Paul Andersen explains how feedback loops allow living organisms to maintain homeostasis. He uses thermoregulation in mammals to explain how a negative feedback loop functions. He uses fruit ripening to explain how a positive feedback loop functions. He also explains what can happen when a feedback look is altered. Diabetes mellitus is caused by an alteration in the blood glucose feedback loop.
Paul Andersen explains how eukaryotic cells use compartmentalization to increase the surface area and level of specialization within the cell. Prokaryotic and eukaryotic cells are compared and contrasted. The role of both the mitochodria and endoplasmic reticulum are discussed.
Paul Andersen describes how cells move materials across the cell membrane. All movement can be classified as passive or active. Passive transport, like diffusion, requires no energy as particles move along their gradient. Active transport requires additional energy as particles move against their gradient. Specific examples, like GLUT and the Na/K pump are included.
Paul Andersen explains how cells are selectively permeable with the help of their cell membrane. The main constituents of the cell membrane, including cholesterol, glycolipids, glycoproteins, phospholipids, and proteins are included. The fluid mosaic model is also illustrated. The cell wall in plants, bacteria, and fungi is also discussed.
Paul Andersen explains how living organisms exchange matter with the environment. The importance of the surface area to volume ratio is emphasized using a simple mathematical model. The essential chemicals for life; water, carbon, nitrogen and phosphorus are described. Each of these elements are vital to the four major macromolecules. A brief description of the biogeochemical cycles is also included.
Paul Andersen details the processes of photosynthesis and respiration in this video on free energy capture and storage. Autotrophs use the light reactions and the Calvin cycle to convert energy from the Sun into sugars. Autotrophs and heterotrophs use cellular respiration to convert this sugar into ATP. Both chemosynthesis and fermentation are discussed. The evolution of photosynthesis is also discussed.
Paul Andersen describes how free energy is used by organisms to grow, maintain order, and reproduce. A brief discussion of the first and second law of thermodynamics is also included. Disruptions in the amount of free energy can cause death and disruptions to popultaions, communities, and ecosystems.
Paul Andersen attempts to explain Gibbs Free Energy. He begins by using three spontaneous reactions to explain how a change in enthalpy, entropy and temperature can affect the free energy of a system. He then applies this concept to cellular respiration and photosynthesis.
Paul Andersen discusses scientific evidence of the origin of life on our planet. He begins with a brief discussion of the age of the earth and ends with the future of humanity. He includes geologic, chemical and molecular data.
Paul Andersen describes how life could have formed on our planet through natural processes. The progression from monomers, to polymers, to protocells and finally to cells is described. The Miller-Urey experiment is described in detail as well as characteristics of the latest universal ancestor.
Paul Andersen explains how life has evolved and continues to evolve today. A brief discussion of artificial, natural and sexual selection is included. The beak of the finch is used to explain how directional selection is achieved.
Paul Andersen explains how reproductive isolation can eventually lead to speciation. Three main barriers to gene flow are included: geographic, pre-zygotic and post-zygotic. Both allopatric and sympatric speciation are discussed. A brief discussing of polyploidy and punctuated equilibrium are also included.
Paul Andersen details the evolutionary processes of speciation and extinction. Stickleback evolution in Lake Loberg is used as example of rapid speciation. Adaptive radiation is illustrated using the Hawaiian honeycreeper. A brief discussion of extinctions and mass extinctions is also included.
Paul Andersen discusses the specifics of phylogenetics. The evolutionary relationships of organisms are discovered through both morphological and molecular data. A specific type of phylogenetic tree, the cladogram, is also covered.
Paul Andersen describes three main characteristics of life that are conserved in all organisms on the planet. The universal genetic code, the central dogma of biology, and shared metabolic pathways give us details of the original universal ancestor. He also explains how eukaryotic cells gained complexity through infolding of the cell membrane and endosymbiosis.
Paul Andersen lists major evidence for the existence of evolution. He begins with a discussion of Charles Darwin and the evidence that he presented in the Origin of Species, including biogeography, fossils, and homologies. He also explains how DNA evidence can be used to trace evolutionary history.
Paul Andersen describes genetic drift as a mechanism for evolutionary change. A population genetics simulator is used to show the importance of large population size in neutralizing random change. The near extinction of the northern elephant is used as an example of the bottleneck effect. The high incidence of total colorblindness due to a typhoon that hit the small island of Pingelap is also included.
Paul Andersen details examples of natural selection in the world. He starts by explaining how changes in global temperatures are causing plants to adapt. He explains how mutations cause changes in phenotype which give organisms varying levels of fitness. Two specific examples of natural selection; sickle cell disease and muti-drug resistant tuberculosis are also included.
Paul Andersen explains how natural selection is a major mechanism in evolution. The video begins with a discussion of Charles Darwin and the details of natural selection. The data of the peppered moth during the industrial revolution is used to show the process of adaptation. Allele frequencies are calculated before and after the selection. The adaptation of cichlids in African lakes is also included.
Mr. Andersen describes visible light while discussing the electromagnetic spectrum. A simple description of the eye, optical illusions and lights are also included.
