Biologia

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Did you know that carbohydrates, the main source of energy for the human body, are made of different types of sugar molecules? Depending on their molecular structure, some carbohydrates are broken down quickly in the body to release as energy; others need a special enzyme to digest; and still others cannot be digested at all by humans.

Resumen

Our bodies are efficient chemical processing plants, breaking down nutrients to use and store for energy. This module introduces carbohydrates, an important macronutrient. It explains how different carbohydrates are used by plants and animals. Simple sugars and complex carbohydrates are identified, and their biochemical structures are compared and contrasted.

• NGSS

• HS-C6.2, HS-LS1.C2

Conceptos Clave

• Carbohydrates are a class of macronutrients that are essential to living organisms. They are the main energy source for the human body.
• Carbohydrates are organic molecules in which carbon (C) bonds with hydrogen and oxygen (H₂O) in different ratios depending on the specific carbohydrate.
• Plants harvest energy from the sun and manufacture carbohydrates during photosynthesis. In a reverse process, animals break down carbohydrates during metabolism to release energy.
• All carbohydrates are made up of units of sugar. There are two types of carbohydrates: simple sugars – the monosaccharides and disaccharides – and complex carbohydrates – the polysaccharides, which are polymers of the simple sugars.
• Examples of complex carbohydrates are starch (the principal polysaccharide used by plants to store glucose for later use as energy), glycogen (the polysaccharide used by animals to store energy), and cellulose (plant fiber).

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Did you know that there are an estimated 100,000 different proteins in the human body? Proteins, one of the major nutrients required by our bodies, are large molecules made up of hundreds, even thousands, of amino acids combined in different ways. Fat is another essential nutrient, providing a reserve supply of energy, insulation and protection for the body, and structure for cells.

Resumen

Fats and proteins are two of the major nutrient groups that our bodies need. This module provides an introduction to these two macronutrients. The basic chemical structure of fats as triglycerides is presented along with the purposes and types of fat. The module also introduces the amazing structure of protein molecules, including the peptide bond, and explains the purpose of proteins.

• NGSS

• HS-C6.2, HS-LS1.C2

Conceptos Clave

• In addition to carbohydrates, fats and proteins are the other two macronutrients required by the human body.
• Fats, a subgroup of lipids, are also known as triglycerides, meaning their molecules are made from one molecule of glycerol and three fatty acids.
• Fats in the body serve mainly as an energy storage system. They are also used as insulation to conserve body heat and protect internal organs, to form the main structural material in cell membranes, and to manufacture steroids and hormones to help regulate the growth and maintenance of tissue.
• Fats are classified as saturated or unsaturated. Saturated fats contain no double carbon-carbon bonds in their fatty acid chains and tend to be solid at room temperature. Unsaturated fats contain double carbon-carbon bonds and are generally liquid at room temperature. Unsaturated fats can be either polyunsaturated (many double bonds) or monounsaturated (one or few double bonds).
• Proteins are polymers of hundreds or even thousands of amino acids. Each protein has a different structure and performs a different function in the body. There are around 100,000 different proteins in the human body, each of which is made up of combinations of only 20 amino acids.
• Enzymes are proteins that help to carry out specific chemical reactions in the body.

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Did you know that the human body contains an estimated 100,000 different proteins, all due to the numerous ways that only 20 amino acids can combine? Proteins are large molecules made up of hundreds, even thousands, of amino acids combined in different ways.

Resumen

This module explores how proteins are polymers composed of building blocks called amino acids. Using the historic research of Frederick Sanger on insulin as a starting point, the complex structures of proteins, due to molecular bonds like the disulfide bridge and the peptide bond, are explained.

Conceptos Clave

• Proteins are vital components to nearly every biological process.
• Proteins are polymers composed of building blocks called amino acids, of which life on Earth uses just twenty.
• Molecular bonds determine the structures of amino acids and proteins. Peptide bonds link amino acids together in a chain; disulfide bridge bonds hold proteins together.
• Using techniques like electrophoresis and chromatography, Frederick Sanger discovered that proteins were built of specific amino acid sequences and that changing the sequence would make it a different protein.
• Proteins can have four types of structures: (1) Primary, the sequence of amino acids, (2) Secondary, hydrogen bonds among the strands of amino acids form beta sheets or alpha-helixes, (3) Tertiary, the three-dimensional, twisted structure based on bonding interactions between amino acid strands, and (4) Quartnerary, the complex structure made up of multiple folded subunits.

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Did you know that in the early days of blood transfusions, more people died than survived them? All blood looks pretty much the same to the naked eye, but blood that is lifesaving for one person may be deadly to another. Transfusions became a safe medical procedure only when scientists came to understand the complexity of blood components and different blood types.

Resumen

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.

Conceptos Clave

• Blood is a complex fluid with many different components, but can be divided into solids (red blood cells, white blood cells, and platelets) and liquid (plasma).
• Blood plasma includes clotting factors (agents that help to form blood clots) and when these are removed, the remaining liquid is known as serum.
• The main cellular components of blood are: red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes).
• The Austrian researcher Karl Landsteiner studied agglutination, or clumping together of blood cells with certain antigens. Based on his findings, he proposed that there were three types of blood (A, B, O) and later added a fourth type (AB).
• Antibodies are proteins produced by plasma cells, a type of B-cell lymphocyte, and are present in the blood serum. These antibodies are important for blood transfusion, since the blood type of a patient and the type of antibodies present in the donor’s blood will determine whether or not it agglutinates or clumps.

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Did you know that studying lipids can help us understand and treat medical conditions such as heart disease, hormone disorders, multiple sclerosis, and many others? Lipids are necessary for the structure of all living cells. Their chemical composition allows them to have many important functions, from storing energy to regulating metabolism to helping the fur coat of sea otters repel water.

Resumen

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.

• NGSS

• HS-C6.2, HS-LS1.C2

Conceptos Clave

• Lipids are a large and diverse class of biological molecules marked by their being hydrophobic, or unable to dissolve in water.
• The hydrophobic nature of lipids stems from the many nonpolar covalent bonds. Water, on the other hand, has polar covalent bonds and mixes well only with other polar or charged compounds.
• Fats and oils are high-energy molecules used by organisms to store and transfer chemical energy. The distinct structures of different fat molecules gives them different properties.
• Phospholipids are specialized lipids that are partially soluble in water. This dual nature allows them to form structures called membranes which surround all living cells.

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¿Sabia usted que el cuerpo humano consiste de miles de millones células individuales y 200 tipos distintos de células? Las células humanas varían en tamaño desde 1/12,000 de pulgada (un par de micrómetros) hasta mas de 39 pulgadas (Mas de un metro) de largo. Todos los seres vivientes son hechos de células, pero a pesar de la diferencia en tamaño, forma y función, estas bases de vida comparten similitudes increíbles.

Resumen

Las células son la unidad estructural y funcional básica de la vida. Este módulo traza el descubrimiento de la célula en la década de 1600 y el desarrollo de la teoría celular moderna. Este módulo explora las similitudes y diferencias entre diferentes tipos de células y la relación entre estructura celular y función. La Teoría de Descenso Común Universal se presenta junto con evidencia de que todos los seres vivientes en la Tierra descendieron de un ancestro común.

• NGSS

• HS-C6.1, HS-LS1.A1

Conceptos Clave

• Las células son la unidad estructural y funcional básica de todos los seres vivientes y contienen material genético heredable.
• La actividad de una célula se lleva a cabo por las estructuras sub-celulares que posee.
• Las células poseen una capa externa, llamada membrana celular, citoplasma, el cual contiene orgánulos y también material genético.
• Existe variedad considerable entre células vivientes, incluyendo la función de membranas y estructuras sub-celulares, y los diferentes tupos de funciones que llevan a cabo las células, tales como el transporte de químicos, el apoyo y otras funciones.

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Did you know that Benjamin Franklin’s 1774 experiments with pouring oil onto a pond of water was an early step in gaining a scientific understanding of cell membranes? Cell membranes were thought to be passive barriers until the 1960s, but we now know that they are active and responsive structures that serve a critical function as gatekeepers and communicators.

Resumen

Cell membranes are much more than passive barriers; they are complex and dynamic structures that control what enters and leaves the cell. This module explores how scientists came to understand cell membranes, including the experiments that led to the development of the fluid-mosaic model of membrane structure. The module describes how the components and structure of cell membranes relate to key functions.

• NGSS

• HS-C6.2, HS-LS1.A1

Conceptos Clave

• La capa externa de una célula o una membrana celular, es una estructura compleja con muchos diferentes tipos de moléculas que están en movimiento constante, moviéndose fluidamente por la membrana.
• Membranas celulares forman barreras selectivas que protegen la célula del ambiente aguado que los rodea mientras permiten que moléculas insolubles en agua como el oxigeno, dióxido de carbono y algunas hormonas que pasen.
• La mayoría de la membrana celular se forma por fosfolípidos que tienen una estructura única que los causa que se arreglen automáticamente en una capa doble que es hidrofóbica en medio e hidrófila afuera.

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¿Sabia usted que la ausencia de un pequeño aminoácido en membranas celulares causa fibrosis quística, una enfermedad que amenaza la vida? Y una enfermedad mas común, la acidez se trata con medicina que atrasa la frecuencia en la cual proteínas son empujadas a través de membranas celulares en el estomago. Estudiando como viajan las moléculas a través de membrana plasmática (membrana celular) es la clave para entender y tratar muchas condiciones medicas.

Resumen

Para que las cosas vivientes sobrevivan, diferentes moléculas necesitan entrar y salir de células, sin embargo las membranas de células sirven como una barrera a la mayoría de las moléculas. Afortunadamente, todas las células vivientes tienen transportadores incluidos que permite que el agua, la glucosa, el sodio, el potasio, el cloro y otras moléculas crucen la membrana de plasma. Este módulo mira como funcionan los transportadores activos y pasivos. Resalta la importancia del estudio de membranas celulares viendo avances en el tratamiento de fibrosis quística y enfermedades digestivas comunes y así mismo los desarrollos de analgésicos efectivos.

• NGSS

• HS-C6.2, HS-LS1.A1, HS-LS1.C3

Conceptos Clave

• Ya sea que una molécula puede pasar fácilmente o no hacia adentro o hacia fuera de una célula es altamente dependiente de su carga y solubilidad en el agua.
• La membrana de plasma sirve como una barrera semi permeable a la célula. Solamente moléculas sin carga, no polares pueden pasar hacia adentro o hacia fuera de una célula sin ayuda.
• Todas las membranas de plasma poseen transportadores para ayudar a mover moléculas de un lado de la membrana a otro. Estos transportadores pueden ser activos (bombas) o pasivos (canales) y son en veces reguladas por puertas.
• La falta de transportadores específicos pueden interrumpir funciones celulares y causar enfermedades como la fibrosis quística.
• Investigación en analgésicos proveen información acerca de el transportador mas importante y mas universal en el cuerpo humano, la bomba de sodio y potasio.

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Did you know that “survival of the fittest” is not the only explanation for the success of a species over time? Cooperation can be just as important when it comes to how species adapt in order to survive. According to Lynn Margulis, who proposed that modern-day mitochondria and chloroplasts evolved through endosymbiosis, “Life did not take over the globe by combat, but by networking.”

Resumen

Evolution isn't always about competition. It can also be about cooperation, as is the case with the development of chloroplasts and mitochondria from free-living bacteria. This module explains the theory of endosymbiosis along with its origins. Convincing evidence in support of the theory is presented. The evolution of the nucleus and other organelles through invagination of the cell membrane is also discussed.

• NGSS

• HS-C6.1, HS-C6.2, HS-LS1.A1, HS-LS1.A3

Conceptos Clave

• Una de las mayores diferencias entre células eucariotas y células procariotas es la presencia de un núcleo y otros orgánulos membranosos.
• Cloroplastos y mitocondria tienen papeles especializados en la producción de energía para la célula y tienen varias características únicas incluyendo alguno de su propio ADN. Debido a esto, los científicos creen que ambos de estos orgánulos originaron por medio de las endosimbiosis cuando una célula pequeña comienza a vivir dentro de una mas grande.
• Orgánulos membranosos evolucionaron como dobleces de la membrana plasmática; esto permitió que estas células establecieran compartimientos con diferentes ambientes apropiados para la función especifica que lleva a cabo el orgánulo.

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Did you know that every organ and tissue in your body was formed as the result of individual cells making copies of their DNA and separating themselves into two identical cells? From experiments in the 1870s to research more than 100 years later, scientists have made fascinating discoveries about the complex series of events that allow the cells in plants and animals, including humans, to grow and sustain life.

Resumen

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.

• NGSS

• HS-C6.2, HS-LS1.B1

Conceptos Clave

• La mayoría de las células que forman a organismos mas complejos como animales, como los animales vertebrados y plantas con flores, se reproducen via un proceso llamado división celular.
• En la división celular, las células hace una copia de su ADN y después se separa en dos células idénticas - cada una con su propia copia de ADN envuelta dentro del núcleo.
• El termino mitosis se refiere específicamente al proceso en donde el núcleo de la célula madre se divide en dos núcleos idénticos.

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¿Sabia usted que existe una gran variación en el numero de cromosomas en seres vivientes? Mientras que humanos tienen 46 cromosomas y perros tienen 78, un tipo de hormiga tiene solamente 2 cromosomas y un tipo de protozoo tiene casi 16,000! Pero lo que todos estos seres vivientes tienen en común es que su código genético es copiado de célula a célula gracias a un proceso llamado mitosis, en donde el núcleo de una célula se separa antes de que se divide la célula.

Resumen

Comenzando con el descubrimiento de mitosis, este módulo detalla cada fase de este proceso. Provee una vista general de la estructura de componentes celulares que son críticos en la mitosis. El módulo describe los experimentos de Clarke Noble con el bígaro de Madagascar, el cual llevó al descubrimiento de una droga de tratamiento efectivo para el cáncer. La relación entre mitosis y cáncer se explora tal como es el mecanismo por el cual las drogas de anti cáncer trabajan para atrasar o prevenir la división celular.

• NGSS

• HS-C6.2, HS-LS1.A1, HS-LS1.B1

Conceptos Clave

• El termino mitosis se refiere específicamente al proceso en el cual el núcleo de células eucariotas se divide en dos núcleos idénticos antes de la división celular.
• Mitosis es un proceso cíclico que consiste de cinco fases que alimentan el uno al otro: profase, prometafase, metafase, anafase y telofase.
• El ritmo en el cual ocurre la mitosis depende del tipo de célula. Algunas células se replican mas rápidamente y otras mas lentamente y el proceso entero puede ser interrumpido.
• Las cromosomas consisten de un material llamado cromatina, el cual se dispersa a través del núcleo de la célula durante interfase. Sin embargo, durante el mitosis la cromatina se condensa haciendo que cada cromosoma individual sea visible bajo una luz ordinaria microscópica.

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Sabia usted de que la mayoría de los químicos con los que interactuamos – incluyendo la comida que comemos – debe pasar por un sistema complejo de membranas celulares antes de que entren en el flujo sanguíneo? Existen muchas diferentes maneras de que los químicos entren el cuerpo, dependiendo en el tipo de químico y la parte del cuerpo con el cual interactúa.

Resumen

Para que muchas medicinas trabajen, los químicos deben desplazarse del ambiente externo hacia el cuerpo. Este módulo discute los diferentes mecanismos por el cual los químicos cruzan la membrana celular y los factores que influyen el proceso. Adicionalmente a introducir la absorción biológica, este módulo explica como los químicos son almacenados y distribuidos dentro del cuerpo.

• NGSS

• HS-C5.4, HS-LS1.C3

Conceptos Clave

• Chemicals can enter the human body by several methods, but most must pass through living cell membranes before entering the bloodstream.
• The cell membrane consists mainly of phospholipids and proteins in the form of a lipid bilayer.
• Mechanisms for moving chemicals through the cell membrane include: passive diffusion, facilitated diffusion, active transport, and endocytosis.
• Factors such as human anatomy and chemical structures affect the movement of chemicals in the body.

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Did you know similar to the way cars are manufactured, chemical compounds in living cells are built up, broken down, and moved around in assembly-line fashion? In living organisms, a series of reactions is needed to get energy from food molecules. One such important chemical pathway is the circular assembly line known as the Krebs cycle.

Resumen

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.

• NGSS

• HS-C5.2, HS-LS1.C4

Conceptos Clave

• In a cell, chemical compounds are put together, taken apart, and moved around through pathways that resemble moving assembly lines.
• The main types of biological macromolecules that cells use for fuel are sugars, fats, and proteins.
• The main biochemical pathway where the breakdown of biological fuels comes together is called the Krebs cycle. Named for its discoverer, Sir Hans Adolf Krebs, this pathway is like a circular assembly line.

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Did you know that the energy in chemical compounds is found in tiny electrons? The electron transport chain is like an assembly line inside of cells that harnesses high-energy electrons so they can be used to make ATP, the energy that organisms need to survive. When Peter Mitchell proposed the way that ATP is made inside cells, other scientists made fun of him – until he was eventually proved correct and won the Nobel Prize in Chemistry.

Resumen

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.

• NGSS

• HS-C5.2, HS-LS1.C4

Conceptos Clave

• Adenosine triphosphate (ATP) is the main energy currency of the cell. It is generated from a similar compound, ADP, using energy harnessed from cellular fuels, such as sugars, fats, and proteins.
• The amount of ATP generated directly during glycolysis (the breakdown of the sugar glucose) is small compared with amount of energy contained within glucose.
• The energy held by ATP and other energy-holding chemical compounds is contained in electrons. By moving electrons, different molecules move energy around the cell.
• Two specialized energy currency compounds, NADH and FADH₂, are vital to the movement of high-energy electrons from cellular fuels like glucose to an assembly-line system of enzymes called the electron transport chain.
• Located inside mitochondria, the electron transport chain harnesses energy from NADH and FADH₂ to power a process called oxidative phosphorylation, which generates large amounts of ATP. Oxidative phosphorylation requires oxygen.

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Did you know that the oxygen we breathe is a waste product? Of photosynthesis, that is. Through this remarkable process, plants capture energy from sunlight and produce the sugars that provide sustenance to nearly every living thing on Earth along with the oxygen we need to survive.

Resumen

Through photosynthesis, plants harvest energy from the sun to produce oxygen and sugar, the basic energy source for all living things. This module introduces photosynthesis, beginning with experiments leading to its discovery. The stages of photosynthesis are explained. Topics include the role of chlorophyll, the action spectrum of photosynthesis, the wavelengths of light that drive photosynthesis, light-harvesting complexes, and the electron transport chain.

• NGSS

• HS-C5.2, HS-C5.4, HS-LS1.C1

Conceptos Clave

• La fotosíntesis es un proceso por el cual un organismo convierte la energía de la luz del solo a energía química para su sustento.
• El fotosíntesis ocurre en plantas, algas y algunas especies de bacteria.
• En plantas, los cloroplastos contienen clorofila, el cual absorbe la luz en regiones de rojo y azul-violeta del espectro.
• La fotosíntesis ocurre en dos etapas, la etapa dependiente de luz que ocurre en la membrana tilacoide del cloroplasto y cosecha la energía del sol, y la etapa independiente de la luz que toma la energía y hace azúcar del dióxido de carbono.

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Did you know that it is much easier to determine when life appeared on Earth than how life came to exist? Evidence points to life on Earth as early as 3.8 billion years ago, but the question of how life came to be has puzzled scientists and philosophers since prehistoric times. In the 1950s, scientists successfully created biological molecules by recreating the atmosphere of primordial Earth in a bottle and shocking it with lightning. This and other experiments give clues to the origins of life.

Resumen

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.

• NGSS

• HS-C4.2, HS-C4.3, HS-ESS2.E1

Conceptos Clave

• Theories about the origins of life are as ancient as human culture. Greek thinkers like Anaximander thought life originated with spontaneous generation, the idea that small organisms are spontaneously generated from nonliving matter.
• The theory of spontaneous generation was challenged in the 18th and 19th centuries by scientists conducting experiments on the growth of microorganisms. Louis Pasteur, by conducting experiments that showed exposure to fresh air was the cause of microorganism growth, effectively disproved the spontaneous generation theory.
• Abiogenesis, the theory that life evolved from nonliving chemical systems, replaced spontaneous generation as the leading theory for the origin of life.
• Haldane and Oparin theorized that a "soup" of organic molecules on ancient Earth was the source of life's building blocks. Experiments by Miller and Urey showed that likely conditions on early Earth could create the needed organic molecules for life to appear.
• RNA, and through evolutionary processes, DNA and the diversity of life as we know it, likely formed due to chemical reactions among the organic compounds in the "soup" of early Earth.

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Did you know that scientists don’t need time travel to mimic conditions on Earth 4 billion years ago? Scientists who want to experiment in an environment like that of primordial Earth need only to visit volcanoes, which have chemical conditions similar to those on Earth long, long ago. That’s just what chemist David Deamer did in his research into the origins of life. Just as had happened in the lab, Deamer’s volcano experiments produced a necessary step toward the formation of living matter.

Resumen

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.

Conceptos Clave

• For life to occur, smaller molecules must join together and form polymers, which then fold into complex shapes. These large molecules are called macromolecules.
• Simple membranes made of lipids may have served as nature’s test tubes, providing the enclosed environments necessary for RNA enzymes to develop.
• The possible ancestor to living cells, liposomes, may have been created from phospholipids formed from the gases of Earth’s primeval atmosphere or from free fatty acids delivered to ancient Earth via meteorites.
• To trigger abiogenesis, a system of molecules would need to develop the ability to copy themselves using polymers.
• Protocells made of liposomes that exchanged fatty acids between their membranes possibly absorbed RNA enzymes and made copies of themselves, leading to the evolutionary development of living cells.

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¿Sabia usted que la teoría de la evolución no comenzó con Charles Darwin? La idea de la evolución fue parte del pensamiento Occidental por mas de 2,000 años antes que Darwin cambio el mundo con su libro legendario El Origen de las Especies.

Resumen

Las experiencias y observaciones de Charles Darwin contribuyeron significativamente a su teoría de la evolución por medio de la selección natural. Este módulo explora esas influencias y describe la evolución como una fuerza para cambio biológico y la diversificación. El primero en una serie, detalla como la teoría desafió el pensamiento cultural del tiempo, incluyendo el efecto de sus trabajos principales: El Origen de las Especies por Medio de la Selección Natural y El Origen del Hombre y la Selección en Relación al Sexo.

• NGSS

• HS-C1.1, HS-LS4.A1

Conceptos Clave

• Charles Darwin realizo un papel importante en apoyar y explicar la teoría de la evolución por medio de la selección natural.
• Las habilidades de Darwin para observar y su habilidad para recolectar datos con exactitud le permitió crear un modelo comprensivo del mecanismo por el cual ocurre la evolución.
• La teoría de la evolución por medio de la selección natural explica como todas las formas de vida están relacionadas una con el otro genealógicamente, y enfatiza que la variación dentro de las especies es la raíz del cambio evolucionario.

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¿Sabia usted de que la experiencia de Darwin con sus diez hijos fomento su pensamiento acerca de la evolución? Teorizo de que algunos comportamientos humanos, tales como el egoísmo de un niño pequeño, se basaron por medio de instintos que eran adaptaciones. Estas diferencias naturales que siempre existen entre individuos están en el centro del principio de la selección natural como el motor del cambio evolucionario.

Resumen

El segundo en una serie discutiendo el trabajo de Charles Darwin. Este módulo hace una mirada mas profunda en el proceso que llevo a Darwin a la teoría de selección natural y examina mecanismos específicos que forjan el cambio evolucionario. Puntos clave en los cuales la idea de selección natural se basa se perfilan. Ejemplos de la vida personal de Darwin hacen mas claro su pensamiento acerca del cambio dentro de una especie y la "lucha por existir".

• NGSS

• HS-C7.2, HS-LS4.B1, HS-LS4.C1

Conceptos Clave

• Variación dentro de una especie incrementa la posibilidad que tiene por lo menos algunos miembros de la población sobrevivirán bajo condiciones ambientales cambiadas.
• Las características comunes de individuos dentro de una población cambiaran con el tiempo, mientras que los que tienen rasgos ventajosos serán los más comunes y los más extendidos.
• While evidence of evolution by natural selection exists, its effects cannot be predicted.

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¿Sabia usted que Charles Darwin prefería la frase “descendencia con modificaciones” mas que el término simple “evolución”? En su libro innovador El Origen de Las Especies, Darwin escogió sus palabras cuidadosamente. “Evolución” fue utilizada en diferentes maneras en ese entonces, y Darwin quería transmitir el concepto importante de que la formas de vida descendieron de un ancestro común.

Resumen

Nuestro entendimiento del término Evolución ha cambiado significativamente desde el tiempo de Darwin. Este módulo explica como el trabajo de Darwin ayudó a dar a la evolución el significado que tiene hoy en día. Detalla el concepto de “descendencia con modificaciones” que Darwin describió con la figura que Darwin incluyó en El Origen de las Especies . Este módulo discute como este modelo revoluciono el pensamiento científico acerca de las similitudes y diferencias entre especies y dentro de las mismas, dando base para nuestro entendimiento actual de la biodiversidad.

• NGSS

• HS-C2.1, HS-C2.2, HS-LS4.B1, HS-LS4.B2, HS-LS4.C1, HS-LS4.C2

Conceptos Clave

• La teoría de Darwin de la descendencia con modificación muestra como al reproducirse los organismos, cambios leves crean variación, y potencialmente producen nuevas especies con el tiempo.
• Darwin proveyó el primer modelo que podía explicar lógicamente la biodiversidad, explicando linaje y variaciones pequeñas que distinguen a una especie con la otra similar.
El trabajo de Darwin cambio radicalmente el pensamiento de
• la escala de la Naturaleza, un modelo que sugirió que algunas especies eran inferior naturalmente a otros, y mostraba que las especies evolucionaban en respuesta a presiones ambientales y no porque alguna jerarquía de la orden.

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¿Sabia usted que existen especies de polillas con una lengua con una longitud de 12 pulgadas para recolectar néctar? No por casualidad, esta polilla se alimenta y poliniza una tipo de orquídea que tiene un tubo que produce néctar que mide 11 pulgadas. La naturaleza tiene una gran cantidad de ejemplos de plantas y animales que se han adaptado a su ambiente a través del tiempo para asegurar la sobrevivencia de la especie.

Resumen

Este módulo introduce los conceptos de la adaptación evolucionaria. Sigue el desarrollo de las ideas de Charles Darwin acerca de cómo las especies se adaptan a su ambiente para poder sobrevivir y reproducirse. La diferencia entre adaptación y selección natural es explicada. Con una mirada a los pingüinos y otros ejemplos de la naturaleza, el módulo explora el proceso que incluye la diversidad de la vida.

• NGSS

• HS-C6.2, HS-LS4.C2

Conceptos Clave

• Natural selection is the mechanism that explains how organisms change.
• The structure of an organism and many of its features are directly related to the environment in which it lives.
• Numerous environmental mechanisms, both naturally occurring and man-made, influence adaptive evolution.

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¿Sabía usted que se comenzó a clasificar a los seres vivientes en el año 300 AEC? Pero nuestro sistema de clasificación moderna oficialmente comenzó en el siglo XIX cuando Carolus Linnaeus listó todas las plantas y todos los animales conocidos en el mundo – mas de 12,000 en total. Produjo una de las obras grandes en la historia de la ciencia, Systema Naturae, el cual utilizamos aun hoy.

Resumen

La taxonomía moderna comenzó oficialmente en 1757 con Sistema Naturae, la obra clásica por Carolus Linnaeus. Este módulo, el primero en una serie de dos partes acerca de la taxonomía de especie, se enfoca en el sistema de Linnaeus para clasificar y nombrar plantas y animales. Este módulo discute la contribución de la taxonomía popular a la clasificación moderna popular y describe el desarrollo histórico de una base científica para clasificar especies.

• NGSS

• HS-C1.5, MS-LS4.A2

Conceptos Clave

• Bajo el sistema Linnaeus, todas las especies son conocidas por un nombre de genero y de una especie únicas en Latín que los distingue de otras especies.
• El trabajo de Linnaeus organizó a los organismos en clases lógicas basadas en su apariencia y características, y por ende proveía una base para comparar diferentes especies.

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Did you know that Tyrannosaurus rex could have been called Manospondylus gigas? The rules of scientific nomenclature usually dictate that when more than one name for a species is discovered has been given, the older one prevails. Luckily, common sense won out in the case of T. Rex, and this most famous dinosaur was allowed to keep the newer name that both scientists and the general public had become familiar with.

Resumen

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.

• NGSS

• HS-C1.5, MS-LS4.A2

Conceptos Clave

• El sistema de nomenclatura binomial fue la respuesta de Linnaeus a la necesidad de un nombramiento de especies claro y distintivo que pudiera ser reconocido a nivel mundial y reducir la posibilidad de que una especie fuese dada múltiples nombres.
• Nombres científicos siempre están escritos en bastardilla, con el genero capitalizado y la especie en letra minúscula y debe sonar como que si fuese latín.

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Did you know that bones, stones, and tools are often all scientists have to go by to piece together the human family tree? This is the work of paleoanthropologists, who trace human ancestry by analyzing fossilized bones and teeth, tools made by the creatures, and the surrounding sediment and stones. Although pre-human fossils are rarely uncovered, any such find can give great insight into the evolution of humans.

Resumen

Paleoanthropology is the study of human ancestry through fossil remains and other evidence. This module explains how paleoanthropologists uncover and evaluate clues to the lineage to modern humans, tracing intermediate forms along the way since the time we diverged from our cousins, the great apes. Key discoveries are highlighted that shed light on the pathway of human evolution. The module describes different ideas through history about how the human family tree is constructed and which characteristics best define humanness.

Conceptos Clave

• Paleoanthropology is the study of human ancestry through analysis of fossilized bones and teeth, the stones and sediments in which bones are buried, as well as the tools associated with those ancient creatures.
• Charles Darwin first proposed that humans and apes shared a common ancestor in his 1871 publication The Descent of Man.
• Early researchers sought out an ape-man fossil, or a “missing link,” to make a clear lineage from ape to man. However, we know today that the human lineage branches like a tree with many human-like species in a few genera.
• Key discoveries have helped to provide more detail on human evolution, such as Mary and Louis Leakey’s discovery of Homo habilis, but also brought up difficult questions of taxonomic classification.

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Did you know that only half of British children lived to age 21 in Charles Darwin’s time? Thanks to modern medicine and public health measures, most humans in developed countries now survive to adulthood. As survival constantly improves, natural selection is no longer a major force that shapes the human population. However, evolution will likely continue among humans due to other evolutionary forces at work.

Resumen

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.

Conceptos Clave

• Humans continue to evolve due to a variety of evolutionary forces: natural selection, artificial selection, genetic drift, and via transhuman breakthroughs.
• Evolution is the gradual genetic change of a species over time due to unequal reproduction among members.
• Natural selection is the phenomenon that rewards certain advantageous traits and punishes others through better or worse survival or reproduction. Natural selection is one of the forces that moves evolution forward.
• Artificial selection is the selective breeding of animals or plants by humans to modify an organism.
• Genetic drift is a change in the frequency of a population's genes and alleles over time, often by founder effects (when a small group of individuals relocate) or bottlenecking (when a large population is decimated, leaving a smaller group to repopulate).
• Transhumanism is the idea that humans can evolve new physical and mental capabilities, particularly through the use of science and engineering.

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Did you know that the Piltdown Man hoax inspired the development of various scientific tests for authenticating paleoanthropological specimens? From the 1960s onward, scientists developed methods for more accurately finding both the date and geography of origin for materials.

Resumen

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.

Conceptos Clave

• Confirmation bias is the tendency to accept any evidence that seems to support one’s belief while rejecting all evidence that is contrary.
• The 1912 discovery of Piltdown Man was widely hailed as the discovery of the "missing link" between humans and apes, but was really an elaborate deception.
• The hoax perpetrator buried ancient animal bones, flint tools, and both human and ape skull fragments in the English town Piltdown.
• The discoverers of the Piltdown Man were so enthusiastic about their findings that they ignored contradictory evidence and failed to carefully test the bones.
• By the 1940s the scientific community were skeptical of the Piltdown discovery and it was officially declared a hoax in 1953.

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¿Sabia usted que la gente antes creía que versiones miniaturas formadas de sus hijos eran contenidos de células de espermatozoides? Las primeras teorías de reproducción fueron refutadas, pero los patrones de herencia permanecieron un misterio hasta Gregor Mendel realizo sus experimentos con plantas de guisantes en la primera década del siglo XIX

Resumen

Este módulo describe los experimentos que resultaron en La Ley de la Herencia de Mendel . Un vistazo a rasgos específicos en plantas de guisantes a través de las generaciones muestra como los métodos de investigación de Mendel resultaron en un entendimiento de genes dominantes y recesivos. La dominancia parcial también se discute.

• NGSS

• HS-C1.4, HS-C1.5, HS-LS3.A1, HS-LS3.B2, MS-LS4.B2

Conceptos Clave

• Mendel determino que el organismo hereda dos copias de material genético que determina los rasgos físicos de un individuo, una copia que viene del padre y otro de la madre.
• Mendel observo de que para cada rasgo, a veces lo que se hereda de un padre enmascara lo que se heredo del otro. También llamo el rasgo escondido recesivo y el expresado como el rasgo dominante.
• Desde el tiempo de Mendel, otros científicos han observado de que no todos los rasgos son heredados con un patrón simple dominante-recesivo. Dominio incomplete y dominio compartido puede resultar en una variedad de fenotipos para cada rasgo.

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¿Sabia usted de que a Gregor Mendel se le conoce como el “Padre de la Genética” y aun así su trabajo fue en gran medida ignorado por científicos durante su vida? Fue nada mas cuando tres científicos redescubrieron el trabajo de Mendel casi 35 años después de que fue publicado que se llego a apreciar sus implicaciones del entendimiento científico de la herencia

Resumen

El poder del enfoque científico de Mendel puede ser visto el la investigación que llevó a su Segunda Ley. Este módulo, el segundo en una serie, provee detalles acerca del trabajo de Mendel con cruces dihíbridos y la distribución independiente. El módulo describe pruebas que confirmaron las ideas de Mendel acerca de segregación aleatoria e independiente de factores genéticos.

• NGSS

• HS-C1.4, HS-C1.5, HS-LS3.A1, HS-LS3.B2, MS-LS4.B2

Conceptos Clave

• La segunda ley de Mendel, la ley del surtido independiente, mantiene de que los cruces dihíbridos resultan en una expresión de proporción 9:3:3:1 - 9 con rasgos dominantes, 3 con rasgo uno dominante y dos con el rasgo dos dominante y 1 con ambos rasgos recesivos.
• El trabajo de Mendel no fue apreciado por la comunidad científica durante su vida porque su enfoque difería de aquellos que eran popular en ese entonces y los estudios que el llevo a cabo, en la superficie, se parecían en lo que otros habían hecho antes.
• Fue porque Mendel simplificó su enfoque e hizo preguntas mas pequeñas y mas contrastables y pudo plantear ideas como la Ley del Surtido Independiente.
• Fue porque Mendel fue tan metódico en su investigación y completo en documentar cada paso, que le permitió a los científicos repetir sus experimentos y probar los resultados muchos años después de su muerte.

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¿Sabia usted que uno de los descubrimientos mas importantes en la biología fue hecha mientras un oficial medico del ejercito Británico trataba de desarrollar una vacuna para neumonía después de la Primera Guerra Mundial? A pesar de que una vacuna para la neumonía aun no existe, Frederick Griffith descubrió la “transformación”. Esto significa de que organismos pueden ser reprogramados genéticamente en una versión un poco diferente de ellos mismos.

Resumen

Este módulo es el primero en una serie que discute el descubrimiento, la estructura y la función del ADN. Experimentos clave son discutidos: desde el descubrimiento de Griffith de la “transformación“ Genética hasta la determinación de Avery, MacLeoid y McCarty de un “agente de transformación” y hasta la confirmación por Hershey y Chase de ADN en vez de una proteína con material genético.

• NGSS

• HS-C6.1, HS-C6.2, HS-LS1.A2

Conceptos Clave

• Mientras que científicos sabían que los organismos pasaban información en la forma de material genético, se requería numerosos experimentos por muchos científicos para determinar cual era el material genético, y para identificar que el ADN y no la proteína, es el material genético en que se basa la vida.
• Una de las piezas claves de la información que identificaba el ADN como el material genético fue la observación de que las cepas de células bacteria les podrían ser "transformadas" a otras cepas agregándoles ADN de diferentitas bacterias.

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¿Sabia usted que las combinaciones precisas de cuatro bases de nitrógeno forman miles de millones de nucleótidos que constituyen nuestras moléculas de ADN únicas? Esta información es almacenada en la secuencia de base de una sola hebra de ADN incluye toda la información genética en su cuerpo y nos da nuestros rasgos genéticos individuales.

Resumen

La exploración de la estructura de ADN aclara las propiedades fascinantes de la molécula. Este modulo, el segundo de una serie, resalta descubrimientos importantes, desde las partes de un nucleótido - las bases del ADN - hasta la estructura del doble hélice de la molécula de ADN. Este módulo describe desarrollos científicos que llevaron al entendimiento del mecanismo del cual se replica el ADN.

• NGSS

• HS-C6.1, HS-C6.2, HS-LS1.A2, HS-LS3.B1

Conceptos Clave

• El ADN consiste de dos hileras de unidades que se repiten y que se llaman nucleótidos. Cada nucleótido está hecho de azúcar de 5 carbonos, de un grupo de fosfatos y de una base de nitrógeno.
• La secuencia específica de los cuatro nucleótidos diferentes que forman el organismo del ADN es la que le da a este organismo sus rasgos genéticos únicos.
• Las cuatro bases de nitrogeno son complementarias (adenina con timina, citosina con guanina) y los pares forman enlaces de hidrógeno cuando las puntas 5'/3' de los grupos de ázucar y fosfato están en dirección anti-paralela.

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¿Sabia usted que el ADN en el cuerpo humano debe de hacer copias exactas de si mismo no solamente miles de veces, no millones de veces, y ni siquiera miles de millones de veces, si no que mas de cientos de miles de millones de veces? Dentro de la levadura, dentro de una bacteria o dentro de una célula humana, cada célula viviente debe de poder copiar todo su ADN con una exactitud increíble.

Resumen

En el campo de biología molecular, científicos examinan como el ADN graba las complejidades de todas las cosas vivientes. Este tercer módulo en la serie de ADN se enfoca en el proceso en la que se replica el ADN. Este módulo describe el ensayo de síntesis de ADN, en donde científicos fueron capaces de replicar el ADN en un tubo de ensayo. Avances en el entendimiento de las características y propiedades de la replicación de ADN son discutidos.

• NGSS

• HS-C6.1, HS-C6.2, HS-LS3.B1

Conceptos Clave

• Una vez que la estructura de la molécula de ADN fue descubierta, los científicos pudieron inmediatamente imaginar un posible mecanismo basado en las reglas del emparejamiento de bases de nucleótidos
• Para poder estudiar y observar la replicación del ADN mas directamente, los científicos en la década de 1950 elaboraron técnicas para llevar a cabo replicación de ADN en tubos, llamada ensayo de replicación de ADN.
• Al utilizar ensayos de síntesis de ADN, los científicos pudieron observar las características y propiedades de la replicación del ADN y probar varias hipótesis de cómo funciona el proceso.

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Did you know that blue eyes are the result of defective genes for pigment? Some recessive traits, like eye color, are harmless, while others are deadly. The way that genes translate into physical traits has to do with the particular enzyme that each type of gene makes, a discovery that was made by two scientists by way of the mutant bread mold they created, winning them the Nobel Prize in 1958.

Resumen

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.

• NGSS

• HS-C1.5, HS-LS1.A2, HS-LS3.A1, HS-LS3.B1

Conceptos Clave

• Genes cannot be used directly by organisms. The information stored in genes must be used to make products, such as enzymes, that cells need to perform different functions. Gene expression is the chemical pathway from genes to the gene products, such as proteins, that organisms can use.
• Since organisms have two genes for everything, even If one gene of a pair produces a defective enzyme or no enzyme at all, the other gene in the pair will make enough enzyme to do its job. Only an individual with two genes for a defective enzyme will actually show the recessive trait, such as an inherited disease or condition, blue eyes, or a recessive peapod shape.
• In the mid-1900s, George Beadle and Edward Tatum showed that a defective gene leads to a defective enzyme. Their “one gene, one enzyme” hypothesis was later expanded to “one gene, one RNA."
• The genetic code is the set of rules that combines amino acids to form polypeptides and is nearly the same for all life-forms on Earth.
• The genetic code is not a way for cells to translate genetic information in DNA directly into chains of amino acids to make proteins. Rather, RNA molecules must be made as intermediaries along the way from DNA to the polypeptides that fold into proteins.
• Genetic information moves in one direction, from DNA to RNA to protein. This is known as the Central Dogma of molecular biology.

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Did you know that DNA testing of 50,000-year-old bones showed that the original Neanderthal man did not descend from the same mother as modern humans? However, male lineage tests revealed that 8% of the non-African human gene pool consists of Neanderthal DNA. Certain genetic sequences called haplotypes are passed on only by males or by females, so to get a complete picture of the ancestry of a population, scientists generate one family tree based on the male line and another based on the female line.

Resumen

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).

Conceptos Clave

• Haplotypes are genetic sequences that we inherit from only one parent. There are two types: Y-chromosomes, inherited from your father, and mitochondrial DNA, inherited from your mother.
• Y-chromosome haplotypes are subject to random mutation and the discovery of numerous different haplotypes led scientists to construct the Y-chromosome family tree.
• Mitochondria are organelles in all eukaryotic cells and have some of their own DNA. All of your mitochondria come from your mother and help to build a mtDNA family tree.
• The most recent common ancestor (MRCA) is someone who exists in everyone's family tree.
• When scientists study populations of a given ethnic group, they generate one family tree based on the populations' Y-chromosomes and another one based on mtDNA.
• When constructing family trees, often an ancestor will appear in multiple places - this is a phenomenon known as pedigree collapse.

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Did you know that elephant seals in the Northern Pacific have a signature asymmetrical face that is extremely rare among other populations of elephant seals? This is because an evolutionary force called a bottleneck event acted upon their gene pool. Other forces can work to change the gene pool of a population, such as natural selection, gene flow, and the founder effect, among others.

Resumen

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.

Conceptos Clave

• Variants in genes are called alleles. Alleles can be dominant, meaning they are always expressed, or recessive, meaning that only individuals that receive defective copies from both parents are affected.
• The work of Gregor Mendel on genes and inherited traits was important in the development of early genetic theories of traits.
• In a population, the frequencies of alleles (the variations of genes), genotypes (the alleles an individual possesses), and phenotypes (the characteristics an individual expresses due to the alleles) will remain constant, or at equilibrium, unless acted upon by a force.
• The Hardy-Weinberg Equilibrium equation (p² + 2pq + q² = 1) describes how alleles behave in a given population, also known as a population’s gene pool.
• Genetic drift refers to changes in gene frequencies due to random events, which can happen very quickly, producing dramatic and sudden effects.
• There are two main types of genetic drift: bottleneck events (when a population suffers a sudden catastrophic decline and is repopulated by a small group of survivors) and Founder effects (when a new population is started by just a few members of the original population).

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Did you know scientists once believed that nonhuman animals lacked individuality in their behaviors? Today, we know that even fruit flies exhibit individual behaviors based on many factors, including genetic makeup and past experiences. But how did we gain this knowledge and come to this conclusion?

Resumen

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.

• NGSS

• HS-LS3.B2, HS-LS4.B1, HS-LS4.C2

Conceptos Clave

• Scientists study animal behavior through field observations in natural and evolutionary contexts (ethology) and controlled laboratory experimentation (comparative psychology).
• Other scientific disciplines, such as neurobiology, ecology, and physiology, also help tease out the proximate (immediate) to ultimate (long-term) causes of animal behavior.
• Through observation and experimentation across life stages, scientists distinguish innate (genetic) behaviors from learned behaviors and their interactions.
• Proximate causes include stimuli in an animal’s environment that triggers a behavioral response through the body’s systems, starting with the nervous system. In contrast, ultimate causes include natural selection for certain behaviors (adaptations) that improve animal survival, reproduction, or both.
• Evolutionary and behavioral studies show that most behaviors—such as feeding and migration—result from interactions between genetics and environment as well as both innate and learned responses.

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Resumen

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.

• NGSS

• HS-LS2.A1, HS-LS2.D1, HS-LS3.B2, MS-LS1.B1, MS-LS2.A1

Conceptos Clave

• Animal ecology is the study of the relationships between animals and their natural environment, including their specific ecological niche.
• An ecological niche is defined by the biotic (living things) and abiotic (nonliving things) factors, such as food, that must be present for an animal to meet its needs for survival and reproduction.
• An animal’s realized ecological niche may be smaller or larger than its fundamental (potential) niche, depending on its interactions with other species—or “symbiotic relationships.”
• Competition may reduce an animal’s realized niche, while facilitation or cooperation may effectively expand it.
• All animals are vulnerable to predation and have evolved various strategies to evade it, which drives adaptations such as camouflage and mimicry.
• As habitats continue to change from local and global alterations, animals encounter changing niches that may or may not support continued survival.

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Did you know that the sudden disappearance of a single species risks collapsing an entire ecosystem? In fact, the biological diversity (biodiversity) of our ecosystems is vital to the continued existence of life on Earth. Scientists recognize three levels of biodiversity: species diversity, genetic diversity, and ecosystem diversity. Each level impacts the others, and to understand their interactions, scientists are looking to a variety of ecosystems for answers.

Resumen

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.

• NGSS

• HS-LS2.A1, HS-LS3.B2, HS-LS4.B1, HS-LS4.C2, HS-LS4.C4, HS-LS4.D1, HS-LS4.D2

Conceptos Clave

• On the basis of physical characteristics, genetic markers, and interactions collected through multiple methods, scientists define biodiversity as the variety of life on Earth on multiple levels: species, genetic, ecosystem.
• Measurements of species-level biodiversity include species richness and evenness, which are calculated from samples of species distributions within and across ecosystems.
• Scientific studies of biodiversity find that it correlates with latitude, landscape heterogeneity, and specific biogeographical pattern features like islands.
• The functioning of Earth’s systems that sustain life depends on biodiversity at all levels, evidenced by the poor health of ecosystems with low biodiversity.

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Did you know the Earth’s ecosystems rely on the species that inhabit them for their sustained health? It’s a bit like the relationship between a bicycle and its individual parts. Certain pieces of the bicycle can be removed without great effect. However, removing more critical components, like the bicycle's brakes, can result in dire consequences. So, what happens when a crucial species is removed from its ecosystem?

Resumen

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.

• NGSS

• HS-LS2.C1, HS-LS2.C2, HS-LS4.C5, HS-LS4.D2

Conceptos Clave

• All animals alter their habitats to some degree, but humans are especially adept at changing ecosystems to meet their needs.
• Global assessments have revealed that human changes to the environment impact biodiversity at all geographic scales.
• Geographic fragmentation and introduced species alter ecosystems and usually reduce biodiversity.
• Managing biodiversity requires extensive international stewardship and cooperation, given our globally interconnected world.

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Did you know that ecosystems naturally provide an array of life-sustaining services to humans? For example, earth’s ecosystems filter and regulate both the water we drink and the air we breath, ensuring many of our essential needs are met. But what is the cost of these services? Nothing in life is free.

Resumen

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.

• NGSS

• HS-ESS3.A2, HS-ETS1.B1, HS-LS2.C1, HS-LS4.D2

Conceptos Clave

• Ecosystems have long been recognized for their roles in naturally generating harvestable provisions, whether honey, timber, soils, or others.
• Studies have found that ecosystems also supply a myriad of essential services, such as water filtration and climate regulation.
• A full consideration of ecosystem services includes provisions (products), regulation of processes, support of biodiversity, and satisfaction of cultural needs.
• Ascribing monetary value to ecosystem services positions them more effectively in the cost-benefit evaluations that guide decision-making about land use.

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¿Sabía usted que?

All monarch butterflies are one species. But did you know that monarch butterflies in North America exist in two separate populations? These two populations can interbreed but generally will not. So, what exactly is a “population,” and why is understanding the distinction crucial to species’ survival on Earth? Let’s find out!

Resumen

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.

• NGSS

• HS-LS2.A1, HS-LS2.C1, HS-LS2.D1, HS-LS3.B2, HS-LS4.C3, MS-LS2.A1

Conceptos Clave

• In biology, populations are defined as groups of the same species in the same geographic area that have the potential to breed.
• The field of population biology emerged as the need to manage fish and other food resources became important to societies that rely on them.
• Mathematical approaches to understanding animal population dynamics were inspired by studies of human population dynamics and include demographic statistics such as age and sex distributions.
• The recognition that populations don’t grow exponentially led to the concept of carrying capacity and its determinants for a particular species.
• While models show general patterns, populations are subject to unpredictable variables that limit growth or cause declines such as climate change and pressure from predators or harvest.

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