Why do teenagers act the way they do? This video segment from FRONTLINE: Inside the Teenage Brain explores the work scientists are doing to explain some of the mysteries of teenage behavior.

In this activity, student teams design and conduct a scientific investigation in which they explore the conditions necessary for life. They conduct observations of environmental conditions both indoor and outdoor, and determine the range of variation they see. They compare these data with published temperature data for Earth, Mars, Pluto and Venus. The activity supports inquiry into the real world challenge of searching for life in extreme environments. The resource includes several student data sheets, data table and images, and a teacher's guide. Materials needed for this activity include weather instruments (e.g., thermometers, barometers, anemometers). This is Activity A of two activities in the first module, titled "Temperature variations and habitability," of the resource, "Earth Climate Course: What Determines a Planet's Climate?" The course aims to help students to develop an understanding of our environment as a system of human and natural processes that result in changes that occur over various space and time scales.

In this activity, student teams create a knowledge map of the essential characteristics or factors of a planet with a habitable climate, identifying range of inputs, outputs and variables of a planetary environmental system. Identified characteristics are compared to extreme environments on Earth, such as the Antarctic or the Sahara desert, and are used to consider the real life challenge of searching for life in extreme environments. The resource includes a student data sheet, questions, teacher's guide and scoring rubric. This is Activity B of two activities in the first module, titled "Temperature variations and habitability," of the resource, Earth Climate Course: What Determines a Planet's Climate? The course aims to help students to develop an understanding of our environment as a system of human and natural processes that result in changes that occur over various space and time scales.

This illustration from Evolution by Monroe W. Strickberger shows the remarkable similarities between the bones in the forelimbs of various tetrapods, all of whose limbs serve very different functions.

Examine how the human/grizzly relationship has changed since the closing of the Yellowstone dumps, and also learn about the challenges posed to both humans and bears, in this video segment from Nature.

In this activity, learners overlap the three primary colors to see how all other colors are made. This activity also explains how color can be explained by the subtraction of colors of light, related to the principles of absorption and reflection of light.

In this video from an expedition to the Bahamas, Jonathan encounters dozens of Lemon sharks while trying to film a Tiger shark. But finally a Tiger shark arrives and you won‰ŰŞt believe the incredible encounter Jonathan has with this enormous, hungry animal. Please see the accompanying study guide for educational objectives and discussion points.

In this lesson designed to enhance literacy skills, students learn that transitional fossils provide scientists with evidence to establish how major animal groups are related to one another.

This animation produced by WGBH and Digizyme, Inc. demonstrates the experimental technique used to introduce DNA plasmids inside bacterial cells, a process called bacterial transformation.

John Noble Wilford, a New York Times science writer, outlines various hypotheses on the origin of bipedalism.

In this video segment from NOVA: Judgment Day: Intelligent Design on Trial, learn about the discovery of a well-preserved transitional fossil and how such transitional fossils support the theory of evolution.

This fun Web site is part of OLogy, where kids can collect virtual trading cards and create projects with them. Here, they explore the Tree of Life cladogram. The site begins with a brief explanation of cladograms and how the Tree of Life shows the relationship of all living things on Earth. A cladogram of fruit is used to demonstrate on a small scale how scientists use this tool to understand how things are similar and different. A portion of the Tree of Life cladogram is included, showing true bacteria, arthropods, mammals, and 11 other important groups of species. Students can mouse over the branching points to see what the subsets have in common. The site also includes a pie chart view that compares the relative size of the most important groups of species. Students can click on each group to learn its characteristics, known species, size range, and other important details.

All cells, organs and tissues of a living organism are built of molecules. Some of them are small, made from only a few atoms. There is, however, a special class of molecules that make up and play critical roles in living cells. These molecules can consist of many thousands to millions of atoms. They are referred to as macromolecules (or large biomolecules).

Millions of fish eggs from the Caribbean get stuck in the gulf stream every year and drift thousands of miles north where they hatch. Unfortunately, when winter comes, the baby fish will die. In this video, Jonathan joins the New England Aquarium Dive Club on a tropical fish rescue in Rhode Island where they catch some of these fish in the fall before water temperatures plummet. The fish go to the New England Aquarium‰ŰŞs exhibits. Please see the accompanying study guide for educational objectives and discussion points.

In this problem-based learning activity, students will examine opposing views on the Amazon Rainforest and will take a position on land-use and species conservation in one of the last areas of biodiversity on Earth. This activity is part of Exploring the Environment.

This illustrated guide is designed to help students recognize and learn the different types of antennae found on arthropods. The single Web page, which can be easily printed for use at field sites or in the lab, shows plumose (featherlike) pectinate (comblike) serrate (sawlike) moniliform (beadlike) filiform (threadlike) aristrate (with bristles) elbowed (with a bend) clubbed (the segments towards the end are larger).

This illustrated guide is designed to help students recognize and learn the different types of compound leaves. The single Web page can be easily printed for use at field sites. Along with a short description, an illustration that identifies a leaflet and petiole is included for each type: pinnate (odd) twice pinnate pinnate (even) palmate.

In the first video segment, we estimate properties of a parent distribution (i.e. mean and standard deviation) from a sample of a finite collection of data measurements, and we describe the standard error (SE). In the second segment, we derive the famous square-root of n factor that appears in the SE formula. The third video segment describes the visual comparison of error bars, and the fourth segment warns against a mistake that can generate inappropriate claims of statistical significance during this kind of analysis.

In this classroom activity, middle school students explore cladistics by creating a cladogram. The activity opens with background information for teachers about cladistics. After discussing the relationship of some familiar mammals, students learn about how scientists use cladistics to determine evolutionary relationships among animals. Working in pairs, students complete a worksheet that directs them to examine coins and create a cladogram based on their shared characteristics. Then, small groups of students examine dinosaur illustrations, identify their shared features, and those features to classify the dinosaurs.