Answer:
The dry-out material contains spores of anthrax-causing bacteria
Explanation:
<em>Anthrax is a disease caused by a bacteria known as Bacillus anthracis. Susceptible animals get infected by anthrax when the spore of the bacteria gets into their bodies, become activated, multiply and produce toxins.</em>
The spore serves primarily as a propagating structure and also as an agent for transmitting infections. It can be transmitted by air, water, food or any other means. Bacterial spores usually have the capability to tolerate harsh environmental conditions and only become inactivated when conditions are favourable.
The dry granular powdery material constituent of the letters received by the U.S. senators must have been spores of <em>Bacillus anthrasis</em>
Answer:
Species separated by a physical barrier for a long time, suffer allopatric speciation, so they can not interbreed anymore.
Explanation:
Allopatric speciation consists of the geographic separation of a continuous genetic background giving place to two or more new geographically isolated populations. These separations might be due to migration, extinction of geographically intermediate populations, or geological events. In this speciation, some barriers impede genetic interchange, or genetic flow, as the two new populations that are separated can not get together and mate anymore. These barriers might be geographical or ecological.
Vicariance is the geographical separation of an original population into two or more new groups. Discontinuities in the physical environment like rivers, mountains, water, etc., are physical barriers that impede genetic flow between the separated groups.
The process of allopatric speciation involves different steps:
- The emergence of the barrier.
- Interruption in the genetic interchange
- The occurrence of new mutations and their accumulation in time in each population. Slow and gradual differentiation.
- Genetic divergence by natural selection and reproductive isolation makes it impossible for the two groups to mate even if the barrier disappears.
- Prezigotic isolation mechanisms favored by selection once occurs a secondary contact between the new species in formation.
