This 14-minute video lesson looks at secondary active transport in the Nephron. [Biology playlist: Lesson 60 of 71].

This 14-minute video lesson covers the chromosomal basis for gender and sex-linked traits. [Biology playlist: Lesson 17 of 71].

This 14-minute video lesson looks at how a sodium potassium pump can maintain a voltage gradient across a cell or neuron's membrane. [Biology playlist: Lesson 42 of 71].

This 9-minute video lesson discusses what a species is and isn't. It considers ligers, tiglons, mule, hinnies, and dogs. [Biology playlist: Lesson 61 of 71].

This 13-minute video lesson looks at the science of taxonomy and where humans fit into the tree of life. [Biology playlist: Lesson 62 of 71].

This 19-minute video lesson provides an overview of how the nephrons in the kidney filter blood and reabsorb water and other molecules. [Biology playlist: Lesson 59 of 71].

This 21-minute video lesson looks at the pulmonary system including the lungs, larynx, trachea, bronchi, bronchioles, alveoli and thoracic diaphragm. [Biology playlist: Lesson 37 of 71].

This 9-minute video lesson looks at tropomyosin and troponin and their role in regulating muscle contraction. How calcium ion concentration dictates whether a muscle is contracting or not. [Biology playlist: Lesson 48 of 71].

This 8-minute video lesson presents an overview of types of immune responses. It looks at the difference between innate and adaptive immunity and the differences between humoral adaptive immunity and cell-mediated adaptive immunity. [Biology playlist: Lesson 52 of 71].

This 20-minute video lesson discusses how variation can be introduced into a species. [Biology playlist: Lesson 7 of 71].

This 23-minute video provides an introduction to viruses. [Biology playlist: Lesson 19 of 71].

This art history video discussion examines the Ambulatory at the Basilica of Saint Denis, Paris, 1140-44.

Describe a bivariate relationship's linearity, strength, and direction. In other words, plotting things that take two variables into consideration and trying to see whether there's a pattern with how they relate.

This art history video discussion looks at Arnold Bocklin's "Self-Portrait with Death Playing the Fiddle", 1872, oil on canvas, 75 x 61 cm (Alte Nationalgalerie, Berlin).

This art history video discussion looks at Bodhisattva, probably Avalokiteshvara (Guanyin), Northern Qi dynasty, c. 550--60, Shanxi Province, China, sandstone with pigments, 13-3/4 feet / 419.1 cm high (Metropolitan Museum of Art, New York).

This art history video discussion looks at Rosa Bonheur's "Plowing in the Nivernais (or The First Dressing)", oil on canvas, 1849 (Musee d'Orsay, Paris).

This art history video discussion looks at Rosa Bonheur "Sheep in the Highlands", 1857, oil on canvas (Wallace Collection, London). The Wallace Collection suggests that this painting is likely the result of a trip that the artist made to Scotland the previous year.

This art history video discussion examines Hieronymus Bosch's "Last Judgment Triptych", 1504-08, Akademie fur bildenden Kunste, Vienna, overall dimensions.

This art history video discussion looks at Botticelli's "The Birth of Venus", 1483-85, tempera on panel, 68 x 109 5/8" (172.5 x 278.5 cm), Uffizi, Florence.

This art history video discussion looks at Botticelli's "La Primavera (Spring)", 1481-1482, tempera on panel, 80 x 123 1/2" (203 x 314), Uffizi, Florence.