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Biology Basics: Ecosystems

Life thrives in every environment on Earth, and each of those environments is its own ecosystem, essentially a little machine made up of living and nonliving parts that interact with one another in a particular [more…]

Biology Basics: Population Ecology

Population ecology is the branch of biology that studies the structures of populations and how they change. The unique thing about population ecologists is that they study the relationships within ecosystems [more…]

Biology: How to Track Changes in Populations

Population dynamics are changes in population density over time or in a particular area. Primarily, populations increase because of births (natality) and decrease because of deaths [more…]

Biology Basics: Interaction among Species

Not all the organisms in a given biological community are the same. In fact, they’re often members of different species (organisms that can’t sexually reproduce together and produce fertile offspring). [more…]

Biology Basics: Matter Cycling within Ecosystems

Organisms in biological ecosystems connect to one another through their need for matter as well as energy. Every organism needs molecules like proteins, carbohydrates, and fats to provide the raw building [more…]

How Biologists Read a Gene with DNA Sequencing

DNA sequencing, which determines the order of nucleotides in a DNA strand, allows scientists to read the genetic code so they can study the normal versions of genes. It also allows them to make comparisons [more…]

How Biologists Separate Molecules with Gel Electrophoresis

Scientists use gel electrophoresis to separate molecules based on their size and electrical charge. Gel electrophoresis can separate fragments of DNA that were cut with restriction enzymes, creating a [more…]

Biology Experiments and the TimeLapse Pro iPad App

Teachers can easily incorporate iPads into their biology science classrooms to research and record experiments. This activity uses iPads and the TimeLapse Pro app to measure the growth of mung beans over [more…]

Glands and Hormones

In addition to the nervous system’s electrical signals, animals also regulate their bodies with chemical messengers called hormones. Endocrine glands produce the hormones and then release them into the [more…]

Adaptive Immunity

Your adaptive immunity gets its name because it adapts and changes, or adapts, as you go through life and are exposed to specific microbes that your innate defenses can’t fight. Your body’s innate defenses [more…]

Biology Basics: Pulmonary Circulation

Pulmonary circulation, the first pathway of your two-circuit circulatory system, brings blood to your lungs for oxygenation. Following is a rundown of how blood moves during pulmonary circulation. [more…]

Biology Basics: Systemic Circulation

Systemic circulation brings oxygenated blood around to all your body’s cells. Here is a description of how blood moves through this pathway (see the figure): [more…]

Biology Topics to Study for the Miller Analogies Test (MAT)

Science and math aren't the most prevalent topics on the MAT, but they are tested. The biology topics listed here will help you prepare for the MAT by exposing you to the major subjects in the biology [more…]

The Bootstrap Method for Standard Errors and Confidence Intervals

You can calculate the standard error (SE) and confidence interval (CI) of the more common sample statistics (means, proportions, event counts and rates, and regression coefficients). But an SE and CI exist [more…]

Two Views of Probability

Two quite different ideas about probability have coexisted for more than a century. These probability approaches, which differ in several important ways, are as follows: [more…]

Trying the Simulation Approach in Statistical Analysis

Modern statistical software makes it easy for you to analyze your data in most of the situations that you’re likely to encounter (summarize and graph your data, calculate confidence intervals, run common [more…]

Model Building with Stepwise Regression

One of the reasons (but not the only reason) for running a multiple regression analysis is to come up with a prediction formula for some outcome variable, based on a set of available predictor variables [more…]

10 Names Every Biostatistician Should Know

Biostatistics, in its present form, is the cumulative result of four centuries of contributions from many mathematicians and scientists. Some are well known, and some are obscure; some are famous people [more…]

Estimating Sample-Size Requirements with a Handy Calculator

While many programs, apps, and web pages are available to perform power and sample-size calculations, they aren’t always easy or intuitive to use. Because spreadsheets like Excel are readily available [more…]

Estimating Sample Size for Correlation Tests in Biostatistics

For a correlation test in biostatistics (such as the Pearson or Spearman test), pick the scatter chart that looks like an important amount of correlation. Each chart shows the value of [more…]

Sample Size Estimation for Unpaired Student t Tests in Biostatistics

In biostatistics, when comparing the means of two independent groups of subjects using an unpaired Student t test, the effect size is expressed as the ratio of Δ [more…]

Sample Size Estimation for Paired Student t Tests in Biostatistics

In biostatistics, when comparing paired measurements (such as changes between two time points for the same subject) using a paired Student t test, the [more…]

Estimating Sample Size When Comparing Two Proportions in Biostatistics

The proportion of subjects having some attribute (such as responding to treatment) can be compared between two groups of subjects by creating a cross-tab from the data, where the two rows represent the [more…]

Biostatistics For Dummies Cheat Sheet

To estimate sample size in biostatistics, you must state the effect size of importance, or the effect size worth knowing about. If the true effect size is less than the “important” size, you don’t care [more…]

How Can Paralysis Be Cured?

Paralysis has multiple causes. The part of the brain that controls movement can be damaged, such as from a stroke. Injuries and diseases can interrupt the message transmitted from the brain to the muscles [more…]

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