Life Sciences Archives - Page 3 of 7 - Eva Varga


December 1, 2015

For the past six years or so, we have purchased our dairy products direct from a local farmer.  My kids and I love the taste of raw milk and crave its distinctive flavor. We can even taste the difference between farm fresh eggs from chickens allowed to wander and graze on a variety of foods (including insects and other invertebrates) and eggs from chickens confined to a small cage their entire lives.

Bacteria & Enzymes of Milk: The Impact of Louis Pasteur @EvaVarga.netWe first tried raw milk at the home of a homeschool family in Bend, Oregon. It was deliciously creamy. We soon heard stories of friends who had experienced amazing results — ear infections, asthma, and allergies — all diminished after changing to a diet of Real And Wholesome milk. Thus began our journey towards a more wholesome diet – including raw milk.

Raw milk is milk from cows, sheep, or goats that has not been pasteurized. Pasteurization is a process that kills harmful bacteria by heating milk to a specific temperature for a set period of time. First developed by Louis Pasteur in 1864, pasteurization kills harmful organisms responsible for such diseases as listeriosis, typhoid fever, tuberculosis, diphtheria, and brucellosis.

Controversial, proponents on both sides of the pasteurization debate will cite research and anecdotal evidence to support their side. Did you know, however, that Pasteur initially developed the process for which he is most well known not for milk but for wine? As he was born in December, I thought I would share a little insight into the life and the impact of Louis Pasteur.

Science Milestones: Louis Pasteur @EvaVarga.netBiography

Born on December 27, 1822, in Dole, France, Louis Pasteur was the son of a sergeant major in the Napoleonic wars who grew up in Arbois, a small town in eastern France surrounded by farms and vineyards.

“When I approach a child, he inspires in me two sentiments; tenderness for what he is, and respect for what he may become.” ~ Louis Pasteur

An average student, Pasteur had a passion for drawing and painting. As a boy, he captured his family in a series of lifelike portraits, Pasteur: Dessins et pastels, which showed a keen eye for precision and detail. While his teachers encouraged his artistic side, his father considered painting an indulgence: what counted was solid schoolwork.

Pasteur began a career in chemistry with a post at the University of Strasbourg and quickly made a ground-breaking discovery. He showed that otherwise identical molecules could exist as mirror images (or ‘left’ and ‘right-handed’ versions). He noticed that molecules produced by living things were always left-handed. This discovery was a fundamental step forward in microbiology, underpinning modern drug development and even our understanding of DNA.

Bacteria & Enzymes of Milk: The Impact of Louis Pasteur @EvaVarga.netPasteur also disproved the age-old theory that life appeared spontaneously with a simple experiment. He showed that food decayed because of contamination by microbes in the air. He went on to argue that these could cause disease. Though his ‘germ theory’ was initially controversial (he was not a doctor, after all), it eventually led to the development of antiseptics and changed healthcare forever.

“A bottle of wine contains more philosophy than all the books in the world.” ~ Louis Pasteur

Relatedly, he discovered that microbes were responsible for souring alcohol. In a series of careful experiments, Pasteur discovered that heating wine to 55 degrees killed bacteria without ruining the taste. This process, later named pasteurization, saved the wine industry, and cemented Pasteur’s fame. Today, this process is widely used to keep food free from disease.

“Officially, I recommend the pasteurization of milk. But I still love drinking it straight from the udder.” ~ Louis Pasteur

While Louis Pasteur is most well known for developing the process of pasteurization; his work in germ theory also led him to create vaccinations for rabies, a highly contagious infection which attacks the central nervous system. It enters the body through the bite of an infected animal or through infected saliva entering an existing wound.

After experimenting with the saliva of animals suffering from the disease, Pasteur concluded that the disease rests in the central nervous system of the body. When an extract from the spinal column of an rabid dog was injected into healthy animals symptoms of rabies were produced. By studying the tissues of infected animals – rabbits, Pasteur was able to produce an attenuated form of the virus that could be used for inoculation.

Pasteur became a national hero and was honored in many ways. He died at Saint-Cloud on 28 September 1895 and was given a state funeral at the Cathedral of Notre Dame and his body placed in a permanent crypt at the Pasteur Institute.Bacteria & Enzymes of Milk: The Impact of Louis Pasteur @EvaVarga.net

Bring it Home

➤ In the lab, Milk – How Sweet Is It?, students test different samples to see which ones contain the lactase enzyme.

➤ The enzyme lactase is produced in the small intestines of infants where it breaks down the sugar lactose found in milk. Zoom in to the molecular level to see how the enzyme works in this striking animation, Lactose Digestion in Infants.

➤ Learn how a single genetic mutation that first enabled ancient Europeans to drink milk, The Milk Revolution.

➤ Check out the The Science of Milk TED-Ed lesson by Jonathan O’Sullivan

➤ After watching the short film Got Lactase?, students may explore how the enzyme lactase hydrolyzes lactose into monosaccharides, and practice graphing and analyzing data. The accompanying worksheet requires them to provide reasoning for their answers. If you have time to explore the extension portion of the activity, you can tie in anaerobic respiration and why lactase non-persistence causes pain and discomfort. (Recommend for high school level)

Science Milestones



October 17, 2015

Have you ever seen weird bumps growing on stems, leaves, buds, or flowers? You might be surprised to learn that these odd growths are not the plant’s idea at all but are caused by a fly, wasp, midge, or other insect.

How Are Galls Formed?

The goldenrod gall, for example, is formed by one kind of gall fly. The female picks out a tender spot on a growing tip of the plant where she deposits an egg and flies off. When the larva hatches out of the egg, it will bore into the plant. As it does so, it excretes a chemical which causes this part of the plant to enlarge into the swelling that we call a gall. Soon the larva is surrounded by this enlarged tissue, essentially its gall house.

Through the summer months, the larva will eat away at the inside of the house. In autumn, the plan dies and the gall turns brown and hard. At this time, the larva digs a tunnel out to the skin of the gall, but does not break through. Instead, it curls up to await spring at which point it will pupate and eventually emerge as an adult gall fly.Insect Galls: A Nature Study @EvaVarga.net

Galls Are Diverse

There are many kinds of galls and each is formed in a different way. In my earlier post, Galls: A Nature Study, I shared the small variety of galls we’ve encountered in our nature studies.

In North America, more types of galls are found on Oaks than on any other kind of plant. They can turn up on many different kinds of plants, however. Including flowers, ferns, and even mushrooms.

 

Symbiotic Relationships

Not all galls are started by insects. Some are caused by mites or nematodes (tiny worms). Fungi and bacteria can also cause galls to form.

Nitrogen-fixing bacteria are microorganisms capable of transforming atmospheric nitrogen into fixed nitrogen (inorganic compounds usable by plants). More than 90 percent of all nitrogen fixation is effected by these organisms, which thus play an important role in the nitrogen cycle.

Even though the galls may deform the plant, they usually don’t do serious harm. Galls also provide a food source for many animals – including woodpeckers and many other insects.

Some galls are even useful to humans. The Bushmen of the Kalahari Desert in Africa make a powerful poison for their arrow tips from crushed gall wasps. In the states, galls that fall from Oak trees are sometimes used by farmers to feed their livestock.Insect Galls: A Nature Study @EvaVarga.net

Bring it Home

Undertaking the activities described below provide students with an opportunity to begin to examine the affect of environmental conditions on galls and insect growth. Students also develop an appreciation and understanding of the complex interactions among plants and animals.

Materials

  • collection jars
  • glue
  • old nylon stockings
  • an intact gall (one without an exit hole)
  • dissecting knife
  • rubber band

Gall Dissection

The larva lies at the center of the gall. Use a dissecting knife or other sharp tool to make an incision in the gall parallel to the stem, but off center. Create a small window so the larva is clearly visible.

Put a little glue around the perimeter of the window and press it against the inside wall of a jar. You will now be able to observe the larva as it develops. Keep track of your observations in your notebook.

Larval Development

Place the gall inside a collection container with nylon stretched over the opening and secured with the rubber band. Make observations of the changes that take place as the insect develops and emerges from the gall.

Most specimens should emerge in approximately 3 weeks.

Inquiry Activities

Design an experiment to explore the effect of different environmental factors such as light, temperature, or moisture. For example, does the amount of light affect the development of the larva?

Once you start looking, you’ll likely find lots of galls. Insect galls are fascinating.



October 12, 20157

As a science educator, I have always relied on my own experience and the wealth of material that I have collected over the years to develop our homeschool science curriculum. I have also allowed the interests of my children to drive our studies, ensuring that we also cover a variety of topics.

Months ago, when we were in the midst of our Human Anatomy unit with our STEM Club, I realized that I needed to go more in-depth, specifically for my daughter. I hadn’t taught high school level science, however, so I was a little apprehensive. Would I be able to find labs that would be both challenging and adaptable for the homeschool setting?

As I began my research, I was delighted to discover a great resource for teaching middle school and high school biology, Amy Brown Science. As I browsed her website and the products available at her Teachers Pay Teachers store, I was immediately drawn to her Genetics Complete Bundle Unit and am delighted to share with you how we’ve begun to use it in our homeschool.

Diving into Genetics with Amy Brown @EvaVarga.netGenetics Unit Bundle

Though my son is a few years younger than my daughter, I generally teach them both simultaneously. I thereby began our study by reading aloud, Gregor Mendel: The Friar Who Grew Peas. While this is a picture book, I have found that everyone enjoys listening to quality literature and it was a great way to spark interest in the new unit. I then followed up with Amy’s Genetics Warm-ups to review the material that was covered in the book.

Note: The warm-ups are a separate item in Amy’s TpT store and are not part of the Genetics Complete Bundle. However, they are the perfect tool for review and reinforcement.

Together, we viewed the PowerPoint and took notes along the way. My daughter and I have now begun to progress slowly through the material in the bundle. There is really so very much – it will take us a while to complete everything. I am impressed with the quality of the material – the lessons are laid out very clearly and each warm-up includes a teacher’s answer key.

My favorite component are the labs: Simple DNA Extraction, Effect of Environment on Gene Expression, and The Hardy Weinberg Equation. While each is available individually, the fact that they are bundled not only saves me time but puts everything into context.

Amy does an excellent job of describing the lab procedures in a way that students can easily follow along. She also provides tips for the teacher in regards to set-up and preparation.

The genetics unit focuses almost entirely on Mendelian genetics and on genetics topics that arose after Mendel’s death. The materials do include some discussion of Darwin and natural selection.

Diving into Genetics with Amy Brown @EvaVarga.netThe Genetics Complete Unit Plan Bundle contains at least 3 weeks of materials depending on how many lab activities you want to do. This unit has everything that a teacher needs to teach a unit on genetics to Biology or life science students in grades 8-12.

The bundle includes:

  • A 61 Slide PowerPoint
  • Teacher Notes
  • Student Notes
  • 3 Labs
  • A Jeopardy-style game to review concepts
  • 5 Quizzes
  • 7 Genetics Practice Problem Worksheets
  • A Crossword Puzzle
  • A Unit Test

Wow! All that for a bundled price of just $25.99! This is a savings of 39% off the price if you were to purchase the items individually.



September 4, 2015

In a series of posts this week, I will be sharing 5 Misconceptions in Science and providing lessons and activities to help dispel these conceptual misunderstandings. Today’s post focuses on common misconceptions in biology.

misconceptionsbiologyMisconceptions in Biology

Misconceptions abound in all science disciplines, even in biology. Some of the misconceptions in biology that I have encountered include:

Coral reefs exist throughout the Gulf and North Atlantic waters.

Dinosaurs and cavemen lived at the same time.

Acquired characteristics can be inherited.

Houseflies live for only 24 hours.

Winter weather can be predicted by studying the thickness of the fur of some animals.

Humans are responsible for the extinction of the dinosaurs.

Why I am not able to dispel all of these in a single post, I’ve selected a couple that I think will work well in a middle school setting.

How to Dispel Misconceptions

As I stated previously, students should be encouraged to ask questions given ample opportunity to engage in hands-on experiments or demonstrations designed to test hypotheses.

In my post, Misconceptions in Astronomy, we explored using demonstrations to dispel the myth that the seasons are caused by the Earth’s tilt. Today will will explore how we can use hands-on inquiry activities and our own observations to dispel a couple of myths in biology.

MISCONCEPTION #5

Houseflies live for only 24 hours

The common housefly (Musca domestica) tends to live for about two to three weeks once it reaches the adult stage. The fly does move through all four of its life stages fairly quickly, 6 to 42 days for an egg to transform from larva to pupa to adult.

Eggs take a few hours to hatch into larvae, which in turn take a couple days or weeks to develop. Once the larva becomes a pupa with a protective case around it, it takes 2 to 10 days to emerge from its shell as an adult. Even after adulthood, it takes a few days for it to be able to reproduce.

They mayfly, which belongs to a different order of insects, also goes through multiple stages of development that lasts about a year. Mayflies lay their eggs in a body of water, where they typically gather on the bottom. They hatch into nymphs, which then undergo a number of molts before they make their way to the top of the water’s surface as a “pre-adult” with wings.

They eventually molt once more before final adulthood. Adult mayflies are not very long-lived as the digestive system stops working with the final molt, and the flies tend to die within a couple of days.

Try It :: Consider rearing housefies or flightless fruit flies in a terrarium to observe the complete life-cycle. How long do they live on average? Does their life-span differ by species?

BONUS MISCONCEPTION

Worms are found in apples

The ‘worm’ frequently featured in cartoons is actually the larva of the codling moth, Cydia pomonella. Female moths lay eggs on small developing apples or leaves. The larva tunnels through the skin and feeds on the seeds. Worms do not have legs, insects do. It would be very difficult for an earthworm to climb a tree or fly.

Try It :: Consider gathering a few apples from an orchard – a few picked from the tree and a few that have fallen on the ground. Place them in a small terrarium and observe what critters emerge from these “nurseries” as the apple decays. Use a hand lens or microscope to closely observe the anatomy of the larvae.

5 Misconceptions in Science & How to Dispel Them @EvaVarga.net

Don’t miss the posts I shared earlier this week:

Misconceptions in Science & How to Dispel Them (series introduction)

Misconceptions in Geology & Meteorology

Misconceptions in Chemistry & Physics

Misconceptions in Astronomy

This concludes my 5 day series featuring common misconceptions in science. If you have enjoyed the series, I encourage you to check out my Science Milestones series that focuses upon the discoveries and advancements of scientists through history.

This series is one of many hopscotch link-ups. Hop over and see what others are sharing.

Hopcotch2015



August 8, 2015

The Dean Creek Elk Viewing Area and the O.H. Hinsdale Interpretive Center are popular tourist stops along Hwy. 38 near Reedsport. Here, visitors are able to observe up-close views of Roosevelt Elk, with the herd sometimes reaching as many as 120 elk. This area of mountains, meadows, and marshes also are home to beaver, coyote, muskrat, mallards, Canada geese, and great blue heron.

Roosevelt Elk: A Nature Study @EvaVarga.netThe Roosevelt Elk are native to the area and are considered Oregon’s largest land animal. Inhabiting forests and meadows from northern California to British Columbia, they are the largest of six sub-species of elk. They generally live between 10 to 15 years, but some may live more than 20 years.

In this short video by Chris Cru, you can observe the Roosevelt Elk peacefully grazing as well as a coyote running in the background.


The antlers of a Roosevelt elk can reach spreads of nearly 3 feet and are thicker than the antlers of the Rocky Mountain elk. Older, stronger bulls have larger antlers, with 6 or more points per side, while yearling bulls have single spikes.

A mature bull elk can weigh an imposing 700 to 1200 pounds, standing 5 feet tall at the shoulder. Cows weigh about 500 to 700 pounds, while a calf weighs just 23 to 45 pounds at birth.

Their brown-gray winter coat will turn to a glossy, reddish-bay color in the summer. A tawny rump patch is outlined in black and they boast a thicker mane. At birth, calves are spotted and more tawny in color. As mature elk age, their coats will lighten in color.

Roosevelt Elk: A Nature Study @EvaVarga.net
Using a range finder to calculate our distance apart

Nature predators include mountain lion and black bear which primarily feed on new calves and sick animals. When approached or threatened, both cows and bulls will use their sharp front hooves for protection. Cows will bark an alarm that sounds like a high-pitched neigh while calves will bleat when danger approaches.

In late summer, bulls shed their velvet by rubbing antlers against tree limbs and bushes until the new antlers are hardened and shiny. This helps the males win over the female when the mating season begins in autumn.

Roosevelt Elk: A Nature Study @EvaVarga.netThe elk bulls bugle during the fall season. This is a great time to see the males in action. The bull elk’s deep, resonating bugle can be heard across the meadow as the males call to attract a female, move in to spar with a competitor, and take control of the harem.

To signal their status and fitness, the bulls will wallow in mud and spray themselves with urine. They will also tangle plants in their antlers to appear more imposing and better emphasize their size and power.

Roosevelt Elk: A Nature Study @EvaVarga.netWhen the rut season is over, the females will force the males out of the heard once again. He will generally join up with a small group of other males though occasionally he’ll remain solitary. They then focus on grazing to gain nourishment fro the oncoming winter months.

The bulls drop their antlers in the later winter which become an important source of calcium for smaller forest mammals including coyotes, squirrels, and mice.

~ ~ ~

We’ve always enjoyed taking part in the monthly challenges at Handbook of Nature Study. This month our selected challenge was to Sketch Outdoors.



July 1, 2015

When my son was diagnosed with congenital nystagmus as an infant, I became increasingly interested in heredity or the passing of phenotypic traits from parents to their offspring. Both my brothers also have nystagmus and it was now clear that I carry the gene as does my daughter.

The Father of Genetics, Gregor Mendel @EvaVarga.net

This post contains affiliate links.

Nystagmus is inherited in an X-linked pattern. A condition is considered X-linked if the mutated gene that causes the disorder is located on the X chromosome, one of the two sex chromosomes in each cell. In males (who have only one X chromosome), one altered copy of the gene in each cell is sufficient to cause the condition. In females (who have two copies of the X chromosome), one altered copy of the gene in each cell can cause the condition, although affected females may experience less severe symptoms than affected males.

Genetics is the study of genes, heredity, and genetic variation in living organisms.

Single gene inheritance is also referred to as Mendelian inheritance as it follows transmission patterns Gregor Mendel, a late 19th-century scientist and Augustinian friar, observed in his research on peas. As a result of his work, he is known as the Father of Genetics.

Mendel studied ‘trait inheritance’ or how different traits are passed on from parents to their children. He observed that organisms (pea plants) inherit traits by way of discrete “units of inheritance”. This term is a somewhat ambiguous definition of what is referred to today as a gene.

The four types of Mendelian inheritance patterns he described include:

Autosomal: the gene responsible for the phenotype is located on one of the 22 pairs of autosomes (non-sex determining chromosomes).

X-linked: the gene that encodes for the trait is located on the X chromosome.

Dominant: conditions that are manifest in heterozygotes (individuals with just one copy of the mutant allele).

Recessive: conditions are only manifest in individuals who have two copies of the mutant allele (are homozygous).

Biography

The Father of Genetics, Gregor Mendel @EvaVarga.netJohann Mendel was born July 20, 1822, in Heinzendorf bei Odrau, a small village in the Czech Republic (formerly the Austrian Empire). His parents were small farmers who made financial sacrifices to pay for his education.

He entered the University of Olomouc in 1840. He took courses in physics, mathematics and philosophy. He was advised by a professor to join the Abbey of St. Thomas in Brünn as a monk when he was 21 years of age to help offset the cost of his education.

The Abbey actually had a good reputation for its teaching of sciences, and its director, Abbot Franz Cyril Napp, was particularly interested in heredity of traits in plants and animals on farms. Upon joining the Abbey, he took the name Gregor.

My scientific studies have afforded me great satisfaction; and I am convinced that it will not be long before the whole world acknowledges the results of my work.  ~ Gregor Mendel

After completing his studies, he returned to the monastery in 1854 and took a position as a physics teacher at a school at Brünn, where he taught for the next 16 years. The monastery had a 5 acre garden, and two former professors encouraged Mendel to pursue his interest in heredity by using the garden for experiments.

Mendel set himself the very ambitious task of discovering the laws of heredity. To achieve this, he embarked on a highly systematic, eight year study of edible peas, individually and carefully recording the traits shown by every plant in successive generations. His work involved growing and recording the traits in about 30,000 plants.

One of the keys to his success was breeding from closely related pea varieties which would differ in only a small number of traits. The seven traits of pea plants that Mendel chose to study: seed wrinkles; seed color; seed-coat color, which leads to flower color; pod shape; pod color; flower location; and plant height.

In 1866, he published his heredity work, though it was not immediately recognized for the wealth of information it contained.

Bring it Home

? Explore genetics in more depth with a Genetics Unit Bundle from Amy Brown.

? Use M&M’s to visually see the genetic probability that an offspring will carry a certain trait. Just don’t each them all before you finish!

? Explore the genetics of sickle cell disease through Punnett squares, pedigrees, and an optional chi-square analysis with this classroom activity from the Howard Hughes Medical Institute.

? Enjoy this 3-D animation, available in both basic and advanced detail, which depicts the molecular machinery responsible for quickly and accurately copying DNA.

? Here is a cute video of an interview with Gregor Mendel from Untamed Science.

? Download the free printables from Stephanie Harrington and enjoy the book Gregor Mendel: The Friar Who Grew Peas.

? Create a DNA model of your own using pipe cleaners and beads or if you prefer, Lego bricks.

? Erect a DNA Double Helix Table Sculpture Puzzle

? If you still have those M&Ms, consider this Easter egg and M&M genetics activity from All Things Beautiful!

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.