100 Fun Facts About 7th Grade

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

The mitochondrion is the 'powerhouse of the cell', a nickname popularized by Philip Siekevitz's 1957 Scientific American article; its folded inner membrane hosts the energy-releasing reactions that make ATP.

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

Plants take in carbon dioxide through tiny leaf pores called stomata and combine it with water, using light energy, to make glucose; the oxygen we breathe is the by-product.

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

Mendel used peas; in his monastery garden at Brno he tracked seven traits, such as seed shape and flower colour, across roughly 28,000 pea plants.

What is the basic unit of heredity called?

A gene is the basic unit of heredity: a stretch of DNA that codes for a protein or RNA, and humans carry roughly 20,000 protein-coding genes.

Which type of blood cell carries oxygen from the lungs to the rest of the body?

Red cells (erythrocytes) carry oxygen: the iron-rich protein hemoglobin inside them binds oxygen in the lungs and releases it in the tissues, and it gives blood its red colour.

What is the largest organ of the human body?

The skin is the largest organ, making up about 16 percent of body mass; it is the main part of the integumentary system, with the liver the largest internal organ.

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

Mushrooms, yeasts and molds are Fungi: unlike plants they cannot photosynthesize, and their cell walls are made of chitin, the same material as an insect's exoskeleton.

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

Metamorphosis is the transformation from larva to adult; a caterpillar enters a resting stage called a chrysalis, inside which its body is rebuilt into a butterfly.

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

The cell wall, made mainly of cellulose, sits outside the plant cell membrane; its stiffness lets a stem stand upright without a skeleton, and animal cells have none.

What are animals like birds and mammals called, which keep a steady body temperature?

Warm-blooded animals keep a steady internal temperature; scientists prefer the terms endothermic and homeothermic, since tuna and even bumblebees can also heat parts of their bodies.

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

DNA is a double helix: two strands twisted around each other like a spiral ladder, a structure Watson and Crick proposed in 1953 using X-ray images made by Rosalind Franklin and Raymond Gosling.

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 generate 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 forms from cooled magma or lava: granite is the slow-cooled underground kind, while basalt and obsidian form when lava cools quickly at the surface.

Which planet is the largest in our solar system?

Jupiter is the largest planet: more than 1,300 Earths could fit inside it, and its mass is about two and a half times that of all the other planets combined.

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

Pure water is pH 7, the neutral point; lower numbers are acids like lemon juice, higher numbers are bases like baking-soda solution, and each step is a tenfold change in acidity.

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

Nitrogen makes up about 78 percent of the atmosphere; oxygen is about 21 percent, and the third-biggest ingredient, argon, is under one percent.

What is the longest bone in the human body?

The femur, or thigh bone, runs from hip to knee and is about a quarter of a person's height, making it the longest and, by most measures, strongest bone.

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

Pi is 3.14159..., so 3.14 to two decimal places; it is the ratio of any circle's circumference to its diameter, and its digits go on forever without repeating.

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

A triangle's interior angles always total 180 degrees, which is why a right triangle's other two angles add to 90; the exterior angles of any convex polygon total 360 degrees.

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

The number 2 is the only even one; every other even number can be divided by 2.

What is 25 percent of 200?

Percent means "per hundred", so 25 percent is a quarter, and a quarter of 200 is 50.

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

Each face is equally likely, so every single number has the same one-in-six chance on each roll, no matter what came before.

An angle measuring more than 90 but less than 180 degrees is called what?

An obtuse angle measures between 90 and 180 degrees; the word comes from the Latin obtusus, 'blunt', while angles under 90 degrees are acute, meaning sharp.

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 the middle value of an ordered list; with an even number of values you average the two middle numbers, unlike the mean, which averages them all.

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

Area = πr²; a circle of radius 2 has area 4π, about 12.57. The similar-looking 2πr is the circumference, the distance around the circle, not the space inside.

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

A ratio compares two quantities of the same kind, such as 3 to 2, written 3:2 or 3/2; when the units differ, like miles and hours, the comparison is usually called a rate.

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 built his press in Mainz around 1450; movable type already existed in East Asia, but his metal type, oil-based ink and press made mass-producing books practical.

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, the eastern continuation of Rome, ruled from Constantinople for over a thousand years until Mehmed II took the city in 1453; it is modern Istanbul.

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.

Which religion did the prophet Muhammad found in the 7th century?

Muhammad founded Islam, receiving his first revelation near Mecca in 610 and preaching publicly from 613; within a century of his death in 632 the faith stretched from Spain to Central Asia.

The Black Death swept through Europe during which century?

The Black Death struck in the 14th century, sweeping Europe from 1347 to 1351 after arriving by ship from the Black Sea; it killed perhaps a third or more of Europe's population.

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

Charlemagne, whose name means 'Charles the Great', was crowned emperor by Pope Leo III in St Peter's on Christmas Day 800; his empire covered much of western Europe.

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

The Inca built Machu Picchu around 1450, probably as an estate for the emperor Pachacuti, fitting its stones so precisely that no mortar was needed.

Whose expedition completed the first voyage all the way around the world in 1522?

Ferdinand Magellan led the expedition that left Spain in 1519; he was killed in the Philippines in 1521, and Juan Sebastián Elcano brought the one surviving ship, Victoria, home in 1522.

In what year did Martin Luther write his Ninety-five Theses, starting the Protestant Reformation?

Luther wrote the Ninety-five Theses in 1517, traditionally posted on the Wittenberg castle church door on 31 October; a theology professor there, he attacked the church's sale of indulgences.

The Aztec capital Tenochtitlan was built on an island in which lake?

Tenochtitlan rose on an island in Lake Texcoco from 1325, linked to the shore by causeways; the Spanish later drained the lake, and Mexico City was built on its bed.

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

Pope Urban II called the First Crusade at the Council of Clermont in 1095 to retake Jerusalem, which the crusaders captured in July 1099.

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

Marco Polo served Kublai Khan, founder of the Yuan dynasty, for about 17 years from 1275; his book later gave Europeans a detailed account of China and an early description of Japan.

The Battle of the Alamo, a key event in the Texas Revolution, took place in which year?

The Alamo fell on March 6, 1836, after a 13-day siege; the Texians lost the fort but won independence six weeks later at San Jacinto on April 21, 1836.

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

The Nile, at about 6,650 km, is generally listed as the world's longest river, flowing north through Egypt into the Mediterranean; the Amazon is a close rival and carries far more water.

Which continent contains the most countries?

Africa has 54 countries, more than any other continent; most kept the borders drawn by European powers in the late 1800s when they won independence, mainly in the 1950s and 1960s.

What is the name of the imaginary line at zero latitude, halfway between the poles?

The Equator is the line of 0° latitude; it is about 40,075 km around and splits Earth into the Northern and Southern Hemispheres, passing through Ecuador, Kenya and Indonesia.

What is the largest hot desert in the world?

The Sahara covers about 9.2 million square kilometres of North Africa, roughly the size of the United States; only the cold polar deserts of Antarctica and the Arctic are larger.

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

Russia is the largest country, covering about 17.1 million square kilometres, far ahead of second-place Canada; it spans eleven time zones and borders fourteen countries.

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

The Urals run roughly north to south for about 2,500 km through Russia, separating European Russia from Siberia, and have marked the Europe–Asia boundary by convention since the 1700s.

What is the capital city of Australia?

Canberra was purpose-built as a compromise between rivals Sydney and Melbourne; chosen in 1908 and designed by Walter Burley Griffin, it sits in the Australian Capital Territory.

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

Ponyboy Curtis, a 14-year-old greaser, narrates the story, which is framed as his English-class essay; S. E. Hinton began the book at 15 and published it in 1967 at 18.

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

Personification gives a non-human thing human qualities, such as flowers dancing; it is one of the oldest devices in poetry, and whole cities and seasons have been written as people.

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

A simile uses 'like' or 'as': 'brave as a lion' is one, and dropping the 'as' to say 'he is a lion' turns it into a metaphor.

In Mildred D. Taylor's Roll of Thunder, Hear My Cry, what is the surname of narrator Cassie's family?

Cassie Logan, aged nine, narrates life on her family's own land in 1930s Mississippi; the Logans feature in a whole series by Taylor, including Let the Circle Be Unbroken.

Who wrote A Wrinkle in Time, the novel about Meg Murry's search for her missing father?

Madeleine L'Engle published A Wrinkle in Time in 1962 after some 26 publishers rejected it; it won the 1963 Newbery Medal and opens her Time Quintet.

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

'Loudly' is an adverb: it modifies the verb 'sang', telling how she sang. Adverbs, often ending in -ly, can also modify adjectives or other adverbs, as in 'very loudly'.

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

In Amsterdam the Frank family hid in a secret annex behind Otto Frank's business at Prinsengracht 263 from July 1942 until their arrest in August 1944.

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

A haiku runs 5-7-5: five syllables, then seven, then five, for 17 in all; traditional ones also include a seasonal word (kigo) and a 'cutting word' (kireji) that creates a pause.

How many amendments make up the United States Bill of Rights?

The Bill of Rights is the first 10 amendments, ratified in 1791; Congress had sent 12 to the states, and one of the two left over became the 27th Amendment in 1992.

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

The Supreme Court heads the judicial branch, which interprets the laws; the executive, led by the president, carries them out, and the legislative branch, Congress, writes them.

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

A fief (Latin feudum, the root of 'feudalism') was the grant a vassal held in return for homage and service; it did not have to be land, as mills, tolls and hunting rights were granted the same way.

Which artist painted the Mona Lisa?

Leonardo da Vinci began the Mona Lisa in Florence around 1503 and may have kept retouching it until about 1517; King Francis I of France acquired it after the artist's death in 1519.

The trumpet belongs to which family of musical instruments?

The trumpet is a brass instrument: its sound is made by buzzing the lips into a cup mouthpiece, and its roughly 1.5 metres of brass tubing is folded into a compact oblong.

How many keys does a standard modern piano have?

A standard piano has 88 keys, 52 white and 36 black, spanning just over seven octaves from A0 to C8; Steinway settled on that range in the 1880s.

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

The Pacific covers about 165 million square kilometres, more than all Earth's land combined, and its Mariana Trench, near Guam, reaches about 11,000 metres, the deepest point on the planet.

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

Everest's summit straddles the Nepal–China border, with the Tibet Autonomous Region on the Chinese side; the Nepali name is Sagarmatha and the Tibetan name Qomolangma.

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

Aurum is Latin for gold; many element symbols come from Latin names.

About how many bones does an adult human skeleton have?

An adult skeleton has about 206 bones; babies are born with around 270, but many, such as those of the skull and spine, fuse together during growth.

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

Chloroplasts are the organelles where photosynthesis happens; they are packed with the green pigment chlorophyll and stacked membranes called thylakoids, and a single leaf cell may hold dozens of them.

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

Inertia is the tendency of a body to resist changes in its motion; Newton's first law says a body stays at rest or in uniform straight-line motion unless a net force acts on it.

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

The hypotenuse is the longest side of a right triangle, opposite the right angle; the Pythagorean theorem says its square equals the sum of the squares of the other two sides, as in 3-4-5.

What is the capital city of Canada?

Ottawa, chosen as capital by Queen Victoria in 1857, sits in Ontario on the Quebec border; Toronto is Canada's largest city but not its capital.

Which river is the longest in the United States?

The Missouri is the longest US river at about 2,341 miles, flowing from the Rocky Mountains in Montana to join the Mississippi near St. Louis; the Mississippi itself is a mile or so shorter.

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

The Constitution's Preamble begins 'We the People of the United States'; drafted in 1787 and ratified in 1788, it sets out the document's purposes, such as forming 'a more perfect Union'.

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

The Second Continental Congress, meeting at the Pennsylvania State House in Philadelphia (later Independence Hall), voted for independence on July 2 and adopted Jefferson's Declaration on July 4, 1776.

Which colours of light does chlorophyll mainly absorb?

Chlorophyll absorbs mainly red and blue light, the two peaks of its absorption spectrum, and reflects green, 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 water vapour cooling back into liquid droplets, which is how clouds and dew form; evaporation is the reverse, and precipitation returns the water to the ground.

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

The Ring of Fire's volcanoes sit above convergent boundaries, where an oceanic plate subducts beneath another and drives melting above it; by contrast, mid-ocean ridges such as the Mid-Atlantic Ridge form where plates pull apart.

Which planet is closest to the Sun?

Mercury orbits the Sun at an average of about 58 million km, closer than any other planet; it is also the smallest planet and is only ever seen near the Sun, as a morning or evening star.

Which country is the largest in South America by area?

Brazil covers about 8.5 million square kilometres, nearly half of South America and fifth-largest on Earth; it is also the only Portuguese-speaking nation in the Americas.

In a story, what is the character who opposes the main character called?

The antagonist opposes the protagonist; the word comes from the Greek antagonistes, 'opponent', and the role need not be a person: a storm or a whole society can fill it.

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

E is for Exponents: PEMDAS runs Parentheses, Exponents, Multiplication and Division, Addition and Subtraction. British and Canadian students learn the same order as BODMAS or BEDMAS, with B for brackets.

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

Onomatopoeia is a word that imitates its sound, like 'buzz' or 'splash'; everyday words such as 'cough' and even 'pigeon' (from Latin pipire, 'to chirp') began as sound imitations too.

Who united the Mongol tribes and founded the Mongol Empire?

Genghis Khan, born Temüjin, was proclaimed ruler of all the Mongols in 1206; he then conquered northern China and Khwarezm, founding what became the largest contiguous land empire in history.

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?

Decomposers such as fungi and bacteria break down dead matter; rather than swallowing food, they release digestive enzymes onto it and absorb the nutrients, returning them to the soil.

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

The levels of organisation run cell, tissue, organ, organ system, organism; the heart is an organ built from several tissues.

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

Sublimation is a solid turning straight into gas; dry ice, frozen carbon dioxide, does this at about −78 °C under ordinary air pressure, skipping the liquid stage, which is why it never leaves a puddle.

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

Lois Lowry wrote The Giver, which won the 1994 Newbery Medal, her second after Number the Stars in 1990; it is frequently challenged in schools for its themes of euthanasia and control.

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

Charles Richter devised the Richter scale at Caltech in 1935, calling it simply a 'magnitude scale'; each whole number is a tenfold increase in measured ground motion, and seismologists later moved to the moment magnitude scale.

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

The Strait of Gibraltar is only about 13–14 km wide at its narrowest, so Morocco's coast is clearly visible from Spain on a fine day; it is the Mediterranean's only natural outlet to the Atlantic.

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

Nicolaus Copernicus published De revolutionibus orbium coelestium in 1543, the year he died; the Greek astronomer Aristarchus had proposed a Sun-centred model eighteen centuries earlier, but it never caught on.

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

The shogun's full title, Sei-i Taishōgun, means 'Commander-in-Chief of the Expeditionary Force Against the Barbarians'; Minamoto no Yoritomo received it in 1192, and the last shogun resigned in 1867.

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

Jenner's 1796 smallpox vaccine used material from milkmaid Sarah Nelmes's cowpox sores, tested on James Phipps, his gardener's eight-year-old son; smallpox was declared eradicated in 1980.

What is the SI unit of energy?

The joule, named after James Prescott Joule, is the SI unit of energy; one food Calorie is 4,184 joules and a kilowatt-hour of electricity is 3.6 million, while the watt measures power.

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 the most prominent leader of a revolution in which Caribbean colony?

Haiti, then the French colony of Saint-Domingue, rose in 1791; Louverture, born enslaved, was nearly 50 when the revolt began, and the colony declared independence as Haiti in 1804, a year after his death.

Askia the Great ruled which West African empire from 1493 to 1528?

Askia Muhammad ruled the Songhai Empire from Gao; he seized the throne from Sunni Ali's son in 1493, arguing the heir was not a faithful Muslim, and pushed Songhai's reach east to the Hausa city of Kano.