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.
Answer:
e. staphylococcal enterotoxin
Explanation:
Staphylococcal enterotoxin is a toxin that is produced by the bacteria Staphylococcus aureus. It is a toxin found inside the gastrointestinal tracts of the human body which is why it is called an enterotoxin and it results in food poisoning when consumed by humans.
Staphylococcal enterotoxin is proteinous in nature and it can be found on dairy products such as milk or cheeses that have been contaminated by Staphylococcus aureus.
After consumption of the contaminated milk or cheeses, the person begins to experience symptoms of nausea, diarrhea as well as vomiting.
Staphylococcal enterotoxin is a very heat stable toxin which means even though you heat up a food contaminated with this toxin, the bacteria may die by the toxins would still remain in the food.
The best way to avoid food poisoning by Staphylococcal enterotoxin is to avoid eating contaminated foods.
The answer is d. pheromones.
Osmosis is basically the spread of water across a particular absorbent membrane.
Explanation:
heat (metal or glass) and allow it to cool slowly, in order to remove internal stresses and toughen it.
OR
recombine (DNA) in the double-stranded form following separation by heat.
