Fungi are eukaryotes which may have one cell, like yeasts, or many cells, like mushrooms. They are saprophytes. Fungi break down living or dead material, so they are decomposers. Only fungi, and a few bacteria, can break down lignin and cellulose, two parts of wood. Some fungi are mycorrhiza. They live under ground and give nutrients to plants, like nitrogen and phosphorus. Eukaryotes that are not plants, animals, or fungi are called protists. Most protists live in water.
Over thousands or millions of years, living things can change, through the process of evolution. One kind of evolution is when a species changes over time, such as giraffes growing longer necks. Most of the time, the species because better suited to its environment, a process called adaptation. Evolution can also cause one group of living things to split into two groups. This is called speciation if it makes a new species. An example is mockingbirds on the Galapagos Islands — one species of mockingbird lives on each island, but all the species split from a shared ancestor species. Groups that are bigger than species can also split from a shared ancestor — for example, reptiles and mammals. A group of living things and their shared ancestor is called a clade.
Living things can evolve to be quite different from their ancestors. As a result, parts of the body can also change. The same bone structure became the hands of humans, the hooves of horses, and the wings of birds. Different body parts that evolved from the same thing are called homologous.
Extinction is when all members of a species die. About 99.9% of all species that have ever lived are extinct. Extinction can happen at any time, but it is more common in certain time periods called extinction events. The most recent was 65 million years ago, when the dinosaurs went extinct.
By comparing fossils and DNA, we know that all life on Earth today had a shared ancestor, called the last universal common ancestor (LUCA). Other living things may have been alive at the same time as the LUCA, but they died out. A study from 2018 suggests that the LUCA is about 4.5 billion (4,500,000,000) years old, nearly as old as the Earth. The oldest fossil evidence of life is about 3.5 billion years old.
How did non-living material become alive? This is a difficult question. The first step must have been the creation of organic compounds. In 1953, the Miller–Urey experiment made inorganic compounds into organic compounds, such as amino acids, using heat and energy.
Life needs a source of energy for chemical reactions. On the early Earth, the atmosphere did not have oxygen. Oxidation using the Krebs cycle, which is common today, was not possible. The Krebs cycle may have acted backwards, doing reduction instead of oxidation, and the cycle may have made larger molecules. To make life, molecules needed to make copies of themselves. DNA and RNA make copies of themselves, but only if there is a catalyst — a compound which speeds up the chemical reaction. One guess is that RNA itself served as a catalyst. At some time, the molecules were surrounded by membranes, which made cells.
Law
Law is a set of rules decided by a particular place or authority meant for the purpose of keeping the peace and security of society.
Courts or police may enforce this system of rules and punish people who break the laws, such as by paying a fine, or other penalty including jail. In ancient societies, laws were written by leaders, to set out rules on how people can live, work and do business with each other. But many times in history when laws have been on a false basis to benefit few at the expense of society, they have resulted in conflict. To prevent this, in most countries today, laws are written and voted on by groups of politicians in a legislature, such as a parliament or congress, elected (chosen) by the governed peoples. Countries today have a constitution for the overall framework of society and make further laws as needed for matters of detail. Members of society generally have enough freedom within all the "legal" things they can choose to do. An activity is "illegal" if it breaks a law or does not follow the laws.
A legal code is a written code of laws that are enforced. This may deal with things like police, courts, or punishments. A lawyer, jurist or attorney is a professional who studies and argues the rules of law. In the United States, there are two kinds of attorneys - "transactional" attorneys who write contracts and "litigators" who go to court. In the United Kingdom, these professionals are called solicitors and barristers respectively.
The "Rule of Law" is the law which says that government can only legally use its power in a way the government and the people agree on. It limits the powers a government has, as agreed in a country's constitution. The "Rule of Law" prevents dictatorship and protects the rights of the people. When leaders enforce the legal code honestly, even on themselves and their friends, this is an example of the rule of law being followed. "The rule of law", wrote the ancient Greek philosopher Aristotle in 350 BC, "is better than the rule of any individual."
Culture is usually a major source of the principles behind many laws, and people also tend to trust the ideas based on family and social habits. In many countries throughout history, religion and religious books like the Vedas, Bible or the Koran have been a major source of law.
Civil law is the legal system used in most countries around the world today. Civil law is based on legislation that is found in constitutions or statutes passed by government. The secondary part of civil law is the legal approaches that are part of custom. In civil law governments, judges do not generally have much power, and most of the laws and legal precedent are created by Members of Parliament.
Common law is based on the decisions made by judges in past court cases. It comes from England and it became part of almost every country that once belonged to the British Empire, except Malta, Scotland, the U.S. state of Louisiana, and the Canadian province of Quebec. It is also the predominant form of law in the United States, where many laws called statutes are written by Congress, but many more legal rules exist from the decisions of the courts. Common law had its beginnings in the Middle Ages, when King John was forced by his barons to sign a document called the Magna Carta.
Religious law is law based on religious beliefs or books. Examples include the Jewish Halakha, Islamic Sharia, and Christian Canon law.
Until the 1700s, Sharia law was the main legal system throughout the Muslim world. In some Muslim countries such as Saudi Arabia and Iran, the whole legal systems still base their law on Sharia law. Islamic law is often criticised because it often has harsh penalties for crimes. A serious criticism is the judgement of the European Court that "sharia is incompatible with the fundamental principles of democracy".
The Turkish Refah Party's sharia-based "plurality of legal systems, grounded on religion" was ruled to contravene the European Convention for the Protection of Human Rights and Fundamental Freedoms. The Court decided Refah's plan would "do away with the State's role as the guarantor of individual rights and freedoms" and "infringe the principle of non-discrimination between individuals as regards their enjoyment of public freedoms, which is one of the fundamental principles of democracy".
The history of law is closely connected to the development of human civilizations. Ancient Egyptian law developed in 3000 BC. In 1760 BC King Hammurabi, took ancient Babylonian law and organized it, and had it chiseled in stone for the public to see in the marketplace. These laws became known as the Code of Hammurabi.