Paul Andersen explains how an object with mass placed in a gravitational field experiences a gravitational force. On the Earth this gravitational force is known as weight. The gravitational force is equal to the product of the mass and the gravitational field strength.

Paul Andersen explains how gravitational forces differ from the other three fundamental forces; electromagnetic, strong, and weak. Gravitational forces are always attractive and operate at all scales. Even though gravitational forces are relatively small they dominate at the large scale.

Paul Andersen explains how the gravitational mass is a measure of the force on an object in a gravitational field. The gravitational mass is based on the amount of material in an object and can be measured to a standard kg using a balance.

In this video Paul Andersen explains how the greenhouse effect and greenhouse gases keep our planet warm enough to be habitable. He explains how greenhouse gases keep heat closer to the surface. He finally shows how increases in greenhouse gases may lead to dangerous global warming.

Paul Andersen explains how a radioactive nuclei can decay by releasing an alpha, beta, or gamma particle. The exact moment of decay for each nuclei can not be determined but probability is useful in predicting the half-life.

In this video Paul Andersen explains the elements in the Hardy-Weinberg equation; including the allele frequency and phenotype frequency. He begins with a brief explanation of phenotypes and genotypes. A sample problem is worked out and another problem is included.

Paul Andersen explains how you can combine the power of a Punnett square for an entire gene pool.  Hardy-Weinberg equilibrium will remains constant under several constrains and the probability square makes the information more understandable.

Paul Andersen explains how the wavelength of a standing wave is determined by the boundary length and frequency of the wave. The fundamental frequency has a wavelength double the boundary length. Harmonics are built on the fundamental frequency.

Paul Andersen explains how chemicals can cause both chronic and acute diseases. A discussion of the five main types of toxins; neurotoxins, carcinogens, teratogens, endocrine disruptors, and allergens is including.  The LD50 method of determining toxicity as well as a discussion of bioaccumulation and biomagnification is is included.

Paul Andersen explains how heat is the movement of energy from an object with a higher temperature to an object with lower temperature. Heat transfer can occur through conduction, convection, and radiation.

In this video Paul Andersen explains how energy can be transferred from warmer objects to colder objects through heat. Temperature is a measure of the average kinetic energy of the particles in a substance. When two objects are in contact collisions between the particles will transfer energy from the warmer object in the form of heat.

Paul Andersen explains how heating is the transfer of energy (heat) from a warmer object to a cooler object. Heat can be transferred through conduction, convection and radiation. At the microscopic level conduction results from the collision of particles and therefore the transfer of kinetic energy.

Paul Andersen explains how biology is ordered in the hierarchy of life. He first of all describes how emergent properties appear as you move to more inclusive systems. The then describes life at the following levels; atom, molecule, macromolecule, organelle, cell, tissue, organ, organ system, organisms, population, community, ecosystem, biome and finally biosphere.

Paul Andersen explains how hugs between tissues can help maintain homeostasis. Countercurrent heat exchange allows heat to stay within the core of the body. Close contacts between the capillaries and alveoli allow our body to maintain the correct concentration of oxygen. Capillaries also hug the tubules in the nephron to maintain osmolarity and filter the blood.

Paul Andersen reviews the major components of the homeostasis. He explains how organisms respond to abiotic and biotic factors in their environment with feedback loops. He shows how responses can be behavioral or physiological.

Paul Andersen explains how disruptions in homeostasis can affect biological systems at all levels. He uses the example of dehydration in animals to explain how disruptions at the cellular level can affect an organism.

Paul Andersen shows how homeostasis reflects of evolution through time. The endocrine system shows continuity through flatworms, earthworms and vertebrates. However the respiratory system shows change as organisms move onto land. The importance of the Tiktaalik fossil as a transitional fossil is emphasized.

Paul Andersen describes four important homeostatic loops in biology. He begins with a brief description of the elements of a homeostatic loop. He then describes how the hypothalamus helps us maintain a stable internal body temperature. He explains the role of the pancreas (insulin and glucagon) in regulating blood glucose.

Paul Andersen explores population dynamics of the human population. The population has show exponential growth since the industrial revolution and all countries will eventually move through the demographic transition.