99 Fun Facts About 7th Grade

Which organelle is nicknamed the "powerhouse of the cell"?

The mitochondrion has its own DNA, a leftover of its likely origin as a free-living bacterium that an ancient cell engulfed.

Along with water and light, what do plants need to make their own food through photosynthesis?

Plants combine carbon dioxide from the air with water, using light energy, to make glucose, and release the oxygen we breathe as a by-product.

Gregor Mendel worked out the basic rules of inheritance by breeding which plant?

Peas made Mendel famous only after his death: his results were largely ignored until other scientists rediscovered them in 1900.

What is the basic unit of heredity called?

A gene typically comes in two copies, one inherited from each parent, so every child carries a mix of both parents' versions.

Which part of the blood carries most of the oxygen from the lungs to the rest of the body?

Red cells are packed with oxygen-carrying hemoglobin, and in mammals they shed their nucleus as they mature, leaving more room for it.

What is the largest organ of the human body?

Skin is the largest organ, and one of its jobs is making vitamin D when it is exposed to sunlight.

Mushrooms, yeasts and molds all belong to which biological kingdom?

Fungi are more closely related to animals than to plants, placed with them on the same branch of the tree of life.

A caterpillar turns into a butterfly through a process called what?

Metamorphosis inside a chrysalis starts with the caterpillar digesting itself, while surviving clusters of cells called imaginal discs build the adult wings, legs and eyes.

Which structure do plant cells have that animal cells lack, giving them their rigid shape?

The cell wall holds back water pressure inside a plant cell, and that pressure keeps a well-watered plant firm; when it drops, the plant wilts.

Which of these animals is warm-blooded, making its own body heat?

A penguin is a bird, so it makes its own body heat, and emperor penguins save that heat through Antarctic winter by huddling together.

What is the twisted-ladder shape of a DNA molecule called?

The double helix beat a rival model: the chemist Linus Pauling had proposed that DNA was a triple helix, but his structure turned out to be mistaken.

Ocean tides are caused mainly by the gravitational pull of which object?

The Moon's gravity is the main tide-raiser, being so much closer than the Sun; when Sun, Moon and Earth line up at new and full moon, the combined pull creates extra-large spring tides.

Earth's outer core is a liquid layer made mostly of nickel and which other metal?

Iron makes up most of the liquid outer core, alloyed with nickel; swirling currents in this molten iron produce Earth's magnetic field, which is why compasses point north.

Rock that forms when magma or lava cools and hardens is called what?

Igneous rock can even float: pumice forms when gas-rich lava froths and hardens so fast that it traps countless bubbles, making it light enough to float on water.

Which planet is the largest in our solar system?

Jupiter is so massive that it and the Sun both circle a shared balance point lying just outside the Sun's surface.

On the pH scale, what number is neutral, the same as pure water?

Pure water sits at pH 7, and the first commercially successful electronic pH meter grew out of a citrus chemist's request to Arnold Beckman for a sturdier way to test lemon juice.

Which gas makes up about 78 percent of Earth's atmosphere?

Nitrogen fills about 78 percent of the air, yet most living things can't use it directly; they depend largely on microbes that turn it into compounds cells can use.

What is the longest bone in the human body?

The femur tracks overall height so closely that forensic scientists can estimate a person's height from a femur alone, even when the rest of the skeleton is missing.

To two decimal places, what is the value of pi?

Pi begins 3.14, yet Indiana's House once passed a bill whose method implied pi could be 3.2, before a visiting Purdue math professor helped persuade the Senate to shelve it.

What do the three interior angles of a flat triangle add up to?

A flat triangle's angles always total 180 degrees, but on a curved surface like a ball, a triangle's angles can add up to more, as much as 540 degrees.

A whole number greater than 1 that can only be divided evenly by 1 and itself is called what?

Prime numbers help guard online secrets: a common encryption method multiplies two huge primes, and even computers can't practically undo it by factoring the product.

What is 25 percent of 200?

25 percent of 200 is 50, so cutting 200 by 25 percent leaves 150, yet raising 150 by 25 percent adds only 37.50, landing at 187.50, not back at 200.

What is the probability of rolling a 4 on a single fair six-sided die?

Each face of a fair die has a 1/6 chance on every roll, no matter what came before, so a 4 is never 'due' after a long run without one.

An angle measuring more than 90 degrees but less than a straight angle is called what?

Obtuse comes from an old word meaning 'blunt', and acute from one meaning 'sharpened', so a wide angle was named for looking blunt and a narrow one for looking pointed.

What is (-6) multiplied by (-4)?

Two negatives multiplied together always give a positive result; a negative times a positive gives a negative.

In a data set ordered smallest to largest, the value exactly in the centre is called what?

The median is often used for incomes, because raising the biggest salaries pulls the mean upward but leaves the middle value untouched.

Which formula gives the area of a circle with radius r?

πr² matches Archimedes' discovery that a circle has the same area as a right triangle whose base is the circle's circumference and whose height is its radius.

A comparison that shows how many times one quantity contains another, like 3 to 2, is called a what?

A ratio is how maps shrink the world: a scale of 1:50,000 means 1 centimeter on the map stands for 50,000 centimeters, or 500 meters, on the ground.

In which Italian city did the Renaissance begin?

Florence was the cradle of the Renaissance: its banking Medici family funded artists such as Botticelli and Michelangelo, and Brunelleschi's cathedral dome, finished in 1436, was a landmark of the new age.

Who built Europe's first movable-type printing press in the 1400s?

Johannes Gutenberg did not invent movable type, which East Asian printers had used centuries before; his press made printing far faster, bringing mass-produced books to Europe.

Which English king sealed the Magna Carta in 1215?

King John sealed Magna Carta at Runnymede on 15 June 1215 under pressure from rebel barons; it became a symbol of the idea that even a king must obey the law.

Constantinople was the capital of which empire until the Ottomans captured it in 1453?

The Byzantine Empire's capital had held off attackers for centuries behind massive walls, but the Ottomans brought giant cannons that blasted gaps in them.

In feudal Japan, the professional warrior class who served the lords were called what?

The samurai were Japan's hereditary warrior class, bound to their lords by a code later called bushido; during the peaceful Tokugawa era (1603–1868) many became administrators.

The Black Death was an outbreak of which disease?

Plague killed so many workers that survivors could demand higher wages from the landowners who now badly needed them.

Which Frankish king was crowned emperor by the pope in Rome in the year 800?

Charlemagne championed schools and scholars, yet his biographer wrote that he took up writing so late in life that practising on tablets under his pillow brought little success.

Which civilization built the mountain citadel of Machu Picchu in Peru?

The Inca built Machu Picchu, but Hiram Bingham, who brought it to world attention in 1911, wrongly believed it was the Incas' last refuge, Vilcabamba.

Whose expedition was the first to sail all the way around the world, returning to Spain in 1522?

Ferdinand Magellan led the expedition but never finished it: he was killed in the Philippines in 1521, and Juan Sebastián Elcano sailed Victoria, the only ship to complete the voyage, home.

Martin Luther's Ninety-five Theses, which sparked the Protestant Reformation, attacked the church's sale of what?

Indulgences were certificates said to reduce punishment for sins, and the sale Luther protested was raising money to rebuild St Peter's Basilica in Rome.

The Aztec capital Tenochtitlan, whose ruins lie under modern Mexico City, was built on an island in which lake?

Lake Texcoco surrounded Tenochtitlan, which reached the shore by three causeways broken by bridges, so canoes could keep passing through.

Mansa Musa, famous for his gold-laden pilgrimage to Mecca in 1324, ruled which empire?

Mansa Musa ruled the Mali Empire from about 1312 to 1337; he gave away so much gold on his 1324 pilgrimage that, by some accounts, gold prices in Cairo were depressed for years.

The First Crusade, proclaimed in 1095, aimed to capture which city?

Jerusalem fell to the crusaders in 1099, but they held it for less than a century before Saladin recaptured the city in 1187.

Venetian traveler Marco Polo spent years at the court of which Mongol ruler?

Kublai Khan sent Marco Polo on missions across his empire, and the book about those travels later inspired Christopher Columbus, who owned a heavily annotated copy.

Which former Spanish mission in San Antonio fell to Mexican troops in 1836?

The Alamo was lost, but Texians shouting 'Remember the Alamo!' later routed the Mexican army at San Jacinto in about 18 minutes.

Which river is usually listed as the longest in the world?

The Nile usually wins the title, but some researchers measure the Amazon as longer, and the Amazon carries far more water either way.

Which continent contains the most countries?

Africa's 54 countries mostly kept borders that European powers drew in the late 1800s, often straight lines that ignored the languages and peoples living there.

What is the name of the imaginary line at 0 degrees latitude?

The Equator is where Earth bulges most, so Ecuador's Mount Chimborazo, just south of the line, has the summit farthest from Earth's center, beating Everest.

What is the largest hot desert in the world?

The Sahara is only the largest hot desert: Antarctica gets so little precipitation that almost the whole continent counts as a polar desert, and it is even bigger.

Which country is the largest in the world by land area?

Russia is the largest country and was once larger still: it owned Alaska until 1867, when it sold the territory to the United States for $7.2 million.

Which mountain range is used as the traditional boundary between Europe and Asia?

The Urals are among the world's oldest mountains, some 250 to 300 million years old, yet despite long erosion they stand unusually high for their age.

What is the capital city of Australia?

Canberra was a compromise: Australia's founders put the capital in New South Wales but at least 100 miles from rival Sydney, and Parliament sat in Melbourne until it moved there in 1927.

Who narrates S. E. Hinton's novel The Outsiders?

Ponyboy Curtis narrates, and the ending reveals that the story is the English essay he writes to pass his class, since its first line is the novel's first line.

"The flowers danced in the breeze" is an example of which figure of speech?

Personification of nature once drew fire from the English critic Ruskin, who coined the term 'pathetic fallacy' to criticize writers for giving the natural world human feelings.

A figure of speech that compares two different things using "like" or "as" is called a what?

Aristotle treated a simile as a metaphor with a comparing word added, but later writers such as Quintilian turned that around, calling a metaphor a shortened simile.

Which novel follows Cassie Logan's family fighting to keep their land in 1930s Mississippi?

Roll of Thunder, Hear My Cry grew out of the family stories Mildred D. Taylor heard from her relatives, and it won the 1977 Newbery Medal.

Who wrote A Wrinkle in Time, in which Meg Murry searches for her missing father?

Madeleine L'Engle saw A Wrinkle in Time turned down by dozens of publishers, partly because a science fiction story with a girl as its hero just wasn't done then.

In the sentence "The choir sang loudly", what part of speech is the word "loudly"?

'Loudly' is an adverb telling how the choir sang, but an -ly ending is no guarantee: words such as 'friendly' and 'lovely' are adjectives.

Anne Frank wrote her famous diary while hiding from the Nazis in which city?

In Amsterdam, Anne began rewriting her diary as a book after a 1944 radio appeal from the exiled Dutch government urged people to save their wartime diaries and letters.

A traditional Japanese haiku follows which syllable pattern across its three lines?

The 5-7-5 in a Japanese haiku counts morae, sound units that don't always match syllables, so English-language haiku that count 17 syllables follow a different measure.

Which amendment protects Americans' freedom of speech and freedom of the press?

The First Amendment was third on the list of 12 amendments Congress sent to the states, but the first two were not ratified at the time, so it moved to the top.

Which branch of the US federal government includes the Supreme Court?

The judicial branch can throw out laws: in Marbury v. Madison in 1803, the Supreme Court for the first time struck down a law passed by Congress and signed by the president.

Under feudalism, what was the land or property a lord granted to a vassal in exchange for loyalty called?

A lord kept ultimate ownership of a fief and could take it back, yet fiefs often became hereditary, passing from a vassal to his heirs.

Which artist painted the Mona Lisa?

Leonardo da Vinci painted the Mona Lisa as a portrait of a silk merchant's wife but never gave it to the family; he took it to France, where King Francis I acquired it.

The trumpet belongs to which family of musical instruments?

The trumpet is brass because the player buzzes their lips into the mouthpiece, not because of its metal: the saxophone is made of brass but counts as a woodwind.

How many keys does a standard modern piano have?

A standard piano has 88 keys, but Bösendorfer's Imperial grand has 97; its extra bass keys are rarely played, and their strings mainly enrich the sound by resonating.

What is the largest and deepest of Earth's oceans?

The Pacific got its name, meaning 'peaceful', from an explorer who sailed into it after braving stormy seas and found its waters calm.

Mount Everest sits on the border between Nepal and which other country?

Everest's summit sits on the Nepal–China border, so climbers can reach the top from either country: the standard route starts in Nepal, the other from Tibet in China.

Which layer of Earth is the thickest, making up most of Earth's volume?

The mantle is about 2,900 km thick and holds roughly 84 percent of Earth's volume; though mostly solid rock, it creeps slowly over millions of years, driving plate tectonics.

The chemical symbol Au for gold comes from a word in which language?

Au comes from aurum, the Latin word for gold, and lead's symbol Pb comes from Latin plumbum, which also gave English the word 'plumber', originally a worker in lead.

About how many bones does an adult human skeleton have?

An adult skeleton has about 206 bones, yet a newborn has more, roughly 270 to 300, because many of a baby's bones fuse together as it grows.

In plants and algae, photosynthesis takes place inside which organelles?

Chloroplasts descend from bacteria: long ago a cell engulfed a photosynthetic cyanobacterium, which is why chloroplasts still carry their own DNA.

Newton's first law describes which principle, that a body keeps moving in a straight line at constant speed?

Before Newton codified inertia as his first law, Galileo reasoned that moving objects stop only because forces such as friction slow them down.

In a right triangle, what is the name of the side opposite the right angle?

Carpenters use the hypotenuse to check a corner: measure 3 units along one side and 4 along the other, and if the hypotenuse joining those marks is 5, it's a right angle.

What is the capital city of Canada?

Ottawa became the capital because rivalries between cities made any choice politically risky, so Queen Victoria was asked to decide, and she picked Ottawa, on the border of today's Ontario and Quebec.

Which river is the longest in the United States?

The Missouri was Lewis and Clark's route west: Jefferson hoped it would link by water to the Columbia River, but beyond its headwaters they found mountains to cross over land.

Which US document opens with the words 'We the People'?

The Constitution's early draft spoke of the people of the various states, and the switch to 'We the People of the United States' is often explained by doubt over which states would ratify.

Which body adopted the Declaration of Independence on July 4, 1776?

The Second Continental Congress adopted the Declaration on July 4, 1776, but its famous parchment copy wasn't signed until August 2, and some delegates added their names even later.

Which colours of light does the pigment that makes leaves green mainly absorb?

Red and blue light are what this pigment absorbs most, while much of the green light is reflected rather than absorbed, which is why leaves look green to us.

In the water cycle, what is the process by which water vapour turns back into liquid called?

Condensation is why a glass of cold water 'sweats' on a humid day: water vapour in the warm air cools against the glass and turns into drops on the outside.

The volcanoes of the Ring of Fire are caused by what kind of tectonic plate boundary?

Convergent boundaries, where one plate is forced beneath another, don't only build volcanoes: they also make the Ring of Fire home to most of the world's largest earthquakes.

Which planet is closest to the Sun?

Mercury is the planet closest to the Sun, yet it isn't the hottest: that's Venus, whose thick atmosphere traps heat.

Which country is the largest in South America by area?

Brazil became Portuguese rather than Spanish because its eastern bulge lay on Portugal's side of the line set by the 1494 Treaty of Tordesillas.

What do you call a character who opposes a story's main character?

The antagonist opposes the protagonist, but it need not be a person at all: a force such as a storm can fill the role.

In the order-of-operations acronym PEMDAS, what does the E stand for?

Exponents come before multiplying in PEMDAS, but the M doesn't outrank the D: multiplication and division share one step, worked from left to right.

Words like 'buzz' and 'splash' that imitate the sounds they describe are examples of what?

Onomatopoeia can hide inside names: 'pigeon' traces back to an old word for a young chirping bird, from a verb meaning 'to chirp'.

Who united the Mongol tribes and founded the Mongol Empire?

Genghis Khan began as an outcast: after his father was poisoned, the tribe abandoned his family, yet in 1206 the Mongols proclaimed him their ruler.

Which of Newton's laws says the forces two bodies exert on each other are equal and opposite?

Newton's third law states that every action has an equal and opposite reaction; it is why a rocket moves: the engine pushes exhaust backward, and the exhaust pushes the rocket forward with equal force.

Organisms that break down dead matter and recycle its nutrients are called what?

Many decomposers don't swallow their food: they release enzymes onto dead matter, then absorb the nutrients those enzymes free.

A group of similar cells that work together to carry out a specific function is called what?

A tissue doesn't have to be solid: blood counts as one, a connective tissue whose cells travel suspended in a watery fluid.

Dry ice turning directly from a solid into a gas is an example of which process?

Sublimation is why dry ice never leaves a puddle: at ordinary air pressure it can't melt into a liquid, so it turns straight into gas.

Who wrote The Giver, the 1993 dystopian novel set in a seemingly perfect community?

Lois Lowry's The Giver won the 1994 Newbery Medal, yet it ranked among America's most challenged books in both the 1990s and the 2000s.

Which system, introduced in 1935, rates the strength of earthquakes by magnitude?

Each step up the Richter scale means waves ten times taller on a seismogram, yet seismologists rarely use it today except for small earthquakes recorded nearby.

Which narrow channel links the Atlantic to the Mediterranean between Spain and Morocco?

The Strait of Gibraltar carries two currents at once: saltier, denser Mediterranean water flows out along the bottom, while Atlantic water flows in on top.

Whose 1543 book placed the Sun, not Earth, at the centre of the universe?

Legend has it Copernicus saw his finished book on his deathbed in 1543, yet Aristarchus of Samos had proposed a Sun-centred universe in the 3rd century BC, an idea largely rejected.

What title did Japan's military rulers hold for most of the period from 1185 to 1868?

Shogun was once only a temporary title, given to commanders for campaigns against the Emishi people, long before shoguns became Japan's real rulers.

Edward Jenner created the world's first vaccine in 1796 against which disease?

Jenner tested a country belief that catching mild cowpox protected people from smallpox: he gave a boy cowpox, later exposed him to smallpox, and no disease followed.

What is the SI unit of energy?

A joule is small, about the energy needed to lift an apple one metre, so everyday electricity is usually counted in kilowatt-hours, each worth 3.6 million joules.

Angkor Wat in Cambodia was built in the 12th century by a king of which empire?

Suryavarman II of the Khmer Empire built Angkor Wat in the early 12th century as a Hindu temple to Vishnu; it later became Buddhist and, at about 160 hectares, ranks as the world's largest religious monument.

Toussaint Louverture was a leader of the revolution that created which Caribbean country?

Haiti's revolution began in 1791, and France's failure to crush it helped push Napoleon to sell Louisiana to the United States in 1803, before Haiti declared independence in 1804.

Askia the Great ruled which empire until 1528?

Askia the Great took Songhai's throne from Sunni Ali's son, then made the pilgrimage to Mecca and came home with the title of caliph.