The video resource "Pollution: Crash Course Ecology #11" is included in the "Ecology" course from the resources series of "Crash Course". Crash Course is a educational video series from John and Hank Green.

This "The Polymerase Chain Reaction (PCR)" learning object is the from the Sumanas resource series. Sumanas offers a robust selection of content and services that are directed at enhancing the learning experience.

Paul Andersen explains how polymers are formed from monomers. He describes how carbohydrates, proteins and nucleic acids are created through condensation reactions. He also explains how these macromolecules are broken down through the process of hydrolysis.

This "Polyribosomes" learning object is the from the Sumanas resource series. Sumanas offers a robust selection of content and services that are directed at enhancing the learning experience.

This "Polyribosomes" learning object is the from the Sumanas resource series. Sumanas offers a robust selection of content and services that are directed at enhancing the learning experience.

This video is from the Khan Academy subject of Partner content on the topic of Crash Course and it covers Population Ecology: The Texas Mosquito Mystery.

The video resource "Population Ecology: The Texas Mosquito Mystery - Crash Course Ecology #2" is included in the "Ecology" course from the resources series of "Crash Course". Crash Course is a educational video series from John and Hank Green.

Hank talks about population genetics, which helps to explain the evolution of populations over time by combing the principles of Mendel and Darwin, and by means of the Hardy-Weinberg equation.

The video resource "Population Genetics: When Darwin Met Mendel - Crash Course Biology #18" is included in the "Biology" course from the resources series of "Crash Course". Crash Course is a educational video series from John and Hank Green.

Using Avida-ED freeware, students control a few factors in an environment populated with digital organisms, and then compare how changing these factors affects population growth. They experiment by altering the environment size (similar to what is called carrying capacity, the maximum population size that an environment can normally sustain), the initial organism gestation rate, and the availability of resources. How systems function often depends on many different factors. By altering these factors one at a time, and observing the results, students are able to clearly see the effect of each one.

This lesson is the second of two that explore cellular respiration and population growth in yeasts. In the first lesson, students set up a simple way to indirectly observe and quantify the amount of respiration occurring in yeast-molasses cultures. Based on questions that arose during the first lesson and its associated activity, in this lesson students work in small groups to design experiments that will determine how environmental factors affect yeast population growth.

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 explains the importance of genetic variation within a population. He begins with a discussion of the devil facial tumor that is a form of cancer transferred between Tasmanian devils. He then explains how a decrease in genetic variability nearly led to the extinction of the black-footed ferret.

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 included. Human impacts to ecosystems are also considered using the invasive species kudzu.

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 loop is altered.

This "Positron Emission Tomography (PET)" learning object is the from the Sumanas resource series. Sumanas offers a robust selection of content and services that are directed at enhancing the learning experience.

This "Potential Use of Human Embryonic Stem Cells to Treat Disease (alternate version)" learning object is the from the Sumanas resource series. Sumanas offers a robust selection of content and services that are directed at enhancing the learning experience.

Find out how the body controls how much blood flows through a capillary bed. Rishi is a pediatric infectious disease physician and works at Khan Academy.

For irrigated crops, knowing when and how much water to apply has long been a matter of experience and guesswork. In a changing climate, new technology can reduce this uncertainty, enabling farmers to make every drop of water count.