Answer:
Directional Selection
Explanation:
The type of natural selection that favors one of the extreme phenotypes over the intermediate and another extreme phenotype is called directional selection. Here, the extreme phenotype exhibits better survival and reproductive fitness over the other phenotypic ranges.
In the given example, the frequency of the heat-tolerant allele in microbes is shown to increase under the conditions of higher temperatures of the water of the springs in which they live.
When the temperature of spring water is increased, the frequency of the heat-tolerant allele is reduced and is increased again upon an increase in water temperature.
Since the natural selection favors the extreme phenotype (microbes with heat tolerance) when the spring water exhibits higher temperatures, it is directional selection.
DNA polymerase is the enzyme that catalyzes the base pairing during DNA replication.
The DNA polymerases are enzymes that synthesize DNA molecules by assembling deoxyribonucleotides, the building blocks of DNA. These enzymes are essential to DNA replication when they read the existing DNA strand to synthesize new strand that match the existing ones by adding nucleotides to the three prime (3')-end of a DNA strand.
Ectopic focus or ectopic pacemaker happens when an excitable group of cells outside the normal sinoatrial node causes premature heartbeat. Sinoatrial node (SA node) is the pacemaker of the heart. Most people experience ectopic focus but persistent occurrence may need the client/patient to visit the doctor. If a client or patient complains of ectopic focus, it is better to consider his/her activity before visiting the clinic. Ask, for example if the client/patient had a vigorous exercise because it might be causing the irregular heartbeat, how often is he/she experiences such irregularity in his/her heartbeat (acute ectopic foci is usually non-life threatening, however, chronic type requires medical help), his/her lifestyle (he/she might be using illegal drugs, smokes and/or drinks alcohol,had too much coffee etc). Again, history taking is very vital.
