100 Fun Facts About 7th Grade

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

The nickname was popularized by a 1957 Scientific American article; the energy-releasing reactions happen on the folded inner membrane.

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

The gas is pulled in through tiny pores called stomata, and the oxygen we breathe is the leftover from the process.

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

He tracked seven traits, including seed shape and flower colour, across roughly 28,000 plants in a monastery garden.

What is the basic unit of heredity called?

Each one is a stretch of DNA, and humans carry roughly 20,000 of them coding for proteins.

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

The iron-rich molecule hemoglobin inside them grabs the oxygen, and it is also what makes blood look red.

What is the largest organ of the human body?

It makes up around 16 percent of body mass and is the outer layer of the integumentary system.

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

Unlike plants they cannot photosynthesize, and their cell walls are made of chitin, the same material as an insect's shell.

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

In butterflies the resting stage is called a chrysalis, and some moths remember things they learned as caterpillars.

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

It sits outside the membrane, and its stiffness is what lets a plant stem stand up without a skeleton.

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

Scientists prefer terms like endothermic and homeothermic, since some fish and even a few insects can heat themselves too.

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

Watson and Crick proposed it in 1953, relying heavily on X-ray images made by Rosalind Franklin and Raymond Gosling.

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

The Sun helps too: when the Sun, Moon and Earth line up at new and full moon, the extra-large tides are called spring tides.

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

Swirling currents in that molten metal are what generate Earth's magnetic field, the reason compasses point north.

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

Granite is the slow-cooled underground kind; basalt and obsidian form when lava cools quickly at the surface.

Which planet is the largest in our solar system?

More than 1,300 Earths could fit inside it, and its Great Red Spot is a storm bigger than our whole planet.

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

Lower numbers are acids like lemon juice, higher numbers are bases like baking soda solution, and each step is a tenfold change.

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

Oxygen is only about 21 percent; the third-biggest ingredient, argon, is under one percent.

What is the longest bone in the human body?

It runs from hip to knee, and by some measures it is also the strongest bone you have.

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

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?

The exterior angles, one at each corner, add up to 360 degrees instead, and that is true for every convex polygon.

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 that is larger than a right angle but smaller than a straight angle is called what?

The word comes from Latin for "blunt"; angles under 90 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?

With an even number of values there is no single center, so you average the two middle numbers.

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

The similar-looking 2πr is the distance around the circle, its circumference, not the space inside.

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

When the two quantities have different units, like miles and hours, the comparison is usually called a rate instead.

In which Italian city did the Renaissance begin?

The wealthy Medici family paid for much of the art, and Greek scholars fleeing the fall of Constantinople brought ancient texts with them.

Which German inventor built Europe's first movable-type printing press in the 1400s?

Movable type already existed in East Asia, but his press, oil-based ink and metal type made mass-producing books practical.

Which English king sealed the Magna Carta in 1215?

Rebel barons forced it on him at Runnymede; 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 city is modern Istanbul; its fall is often used as the date marking the end of the Middle Ages.

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

They trained in the military arts from childhood, and under the Tokugawa peace they gradually became hereditary administrators.

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

He began preaching publicly in Mecca in 613, and within a century of his death the faith stretched from Spain to Central Asia.

The Black Death swept through Europe during which century?

The plague pandemic ran from 1346 to 1353 and killed a large share of the continent's population.

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

His name means "Charles the Great", and his empire covered much of western Europe.

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

It was built around 1450, likely as an estate for the emperor Pachacuti, using stones cut so precisely no mortar was needed.

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

He himself was killed in the Philippines in 1521; Juan Sebastián Elcano brought the one surviving ship home to Spain.

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

He was a theology professor at Wittenberg, and his complaint was the church selling indulgences.

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

Causeways linked it to the shore, and Mexico City now stands on the drained lakebed.

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

He gave away so much gold along the way that some accounts say prices in Cairo were disrupted for years.

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

Pope Urban II made the call at the Council of Clermont, promising spiritual rewards to those who went.

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

His book gave Europeans their first detailed look at China, Persia and Japan, and many readers refused to believe it.

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

The Texians lost the fort but won independence six weeks later at San Jacinto.

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

It runs about 7,088 km through northeastern Africa, though the Amazon carries far more water.

Which continent contains the most countries, with 54?

Most of them kept the borders drawn during the colonial era when they became independent.

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

It is about 40,075 km around and splits Earth into the Northern and Southern Hemispheres.

What is the largest hot desert in the world?

Only the cold deserts of Antarctica and the Arctic are bigger; it covers about 9.2 million square kilometres of North Africa.

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

It spans eleven time zones and shares land borders with fourteen countries.

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

The range runs north to south through Russia, separating European Russia from Siberia.

What is the capital city of Australia?

It was purpose-built as a compromise between rivals Sydney and Melbourne, and sits in its own territory.

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

He is a 14-year-old greaser in Tulsa, and Hinton was still a teenager herself when she wrote the book.

"The wind whispered through the trees" is an example of which figure of speech?

Giving a non-human thing human qualities is one of the oldest devices in poetry; 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?

"Brave as a lion" is one; drop the "as" and say "he is a lion" and it becomes a metaphor.

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

Cassie is nine, living in 1930s Mississippi, and the book is one of a whole series about the family.

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

It opens the Time Quintet, and the author based the Murry family on her own.

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

Words of this type can also modify adjectives and each other, as in "very loudly".

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

Her family hid in a secret annex behind her father's business from 1942 until they were discovered in 1944.

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

Traditional ones also include a seasonal reference and a "cutting word" that creates a pause.

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

They were ratified in 1791; the Constitution as a whole now has 27 amendments.

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

The other two are the executive, headed by the president, and the legislative, which is Congress.

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

It did not have to be land; the right to run a mill, collect a tax or hunt in a forest could all be granted the same way.

Which artist painted the Mona Lisa?

He worked on it from about 1503 and may still have been touching it up as late as 1517.

The trumpet belongs to which family of musical instruments?

Its tubing has been made of that metal since the late 1400s and is bent twice into a rounded rectangle.

How many keys does a standard modern piano have?

Fifty-two are white and thirty-six are black, covering just over seven octaves.

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

It covers more area than all the land on Earth combined, and the Mariana Trench in its west is the deepest spot on the planet.

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

Its summit marks the frontier; the Nepali name is Sagarmatha and the Tibetan name is Qomolangma.

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

It is about 2,900 km thick and, though mostly solid rock, it flows very slowly over millions of years, which drives 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?

Babies are born with around 270 bones, but many fuse together as they grow.

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

Chlorophyll inside them absorbs red and blue light and reflects green, which is why leaves look green.

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

The law says a body stays at rest or in uniform motion unless a force acts on it.

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

The Pythagorean theorem says the square on that side equals the sum of the squares on the other two.

What is the capital city of Canada?

Toronto is the largest city, but the federal capital sits in Ontario on the Quebec border.

Which river is the longest in the United States?

It flows 2,341 miles from Montana into the Mississippi, which it slightly outstrips in length.

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

The Preamble sets out the Constitution's purposes and guiding principles.

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

They met at the Pennsylvania State House in Philadelphia, later renamed Independence Hall.

Which colours of light does chlorophyll mainly absorb?

Because it reflects green light, plants look green to us.

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

Evaporation, transpiration, condensation, precipitation and runoff are among the fluxes that move water around Earth.

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

By contrast, mid-ocean ridges like the Mid-Atlantic Ridge have volcanoes where plates pull apart.

Which planet is closest to the Sun?

It is also the smallest planet in the Solar System, and from Earth it is only ever seen near the Sun as a morning or evening star.

Which country is the largest in South America by area?

It is the fifth-largest country on Earth and the only Portuguese-speaking nation in the Americas.

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

The word comes from the Greek for 'opponent' or 'competitor', and the role does not have to be a person: a storm or a society can fill it.

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

British and Canadian students learn the same idea as BODMAS or BEDMAS, where the B stands for brackets.

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

Everyday words such as 'cough' and 'pigeon' probably started out as sound imitations too, even though speakers no longer hear them that way.

Who united the Mongol tribes and founded the Mongol Empire?

After uniting the tribes he conquered large parts of China and Central Asia, building the foundation of 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?

It is why a rocket moves: the engine pushes exhaust gas backward, and the gas pushes the rocket forward with equal force.

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

Rather than swallowing food, they release digestive enzymes directly onto it and then absorb the broken-down nutrients.

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?

Dry ice is frozen carbon dioxide, and at ordinary air pressure it skips the liquid stage entirely, which is why it never leaves a puddle.

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

The book won the Newbery Medal in 1994 and is frequently challenged in schools for its themes of euthanasia and control.

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

Its creator simply called it a 'magnitude scale'; seismologists today mostly use the moment magnitude scale, which gives similar numbers.

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

At its narrowest the channel is only about 13 kilometres wide, so Africa is clearly visible from the Spanish shore on a fine day.

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

The Greek astronomer Aristarchus had proposed a Sun-centred model eighteen centuries earlier, but the idea did not catch on until the Renaissance.

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

The full title means 'Commander-in-Chief of the Expeditionary Force Against the Barbarians', and it was nominally granted by the emperor.

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

He tested it on James Phipps, his gardener's eight-year-old son, using material from a milkmaid's cowpox sores.

What is the SI unit of energy?

One food calorie on a nutrition label is 4,184 of them, and a kilowatt-hour of electricity is 3.6 million.

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

Suryavarman II built it as a Hindu temple to Vishnu; it later became Buddhist and is today the largest religious complex in the world.

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

Born enslaved in French Saint-Domingue, he was nearly 50 when the revolt began; the colony declared independence in 1804, a year after his death.

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

He seized the throne from Sunni Ali's son, arguing the heir was not a faithful Muslim, and pushed the empire east as far as Kano.