Answer: D) Pulmonary and aortic valves.
Explanation
There are two main heartbeats from a healthy heart.
The first beat is called the S1 or the lub, and it occurs when the atrioventricular valves (comprising the mitral and tricuspid valves) close.
The second beat is called the S2 or the dub, and it occurs when the semilunar valves (comprising the aortic and pulmonary valves) close.
Listening for heart beats is an essential part of cardiac auscultation.
Answer:
The correct answer is -
1. right-handed
2. right-handed
3. positive
4. left-handed
5. negative
6. negative
Explanation:
In a circular bacterial chromosome, the structure of DNA is a right-handed double helix In a circular bacterial chromosome.
If DNA is twisted in the right-handed direction, it becomes overwound. Overwinding results in positive supercoiling takes place. If DNA is twisted in the left handd direction, it becomes underwound. Underwinding results in negative supercoiling.
f. One effect negative supercoiling in bacterial chromosomes is to promote separation of the two strands of DNA in the double helix
Answer:
Mutation, migration, genetic drift, and natural selection are all processes that can directly affect gene frequencies in a population.
Explanation:
They return nutrients from waste or dead organisms back into the ecosystem to be recycled.
The focea centralis functions to promote daytime vision, being the site of concentrated photoreceptors called cone cells.
