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...

Paul Andersen explains how viruses reproduce using the lytic cycle. He also shows how viruses can pick up new genetic material and how retroviruses (like HIV) can enter into the lytic cycle. He also describes the lysogenic cycle and...

Paul Andersen explains how populations interact in an ecosystem. The symbiosis of several populations is based on effects that may be neutral, positive, or negative. Interactions like mutualism, commensalism and parasitism are...

Explore the steps of DNA replication, the enzymes involved, and the difference between the leading and lagging strand! This video is an update from our old DNA replication video with nearly the same script but added detail and improved...

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...

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. ...

Join the Amoeba Sisters on this introduction to the Nervous System! This video briefly describes the division of the central nervous system (including going over some general areas of the brain) and the peripheral nervous system before...

Join the Amoeba Sisters a they explore different muscle tissues and then focus on the sliding filament theory in skeletal muscle! This video also briefly talks about muscle naming, some vocabulary (such as agonists and antagonists)...

Paul Andersen shows you how we can use a spreadsheet to model population changes. He begins with a brief discussion of populations and life cycles. He then shows you how you can model a single generation using a spreadsheet.

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...

Paul Andersen explains how organisms respond to the external environment. He begins with a discussion of behavioral responses like hibernation and migration. He ends with a discussion of physiological responses like shivering and...

Paul Andersen describes microevolution and macroevolution in the stickleback fish of Loberg Lake. He describes how anadramous fish repopulated the lake after poisoning and adapted to the new environment through natural selection. He...

Paul Andersen starts this video with a description of the respiratory surface. He explains how worms, insects, fish and mammals take in oxygen and release carbon dioxide. He then tours the major organs of the respiratory system; from...

In this video Paul Andersen explains the major phases of meiosis including: interphase, prophase I, metaphase I, anaphase I, telophase I, cytokinesis, interphase II, metaphase II, anaphase II, and telophase II. He explains how variation...

Paul Andersen explains how populations experience exponential. He begins by address the major players; N (population size) and r (growth rate). He models population growth in rabbits through four generations. He then shows you how to...

Curious about modes of nutrition? Join the Amoeba Sisters in learning about autotrophs and heterotrophs. Video explains these terms as well as how their carbon source differs. Photoautotrophs, photoheterotrophs, chemoautotrophs, and...

Paul Andersen explains how we perceive our environment using our sensory system. He starts with a brief discussion of action potentials and the nervous system. He shows that we many more than five senses. He goes into more detail to show...

Paul Andersen shows you how to construct a cladogram from a group of organisms using shared characteristics. He also discusses the process of parsimony in cladogram construction. He then explains how modern cladograms are constructed...

Paul Andersen explains how signal transmission is used to alter both cellular function and gene expression. He uses the example of epinephrine release in humans and how it is used in the fight or flight response. Epinephrine causes...

Join the Amoeba Sisters in their updated plant structure and adaptations video as they discuss the terms vascular vs nonvascular and how they relate to plants before exploring some general categories of plants (bryophytes, seedless...

Paul Andersen explains how signal transduction pathways are used by cells to convert chemical messages to cellular action. Epinephrine is used as a sample messenger to trigger the release of glucose from cells in the liver. The...

Paul Andersen starts with a brief description of diffusion and osmosis. He then describes the diffusion demonstration and how molecules move over time. He then explains the concepts behind the osmosis lab and how potatoes are affected...

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. He also uses the...

Paul Andersen describes the important characteristics of viruses. He starts with a brief description of origin theories. He then describes the two characteristics of all viruses; genetic information and protein coats. He also...