Palaeontologists have found some exceptional places (lagerstätten) where fossils of early birds are found. The preservation is so good that on the best examples impressions of their feathers can be seen, and sometimes even the remains of meals they have eaten. From these remains we know that birds evolved from small carnivorous dinosaurs (theropods) in the Jurassic period. They radiated into a huge variety in the Lower Cretaceous. At the same time, their direct competitors, the pterosaurs, dwindled in numbers and variety, and became extinct at the end of the Mesozoic.
Birds are classified by taxonomists as 'Aves' (Avialae). Birds are the only living descendants of dinosaurs (strictly speaking, they "are" dinosaurs). Birds and Crocodilia are the only living members of the once-dominant Archosaur reptiles.
The class Aves is now defined as all the descendants of the most recent common ancestor of modern birds and "Archaeopteryx lithographica".
"Archaeopteryx", from the Upper Jurassic some 150–145 million years ago (mya), was for a long time the earliest known bird which could fly. It is famous, because it was one of the first important fossils found after Charles Darwin published his ideas about evolution in the 19th century. By modern standards, "Archaeopteryx" could not fly very well. Other early fossil birds are, for example, "Confuciusornis", "Anchiornis huxlei" and other Paraves.
Many fossils of early birds and small dinosaurs have been discovered in the Liaoning Province of Northeast China. These include "Anchiornis huxlei", from about 160 mya. The fossils show that most small theropod dinosaurs had feathers. These deposits have preserved them so well that the impressions of their feathers can be clearly seen. This leads us to think that feathers evolved first as heat insulation and only later for flight. The origin of birds lies in these small feathered dinosaurs.
Palaeontologists now agree that birds are included in Maniraptora group of dinosaurs. This explains why we say that birds are living dinosaurs.
Some birds are eaten as food. Most usually it is the chicken and its eggs, but people often also eat geese, pheasants, turkeys and ducks. Other birds are sometimes eaten are: emus, ostriches, pigeons, grouse, quails, doves, woodcocks and even songbirds. Some species have died out because they have been hunted for food, for example the dodo and the passenger pigeon.
Many species have learned how to get food from people. The number of birds of these species has grown because of it. Seagulls and crows find food from garbage dumps. The feral pigeon ("Columba livia"), sparrows ("Passer domesticus" and starlings ("Sturnus vulgaris") live in large numbers in towns and cities all over the world.
Sometimes people also use working birds. For example, homing pigeons carry messages. Nowadays people sometimes race them for sport. People also use falcons for hunting, and cormorants for fishing. In the past, people in mines often used a canary to see if there were bad gas methane in the air.
People often have colorful birds such as parrots and mynahs as pets. These intelligent birds are popular because they can copy human talking. Because of this, some people trap birds and take them to other countries to sell. This is not usually allowed these days. Most pet birds are specially bred and are sold in pet shops.
People can catch some bird diseases, for example: "psittacosis", "salmonellosis", "campylobacteriosis", Newcastle's disease, "mycobacteriosis", influenza, "giardiasis" and "cryptosporiadiosis". In 2005, there was an epidemic of bird influenza spreading through some parts of the world, often called avian flu.
Some people have birdboxes in their gardens to give birds a place to nest and bird tables where birds can get food and water in very cold or very dry weather. This lets people see some small birds close up which are normally hidden away in bushes and trees.
The following is a listing of all bird orders:
A report produced by BirdLife International every five years measures the population of birds worldwide. In 2018 the number of bird species has decreased by 40%. One in every eight types of birds is now almost extinct.
Freedom of speech
Freedom of speech is the right to state one's opinions and ideas without being stopped or punished. Sometimes this is also called Freedom of expression. Freedom of speech is thought to also include Freedom of information. However, new laws are usually needed to allow information to be used easily.
Most people think freedom of speech is necessary for a democratic government. In countries without free speech, people might be afraid to say what they think. Then, the government does not know what the people want. If the government does not know what they want, it cannot respond to their wants. Without free speech, the government does not have to worry as much about doing what the people want. Some people say this is why some governments do not allow free speech: they do not want to be criticised, or they fear there would be revolution if everyone knew everything that was happening in the country.
A well-known liberal thinker, John Stuart Mill, believed that freedom of speech is important because the society that people live in has a right to hear people's ideas. It's not just important because everyone should have a right to express him or herself.
Few countries with "free speech" let everything be said. For example, the United States Supreme Court said that it was against the law to shout "fire" in a crowded theater if there is no fire, because this might cause people to panic. The International Covenant on Civil and Political Rights also says that it is not okay to cause national, racial or religious hatred. Also, some countries have laws against hate speech.
As Tocqueville pointed out, people may be hesitant to speak freely not because of fear of government punishment but because of social pressures. When an individual announces an unpopular opinion, he or she may face the disdain of their community or even be subjected to violent reactions. While this type of suppression of speech is even more difficult to prevent than government suppression is, there are questions about whether it truly falls within the ambit of freedom of speech, which is typically regarded as a legal right to be exercised against the government, or immunity from governmental action.
Banana
A banana is the common name for a type of fruit and also the name for the herbaceous plants that grow it. These plants belong to the genus "Musa". They are native to the tropical region of southeast Asia.
It is thought that bananas were grown for food for the first time in Papua New Guinea. Today, they are cultivated in tropical regions around the world. Most banana plants are grown for their fruits, which botanically are a type of berry. Some are grown as ornamental plants, or for their fibres.
There are about 110 different species of banana. In popular culture and commerce, "banana" usually refers to the soft and sweet kind, also known as "dessert bananas". Other kinds, or cultivars, of banana have a firmer, starchier fruit. Those are usually called plantains. Plantains are mostly used for cooking or fibre.
Other than being used as food, beer can be made by fermenting the juice of certain cultivars in Africa, known as "beer bananas". The ash of bananas can be used to make soap. In Asia, bananas are often planted to provide shade to plants that like shade, for example coffee, cocoa, nutmeg or black pepper. Because of this, banana plants can often be found in plantations of other crops.