Via MIT Tech Review:
… results show that it was difficult to get any human cells to survive in pig embryos and contribute to a developing fetus. Their best effort resulted in only a minimal number of human cells. It’s likely that the larger genetic distance between pigs and man is to blame.
NASA’s two Voyager spacecraft are hurtling through unexplored territory on their road trip beyond our solar system. Along the way, they are measuring the interstellar medium, the mysterious environment between stars. NASA’s Hubble Space Telescope is providing the road map – by measuring the material along the probes’ future trajectories. Even after the Voyagers run out of electrical power and are unable to send back new data, which may happen in about a decade, astronomers can use Hubble observations to characterize the environment of through which these silent ambassadors will glide.
A preliminary analysis of the Hubble observations reveals a rich, complex interstellar ecology, containing multiple clouds of hydrogen laced with other elements. Hubble data, combined with the Voyagers, have also provided new insights into how our sun travels through interstellar space.
Image: In this illustration oriented along the ecliptic plane, NASA’s Hubble Space Telescope looks along the paths of NASA’s Voyager 1 and 2 spacecraft as they journey through the solar system and into interstellar space. Hubble is gazing at two sight lines (the twin cone-shaped features) along each spacecraft’s path. The telescope’s goal is to help astronomers map interstellar structure along each spacecraft’s star-bound route. Each sight line stretches several light-years to nearby stars.
Credits: NASA, ESA, and Z. Levay (STScI)
Chlorophyll is a term used for several closely related green pigments found in cyanobacteria and the chloroplasts of algae andplants. Its name is derived from the Greek words χλωρός, chloros (“green”) and φύλλον, phyllon (“leaf”).
Chlorophyll is an extremely important bio molecule, critical in photosynthesis, which allows plants to absorb energy from light. Chlorophyll absorbs light most strongly in the blue portion of the electromagnetic spectrum, followed by the red portion. Conversely, it is a poor absorbent of green and near-green portions of the spectrum, hence the green color of chlorophyll-containing tissues.
One way of extracting Chlorophyll is by ethanol extraction (the safest). Plant material is slightly boiled in ethanol for a few moments and then filtered to reveal the green stuff extracted from your other green stuff. Chlorophyll is also fluorescent giving off a Red-ish color under UV light.
The maximum life span is a theoretical number whose exact value cannot be determined from existing knowledge about an organism; it is often given as a rough estimate based on the longest lived organism of its species known to date. A more meaningful measure is the average life span; this is a statistical concept that is derived by the analysis of mortality data for populations of each species. A related term is the expectation of life. Life expectancy represents the average number of years that a group of persons, all born at the same time, might be expected to live, and it is based on the changing death rate over many past years.
The concept of life span implies that there is an individual whose existence has a definite beginning and end. What constitutes the individual in most cases presents no problem: among organisms that reproduce sexually the individual is a certain amount of living substance capable of maintaining itself alive and endowed with hereditary features that are in some measure unique. In some organisms, however, extensive and apparently indefinite growth takes place and reproduction may occur by division of a single parent organism, as in many protists, including bacteria, algae, and protozoans. In order to consider life span in such organisms, the individual must be defined arbitrarily since the organisms are continually dividing. In a strict sense, the life spans in such instances are not comparable to those forms that are sexually produced.
There is a brief period during which it is impossible to say whether an organism is still alive, but this time is so short relative to the total length of life that it creates no great problem in determining life span.
Some organisms seem to be potentially immortal. Unless an accident puts an end to life, they appear to be fully capable of surviving indefinitely. This faculty has been attributed to certain fishes and reptiles, which appear to be capable of unlimited growth. Without examining the various causes of death in detail, a distinction can be made between death as a result of internal changes (i.e., aging) and death as a result of some purely external factor, such as an accident. It is notable that the absence of aging processes is correlated with the absence of individuality. In other words, organisms in which the individual is difficult to define, as in colonial forms, appear not to age.
The fight-or-flight response is a physiological reaction that occurs in response to a perceived harmful event, attack, or threat to survival.
It was first described by Walter Bradford Cannon. His theory states that animals react to threats with a general discharge of the sympathetic nervous system, priming the animal for fighting or fleeing.
An evolutionary psychology explanation is that early animals had to react to threatening stimuli quickly and did not have time to psychologically and physically prepare themselves.
The fight or flight response provided them with the mechanisms to rapidly respond to threats against survival.