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WritingView an object through a microscope. Draw a picture and write a descriptive paragraph of what you see. Invite a partner to guess what you are describing.HistoryResearch the life of Antonie van Leeuwenhoek. Write a short biography about his major accomplishments and influence on the world.

Connections

Through a Microscope

A Reading A–Z Level W Leveled BookWord Count: 1,374

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Written by Cheryl Reifsnyder

LEVELED BOOK • W

Q•T•W

Through a Microscope

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How do microscopes help people learn about the world?

Focus Question

Written by Cheryl Reifsnyder

Through a Microscope

Front cover: A magnified image shows the detailed surface of a damselfly’s eye.

Title page: A magnified view of a butterfly wing shows yellow and black scales and dark-brown veins.

Page 3: A magnified view of a raised number on a credit card reveals tiny imperfections.

Photo Credits: Front cover, page 4: © Frank Fox/Science Source; title page: © Gerd Guenther/Science Source; page 3: © iStock.com/wavemovies; page 5: © SPL/Science Source; page 6: © Michael Fair/123RF; page 7: © Universal History Archive/Universal Images Group/REX/Shutterstock; page 8: © L. S. Stepanowicz/Visuals Unlimited; page 10 (left): © Visuals Unlimited; page 10 (bottom): © Manfred Kage/Science Source; page 11: © Laura J. Gardner/The Journal-Gazette/AP Images; page 12 (top): © Scott Camazine/Visuals Unlimited, Inc.; page 12 (bottom): © Perennou Nuridsany/Science Source; page 13 (left): © Dr. Richard Kessel & Dr. Gene Shih/Visuals Unlimited/Getty Images; page 13 (right): © Juergen Berger/Science Source; page 14: © Eye of Science/Science Source; page 15 (top): © De Agostini Picture Library/Science Source; page 15 (bottom): © Microscape/Science Photo Library/Getty Images

Words to Know

antennaeartificialcompoundcontaminatecrystaldistortions

electronmicroorganismsmicroscopenutrientsproductspecimens

CorrelationLEVEL W

S4040

Fountas & PinnellReading Recovery

DRA

Through a MicroscopeLevel W Leveled Book© Learning A–ZWritten by Cheryl Reifsnyder

All rights reserved.

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3

Table of Contents

Barely Visible . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

The First Simple Microscopes . . . . . . . . . . . . . . . . 5

Compound Microscopes . . . . . . . . . . . . . . . . . . . . 6

Magnified Twenty to Thirty Times (20–30x) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Magnified Fifty to Two Hundred Times (50–200x) . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Magnified Two Hundred to Fifteen Hundred Times (200–1,500x) . . . . . . . . . 11

Magnified One Million Times (1,000,000x) . . . . 14

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Through a Microscope • Level W 4

Barely Visible

A human hair—which is about one-tenth of a millimeter (0 .0039 in .) in width—is one of the smallest things the human eye can see . Imagine, though, if you could shrink yourself until that hair looked as thick as your arm . Imagine if the hair looked as fat as a tree trunk . What would you see?

The hairs on a fly’s legs would look like enormous spikes . The fly itself would look like a monster with gigantic eyes!

That’s the close-up view a microscope provides, and it changes how we see the world .

A green blowfly’s body would look very different if you could make yourself really small.

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The First Simple Microscopes

For thousands of years, people have been interested in taking a closer look at their world . The ancient Greeks used glass globes filled with water to make objects appear larger . In the first century ce, the Romans discovered how to make things appear larger with glass that was thick in the middle and thin on the edges—the first magnifying glass . When people started to figure out how to make better glass lenses in Europe in the 1600s, the microscope was invented .

At first, the microscope was just a sort of fancy magnifying glass . It had a single glass lens mounted above a holder for specimens . Most magnifying glasses only make objects appear about five to ten times (5–10x) larger in size . That was the magnifying power of the first simple microscopes .

This simple microscope from 1780 could be folded up in its case and carried in a pocket.

Through a Microscope • Level W 6

Compound Microscopes

Early microscope users figured out that they could put two magnifying glasses in line with each other to get even more magnification . The second lens magnified the image from the first lens, multiplying its power of magnification . With the combination of two lenses in a single microscope, the compound microscope was born .

The compound microscope’s total magnification is the product of the power of both of its lenses . For example, if the first lens provides ten times (10x) magnification and the second lens provides forty times (40x) magnification, the specimen will be viewed at four hundred times (400x) its actual size . Today, compound microscopes can magnify objects to make them appear up to fifteen hundred times (1,500x) larger than their actual size!

eyepiece lensbody tube

stage

mirror

base

objective lens (this microscope has three lenses of different powers to choose from)

focus knob

Parts of a Modern Compound Microscope

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Magnified Twenty to Thirty Times (20–30x)

One of the first early microscope users was a British scientist named Robert Hooke . Hooke improved the early compound microscopes, which could only magnify objects about twenty to thirty times (20–30x) their actual size . He was also one of the first people to take detailed notes on what he saw through a microscope . Hooke published his observations in 1665 in a book called Micrographia . It was the first book on microscope use written by a scientist .

In Micrographia, Hooke included drawings of close-up views of a louse and a flea . He drew the compound eyes of a fly in greater detail than anyone had ever seen before . He sketched the individual hairs that cover a fly’s body, the delicate antennae, and the complicated mouthparts .

Robert Hooke’s detailed drawing of a flea appeared in his 1665 book.

Through a Microscope • Level W 8

Hooke also sketched sections of plants and seeds . When he examined a thin section of cork under a microscope, he discovered that it was made up of hundreds of tiny chambers . He described those tiny chambers as “cells .” They reminded him of the small rooms, called cells, used by monks in a monastery . Eventually, the term cell became used to describe the tiny building blocks of all living things .

Today, examining thin slices of plants lets us see how seeds are formed . It reveals how cells make up the veins and tissues of plant leaves . It shows the cells that allow water and nutrients to move in plant stems, which helps us understand how plants live and grow .

This magnified view of a thin slice of cork shows that it is made up of many tiny “cells.”

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Magnified Fifty to Two Hundred Times (50–200x)

Historians believe that Hooke’s Micrographia inspired another early microscope user, Antonie van Leeuwenhoek (LEY-vun-hook) . Van Leeuwenhoek was a Dutch cloth merchant, not a trained scientist . However, he used magnifying glasses to examine the different types of fabric he bought and sold . When he saw Hooke’s drawings of the microscopic world, Van Leeuwenhoek started making lenses of his own .

Van Leeuwenhoek discovered a way to create better lenses . As a result, he was able to make microscopes that magnified objects to more than two hundred times (200x) their real size . He assembled more than five hundred microscopes in the late 1600s and early 1700s .

Using these stronger microscopes, Van Leeuwenhoek discovered red blood cells . He also discovered tiny life forms called microorganisms living in lake water and in the scrapings from someone’s teeth . Before Van Leeuwenhoek’s time, no one knew that microorganisms—living things too small to see with the naked eye—even existed . Microscopes revealed that microorganisms live everywhere .

Through a Microscope • Level W 10

Today, if you use a microscope in the classroom, it probably magnifies objects about the same amount as Van Leeuwenhoek’s early microscopes . Although two hundred times (200x) magnification might not seem like a lot, it’s enough to reveal details invisible to the naked eye .

Even something as simple as sand is seen in a new light under a microscope . Without magnification, sand looks ordinary and plain . Under magnification, it’s clear that sand from the ocean’s edge contains microscopic shells, shell fragments, coral, and volcanic rock .

Plain beach sand is really made up of many tiny, colorful items.

Looking through a microscope can reveal the tiny living things in pond water.

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Magnified Two Hundred to Fifteen Hundred Times (200–1,500x)

Early compound microscopes had some problems because the lenses often created distortions in the image . It was extremely difficult to tell what was the actual image and what was an artificial effect caused by the way light passed through the lenses . In the early 1800s, a British scientist named Joseph Jackson Lister invented a new type of lens that solved the distortion problem . His work made microscopes more powerful and reliable .

As a result, microscopes allowed new discoveries in multiple fields of science and medicine . In the mid-1800s, French biologist Louis Pasteur (pass-TUR) discovered that microorganisms in the air could contaminate beer or milk, causing it to spoil . Around the same time, the improved microscope allowed physicians to see microorganisms in the bodies of sick people . For the first time, scientists made the connection between microorganisms and disease . This discovery revolutionized the practice of medicine .

Early microscopes could stretch images the same way they get stretched by a funhouse mirror.

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The early compound microscope also led to the discovery that no two snowflakes are alike . American photographer Wilson Alwyn Bentley was known as “Snowflake” Bentley for his work with snowflakes . He paired a camera with his microscope in the late 1800s and early 1900s to take photographs of more than five thousand individual snowflakes . He showed that snowflakes are mirror images of themselves in six different directions .

Compound microscopes also allowed scientists to discover that salt, sugar, and some other substances form very specific crystal structures . Salt is made up of only two types of regularly spaced atoms . As a result, it forms regularly shaped cubic crystals . Sugar, or sucrose, is made up of two different, simpler types of sugar . It forms crystals that are slanted at each end and more oblong than salt crystals .

These photographs taken by “Snowflake” Bentley in 1902 revealed how each snowflake is a different, beautiful shape.

Sugar crystals form regular rectangular shapes.

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The ability to see the world’s tiny details can help people understand how things work . Take the cocklebur . A Swiss engineer named George de Mestral became curious about the cockleburs that stuck to his clothing and his dog’s fur . Wondering how they attached themselves so firmly, he took a closer look at the burrs under a microscope . He saw that they had tiny hooks that latched onto loops in the fabric of his pants .

Inspired by nature’s hook-and-loop fastener, de Mestral worked to recreate the design using fabric . Years later, the result was Velcro . Velcro is made up of two pieces of fabric, one covered in thousands of tiny hooks and the other covered in thousands of tiny loops . The hooks and loops allow the two pieces of fabric to “zip” together .

Scientists copied the shape of natural hooks on cockleburs (left) to make the fastener Velcro (right).

Through a Microscope • Level W 14

Magnified One Million Times (1,000,000x)

Because of the way light works, there is a limit to how much magnification a compound microscope can achieve . During the last century, scientists developed microscopes that use different ways to illuminate samples, including ultraviolet light and beams of energy called electron particles .

Microscopes that use electron beams to illuminate samples are called electron microscopes . They provide the greatest magnification of any type of microscope currently in existence . They can magnify samples up to one million times (1,000,000x)!

A tiny dust mite feeds on flakes of human skin.

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Conclusion

With each new degree of magnification, more detail is revealed about the tiniest structures of plants, animals, and materials . As a result, microscopes have allowed countless discoveries in nearly every field of science .

Microscopes make the invisible visible, allowing us to explore the world in an entirely new way .

A microscopic view of a fish scale reveals details that are impossible to see with the naked eye.

Stains and DyesMany cells and other

small objects are transparent, or see-through. This makes them difficult to see under a microscope. Stains and dyes have been used since the 1800s to make objects stand out more against their backgrounds. This makes the objects easier to see with a microscope.

Stains reveal that healthy cells (orange) are being replaced by damaged cells (purple) in this microscopic view of a diseased human liver.

Through a Microscope • Level W 16

Glossaryantennae (n.) the thin feelers found on the heads

of some animals that help them touch and smell (p . 7)

artificial (adj.) human-made; not occurring naturally (p . 11)

compound (adj.) made up of two or more elements or parts (p . 6)

contaminate (v.) to make something unusable or unsafe by adding a harmful or unwanted substance (p . 11)

crystal (n.) a solid substance in which the atoms are arranged in a regular, tight pattern (p . 12)

distortions (n.) twisted or inaccurate representations of something (p . 11)

electron (n.) a particle in an atom that orbits the nucleus and has a negative electrical charge (p . 14)

microorganisms microscopic organisms, such as (n.) viruses or bacterial cells (p . 9)

microscope (n.) a device used to view tiny objects (p . 4)

nutrients (n.) substances that living things need to live, stay healthy, and grow (p . 8)

product (n.) the result of multiplying two or more numbers (p . 6)

specimens (n.) examples used for comparison, study, or display (p . 5)