This video segment from NOVA: A Desert Place describes the physical characteristics and organisms that define the desert biome.

This video segment from Outdoor Nevada examines threats to the desert tortoise population.

This video from Nature offers a description of desirable traits in beef and dairy cattle.

In this video segment from Nature, scientists question how animals mysteriously survive natural disasters.

In this deterministic cellular automata model, interactions between neighboring automata are described using a prisoner's dilemma. Limiting dispersal of seeds of annual plants can permit heterogeneous co-existence, whereas thorough mixing instead allows one subpopulation to dominate quickly.

This reference tool allows students to identify an arthropod's order by making a series of guided decisions, such as six legs or more, well-developed or missing wing, and chewing or sucking mouthparts. The key, which includes only adult arthropods, is available as an interactive key on the AMNH's Web site that can be downloaded to your computer.

In this video segment from Nature, learn about six different breeds of cattle.

In the first video, we present a biological circuit topology from Ma, Trusina, El-Samad, Lim, and Tang, "Defining network topologies that can achieve biochemical adaptation," Cell, 138: 760-773 (2009). This topology supports adaptation, which is not the absence of change in response to stimulation/stress, but, instead, the ability to produce delayed compensation for those changes. In the second video, we summarize the method of almost linear stability analysis used to solve for the dynamics of this example system.

To describe how oscillations are supported in systems of differential equations, we present a classic "Romeo and Juliet" picture of two-dimensional oscillations, and we analyze how trajectories change as nullclines are arranged at different angles in the phase plane. In addition to models based on traditional systems of differential equations, dynamical systems with time delays and dynamical systems with stochastic fluctuation (i.e. stochastic resonance) can also support oscillations.

The first video segment presents a canonical mathematical example from quantitative biology, in which mRNA is transcribed from a gene sequence, and protein is translated from mRNA. The second segment uses eigenvector-eigenvalue analysis to sketch the trajectories of the system in a phase portrait. Finally, the third segment generalizes the linear stability analysis used to study this example.

Movement of ions in and out of cells is crucial to maintaining homeostasis within the body and ensuring that biological functions run properly. The natural movement of molecules due to collisions is called diffusion. Several factors affect diffusion rate: concentration, surface area, and molecular pumps. This activity demonstrates diffusion, osmosis, and active transport through 12 interactive models.

This minds-on analysis and discussion activity helps students understand that cell size is limited by the very slow rate of diffusion over any substantial distance and the insufficient surface-area-to-volume ratio for larger cells. In addition, students calculate why these problems do not apply to long slender cells or parts of cells (e.g. the axons of neurons that extend from your spinal cord to your foot). To maximize student participation and learning, I recommend that you have your students complete the questions individually or in pairs and then have a whole class discussion.

In this classroom activity, middle school students explore the Greek and Latin root words used to create dinosaur names. The activity opens with background information for teachers about how dinosaurs are named. As a class, students explore the Greek and Latin roots of the words photograph, terrace and other familiar terms. Working individually, students complete a worksheet that challenges them to translate the meaning of seven dinosaurs' names. Then, working in pairs, students create their own dinosaur; name it; and describe how it moves, what it eats, how it raises it young, and how it behaves.

This activity sheet for young children is designed to be completed during a visit to the Museum's Hall of Biodiversity. The printable two-page handout includes an explanation of biodiversity, a "scavenger hunt" and a writing and drawing activity using the Forest Floor Diorama, a classification activity using the Spectrum of Life Wall and a treasure hunt using the Rain Forest Diorama.

Oyster Shells is one of the AMNH Education Department's many collections of specimens and artifacts gathered the world over by explorers and scientists. In its online Discovery Collection form, Oyster Shells includes photographs of 15 specimens with classification and distribution details, an interactive key that guides you through specimen identification, an activity where students select and identify a specimen photograph using the interactive identification key and an Educator's Guide with suggestions for how to use the Oyster Shells Discovery Collection in the classroom.

This video segment adapted from A Science Odyssey tells the story of researcher Sir Alexander Fleming, whose luck and scientific reasoning led to the groundbreaking discovery of penicillin.

In this video segment from NatureScene, observe some methods of plant identification with regards to the diversity of hardwoods at the Congaree Swamp.

This video segment from the Science and Technology Chat series focuses on dolphin pregnancy, birth, and care of the young, and features Atlantic bottlenose dolphins living in captivity at the Mirage Resort Dolphin Habitat.

Dr. Stephen O'Brien of the National Cancer Institute discovers a 700-year-old mutation that makes a person resistant to HIV infection. From Evolution: "Evolutionary Arms Race."

Students learn the principles of independent assortment and gene linkage in activities which analyze inheritance of multiple genes on the same or different chromosomes in hypothetical dragons. Students learn how these principles derive from the behavior of chromosomes during meiosis and fertilization.