The post-eradication era is a period of history for which there has been no precedent whatsoever in terms of a zero base of immunity. Cessation of immunization will eventually create a population susceptible to widespread infection in the event of accidental or intentional reintroduction or re-emergence of the eradicated virus. Thus, even after immunization ceases, vaccine production must continue.
However, many currently available vaccines may not be appropriate for continued post-eradication vaccine production or reinstatement. Vaccines must be continually improved and ongoing vaccination research maintained. Other potentially useful antiviral strategies—antivirals, prophylaxis, and probiotics—must also be considered as means to strengthen the immune system and serve as adjuvant or prophylactic therapies.
In the case of polio, for example, it remains to be determined which vaccine (oral polio vaccine [OPV] or inactivated polio vaccine [IPV]), or variant thereof, should be produced in the post-eradication, post-vaccination era. A detailed plan for vaccine production will require more information on OPV-derived viral persistence and transmission, as well as continuing dialogue between public health and research communities in order to ensure that appropriate vaccination research continues.
Answer:
The three basic types of adaptations, based on how the genetic changes are expressed, are structural, physiological and behavioral adaptations. Most organisms have combinations of all these types
Explanation:
Answer:
Advanced forms of life existed on earth at least 3.55 billion years ago. In rocks of that age, fossilized imprints have been found of bacteria that look uncannily like cyanobacteria, the most highly evolved photosynthetic organisms present in the world today. Carbon deposits enriched in the lighter carbon-12 isotope over the heavier carbon-13 isotope-a sign of biological carbon assimilation-attest to an even older age. On the other hand, it is believed that our young planet, still in the throes of volcanic eruptions and battered by falling comets and asteroids, remained inhospitable to life for about half a billion years after its birth, together with the rest of the solar system, some 4.55 billion years ago. This leaves a window of perhaps 200-300 million years for the appearance of life on earth.
divine interventionThis duration was once considered too short for the emergence of something as complex as a living cell. Hence suggestions were made that germs of life may have come to earth from outer space with cometary dust or even, as proposed by Francis Crick of DNA double-helix fame, on a spaceship sent out by some distant civilization. No evidence in support of these proposals has yet been obtained. Meanwhile the reason for making them has largely disappeared. It is now generally agreed that if life arose spontaneously by natural processes-a necessary assumption if we wish to remain within the realm of science-it must have arisen fairly quickly, more in a matter of millennia or centuries, perhaps even less, than in millions of years. Even if life came from elsewhere, we would still have to account for its first development. Thus we might as well assume that life started on earth.
How this momentous event happened is still highly conjectural, though no longer purely speculative. The clues come from the earth, from outer space, from laboratory experiments, and, especially, from life itself. The history of life on earth is written in the cells and molecules of existing organisms. Thanks to the advances of cell biology, biochemistry and molecular biology, scientists are becoming increasingly adept at reading the text.
An important rule in this exercise is to reconstruct the earliest events in life's history without assuming they proceeded with the benefit of foresight. Every step must be accounted for in terms of antecedent and concomitant events. Each must stand on its own and cannot be viewed as a preparation for things to come. Any hint of teleology must be avoided.
Hydrosphere
Explanation:
- The dolphin swims in the hydrosphere.
- The hydropshere is the region occupied by water on the earth surface.
- They are the oceans, lakes, rivers, glaciers e.t.c
- The hydrosphere makes up 70% the total surface area on earth.
- Ocean occupies a whooping 95% of all.
- The hydrosphere is able to support aquatic life and this is why the dolphin with its streamlined body swims in this sphere.
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Atmosphere brainly.com/question/1851697
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