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This page shows some key events of human development during the embryonic period of the first eight weeks (weeks 1 - 8) following fertilization. This period is also considered the organogenic period, when most organs within the embryo have begun to form. There are links to more detailed descriptions which can be viewed in a week by week format, by the Carnegie stages or integrated into a Timeline of human development. Online resources available include: individual images of all Carnegie stages, scanning electron micrographs of the earlier stages, cross-sections showing internal structures at mid- and late-embryonic, 3D reconstructions of internal structures, animations of processes, ultrasound scans and information about abnormalites of development.

Whether gas, liquid or solid; radioactive or stable; reactive or inert; toxic or in your vitamin pill, the 118 building blocks each has its own chemically idiosyncratic characteristics--and certain commonalities. See what makes your favorite element unique on this interactive periodic table

To understand the importance of elements to nutrition. Of the approximately 115 elements known, only the 19 highlighted in purple in Figure 1.26 are absolutely required in the human diet. These elements-called essential elements-are restricted to the first four rows of the periodic table (see Chapter 32 "Appendix H: Periodic Table of Elements"), with only two or three exceptions (molybdenum, iodine, and possibly tin in the fifth row). Some other elements are essential for specific organisms. For example, boron is required for the growth of certain plants, bromine is widely distributed in marine organisms, and tungsten is necessary for some microorganisms.

The external environment's effects upon genes can influence disease, and some of these effects can be inherited in humans. Studies investigating how environmental factors impact the genetics of an individual's offspring are difficult to design. However, in certain parts of the world in which social systems are highly centralized, environmental information that might have influenced families can be obtained. For example, Swedish scientists recently conducted investigations examining whether nutrition affected the death rate associated with cardiovascular disease and diabetes and whether these effects were passed from parents to their children and grandchildren (Kaati et al., 2002). These researchers estimated how much access individuals had to food by examining records of annual harvests and food prices in Sweden across three generations of families, starting as far back as the 1890s. These researchers found that if a father did not have enough food available to him during a critical period in his development just before puberty, his sons were less likely to die from cardiovascular disease. Remarkably, death related to diabetes increased for children if food was plentiful during this critical period for the paternal grandfather, but it decreased when excess food was available to the father. These findings suggest that diet can cause changes to genes that are passed down though generations by the males in a family, and that these alterations can affect susceptibility to certain diseases. But what are these changes, and how are they remembered? The answers to questions such as these lie in the concept of epigenetics.

Exposing mice to long periods of light each day led them to put on fat, likely because their energy-burning brown fat wasn't in good shape.  Mice exposed to long periods of light didn't eat more or exercise less than mice that kept to a 12-hour day, but their brown fat activity dropped, researchers reported in PNAS this week (May 11).

Acid and Alkali in water... look with thermal imaging.

Although Hardy-Weinberg equilibrium is a fundamental part of introductory biology classes, students often have difficulty understanding its implications. This interrupted case study places students in the role of small teams who are conducting preliminary research into the impact of roads on the population structure of timber rattlesnakes in order to apply for a grant for further research. Research groups consisting of 3-4 students work through a series of questions allowing them to use HWE principles to discover for themselves how deviations from HWE can have implications for conservation biology. Periodic interruptions with help sheets (see Supplemental Materials) allow teachers to maintain an active role in the students' progress, while also demonstrating the collaborative nature of scientific research. Ultimately students formulate formal emails summarizing and interpreting their findings in order to "apply" for the grant. The case is designed for undergraduate students in introductory biology or in lower-level population genetics/conservation courses where connecting basic genetic principles to ecology and sustainability is key.

This case study centers on an active teaching game that simulates a cholera outbreak among five villages along a river, similar to the Haitian outbreak of 2010. By enacting the behaviors of fictional villagers, students learn how trade, travel, sanitation practices and geographic location contribute to the spread of diarrheal disease. Documenting various contamination events of village water supplies allows students to trace the progression of the disease and illustrates how adequate sanitation facilities provide protection against the bacteria Vibrio cholera. Originally designed for an undergraduate upper-division biology course focusing on the epidemiology of diseases, the simulation is also appropriate for microbiology and public health courses, as well as lower division undergraduate biology courses and high school. Biology or epidemiology components of the case study can be highlighted depending on the emphasis of the course being taught. The game can be completed within a 45- to 60-minute class period. Playing cards are available from the Supplemental Materials tab; detailed instructions are found in the teaching notes.

The backbone of New Tech High's unique learning environment is project-based learning (PBL). Instead of handing out daily assignments, teachers assign periodic projects that require critical thinking, creativity, collaboration, and communication.

In their study of the medium ground finches, evolutionary biologists Peter and Rosemary Grant were able to track the evolution of beak size twice in an amazingly short period of time due to two major droughts that occurred in the 1970s and 1980s. This activity simulates the food availability during these droughts and demonstrates how rapidly natural selection can act when the environment changes. Students use two different types of tools to represent different beak types to see which is best adapted to collect and "eat" seeds of different sizes. Students collect and analyze data and draw conclusions about traits that offer a selective advantage under different environmental conditions. They have the option of using an Excel spreadsheet to calculate different descriptive statistics and interpret graphs.

Before civilization began to impact the human life cycle approximately 10,000 years ago, human beings had high birth and death rates. Today the world is in the midst of a demographic transition - a transition to low birth and death rates - as the ability to control both disease and reproduction increases. Along the way, between these extremes, populations go through an intermediate period of continued high birth rates, combined with low death rates, resulting in a population explosion.

Biotech foods ('GMOs') are safe. Period. That may seem like a bold statement, but it comes with the weight of a huge body of research and global consensus among preeminent health organizations. To understand the safety of food biotech, it helps to look at the numbers. There are thousands of studies on biotech crops published, billions of pounds of biotech foods eaten, and there are zero illnesses (human or animal) resulting of consuming biotech foods.

This case study uses an interactive activity to illustrate density dependence in ecology classes. We developed a "hunt" using paper butterflies with warning signals on the upper side of the wings and symbols that indicate if a butterfly is noxious underneath the wings. Butterflies are distributed in four different patches with varying densities of noxious and palatable butterflies, simulating Batesian or Müllerian mimicry. Students can catch as many butterflies they want for a period of time, but if they catch more than three noxious butterflies they are out of the game. After the activity, students calculate the survival rate of each type of butterfly in each patch and discuss the implications of density and warning signals according to their results. Students then answer questions and build graphs using the data from the activity and knowledge from the class and the discussion. With this case study, students will be able to understand negative and positive density dependence, as well as predation, learning, and convergent evolution, while recalling or being introduced to Batesian and Müllerian mimicry.

Every year during the foodless winter months, bears enter their den and lapse into a state of extended dormancy and slumber (called hibernation). For the next 130+ consecutive days they do not drink, eat, defecate, or urinate. Rarely do they die from starvation, dehydration, or poisoning from waste buildup while hibernating. How do bears prepare for this period of starvation coupled with significant weight loss? Bears are not only the champions of winter rest, but are also the undisputed champions of non-stop summer eating. They are constantly on the move during late spring and all summer long into late autumn oftentimes covering great distances over diverse habitats in their incessant search for locally and seasonally available food. In this case study, students learn the basics about bear denning, hibernation energetics, the differences in size of bear home ranges, and the nutritional landscape they must navigate to prepare for the long months of winter inactivity and caloric deprivation. The case is suitable for a wide audience, including majors or non-majors in lower- or upper-level undergraduate courses in environmental science, ecology, biology, or wildlife science.

This case study centers on symbiotic relationships between insects and bacteria using Drosophila melanogaster, the common fruit fly, and the recently discovered bacterial species Sodalis praecaptivus. Until recently, the only known Sodalis species of bacteria were symbiotically associated with several different species of insects. However, free-living non-symbiont Sodalis species are being tested in several different insect species to determine if they can transition into symbiotic relationships. A pre-class assignment (see Supplemental Materials) directs students to read an open access research journal article providing a comprehensive review of S. praecaptivus and describing an experimental weevil model that parallels that of the fruit fly. A PowerPoint presentation shown in class (see Supplemental Materials) provides further background before students work in small groups to complete the case study focusing on results from D. melanogaster and S. praecaptivus model experiments.  Although developed for a genetics course, this interrupted case is appropriate for an upper-level biology course. It can be completed within a 75-minute class meeting, or adapted for shorter time periods.

The 2015 Nobel Prize in Chemistry is awarded "for mechanistic studies of DNA repair". The recipients are Paul L. Modrich, Tomas Lindahl and Aziz Sancar.

8:19 video The Nobel Prize in Physiology or Medicine 2015 goes to William Campbell & Satoshi Ōmura "for their discoveries concerning a novel therapy against infections caused by roundworm parasites" and Youyou Tu "for her discoveries concerning a novel therapy against Malaria".

Muscogee County School podcasts:  math, science, language arts, science videos

properties, orbitals, isotopes, compounds