Library: (133) results for "science"
Success in science requires a creative mind. This module explores the nature of creativity in the scientific process. It details various discoveries and explains how creativity played a significant role in each. The importance of logical thinking and background knowledge to the creative process is discussed.
This module profiles the career of astrophysicist France Córdova, director of the National Science Foundation. The module traces Córdova's path from her days at a high school that didn’t offer physics to female students, to her career as a writer, and ultimately to the top post in US science administration. Among her many accomplishments, this powerful role model built the most powerful X-ray telescope ever sent into space, published over 150 scientific papers, helped start a medical school, and has been a leader at several prestigious universities.
Nearly three million whales worldwide were killed at the height of the whaling industry. But 20th century laws to protect whales greatly affected the indigenous Māori people of New Zealand by outlawing their traditional practice of harvesting resources from whales that washed up on the beach. Over time, the Māori lost their ancient customs and their deep connection with whales. Māori whale expert and “whale rider” Ramari Stewart has dedicated her life to studying whales and preserving Māori traditions. Stewart is the first woman and indigenous person to have a marine mammal species named in her honor.
Scientific research rarely leads to absolute certainty. There is some degree of uncertainty in all conclusions, and statistics allow us to discuss that uncertainty. Statistical methods are used in all areas of science. The module explores the difference between (a) proving that something is true and (b) measuring the probability of getting a certain result. It explains how common words like "significant," "control," and "random" have a different meaning in the field of statistics than in everyday life.
This module traces the beginnings of neuroscience, with a focus on two fathers of neuroscience who shared the 1906 Nobel Prize for their work. Along with the advent of better microscopes, Camillo Golgi’s and Santiago Ramón y Cajal’s vastly improved staining techniques and meticulous drawings shed light on our understanding of the structure of nervous tissue. The module explores Golgi’s reticular theory, which was later proved incorrect, and Ramón y Cajal’s discovery that the brain was made up of individual cells.
The Piltdown Man was once hailed as the "missing link" in the evolution of apes to humans. However, the discovery at Piltdown - human skull fragments, ancient mammal bones, and archaic tools - was an elaborate hoax. The deception took a long time to be revealed due to errors by the discoverers. They succumbed to confirmation bias by accepting any evidence that supported their discovery and rejecting any contradictory evidence.
Scientists use multiple methods to investigate the natural world and these interconnect and overlap, often with unexpected results. This module gives an overview of scientific research methods, data processing, and the practice of science. It discusses myths that many people believe about the scientific method and provides an introduction to our Research Methods series.
"What is science and how does it work?" This module introduces the Process of Science series, which answers this question, and presents the scientific process as a way of thinking that can help in everyday decision making. A brief overview is given of key concepts that guide the Process of Science module series.
Theories are not based on one scientist's work but on an accumulation of evidence and ideas from many scientists over time. This module discusses how scientific theories are built and revised. It uses the development of the theory of evolution through natural selection to illustrate how theories are built through a process of testing, expanding, and refining.
Understanding graphs and other visual forms of data is an important skill for scientists. This module describes how to read and interpret graphs and introduces other types of visual data. With a look at various examples, it is clear how trends can be grasped easily when the data is shown in a visual form.
Knowledge of blood components brought about a revolution in surgery through safe transfusion. The module traces the development of our understanding of blood over centuries, beginning in 1628 with English physician William Harvey's breakthrough research on circulation. With a focus on early 20th-century experiments by Austrian researcher Karl Landsteiner, the module shows how the identification of clotting factors, blood types, and antigens was critical to medical science. Whole blood, plasma, serum, and different types of blood cells are defined.
Have you ever wondered: Just how old is Earth? If so, you’re in good company. For centuries, people have wondered, offering wildly different answers. In this module, we’ll explore the path science has taken in broadening understanding of our home. You'll see how people have used calculations from religious scriptures, observations of Earth processes, and more to stretch Earth's timeline beyond imagination. Today, we’ve determined that Earth is 4.54 billion years old. But how did we figure it out, and how can we grapple with such large amounts of time?
Observation is an important tool for scientific researchers, and describing what is observed is a valuable method of research. This module explains key features of scientific description and discusses how this method is used in the process of science. Examples from history illustrate the use of description, from the geologic exploration of the US in the 1800s to 20th century studies of primate behavior.
Exponential equations are indispensable in science since they can be used to determine growth rate, decay rate, time passed, or the amount of something at a given time. This module describes the history of exponential equations and shows how they are graphed. Sample problems, including a look at the growth rate of the reindeer population on St. Matthew Island in the Bering Sea, illustrate how exponential equations are used in the real world.
This module profiles the groundbreaking research of biologist Barbara McClintock in the field of genetics. The module describes McClintock’s painstaking process of identifying specific loci for inherited traits. It shows how her diligence and creativity advanced science through decades of research on maize plants, which led to a Nobel Prize for her discovery of “jumping genes” or transposons.
Have you ever thought about measuring something you cannot touch? How would you go about it? In this module, we’ll explore how scientists first began grappling with the idea of measuring the speed of light. But, before that, we’ll need to figure out what speed even is—How would you describe it? Your description might give you a hint at the science behind measuring speed.
Linear equations can be used to describe many relationships and processes in the physical world, and thus play a big role in science. This module traces the development of linear equations and explores their many uses in science. The standard form of linear equations is presented, and sample problems are given. Concepts include Cartesian coordinates, ordered pairs, slope-intercept form, describing vertical and horizontal lines, and calculating rates.
Scientific modeling is a research method scientists use to replicate real-world systems – whether it's a conceptual model of an atom, a physical model of a river delta, or a computer model of global climate. This module describes the principles that scientists use when building models and shows how modeling contributes to the process of science.
Peer review is an important part of the process of science. This module describes the history of peer review and shows how the review process helps validate the work of scientists and ensure that quality standards are met. The process is illustrated by actual correspondence among authors, reviewing scientists, and the editor of a scientific journal.
The module traces the life and career of organic chemist Percy Julian, who developed a way to synthesize cortisone in large quantities, earning him a place in the National Inventors Hall of Fame. The module relates Julian’s accomplishments and the numerous challenges that he overcame through unwavering perseverance in the face of racial barriers. From his upbringing in the Deep South where public schools stopped at the eighth grade for African American children, Julian went on to earn a PhD, was awarded over 130 patents, revolutionized glaucoma treatment, and became the second African American inducted into the National Academy of Sciences.
From home pregnancy tests to treatment for Ebola, the discovery of monoclonal antibodies has greatly advanced science and medicine. This module traces the work of immunologist César Milstein, who successfully created “hybridoma” cells capable of producing specific antibodies in mass quantities. The module describes Milstein’s life as a student in Argentina during the regime of Juan Peron and his later research as he became a world-class scientist, winning the Nobel Prize in 1984.
Wrinkle-resistant cotton is one of the most significant developments of the 20th century. In the midst of an economic and social climate that provided few opportunities for women in science, chemist Ruth Benerito developed a method of wrinkle-proofing cotton, which was being edged out of the clothing market by synthetic fabrics. This profile describes the life of the chemist who is often credited with saving the US cotton industry. It explains the cross-linking process that made “wash-and-wear” cotton fabric possible.
Controversy isn't always a bad thing. It exists in every field of science and in many cases clarifies and advances our scientific understanding. This module explains what scientific controversies are and how they differ from other kinds of controversy. Using the example of climate change, the module identifies factors that lead to controversies in science and explains how they are resolved.
Ethical standards are a critical part of scientific research. Through examples of scientific fraud, misconduct, and mistakes, this module makes clear how ethical standards help ensure the reliability of research results and the safety of research subjects. The importance and consequences of integrity in the process of science are examined in detail.
Scientific institutions and societies play an essential role in the process of science and contribute to the building of scientific knowledge. This module explores these different bodies and discusses three types in detail: research institutions, professional societies, and funding institutions. Specific examples highlight how these institutions are essential to progress in science.
The blue whale weighs approximately 190,000 kilograms, while a plankton weighs just 0.5 milligrams—a difference of 11 orders of magnitude. Scientific notation and order of magnitude are fundamental concepts in all branches of science. They are especially useful when expressing and comparing very large and very small measurements. This module traces the history of our base-ten numeration system and gives a step-by-step explanation of how to write numbers in scientific notation. Sample problems demonstrate how to divide numbers in scientific notation to determine orders of magnitude.
Science benefits from diverse interests and different points of view. This module explores at the human side of science. With a look at the unique background and motivations of individual scientists, it is clear how personal experience, varied perspectives, creativity, and even chance contribute to progress in science.
Scientific meetings and conferences play an important role in the process of science. This module describes the history of scientific societies, beginning with the Royal Society of London in 1660. Specific examples illustrate why scientists go to meetings, how these gatherings influence research, and why attending meetings can be important for students and new scientists.
The metric system is the standard system of measurement in science. This module describes the history and basic operation of the metric system, as well as scientific notation. The module explains how the simplicity of the metric system stems from having only one base unit for each type of quantity measured (length, volume, and mass) along with a range of prefixes that indicate multiples of ten.
This module explores the nature of scientific knowledge by asking what science is. It emphasizes the importance of a scientific way of thinking and shows how observation and testing add to the body of scientific knowledge. Focusing on astronomy and physics, the module highlights the work of scientists through history who have contributed to our understanding of the age of the universe as a means of conveying the nature of scientific knowledge.
Scientific investigation is not always a linear process that starts with a hypothesis and ends with a conclusion, as portrayed in the classic “Scientific Method.” The true scientific method is a much more dynamic and much less predictable, and can involve various methods that may overlap. This module serves as an introduction to our Practice of Science series of modules, which describe key scientific methodologies.
This module offers an in-depth profile of wildlife biologist Sergio Avila and his work to conserve endangered jaguars and other wildlife in the US-Mexico border region. Topics in environmental science and conservation biology are introduced. The module describes how research data are collected and analyzed and highlights the importance of cooperation among individuals and agencies to protect endangered plant and animal species.
Scientific literature is central to the development of science as a whole. This module explains what scientists mean when they refer to the scientific literature and offers specific examples of how scientists use it to (1) discover what other work has been done on a topic, (2) cite sources of their data, and (3) show how their interpretations relate to existing knowledge.
We experience the effects of acids and bases in our everyday lives, which is why these types of molecules were first described so many centuries ago. The definition of acids and bases has been refined over time to reflect an increased understanding of their chemical properties. We now know that the properties that accompany pH arise because of the concentration of hydrogen ions. A major step in our ability to analyze and use acids and bases was the creation of the pH scale, which gave scientists a numerical way to describe H+ concentration. This understanding of pH allows us to determine pH when we don’t know it, and adjust pH value as needed. Thus, we can wield acid-base chemistry as a tool with wide-ranging uses, from cleaning up industrial waste to calming our overactive stomachs and keeping our pet fish healthy and happy. Acids and bases also play a crucial role in the body, maintaining a blood pH of around 7.4 (and saving us from nausea, headaches, and heart problems). To understand how that happens, we need a more accurate definition of acids and bases.
Our bodies constantly produce carbon dioxide, some of which stays in the blood and becomes carbonic acid. So what keeps blood from becoming too acidic? Our blood has a built-in buffering system that works to maintain a neutral pH. This module explores how our body achieves this remarkable balancing act, and traces scientific discoveries that contributed to our current understanding of acid-base chemistry.
Testing predictions is a major part of scientific research, and a key component of many classic experiments. This module explores the research methods used by Meselson and Stahl in their ingenious 1958 experiment showing how DNA replicates. The module highlights the power of simplicity in what has been called "the most beautiful experiment in biology."
Animal behavior studies include observations made in natural environments and through controlled laboratory experiments. In this module, we’ll explore the history of animal behavior studies and how different methods of study have produced the wealth of information available today.
This module introduces animal ecology, the study of animals’ relationship to their environment. We’ll explore the concept of a species’ ecological niche, which includes living and nonliving things that a species needs to survive. Every species uses and changes its environment to support its survival. Sometimes this helps other species; other times it’s detrimental.
This module traces the life and scientific research of Mario Molina, the first Mexican-born chemist to win the Nobel Prize. Working with F. Sherwood Roland, Molina’s groundbreaking research led to an international treaty to phase out human-made chemicals that harm Earth’s protective ozone layer. As a result, ozone-depleting substances were reduced by 98 percent. Molina has since been crusading to further scientific research in developing countries, spread scientific knowledge that will protect the environment, and advance international policy to save the Earth.
The 19th and early 20th centuries saw great advances in our understanding of the atom. This module takes readers through experiments with cathode ray tubes that led to the discovery of the first subatomic particle: the electron. The module then describes Thomson’s plum pudding model of the atom along with Rutherford’s gold foil experiment that resulted in the nuclear model of the atom. Also explained is Millikan’s oil drop experiment, which allowed him to determine an electron’s charge. Readers will see how the work of many scientists was critical in this period of rapid development in atomic theory.
The 20th century was a period rich in advancing our knowledge of quantum mechanics, shaping modern physics. Tracing developments during this time, this module covers ideas and refinements that built on Bohr’s groundbreaking work in quantum theory. Contributions by many scientists highlight how theoretical insights and experimental results revolutionized our understanding of the atom. Concepts include the Schrödinger equation, Born’s three-dimensional probability maps, the Heisenberg uncertainty principle, and electron spin.
Our Atomic Theory series continues, exploring the quantum model of the atom in greater detail. This module takes a closer look at the Schrödinger equation that defines the energies and probable positions of electrons within atoms. Using the hydrogen atom as an example, the module explains how orbitals can be described by type of wave function. Evidence for orbitals and the quantum model is provided by the absorption and emission spectra of hydrogen. Other concepts include multi-electron atoms, the Aufbau Principle, and Hund’s Rule.
Dr. Bernardo Houssay was a pioneering researcher of the endocrine system, the system of glands that secrete hormones in the human body. Especially important was his work on a gland at the base of the brain called the pituitary and how multiple hormones enable the pituitary and other glands to affect one another in what are called "hormone feedback loops." That understanding resulted in Dr. Houssay being awarded the Nobel Prize.
Since the time of hunter-gatherers, human beings have been aware of how the wellbeing of plants and animals dictates our ability to survive. This module explores the strides we’ve made in understanding biological diversity (biodiversity) and how it impacts our ecosystems.
According to recent estimates, humans have significantly altered roughly 75% of land-based environments, resulting in often drastic changes to biodiversity. This module explores humans’ impact on the Earth and its ecosystems and how this ongoing change is affecting the global level of biodiversity.
The successful construction of the Panama Canal relied as much on a medical breakthrough as it did on technological advances and hard labor. This module profiles Cuban-American doctor Carlos Finlay, who identified mosquitoes as the culprits in the spread of malaria and yellow fever. Tracing how our understanding of infectious disease evolved, the module highlights Finlay’s perseverance in spite of initial rejection by the medical community. It shows how Finlay's insights helped to stop the spread of these diseases and ultimately made the Panama Canal possible.
Cell division is an enormously complex process that must go on millions and millions of times during the life of an organism. This module explains the difference between binary fission and the cell division cycle. The stages of cell division are explored, and research that contributed to our understanding of the process is described.
Beginning with the discovery of mitosis, the module details each phase of this cell process. It provides an overview of the structure of cell components that are critical to mitosis. The module describes Clark Noble’s experiments with the Madagascar Periwinkle, which led to the discovery of an effective cancer treatment drug. The relationship between mitosis and cancer is explored as is the mechanism by which anti-cancer drugs work to slow down or prevent cell division.
The experiences and observations of Charles Darwin significantly contributed to his theory of evolution through natural selection. This module explores those influences and describes evolution as a force for biological change and diversification. The first in a series, it details how the theory challenged the cultural mindset of the time, including the effect of his major works: On the Origin of Species by Means of Natural Selection and Sexual Selection and the Descent of Man.
The second in a series discussing the work of Charles Darwin, this module takes a deeper look into the processes that led to Darwin's theory of natural selection and examines specific mechanisms that drive evolutionary change. Key points on which the idea of natural selection rests are outlined. Examples from Darwin's personal life shed light on his thinking about change within a species and the "struggle for existence."
Our understanding of the term evolution has changed significantly since Darwin's time. This module explains how Darwin's work helped to give evolution the meaning it has today. It details the concept of "descent with modification" that Darwin described with the one figure originally included in Origin of Species. The module discusses how this model revolutionized scientific thinking about the similarities and differences between and within species, laying the foundation for our current understanding of biodiversity.
The millions of different chemical compounds that make up everything on Earth are composed of 118 elements that bond together in different ways. This module explores two common types of chemical bonds: covalent and ionic. The module presents chemical bonding on a sliding scale from pure covalent to pure ionic, depending on differences in the electronegativity of the bonding atoms. Highlights from three centuries of scientific inquiry into chemical bonding include Isaac Newton’s ‘forces’, Gilbert Lewis’s dot structures, and Linus Pauling’s application of the principles of quantum mechanics.
Chemical equations are an efficient way to describe chemical reactions. This module explains the shorthand notation used to express how atoms are rearranged to make new compounds during a chemical reaction. It shows how balanced chemical equations convey proportions of each reactant and product involved. The module traces the development of chemical equations over the past four centuries as our understanding of chemical processes grew. A look at chemical equations reveals that nothing is lost and nothing is gained in a typical chemical reaction–matter simply changes form.
This modules explores the variety of chemical reactions by grouping them into general types. We look at synthesis, decomposition, single replacement, double replacement, REDOX (including combustion), and acid-base reactions, with examples of each.
This module explores the study of reaction rates and the variables that can speed them up or slow them down, also known as chemical reaction kinetics. Through real-life examples, we examine our understanding of chemical reaction products, and the developments scientists have made in manipulating them.
Although weather can change every day, climate is the average of daily weather conditions over decades. This module presents factors that influence climate around the world, such as the shape, tilt, and orbit of Earth. Starting with observations of early ocean travelers and progressing through others’ ideas over later centuries, the module describes how we came to understand Earth’s climate. Also discussed is the imbalance of energy from incoming vs. outgoing radiation and its effect on wind and ocean currents.
Biological oceanographer Kevin Arrigo investigates questions about changes in polar ecosystems due to a changing climate. This research profile explores Arrigo's expeditions in the Arctic Ocean and examines the different influences on Arrigo’s research projects and his career in general. Factors that guide research are discussed, from obtaining funding, to planning research projects, to conducting research in the field.
Comparing and contrasting is a critical research tool for making sense of the world. Through scenarios in which scientists would likely choose to do comparative research, this module explores the differences and similarities between comparison and experimentation. Studies of the link between cigarette smoking and health illustrate how comparison along with other research methods provided solid evidence that cigarette smoke is a major cause of lung cancer.
With a warming climate around the world, astounding archaeological finds have been melting out of ice patches. This module profiles the work of Craig Lee, a leader in the emerging field of ice patch archaeology in North America. The module emphasizes the importance of collaboration between archaeologists, tribal groups, and US government entities in an effort to appropriately collect, protect, and interpret culturally sensitive artifacts found on ancestral Native American lands. Topics include research methods and the multidisciplinary nature of the work.
This module is the first in a series that discusses the discovery, structure, and function of DNA. Key experiments are discussed: from Griffith’s discovery of genetic “transformation” to Avery, MacLeod, and McCarty’s determination of the “transforming agent” to confirmation by Hershey and Chase of DNA rather than protein as the genetic material.
Exploration of the structure of DNA sheds light on fascinating properties of the molecule. This module, the second in a series, highlights major discoveries, from the parts of a nucleotide - the building blocks of DNA - to the double helix structure of the DNA molecule. The module describes scientific developments that led to an understanding of the mechanism by which DNA replicates itself.
In the field of molecular biology, scientists examine how DNA encodes all the complexities of living things. This third module in the DNA series focuses in the process by which DNA is replicated. The module describes the DNA synthesis assay, where scientists were able to replicate DNA in a test tube. Advancements in understanding the features and properties of DNA replication are discussed.
Data analysis is at the heart of any scientific investigation. Using weather as an example, this module takes readers through the steps of data collection, analysis, interpretation, and evaluation. The module explores how scientists collect and record data, find patterns in data, explain those patterns, and share their research with the larger scientific community.
This module profiles renowned AIDS researcher David Ho, who is credited with inventing the “AIDS cocktail” that has saved millions of lives. The module traces Ho’s journey from entering Los Angeles public schools at age 12 as a Taiwanese immigrant with no English to being named Time Magazine’s “Man of the Year” and being awarded the Presidential Citizens Medal for combating the HIV/AIDS epidemic. Topics include how the HIV virus replicates and mutates and how effective drugs target the biology of HIV. Also described is Ho’s work toward equality in HIV care around the world and among underserved populations in the US.
The concept of energy has fascinated scientists and philosophers for thousands of years. This module describes early ideas about energy and traces the development of our modern understanding of energy through the work of Joule and Faraday. Potential and kinetic energy are distinguished, and the six main forms of energy are described. The module highlights energy conversion and discusses how energy is measured.
The study of minerals provides a window into the history of Earth and other planets in our solar system. This first module in a three-part series describes the history of our understanding of minerals and then defines a mineral, focusing on chemical composition and structure.
The process of diffusion is critical to life, as it is necessary when our lungs exchange gas during breathing and when our cells take in nutrients. This module explains diffusion and describes factors that influence the process. The module looks at historical developments in our understanding of diffusion, from observations of “dancing” particles in the first century BCE to the discovery of Brownian motion to more recent experiments. Topics include concentration gradients, the diffusion coefficient, and advection.
Cells are the basic structural and functional unit of life. This module traces the discovery of the cell in the 1600s and the development of modern cell theory. The module looks at similarities and differences between different types of cells and the relationship between cell structure and function. The Theory of Universal Common Descent is presented along with evidence that all living things on Earth descended from a common ancestor.
Tracking the development of our understanding of the atomic structure of matter, this module begins with the contributions of ancient Greeks, who proposed that matter is made up of small particles. The module then describes how Lavoisier's Law of Conservation of Mass and Proust's Law of Definite Proportions contributed to Dalton's modern atomic theory.
This module explores the role ecosystems provide in supplying humans with a wealth of life-supporting resources like clean water, climate control, nutrient cycling, and many others. These are called ecosystem services. Further in the module, we’ll explore the financial value placed on ecosystem services and how this value helps guide decisions regarding use of land and water.
The study of electricity and magnetism were artfully united in John Clerk Maxwell’s theory of electromagnetism. This module explores the experimental connection between electricity and magnetism, beginning with the work of Oersted, Ampere, and Faraday. The module gives an overview of the electromagnetic nature of light and its properties, as predicted by Maxwell’s mathematical model.
Although she was rejected by the space program initially, Ellen Ochoa went on to become the first Hispanic woman to travel in space and was ultimately named Director of the Johnson Space Center. This module takes an in-depth look at the life and career of Ellen Ochoa, from considering a flute-playing career to getting a PhD in electrical engineering and becoming an astronaut. The module describes scientific research projects in space and how they contribute to our understanding of Earth.
Food fuels our bodies, but how does our body convert food molecules into usable energy? This module looks at glycolysis and the Krebs cycle, two important stages of cellular respiration, the process by which cells harvest energy from food. It highlights the work of Sir Hans Adolf Krebs and his focus on cyclic pathways as he discovered the main biochemical pathway for breaking down fuel to produce energy.
ATP is the main energy currency of living cells. This module answers the question of how most ATP is generated. A look at two important compounds, NADH and FADH2, reveals their important role in the production of ATP. The module explains the workings of the electron transport chain, which provides high-energy electrons to fuel the ATP-producing process called oxidative phosphorylation.
Manipulating and controlling variables are key aspects that set experimentation apart from other scientific research methods. This module highlights the principles of experimentation through examples from history, including the work of Alhazen in 1000 CE and Louis Pasteur in the 1860s.
This module introduces exponential equations of the form N=N0 ekt, which describe growth or decay over time. Such equations can be used to predict the spread of a virus, the growth of a population, chemical reaction rates, or the age of a material based on radioactive decay. The constants e and k are explained, and their role in exponential equations is demonstrated. The module takes readers through sample exponential equations that use e in calculating bacteria growth and in radiocarbon dating.
Franklin Chang Díaz, the first Latin American to travel to space, ties the record for the highest number of space flights. This module traces Chang Diaz’s life and career from his boyhood in Costa Rica where he built his own mini rockets, to his emigration and studies of plasma physics in the US, through his career as an astronaut, and beyond. The module describes Chang Diaz’s work toward a plasma-based rocket engine that could radically change space travel, his ongoing crusade on behalf of the environment, and his induction into NASA’s Astronaut Hall of Fame.
Some noted modern scientists have declared that human evolution is over. With advances in medicine and public health, natural selection is no longer a major shaping force for humans. Even so, it doesn’t mean that humans won’t evolve. This module explores the various directions that human evolution might take. Various influences on human evolution are discussed by way of specific examples, including artificial selection through surgical advances and how “bottlenecking” could affect the human gene pool if distant space colonies are formed in the future.
Through a look at the devastating Tay-Sachs disease and other hereditary conditions, this module explores the connection between genes and enzymes. The role of dominance vs. recessivity is examined. The module traces developments in our understanding of gene expression, starting with a rediscovery of Mendel’s laws of inheritance and built upon by the pioneering work of later scientists. The module introduces the Central Dogma of molecular biology, which is the one-way process of using DNA to make RNA and RNA to make proteins.
Isaac Newton's description of gravity was not the first explanation of this phenomenon, nor was it the last. This module explores how Newton built on the work of early astronomers and how his theory was confirmed and built upon by others. Mathematical equations are presented for (1) the Law of Universal Gravitation, (2) the Gravitational Constant, (3) Earth's mass, and (4) the gravitational attraction between two people.
This module looks at how the Earth's atmosphere has changed since the planet came into existence. Starting with clues provided by neon gas, the module traces how scientists have pieced together the story of Earth’s atmosphere. Techniques are described for determining the concentration of elements found on Earth as well as those on planets and stars that are too far away to allow scientists to collect samples.
Minerals are classified on the basis of their chemical composition, which is expressed in their physical properties. This module, the second in a series on minerals, describes the physical properties that are commonly used to identify minerals. These include color, crystal form, hardness, density, luster, and cleavage.
The power of Mendel’s scientific approach can be seen in the research that led to his Second Law. This module, the second in a series, provides details on Mendel's work with dihybrid crosses and independent assortment. The module describes tests that confirmed Mendel’s ideas about the random and independent segregation of genetic factors.
This module describes the experiments that resulted in Mendel's Laws of Inheritance. A look at specific traits in pea plants over generations shows how Mendel's research methods resulted in an understanding of dominant and recessive genes. Partial dominance is also discussed.
Scientists look to uncover trends and relationships in data. This is where descriptive statistics is an important tool, allowing scientists to quickly summarize the key characteristics of a population or dataset. The module explains median, mean, and standard deviation and explores the concepts of normal and non-normal distribution. Sample problems show readers how to perform basic statistical operations.
Many techniques have been developed to aid scientists in making sense of their data. This module explores inferential statistics, an invaluable tool that helps scientists uncover patterns and relationships in a dataset, make judgments about data, and apply observations about a smaller set of data to a much larger group. The module explains the importance of random sampling to avoid bias. Other concepts include populations, subsamples, estimation, and the difference between a parameter and a statistic.
Have you ever wondered what it takes to calculate a rocket’s trajectory? In this module, we’ll learn about the vector quantities aerospace engineers use to design a rocket’s flight plan. It is because of these measurements and specifications that we can send astronauts into space and ensure their safe return.
Over four hundred years, scientists including Rudolf Clausius and James Clerk Maxwell developed the kinetic-molecular theory (KMT) of gases, which describes how molecule properties relate to the macroscopic behaviors of an ideal gas—a theoretical gas that always obeys the ideal gas equation. KMT provides assumptions about molecule behavior that can be used both as the basis for other theories about molecules and to solve real-world problems.
Fats, oils, waxes, steroids, certain plant pigments, and parts of the cell membrane – these are all lipids. This module explores the world of lipids, a class of compounds produced by both plants and animals. It begins with a look at the chemical reaction that produces soap and then examines the chemical composition of a wide variety of lipid types. Properties and functions of lipids are discussed.
His name may not be familiar, but Mexican chemist Luis Miramontes was instrumental in a discovery that changed the course of human history: the birth control pill. This module traces the life and achievements of Miramontes, not only in the area of hormone synthesis, but in other areas of chemistry as well. Miramontes' advances in pharmaceuticals and petrochemistry are described, including his success in devising a chemical process to remove pollutants from engine exhaust.
Luis Alvarez is less famous for his Nobel prize-winning research into subatomic particles than for his theory on how dinosaurs became extinct. Yet, before he started looking into dinosaurs, Alvarez was credited with a lifetime of major advances in atomic physics. This module traces Alvarez’s application of physics to aircraft safety, Egyptian pyramids, K-electron capture, nuclear bombs, and the hydrogen bubble chamber which led to the discovery of many new subatomic particles.
The most recent mass extinction was about 65 million years ago, well before humans began roaming Earth’s surface and leaving written histories for later generations to find. So, how do scientists reconstruct history from prehistoric times? In this module, we’ll learn some techniques scientists and researchers have used to determine when and how the most substantial extincti
In almost every facet of modern life, values – measurements – play an important role. We count calories for a diet, stores measure the percentage of tax on our purchases, and our doctors measure important physiological indicators, like heart rate and blood pressure. From the earliest documented days in ancient Egypt, systems of measurement have allowed us to weigh and count objects, delineate boundaries, mark time, establish currencies, and describe natural phenomena. Yet, measurement comes with its own series of challenges. From human error and accidents in measuring to variability to the simply unknowable, even the most precise measures come with some margin of error.
Tornadoes, earthquakes, tsunamis, and volcanic activity are all examples of natural hazards with the potential to cause substantial damage to a community or region. However, the potential impact these hazards pose to a region or community depends on a variety of other factors. In this module, we’ll explore the difference between a hazard and a disaster and how we determine a region’s risk for a particular natural hazard.
This module explores radioisotopes resulting from unstable atomic nuclei. You will learn how they decay to give off particles and energy. You will also see how alpha, beta, and gamma radioactive decay can be represented by nuclear equation models. Decay chains can be represented as a series of nuclear equations. Knowing the forms of decay and the half-lives of radioisotopes, applications in radiometric dating and radiation therapy for cancer are discussed.
Ocean currents are responsible for transporting matter and energy across the ocean. They are driven by the wind, Earth’s rotation, and the locations of the continents. In this module, we explore the various methods used to study ocean currents throughout history and how our understanding of them has evolved.
Since prehistoric times, people have pondered how life came to exist. This module describes investigations into the origins of life through history, including Louis Pasteur’s experiments that disproved the long-held idea of spontaneous generation and and later research showing that the emergence of biological molecules from a nonliving environment – or abiogenesis – is not only possible, but likely under the right conditions.
Building on earlier experiments showing how life’s chemical building blocks could form from nonliving material on early Earth, this module explores theories on the next steps needed for life. These include the formation of long polymers, which then fold into complex macromolecules. The module describes experiments in an environment like that of primordial Earth, resulting in the spontaneous emergence of phospholipids, which could form into membranes, paving the way for RNA duplication and the eventual emergence of living cells.
Paleontologists study fossils to understand ancient organisms. While fossils might look simple enough, they provide a heap of information. In this module, we’ll explore the different ways paleontologists use fossils and other ancient remains to gain context on extinction events, the progress of evolution, and even the behaviors of organisms that existed long before us.
Earthquakes and volcanoes can reveal a lot about plate boundaries. This module looks at the nature of tectonic plates and discusses the different boundary types that exist between them – convergent, divergent, and transform. Forces that drive the push and pull of these landmasses are explored.
Population biology is the study of population dynamics and the factors that influence a population’s makeup. In this module, we’ll define “population” in relation to population biology and explore the history of the study. Additionally, we’ll learn about its importance in understanding Earth’s changes and its implications on the environment’s wellbeing.
Changes in the genetic makeup of a population affect the incidence of certain traits and diseases within the population. Beginning with a look at the abnormally high rate of a dangerous health condition in US Amish communities, this module explores forces that affect a population's gene pool. Among them are natural selection, gene flow, and two types of genetic drift: founder effects and bottleneck events. The Harvey-Weinberg Equilibrium equation is presented along with sample problems that show how to calculate the frequency of specific alleles in a population.
This module describes the properties of gases and explores how these properties relate to a common set of behaviors called the gas laws. With a focus on Boyle’s Law, Charles’s Law, and Avogadro’s Law, an overview of 400 years of research shows the development of our understanding of gas behavior. The module presents the ideal gas equation and explains when this equation can—and cannot—be used to predict the behavior of real gases.
When it comes to different liquids, some mix well while others don’t; some pour quickly while others flow slowly. This module provides a foundation for considering states of matter in all their complexity. It explains the basic properties of liquids, and explores how intermolecular forces determine their behavior. The concepts of cohesion, adhesion, and viscosity are defined. The module also examines how temperature and molecule size and type affect the properties of liquids.
Solids are formed when the forces holding atoms or molecules together are stronger than the energy moving them apart. This module shows how the structure and composition of various solids determine their properties, including conductivity, solubility, density, and melting point. The module distinguishes the two main categories of solids: crystalline and amorphous. It then describes the four types of crystalline solids: molecular, network, ionic, and metallic. A look at different solids makes clear how atomic and molecular structure drives function.
Living things reproduce either by making exact copies of themselves (asexual reproduction) or by combining genes from two parents (sexual reproduction). Asexual reproduction is simple and fast and is used by bacteria, most other microbes, and some plants and animals. Sexual reproduction is more complicated but creates unique offspring, which helps species survive in changing environments. In this module, we’ll find out why some organisms, like aphids, use both methods and how sexual reproduction keeps life diverse and adaptable.
Through history, important scientific advances have been made in connection with brewing beer. The module begins at the Guinness Brewery with the development of an important mathematical tool for inferential statistics. The focus of the module is confidence intervals, used when making statements about the relationship between a subsample and an entire population. Readers are shown how to construct and report a confidence interval. Topics include Student’s t-distribution, confidence level, critical value, and margin of error. Examples and a sample problem illustrate concepts introduced.
This module explores substances through hypothetical and real-world examples. Substances are broadly classified as pure substances, such as elements and compounds, or mixtures, such as rainwater, but the classification system goes further. How a substance is classified depends on its makeup and properties, and understanding the differences helps scientists solve major issues, such as creating clean drinking water.
Modern taxonomy officially began in 1758 with Systema Naturae, the classic work by Carolus Linnaeus. This module, the first in a two-part series on species taxonomy, focuses on Linnaeus’ system for classifying and naming plants and animals. The module discusses the contribution of diverse cultures to the development of our modern biological classification and describes the historical development of a scientific basis for classifying species.
Carolus Linnaeus, the “father of taxonomy,” developed a uniform system for naming plants and animals to ensure that each species has a unique name. This module outlines rules of forming two-term taxonomic names according to genus and species. The module gives examples of naming controversies and describes how they were resolved, including by bending the rules in regard to certain famous beasts.
This module provides an introduction to the relationship between energy, heat, and temperature. The principle behind thermometers is explained, beginning with Galileo’s thermoscope in 1597. The module compares the three major temperature scales: Fahrenheit, Celsius, and Kelvin. It discusses how the different systems use different references to quantify heat energy.
Carbon, the fourth most abundant element in the universe, moves between the atmosphere, oceans, biosphere, and geosphere in what is called the carbon cycle. This module provides an overview of the global carbon cycle, one of the major biogeochemical cycles. The module explains geological and biological components of the cycle. Major sources and sinks of carbon are discussed, as well as the impact of human activities on global carbon levels.
Powered by the sun, water constantly cycles through the Earth and its atmosphere. This module discusses the hydrologic cycle, including the various water reservoirs in the oceans, in the air, and on the land. The module addresses connections between the hydrologic cycle, climate, and the impacts humans have had on the cycle.
The mole is an important concept for talking about a very large number of things — 6.02 x 1023 of them to be exact. This module shows how the mole, known as Avogadro’s number, is key to calculating quantities of atoms and molecules. It describes 19th-century developments that led to the concept of the mole, Topics include atomic weight, molecular weight, and molar mass. Sample equations illustrate how molar mass and Avogadro’s number act as conversion factors to determine the amount of a substance and its mass.
For centuries, controversy over whether light is made of particles or waves abounded. This module traces the controversy over time, from Isaac Newton's "corpuscle" (particle) theory, which prevailed for centuries, to Thomas Young's groundbreaking double slit experiment, which provided evidence that light traveled in waves.
The periodic table can be used to predict bonding patterns among different elements, based on the number of electrons in an atom’s outer shell. The module explains how electron shells, subshells, and orbitals affect valency, an atom’s bonding capacity—and how this knowledge has helped win the war on AIDS. Applying knowledge of electron configuration, scientists can create brand-new drugs, such as Crixivan, which has saved the lives of over 9.5 million people infected with HIV.
Chemical families are groups of elements that are located near each other on the periodic table and have similar properties. This module looks at the characteristics of each of the ten chemical families, which are determined by how electrons are arranged around the atom’s nucleus. The module explains how chemical families are organized on the periodic table from most-to-least metallic and what this means in terms of chemical reactions.
All living organisms need phosphorous to survive and grow. This module describes forms that phosphorous takes in nature and how the element cycles through the natural world. A historical journey highlights how we came to understand this vital element. The Experimental Lakes Project shows the harmful effects of too much phosphorous on the environment as a result of human activities.
Earth’s materials are in constant flux. Some processes that shape the Earth happen quickly; others take millions of years. This module describes the rock cycle, including the historical development of the concept. The relationship between uniformitarianism, the rock cycle, and plate tectonics is explored in general and through the specific example of the Cascade Range in the Pacific Northwest.
Understanding the structure of silicate minerals makes it possible to identify 95% of the rocks on Earth. This module covers the structure of silicates, the most common minerals in the Earth's crust. The module explains the significance of the silica tetrahedron and describes the variety of shapes it takes. X-ray diffraction is discussed in relation to understanding the atomic structure of minerals.
Without heat flow, nothing can move, no chemical reactions can take place, and no machines can run. This module introduces the concepts of heat and thermodynamics. It explains early ideas about heat and how scientists came to understand that heat and work are two different forms of the same thing. The First Law of Thermodynamics is described (simply put, energy cannot be created or destroyed). Other topics include latent heat and the measurement of heat.
Using genetic markers passed down through the male or female line, scientists can construct family trees going back thousands of years. This module introduces haplotypes – genetic sequences that we inherit from only one parent. As an example, the module looks at the degree of interbreeding between now-extinct Neanderthals and modern humans as determined through an analysis of Y-chromosome haplotypes (male lineage) and mitochondrial DNA haplotypes (female lineage).
Trophic ecology is the study of feeding relationship structures between organisms in a community. This module explores how scientists use various models like food chains and food webs to understand feeding relationships. We’ll also explore how scientists have tested theories on food chain and web length and how the different levels of a feeding structure interact to help define an ecosystem.
There is uncertainty in all scientific data, and even the best scientists find some degree of error in their measurements. This module uses familiar topics - playing baseball, shooting targets, and calculating the age of an object - to show how scientists identify and measure error and uncertainty, which are reported in terms of confidence.
The air has less oxygen at high altitudes, and the physiology of the body changes dramatically as a result. This module profiles the work of Peruvian physiologist Fabiola León-Velarde, who has significantly advanced the world’s understanding of mountain sickness. The module traces Leon-Velarde’s research and accomplishments while educating readers on changes to the body at high altitudes. Several health effects of high altitude are explored in detail.
Using a brief history of scientific writing, this module provides an introduction to the structure and content of scientific journal articles. Key differences between scientific journals and popular media are explained, and basic parts of a scientific article are described through a specific example. The module offers advice on how to approach the reading of a scientific article.
Water in the atmosphere is responsible for moving precipitation around the planet and contributing to the characteristics of Earth’s various climatic zones. The amount of water in the atmosphere varies due to daily temperature and pressure changes, as well as from the global prevailing wind directions and speeds. As global temperatures change, the amount of water vapor in the atmosphere will also change.
Waves, circles, and triangles are closely related. In fact, this relatedness forms the basis of trigonometry. Basic trigonometric functions are explained in this module and applied to describe wave behavior. The module presents Cartesian coordinate (x, y) graphing, and shows how the sine function is used to plot a wave on a graph.
Waves have been of interest to philosophers and scientists alike for thousands of years. This module introduces the history of wave theory and offers basic explanations of longitudinal and transverse waves. Wave periods are described in terms of amplitude and length. Wave motion and the concepts of wave speed and frequency are also explored.
Before you go out for the day, you probably check the weather to help determine what you should wear. Today, forecasts are common, and many of us take for granted how easily we can look up the weather. But how did farmers, sailors, and everyone else know what to expect before the conveniences of today? In this module, we will explore the history of meteorology, the individuals who began collecting weather data and making forecasts, and how those same concepts and measurements are used today.
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