Nettie Stevens: The Genetics Pioneer Who Discovered Sex Chromosomes

At a time when women mostly married and stayed home, or were teachers or nurses if they wanted to work, Nettie Stevens became a research scientist and her discoveries changed genetics forever.

NettieStevensGeneticsPioneerOnce she graduated with her PhD in 1903, she and a colleague (Thomas Morgan) began a collaboration on the controversial and unresolved question of how sex is determined in the developing egg. Did external factors, like food and temperature, set the sex of an egg? Or was it something inherent to the egg itself? Or was sex inherited as a Mendelian trait?

She examined the yellow mealworm, Tenebrio melitor, and made a striking observation. She had observed that this species produced two classes of sperm: a type that carried ten large chromosomes, and a type that carried nine large and one small chromosome. Body cells in the females contained 20 large chromosomes while males carried 19 large and one small chromosome.

Stevens reasoned that when an egg is fertilized by a sperm that carries the small chromosome, the result is a male offspring. The presence of the small chromosome might be what decided the individual’s “maleness.”

She published her research in 1905 and it eventually evolved into the XY sex-determination system we know today: The father’s sperm, which can carry either X or Y chromosomes, determines the sex of the offspring. Before Stevens’ work, scientists thought that the mother or the environment determined if a child was born male or female.

Biography

Nettie StevensNettie Maria Stevens was one of the first American women to be recognized for her contribution to science. Yet she didn’t begin her career in genetics until later in life.

Stevens was born on July 7, 1861, in Cavendish, Vermont, to Ephraim and Julia Stevens. After the death of her mother, her father remarried and the family moved to Westford, Massachusetts.

Initially, Stevens taught high school and was a librarian for more than a decade. Her teaching duties included courses in physiology and zoology, as well as mathematics, Latin, and English. Her first career allowed her to save up for college; at the age of 35, she resigned from a high school teaching job in Massachusetts and traveled across the country to enroll at Stanford University in California.

At Stanford, she received her B.A. in 1899 and her M.A. in 1900. She also completed one year of graduate work in physiology under Professor Jenkins and histology and cytology under Professor McFarland.

Stevens continued her studies in cytology at Bryn Mawr College, where she obtained her Ph.D. Here, she was influenced by the work of Edmund Beecher Wilson and by that of his successor, Thomas Hunt Morgan. Her work documented processes that were not researched by Wilson and she used subjects that he later would adopt along with the results of her work.

At age 50 years, only 9 years after completing her Ph.D., Nettie Stevens died of breast cancer on May 4, 1912 in Baltimore, Maryland.

Bring it Home

▶︎ Dive into Genetics with a fun unit study

▶︎ Enjoy a slide show presentation on genetics

▶︎ Try out this jigsaw format activity to explore the sex determination mechanisms of seven organisms, Xs and Os

▶︎ Learn about the Father of Genetics: Gregor Mendel

▶︎ Try this Gummy Bear Genetics lab from The Science Teacher (a NSTA publication)

▶︎ Use pipecleaners and beads to show how genes and chromosomes are inherited in this Pipecleaner Babies lab.

▶︎ Use pennies to do this How Well Does a Punnet Square Predict the Actual Ratios? lab.

Science Milestones

Visit my Science Milestones page to learn more about scientists whose discoveries and advancements have made a significant difference in our lives or who have advanced our understanding of the world around us.

The bloggers of the iHomeschool Network have teamed up to create fun and original unit studies on fascinating people who were born in July.

 

The Puzzling Impact of Ernő Rubik

For the past eight months there has been a constant click heard in my home. At the dinner table, while driving in the car, and even late at night when I am beginning to drift off to sleep, I can hear the subtle sounds of my son cubing. Cubing has become one of his passion projects and he spends every waking moment with a puzzle in his hands.

The Puzzling Impact of Erno Rubik @EvaVarga.netI had given him a traditional Rubik’s Cube a few years ago for Christmas but once it was scrambled, it sat in the corner of his bookshelf collecting dust. That was until he stumbled upon a recommended video on his YouTube feed of Collin Burns’ 5.25 world record solve. That was all it took. He was hooked.

As it is always in his hand, he gains a lot of attention and notoriety. He is now recognized around our community as the fastest cuber. Kids and adults alike bring him cubes that they “messed up” for him to solve.

His best solve time for the 3×3 is presently 7.22 seconds. He averages 13.09. Yet the 3×3 is not the only puzzle he enjoys. He also competes in 2×2, 4×4, 5×5, Megaminx, Pyraminx, and Skewb.

The Puzzling Impact of Erno Rubik @EvaVarga.netBiography

Ernő Rubik was born during World War II in Budapest, Hungary on the 13th of July 1944. His father, Ernő Rubik Sr., was a flight engineer at the Esztergom aircraft factory and a highly respected engineer of gliders. His mother, Magdolna Szántó, was a poet.

While Rubik has stated in almost every interview that he got his inspiration from his father, he also considers university and the education it afforded him as the decisive event which shaped his life. From 1958 to 1962, Rubik specialised in sculpture at the Secondary School of Fine and Applied Arts and later attended the Budapest University of Technology where he became a member of the faculty upon graduation.

“Schools offered me the opportunity to acquire knowledge of subjects or rather crafts that need a lot of practice, persistence and diligence with the direction of a mentor.”

In the 1970s, Rubik was a professor of architecture at the Budapest College of Applied Arts. It was during this time that he invented the Rubik’s Cube. The cube was originally designed to help Mr. Rubik explain spatial relationship to a class that he taught at the time. He soon realized the potential of the cube and began to get the cube mass produced, applying for a patent in 1975.

It was quickly a huge success. The cube was originally called ‘Magic Cube’ but after some discussion the name was changed to what it is known for today, Rubik’s Cube. In an interview with CNN, Rubik stated;

Space always intrigued me, with its incredibly rich possibilities, space alteration by (architectural) objects, objects’ transformation in space (sculpture, design), movement in space and in time, their correlation, their repercussion on mankind, the relation between man and space, the object and time. I think the CUBE arose from this interest, from this search for expression and for this always more increased acuteness of these thoughts…

In the nearly forty years the cube has been around, over three hundred and fifty million copies have been produced. Yet, only about 1.25% of the people who have purchased the cube can actually solve it.

The Puzzling Impact of Erno Rubik @EvaVarga.netErnő Rubik witnessed his creation blow up around the world. The cube became the Toy of the Year twice in a row, and the first world championship for The Rubik’s Cube was in 1982. At this competition the first world record was set at 22.95 seconds. Nowadays that is what most cubers average.

Today, there are a variety of speed cubes available on the market. Each is designed to turn faster and more efficiently without the lockups or pops that speed cubers abhor. The current 3×3 record is 4.737 seconds held by a 19 year old from Australia, Feliks Zemdegs.

Bring it Home

Learn to solve the original 3×3 puzzle using online tutorials; there are many to choose from.

Challenge yourself to get faster or learn to solve another puzzle type.

Visit the World Cube Association and find a competition near you to see what it is all about.

Science Milestones

Visit my Science Milestones page to learn more about scientists whose discoveries and advancements have made a significant difference in our lives or who have advanced our understanding of the world around us.

The bloggers of the iHomeschool Network have teamed up to create fun and original unit studies on fascinating people who were born in July.

Science Milestones: The Heroine of Lyme Regis, Mary Anning

In my Facebook newsfeed recently, a memory popped up highlighting a field trip we took part in years ago when we first began our homeschool journey. Our visit to Paleo Lands Institute in Eastern Oregon is one of our fondest homeschool experiences. When we visit the Field Museum in Chicago last week, we reflected on this trip as we marveled at the many specimens they had on display – the most impressive, of course, was SUE (pictured below).

The unveiling of her 67-million-year-old skeleton at The Field Museum made global headlines in May of 2000. As the largest, best-preserved, and most complete Tyrannosaurus rex ever found, she is considered to be the most famous fossil ever found. She measures 40.5 feet long from snout to tail and 13 feet tall at the hip.

Interesting fact: While SUE is frequently referred to as a “she,” scientists don’t actually know her sex.

Virtually all parts of SUE’s skeleton are preserved in great detail—even the surface of her bones. Scientists can actually see where muscles, tendons, and ligaments once attached. Not only are most of the bones undistorted from fossilization, but cross-sections of the bones show that even the cellular structure inside remains intact.

w/ Sue at the Field Museum, Chicago

If SUE is the most famous fossil, who then is regarded as the most renowned fossilist the world ever knew?  The answer is Mary Anning.

Despite the fact that Mary Anning’s life has been made the subject of several books and articles, comparatively little is known about her life, and many people were unaware of her contributions to paleontology in its early days as a scientific discipline. How can this be, you ask?

Biography

Mary Anning by B. J. DonneMary Anning was born on the 21st of May 1799 to Richard and Mary Anning in Lyme Regis, Southwest England. Mary grew up in a prime location to lead a life of fossil collecting. The marine fossil beds in the cliffs in this area remain today a huge source of fossils from the Jurassic period.

Her findings contributed to important changes in scientific thinking about prehistoric life and the history of the Earth. At the age of 12, Mary Anning was to become one of the most famous popular palaeontologists, with her discovery of a complete Icthyosaur.

Interesting fact: Though she is now credited with the discovery, her brother had first found the specimen. Mary did find the majority of the remains and contribute significantly to the excavation work. Mary went on to find two more species of Ichtyosaur in her life.

In early 1821, Anning made her next big discovery with the finding of the first Plesiosaurus. She sent a drawing she made to the renowned George Curvier, who at first snubbed it as a fake. Upon further examination, he eventually reversed this statement finally giving Anning the respect she had deserved from the scientific community. This discovery is perhaps her most important find, from a scientific point of view.
Autograph letter concerning the discovery Wellcome L0022370
The majority of Mary’s finds ended up in museums and personal collections without credit being given to her as the discoverer of the fossils. There are many factors contributing to this error: the lack of appropriate documentation of her special skills, her social status, and more importantly, her gender. Many scientists of the day could not believe that a young woman from such a deprived background could posses the knowledge and skills that she seemed to display.

For example, in 1824, Lady Harriet Sivester, the widow of the former Recorder of the City of London, wrote in her diary after visiting Mary Anning:

“. . . the extraordinary thing in this young woman is that she has made herself so thoroughly acquainted with the science that the moment she finds any bones she knows to what tribe they belong. She fixes the bones on a frame with cement and then makes drawings and has them engraved. . . It is certainly a wonderful instance of divine favour – that this poor, ignorant girl should be so blessed, for by reading and application she has arrived to that degree of knowledge as to be in the habit of writing and talking with professors and other clever men on the subject, and they all acknowledge that she understands more of the science than anyone else in this kingdom.”

After her death on the 9th of March 1847, her unusual life story attracted the attention of scholars around the world. Her story was the inspiration for the 1908 tongue-twister “She sells seashells on the seashore” by Terry Sullivan and in 2010, one hundred and sixty-three years after her death, the Royal Society included Anning in a list of the ten British women who have most influenced the history of science.

Bring it Home

➤ For younger students, explore the fun games and activities at BBC’s Primary History Famous People: Mary Anning.

➤ Read the article, “Mary Anning: The Fossilist as Exegete” by Thomas W. Goodhue in Endeavour Magazine, March 2005 issue

➤ Build upon your child’s interest in fossils and geology in an in-depth Earth sciences curriculum study.

Geology Rocks➤ Visit a local geology club in your area and inquire about getting started in collecting.

➤ Discover Ice Age Fossils at La Brea Tar Pits in Los Angeles

 

Science MilestonesVisit my Science Milestones page to learn more about scientists whose discoveries and advancements have made a significant difference in our lives or who have advanced our understanding of the world around us.

Interested in learning about others who were born in the month of January? Hop over to Birthday Lessons in March to read posts by other iHomeschool Network bloggers.

More Than Just the Telephone: The Impact of Alexander Graham Bell

Unbeknownst to many, Alexander Graham Bell made outstanding contributions to aviation through his development of tetrahedral kites, the investigation of their application to personnel carrying aircraft, and his enlistment of talented associates who aided significantly in the progress toward accomplishing powered flight.

Expanding upon the design of the rectangular-celled box kite that Hargrave of Australia invented, Dr. Bell developed a three-sided triangular form of cell which he adapted to various multi-cellular shapes. This research led to a large kite in which on December 6th, 1907, his associate, Lt. Thomas Selfridge, flew to a height of over 160 feet.

Science Milestones: Alexander Graham Bell @EvaVarga.netAlthough his greatest scientific accomplishment was the invention of the telephone, Dr. Bell deserves wide recognition for his promotion of aeronautics. He was a member the Aerial Experiment Association that formed in 1907 who conducted flight experiments from his summer home at Baddeck, Nova Scotia.

“I have no doubt that a machine will be driven from the Earth’s surface at enormous velocities by a new method of propulsion – think of tremendous energies locked up in explosives – what if we could utilize these in projectile flight!” ~ Alexander Graham Bell

Believing that the substitution of an engine and propeller attached to the kite might permit free man-carrying flight, dispensing with the tethering line, Dr. Bell and Lt. Selfridge secured the services of Glenn H. Curtiss. Curtiss helped them to construct a proper engine, and they also engaged the assistance of J. A. D. McCurdy and F. W. Baldwin. These five men formed the Aerial Experiment Association for the stated purpose of “getting into the air” – which also put them in direct competition with the Wright brothers.

Biography

Science Milestones: Alexander Graham Bell @EvaVarga.netAlexander Graham Bell was born on March 3, 1847 in Edinburgh, Scotland. His mother was the daughter of a Royal Navy surgeon and was a skilled musician and portrait painter whose hearing loss when Bell was just twelve years old, brought deafness close to him.

Bell’s father, Alexander Melville, was the world world-famous inventor of “Visible Speech”, a code of symbols to guide the action of the throat, tongue and lips in the shaping of various sounds. It was devised as a key to the pronunciation of the words in all languages, but had become of most use in teaching the deaf to speak. His grandfather, Alexander, was a specialist in the correction of speech defects as well as a renowned public speaker, giving public readings from Shakespeare’s plays on London’s stages.

“Don’t keep forever on the public road, going only where others have gone. Leave the beaten track occasionally and dive into the woods.” ~ Alexander Graham Bell

Bell had natural musical ability and turned toward a career as a pianist. By the time he was 25, he was assisting his father at Weston House, a boys’ school near Edinburgh, and trading music and elocution lessons for instruction in other subjects. He continued his formal education at the University of Edinburgh and later specialized in the anatomy of the vocal apparatus at University College in London. At 22, with his formal education behind him, he became a partner with his father.

He moved with family to Ontario in 1870 and a year later Sarah Fuller, the principal of a school for the deaf in Boston, asked him to teach her teachers. His success lead to a professor appointment at Boston University.

Bell’s patent for his telephone was filed just two hours before another experimenter, Elisha Gray, filed his claim in the U.S. Patent Office.

While in Boston, Bell met the two men who financed his pioneer work with the telephone. Thereafter, Bell spent the latter part of his life in Washington, D.C. and his summer home in Nova Scotia. He became a United State citizen in 1882.

He died on August 2, 1922 at which time 14,347,000 telephone were in operation across the country.

Bring it Home

➤ Research and discuss the invention of the telephone, its origin, its innovations, its advantages and disadvantages, and how it has shaped today’s society.

➤ Watch a video about Alexander Graham Bell.

➤ Create a poster to illustrate the changes the telephone has undergone since Bell’s original invention.

Build a tetrahedral kite of your own. Test the flight and refine your design to make improvements.

➤ Research his contemporaries (Glenn Curtiss, the Wright brothers, Thomas Edison, etc.) and put together a presentation (PowerPoint, brochure, poster, video, etc.) to share with others their impact on technology.

➤ Although Bell is best known for inventing the telephone, he invented many other things. He held patents for 18 other inventions on his own and 12 for which he collaborated with others. Learn more about each of these.

Science Milestones

Visit my Science Milestones page to learn more about scientists whose discoveries and advancements have made a significant difference in our lives or who have advanced our understanding of the world around us.

Interested in learning about others who were born in the month of January? Hop over to Birthday Lessons in March to read posts by other iHomeschool Network bloggers.

Science Milestones: A New Astronomy with Johannes Kepler

Each month, I like to share a post celebrating the accomplishments of a scientist whose discoveries and advancements have made a significant difference in our lives. To honor the work of these amazing people, I provide a little peak into their life and share an unschool-style learning guides or unit study to guide you and your children on a path of discovery.

This month, I chose to honor the Johannes Kepler, who lived in an era when there was no clear distinction between astronomy and astrology. There was, however, a strong division between astronomy (a branch of mathematics within the liberal arts) and physics (a branch of natural philosophy).

Science Milestones: A New Astronomy with Johannes Kepler @EvaVarga.netJohannes Kepler

In 1596, the German astronomer published his first important work on astronomy, Mysterium Cosmographicum (The Cosmographic Mystery). As well as defending the heliocentric model of the universe previously proposed by Copernicus in 1543.

Kepler explained the orbits of the known planets around the Sun in geometric terms in an attempt to unravel “God’s mysterious plan of the universe.” To do this, he dow upon the classical notion of the “harmony of the spheres” which he linked to the five Platonic solids – octahedron, icosahedron, dodecahedron, tetrahedron, and cube.

Science Milestones: A New Astronomy with Johannes Kepler @EvaVarga.net

The Platonic solids, when inscribed in spheres and nested inside one another in order, correspond to the orbits of the planets Mercury, Venus, Earth, Mars, Jupiter, and Saturn.

In 1619, he published Harmonices Mundi (The Harmony of the World) wherein he stated his third law of planetary motion. He described the relationship between a planet’s distance from the Sun and the time taken to orbit around it as well as the speed of the planet at any time in that orbit.

Biography

Science Milestones: Johannes KeplerKepler was born in the small town of Weil der Stadt in the Swabia region of Germany and moved to nearby Leonberg with his parents in 1576. His father was a mercenary soldier and his mother, the daughter of an innkeeper. Johannes was their first child.

When Johannes was just five, his father left home for the last time and is believed to have died in the war in the Netherlands. As a child, Kepler lived with his mother in his grandfather’s inn. He tells us that he used to help by serving in the inn.

Kepler’s early education was in a local school and then at a nearby seminary. Intending to be ordained he went on to enroll at the University of Tübingen, a bastion of Lutheran orthodoxy.

Throughout his life, Kepler was a profoundly religious man. All his writings contain numerous references to God, and he saw his work as a fulfilment of his Christian duty to understand the works of God.

At Tübingen Kepler was taught astronomy by one of the leading astronomers of the day, Michael Mästlin. The curriculum was of course, geocentric astronomy, in which all seven planets – Moon, Mercury, Venus, Sun, Mars, Jupiter and Saturn – moved around the Earth, their positions against the fixed stars being calculated by combining circular motions.

This system was more or less in accord with current Aristotelian notions of physics, though there were certain difficulties. However, it seems that on the whole astronomers were content to carry on calculating positions of planets and leave it to natural philosophers to worry about whether the mathematical models corresponded to physical mechanisms. Kepler did not take this attitude. His earliest published work, Mysterium Cosmographicum, proposed to consider the actual paths of the planets, not the circles used to construct them.

 “I am satisfied…to guard the gates of the temple in which Copernicus makes sacrifices at the high altar.” ~ Johannes Kepler

Kepler was one of the few pupils to whom Mästlin chose to teach more advanced astronomy by introducing them to the new, heliocentric cosmological system of Copernicus. Kepler seems to have accepted almost instantly that the Copernican system was physically true.

Soon after moving to Regensburg in 1630, he became seriously ill with fever and on November 15 he died.

Bring it Home

What are Kepler’s three laws of planetary motion? How were his ideas viewed by his contemporaries?

Learn more about star polyhedra, discovered by Kepler in 1619 and prominently featured in the architecture of European churches.

Build models of the five Platonic solids; consider The Finnish Craft of Himmeli or Paper Models of Polyhedra.

Research the epitaph inscribed on his gravestone (sadly swept away in the Thirty Years War):

I used to measure the heavens,
now I shall measure the shadows of the earth.
Although my soul was from heaven,
the shadow of my body lies here.

 

Science Milestones

Visit my Science Milestones page to learn more about scientists whose discoveries and advancements have made a significant difference in our lives or who have advanced our understanding of the world around us.

Interested in learning about others who were born in the month of January? Hop over to Birthday Lessons in December to read posts by other iHomeschool Network bloggers.

The Engineering Feats of Alexandre-Gustave Eiffel

 

Each month, I like to share a post celebrating the accomplishments of a scientist whose discoveries and advancements have made a significant difference in our lives. To honor the work of these amazing people, I provide a little peak into their life and share an unschool-style learning guides or unit study to guide you and your children on a path of discovery.

This month, I chose to honor the Alexandre-Gustave Eiffel who is most recognized for creating the Eiffel Tower.

Science Milestones: The Engineering Feats of Alexandre-Gustave Eiffel @EvaVarga.netAlexandre-Gustave Eiffel

When the Statue of Liberty’s initial internal designer, Eugene Viollet-le-Duc, unexpectedly passed away in 1879, the Franco American Union and Auguste Bartholdi (the French sculptor who designed Lady Liberty) hired Alexandre-Gustave Eiffel as his replacement.

While Eiffel praised and retained Viollet-le-Duc’s plans for the sculpting and connection of the copper sheets (he would use Viollet-le-Duc’s repoussé technique and armature bars), he ultimately changed the initial plans for the interior design in favor of a modern approach. The Statue’s new internal structure would not rely on weight to support the copper skin but rather a flexible, skeletal system.

Eiffel designed a tall, central pylon (92 feet, or 28 meters) to be the primary support structure of the Statue’s interior. The pylon serves as the central attachment point for a lightweight truss work of complex asymmetrical girders which forms the Statue’s body. To connect the Statue’s copper skin to the pylon, flat metal bars are bolted at one end to the pylon and to the copper skin at the other end.

While the bars hold the Statue together, they also create flexible suspension (due to their malleability), acting like springs allowing the Statue to adjust and settle into the environment. This elasticity of Eiffel’s design is important because the Statue has to withstand winds from New York Harbor, temperature changes, and various other weather conditions.

Once his plans were approved, Eiffel supervised the Statue’s internal construction until its completion in late 1883. A few years later, Eiffel began his most famous project: the Eiffel Tower, which was completed for the Universal Exposition of 1889 (Exposition Universelle de 1889) in Paris. Eiffel died on December 27, 1923 in Paris, France.

Biography

A prominent French architect and structural engineer, Alexandre-Gustave Eiffel was born on December 15, 1832 in Dijon, France. Interested in construction at an early age, he attended the École Polytechnique and later the École Centrale des Arts et Manufactures (College of Art and Manufacturing) in Paris, graduating in 1855. Setting out on his career, Eiffel specialized in metal construction, most notably bridges. He worked on several over the next fewdecades, letting mathematics find ways to build lighter, stronger structures.

Science Milestones: EiffelIn his early work designing railway bridges, Eiffel relied on sophisticated mathematical designs renowned for their lightness, grace, and strength.

Eiffel is most famous for what would become known as the Eiffel Tower, which was begun in 1887 for the 1889 Universal Exposition in Paris. The tower is composed of 12,000 different components and 2,500,000 rivets, all designed and assembled to handle wind pressure.

The structure is a marvel in material economy, which Eiffel perfected in his years of building bridges—if it were melted down, the tower’s metal would only fill up its base about two and a half inches deep.

In his final years, Eiffel turned his interest to meteorology. He continued to study the subject at length until his death on December 27, 1923.

Bring it Home

There are a variety of ways in which you can expand upon your study of Eiffel. Consider some of the following suggestions to get you started.

🗼Learn more about his earlier engineering projects, including the Eiffel Tower in Paris.

🗽Explore the science behind the Statue of Liberty, Visiting the Statue of Liberty & Chemical Reactions.

Science Milestones

Visit my Science Milestones page to learn more about scientists whose discoveries and advancements have made a significant difference in our lives or who have advanced our understanding of the world around us.

Interested in learning about others who were born in the month of January? Hop over to Birthday Lessons in December to read posts by other iHomeschool Network bloggers.