groups to identify each other, enabling them to share information about food hot spots. Among resident killer whales, it also allows females to avoid inbreeding by picking out a mate with a strange dialect from outside their pods, says Barrett-Lennard.

H. The importance of shared information seems to have led to biological changes in at least some species of whale. Female killer whales, like humans, are very unusual in that they live up to a quarter of a century after they had their last offspring. This only makes sense if they have something useful to give their descendants. And what whale matriarchs offer is the most important thing of all - cultural knowledge, vital for the group's survival, passed directly from one generation to the next.