For instance, around 25,000–27,000 species of nematodes have been described, while published estimates of the total number of nematode species include 10,000–20,000; 500,000; 10 million; and 100 million. The following table lists estimated numbers of described extant species for the major animal phyla, along with their principal habitats (terrestrial, fresh water, and marine), and free-living or parasitic ways of life. The blue whale (Balaenoptera musculus) is the largest animal that has ever lived, weighing up to 190 tonnes and measuring up to 33.6 metres (110 ft) long. Vertebrates such as the lobe-finned fish Tiktaalik started to move on to land in the late Devonian, about 375 million years ago. Some benthic animals living close to hydrothermal vents and cold seeps on the dark sea floor consume organic matter produced through chemosynthesis (via oxidising inorganic compounds such as hydrogen sulfide) by archaea and bacteria.
Most animals rely on biomass and bioenergy produced by plants and phytoplanktons (collectively called producers) through photosynthesis. Selective pressures imposed on one another lead to an evolutionary arms race between predator and prey, resulting in various antagonistic/competitive coevolutions. In carnivorous or omnivorous species, predation is a consumer–resource interaction where the predator feeds on another organism, its prey, who often evolves anti-predator adaptations to avoid being fed upon. These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula.

• Relative to gross domestic product, Japan’s research and development budget is the sixth or seventh highest in the world, with 907,400 researchers sharing a 22-trillion-yen research and development budget as of 2023update.
• People without insurance through employers can participate in a national health insurance program administered by local governments.
• The United States is a major market for Japanese exports and a major source of Japanese imports, and is committed to defending the country, with military bases in Japan.
• Popular Japanese beverages include sake, a brewed rice beverage that typically contains 14–17% alcohol and is made by multiple fermentation of rice.
• It underwent rapid economic growth in the following decades and became one of the first major non-NATO allies of the U.S.
• Japan has the second highest number of researchers in science and technology per capita in the world with 14 per 1000 employees.
• The animal kingdom is divided into five major clades, namely Porifera, Ctenophora, Placozoa, Cnidaria and Bilateria.

Having a front end means that this part of the body encounters stimuli, such as food, favouring cephalisation, the development of a head with sense organs and a mouth. The digestive chamber has two openings, a mouth and an anus, and in the Nephrozoa there is an internal body cavity, a coelom or pseudocoelom. Most members of Medusozoa, including jellyfish and most hydrozoans, have a polyp form as well, but also have a motile medusae stage. Members of the group Anthozoa, such as sea anemones, coral, and sea pens only are sessile polyps. Sponges lack the complex organisation found in most other animal phyla; their cells are differentiated, but in most cases not organised into distinct tissues, unlike all other animals.
Japan is an ethnically and culturally homogeneous society, with the Japanese people forming 97.4% of the country’s population. On April 1, 2019, Japan enacted its revised immigration law, protecting the rights of foreign workers to help reduce labor shortages in certain sectors. The country has therefore aimed to diversify its sources and maintain high levels of energy efficiency. The high-speed Shinkansen (bullet trains) that connect major cities are known for their safety and punctuality. The explorer entered a lunar orbit on October 4, 2007, and was deliberately crashed into the Moon on June 11, 2009. Japan’s plans in space exploration include building a Moon base and landing astronauts by 2030.
In the classical era, Aristotle divided animals,d based on his own observations, into those with blood (roughly, the vertebrates) and those without. The chordates are dominated by the vertebrates (animals with backbones), which consist of fishes, amphibians, reptiles, birds, and mammals. Most protostomes have schizocoelous development, where cells simply fill in the interior of the gastrula to form the mesoderm. Most appear to belong to two major lineages, the protostomes and the deuterostomes.
The Ryukyu Islands, which include Okinawa, are a chain to the south of Kyushu. The country’s five main islands, from north to south, are Hokkaido, Honshu, Shikoku, Kyushu and Okinawa. On March 11, 2011, Japan suffered the Tōhoku earthquake—the largest by magnitude in its recorded history—which, along with the ensuing tsunami, triggered the Fukushima nuclear accident. The war cost Japan millions of lives and many of its conquered territories, including de jure parts of Japan such as Korea, Taiwan, Karafuto, and the Kurils.

Law enforcement

Popular Japanese beverages include sake, a brewed rice beverage that typically contains 14–17% alcohol and is made by multiple fermentation of rice. Japanese cuisine offers a vast array of regional specialties that use traditional recipes and local ingredients. Beginning in 2000, Japan implemented the Happy Monday System, which moved a number of national holidays to Monday in order to obtain a long weekend. Public holidays in Japan are regulated by the Public Holiday Law (国民の祝日に関する法律, Kokumin no Shukujitsu ni Kansuru Hōritsu) of 1948.

Crappie Fish

After being defeated in the Pacific War and suffering the U.S. atomic bombings of Hiroshima and Nagasaki, Japan surrendered in 1945 and came under Allied occupation until 1952. The Meiji period saw Japan pursue rapid industrialization, modernization, militarism, and overseas colonization. Between the 4th and 6th centuries, its kingdoms were united under an emperor in Nara and later in Heian-kyō. With a population of almost 123 million as of 2026, it is the world’s 11th most populous country.

• Also, the cells of animals have different cell membranes to other eukaryotes like plants and fungi.
• Japan is the second highest-ranked Asian country in the 2025 Global Peace Index.
• Since 1973, all elderly persons have been covered by government-sponsored insurance.
• However, Japan’s video game sector remains a major industry; in 2014, Japan’s consumer video game market grossed $9.6 billion, with $5.8 billion coming from mobile gaming.
• Statutory law originates in the legislature, and the constitution requires that the emperor promulgate legislation passed by the Diet without giving him the power to oppose legislation.
• In 1185, following the defeat of the Taira clan by the Minamoto clan in the Genpei War, samurai Minamoto no Yoritomo established a military government at Kamakura.
• For example, adult echinoderms are radially symmetric (unlike their larvae), while some parasitic worms have extremely simplified body structures.

The Reform began with land reform, based on Confucian ideas and philosophies from China. Japan first appears in written history in the Chinese Book of Han, completed in 111 AD, where it is described as having a hundred small kingdoms. The Japonic-speaking Yayoi people later entered the archipelago from the Korean Peninsula, intermingling with the Jōmon people. The old Malay name for Japan, Japang or Japun, was borrowed from a southern coastal Chinese dialect and encountered by Portuguese traders in Southeast Asia, who brought the word to Europe in the early 16th century. The name “Japan” is based on Min or Wu Chinese pronunciations of 日本 and was introduced to European languages through early trade.

The earliest works of Japanese literature include the Kojiki and Nihon Shoki chronicles and the Man’yōshū poetry anthology, all from the 8th century and written in Chinese characters. Japan has the lowest rate of heart disease in basswin the OECD, and the lowest level of dementia among developed countries. Since 1981, the principal cause of death in Japan is cancer, which accounted for 27% of the total deaths in 2018—followed by cardiovascular diseases, which led to 15% of the deaths.
However, these estimates are based on people affiliated with a temple, rather than the number of true believers. Japanese Sign Language is the primary sign language used in Japan and has gained some official recognition, but its usage has been historically hindered by discriminatory policies and a lack of educational support. English has taken a major role in Japan as a business and international link language, and is a compulsory subject at the junior and senior high school levels. Japanese writing uses kanji (Chinese characters) and two sets of kana (syllabaries based on cursive script and radicals used by kanji), as well as the Latin alphabet and Arabic numerals. The Japanese language is Japan’s de facto national language and the primary written and spoken language of most people in the country.