TEST 17

The food chain is the order in which animals and plants eat each other in order to survive. Every living creature needs to eat other creatures below it. Every ecosystem has a different food chain, depending on which animals and plants live there.

The lowest part of the food chain are the plants. They are called producers because they produce their own food using the sunlight's energy. This process is called photosynthesis. Animals are the consumers of the food chain. They eat other plants and animals.

Some animals only eat plants. Among this group of herbivores are rabbits, mice and cows. Carnivores are animals that eat other animals, like wolves, foxes or lions.

Each food chain has a predator, the strongest animal that is not eaten by others. Hawks or polar bears are such predators that dominate their habitats.

Many creatures belong to more than one food chain. Grass, for example, is eaten by many other animals as well as insects. Food chains that are connected to each other are called food webs.

When an animal dies it is eaten up by worms, bacteria and other organisms. These so-called decomposers break down animals and plants into small parts and enrich soil so that other plants can grow better. The nutrients of dead animals and plants are converted back to the soil so that plants can use them again.

The balance of plants and animals within a food chain is determined by nature. For example, if there are too many zebras in a tropical habitat many of them will die because they cannot get enough food to feed on. This also means that there is less food for predators, like lions, to eat. And when there are fewer lions the zebra population will grow again.

TEST 18

Bananas belong to the most popular and most eaten fruits in the world. They were first grown in tropical India and Southeast Asia over 4000 years ago. Arab merchants brought them to northern Africa and the Middle East.

Portuguese navigators discovered bananas when they sailed down the Atlantic coast of Africa.  From there they were brought to the Canary Islands, from where Spaniards took them to the New World.

Physical Features of a Banana Plant

Although bananas grow like trees they are actually plants. They are made up of stalks that are covered with overlapping leaves. A stalk or stem can be about 30 cm thick. A banana plant can grow up to 6 meters in height. It has up to 20 long and wide leaves.

Bananas hang in clusters, also called hands, from the plant. Each cluster can carry about 10 to 20 bananas.

Bananas need good, well-drained soils, as well as a warm tropical climate with enough rainfall to grow. They are often cultivated on plantations, often with hundreds of workers who cultivate and harvest bananas for the world market. These large farms sell their products to large companies like, Chiquita and Dole.

The first banana fruits can grow about a year after planting. Bananas are endangered by temperatures below zero and strong winds. Diseases, like the Panama disease, an infection of the soil, can completely destroy banana crops.

Bananas are harvested while they are still green. In this state the banana's flesh is white and cannot be eaten. The green fruits are taken to the nearest port, where they are put on container ships with cooling containers on board.

When the bananas arrive at their destination they are loaded onto trucks or railway cars and brought to sellers who store them in special ripening rooms. From this time on it takes bananas about five days to ripen and get the yellow colour and taste we all know. As the fruit ripens the flesh also becomes sweet.

Banana as a staple diet

In many tropical regions of Africa, South America and Asia, bananas are a main food for the population. They have many nutrients that people need. In addition to 75 % water, a banana contains sugar, proteins and vitamins. It gives you quick energy and can be digested fairly easily.

Bananas belong to the healthiest foods in the world. They contain potassium, which can lower your blood pressure, prevent heart diseases and reduce the risk of a stroke.

In the western world bananas are eaten as snacks in-between meals or together with cereals. In other countries they are used to make wine or beer.

Types of bananas

There are up to a thousand different kinds of bananas. The Cavendish banana is the most widely produced and eaten fruit in the world. Bananas that are used for cooking are called plantains.

Economic Value

Bananas are the fourth most valuable food crop in the world, after wheat, rice and corn.

They are important for the economy of tropical countries. About 140 million tons are harvested annually, however only a small percentage of the actual production is exported. The biggest banana-producing countries in the world actually need most of the fruit themselves.

India is the world’s largest banana producer, followed by Uganda, China, the Philippines, Ecuador and Brazil.

Banana Trade

Today the banana trade is a 5 billion dollar industry. Large companies like Chiquita and Dole control most of the banana exporting industry. Especially in Central America and the Caribbean workers suffer from poor working conditions and get low wages.

For decades EU countries preferred bananas from their former colonies in Africa and the Caribbean and placed taxes on imported South American bananas. In 2009 this long trade war came to an end.

TEST 19

About 75% of the world’s animals are insects. They have been living on earth for over 400 million years, long before humans appeared. Insects have changed a lot and adapted to new climates in order to survive. Today, there are about one million different species of insects and scientists are discovering new groups daily. Insects have different sizes and body forms. Most of them are very small but they can grow as large as 30 cm. Among the most common insects are flies, beetles, bees, butterflies, moths and wasps.

Where insects live

Insects live in every region of the world. They can survive in any type of climate, from tropical rainforests to icy polar regions, as long as they can find food. The oceans are the only places where few insects live. Because they are so small, they can live in places where other animals cannot survive, some even live in underground caves.

Physical features

Insects belong to a group of animals called arthropods. They do not have a skeleton but a kind of shell that protects them. This exoskeleton is very tight and does not grow with the insect. When an insect becomes too large for the shell it breaks open and a new shell develops.

Insects have three major body parts: head, thorax and abdomen. They have six legs and at least one pair of feelers.

An insect’s antennae, mouth and eyes are located in the head. The compound eyes consist of up to 4,000 separate lenses that combine images inside an insect’s brain. Such a complex eye gives it extremely good eyesight. Insects use antennae to smell and feel. If their feelers are damaged they become helpless.

The thorax has three pairs of legs and two pairs of wings, however, some insects have no wings at all.

The abdomen is the largest part of an insect.

It contains organs that digest food, release waste and let insects reproduce.

How insects behave

Insects protect themselves from enemies in many ways.  Some can blend into their surroundings by changing their colours. Others, like beetles, have a hard shell that protects them. Some insects produce poison and inject it into enemies by biting or stinging them.

Most insects live alone but there are some social insects that live in colonies. Termites, ants and bees are examples of insects that live in groups of thousands or even millions, in which everything is organized and each insect has a certain task. Such a society is headed by a leader, a queen or a king, whom others follow.

Insects eat plants, animals and other organisms. They also live on other animals and get food from their body. Such insects are called parasites.

Certain insects migrate during the wintertime. The monarch butterfly, for example, flies south to tropical and subtropical areas. In spring they come back to their original habitat.

Life cycle of insects

Most insects are born from eggs. Their covering or shell cannot grow and they break out of it after a certain time. After that an insect grows a new shell. This process is called moulting. An insect can moult many times until it becomes a fully grown adult. This process, from hatching out of an egg to becoming an adult, can take between a few days and many years. As an adult, most insects live only for a short time. But there are a few, like the queen of a termite colony, which can live for many years.

Some insects change completely during the different stages of their life. This is called metamorphosis. After hatching from an egg they become a larva, which takes on a wormlike shape. A larva eats a lot and moults several times during its development process. After growth an insect becomes a pupa. It spins a protective covering around itself. During this resting stage an insect develops wings and legs and other body features. In the final stage an adult emerges from the pupa. Bees and butterflies grow in this way.

Insects and humans

Insects can be helpful to humans in many ways. They eat other insects and dangerous animals that may endanger fields and crops. They keep our environment clean by eating animal waste and other unwanted substances. Some produce valuable products like honey and silk. Flowers, fruits and other plants depend on insects to help spread pollen.  On the other side, insects are an important source of food for birds, frogs and other animals.

There are very few harmful types of insects, but they can do a lot of damage. Some of them spread diseases by stinging and biting people. In tropical regions insects are the main carriers of malaria or the plague. They injure pets and animals, and do damage to trees and crops.

TEST 20

Sugar is used as a sweetener all over the world. People sugar all sorts of food and drinks to make them taste better. Sugar is often added to tea or coffee and to certain types of pastries.  The food industry adds sugar to soft drinks and ice cream.

Sugar is a simple carbohydrate, a substance that gives us energy. However, too much sugar can be harmful. It can cause obesity and tooth decay. People who consume too much sugar can be hyperactive. That is why some people use artificial sweeteners instead of sugar.

Types of sugar

Our sugar is also referred to as sucrose. It is made up of two basic components. Glucose comes from the carbohydrates that we eat. Our body changes them to energy and transports them into the bloodstream. Fructose occurs naturally, especially in fruits, vegetables and honey. When we eat an apple or orange fructose is changed into glucose and goes into our blood.

Lactose, or milk sugar, is found in dairy products. Some adults are not able to digest milk sugar and should not consume dairy products.

How sugar is produced

Sugar can be manufactured from two natural products: sugar cane and sugar beets. About 70% of the world’s 200 million tons of sugar comes from sugar cane.

Sugar beets grow in temperate climates of the world.  Sugar is contained the white roots of the beet. These beets are dug out of the ground and brought to a factory, where they are washed and cut. Afterwards they are heated to a juicy mixture. As the juice evaporates sugar crystals start to form. They are separated from the juice and processed further. Raw sugar is brown or yellow. It is chemically bleached to make it white. Then sugar is packaged and sold.  The syrup that is eventually left over is called molasses.

Sugar cane is in the stalks of a tall plant that grows in the tropical regions. Brazil, India and China are the world’s largest producers of sugar cane. When the stalks are ripe they are harvested and crushed in a special machine that squeezes out the sugar liquid. The process after that is similar to the way sugar beets are processed.

History of sugar

Sugar has been known for a long time. Early inhabitants of Pacific Island used sugar thousands of years ago. Sugar cane was also grown in ancient India and in other cultures. Sugar reached Europe at the beginning of the Middle Ages. During the Age of Exploration navigators brought sugar to Africa and America, where it was planted in the southern colonies of the United States.

TEST 21

Coffee is one of the most popular hot drinks in the world. Almost a third of the world’s population drinks coffee.  People often meet at cafes or coffee shops for a coffee break during the middle of the morning or stop work in the afternoon to drink coffee.

About 7 million tons of coffee are produced every year. Brazil is, by far, the world’s largest coffee producer. About a third of the world’s production comes from this South American country. Other coffee producing countries include Vietnam, Indonesia and Columbia.

The United States is the biggest coffee consumer in the world. About 1.2 billion kilograms of coffee are consumed there every year. Drinking coffee is extremely popular in European countries, like Italy, France and Germany, as well as in Brazil.

The coffee plant

Coffee grows as a green-leaved tree or bush with blossoming white flowers. The coffee shrub originally comes from Ethiopia but, in the course of time spread to Southeast Asia and South America.

There are two basic types of coffee. Arabica accounts for about 70% of the world’s coffee production. It is grown in the higher regions of central and South America and is popular for its flavor and fragrance. Robusta has spread throughout central and eastern Africa. Although it makes up only thirty per cent of the total coffee production it has become more important because it can resist diseases better. It also has smaller beans and can grow at lower altitudes than Arabica.

Coffee plants grow in the warm and moist climate of the tropics and subtropics. Most coffee trees grow best between 1000 and 2500 meters above sea level.

Coffee trees produce fruits called berries. At first they are yellow, and then become red as they mature. An average coffee tree can produce enough berries to make about a pound (half a kilo) of roasted coffee.

Coffee seeds are grown in nursery beds. After a year they are planted in specially prepared fields. It takes a coffee tree about six years to produce a full harvest of coffee berries.  The largest ones can get up to six meters tall, but they are normally trimmed to a height of 1.5 to 4 meters.

Harvesting and processing coffee

Most coffee berries are picked by hand, which makes sure that only the good berries are used. After separating berries from leaves and other waste materials, the beans are then taken out, cleaned and dried. Only the best beans make it to the market. Then they are put into bags and shipped to countries where they are roasted.

At their destination the beans are combined to make different blends of coffee. Roasting for about 15 minutes brings out the true flavor of the coffee. The roasted coffee beans are packaged; some of them are crushed to ground coffee.

Effects of coffee

Coffee contains caffeine, a substance that stimulates parts of the body, especially heart and muscles. People often drink coffee to help them stay awake or keep them alert. Although coffee has some negative effects it is not thought to be a harmful drink. Children and people who have heart problems should not drink coffee it in great quantities. In decaffeinated coffee the caffeine is extracted in a chemical process.

How coffee is brewed.

Coffee must be ground before it is brewed. Grounding usually takes place inside a coffee machine, but you can also buy ground coffee in shops. The simplest brewing process is pouring boiling water over a filter of ground coffee and letting it flow into a pot. Coffee is often made by using simple machines that force hot water through a pad of pressed coffee. Espresso machines press hot water through ground coffee.

Instant coffee is made by pouring hot water over powdery coffee. It dissolves at once and you do not need a special machine.

History of coffee

Coffee originated in the east African highlands in the 6th century. It was then brought to Arabia where people used it as food and medicine. During the 11th century the first coffee drinks came up. In the 16th and 17th centuries coffee became widely popular in Europe when the Turks brought it to Central Europe. In the 17th and 18th century coffee conquered North and South Amercia

Coffee houses soon became popular all over the world. In the 1900s chains of coffee shops developed in Europe and America. Today, Starbucks is the largest coffeehouse chain in the world, with over 20,000 stores in 60 countries.

Types of Coffee drinks

Espresso is probably the most popular coffee drink in the world. It is made by forcing hot water through a pad filled with dark ground coffee. Although there is not much coffee in the cup an espresso is very strong. It is usually drunk black, with no milk added.

Americano is an espresso with hot water added to make it weaker.

Café Latte is an espresso with a lot of hot milk and foam added on the top

Cappuccino is a cup of espresso, together with warm milk and a lot of milk foam at the top. In some coffee shops it is decorated with flaked chocolate or cocoa.

Cafe Mocha is a cappuccino with chocolate or cocoa added

Frappe is a cold espresso  that you can get at some coffee shops during the hot summer months

Turkish coffee is usually thicker than normal coffee. It is made by combining  ground coffee and water to a muddy mixture

TEST 22

Fish are animals that live in water.  They are vertebrates, animals with backbones, and come in all kinds of shapes, sizes and colors. Fish first appeared in the oceans of the Earth about 500 million years ago, long before dinosaurs roamed our planet. Today there are tens of thousands of different kinds of fish and new species are discovered every year. Over millions of years fish have changed their features and adapted to their surroundings in order to survive.

The whale shark is the largest fish on Earth. It can grow up to 12 meters in length and can weigh up to 15 tons. In contrast tiny gobies are often only a few mm long.

Fish are important to people. They were among the first animals hunted by primitive human beings. Millions of people all over the world depend on fish as a main form of nutrition. In many coastal countries, for example Japan or Norway, people depend on fishing to make a living.

Fish are a part of the food chain. They eat animals and are eaten by other sea creatures, thus keeping up the balance of nature.

Where fish live

Fish live all over the world, in the cold water of the Arctic as well as in warm tropical water around the equator. Areas rich in fish are especially around the coastal shelves of the Northern Atlantic, the Caribbean Sea and the western Pacific Ocean.

Most of the world’s fish live in salt water. They preferably live in areas where warm and cold currents meet. Some types live in the warm tropical waters around coral reefs.

About 40% of all fish species are in fresh water. They include carp, catfish, trout or bass. Some of them live in the clear water of rivers while others prefer muddy pond water. A few types of fish can swim in both salt and fresh water. Salmon, for example, are born in fresh water , migrate to the ocean and then return to fresh water to reproduce.

Bodies of fish

Fish have no neck. The head and body are combined to one. Most species have a skeleton made of bone, only a few species have backbones made of cartilage.

Most fish are shaped like cigars or torpedoes, so that they can travel very quickly. Fish that swim near the ocean floor are flat-shaped. Eels look like long snakes under water.

Fish are cold-blooded. Their body temperature changes with their surroundings. Almost all fish have fins, instead of arms and legs, which they use for swimming.

The skin of most fish is made out of a special slippery substance. It is covered by small plates called scales. Some scales have special cells that give fish a certain color.

Fish breathe oxygen from the water they live in. Gills on the side of a fish’s head absorb oxygen from the water and release carbon dioxide into it.

Some animals in the oceans of the world look like fish but are actually mammals. Dolphins and whales have lungs and must come up to the surface for air.

Senses

Fish have organs that tell them what is happening in the water around them.  They can see left and right at the same time. Although they have no physical ears they have hearing organs on the side of their head.  They not only can hear sounds in the water but can also sense sounds that happen on the surface.

All fish have a sense of smell. In some species, for example sharks and salmon, it is highly developed.  Fish can also feel pressure of water movements, thus feeling dangers that approach them.

Fish have a special sense called the lateral line. It is a row of cells that works like radar and help them navigate through waters.

How fish live

Most fish eat meat, preferably other fish.  They also eat plants, worms and algae. The largest fish in the world consume huge masses of plankton.

Fish have to protect themselves from being eaten by other fish. They blend into their surroundings by changing their color or their shape. Some fish are very fast swimmers and get away from their enemies very quickly.  Others release poisonous substances from their spines.

Although most fish are harmless to humans some will attack if provoked. Sharks attack humans if they smell blood or if people make uncontrolled movements.  Piranhas live in the waters of the tropical rainforest. They attack their victims with their sharp teeth and tear their flesh apart.

How fish reproduce

Fish reproduce by releasing male sperm and female eggs into the water at the same time. The process of joining together is called spawning. Eggs are food for other fish. Many females release hundreds of thousands of eggs to make sure that at least some of the young ones can survive.

Many fish leave their eggs after spawning. Some of them stay and protect their eggs until they hatch. Salmon cover their eggs with sand and gravel.

Danger to fish

Fish are caught for a number of reasons. Apart from providing food for millions of people they are used for animal feed and to produce oil.

Overfishing in the world’s oceans poses a threat to many species. Some are in danger of dying out. Catch quotas have been introduced to save some of the most important species. Fish are also endangered by pollution of the world’s oceans. 

TEST 23

Cloning occurs when you copy a living creature. Two clones have the same genes, small structures with information in them that tells them what the body of a living thing should look like and how it should behave. You get the genes from your parents.

Many people think that cloning is only done by scientists in laboratories, but, in fact, cloning also occurs in nature.

Cloning animals

Animals have billions of cells. The nucleus of such a cell has genetic information called DNA. All the nuclei of an animal have the same information. But each cell only uses a part of this information in order to work properly. The other part of the DNA is not active. But because a single cell holds all the DNA of an animal, scientists can make physical copies of an animal from only one cell.

They transfer the nucleus of an animal’s cell into an egg cell of another animal. This egg cell has the same genetic information as that of the donor animal. The cell then grows into an embryo. Scientists must then activate the DNA that was not active in the parent cell. Otherwise a full organism would not develop.

Clones do not behave in an identical way – this is because they live in different environments. Researchers have found out that identical twins that carry the same DNA are different because they grow up differently.

History of cloning

Cloning animals started way back in the 1950s when the first frogs were reproduced. In 1996 British scientists cloned the first mammal, a sheep called Dolly. Since then the cloning of mice, cattle, cats and other mammals has been successful.

Pros and cons of cloning

 The cloning of certain animals may bring advantages to humans. The cloning of cattle or sheep can produce animals whose meat quality is better or which are more resistant towards illnesses.

Scientists, however, cannot yet create perfect clones. Many of them do not survive the cloning process and die before they are born.

In the past human embryos have been cloned in order to get stem cells. These are cells that can develop into many different kinds of other cells. Doctors are able to use stem cells to replace parts of the body that are ill, like skin or other organs. Although this could be a major breakthrough in medicine many people fear that cloning embryos is murder and must therefore be forbidden. Many countries have put bans on cloning or other experiments that produce cloned human embryos.

Some scientists still believe that it may be possible to clone a human being from the cells of one adult. For a long time this has been thought of as science fiction.

Many problems arise when it comes to cloning human beings. What should be the ideal characteristics of reproduced humans: should they be highly intelligent, strong or creative. Who are the people to decide these questions? Critics of cloning say that creatures should be born in a natural way. Nobody has the right to play God.

 Natural cloning

Clones occur naturally in many cases, for example, when a mother gives birth to two identical twins. They come from the same fertilized eggs and are therefore have identical genes. Bacteria and animals with only one cell can also reproduce themselves in a natural way. Plants can also produce clones. Farmers use breeding techniques to produce certain types of plants.

 Reasons for cloning

Cloning is often performed for medical reasons. Experiments are carried out on animals that carry a disease which causes mutations in their genes. Farm animals are cloned to produce drugs and other substances that are useful in medicine. Cloning is a way to produce large numbers of genetically engineered animals.

Therapeutic cloning

In therapeutic cloning stem cells are reproduced in order to create new organs and tissue. New, healthy tissue can help a person get a new heart or a new liver to replace his ill one. Such a method could also create stem cells that you could use for patients who suffer Alzheimer’s or Parkinson’s disease.

TEST 24

Marine biology is the study of the ocean’s plant and animal life. Marine life gives us food, medicine and other raw materials we need. It also maintains tourism and provides us with an area of recreation. Organisms in the ocean produce oxygen and help regulate the earth’s climate. Coasts are partly created by marine life; some marine organisms even help to create new land.

Marine biology ranges from very small organisms, like plankton, to huge 30 meter long whales. Habitats stretch from the ocean’s surface to the ocean trenches which are over 10,000 meters deep.

About 71% of the Earth’s surface consists of oceans. They are, on average, about 4,000 meters deep. A large part of the Earth’s life lives in them, even though not all forms of marine life have yet been discovered.

Studying marine life is a large field of science. The oceans are home to many different species, including fish, birds, reptiles and other organisms. Scientists also research out how organisms live in salt water.

Marine animals and plants

Many birds have adapted to life in ocean regions. Seabirds usually live longer and have fewer young ones than other birds do. Most of them travel thousands of miles a year and cross the equator from the northern to the southern hemisphere. Humans have depended on seabirds throughout history. They have shown seafarers the way and guided sailors to land. Among the best-known are albatrosses and Arctic terns.

Fish belong to the main species that live in the oceans. They range from tiny sardines to dangerous sharks. Fish serve as one of the main sources of food for humans.

Invertebrates are animals that do not have backbones. Many of them live in the sea and around coastal regions, like jellyfish, sea worms, shellfish or octopuses.

The largest mammals of the oceans are whales. Dolphins and sea lions are among other mammals that live in the sea. Sometimes the polar bear is referred to as a sea animal because it depends on seafood.

Most marine reptiles live in or near the coastal waters. They include sea turtles and saltwater crocodiles. Many species need to come to land to lay their eggs.

There is a very diverse plant life in the world’s oceans. Algae and sea grass are among the most common. Such plants have become used to a salty environment. Different types of plants also grow in areas where the water surface is affected by the rise and fall of the tides.

Habitats

Different forms of life live in various areas of the ocean. Some are limited to the coastal and shelf areas, while others live in the open sea.

Coral reefs are found in the tropical areas of the world, but they can also exist in colder water. Reefs are built by corals and other animals that deposit calcium on rocks. They are home to a vast variety of different life forms. About half of the world’s coral reefs, however, are in danger because of global warming and a rise in sea temperatures.

Although we do not know very much about what kind of life forms exist in deep water trenches, marine scientists have found out that a certain type of jellyfish and a flatfish were seen in the Mariana Trench, the world’s deepest ocean area. Generally these parts of the ocean have little or no sunlight and many organisms that live here have to produce their own light.

Marine biologists also study how waves, currents and the tides affect organisms living in the world’s oceans. Little is known about where certain species travel to breed.

TEST 25

Factory farming is a method of mass food production in which animals are kept in very confined areas in order to get the best possible profit. Factory farming wants to keep production costs low and sell cheaper food to consumers.

            Factory farming is a much discussed issue. Animal rights activists and environmentalists claim that this type of food production is dangerous to our environment and forces animals to live in an unworthy way. On the other side farmers and larger food corporations claim that they cannot produce enough food at reasonable prices without factory farming.

Over the past decades farms have grown in size and intensity. Farming has become an industry, using modern technology. Today farmers use pesticides, antibiotics and vitamins to produce as much as they can and to control diseases. Fertilizers make it possible to grow more crops than nature would allow. These factors lead to lower food prices on supermarket shelves.

Those who are in favor of factory farming say that it creates jobs and lets consumers buy cheaper food. They also state that it is friendly to our nature because it uses less land to produce the same amount of food.

Critics against factory farming say that it is brutal and cruel to animals. They live in overcrowded cages or boxes without enough space to move around. Chicken, sheep, cattle and pigs are often kept in such a way. They are given special feed so that they can grow quicker. Crops that are sprayed with pesticides are a health risk to humans and have a number of chemicals in them. They also argue that such large farms ruin smaller ones because they can produce at more competitive prices.

Although products from factory farms are not labeled consumers can buy food from organic production. Some products, like eggs, have labels on the boxes that say they are laid by hens that can move around and are not kept in cages.

TEST 26

A mammal is an animal that feeds its babies with milk when it is young. There are over 4,500 types of mammals. Many of the most popular animals we know are mammals, for example, dogs, cats, horses, cows, but exotic animals like kangaroos, giraffes, elephants and anteaters belong to this group, too. Humans are also mammals.

Mammals live in all regions and climates. They live on the ground, in trees or underground. Polar bears, reindeer and seals are mammals that live in the Arctic regions. Others, like camels or kangaroos prefer the world’s dry areas. Seals and whales are mammals that swim in the oceans; bats are the only mammals that can fly.

Mammals have five features that make them different from other animals:

Female mammals produce milk and feed their babies with it.

Only mammals have hair or hair-like skin. All mammals have hair at least some time in their lives.

Mammals are warm-blooded. Their body temperature always stays the same and does not change with the outside temperature.

Most mammals have a larger and well-developed brain. They are more intelligent than other animals.

Mammals protect their babies more than other animals. They prepare them for future life.

People have hunted mammals for ages. They ate their food and made clothes out of their skins. Thousands of years ago wild mammals were domesticated and gave human beings milk, wool and other products. Some mammals, like elephants and camels are still used to transport goods. In poorer countries farmers use cows or oxen, to plough fields.

Today some mammals are hunted illegally. Whales are killed because people want their meat and oil, elephants are killed for the ivory of their tusks.

Mammals are often kept as pets. Among them are cats, dogs, rabbits or guinea pigs.

Mammals are useful to people in many other ways. Some help plants grow and eat harmful insects. Others eat weeds and prevent them from spreading too far. The waste of mammals is used as fertilizers that improve the quality of soil.

Types of mammals

Mammals are divided into three groups:

Monotremes are mammals that lay eggs, like a bird. They live in Australia and New Zealand. The platypus belongs to this group

Marsupials are mammals that raise their young ones in a pouch in their bodies.

Placentals are the largest group of mammals. The babies grow inside their mothers until they are ready to be born. Humans are placentals.

Mammals and their bodies

Skin and hair cover a mammal’s body. Some mammals have horns, claws and hoofs. The hair or fur of a mammal has many functions. The colour often blends in with the world around them and allows them to hide from their enemies. Some mammals produce needles or sharp hair that protects them from attack. But the main function is to keep the body warm.

Mammals have glands that produce substances that the body needs like hormones, sweat and milk.

A mammal’s skeleton is made up of three parts:

The skull contains the brain, teeth and other organs.

The spine or backbone enables mammals to stand or walk.

Limbs are legs and arms of a mammal, often with strong bones.

Mammals have a four-chambered heart system that pumps blood into all parts of their body. The blood brings oxygen to muscles and tissue. The red blood cells of mammals can carry more oxygen than in many other animals. Because mammals have a high body temperature they must burn a lot of food.

Mammals digest food through their digestive system. After food is eaten through the mouth it goes down the throat into the stomach and passes through the intestines. Mammals that eat plants have a complicated system with long intestines that help break down food. Flesh is easier to digest so meat-eating mammals have a simpler stomach.

Mammals breathe air through their lungs. Most of them have noses or snouts with which they take in air. Dolphins and whales breathe through a hole in the top of their back.

Mammals and their senses

Mammals have five senses that tell them what is happening in their surroundings. Not all senses are developed equally among mammals.

Mammals rely on smell to find food and warn them of their enemies. Many species use smell to communicate with each other. Humans, apes and monkeys have a relatively bad sense of smell.

Taste helps mammals identify the food that they eat. Most mammals have a good sense of hearing. Some mammals use their hearing to detect objects in the dark. Bats, for example, use sounds to navigate and detect tiny insects. Dolphins also use such a  system to find their way around.

While higher primates, like humans, apes and monkeys have a highly developed sense of sight other mammals are nearly blind. Most of these mammals, like bats, are active at night.

Mammals have a good sense of touch. They have nerves on all parts of their body that let them feel things. Cats and mice have whiskers with which that they can feel themselves around in the dark.

What mammals eat

Herbivores are mammals that eat plants. They have special teeth that allow them to chew food better. Examples of herbivores are deer, cows and elephants. The giant panda is a plant eater that only eats bamboo.

Carnivores are mammals that eat other animals. Cats, dogs, tigers, lions, wolves belong to this group. They are hunters that tear their prey apart with sharp teeth. They do not chew their food very much.

Omnivores are mammals that eat plants and meat. Bears, , apes, pigs and humans are examples of omnivores.

How mammals move

Most mammals live and move on the ground. They have four legs and walk by lifting one foot at a time or by trotting. Kangaroos hop and use their tail for balancing.

Mammals that live in forests spend a lot of their time in trees. Monkeys can grasp tree branches with claws and can hang on to them with their curved tail. Often mammals spend time hanging upside down in trees.

Dolphins and whales are mammals that live and move around in water. Instead of limbs they have flippers which they use to move forward. Other animals, like the hippopotamus, only spend some time in the water.

Bats are the only flying mammals. Their wings are made of skin stretched over their bones. They can fly by beating their wings up and down.

Gophers and moles are mammals that spend most of their life underground.

How mammals have babies

Mammals reproduce when a male’s sperm gets into contact with a female egg and fertilizes it. A young mammal grows inside the female’s body. Before this can happen mammals mate. Males and females stay together for a certain time.

Unborn mammals live their mother’s body for different periods of time. While hamsters are born after only 16 days, it takes elephants 650 days to give birth. Human pregnancies last about 9 months.

Many new-born mammals, like horses and camels, can walk and run shortly after they are born.

Marsupials give birth to babies that attach themselves to their mothers. They stay in pouches because they are too weak to live alone. Almost all marsupials, including kangaroos, koala bears or wombats live in Australia .

After birth the glands of a female mammals produce milk. Some mammals nurse their babies for only a few weeks. Others, for example elephants, give milk to their babies for a few years.

The duck-billed platypus and echidnas are the only mammals that lay eggs. After the young hatch they drink milk from their mother, just like other mammals do.

Life habits

Many mammals live in families or groups. Wolves and lions help each other in their search for food and protect each other from attackers.

Leopards, cats, tigers and other mammals prefer living alone . They do not share their living space and food that they have, however males and females get together to mate.

Mammals can mark the areas that they live in. They defend these areas by fighting off attackers. Some mammals claim territories only during the breeding season.

Many mammals migrate during special times of the year in order to get food and survive. North American bats travel to the south because insects become scarce during the cold winter months. Zebras and other wild animals follow the rainy seasons in Africa to find green grass. Whales migrate to warmer southern waters off the coast of Mexico to give birth to babies because they could not survive in the cold waters of the Arctic Ocean.

Some mammals hibernate because they cannot find enough food to survive. Their body temperature falls, heartbeat and breathing become slower. During this period hibernating mammals do not eat. They live from the fat of their bodies. Bats, squirrels and other rodents hibernate.

Mammals defend themselves from attackers in many ways. Hoofed mammals can run quickly in order to get food or escape. Squirrels rush into trees to hide. Some animals have special features that protect them from enemies. Skunks spray a bad smelling liquid to keep off attackers. The fur of mammals sometimes changes  with its surroundings. Arctic foxes, for example, are brown in summer and in the winter their coats turn white.

History of mammals

The first mammals probably evolved from reptiles about 200 million years ago during the Mesozoic period. They were rather small in a time when dinosaurs ruled the lands. When the dinosaurs died out about 65 million years ago mammals became the dominant land animals. Many mammals became extinct during the Ice Age , which ended thousands of years ago.

Today, some species are in constant danger of becoming extinct because they are hunted by humans. Hunters and poachers earn money by selling fur, tusks and other parts of mammals. Larger wild animals are often brought to zoos where they are protected.

TEST 27

Cotton is a plant that produces fibers , which are used to make clothes and other products, like towels , carpets or sheets . Clothes made out of cotton are especially light and comfortable .

What Cotton is Used For

Every part of the cotton plant can be used. The long cotton fibers are used to make cloth , the short fibers can be used in the paper industry. You can make oil or margarine out of the seeds of the cotton plant. The leaves and stalks of the cotton plant are plowed into the ground to make the soil better. Other parts of the plant are fed to animals.

Where cotton is grown 

Cotton is a subtropical plant that grows in many warm areas of the world. It started out as a plant of the tropics but today it is grown in other warm areas that have at least 200 frost-free days. The most important cotton-growing countries are the USA, China, India, Pakistan and Australia.

China produces about 30% of the world’s cotton fibre, mostly in the eastern part of the country. In the United States cotton is grown in the southern states, the biggest cotton producer is Texas.

Cotton needs a hot, sunny climate to grow. The plant needs soil that is well - drained and a lot of rainfall during the growing season. During the harvest season it should be sunny and dry. Some areas grow cotton on irrigated land.

Cotton needs soil that has a lot of nitrogen in it. Farmers use chemical fertilizers to improve the soil.

Growing and processing cotton

Cotton plants can reach a height of up to 2 meters.

After plowing the soil in spring cotton seeds are planted in rows by hand or machine. Three weeks after the plants come out flower buds begin to form. They produce white flowers that turn red and fall off . The flowers have a green fruit, called boll, which has seeds in it. White fiber of different lengths grows around the seeds . Cotton can be harvested when the boll bursts open and shows the fibers inside. The longest fibers are up to 6 cm long and are used for the best cloth . Most fibers, however ,are much smaller.

During the growth period cotton farmers must be careful that their crop does not get any diseases . They spray insecticides to keep insects away from the plant. Such insects destroy almost 15 % of the world’s cotton every year. Weeds also do damage to the cotton plants. They take away moisture that plants need so much.

Cotton is harvested about 150 to 200 days after farmers plant it. In industrial countries picking machines drive through the fields, harvest the cotton and transport it onto a trailer . In the Third World cotton harvesting is often done by hand.

Gins separate the cotton fiber from the seeds . Cotton is then combed , dried, cleaned and pressed into bales. Cotton buyers or brokers buy the raw cotton and then sell it to textile mills . There, spinning machines spin cotton into yarn . The yarn is woven into cloth, which is bleached and sometimes dyed .

History of cotton

Humans realized very early that the soft, fluffy cotton fibers can be used to make comfortable clothes.

Cotton was first grown in Pakistan and the Nile valley about 3,000 years ago. Native Americans started growing cotton at the same time in North America. Europe was introduced to cotton through Arab merchants at about 800 A.D . By 1500 cotton was known all over the world.

When Europeans founded colonies in America they relied on cotton to make a living . In the early days, growing and harvesting cotton was a hard job that was done manually by slaves .

In 1793 an American, Eli Whitney, invented the cotton gin , a machine that separated seeds from fiber. This new invention allowed farms to produce even more cotton.

In the second part of the 20th century people started to produce synthetic fibers , like nylon and acrylic. The importance of cotton fiber began to drop . By the middle of the 1970s cotton made up only one third of all fibers worldwide . Many cotton farmers had to close their farms. Governments , especially in America, had to help cotton farmers during this economically difficult period .

By 1990 the demand for cotton clothes became bigger, simply because people saw that cotton was a natural fiber and very comfortable to wear. By the turn of the millennium cotton regained its importance .

Towards the end of the 20th century farmers started experimenting with organic cotton , grown without chemicals or pesticides . Such cotton, however , has turned out to be more expensive than normal cotton.

TEST 28

The shark is a meat-eating fish and one of the most feared animals in the sea. There are over 300 types of sharks that live in oceans all over the world. Most of them live in warm seas but some sharks prefer colder regions like the seas around Antarctica.

The first sharks lived in our oceans about 300 million years ago. They belong to the earth’s oldest animals.

Size and habitat

Sharks have different sizes and habits. The largest is the whale shark, which can grow up to 15 metres long and weigh twice as much as an elephant. The smallest sharks are only about 16 cm long and weigh about 28 grams. One of the strangest looking sharks is the hammerhead, with a flat head that looks like a hammer.

Some kinds of sharks live in the deepest parts of the ocean, others are found near the surface. Some stay close to the coast, while others swim far out at sea. A few types of sharks even live in rivers and lakes.

All sharks are meat eaters. Most of them eat other fish, either as a whole or by tearing off chunks of a bigger fish. They also eat dead animals, plankton, crabs, sea turtles, seals, sometimes even whales.

A shark’s body

Most sharks have a body that is shaped like a torpedo. The two side fins are stiff; the tail is often curved and it helps the shark swim. Small scales cover a shark’s body and make its skin very rough. The mouth of most sharks is at the bottom of the head. They have many rows of teeth, which are sharp and pointed. New teeth grow and replace the older ones, sometimes as often as every week. Behind the eyes, sharks have five to seven gills on each side of the head. They use them to breathe underwater.

Sharks have sharp senses. They can find a fish to eat by the sound that it makes. They also have good eyes and can see almost everything in dark areas. Sharks must swim fast and well, otherwise they will sink. Some types have been recorded to swim at speeds of up to 90 km an hour.

Behaviour

More than half of the sharks in the world are not dangerous to people and seldom attack them. Among the most dangerous is the white shark, a fish with sharp teeth that can rip off chunks of flesh from animals. They hunt for large animals, such as sea lions, tuna and other sharks. They have even attacked human beings, especially when they are hungry or worried. Movement, noises or blood in the water can provoke sharks and make them attack.

Importance of sharks

Fishermen catch sharks mostly for their skin and flesh. Shark skin is used to make leather goods. The Chinese use dry shark fins to make popular and expensive soup. The liver oil of sharks has a lot of vitamin A.

Safety

Swimmers should always be careful in areas known to have sharks. Here are some rules to follow.

Never swim or dive alone.

Never swim or dive if you have an open cut on your body.

Leave the water immediately when you see a shark. Swim as smoothly as possible and avoid wild movements.